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 including main grooves 20 and 21 inclined with respect to a tire width direction so as to be positioned gradually towards a rear side in a main rotating direction of the tire, from a center part in a tire width direction toward both sides in the tire width direction. The tread 10 has a plurality of shoulder blocks 50 and 60, arranged at both sides in the tire width direction along a tire circumferential direction, in which sipes 51 and 61 are formed. In side walls of the sipes 51 and 61 are formed inclined surfaces 52 and 62 inclined at a predetermined angle with respect to ground contact surfaces of the shoulder blocks 50 and 60.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, pneumatic tires 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 are known (see, for example, Patent Document 1). The tread of the tire of Patent Document 1 has a plurality of main grooves formed inclined relative to the tire width direction. The tire of Patent Document 1 is a so-called directional tire in which the main rotation direction of the tire is specified. Furthermore, the pneumatic tire of Patent Document 1 exhibits an edge effect on snowy and icy road surfaces due to the edge of the blocks and sipes formed in the blocks. [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 attempts 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 that has improved wet and dry performance, and in particular, excellent braking performance on both wet and dry road surfaces. [Means for solving the problem]

[0006] A pneumatic tire according to the present invention has a tread including main grooves that are inclined relative to the tire width direction so as to be positioned gradually rearward in the main rotational direction of the tire from the tire widthwise center toward both sides in the tire width direction. The tread has shoulder blocks arranged on both sides in the tire width direction along the tire circumferential direction and each having a first sipe formed therein, and the sidewalls of the first sipes are formed with first slopes that are inclined at a predetermined angle relative to the contact surfaces of the shoulder blocks.

[0007] This configuration improves braking performance on both wet and dry road surfaces, achieving both good wet and dry performance. The slopes formed on the sipe sidewalls of the shoulder blocks effectively distribute the ground pressure of the blocks while ensuring the rigidity of the blocks. Distributing the ground pressure over a wide area of ​​the block's contact surface increases friction with the road surface and improves grip compared to when the ground pressure is concentrated in a limited area. With this configuration, for example, even if the shoulder blocks are relatively small due to increased drainage by increasing the width of the main groove, high braking performance can be achieved due to the ground pressure distribution effect of the slopes. [Effects of the Invention]

[0008] The pneumatic tire according to the present invention has excellent braking performance on both wet and dry road surfaces, and has good wet and dry performance. The pneumatic tire according to the present invention is a directional tire with a specified main rotation direction, and is suitable as an all-season tire. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a perspective view of a pneumatic tire as an example of an embodiment. [Figure 2] 1 is a plan view of a pneumatic tire that is an example of an embodiment, showing a portion of a tread. [Figure 3] FIG. 2 is a plan view schematically showing a part of a tread. [Figure 4]FIG. 2 is an enlarged perspective view showing a left portion in the width direction of the tread. [Figure 5] FIG. 2 is a perspective view showing a block group 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 the left side portion in the width direction of the tread. DETAILED DESCRIPTION OF THE INVENTION

[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. Furthermore, the present invention includes selective combinations of the 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 refers to a road surface wet with rainwater or a road surface wet from melting snow and ice. A snowy road surface refers to a road surface covered with snow. A dry road surface refers to a dry road surface free of snow and ice. Hereinafter, for convenience of explanation, wet road surfaces and snowy road surfaces may be collectively referred to as "snow and ice road surfaces." Furthermore, although no particular reference will be made to driving performance on frozen road surfaces (ice performance) below, 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, illustrating the internal structure of the tire. As shown in FIG. 1, the pneumatic tire 1 includes a tread 10, which is the portion that comes into contact with the road surface. The tread 10 has a tread pattern including a plurality of blocks, which are 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 relative to the tire width direction so as to be positioned gradually rearward in the main rotational direction of the tire 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 rotational direction. The main grooves 20, 21 are formed between blocks adjacent in the tire circumferential direction, and define 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 equipped with the pneumatic tire 1 moves forward. In addition, for the sake of convenience, the terms "left and right" are used in this specification to describe the pneumatic tire 1 and its components. The "right side" of the pneumatic tire 1 refers to the right side when the pneumatic tire 1 is mounted on a vehicle and viewed from the front of the vehicle, and the "left side" refers to the left side when the pneumatic tire 1 is mounted on a vehicle and viewed from the front of the vehicle. The drawings show arrows indicating the main tire rotation direction and 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 portion 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. 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 "tread 10 width direction" are the same direction, and both terms will be used appropriately hereinafter.

[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 protrude radially outward from the tire. The tread 10 has a plurality of center blocks 30, 40, a plurality of shoulder blocks 50, 60, and a plurality of intermediate blocks 70, 80. The center block 30, the shoulder block 50, and the intermediate block 70 are arranged on the left side of the tread 10 in the width direction, and the center block 40, the shoulder block 60, and the intermediate block 80 are arranged on the right side of the tread 10 in the width direction.

[0016] In this embodiment, blocks of the same type, designated by the same reference numerals, 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 intermediate blocks 70, 80.

[0017] Center blocks 30, 40 are arranged in the widthwise center of the tread 10, sandwiching the tire equator CL on either side. The tire equator CL refers to 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). Portions 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 a single 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 a single block group 101. The three blocks that make up block group 100 are aligned in the direction in which the main groove 20 extends, and the three blocks that make up block group 101 are aligned in the direction in which the main groove 21 extends.

[0019] As will be described in more detail below, the tread 10 has a tread pattern in which the contact area (A3) of the slope 52 mediate blocks 70, 80 is large and the contact area (A3) is greater than or equal to the contact area (A2) of the shoulder blocks 50, 60. The pneumatic tire 1 exhibits high grip on snowy and icy surfaces using multiple blocks, and by increasing the contact area (A3), it achieves excellent handling stability on both snowy and icy surfaces and dry surfaces. Each block also has sipes formed to enhance the edge effect on snowy and icy surfaces. A pneumatic tire 1 with such a tread pattern is suitable, for example, for all-season tires.

[0020] The pneumatic tire 1 includes shoulder portions 11, sidewall portions 12, and beads 13, which are formed in an annular shape along the tire circumferential direction, similar to the tread 10. The shoulder portions 11, sidewall portions 12, and beads 13 are portions that form the side surfaces 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 portions 11. In addition, annular side ribs 14 formed on the side surfaces of the pneumatic tire 1 are the boundary positions between the shoulder portions 11 and the sidewall portions 12.

[0021] In this specification, the ground contact edge E refers 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 inflated to 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 specified by the tire standard, and is a "standard rim" for JATMA, a "design rim" for TRA, and a "measuring rim" for ETRTO. "Regular internal pressure" is the "maximum air pressure" for JATMA, the maximum value listed in the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" table for TRA, and "INFLATION PRESSURE" for ETRTO. "Regular load" is the "maximum load capacity" for JATMA, the maximum value listed in the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" table for TRA, and "LOAD CAPACITY" for ETRTO.

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

[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 coated 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 withstands loads, impacts, air pressure, and the like. The belt 16 is a reinforcing band stretched in the circumferential direction of the tire, and tightly fastens the carcass 15 to increase the rigidity of the tread 10. An inner liner 17, which is a rubber layer for maintaining 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 portion of the tread 10. In Fig. 2 and other figures, the block contact surfaces are indicated by dot hatching. The block contact surface refers to the area of ​​the top surface of each block facing outward in the tire radial direction that comes into contact with the road surface.

[0026] As shown in Figure 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 pattern along the tire circumferential direction. The block groups 100, 101 defined by the main grooves 20, 21 are also 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 portion 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 portion 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 contact edge E side. The inclination angle of the main grooves 20, 21 with respect to the tire width direction on the tire equator CL side is, for example, 30° to 60° or 40° to 50°.

[0028] In the pneumatic tire 1, when the tire rotates so that the tire equator CL side of the block groups 100, 101 contacts 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, resulting in good wet and snow performance. 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 contacts the ground first is the main rotation direction. The sidewall portion 12 is provided with markings such as arrows or letters that indicate the main rotation direction of the tire.

[0029] The tread pattern of the tread 10 is a pattern in which 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 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, past the left ground contact edge E, and across 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 pattern 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 its inclination with respect to the tire width direction becomes gentler.

[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 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 grips and compacts 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, past the right ground contact edge E, and across 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 conforms to the tire width direction from the tire equator CL side toward the ground contact edge E, with a gentler slope relative to the tire width direction. 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 rows of blocks aligned in the tire circumferential direction. The first circumferential grooves 25 dividing the rows of center blocks 30, 40 are bent in opposite directions at the intersections with the main grooves 20, 21, i.e., at 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 linearly 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 linear fashion, good drainage performance is achieved. The second circumferential groove 26 separates the row of shoulder blocks 50 from the row of intermediate blocks 70, and the second circumferential groove 27 separates the row of shoulder blocks 60 from the row of intermediate 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 areas where there are no raised portions 90 (described below).

[0035] Protuberances 90 that are lower in height than the blocks are provided within the second circumferential grooves 26, 27. Like the blocks, the protuberances 90 protrude radially outward in the tire direction and are formed to connect the lower portions of the two blocks between the shoulder block 50 and the intermediate block 70, and between the shoulder block 60 and the intermediate block 80. As will be described in more detail later, the protuberances 90 increase the rigidity of the blocks, contributing to improved dry performance, for example.

[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. Furthermore, 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 can be said to be formed in multiples lined up in the tire circumferential direction. Furthermore, 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 the 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 handling stability on snowy and icy roads. The width of the sipes is, for example, 30% or less, or 20% or less, of the width of the third circumferential grooves 28, 29 in the portions where there are no slopes, as described below.

[0038] The sipes 31, 41 of the center blocks 30, 40 and the sipes 71, 81 of the intermediate 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 from the end located on the inner side of each block in the tire width direction to a length exceeding the ground contact edge E. In addition, a slope is formed on the sidewall of each sipe, inclined at a predetermined angle θ (see Figure 6 described below) with respect to the block ground contact surface. The slope is formed at a predetermined depth from the block ground contact surface along the length of the sipe. The predetermined depth is, for example, 30% or less of the sipe depth.

[0039] The slopes 52 formed along the sipes 51 of the shoulder blocks 50 function to effectively distribute the ground pressure of the blocks, increasing friction with the road surface and improving grip while maintaining the rigidity of the shoulder blocks 50. The slopes 52 also widen the sipes 51 to improve drainage and enlarge the snow pockets that trap snow. The slopes 52 improve braking performance on snowy and icy roads and dry roads, contributing to improved wet, snow, and dry performance. The slopes 62 formed along the sipes 61 of the shoulder blocks 60 also perform the same function as the slopes 52.

[0040] The slopes 32 formed along the sipes 31 of the center block 30 contribute to the distribution of ground pressure, just like the slopes 52, but they also improve the block's ability to grip snow, enhancing traction on snowy roads. The slopes 32 also improve drainage. The slopes 42 formed along the sipes 41 of the center block 40 and the slopes 72 and 82 formed along the sipes 71 and 81 of the intermediate blocks 70 and 80, for example, perform the same function as the slopes 32.

[0041] The configuration of each block will be described in detail below with reference to Figures 2 to 4, taking three blocks that make up the block group 100 as an example. Figure 3 is a plan view that schematically shows the tread 10, and Figure 4 is an enlarged perspective view of the left side portion of the tread 10 in the width direction. Figures 5 and 6 will also be referenced below as appropriate. Figure 5 is a view that selectively shows the block group 100, and Figure 6 is a cross-sectional view taken along line AA in Figure 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 plan view that is elongated in the extension direction of the main grooves 20, 21, 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 beyond the tire equator CL to the right, and a portion of the right center block 40 extending beyond the tire equator CL to the left.

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

[0044] In this embodiment, the sidewalls 30b, 30c of the center block 30 and the sidewalls 40b, 40c of the center block 40 intersect with the tire equator CL. On the other hand, the sidewalls 30a, 40a of each block are not positioned on the tire equator CL and do not intersect with the tire equator CL. The sidewalls of the center blocks 30, 40 are not entirely perpendicular to the block ground contact surface; the lower portions of the sidewalls, particularly those near the groove bottoms, are curved to extend outward from the block (the same applies to the sidewalls of the other blocks). In the schematic diagram of FIG. 3, the entire sidewall of each block is shown 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. 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 sidewall 30c of the center block 30 is formed with three surfaces (first surface 301c, second surface 302c, and third surface 303c) that are oriented in different directions, and there is an intersection point P5 where these three surfaces intersect. The first surface 301c faces the sidewall 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 sidewall 30a to the center portion of the center block 30 in the lateral direction. The second surface 302c is formed from a corner P2 to the center portion of the center block 30 in the lateral direction, and is connected to the first surface 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, causing the first circumferential groove 25 to gradually widen 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 relative 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 extension direction of the main groove 20. The sipe 31 is formed in the center portion in the short direction of the center block 30, extending over the entire longitudinal length of the contact patch so as to bisect the contact patch. The sipe 31 is also formed on the sidewall 30d from the block contact patch to the groove bottom of the third circumferential groove 28 or deeper than the groove bottom, with the sipe end 31b opening into the third circumferential groove 28. On the other hand, no sipe 31 is formed on the sidewall 30c intersecting the tire equator CL, and the sipe end 31a does not open into the first circumferential groove 25. In this case, good braking performance on dry roads is ensured, while the edge effect and drainage effect of the sipe 31 can improve braking performance on snowy and icy roads.

[0050] The contact area (A1) of the center block 30 is the smallest of the three blocks constituting the block group 100. In this specification, the contact area of ​​a block refers to the area of ​​the portion that comes into contact with the road surface under the above conditions, and includes the area of ​​the portion where sipes are formed. When the total contact area of ​​the three blocks constituting the block group 100 is taken as 100%, the contact area (A1) of the center block 30 is, for example, 20% to 35%, and more preferably 25% to 33%. If the contact area (A1) ratio is within this range, it becomes easier to improve handling performance during steady driving, such as straight driving at speeds 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) relative to the contact surface of the center block 30. As described above, the slopes 32 ensure the rigidity of the center block 30 while improving traction performance on snowy roads and drainage. 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. Furthermore, during sudden braking or sudden acceleration, for example, the slopes 32 come into contact with the road surface, preventing the blocks from tipping over.

[0052] In this specification, the inclination angle θ of the slope 32 relative to the ground contact surface of the center block 30 refers to the angle between the block ground contact surface (top surface of the block) and an imaginary plane α extending from the slope 32, as shown in Figure 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 applies similarly to the slopes of the other blocks.

[0053] The slope 32 may be formed on both the first sidewall of the sipe 31, which is located on the front side in the tire's main rotational direction, and the second sidewall, which is located on the rear side in the tire's main rotational direction. However, it is preferable that the slope 32 be formed larger on the second sidewall than on the first sidewall. In this embodiment, the slope 32 is formed only on the second sidewall of the sipe 31, which is located on the rear side in the tire's main rotational direction. By forming the slope 32 on only one sidewall, it is possible to more effectively achieve both the effect of the slope 32 and the suppression of a decrease in the rigidity of the block. Furthermore, when the slope 32 is formed on the second sidewall, the slope 32 comes into contact with the road surface during sudden braking or sudden acceleration, making it easier to suppress the collapse of the block, compared to when the slope 32 is formed on the first sidewall.

[0054] 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 trailing side of the side walls of the sipe 31. Alternatively, if the portion of the center block 30 partitioned by the sipe 31 located on the front side in the main rotational direction of the tire 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, then the slope 32 can be said to be formed on the leading end of the second portion.

[0055] The slope 32 includes two regions (first region 32a and second region 32b) that have different shapes in a plan view (see FIG. 4). The first region 32a is a generally rectangular surface in a plan view that is generally parallel to the longitudinal direction of the sipe 31, and is formed with a length that is 40% to 60% of the overall length of the slope 32. In contrast, the second region 32b is a generally triangular surface in a plan view that is inclined more toward the sipe end 31b than the first region 32a, and its area decreases toward the sipe end 31a. By providing the second region 32b, the step formed at the end of the slope 32 can be made gentler, 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 contact surface to the middle of the sipe 31 in the depth direction. The slope 32 is preferably formed only near the block ground contact surface. Hereinafter, the opening of the sipe at the block ground contact surface (top surface of the block) may be referred to as the "upper opening." The formation of the slope 32 widens the sipe 31 at and near the upper opening, but the width of the sipe 31 does not increase in areas away from the upper opening. In other words, even in areas where the slope 32 of the sipe 31 is formed, areas away from the upper opening are formed with the same width as areas where the slope 32 is not present. Note that although FIG. 6 illustrates a 2D sipe, the sipe may be a 3D sipe.

[0057] The depth D2 of the slope 32 in the first region 32a is, for example, 10% to 30% of the depth D1 of the sipe 31, more preferably 10% to 25%, or 10% to 20%. Here, the depth of the sipe and slope means the length from the block 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 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 or 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 slopes 32 are formed within a predetermined length range from the sipe ends 31b located on the intermediate block 70 side. The predetermined length is preferably a length that does not reach the sipe ends 31a on the tire equator CL side, and the slopes 32 are not formed near the sipe ends 31a. As will be described in detail later, the slopes 32 are formed with a length (length along the sipes 31) that is, for example, 30% to 50% of the longitudinal length of the contact patch of the center block 30. By controlling the length of the slopes 32 within an appropriate range and accurately controlling the relationship with the lengths of the slopes of the other blocks, the wet performance, snow performance, and dry performance of the pneumatic tire 1 can be more effectively improved.

[0059] As described above, the slopes 32 widen the sipes 31 at and near the upper openings of the sipes 31. The width W2 of the slopes 32 in the first region 32a is, for example, 1.3 to 3.5 times, more preferably 1.5 to 3 times, or 2 to 3 times, the width W1 of the sipes 31 in the portion where the slopes 32 are not present (see FIG. 6). Here, the width of the slopes refers to 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 slopes 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 sipes 31 is, for example, 5% to 35% of the width of the third circumferential groove 28.

[0060] Similarly, a single sipe 41 is formed in the center block 40 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, dividing the block ground contact surface into two equal parts. 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 sidewalls of the sipes 41 are formed with slopes 42 that are inclined at a predetermined angle relative to the contact surface of the center blocks 40 over a predetermined length range from the sipe ends 41b. The inclination angle of the slopes 42 is, for example, 25° to 35°, which is the same as the inclination angle θ of the slopes 32. The slopes 42 are formed only on the second sidewalls of the sipes 41 that are located on the rear side in the main rotational direction of the tire. In this embodiment, the shape of the center blocks 40 is the same as the shape of the center blocks 30 when they are inverted with respect to the tire equatorial plane, and if the inverted center blocks 30 are slid circumferentially in the tire, they will match the center blocks 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 tire width direction outer side and tire radial direction inner side, and the block top surfaces are significantly curved. Similar to the center blocks 30, 40, the shoulder blocks 50, 60 have a generally rectangular shape in plan view that is elongated in the extension direction of the main grooves 20, 21, and the longitudinal direction of each block is inclined with respect to the tire width direction. However, 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 larger than the center block 30 and the mediate block 70, and its length along the tire width direction is the longest among these three blocks. On the other hand, the contact area (A2) of the shoulder block 50 is less than or equal to the contact area (A3) of the mediate block 70. The contact area (A2) is, for example, 30% - 45%, more preferably 33% - 38%, when the total contact area of the three blocks constituting the block group 100 is taken as 100%. If the ratio of the contact area (A2) is within this range, it becomes easier to improve the handling performance during steady driving.

[0064] The contact area (A2) of the shoulder block 50 is larger than the contact area (A1) of the center block 30, and it is preferable that the contact area of each block satisfies the condition of A1 < A2 ≤ A3. Although it will be described in detail later, when the sum of the contact areas (A1, A3) is 1.8 to 1.9 times the 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 contact surface 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 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 contact pressure by the slope 52.

[0065] Similarly, for the shoulder block 60, it is the largest among the three blocks constituting the block group 101, but the contact area of the shoulder block 60 is less than or equal to the 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. If the inverted shoulder block 50 is slid in the tire circumferential direction, it will coincide with the shoulder block 60.

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

[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 bends. 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 second circumferential groove 26. Details of the raised portion 90 will be described later.

[0068] A single sipe 51 is formed in each 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 direction, extending 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 that exceeds the ground-contact edge E. The sipe 51 is formed on 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. If the depth of the sipe 51 satisfies these 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 in the tire width direction to sipe ends 71b of the sipes 71 of the intermediate blocks 70, with the second circumferential groove 26 sandwiched between them. 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 edge E, and the sipe ends 51b on the outer side in the tire width direction are located between the ground contact edge E and the side ribs 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 sidewalls of the sipes 51 are formed with slopes 52 that are inclined at a predetermined angle relative to the contact surface of the shoulder blocks 50. As described above, the slopes 52 ensure the rigidity of the shoulder blocks 50 while dispersing the contact pressure of the blocks and improving friction with the road surface. Therefore, the slopes 52 significantly contribute to improved braking performance. The slope angle of the slopes 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 slopes 32. In this case, the function of the slopes 52 is more effectively exhibited.

[0071] The slope 52 may be formed on both the first side wall of the sipe 51, which is located on the front side in the tire's main rotational direction, and the second side wall, which is located on the rear side in the tire's main rotational direction. However, it is preferable that the slope 52 be 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, which is located on the rear side in the tire's main rotational direction. By forming the slope 52 only on the second side wall, it is possible to more effectively achieve both the effect of the slope 52 and the suppression of a decrease in the rigidity of the block. Furthermore, 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 slopes 52 are formed from the contact surface of the shoulder block 50 to a predetermined depth of the sipe 51. The slopes 52 are preferably formed at the upper openings of the sipes 51 and in the vicinity thereof. The depth of the slopes 52, located inward in the tire width direction from the 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 slopes 52 is within this range, the block rigidity can be ensured while the ground pressure can be effectively dispersed. An example of the depth of the slopes 52 is 0.8 mm to 1.2 mm.

[0073] The slopes 52 may be formed to a depth greater than the slopes 32 of the center block 30, but in this embodiment, they are formed shallower than the slopes 32. The depth of the slopes 52 is, for example, 60% to 90% or 65% to 85% of the depth of the slopes 32. If the slopes 52 are formed long, the shoulder blocks 50 will have a higher effect of dispersing ground pressure, but the rigidity of the blocks will likely decrease. Therefore, in this embodiment, a configuration in which the slopes 52 are formed long and slightly shallow will be adopted, thereby achieving both sufficient block rigidity and a higher level of ground pressure dispersion.

[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 edge E. By forming the slope 52 over the entire length of the ground contact surface of the shoulder block 50, it is possible to enhance the effect of improving braking performance by dispersing ground pressure. In addition, by positioning the end of the slope 52 outward from the ground contact edge E, it is possible to suppress the concentration of stress at the end of the slope 52, improving the durability of the block. Note that, because the end of the slope 52 is not present 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 intermediate block 70 in the tire width direction, with the second circumferential groove 26 in between. 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, effectively removing the water film between the tire and the road surface. In addition, the snow pockets that trap snow can be efficiently enlarged, improving snow column shear force.

[0076] The slopes 52 are formed so that their length does not reach the sipe ends 51b. By positioning the ends of the slopes 52 between the ground contact edge E and the sipe ends 51b, a decrease in the rigidity of the shoulder blocks 50 can be suppressed, improving the durability of the blocks. The ends of the slopes 52 are preferably positioned near the ground contact edge E in the shoulder regions 11. The rigidity of the shoulder blocks 50 can also be adjusted by the position of the sipe ends 51b in the shoulder regions 11. For example, if the rigidity of the shoulder blocks 50 is too high relative to the other blocks, the sipes 51 can be extended to adjust the rigidity balance of the blocks.

[0077] The slopes 52 are formed to 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 slope length to the block length is greatest in the shoulder block 50 among the three blocks that make up the block group 100. Furthermore, the length of the slopes 52 along the sipes 51 is longer than the lengths of the slopes of the other two blocks along the sipes. The slopes 52 of the shoulder block 50 are preferably formed long on the block contact surface because they greatly contribute 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 is not present. If the width of the slope 52 is within this range, for example, it is possible to effectively distribute ground pressure while ensuring block rigidity. The slope 52 may be formed to be wider than 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 that the slope 52 be formed long on the block contact surface. Therefore, the depth and width of the slope 52 are made slightly smaller, thereby achieving both ensuring block rigidity and a more effective distribution of ground pressure.

[0079] Similarly, each shoulder block 60 has a single sipe 61 formed along the extension direction of the main groove 21. The sipe 61 is formed with a length that extends from a sipe end 61a that opens into the second circumferential groove 27, past the ground contact edge 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 edge E and the side rib 14. The sipe end 61a is disposed opposite in the tire width direction to a sipe end 81b of a sipe 81 in the intermediate block 80, with the second circumferential groove 27 sandwiched between them.

[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 edge 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 opposite 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 plan view that is elongated in the extension direction of the main grooves 20, 21, 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. Meanwhile, 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. Furthermore, 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 handling performance during steady driving.

[0083] Similarly, the contact area of ​​the mediate block 80 is the largest among the contact areas of the three blocks that make up 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 when the inverted mediate block 70 is slid in the tire circumferential direction, it matches the mediate block 70.

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

[0085] The sidewall 70c is formed in a generally 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 generally 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 main tire rotation direction. Therefore, the sidewalls 70c, 70d are not parallel to each other, and the sidewall 70b is longer than the sidewall 70a.

[0086] Each mediate block 70 has one sipe 71 formed along the extension direction of the main groove 20. The sipe 71 is formed in the center of the mediate block 70 in the short direction over the entire length of the block in the longitudinal direction so as to divide the block 70 in half. 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 to the same depth over the entire longitudinal length of the intermediate block 70. In the sidewall 70c, the sipes 71 are formed to 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 sidewall 70d, the sipes 71 are formed from the block contact surface to the upper surfaces of the raised portions 90 formed in the second circumferential groove 26, or are formed deeper than the upper surfaces of the raised portions 90 and shallower than the main groove 20. When the depth of the sipes 71 satisfies these conditions, it becomes easy to enhance the edge effect while ensuring the rigidity of the block.

[0088] The sidewall of the sipe 71 is formed with a slope 72 inclined at a predetermined angle relative 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 distributes ground contact pressure, improves drainage, and enlarges snow pockets while ensuring the rigidity of the block. 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 of the sipe 71, which is located on the front side in the tire's main rotational direction, and the second side wall, which is located on the rear side in the tire's main rotational direction, 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, which is located on the rear side in the tire's main rotational direction. In all three blocks constituting the block group 100, the slopes along the sipe are formed only on the second side wall. In this case, the effect of the slopes can be more effectively achieved while suppressing a decrease in the rigidity of the blocks. Furthermore, the slopes come into contact with the road surface during sudden braking or sudden acceleration, making it easier to suppress the collapse of the blocks.

[0090] Like the slope 32, the slope 72 includes two regions (a first region 72a and a second region 72b) that have different shapes in a plan view (see FIG. 4). The first region 72a is a generally rectangular surface in a plan view that is generally parallel to the longitudinal direction of the sipe 71, and is formed over a length that is more than 50%, preferably 70% to 90%, of the entire length of the slope 72. In contrast, the second region 72b is a generally triangular surface in a plan view that is inclined more toward the sipe end 71b than the first region 72a, and its area decreases toward the sipe end 71a. By providing the second region 72b, the step formed at the end of the slope 72 can be made gentler, thereby suppressing stress concentration at the end of the slope 72.

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

[0092] The slopes 72 are formed within a predetermined length range from the sipe ends 71b located on the shoulder block 50 side. The predetermined length is preferably a length that does not reach the sipe ends 71a on the third circumferential groove 28 side, and the slopes 72 are not formed near the sipe ends 71a. The slopes 72 are formed to a length (length along the sipes 71) that is, for example, 20% to 40% of the longitudinal length of the block top faces. As will be described in detail later, the length of the slopes along the sipes and the ratio of the length of the slopes to the length of the blocks are smallest in the intermediate block 70 among the three blocks that make up the block group 100.

[0093] The width of the slope 72 is, for example, 1.3 to 3.5 times, 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. Note that 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, each mediate block 80 has a single sipe 81 formed along the extension direction of the main groove 21. The sipe 81 is formed over the entire longitudinal length of the mediate block 80 so as to bisect the block. 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 the sipe end 81b. The inclination angle of the slope 82 with respect to the ground contact surface of the intermediate block 80 is, for example, 25° to 35°, which is the same as the inclination angle of the slope 72. In addition, the slope 82 is formed at a position opposite 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 explained below with reference to FIGS.

[0097] As described above, the block group 100 has three blocks arranged in a row along the extension direction of the main groove 20, and has an overall gently curved shape in a plan view. Similar to the main groove 20, the block group 100 is inclined with respect to the tire width direction so that it is gradually positioned rearward in the main rotation direction of the tire from the center in the tire width direction toward the outer sides in the tire width direction. That is, among the three blocks that make up one block group 100, the center block 30 is positioned forward of the shoulder block 50 in the main rotation direction of the tire.

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

[0099] The block group 100 has a third circumferential groove 28 that separates the center block 30 and the intermediate block 70, but its depth 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 intermediate block 70 are connected by a portion that protrudes from the groove bottom of the main groove 20. In other words, in the block group 100, the lower parts of adjacent blocks are connected via a low protrusion. In this case, the rigidity of the block group 100 is improved, and 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, substantially 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 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 sidewalls 30b of the center blocks 30 face the sidewalls 40c of the center blocks 40 across the first circumferential groove 25, and the sidewalls 30c face the sidewalls 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 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 that protrudes from the bottom of the main groove 20.

[0102] The block groups 100, 101 are formed such that the lower portions of adjacent blocks are connected via raised portions and extend across the left and right side ribs 14. Furthermore, the center block 30 is connected to two center blocks 40 that are adjacent in the tire circumferential direction, so the lower portions 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 overall rigidity.

[0103] The contact area of ​​each block and the length of the slope formed on the sipe sidewall of each block will be further explained below with reference to Fig. 7. Fig. 7 is a plan view showing a portion 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 grounding 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 grounding 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 running can be more highly compatible. When the total of the grounding areas (A1, A3) is less than 1.8 times the grounding area (A2), the handling performance during steady running tends to deteriorate compared with the case where the above condition is satisfied. On the other hand, when the total of the grounding areas (A1, A3) exceeds 1.9 times the grounding area (A2), the braking performance tends to deteriorate compared with the case where the above condition is satisfied.

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

[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 70 , 72 , 72 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 / L 70 ), 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 72 of the ratio (L <000001 l> / L 70When [[ID=]] is 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 a wet road surface, a snow road surface, and a dry road surface, and the wet performance, snow performance, and dry performance are effectively improved. On the other hand, regarding the width and depth of the groove, the groove 52 of the shoulder block 50 is the smallest compared to the groove 32 of the center block 30 and the groove 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 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 groove of the groove, it is shown in FIG. 7. However, since the groove is inclined with respect to the tire width direction, it is longer than the illustrated length.

[0112] The ratio of the length of the groove 32 to the length of the groove 31 of the center block 30 is substantially the same as the above ratio (L1). Also, the ratio of the length of the groove 72 to the length of the groove 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 groove 52 to the length of the groove 51 of the shoulder block 50 is 32 substantially the same as the above ratio (L2). 72 The ratio of the length of the groove 72 to the length of the groove 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 groove 52 to the length of the groove 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 conditions of L3 < L1 < L2 are satisfied and the ratios (L1 - L3) are within the said range, the wet performance, snow performance, and dry performance can be improved more effectively.

[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 In other words, for the pneumatic tire 1, L 72 <L 32 <L 52 <L 52 32 The length L of the slope 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 block ground contact surface). 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. 32 The length L of the slope 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 block ground contact surface). The sip 51 and the slope 52 are formed over the entire length of the ground contact surface of the shoulder block 50 as described above. <000041As described above, according to the pneumatic tire 1 having the above configuration, the slopes 52 and 62 formed on the sidewalls of the sipes of the shoulder blocks 50 and 60 can effectively disperse the contact pressure of the blocks while ensuring the rigidity of the blocks. The dispersion effect of this contact pressure has been demonstrated by the present inventor. When the contact pressure can be dispersed over a wide range of the block contact surface, the frictional force against the road surface increases and the braking performance improves. The pneumatic tire 1, for example, has wide main grooves 20 and 21 and good drainage and snow removal performance, but accordingly, the contact area (A2) of the shoulder blocks 50 and 60 is small. However, due to this dispersion effect of the contact pressure, high braking performance can be obtained on wet and dry road surfaces.

[0116] If slopes 32 and 42 are formed on the sidewalls of the center blocks 30 and 40, the width of the sipes can be widened to improve drainage and the snow pocket for biting snow can be enlarged while ensuring the rigidity of the blocks. The center blocks 30 and 40, for example, can firmly grip the snow at the portions where the slopes 32 and 42 are formed, improving the traction on the snow-covered road surface. In particular, if slopes are formed on each block including the intermediate blocks 70 and 80 and the lengths of the respective slopes are accurately controlled to satisfy the above conditions, the wet performance, snow performance, and dry performance can be more effectively improved.

[0117] Also, by satisfying the condition that the 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, the braking performance and the handling performance during steady driving can be more highly compatible. 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.

[0118] In addition, in the pneumatic tire 1, the slopes 52 of the shoulder blocks 50 and the slopes 72 of the intermediate blocks 70 are formed adjacent to the second circumferential groove 26 and are disposed opposite each other in the tire width direction with the second circumferential groove 26 sandwiched between them. Similarly, the slopes 62 of the shoulder blocks 60 and the slopes 82 of the intermediate blocks 80 are formed adjacent to the second circumferential groove 27 and are disposed opposite each other in the tire width direction with the second circumferential groove 27 sandwiched between them. In this case, water can be efficiently drained from each sipe into the circumferential groove, effectively removing the water film between the tread 10 and the road surface, greatly improving drainage performance. Snow pockets can also be efficiently expanded.

[0119] As described above, the pneumatic tire 1 is suitable for use as an all-season tire. While all-season tires generally emphasize wet and dry performance, the pneumatic tire 1 excels in snow performance in addition to wet and dry performance. In this embodiment, the contact area of ​​each block and the arrangement and dimensions of the slopes of each block are precisely controlled in a well-balanced manner, thereby achieving performance suitable for an all-season tire across the entire tread 10.

[0120] 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 of the block group 101 when 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 that is symmetrical with respect to the tire equatorial plane.

[0121] In the above-described embodiment, slopes are formed on the sipe sidewalls of all blocks, but slopes do not have to be formed on at least one of the center blocks and the intermediate blocks. However, to improve traction on snowy roads, it is preferable to form slopes on the sipe sidewalls of the center blocks. For example, a pattern may be adopted in which slopes are formed on the center blocks and shoulder blocks but not on the intermediate blocks, but it is preferable that the rigidity of the blocks, ground pressure, drainage and snow removal performance, etc. are well-balanced and controlled throughout the tread 10.

[0122] Note that, 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-described embodiment, the contact area (A3) of the mediate blocks 70, 80 is larger than the contact area (A2) of the shoulder blocks 50, 60, but the contact area (A2) may be larger than the contact area (A3).

[0123] In the above-described embodiment, each block has one sipe, but two or more sipes may be formed in each block. In the above-described embodiment, by forming slopes on the sipe sidewalls, drainage is improved without increasing the number of sipes, thereby improving wet performance. However, 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. [Explanation of symbols]

[0124] 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 sidewall, 301c first surface, 302c second surface, 303c third surface, 31, 41, 51, 61, 71, 81 sipe, 31a, 31b, 41a, 41b, 51a, 51b, 61a, 61b, 71a, 71b, 81a, 81b Sipe edge, 32, 42, 52, 62, 72, 82 slope, 32a, 72a first area, 32b, 72b second area, 50, 60 shoulder block, 70, 80 mediate block, 90 raised portion, 100, 101 block group, CL tire equator, E contact edge, P1, P2, P4 corner, P5 intersection

Claims

1. A pneumatic tire having a tread including main grooves inclined with respect to the tire width direction so as to be positioned gradually rearward in the main rotation direction of the tire from a center portion in the tire width direction toward both sides in the tire width direction, The tread has a plurality of shoulder blocks arranged on both sides in the tire width direction along the tire circumferential direction, and each shoulder block has a sipe formed therein, The sidewall of the sipe is formed with a slope inclined at a predetermined angle with respect to the ground contact surface of the shoulder block, The side walls of the sipe have a first side wall located on the front side in the main rotational direction of the tire and a second side wall located on the rear side in the main rotational direction of the tire, The pneumatic tire, wherein the inclined surface is formed only on the second side wall.

2. The pneumatic tire according to claim 1 , wherein the sipes and the slopes are formed from ends of the shoulder blocks located on inner sides in the tire width direction to positions beyond the tread edge.

3. 3. The pneumatic tire according to claim 1, wherein the inclined surface is inclined at an angle of 25° to 35° with respect to the contact surface of the shoulder block.

4. The tread is a plurality of intermediate blocks arranged along the tire circumferential direction between the tire width direction center and the shoulder blocks, the intermediate blocks having second sipes formed therein; a circumferential groove formed linearly along the tire circumferential direction between the shoulder block and the intermediate block; The pneumatic tire according to any one of claims 1 to 3, having

5. A pneumatic tire having a tread including main grooves inclined with respect to the tire width direction so as to be positioned gradually rearward in the main rotation direction of the tire from a center portion in the tire width direction toward both sides in the tire width direction, The tread is a plurality of shoulder blocks arranged on both sides in the tire width direction along the tire circumferential direction, the shoulder blocks having first sipes formed therein; a plurality of intermediate blocks arranged along the tire circumferential direction between the tire width direction center and the shoulder blocks, the intermediate blocks having second sipes formed therein; a circumferential groove formed linearly along the tire circumferential direction between the shoulder block and the intermediate block; and A first inclined surface inclined at a predetermined angle with respect to the ground contact surface of the shoulder block is formed on a side wall of the first sipe, A second inclined surface inclined at a predetermined angle with respect to the ground contact surface of the mediate block is formed on a side wall of the second sipe, The pneumatic tire, wherein the first inclined surface and the second inclined surface are formed at positions opposing each other in the tire width direction with the circumferential groove interposed therebetween.

6. 6. The pneumatic tire according to claim 1, wherein a ratio of a length of the main groove along the tire circumferential direction to a length of the contact surface of the shoulder block along the tire circumferential direction is 3:7 to 4:6.

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