Pneumatic tire and tire molding mold

Abstract

To improve road surface followability on a snow-covered road surface while improving steering stability and braking performance on a dry road surface.SOLUTION: A pneumatic tire 1 includes a tread 10 and has a specified rotational direction. The tread 10 includes: a plurality of main grooves 20 extending from an equator side toward a ground contact end side; blocks 30 provided along the main grooves 20 and arranged alternately across the main grooves in a tire circumferential direction; and a slit 80 connecting the adjacent main grooves 20 to each other in a tire rotation direction and having a bent shape, where the slit 80 includes first portions 82 and 83 extending along a first direction and a second portion 84 extending along a second direction inclined with respect to the first direction in a plan view of the tread, the first portions 82 and 83 are provided at both ends of the slit 80 in a length direction, and a sipe 85 is provided on a bottom surface of the slit 80.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a pneumatic tire and a tire molding die.

Background Art

[0002] Conventionally, directional tires in which the rotation direction of the tire is specified are known. For example, Patent Document 1 discloses a pneumatic tire in which chamfers are provided on the side surfaces of the sipes provided in the tread blocks from the viewpoint of improving handling stability and braking performance on a dry road surface.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In winter tires or all-season tires, in addition to improving handling stability and braking performance on a dry road surface, it is also required to improve road surface following performance on a snow-covered road surface.

Means for Solving the Problems

[0005] The pneumatic tire according to the present invention includes a tread and is a pneumatic tire with a specified rotation direction. The tread has a plurality of main grooves extending from the equator side toward the ground contact end side, blocks provided along the main grooves and arranged alternately with the main grooves in the tire circumferential direction, and slits connecting adjacent main grooves in the tire rotation direction and having a bent shape. The slit includes a first portion extending along a first direction and a second portion extending along a second direction inclined with respect to the first direction in a plan view of the tread. The first portion is provided at both ends in the length direction of the slit, and sipes are provided on the bottom surface of the slit.

Advantages of the Invention

[0006] According to the pneumatic tire of the present invention, it is possible to improve the handling stability and braking performance on a dry road surface while improving the road surface following performance on a snow road surface.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Modes for Carrying Out the Invention

[0008] Hereinafter, with reference to the drawings, an example of an embodiment of the pneumatic tire according to the present invention will be described in detail. The embodiments described below are merely examples, and the present invention is not limited to the following embodiments. In addition, forms formed by selectively combining the respective constituent elements of the embodiments described below are included in the present invention.

[0009] FIG. 1 is a perspective view showing a part of a pneumatic tire 1 according to an example of an embodiment, and also shows the internal structure of the tire. As shown in FIG. 1, the pneumatic tire 1 includes a tread 10 that is a portion in contact with the road surface, a pair of sidewalls 11 disposed on both sides of the tread 10, and a pair of beads 13 disposed on the inner side in the tire radial direction of the sidewalls 11. Further, the pneumatic tire 1 includes a carcass 14 spanned between the pair of beads 13 and an inner liner 15 disposed on the inner side in the tire radial direction of the carcass 14.

[0010] The pneumatic tire 1 is a directional tire with a specified rotational direction. In this specification, the "rotational direction" of the tire means the rotational direction when the vehicle on which the tire is mounted moves forward. Also, in this specification, the terms "left and right" are used for convenience of explanation, and the left and right here mean the left and right in the traveling direction of the vehicle with the tire mounted on the vehicle. The pneumatic tire 1 preferably has a display for indicating the mounting direction with respect to the vehicle. On the side surface of the pneumatic tire 1, for example, at least one of characters and arrows indicating the rotational direction is provided. FIG. 1 shows an arrow indicating the rotational direction of the tire. Also, in some drawings including FIG. 1, arrows indicating the directions of "front, rear, left, and right" are shown in the direction in which the vehicle moves forward.

[0011] Also, in this specification, the terms "indentation side" and "kicking-out side" are used for the blocks and the like constituting the tread 10. The "indentation side" of the block or the like means the side that first contacts the road surface (front in the rotational direction) when the pneumatic tire 1 rotates in the direction in which the vehicle moves forward, and the "kicking-out side" means the side that contacts the road surface later (rear in the rotational direction).

[0012] The tread 10 has main grooves 20 and 21. The main grooves 20 and 21 extend from the equator CL (see Fig. 2) side toward the ground contact end side, and have a larger inclination angle with respect to the tire axis direction on the equator CL side than on the ground contact end side. More specifically, the main groove 20 (corresponding to the first main groove) extends from the equator CL side toward the ground contact end E1 (corresponding to the first ground contact end) side, and the main groove 21 (corresponding to the second main groove) extends from the equator CL side toward the ground contact end E2 (corresponding to the second ground contact end) side.

[0013] Here, the equator CL means a line along the tire circumferential direction passing through the exact center in the tire axis direction of the tread 10 (a position equidistant from the ground contact ends E1 and E2). Also, in this specification, the ground contact ends E1 and E2 are defined as the both ends in the tire axis direction of the region that contacts the flat road surface when a predetermined load is applied in a state where the unused pneumatic tire 1 is mounted on a standard rim and filled with air to reach the standard internal pressure. In the case of a passenger car tire, the predetermined load is a load corresponding to 88% of the standard load.

[0014] Here, the "standard rim" is a rim determined by the tire specification, which is the "Standard Rim" in JATMA, and the "Measuring Rim" in TRA and ETRTO. The "standard internal pressure" is the "Maximum Air Pressure" in JATMA, the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in TRA, and the "INFLATION PRESSURE" in ETRTO. The standard internal pressure is usually 250 kPa for a passenger car tire, but 290 kPa for a tire marked as Extra Load or Reinforced. The "standard load" is the "Maximum Load Capacity" in JATMA, the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in TRA, and the "LOAD CAPACITY" in ETRTO. In the case of a racing kart tire, the standard load is 392 N.

[0015] The tread 10 has a first block group 30 and a second block group 40 provided along the main groove 20 and including a plurality of blocks, and a first block group 50 and a second block group 60 provided along the main groove 21 and including a plurality of blocks. The first block group 30 and the second block group 40 are alternately arranged with the main groove 20 therebetween in the tire circumferential direction, and the first block group 50 and the second block group 60 are alternately arranged with the main groove 21 therebetween in the tire circumferential direction. Note that a block is a convex portion that is divided by a main groove or a slit and protrudes toward the outer side in the tire radial direction. That is, a region divided by a sipe is not included in the block. In this specification, a groove having a width of 1.5 mm or more is defined as a slit, and a groove having a width of less than 1.5 mm is defined as a sipe, respectively.

[0016] As will be described in detail later, the first block group 30 has three blocks, and the second block group 40 has two blocks. Specifically, the first block group 30 has a first center block 31 located on the equator CL side, a first shoulder block 33 located on the ground contact end E1 side, and a first mediate block 32 disposed between the first center block 31 and the first shoulder block 33. The second block group 40 has a second center block 41 located on the equator CL side and a second shoulder block 42 located on the ground contact end E1 side.

[0017] The first block group 50 also has three blocks similar to the first block group 30, and the second block group 60 also has two blocks similar to the second block group 40. Specifically, the first block group 50 has a first center block 51 located on the equator CL side, a first shoulder block 53 located on the ground contact end E2 side, and a first mediate block 52 disposed between the first center block 51 and the first shoulder block 53. The second block group 60 has a second center block 61 located on the equator CL side and a second shoulder block 62 located on the ground contact end E2 side. In this embodiment, the first shoulder block 53 and the second shoulder block 62 have the same shape.

[0018] The sidewall 11 is disposed on both sides of the tread 10 and is provided annularly along the tire circumferential direction. The sidewall 11 is the portion that protrudes most outward in the tire axial direction of the pneumatic tire 1 and is gently curved so as to be convex toward the outside in the tire axial direction. The sidewall 11 has a function of preventing damage to the carcass 14. The sidewall 11 is the portion that bends most when the pneumatic tire 1 exerts a cushioning effect, and usually, a flexible rubber having fatigue resistance is adopted.

[0019] The pneumatic tire 1 may be provided with side ribs 12 between the grounding ends E1, E2 of the tread 10 and the portion that protrudes most outward in the tire axial direction of the sidewall 11. The side ribs 12 protrude toward the outside in the tire axial direction and are provided annularly along the tire circumferential direction. The portions from the grounding ends E1, E2 of the pneumatic tire 1 or the vicinity thereof to the left and right side ribs 12 are also called the shoulder or the battless region.

[0020] Also, generally, characters, numbers, symbols, etc. called serials are provided on the sidewall 11. The serial includes information such as a size code, a manufacturing time (manufacturing year and week), a manufacturing location (manufacturing factory code), etc.

[0021] The bead 13 is disposed inside the sidewall 11 in the tire radial direction and is the portion fixed to the rim of the wheel. The bead 13 has a bead core 16 and a bead filler 17. The bead core 16 is composed of a steel bead wire and is an annular member extending over the entire circumference in the tire circumferential direction and is embedded in the bead 13. The bead filler 17 has a tip tapered shape extending outward in the tire radial direction and is an annular hard rubber member extending over the entire circumference in the tire circumferential direction.

[0022] The carcass 14 is spanned between a pair of beads 13 and is locked by being folded around the bead core 16. The carcass 14 includes a carcass cord made of organic fibers and topping rubber. The carcass cord is arranged substantially at a right angle (for example, 80° or more and 90° or less) with respect to the tire circumferential direction. Examples of the organic fibers used for the carcass cord include polyester fibers, rayon fibers, aramid fibers, and nylon fibers.

[0023] The inner liner 15 covers the inner surface of the tire between a pair of beads 13. The inner liner 15 is made of air-permeability-resistant rubber and has a function of maintaining the air pressure of the pneumatic tire 1.

[0024] The pneumatic tire 1 further includes a belt 18 disposed on the outer side in the tire radial direction of the carcass 14 and a cap ply 19 covering the entire outer side in the tire radial direction of the belt 18. The belt 18 is disposed on the outer peripheral side of the top of the carcass 14 and is provided so as to overlap the outer peripheral surface of the carcass 14. The belt 18 is composed of a belt ply in which cords arranged in a direction inclined with respect to the tire circumferential direction are rubber-coated. The material of the cords of the belt 18 is not particularly limited, and examples thereof include organic fibers such as polyester, rayon, nylon, and aramid, or metals such as steel. Further, the pneumatic tire 1 may further include an edge ply (not shown) disposed on the outer side in the tire radial direction of the cap ply 19 and covering both axial ends in the tire axial direction of the belt 18. The cap ply 19 and the edge ply have a function of reinforcing the belt 18.

[0025] Hereinafter, with reference to FIGS. 2 to 6, the tread pattern of the pneumatic tire 1 will be described in detail. FIG. 2 is a plan view of the pneumatic tire 1 (tread 10).

[0026] As shown in FIG. 2, the tread 10 has main grooves 20 and 21 that extend from the equator CL side toward the ground contact end side and have a larger inclination angle with respect to the tire axis direction on the equator CL side than on the ground contact end side. The main groove 20 extends from the equator CL side toward the ground contact end E1 side, and the main groove 21 extends from the equator CL side toward the ground contact end E2 side. The main grooves 20 and 21 are arranged at arbitrary intervals in the tire circumferential direction.

[0027] The main groove 20 includes two types of main grooves 20A and 20B with different lengths. The main groove 20A is longer than the main groove 20B and is provided with a length that reaches the right region of the tread 10 beyond the equator CL. The main groove 20B is provided with a length that does not exceed the equator CL in the left region of the tread 10. Similarly, the main groove 21 also includes two types of main grooves 21A and 21B with different lengths.

[0028] The first block group 30 is arranged on the indentation side of the main groove 20A, and the second block group 40 is arranged on the indentation side of the main groove 20B. That is, they are repeatedly arranged in the tire circumferential direction in the order of the main groove 20A, the first block group 30, the main groove 20B, and the second block group 40. Also, as described above, the main groove 20A is longer than the main groove 20B and is provided with a length that reaches the right region of the tread 10 beyond the equator CL. Therefore, the first block group 30 is provided with a length that reaches the right region of the tread 10 beyond the equator CL. Also, the second block group 40 is provided with a length that does not exceed the equator CL, similar to the main groove 20B.

[0029] Similarly, for the right region of the tire, the first block group 50 is arranged on the indentation side of the main groove 21A, and the second block group 60 is arranged on the indentation side of the main groove 21B. That is, they are repeatedly arranged in the tire circumferential direction in the order of the main groove 21A, the first block group 50, the main groove 21B, and the second block group 60. And the first block group 50 is provided with a length that reaches the left region of the tread 10 beyond the equator CL. Also, the second block group 60 is provided with a length that does not exceed the equator CL. Thereby, the first block group 30 and the first block group 50 are arranged in a staggered pattern along the equator CL.

[0030] The tread pattern of this embodiment is a pattern in which, in a plan view of the tread 10, the first block groups 30, 50 and the second block groups 40, 60 are arranged symmetrically with respect to the equator CL with a predetermined pitch shifted in the tire circumferential direction. That is, the shape of the first block group 30 is the same as the shape when the first block group 50 is inverted with respect to the equator CL, and the shape of the second block group 40 is the same as the shape when the second block group 60 is inverted with respect to the equator CL (the same applies to the main grooves 20, 21). The tread pattern of this embodiment has good left - right balance and is effective in improving handling stability.

[0031] In a plan view of the tread 10, the main grooves 20, the first block group 30, and the second block group 40 have a curved shape that bulges toward the kicking - out side. Similarly, the main groove 21, the first block group 50, and the second block group 60 also have a curved shape that bulges toward the kicking - out side. That is, the main grooves 20, 21, the first block groups 30, 50, and the second block groups 40, 60 are all inclined with respect to the tire axial direction so as to be gradually located on the kicking - out side from the equator CL side toward the grounding ends E1, E2 side.

[0032] As described above, the main grooves 20, 21 have a larger inclination angle with respect to the tire axial direction on the equator CL side than on the grounding ends E1, E2 side. In other words, the main grooves 20, 21 gradually become along the tire axial direction from the equator CL side toward the grounding ends E1, E2, and the inclination with respect to the tire axial direction becomes gentle. The inclination angle of the main grooves 20, 21 with respect to the tire axial direction is, for example, 30° or more and 60° or less, or 40° or more and 50° or less on the equator CL side.

[0033] The main groove 20 is connected to the main groove 21 in the vicinity of the equator CL. The main groove 20 extends from the intersection with the main groove 21 toward the ground end E1 side and is provided across the left side rib 12 beyond the ground end E1. Further, the main groove 21 extends from the intersection with the main groove 20 in the vicinity of the equator CL toward the ground end E2 side and is provided across the right side rib 12 beyond the ground end E2.

[0034] The widths of the main grooves 20 and 21 may be constant over the entire length, but in this embodiment, they gradually increase from the equator CL side toward the ground ends E1 and E2 sides. In this case, in addition to improving drainage, the snow column shear force for grasping and tamping down snow is improved, and the braking performance on the snow-covered road surface is improved. The widths of the main grooves 20 and 21 are, for example, 2.0 mm or more and 10.0 mm or less on the equator CL side, and 3.0 mm or more and 15.0 mm or less on the ground ends E1 and E2 sides. Further, the main grooves 20 and 21 are configured to have the same depth. The depth of the main grooves 20 and 21 is, for example, 5.0 mm or more and 15.0 mm or less. In this specification, the width of a groove (including a slit and a sipe) means the width on the profile surface along the ground contact surface of the tread 10 unless otherwise specified. Also, the depth of a groove means the length along the tire diameter direction from the profile surface along the ground contact surface of the tread 10 to the groove bottom unless otherwise specified.

[0035] Bridges 22 and 23 are provided in the grooves at the tips on the equator CL side of the main grooves 20 and 21. The bridge 22 includes a bridge 22A provided at the tip of the main groove 20A and a bridge 22B provided at the tip of the main groove 20B. Further, the bridge 23 includes a bridge 23A provided at the tip of the main groove 21A and a bridge 23B provided at the tip of the main groove 21B.

[0036] The bridges 22 and 23 are convex portions protruding radially outward in the tire diameter direction from the bottoms of the main grooves 20 and 21, and connect adjacent center blocks. Specifically, the bridge 22A connects the first center block 31 and the first center block 51, and the bridge 22B connects the first center block 31 and the second center block 41. Also, the bridge 23A connects the second center block 41 and the first center block 51, and the bridge 23B connects the first center block 51 and the second center block 61.

[0037] By providing the bridges 22 and 23, each center block is connected in the tire circumferential direction, so that the block rigidity becomes high in the vicinity of the equator CL, and the traction performance during braking can be improved. Also, since the bridges 22 and 23 are provided only at the tips of the respective main grooves, good drainage performance can also be ensured. That is, by providing the bridges 22 and 23, it is possible to improve the traction performance during braking while ensuring good drainage performance. The length of the bridges 22 and 23 along the main grooves 20 and 21 may be shorter than, for example, the length along the slits 70 and 71 of the bridges 72 and 73 described later. The length of the bridges 22 and 23 along the main grooves 20 and 21 is, for example, 0.5 mm or more and 5.0 mm or less.

[0038] The bridges 22 and 23 preferably have a height of 30% or more and 70% or less, or 40% or more and 60% or less of the depth of the main grooves 20 and 21. Also, the bridges 22 and 23 may have an inclined region where the height increases as it approaches the tip on the equator CL side of the main grooves 20 and 21. By providing the inclined region in the bridges 22 and 23, the water in the main grooves 20 and 21 easily flows toward the grounding ends E1 and E2 sides, and the drainage performance of the pneumatic tire 1 is improved.

[0039] The tread 10 has a slit 70 that connects the main grooves 20 to each other in the tire rotation direction, and a slit 71 that connects the main grooves 21 to each other in the tire rotation direction. The slits 70 and 71 are grooves that are narrower than the maximum width of the main grooves 20 and 21. The width of the slit 70 is, for example, 2.0 mm or more and 6.0 mm or less.

[0040] The slit 70 is inclined with respect to the tire circumferential direction so as to gradually move away from the ground contact end E1 from the depressed side toward the kicking side. Similarly, the slit 71 is also inclined with respect to the tire circumferential direction so as to gradually move away from the ground contact end E2 from the depressed side toward the kicking side. In the present embodiment, the slits 70 and 71 are provided at the same depth as the main grooves 20 and 21. Note that the depth of the slits 70 and 71 may be smaller than the depth of the main grooves 20 and 21.

[0041] The slit 70 includes a slit 70A that partitions the first intermediate block 32 and the first shoulder block 33, and a slit 70B that partitions the second center block 41 and the second shoulder block 42. As described above, the first block group 30 and the second block group 40 are alternately arranged in the tire circumferential direction. Therefore, the slit 70A and the slit 70B are alternately arranged in the tire circumferential direction. Note that the slit 70A and the slit 70B have the same shape.

[0042] Similar to the slit 70, the slit 71 includes a slit 71A that partitions the first intermediate block 52 and the first shoulder block 53, and a slit 70B that partitions the second center block 61 and the second shoulder block 62. Also, the slit 71A and the slit 71B are alternately arranged in the tire circumferential direction. Note that the slit 71 has the same shape as the shape when the slit 70 is inverted with respect to the equator CL. That is, the slit 71A and the slit 71B have the same shape.

[0043] At the groove bottom of the depressed side ends of the slits 70 and 71, bridges 72 and 73 are provided in the same manner as the main grooves 20 and 21. The bridge 72 includes a bridge 72A provided in the slit 70A and a bridge 72B provided in the slit 70B. Further, the bridge 73 includes a bridge 73A provided in the slit 71A and a bridge 73B provided in the slit 71B.

[0044] Similar to the bridges 22 and 23, the bridges 72 and 73 are convex portions protruding radially outward in the tire diameter direction from the groove bottoms of the slits 70 and 71, and connect adjacent center blocks. Specifically, the bridge 72A connects the first intermediate block 32 and the first shoulder block 33, and the bridge 72B connects the second center block 41 and the second shoulder block 42. Further, the bridge 73A connects the first intermediate block 52 and the first shoulder block 53, and the bridge 72B connects the second center block 61 and the second shoulder block 62.

[0045] By providing the bridges 72 and 73, in-plane shrinkage around the slits 70 and 71 is suppressed. As a result, water can flow more easily through the slits 70 and 71, and the drainage performance of the pneumatic tire 1 is improved. Further, by providing the bridges 72 and 73 at the depressed side ends of the slits 70 and 71, the traction performance during braking is improved.

[0046] The length of the bridges 72, 73 along the slits 70, 71 is preferably 60% or less, more preferably 50% or less of the length of the slits 70, 71. By setting the length of the bridges 72, 73 to 60% or less of the length of the slits 70, 71, the volume of the slits 70, 71 can be ensured, and the braking performance on the snow-covered road surface can be ensured. In other words, when the length of the bridges 72, 73 exceeds 60% of the length of the slits 70, 71, the influence of the volume reduction of the slits 70, 71 becomes significant, and the braking performance on the snow-covered road surface may decrease. Further, the length of the bridges 72, 73 along the slits 70, 71 is preferably 10% or more, more preferably 20% or more of the length of the slits 70, 71. By setting the length of the bridges 72, 73 to 10% or more of the length of the slits 70, 71, the improvement of the drainage performance and the improvement of the traction performance during braking are remarkable. Therefore, the length of the bridges 72, 73 along the slits 70, 71 is preferably 10% or more and 60% or less of the length of the slits 70, 71, more preferably 20% or more and 50% or less.

[0047] The bridges 72, 73 preferably have a height of 30% or more and 70% or less, or 40% or more and 60% or less of the depth of the slits 70, 71. Further, in the present embodiment, the bridges 72, 73 have an inclined region 74 (see FIG. 3) in which the height increases as it goes toward the stepped-in side of the slits 70, 71. That is, the slits 70, 71 have a region in which the depth becomes smaller as it goes toward the stepped-in side of the slits 70, 71. By providing the inclined region 74 in the bridges 72, 73, the water in the slits 70, 71 easily flows toward the main grooves 20, 21 side, and the drainage performance of the pneumatic tire 1 is improved.

[0048] In addition to the slits 70, 71, the tread 10 has a slit 80 that connects the main grooves 20 to each other in the tire rotation direction, and a slit 81 that connects the main grooves 21 to each other in the tire rotation direction. The slit 80 partitions the first center block 31 and the first mediate block 32, and the slit 81 partitions the first center block 51 and the first mediate block 52.

[0049] The slit 80 is provided on a substantially straight extension of the main groove 21A. The slit 80 is disposed opposite to the main groove 21A with the main groove 20A therebetween, and is disposed opposite to a slit 90 (to be described later) with the main groove 20B therebetween. By disposing the slit 80 opposite to the main groove 21A with the main groove 20A therebetween, a large amount of snow can be accumulated inside the slit 80 during snow driving. As a result, the snow column shear force for gripping and compacting the snow is improved, and the traction performance on the snow-covered road surface can be improved. Further, the slit 81 is provided on a substantially straight extension of the main groove 20A. The slit 81 is disposed opposite to the main groove 20A with the main groove 21A therebetween, and is disposed opposite to the slit 90 (to be described later) with the main groove 21B therebetween.

[0050] The slits 80 and 81 have a bent shape. Although details will be described later, the slits 80 and 81 include a first portion 82 and 83 (see FIG. 4) extending along a first direction, and a second portion 84 (see FIG. 4) extending along a second direction inclined with respect to the first direction in a plan view of the tread 10. In the present embodiment, in the plan view of the tread 10, the angle formed by the first direction and the second direction is approximately 90°. That is, the second portion 84 is substantially orthogonal to the first portions 82 and 83. By providing the slits 80 and 81 having a bent shape, a large amount of snow can be accumulated in the vicinity of the bent portion inside the slits 80 and 81 during snow driving. As a result, the snow column shear force for gripping and compacting the snow is improved, and the traction performance on the snow-covered road surface can be improved. The slits 80 and 81 are formed, for example, shallower than the main grooves 20 and 21 and the slits 70 and 71.

[0051] On the bottom surfaces of the slits 80 and 81, sipes 85 (see FIG. 3) extending along the first direction are provided. The sipes 85 are provided, for example, over the extending direction of the slits 80 and 81. That is, the sipes 85 connect the main grooves 20 and 21 to each other in the tire rotation direction. Although details will be described later, by providing the sipes 85 on the bottom surfaces of the slits 80 and 81 having a bent shape, it is possible to improve the handling stability and braking performance on a dry road surface while improving the road surface following performance on a snow road surface.

[0052] Hereinafter, with further reference to FIG. 3, the tread pattern of the pneumatic tire 1 will be described in detail. FIG. 3 is a diagram showing an enlarged part of the tread pattern. As described above, the shape of the first block group 50 is the same as the shape when the first block group 30 is inverted with respect to the equator CL, and the shape of the second block group 60 is the same as the shape when the second block group 40 is inverted with respect to the equator CL. Therefore, hereinafter, the first block group 30 and the second block group 40 will be described, and the description of the first block group 50 and the second block group 60 will be omitted.

[0053] As shown in FIGS. 2 and 3, the tread 10 is partitioned by the main grooves 20 as described above, and has a first block group 30 and a second block group 40 including a plurality of blocks. The first block group 30 and the second block group 40 are alternately arranged in the tire circumferential direction. More specifically, the first block group 30 is arranged on the indentation side of the main groove 20A, and the second block group 40 is arranged on the indentation side of the main groove 20B.

[0054] The first block group 30 includes a first center block 31 located on the equator CL side, a first shoulder block 33 located on the ground end E1 side, and a first intermediate block 32 disposed between the first center block 31 and the first shoulder block 33. A slit 80 that connects two adjacent main grooves 20 in the tire rotation direction is provided between the first center block 31 and the first intermediate block 32, and a slit 70A that connects two adjacent main grooves 20 in the tire rotation direction is provided between the first intermediate block 32 and the first shoulder block 33. That is, the first center block 31 and the first intermediate block 32 are partitioned by the slit 80, and the first intermediate block 32 and the first shoulder block 33 are partitioned by the slit 70A.

[0055] In addition, the second block group 40 includes a second center block 41 located on the equator CL side and a second shoulder block 42 located on the ground end E1 side. A slit 70B that connects two adjacent main grooves 20 in the tire rotation direction is provided between the second center block 41 and the second shoulder block 42. That is, the second center block 41 and the second shoulder block 42 are partitioned by the slit 70B.

[0056] As described above, the first block group 30 includes three blocks, namely, a first center block 31, a first intermediate block 32, and a first shoulder block 33. The second block group 40 includes two blocks, namely, a second center block 41 and a second shoulder block 42. Here, the noise during running is greatly affected by the peak value of the frequency of the impact sound when each block collides with the road surface. When there is no change in the number of blocks over the tire circumferential direction, that is, when the number of blocks included in the first block group 30 is the same as the number of blocks included in the second block group 40, the impact sound generated when the tread 10 collides with the road surface is likely to occur at a constant period, and the peak value of the frequency of the impact sound is generated. As a result, the noise during running increases. On the other hand, as in the tread pattern of the present embodiment, while arranging the main grooves 20, 21 so that the inclination with respect to the tire axial direction is larger on the equator CL side than on the ground contact end E1, E2 sides, by changing the number of blocks included in each block group, the period of the impact sound when the tread 10 collides with the road surface can be shifted. As a result, the frequency of the impact sound is dispersed, and the noise during running can be reduced.

[0057] In a plan view of the tread 10, the area (S31) of the first center block 31 and the area (S32) of the first intermediate block 32 are each smaller than the area (S41) of the second center block 41, and the sum (S31 + S32) of the area (S31) of the first center block 31 and the area (S32) of the first intermediate block 32 is preferably larger than the area (S41) of the second center block 41. That is, the slit 80 partitioning the first center block 31 and the first intermediate block 32 is preferably arranged so as to satisfy S31 < S41, S32 < S41, and S31 + S32 > S41. When S31 < S41, S32 < S41, and S31 + S32 > S41 are satisfied, the sizes of the respective blocks become closer, and the pneumatic tire 1 excellent in wear resistance can be provided. In other words, when S31 < S41, S32 < S41, and S31 + S32 > S41 are not satisfied, the difference in the sizes of the respective blocks becomes too large, and uneven wear is likely to occur in the block having a small size.

[0058] In a plan view of the tread 10, the area (S31) of the first center block 31 is preferably 75% or more and 125% or less, more preferably 80% or more and 120% or less of the area (S32) of the first intermediate block 32. When the area (S31) of the first center block 31 is 75% or more and 125% or less of the area (S32) of the first intermediate block 32, the pneumatic tire 1 more excellent in wear resistance can be provided.

[0059] As shown in FIG. 3, in a plan view of the tread 10, the outer end 32A in the tire axial direction of the first intermediate block 32 and the outer end 41A in the tire axial direction of the second center block 41 are provided on the same straight line along the tire circumferential direction. Further, the first center block 31 is arranged across the equator CL, and the second center block 41 is arranged without crossing the equator CL.

[0060] The tire axial lengths of the first center block 31 and the first intermediate block 32 are, for example, 10% or more and 30% or less of the ground contact width D (see FIG. 2), respectively. Also, the tire axial length of the second center block 41 is, for example, 15% or more and 40% or less of the ground contact width D.

[0061] In the second center block 41, a slit 90 is provided that extends from the main groove 20B toward the inside of the second center block 41 and terminates inside the second center block 41. The slit 90 is provided on a substantially extension of the main groove 21A and is disposed opposite to the slit 80 with the main groove 20B therebetween. The slit 90 provides a snow column shearing force for grasping and compacting snow during snow driving. That is, the slit 90 contributes to the improvement of the traction performance of the pneumatic tire 1 on a snow-covered road surface.

[0062] By terminating the slit 90 inside the second center block 41, the volume of the second center block 41 can be secured and a decrease in block rigidity can be suppressed. As a result, braking performance on a snow-covered road surface can be improved while ensuring traction performance during braking. Also, the slit 90 is preferably provided on the kicking-out side of the second center block 41 from the viewpoint of ensuring the wear resistance of the pneumatic tire 1.

[0063] The slit 90 is inclined with respect to the tire circumferential direction and the tire axial direction. In this case, the edge effect acts in both the tire circumferential direction and the axial direction, and the effect of improving braking performance on a snow-covered road surface becomes more remarkable. The slit 90 is, for example, inclined more with respect to the tire axial direction than the tire circumferential direction. An example of the inclination angle of the slit 90 with respect to the tire axial direction is 60° or more and less than 90°.

[0064] The width of the slit 90 is smaller than, for example, the width of the slit 70 at the end on the main groove 20B side. The width of the slit 90 is, for example, 1.5 mm or more and 3.0 mm or less at the end on the main groove 20B side. Further, the slit 90 has a narrow-width region 91 in which the width decreases as it goes inside the second center block 41. That is, the slit 90 has a tapered shape in which the width gradually becomes narrower toward the tip. By having the narrow-width region 91 in the slit 90, the volume of the second center block 41 can be more ensured, and the decrease in block rigidity can be more suppressed. In the narrow-width region 91, the width of the slit 90 may decrease linearly or non-linearly.

[0065] The depth of the slit 90 may be constant over the extending direction of the slit 90, but in the present embodiment, the depth of the tip side of the slit 90 decreases as it goes inside the second center block 41. The depth of the slit 90 is substantially the same as, for example, the depth of the portion where the bridge 22 of the main groove 20 is provided at the end on the main groove 20B side. The depth of the slit 90 is, for example, 30% or more and 90% or less of the depth of the main groove 20 at the end on the main groove 20B side, preferably 40% or more and 80% or less.

[0066] As shown in FIG. 3, a plurality of cycles (first cycles) 92 that cross the first center block 31 are provided in the first center block 31, and a plurality of cycles (second cycles) 93 that cross the first intermediate block 32 are provided in the first intermediate block 32.

[0067] In a plan view of the tread 10, the sipe 92 is provided such that a straight line connecting both longitudinal ends of the sipe 92 extends along the tire axial direction, and the sipe 93 is provided such that a straight line connecting both longitudinal ends of the sipe 93 is inclined with respect to the tire axial direction. That is, the sipe 92 extends along the axial direction of the tire, and the sipe 93 extends along a direction inclined with respect to the tire axial direction. By changing the extending directions of the sipe 92 and the sipe 93, the handling stability on a dry road surface can be improved. The inclination angle of the sipe 93 with respect to the tire axial direction is, for example, 20° or more and 70° or less.

[0068] The sipes 92 and 93 are preferably wavy sipres. In order to improve the braking performance on a snow road surface, it is necessary to increase the number of sipres and the number of edges. However, when the number of sipres is increased, for example, the block rigidity is excessively reduced, and the contact area is likely to decrease due to the collapse of the blocks. When the collapse of the blocks occurs excessively, the handling stability on a dry road surface decreases. By forming the sipes 92 and 93 as wavy sipres as in the present embodiment, the number of edges can be increased without increasing the number of sipres. As a result, the braking performance on a snow road surface can be improved while ensuring the handling stability on a dry road surface.

[0069] The waves of the sipres 92 and 93 are portions that are convex in a direction orthogonal to the longitudinal direction of the sipres 92 and 93, and are configured to be substantially triangular in plan view. The sipres 92 and 93 have straight portions formed as straight lines and wavy portions in which a plurality of waves are repeated. The straight portions are provided at both longitudinal ends of the sipres 92 and 93, and the wavy portions are provided between the straight portions. The wavy portions are configured to be bent in a zigzag shape so as to be convex on both sides of a center line connecting both longitudinal ends of the sipres 92 and 93.

[0070] The amplitudes of cycles 92 and 93 are constant for each wave, for example, and the waveform portions of cycles 92 and 93 are regularly configured at a constant period. An example of the amplitude of cycles 92 and 93 is 0.5 mm or more and 3.0 mm or less. In this specification, the amplitude of a waveform cycle means the distance from the center line connecting both ends in the length direction of the cycle to the apex of the largest wave.

[0071] The depth of cycles 92 and 93 is, for example, 10% or more and 100% or less of the depth of the main groove 20. Also, for cycles 92 and 93, the depth of the waveform portion may be greater than the depth of the straight portion. That is, for cycles 92 and 93, the depth on the central side in the length direction may be greater than the depth on both end sides in the length direction. Also, the depth of cycles 92 and 93 may differ for each cycle.

[0072] Also, a plurality of cycles 94 crossing the second center block 41 are provided in the second center block 41. Cycles 94 are waveform cycles and extend along a direction inclined with respect to the tire axis direction. The inclination angle of cycles 94 with respect to the tire axis direction is, for example, substantially the same as the inclination angle of cycles 93 with respect to the tire axis direction.

[0073] Hereinafter, the slit 80 will be described in detail with reference to FIGS. 4 to 6. FIG. 4 is a diagram showing an enlarged view of the vicinity of the slit 80. Also, in FIG. 4, for convenience of explanation, a dotted line is shown at the boundary between the first portions 82 and 83 and the second portion 84, which will be described later.

[0074] As shown in FIG. 4, the slit 80 connects the main grooves 20A and 20B to each other in the tire rotation direction and has a bent shape. The slit 80 includes a first portion 82, 83 extending along a first direction and a second portion 84 extending along a second direction inclined with respect to the first direction in a plan view of the tread 10. The two first portions 82, 83 are respectively provided at both ends in the longitudinal direction of the slit 80. That is, the first portion 82 is connected to the main groove 20A, and the first portion 83 is connected to the main groove 20B. When the slit 80 has the first portions 82, 83 and the second portion 84 and has a bent shape, snow enters the inside of the slit 80 during driving on snow, and snow accumulates near the second portion 84 and is easily compacted. As a result, the snow column shearing force for gripping and compacting snow is improved, and the traction performance on the snow-covered road surface can be improved. In other words, when the slit 80 does not have a bent shape but has a linear shape, snow cannot be sufficiently accumulated inside the slit 80, and a large snow column shearing force cannot be exerted.

[0075] As described above, the slit 80 is disposed opposite to the main groove 21A with the main groove 20A interposed therebetween. The first direction is configured to be substantially the same as the extending direction of the main groove 21A at the tip of the main groove 21A. Therefore, the first portion 82 is provided substantially on an extension of the main groove 21A via the main groove 20A. In a plan view of the tread 10, the inclination angle of the first direction with respect to the tire axial direction is, for example, 40° or more and 90° or less, preferably 50° or more and 80° or less.

[0076] In the present embodiment, in a plan view of the tread 10, the angle formed by the first direction and the second direction is approximately 90°. That is, the second portion 84 is substantially orthogonal to the first portions 82, 83. By setting the angle formed by the first direction and the second direction to approximately 90°, more snow can be accumulated near the second portion 84. As a result, a large snow column shearing force can be exerted, and the traction performance on the snow-covered road surface can be improved. Note that the angle formed by the first direction and the second direction may be 90° or less. For example, the angle formed by the first direction and the second direction may be 45° or more and 90° or less.

[0077] The width of the second part 84 may be the same as that of the first parts 82, 83, or may be larger than that of the first parts 82, 83. By making the width of the second part 84 larger than that of the first parts 82, 83, more snow can be accumulated in the second part 84. As a result, a large snow column shearing force can be exerted, and the traction performance on the snow-covered road surface can be improved. The width of the first parts 82, 83 is, for example, 1.5 mm or more and 4.0 mm or less, and the width of the second part 84 is, for example, 2.0 mm or more and 6.0 mm or less.

[0078] Also, the width of the first part 82 and the width of the first part 83 may be different from each other. For example, the width of the first part 83 located on the stepping-in side may be made larger than the width of the first part 82 located on the kicking-out side. Also, the widths of the first parts 82, 83 may be uniform in the first direction, or may be different in the first direction. For example, the widths of the first parts 82, 83 may be configured to become smaller as they approach the main grooves 20A, 20B. Also, the width of the first part 82 located on the kicking-out side may be configured to become smaller as it approaches the main groove 20B, and the width of the first part 83 located on the stepping-in side may be made uniform in the first direction.

[0079] The depth (H80 (see FIGS. 5 and 6)) of the slit 80 is, for example, substantially the same as the depth of the slit 90, and specifically, is substantially the same as the depth of the portion where the bridge 23 (see FIG. 3) of the main groove 21 (see FIG. 3) is provided. The depth (H80) of the slit 80 is, for example, 40% or more and 100% or less of the depth of the main groove 20, preferably 50% or more and 90% or less, more preferably 50% or more and 80% or less. Also, in the present embodiment, the depths of the first parts 82, 83 and the second part 84 are substantially uniform, but the depths of the first parts 82, 83 and the second part 84 may be different from each other. For example, the depth of the second part 84 may be made larger than the depths of the first parts 82, 83.

[0080] As described above, the sipe 85 is provided on the bottom surface 80A of the slit 80. By providing the sipe 85, the block can move appropriately, and good road surface followability on the snow-covered road surface can be obtained. Further, when a load is applied to the block from above, below, left, and right in a plan view of the tread 10, the blocks separated by the sipe 85 support each other, thereby rigidifying the block, and improving the handling stability and braking performance on the dry road surface. That is, by providing the sipe 85 on the bottom surface 80A of the slit 80 having a bent shape, it is possible to achieve both an improvement in road surface followability on the snow-covered road surface and an improvement in handling stability and braking performance on the dry road surface in a high dimension.

[0081] In the present embodiment, the sipe 85 is provided over the length direction of the slit 80, and both ends in the length direction of the sipe 85 are connected to the main grooves 20A and 20B. By connecting both ends in the length direction of the sipe 85 to the main grooves 20A and 20B, the above-described effects of improving the handling stability and braking performance on the dry road surface are more exerted. Further, the sipe 85 may have a bent shape, but in the present embodiment, it has a linear shape and extends along the first direction.

[0082] As described above, since both ends in the length direction of the sipe 85 are connected to the main grooves 20A and 20B, the bottom surface 80A of the slit 80 (see FIGS. 5 and 6) is divided by the sipe 85 into a first region 87 located on the equator CL side and a second region 88 located on the ground contact end E1 side. In the first region 87, both ends in the length direction of the slit 80 are connected to the main grooves 20A and 20B, and in the second region 88, only the end portion located on the stepped-in side among both ends in the length direction of the slit 80 is connected to the main groove 20B. That is, the first region 87 is provided over the length direction of the slit 80, while the second region 88 is not provided over the length direction of the slit 80. With this configuration, more snow can be accumulated inside the slit 80 during snow driving. As a result, a large snow column shear force can be exerted, and the traction performance on the snow-covered road surface can be improved.

[0083] Referring further to FIGS. 5 and 6, the cross-sectional shape of the slit 80 will be described in detail. FIG. 5 is a cross-sectional view taken along line A-A of FIG. 4, and FIG. 6 is a cross-sectional view taken along line B-B of FIG. 4.

[0084] As shown in FIGS. 5 and 6, the width (W85) of the sipes 85 is preferably 0.8 mm or more, more preferably 0.9 mm or less, and still more preferably 1.0 mm or more. By setting the width (W85) of the sipes 85 to 0.8 mm or more, the blocks move appropriately during running, and better road surface followability can be obtained on a snow-covered road surface. In addition, the blocks separated by the sipes 85 support each other, enabling the rigidification of the blocks, and further improving the handling stability and braking performance on a dry road surface. In other words, when the width (W85) of the sipes 85 is less than 0.8 mm, the movement of the blocks may be excessively restricted. As a result, the effect of improving the road surface followability on a snow-covered road surface may not be fully obtained. Note that the width (W85) of the sipes 85 means the width at the bottom surface 80A of the slit 80.

[0085] Also, the width (W85) of the sipes 85 is preferably less than 1.5 mm, more preferably 1.4 mm or less, and still more preferably 1.3 mm or less. When the width (W85) of the sipes 85 is 1.5 mm or more, excessive tilting of the blocks may occur during cornering on a dry road surface, and the handling stability may decrease. Therefore, the width (W85) of the sipes 85 is preferably 0.8 mm or more and less than 1.5 mm, more preferably 0.9 mm or more and 1.4 mm or less, and still more preferably 1.0 mm or more and 1.3 mm or less.

[0086] As shown in Fig. 5, the depth (H85) of the sipe 85 is preferably 50% or more and 120% or less, more preferably 60% or more and 110% or less, and more preferably 70% or more and 100% or less of the depth (H80) of the slit 80. In this case, the effect of improving the steering stability when traveling on a dry road surface is more significantly exhibited. Note that the depth (H85) of the sipe 85 means the length along the tire radial direction from the bottom surface 80A of the slit 80 to the groove bottom of the sipe 85.

[0087] Moreover, it is preferable that the sum (H80+H85) of the depth (H80) of the slit 80 and the depth (H85) of the sipe 85 is equal to or smaller than the depth of the main groove 20 (see FIG. 2). In this embodiment, the side walls on the groove bottom side of the slit 80 and the sipe 85 are gently inclined so that the width narrows toward the groove bottom side.

[0088] 6, in the first portion 83 located on the leading side, the sipes 85 are provided so as to divide the bottom surface 80A of the slit 80 into a first region 87 located on the equator CL side and a second region 88 located on the ground contact edge E1 side. From the viewpoint of improving the steering stability on dry road surfaces, the ratio (W88 / W87) of the width (W88) of the second region 88 to the width (W87) of the first region 87 is preferably 0.5 to 1.5, and more preferably 0.7 to 1.3.

[0089] Hereinafter, the mold 100 for molding the tread 10 of the pneumatic tire 1 of the present embodiment will be described in detail with reference to Figures 7 and 8. Figure 7 is a cross-sectional view that shows the mold 100 in schematic form, and Figure 8 is a plan view of the tread molding surface 111 of the mold 100 as seen from above, showing an enlarged view of the vicinity of a third rib portion 106 described below.

[0090] As shown in FIG. 7, the mold 100 includes a molding surface 110 that contacts the outer surface of the unvulcanized tire set in the cavity 130. The molding surface 110 has a tread molding surface 111 that molds the tread 10 (see FIG. 1) of the pneumatic tire 1 and a side molding surface 112 that molds the sidewall 11 (see FIG. 1) of the pneumatic tire 1.

[0091] The mold 100 includes a tread ring 101 composed of a plurality of sectors and side plates 102, 103. The tread ring 101 plays a role in molding the tread 10 of the pneumatic tire 1. The side plates 102, 103 play a role in molding the sidewall 11 of the pneumatic tire 1. At the time of mold clamping, a plurality of sectors are connected in the tire circumferential direction to form an annular tread ring 101. On the other hand, at the time of mold opening, the tread ring 101 and the side plate 103 rise, and each sector is displaced outward in the tire radial direction so as to radially expand.

[0092] Each sector constituting the tread ring 101 includes a tread molding surface 111. The tread molding surface 111 is provided with exhaust holes (not shown) having openings in the tread molding surface 111. Through the exhaust holes, the air between the outer surface of the unvulcanized tire and the tread molding surface 111 is discharged during vulcanization molding, thereby preventing the occurrence of molding defects caused by rubber defects called bears.

[0093] As shown in FIGS. 7 and 8, the tread molding surface 111 is provided with a plurality of rib portions 104 for groove molding protruding inward in the tire radial direction. The rib portions 104 include, for example, a first rib portion 105 for forming the main grooves 20, 21 (see FIG. 2) in the tread 10, a second rib portion (not shown) for forming the slits 70, 71 (see FIG. 2), a third rib portion 106 (corresponding to a bent rib portion) for forming the slits 80, 81 (see FIG. 2), and a fourth rib portion (not shown) for forming the slit 90. The rib portion 104 shown in FIG. 7 is integrally provided with the tread ring 101 by casting and is not composed of a blade or the like attached to the tread molding surface 111.

[0094] In this embodiment, the first bone portion 105 extends from the center in the tire axial direction toward the outside in the tire axial direction. The second bone portion and the third bone portion 106 extend so as to connect adjacent first bone portions. Further, the fourth bone portion extends so that only one end in the length direction is connected to the first bone portion 105. Note that the configurations of the first bone portion 105, the second bone portion, the third bone portion 106, and the fourth bone portion are not limited to this.

[0095] The tread ring 101 including the bone portion 104 is made of a metal material, for example, an aluminum alloy. As the aluminum alloy, for example, AC4 series, AC7 series, etc. are used.

[0096] As shown in FIG. 8, the third bone portion 106 has a bent shape. The third bone portion 106 includes two third portions 107, 108 extending along the third direction and a fourth portion 109 extending along the fourth direction inclined with respect to the third direction in a plan view of the tread molding surface 111. The two third portions 107, 108 are provided at both ends in the length direction of the third bone portion 106, respectively. Further, a sipe blade 120 projects from the inner side in the tire diameter direction of the third bone portion 106.

[0097] The sipe blade 120 has, for example, a flat plate shape. The sipe blade 120 is made of a metal material and may be made of, for example, stainless steel. As the stainless steel, for example, SUS303, SUS304, SUS630, SUS631, etc. are preferably used. Further, when a three-dimensional modeling machine is used, 17-4PH equivalent materials such as SUS304L and SUS630 are preferably used.

[0098] In a plan view of the tread molding surface 111, it is preferable that the sipe blade 120 projects from the bent bone portion so that at least a part of the side surface of the sipe blade 120 coincides with the side surface of the third bone portion 106. In this case, the strength of the third bone portion 106 can be increased. As a result, deformation and breakage of the third bone portion 106 can be suppressed during tire molding.

[0099] As described above, the tread 10 of the pneumatic tire 1 of the present embodiment has slits 80, 81 including first portions 82, 83 extending along a first direction and second portions 84 extending along a second direction inclined with respect to the first direction in a plan view of the tread 10. And the first portions 82, 83 are provided at both longitudinal ends of the slits 80, 81. By providing the slits 80, 81 described above, a large amount of snow can be accumulated inside the slits 80, 81. As a result, a large snow column shear force can be exerted, and the traction performance on a snow-covered road surface can be improved. Further, a sipe 85 is provided on the bottom surface 80A of the slit 80. By providing the sipe 85, the blocks move appropriately during running, and good road surface followability can be obtained on a snow-covered road surface. Further, in a plan view of the tread 10, when a load is applied to the blocks from the vertical and horizontal directions, the blocks separated by the sipe 85 support each other, so that the blocks can be rigidified, and the handling stability and braking performance on a dry road surface are improved. That is, according to the pneumatic tire 1 of the present embodiment, it is possible to achieve both an improvement in road surface followability on a snow-covered road surface and an improvement in handling stability and braking performance on a dry road surface in a high dimension.

[0100] Note that the above embodiment can be appropriately modified in design without impairing the object of the present invention. For example, in the above embodiment, the first block group 30 has three blocks and the second block group 40 has two blocks, but the present invention is not limited to this. For example, the number of blocks constituting the first block group 30 and the second block group 40 may be the same as each other. Further, for example, the first block group 30 may have four blocks and the second block group 40 may have three blocks.

Explanation of reference numerals

[0101] 1 Pneumatic tire, 10 Tread, 11 Sidewall, 12 Side rib, 13 Bead, 14 Carcass, 15 Inner liner, 16 Bead core, 17 Bead filler, 18 Belt, 19 Cap ply, 20, 20A, 20B Main groove (First main groove), 21, 21A, 21B Main groove (Second main groove), 22, 22A, 22B, 23, 23A, 23B Bridge, 30 First block group, 31 First center block, 32 First intermediate block, 32A Outer end, 33 First shoulder block, 40 Second block group, 41 Second center block, 41A Outer end, 42 Second shoulder block, 50 First block group, 51 First center block, 52 First intermediate block, 53 First shoulder block, 60 Second block group, 61 Second center block, 62 Second shoulder block, 70, 70A, 70B, 71, 71A, 71B Slit, 72, 72A, 72B, 73, 73A, 73B Bridge, 74 Inclined region, 80, 81 Slit, 80A Bottom surface, 82, 83 First part, 82A Sidewall, 84 Second part, 85 Sipe, 85A Sidewall, 87 First region, 88 Second region, 90 Slit, 91 Narrow region, 92 Sipe (First sipe), 93 Sipe (Second sipe) 100 Mold (Tire molding mold), 101 Tread ring, 102, 103 Side plate, 104 Bone part, 105 First bone part, 106 Third bone part (Bending bone part), 107, 108 Third part, 109 Fourth part, 110 Molding surface, 111 Tread molding surface, 112 Side molding surface, 120 Sipe blade, 130 Cavity

Claims

1. A pneumatic tire having a tread and a specified rotational direction, wherein the tread includes a plurality of main grooves extending from the equator side toward the ground contact end side, blocks provided along the main grooves and arranged alternately with the main grooves in the tire circumferential direction, slits connecting adjacent main grooves in the tire rotational direction and having a bent shape, and the slit includes a first portion extending along a first direction and a second portion extending along a second direction inclined with respect to the first direction in a plan view of the tread, the first portions are provided at both ends in the length direction of the slit, and sipes are provided on the bottom surface of the slit. A pneumatic tire.

2. The pneumatic tire according to claim 1, wherein both ends in the length direction of the sipe are connected to the main groove.

3. The pneumatic tire according to claim 1, wherein the width of the sipe is 0.8 mm or more and less than 1.5 mm.

4. The pneumatic tire according to claim 1, wherein the sipe extends along the first direction.

5. The bottom surface of the slit is divided by the sipe into a first region located on the equator side and a second region located on the ground contact end side, both ends in the length direction of the first region are connected to the main groove, and in the second region, only the end located on the front side in the tire rotational direction among both ends in the length direction of the slit is connected to the main groove. The pneumatic tire according to claim 1.

6. The pneumatic tire according to claim 1, wherein the depth of the sipe is 50% or more and 150% or less of the depth of the slit.

7. The angle formed by the first direction and the second direction is 45° or more and 90° or less. The pneumatic tire according to claim 1.

8. The width of the slit in the second portion is larger than the width of the slit in the first portion. The pneumatic tire according to claim 1.

9. The main groove is a first main groove extending from the equator side toward the first grounding end side at one end in the tire axial direction, a second main groove extending from the equator side toward the second grounding end side at the other end in the tire axial direction, and includes The slit is disposed opposite to the second main groove with the first main groove therebetween. The pneumatic tire according to claim 1.

10. The main groove has a greater inclination with respect to the tire axial direction on the equator side than on the grounding end side. The pneumatic tire according to claim 1.

11. The block has a center block located on the equator side, a shoulder block located on the grounding end side, and a mediate block disposed between the center block and the shoulder block. The slit partitions the center block and the mediate block. The pneumatic tire according to claim 1.

12. The block has a first block group and a second block group that are alternately arranged with the main groove therebetween in the tire circumferential direction. The first block group has a first center block located on the equator side, a first shoulder block located on the grounding end side, and a first mediate block disposed between the first center block and the first shoulder block. The second block group has a second center block located on the equator side and a second shoulder block located on the grounding end side. The slit partitions the first center block and the first intermediate block, and the pneumatic tire according to claim 1.

13. A tire molding die having a sipe blade attached to a molding surface that contacts the outer surface of an unvulcanized tire, The molding surface is provided with a plurality of rib portions for forming grooves that protrude toward the inner side in the tire diameter direction, The plurality of rib portions include a bent rib portion having a bent shape, The bent rib portion includes a third portion extending along a third direction and a fourth portion extending along a fourth direction inclined with respect to the third direction in a plan view of the molding surface, Both ends in the length direction of the bent rib portion are provided with the third portion, The sipe blade protrudes from the bent rib portion, and the tire molding die.

14. The sipe blade protrudes from the bent rib portion such that at least a part of a side surface of the sipe blade coincides with a side surface of the bent rib portion in a plan view of the molding surface, and the tire molding die according to claim 13.

Images