pneumatic tires

Abstract

To provide a pneumatic tire which is excellent in brake performance.SOLUTION: A pneumatic tire 1 includes a tread 10, a carcass 15, a belt 16, and a reinforcement layer 2, and has a designated main rotation direction. The tread 10 has center blocks 30 and 40, shoulder blocks 50 and 60, and mediate blocks 70 and 80. The shoulder blocks 50 and 60 are formed with sipes 51 and 61 including inclination surfaces inclined so that groove widths are wider toward a ground surface E. The reinforcement layer 2 has a first area 2a, and a second area 2b having thickness larger than that of the first area 2a. The second area 2b is arranged in a range overlapping the ground surface of the shoulder blocks 50 and 60 in a tire radial direction.SELECTED DRAWING: Figure 1

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, so-called one-way tires have been known, which are pneumatic tires having a plurality of blocks arranged along the tire circumferential direction and a designated main rotation direction (see, for example, Patent Document 1). The tire of Patent Document 1 has a tread formed with a plurality of main grooves inclined relative to the tire width direction, and each block has a plurality of sipes. Tires with such a tread pattern exhibit good braking performance on dry, wet, and snowy road surfaces, for example, and are used as all-season tires. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. WO2014 / 084325 Summary of the Invention [Problem to be solved by the invention]

[0004] Meanwhile, tires such as all-season tires are required to exhibit high grip and good braking performance on all road conditions, and it is necessary to improve braking performance without compromising other tire performances such as rolling resistance.

[0005] An object of the present invention is to provide a pneumatic tire that exhibits excellent braking performance under all road surface conditions. [Means for solving the problem]

[0006] The pneumatic tire of the present invention is a pneumatic tire having a specified main rotation direction, comprising a tread, a carcass, a belt arranged between the tread and the carcass, and a reinforcing layer arranged between the tread and the belt so as to cover the outer surface of the belt, wherein the tread has a plurality of center blocks formed in the circumferential direction of the tire in a central region of the width of the tread, a plurality of shoulder blocks formed in the circumferential direction of the tire in both side regions of the width of the tread, and a plurality of intermediate blocks formed in the circumferential direction of the tire between the center blocks and the shoulder blocks, and the shoulder blocks have sipes formed in the shoulder blocks, including slopes that are inclined so that the groove width widens toward the contact surface, and the reinforcing layer has a first region and a second region that is thicker than the first region, and the second region is arranged in an area that overlaps with the contact surfaces of the shoulder blocks in the radial direction of the tire. [Effects of the Invention]

[0007] The pneumatic tire according to the present invention exhibits excellent braking performance in all road surface conditions, and is suitable as an all-season tire. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view of a pneumatic tire as an example of an embodiment. [Figure 2] 1 is a plan view of a pneumatic tire as an example of an embodiment. [Figure 3] FIG. 2 is a diagram schematically illustrating the shape of the contact surface of the 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 view showing a cross section of a shoulder block in the tire circumferential direction. [Figure 6] FIG. 2 is an enlarged plan view showing the left side portion of the tread in the width direction, and is a diagram for explaining the length of the slope formed on the sipe, etc. DETAILED DESCRIPTION OF THE INVENTION

[0009] 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.

[0010] FIG. 1 is a diagram showing a portion of a cross section along the width direction and the radial direction of a pneumatic tire 1 according to an embodiment (some hatching has been omitted for clarity of the drawing). FIG. 2 is a plan view of the pneumatic tire 1, showing a portion of a tread 10. In FIG. 2 and other figures, dot hatching is applied to the top surface of each block. The top surface of a block refers to the outermost surface of the block facing radially outward of the tire.

[0011] As shown in Figures 1 and 2, a pneumatic tire 1 has 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 has a plurality of main grooves 20, 21 that are inclined with respect to the width direction of the tread 10 so as to be gradually positioned rearward in the main rotation direction of the tire from a widthwise central region R1 (see Figure 3 described later) toward both widthwise side regions R2. The pneumatic tire 1 is a directional tire with a specified main rotation 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.

[0012] 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. For ease of explanation, the terms "left and right" are used for 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. The "tread width direction" and the "tire width direction" are the same direction, and both terms will be used appropriately below.

[0013] The tread 10 has a plurality of circumferential grooves extending in the tire circumferential direction. The plurality of circumferential grooves include a first circumferential groove 25 formed in a widthwise central region R1 of the tread 10, and second circumferential grooves 26, 27 formed on both the left and right sides (widthwise opposite regions R2) of the tread 10. In addition, in 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.

[0014] The tread 10 has multiple blocks defined by multiple main grooves 20, 21 and multiple circumferential grooves. The blocks are island-like protrusions that protrude radially outward and are generally referred to as land portions. The tread 10 has multiple center blocks 30, 40 formed in the tire circumferential direction in the widthwise central region R1, and multiple shoulder blocks 50, 60 formed in the tire circumferential direction in the widthwise side regions R2. The tread 10 also has multiple intermediate blocks 70 formed in the tire circumferential direction between the center blocks 30 and the shoulder blocks 50, and multiple intermediate blocks 80 formed in the tire circumferential direction between the center blocks 40 and the shoulder blocks 60.

[0015] In this embodiment, multiple blocks having substantially the same shape and size are arranged side by side in the tire circumferential direction. Taking the center blocks 30 as an example, the shape and size of each of the center blocks 30 arranged side by side in the tire circumferential direction are substantially the same. Furthermore, each row of blocks along the tire circumferential direction is composed of the same number of blocks. The tread 10 is formed with the same number of center blocks 30, 40, shoulder blocks 50, 60, and intermediate blocks 70, 80.

[0016] In the widthwise central region R1 of the tread 10, center blocks 30, 40 are arranged on either side of the tire equator CL. 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.

[0017] 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.

[0018] The pneumatic tire 1 includes a shoulder 11, a sidewall 12, and a bead 13 that form the side surface of the tire. In this embodiment, the ground contact edge E of the pneumatic tire 1 is the boundary position between the tread 10 and the shoulder 11, and an annular side rib 14 formed on the upper part of the side surface of the pneumatic tire 1 is the boundary position between the shoulder 11 and the sidewall 12. The bead 13 includes a bead core 18 and a bead filler 19.

[0019] In this specification, the ground contact edges E refer to both widthwise ends of the portion that comes into contact with a flat road surface when an unused pneumatic tire 1 is mounted on a standard rim and inflated to an internal pressure of 200 to 260 kPa and a load of 70% of the maximum load capacity is applied. 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 above internal pressure is applied. Here, a "standard rim" refers to a rim specified by tire standards, and is a "standard rim" in the case of JATMA, a "design rim" in the case of TRA, and a "measuring rim" in the case of ETRTO.

[0020] The internal pressure conditions of a tire generally change depending on the aspect ratio of the tire. As a specific example, if the aspect ratio of a pneumatic tire 1 is 60 or more, the internal pressure is set to 200 kPa for standard road standards and 240 kPa for extra load standards. If the aspect ratio is 55 or less, the internal pressure is set to 220 kPa for standard road standards and 260 kPa for extra load standards.

[0021] The pneumatic tire 1 includes a carcass 15, a belt 16 disposed between the tread 10 and the carcass 15, and a reinforcing layer 2 disposed between the tread 10 and the belt 16 so as to cover the outer peripheral surface of the belt 16. The carcass 15 is, for example, a cord layer coated with rubber, and is composed of two carcass plies, forming a tire skeleton that can withstand loads, impacts, air pressure, etc. An inner liner 17, which is a rubber layer for maintaining air pressure, is attached to the inner peripheral surface of the carcass 15.

[0022] The belts 16 are reinforcing bands stretched in the circumferential direction of the tire, and tighten the carcass 15 to increase the rigidity of the tread 10. The belts 16 are made of, for example, rubber-coated steel cords. In the example shown in FIG. 1, two belts 16 are arranged to cover the outer peripheral surface of the carcass 15. The inner belt 16 is wider than the outer belt 16, and at least both widthwise ends of the inner belt 16 are located outward in the tire width direction from the ground contact edge E.

[0023] The belt 16 is arranged, for example, to overlap the entire contact surface of the tread 10 in the tire radial direction. Of the two belts 16, at least the wider inner belt extends in the tire width direction to a position beyond the contact edge E. Both widthwise ends of the belt 16 are located within the range of the left and right shoulders 11. As will be described in detail later, the shoulder blocks 50 are formed with sipes 51 including slopes 52 that are inclined so that the groove width widens toward the contact surface (the same applies to the shoulder blocks 60). The slopes 52 distribute the contact pressure of the shoulder blocks 50, greatly contributing to improved braking performance and reduced rolling resistance.

[0024] The reinforcing layer 2 is disposed so as to cover the entire belt 16, and functions as a reinforcing layer that tightens the belt 16. The reinforcing layer 2 is, for example, an organic fiber layer (cord layer) coated with rubber, and is formed by winding organic fiber cords around the outer peripheral surface of the belt 16 in the tire circumferential direction. Examples of organic fiber cords include polyamide fiber, polyester fiber, and aramid fiber. The reinforcing layer 2 is wider than the belt 16, and extends outward in the tire width direction to positions beyond both ends of the belt 16 in the width direction.

[0025] The reinforcing layer 2 has a first region 2a and a second region 2b that is thicker than the first region 2a. An example of a suitable thickness for the second region 2b is 1.5 to 3.0 times, or 1.6 to 2.4 times, the thickness of the first region 2a. The second region 2b can be formed by, for example, doubling up the organic fiber cord, thereby increasing the number of layers of the organic fiber cord compared to when forming the first region 2a. The second region 2b is preferably formed with a predetermined width from both ends in the width direction of the reinforcing layer 2. An example of the width of each second region 2b is 10 to 20% of the overall width of the reinforcing layer 2.

[0026] The reinforcing layer 2 has a structure in which a first region 2a, which is a single organic fiber cord layer, is sandwiched from both sides in the width direction by a second region 2b formed by doubly wound organic fiber cords. In this embodiment, the second region 2b is arranged at a position overlapping both ends in the width direction of the two belts 16. The second region 2b covers the ends of the belts 16 along the tire circumferential direction, and both ends in the width direction of the second region 2b are located closer to the side rib 14 than both ends in the width direction of the belts 16 within the range of the left and right shoulders 11.

[0027] The second region 2b of the reinforcing layer 2 is disposed in an area that overlaps in the tire radial direction with the contact surfaces of the shoulder blocks 50, 60. This makes it possible to suppress expansion of both widthwise regions R2 of the tread 10 and reduce the contact pressure in the shoulder blocks 50, 60. With the pneumatic tire 1, the synergistic effect of the second region 2b of the reinforcing layer 2 and the slopes 52, 62 of the sipes 51, 61 makes it possible to effectively distribute the contact pressure in the shoulder blocks 50, 60.

[0028] The second region 2b preferably overlaps with at least 50% of the contact patch of the shoulder blocks 50, 60 in the tire radial direction. In this case, the effect of reducing ground pressure is more pronounced. The second region 2b may extend toward the tire equator CL beyond the contact patch of the shoulder blocks 50, 60, but even if the second region 2b is widely positioned toward the tire equator CL, the effect of reducing ground pressure is not as great. For this reason, from the perspective of reducing tire weight, etc., it is preferable that the widthwise inner end of the second region 2b be located closer to the contact edge E than the second circumferential grooves 26, 27.

[0029] The second region 2b radially overlaps with 50 to 100% of the contact surface of the shoulder blocks 50, 60, more preferably 50 to 70%. The second region 2b preferably radially overlaps with at least the contact edges E of the shoulder blocks 50, 60. This configuration provides a more pronounced reduction in contact pressure. In this embodiment, the second region 2b extends from the tire equator CL side of the contact edges E far beyond the contact edges E to approximately the midpoint between the contact edges E and the side ribs 14.

[0030] As described above, the tread 10 has main grooves 20, 21 that partition the block groups 100, 101. 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 in the tire circumferential direction. 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.

[0031] The main groove 20 and the block group 100 have a curved shape in plan view that is convex toward the rear in the tire main rotation direction. The main groove 21 and the block group 101 also have a curved shape in plan view that is convex toward the rear in the tire main rotation direction. The main grooves 20, 21 and the block groups 100, 101 are inclined in the same direction in the tire circumferential direction, and the inclination angle is larger on the tire equator CL side than on the ground contact edge E side. The inclination angle of the main grooves 20, 21 with respect to the tire width direction on the tire equator CL side is, for example, 30 to 60° or 40 to 50°.

[0032] The main groove 20 gradually conforms to the tire width direction from the tire equator CL side toward the ground contact edge E, and the inclination with respect to the tire width direction becomes gentler. The width of the main groove 20 is, for example, 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 26. 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 length of the ground contact surface of each block is, for example, 3:7 to 4:6. The main groove 21 is configured in the same manner as the main groove 20.

[0033] 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 before the ground edge E side, water, snow, and ice can be efficiently discharged from the tire equator CL side of the tread 10 toward the ground edge E side. In this case, good wet and snow performance can be obtained. The pneumatic tire 1 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.

[0034] The pneumatic tire 1 is preferably provided with a marking to indicate the mounting direction on the vehicle. A symbol generally called a serial number is provided on the sidewall 12. The serial number includes information such as a size code, manufacturing date (manufacturing year and week), and manufacturing location (manufacturing factory code). The mounting direction of the pneumatic tire 1 on the vehicle can be specified by providing a serial number only on the sidewall 12 facing the outside of the vehicle, or by providing different serial numbers on the left and right sidewalls 12. A specific example is to provide a manufacturing factory code and a size code on the first sidewall 12 and a manufacturing year and week on only the second sidewall 12.

[0035] The tread pattern 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 block group 100 is the same as the shape of block group 101 when it is inverted with respect to the tire equatorial plane (the same applies to 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 handling stability.

[0036] As described above, the tread 10 has a plurality of circumferential grooves that define rows of blocks aligned in the tire circumferential direction. The circumferential grooves are narrower than the main grooves 20, 21, intersect with the main grooves 20 or 21, and define the rows of blocks aligned in the tire circumferential direction. The first circumferential grooves 25 that separate the rows of center blocks 30, 40 are bent in opposite directions at the intersections with the main grooves 20, 21, and are formed in a zigzag shape that extends in the tire circumferential direction while intersecting the tire equator CL.

[0037] The second circumferential grooves 26, 27 are formed straight along the tire circumferential direction without bending at the intersections with the main grooves 20, 21. By forming the second circumferential grooves 26, 27, which are closest to the ground contact edge E, in a straight line, good drainage performance is achieved. The third circumferential grooves 28, 29 are grooves that separate the center block and the intermediate block, and are formed shallower than the main grooves 20, 21. 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's main rotational direction.

[0038] Thin sipes are formed in each block. In this embodiment, one sipe is formed in every block, and each sipe extends in a direction along the main groove 20 or the main groove 21. The sipes are thin grooves narrower than the main grooves 20, 21 and the circumferential grooves, and enhance the edge effect of catching snow and ice, thereby achieving good braking / driving performance and 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 a portion where there are no slopes, as described below. In this specification, a sipe is defined as a groove whose groove width in a portion not including a slope is 1.0 mm or less.

[0039] Figure 3 is a diagram showing a schematic diagram of the shape of the contact patch of the tread 10. As shown in Figure 3, the contact patch of the tread 10 has a small difference between the contact patch length (L1) and the contact patch length (L2), and has a shape that is close to a rectangle in a plan view. Here, the contact patch length (L1) refers to the length of the contact patch along the tire circumferential direction in the widthwise central region R1 where the center blocks 30, 40 are formed. The contact patch length (L2) refers to the length of the contact patch along the tire circumferential direction 10 mm inward from the contact edge E of the tread 10 (toward the tire equator CL).

[0040] The pneumatic tire 1 has a ratio (L2 / L1) of the contact length (L2) to the contact length (L1) of 0.75 to 0.90 when the internal pressure is 200 to 260 kPa and a load of 70% of the maximum load capacity is applied. If the contact length ratio (L2 / L1) is within this range, the contact area is increased, improving grip and providing excellent braking performance on various road conditions, including dry roads, wet roads, and snowy and icy roads. The contact length ratio (L2 / L1) can be increased, for example, by reducing the difference in height between the contact surfaces of the widthwise central region R1 and the widthwise side regions R2 of the tread 10 and angularizing the shoulders 11.

[0041] When the internal pressure is changed according to the aspect ratio of the tire, the optimum contact length ratio (L2 / L1) changes slightly, but when the tire has the tread pattern of this embodiment, excellent braking performance is achieved if the ratio (L2 / L1) is set to 0.75 to 0.90. In this embodiment, the contact length (L1) is approximately constant in the portion where the center blocks 30, 40 are formed. In addition, the contact length (L2) is substantially the same length on the left and right sides of the tread 10.

[0042] The contact length ratio (L2 / L1) is more preferably 0.77 or greater, and particularly preferably 0.78 or greater. When the internal pressure of the pneumatic tire 1 is 260 kPa, an example of a suitable range for the ratio (L2 / L1) is 0.80 to 0.90, or 0.82 to 0.88. It is generally believed that increasing the contact length ratio (L2 / L1) results in a decrease in snow performance; however, with the tread pattern of this embodiment, good braking performance is exhibited on snow and ice surfaces even when the ratio (L2 / L1) is increased. The hardness of the tread rubber is adjusted to, for example, 55 to 70 or 60 to 65. By slightly reducing the hardness of the tread rubber compared to conventional all-season tires, good snow performance can be easily ensured.

[0043] Hereinafter, each block constituting the tread pattern of this embodiment will be described in detail using three blocks constituting the block group 100 as an example, with reference to Figures 4 to 6 as appropriate in addition to Figure 2. Figures 4 and 6 are enlarged views showing the left side portion of the tread 10 in the width direction. Figure 5 is a cross-sectional view of a shoulder block 50 in the tire circumferential direction.

[0044] [Center Block] 2, the center blocks 30, 40 are island-shaped protrusions formed in the tire widthwise central region R1 of the tread 10. 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. Each center block 30, 40 is also formed with a single sipe 31, 41 along the extension direction of the main grooves 20, 21, i.e., along the longitudinal direction of each block.

[0045] The center blocks 30, 40 are arranged on either side of the tire equator CL, with the left center block 30 partially extending beyond the tire equator CL to the right, and the right center block 40 partially extending beyond the tire equator CL to the left. Note that the side walls of the center blocks 30, 40 are not entirely perpendicular to the block contact surface, and the lower portions of the side walls, particularly those near the groove bottom, are curved so that they extend outward from the block (the same applies to the side walls of the other blocks).

[0046] The ground contact area (A1) of the center block 30 is the smallest among the three blocks that make up the block group 100. In this specification, the ground contact area of ​​a block means 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.

[0047] The sipes 31 are formed in the center of the center block 30 in the short direction, extending over the entire length of the contact patch in the longitudinal direction, so as to divide the contact patch in half. The sipes 31 are formed from the contact patch to the groove bottom of the third circumferential groove 28, or deeper than the groove bottom, and are connected to the third circumferential groove 28. On the other hand, the sipes 31 are not connected to 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 sipes 31 can improve braking performance on snowy and icy roads.

[0048] The groove walls of the sipes 31 have slopes 32 that are inclined from the opening of the sipe to a predetermined depth range so that the groove width increases toward the opening. Unless otherwise specified, the opening of the sipe refers to the opening in the tread profile surface α (see FIG. 5) along the contact patch of the tread 10. The predetermined depth (the depth of the slopes 32) is, for example, 2.0 mm or less, and preferably 0.8 to 1.2 mm. The depth of the slopes 32 may be 10 to 30% of the depth of the sipes 31. The slopes 32 ensure the rigidity of the center block 30 while improving traction performance on snowy roads and drainage.

[0049] The slopes 32 are formed on groove walls along the length of the sipes 31. The inclination angle of the slopes 32 with respect to the profile surface is, for example, 20 to 50°, preferably 20 to 35° or 25 to 35°. If the inclination angle is within this range, the function of the slopes 32 is more effectively exhibited. Furthermore, during sudden braking or sudden acceleration, the slopes 32 come into contact with the road surface, suppressing collapse of the blocks. The maximum width of the slopes 32 is, for example, 1.5 to 2.5 mm. The maximum width of the slopes 32 may be 1.3 to 3.5 times, or 1.5 to 3 times, the width of the sipes 31 in the portions where the slopes 32 are not present.

[0050] The slope 32 is formed only on the second groove wall (groove wall on the trailing side) located on the rear side of the sipe 31 in the main rotational direction of the tire. Although the slope may be formed on the first groove wall (groove wall on the leading side) located on the front side of the main rotational direction of the tire, the slope is preferably formed only on the second groove wall. In this case, the effect of the slope 32 can be more effectively achieved while suppressing a decrease in the rigidity of the block. Furthermore, when the slope 32 is formed on the second groove wall, the slope 32 comes into contact with the road surface during sudden braking or sudden acceleration, making it easier to suppress collapse of the block. The first groove wall of the sipe 31 facing the second groove wall on which the slope 32 is formed is formed approximately perpendicular to the ground contact surface.

[0051] The slope 32 is formed within a predetermined length range from the sipe end on the third circumferential groove 28 side. The predetermined length is preferably a length that does not reach the sipe end on the tire equator CL side. As will be described in detail later, the slope 32 is formed to a length 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 slope 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.

[0052] 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 surface that is generally rectangular in a plan view and is generally parallel to the longitudinal direction of the sipe 31, and is formed over a length of 40% to 60% of the overall length of the slope 32. The second region 32b is a surface that is generally triangular in a plan view, and its area decreases with increasing distance from the first region 32a. 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.

[0053] Similar to the center block 30, the center block 40 has one sipe 41 formed along the extension direction of the main groove 21. Of the groove walls of the sipe 41, a second groove wall located on the rear side in the main rotational direction of the tire has a slope 42 formed within a predetermined depth range from the opening of the sipe such that the groove width increases toward the opening. In this embodiment, the shape of the center block 40 is the same as the shape of the center block 30 when it is inverted with respect to the tire equatorial plane, and if the inverted center block 30 is slid circumferentially in the tire, it will match the center block 40.

[0054] [Shoulder Block] 2 and 4, the shoulder blocks 50, 60 are island-shaped protrusions formed in the tread 10 on both sides in the tire width direction (region R2), with portions extending beyond the ground contact edge E toward the sidewall 12. The shoulder blocks 50, 60 have a significantly curved upper surface from the ground contact edge E to the side rib 14. Like 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, with the longitudinal direction of each block slightly inclined relative to the tire width direction. Furthermore, each shoulder block 50, 60 is formed with a single sipe 51, 61 along the extension direction of the main grooves 20, 21.

[0055] The shoulder blocks 50 are larger than the center blocks 30 and the intermediate blocks 70, and have the longest length in the tire width direction of the three blocks. In this embodiment, the shape of the shoulder blocks 60 is the same as the shape of the shoulder blocks 50 when inverted relative to the tire equatorial plane, and if the inverted shoulder blocks 50 are slid in the tire circumferential direction, they will match the shoulder blocks 60.

[0056] The sipes 51 are formed in the center of the shoulder block 50 in the short direction, extending from the second circumferential groove 26 along the longitudinal direction of the block, beyond the ground contact edge E, but not reaching the side rib 14. The sipes 51 are disposed opposite the sipes 71 of the intermediate block 70 across the second circumferential groove 26.

[0057] The groove walls of the sipes 51 have slopes 52 that slope from the sipe opening to a predetermined depth range so that the groove width increases toward the opening. The slopes 52 ensure the rigidity of the shoulder blocks 50 while dispersing the ground pressure of the shoulder blocks 50, where ground pressure tends to concentrate, thereby improving friction with the road surface. Therefore, the slopes 52 greatly contribute to improving braking performance. Note that the sipes 61 of the shoulder blocks 60 also have slopes 62 similar to the slopes 52.

[0058] As shown in FIG. 5, the depth D2 of the slope 52 is, for example, 2.0 mm or less, and preferably 0.8 to 1.2 mm. The depth D2 of the slope 52 may be 5 to 30% of the maximum depth D1 of the sipe 51. If the depth D1 of the slope 52 is within this range, the block rigidity can be ensured while the ground pressure can be effectively dispersed. In this embodiment, the slope 52 is shallower than the slope 32 of the center block 30. The depth D1 of the slope 52 is, for example, 60 to 90% or 65 to 85% of the depth of the slope 32. In this embodiment, by adopting a configuration in which the slightly shallow slope 52 is formed long, the block rigidity and the ground pressure dispersion effect are both ensured to a higher degree.

[0059] The inclination angle θ of the inclined surface 52 with respect to the profile surface α is, for example, 20 to 50°, preferably 20 to 35°, or 25 to 35°. If the inclination angle θ is within this range, the function of the inclined surface 52 is more effectively exhibited. The inclination angle θ of the inclined surface 52 may be substantially the same as the inclination angle of the inclined surface 32. The maximum width W2 of the inclined surface 52 is, for example, 1.5 to 2.5 mm, and is 1.3 to 3.5 times, preferably 1.5 to 3 times, or 1.5 to 2.5 times the width W1 of the sipe 51 in the portion where the inclined surface 52 is not present. The width W2 of the inclined surface 52 is, for example, 60% to 90%, or 65% to 85% of the width of the inclined surface 32.

[0060] The slope 52 is formed only on the second groove wall located on the rear side of the sipe 51 in the main rotational direction of the tire. Although the slope may be formed on the first groove wall located on the front side in the main rotational direction of the tire, it is preferable to form the slope only on the second groove wall. In this case, the effect of the slope 32 can be more effectively achieved while suppressing a decrease in the rigidity of the block. Furthermore, when the slope 52 is formed on the second groove wall, the slope 52 comes into contact with the road surface during sudden braking or sudden acceleration, making it easier to suppress the collapse of the block. The first groove wall of the sipe 51 is formed approximately perpendicular to the contact surface.

[0061] The slope 52 is formed from the second circumferential groove 26 to a position slightly 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. Furthermore, 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, thereby improving the durability of the block. Note that it is preferable to position the end of the slope 52 near the ground contact edge E to suppress a decrease in block rigidity. The slope 52 is formed to a length that is, for example, 30 to 60% of the longitudinal length of the top surface of the block.

[0062] The slope 52 is formed in a portion adjacent to the second circumferential groove 26 and faces the slope 72 of the mediate block 70 across the second circumferential groove 26. 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 the snow column shear force.

[0063] [Mediate Block] As shown in FIGS. 2 and 4, the mediate block 70 is an island-shaped raised portion provided between the center block 30 and the shoulder block 50. 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 and 40 and the shoulder blocks 50 and 60, the mediate blocks 70 and 80 have a generally rectangular shape in a plan view that is elongated in the direction in which the main grooves 20 and 21 extend. The inclination angle of the mediate blocks 70 and 80 with respect to the tire width direction is the same as or slightly gentler than the inclination angle of the center blocks 30 and 40. Furthermore, one sipe 71 and 81 are formed in the mediate blocks 70 and 80 along the direction in which the main grooves 20 and 21 extend.

[0064] The mediate block 70 is larger than the center block 30 and smaller than the shoulder block 50. On the other hand, the ground contact area (A3) of the mediate block 70 may be the largest among the ground contact areas of the three blocks constituting the block group 100. Similarly, the ground contact area of ​​the mediate block 80 may be the largest among the ground contact areas of the three blocks constituting the block group 101. In this embodiment, the shape of the mediate block 80 is the same as the shape of the mediate block 70 when it is inverted with respect to the tire equatorial plane, and if the inverted mediate block 70 is slid in the tire circumferential direction, it will match the mediate block 70.

[0065] The sipe 71 is formed in the center of the intermediate block 70 in the short direction, extending over the entire length of the block in the longitudinal direction, so as to divide the block in half. The sipe 71 is connected to the third circumferential groove 28, and is disposed opposite the sipe 31 of the center block 30, with the third circumferential groove 28 in between. The sipe 71 is also connected to the second circumferential groove 26, and is disposed opposite the sipe 51 of the shoulder block 50, with the second circumferential groove 26 in between.

[0066] The groove walls of the sipes 71 have slopes 72 that are inclined from the opening of the sipe to a predetermined depth range so that the groove width increases toward the opening. The slopes 72 have the same function as the slopes of other blocks, ensuring the rigidity of the block while dispersing ground pressure, improving drainage, and expanding snow pockets. Note that the sipes 81 of the intermediate blocks 80 also have slopes 82 similar to the slopes 72.

[0067] The slope 72, like the slopes of the other blocks, is formed only on the second groove wall located on the rear side of the sipe 71 in the main rotational direction of the tire. The first groove wall facing the second groove wall of the sipe 71 is formed approximately perpendicular to the ground contact surface. The slope angle of the slope 72 with respect to the profile plane α is, for example, 20 to 50°, and preferably 20 to 35° or 25 to 35°. The slope angle, width, and depth of the slope 72 are, for example, substantially the same as the slope angle, width, and depth of the slope 32 of the center block 30.

[0068] The inclined surface 72 is formed within a predetermined length range from the second circumferential groove 26. The predetermined length is preferably a length that does not reach the sipe end on the third circumferential groove 28 side. The inclined surface 72 includes two regions (a first region 72a and a second region 72b) that have different shapes in a plan view. The first region 72a is a surface that is generally rectangular in a plan view and is generally parallel to the longitudinal direction of the sipe 71, and is formed over a length that exceeds 50%, preferably 70% to 90%, of the entire length of the inclined surface 72. The second region 72b is a surface that is generally triangular in a plan view, and its area decreases with increasing distance from the first region 72a. By providing the second region 72b, the step formed at the end of the inclined surface 72 can be made gentler, thereby suppressing stress concentration at the end of the inclined surface 72.

[0069] [Blocks] The block group 100 has a raised portion 90 formed therein that connects the lower portions of the shoulder blocks 50 and the mediate blocks 70. By providing the raised portion 90, the rigidity of the two connected blocks can be increased, improving dry performance. The raised portion 90 is formed only within the area sandwiched between the shoulder blocks 50 and the mediate blocks 70 within the second circumferential groove 26. The block group 100 also has a third circumferential groove 28 formed therein that separates the center block 30 and the mediate block 70, but its depth is shallower than that of the main groove 20.

[0070] At least a portion of the first circumferential groove 25 separating the block groups 100, 101 is formed shallower than the main groove 20, similar to the third circumferential groove 28. That is, 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 adjacent in the tire circumferential direction, and 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.

[0071] As shown in Fig. 6, among the three blocks constituting the block group 100, the shoulder block 50 is the largest, but with respect to the ground contact area, the ground contact area (A3) of the mediate block 70 is greater than or equal to the ground contact area (A2) of the shoulder block 50. By making the ground contact area (A3) of the mediate block 70 greater than or equal to the ground contact area (A2) of the shoulder block 50, the handling performance during steady driving is improved. The ground contact area (A3) is preferably, for example, larger than the ground contact area (A2) and less than or equal to 1.3 times, or less than or equal to 1.2 times the ground contact area (A2). The ground contact area (A1) of the center block 30 is preferably smaller than the ground contact area (A2).

[0072] The ground contact areas of the three blocks constituting the block group 100 satisfy the condition 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 ground contact area as in the case of the block group 100.

[0073] When the total of the ground contact areas of the three blocks constituting the block group 100 is taken as 100%, an example of the suitable ground contact area of each block is as follows. Ground contact area (A1): 25% - 32%, preferably 27% - 32% Ground contact area (A2): 33% - 38%, preferably 33% - 36% Ground contact area (A3): 34% - 42%, preferably 35% - 40% If the conditions A1 < A2 ≤ A3, preferably A1 < A2 < A3 are satisfied and the ratios of the ground contact areas (A1 - A3) are within the said range, the braking performance and the handling performance during steady driving can be more highly compatible.

[0074] Regarding the length of each slope, the length L along the side 31 of the slope 32 with respect to the longitudinal length L of the upper surface of the center block 30 30 of the ratio (L 32 along the side 31 of the slope 32 with respect to the longitudinal length L of the upper surface of the center block 32 / L 30) The longitudinal length L of the upper surface of the shoulder block 50 50 and the length L along the side 51 of the inclined surface 52 with respect to L 52 of the ratio (L 52 / L 50 ), and the longitudinal length L of the upper surface of the intermediate block 70 70 and the length L along the side 71 of the inclined surface 72 with respect to L 72 of the ratio (L 72 / L 70 ), when they are respectively X1, X2, and X3, it is preferable that the ratio (X2) is larger than the ratio (X1) and the ratio (X3). That is, among the three blocks constituting the block group 100, the ratio (X2) of the shoulder block 50 is the largest.

[0075] In this embodiment, the ratio (X1) of the center block 30 is the second largest, and the ratio (X3) of the intermediate block 70 is the smallest. That is, the pneumatic tire 1 satisfies the condition of X3 < X1 < X2. In this case, the braking performance is improved in various road surface conditions such as wet road surfaces, snow road surfaces, and dry road surfaces, and the wet performance, snow performance, and dry performance are effectively improved. On the other hand, regarding the width and depth of the inclined surface, they are the smallest in the inclined surface 52 of the shoulder block 50 compared to the inclined surface 32 of the center block 30 and the inclined surface 72 of the intermediate block 70.

[0076] 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. 6, for the sake of clarity of the drawing, the longitudinal length of the block upper surface is illustrated by an arrow along the tire width direction. However, since the block is inclined with respect to the tire width direction and especially the upper surface of the shoulder block 50 is greatly curved, the length L 50 in the shoulder block 50 is longer than the illustrated length. Similarly, regarding the length along the side of the inclined surface, as shown in FIG. 7, since the side is inclined with respect to the tire width direction, it is longer than the illustrated length.

[0077] An example of a suitable ratio of the length along the slope to the longitudinal length of the block upper surface along the upper surface of each block constituting the block group 100 is as follows. Ratio (X1): 30% to 50%, preferably 35% to 45% Ratio (X2): 30% to 60%, preferably 45% to 55% Ratio (X3): 20% to 40%, preferably 25% to 30% If the conditions of X3 < X1 < X2 are satisfied and the ratios (X1 to X3) are within the above ranges, the wet performance, snow performance, and dry performance can be more effectively improved.

[0078] The length L of the slope 52 52 is preferably longer than the length L of the slope 32 32 and the length L of the slope 72 72 Also, the length L of the slope 32 32 is preferably longer than the length L of the slope 72 72 That is, the pneumatic tire 1 satisfies the condition of L 72 < L 32 < L 52 The length L of the slope 52 52 is, for example, 2 to 4 times, or 2.5 to 3.5 times the length L of the slope 32 (the same applies to the length of the slope 52 on the block ground contact surface). The sipes 51 and the slopes 52 are formed over the entire length of the ground contact surface of the shoulder blocks 50 as described above. 32 As described above, according to the pneumatic tire 1 having the above configuration, excellent braking performance can be exhibited in any road surface condition. By providing the shoulder blocks 50, 60 in which the sipes 51, 61 including the slopes 52, 62 are formed and arranging the second region 2b of the reinforcing layer 2 in the range overlapping with the ground contact surface of the shoulder blocks 50, 60 in the tire radial direction, the ground contact pressure of the shoulder blocks 50, 60 can be effectively dispersed, and excellent braking performance can be exhibited.

[0079] As described above, according to the pneumatic tire 1 having the above configuration, excellent braking performance can be exhibited in any road surface condition. By providing the shoulder blocks 50, 60 in which the sipes 51, 61 including the slopes 52, 62 are formed and arranging the second region 2b of the reinforcing layer 2 in the range overlapping with the ground contact surface of the shoulder blocks 50, 60 in the tire radial direction, the ground contact pressure of the shoulder blocks 50, 60 can be effectively dispersed, and excellent braking performance can be exhibited.

[0080] 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 both wet and dry performance as well as snow performance. In this embodiment, by appropriately setting the ratio of the contact area and contact length of each block in a well-balanced manner in addition to the configuration of the sipes in the shoulder blocks and the configuration of the reinforcing layer, the entire tread 10 achieves performance suitable for an all-season tire.

[0081] The above-described embodiment may be modified as needed within the scope of the present invention. For example, the tire may have a tread pattern including main grooves, circumferential grooves, center blocks, intermediate blocks, and shoulder blocks with sipes including sloped surfaces, and the second regions of the reinforcing layer may be disposed in areas overlapping the contact surfaces of the shoulder blocks.

[0082] 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.

[0083] In the above-described embodiment, slopes are formed on the groove walls of all blocks. However, for example, slopes may not be formed on at least one of the center block and the mediate block. Note that some blocks may not have sipes or slopes as long as the object of the present invention is not impaired. Also, two or more sipes may be formed in each block. In the above-described embodiment, by forming slopes on the groove walls, drainage is improved without increasing the number of sipes, thereby improving wet performance. However, it is possible to increase the number of sipes as long as the object of the present invention is not impaired. [Explanation of symbols]

[0084] 1 pneumatic tire, 2 reinforcing layer, 2a first region, 2b second region, 10 tread, 11 shoulder, 12 sidewall, 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, 31, 41, 51, 61, 71, 81 sipe, 32, 42, 52, 62, 72, 82 slope, 32a, 72a first region, 32b, 72b second region, 50, 60 shoulder block, 70, 80 mediate block, 90 raised portion, 100, 101 block group, CL tire equator, E ground contact edge, R1 Width direction center area, R2 width direction both side areas

Claims

1. A pneumatic tire having a designated main rotation direction, comprising: a tread; a carcass; a belt disposed between the tread and the carcass; and a reinforcing layer disposed between the tread and the belt so as to cover an outer peripheral surface of the belt, The tread is a plurality of center blocks formed in a tire circumferential direction in a central region of the tread in a width direction; a plurality of shoulder blocks formed in the tire circumferential direction in both widthwise side regions of the tread; a plurality of intermediate blocks formed in the tire circumferential direction between the center block and the shoulder block; and The shoulder blocks are formed with sipes including slopes that are inclined so that the groove width increases toward the ground contact surface, the reinforcing layer has a first region and a second region having a thickness greater than that of the first region, the second region is disposed in a range overlapping in the tire radial direction with the ground contact surface of the shoulder block, and extends outward in the tire width direction to positions beyond both ends of the belt in the width direction.

2. The pneumatic tire according to claim 1 , wherein the second region of the reinforcing layer overlaps with 50% or more of the contact surface of the shoulder block in the tire radial direction.

3. The pneumatic tire according to claim 1 , wherein the second region of the reinforcing layer overlaps at least the ground contact end of the shoulder block in the tire radial direction.

4. A pneumatic tire described in any one of claims 1 to 3, wherein the inclined surface is formed only on the groove wall located on the rear side of the sipe in the main rotation direction of the tire.

5. The center block includes a first center block and a second center block, the shoulder blocks include first and second shoulder blocks; The mediate block includes a first mediate block and a second mediate block, On one side of the tread in the width direction, the first center block, the first intermediate block, and the first shoulder block are arranged in succession in this order from the tire equator side to form a first block group, a second block group is formed on the other side of the tread in the width direction, by arranging the second center block, the second intermediate block, and the second shoulder block in this order from the tire equator side, so that the second center block, the second intermediate block, and the second shoulder block are connected to each other; Each of the first and second block groups is defined by a main groove and has a curved shape in a plan view that is convex rearward in a main rotation direction of the tire, the tread has a circumferential groove that is connected to the main groove and separates the shoulder blocks and the intermediate blocks, The pneumatic tire according to any one of claims 1 to 4, wherein the circumferential grooves are formed linearly along the tire circumferential direction without bending at intersections with the main grooves.

6. A second sipe including a second slope inclined so that the groove width widens toward the ground contact surface is formed on the mediate block, The pneumatic tire according to claim 5 , wherein the inclined surface is formed in a portion adjacent to the circumferential groove and faces the second inclined surface of the mediate block across the circumferential groove.

7. A pneumatic tire as described in claim 6, wherein the second inclined surface is formed only on the groove wall located on the rear side of the second sipe in the main rotation direction of the tire.

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