Tire

Abstract

The present invention improves heat generation resistance performance. A tread section includes: a center block 31A partitioned by vertical grooves 21, 22 and a center lateral groove 41; a shoulder block 32A that is partitioned by a shoulder lateral groove 51 and a vertical groove on the outermost side in the tire width direction and has a buttress section 15B on the outer side in the tire width direction of a ground contact end T; tread-side dimples 61 that open in a polygonal shape at least on the tread surface 15A of the center block and have a cross-sectional shape along the tire radial direction formed so as to become smaller from the opening toward a groove bottom; and buttress section-side dimples 63 that open in a polygonal shape on the surface of the buttress section and have a cross-sectional shape along the tire radial direction formed so as to become smaller from the opening toward the groove bottom. The opening area of the tread-side dimples of the center block is 10 (%) or more and 125 (%) or less with respect to the opening area of the buttress section-side dimples of a buttress section (buttress block 32Aa) of the shoulder block.

Description

tire

[0001] The present invention relates to tires.

[0002] For example, Patent Document 1 describes a tire having a row of blocks in the shoulder region of the tread, with each block having at least one vertical hole extending from the tread surface in the tire radial direction and at least one horizontal hole extending from the outer surface in the tire axial direction.

[0003] Japanese Patent Application Laid-Open No. 2004-009886

[0004] For example, in heavy-duty tires such as OTR (Off The Road), heat separation is likely to occur due to heat generation in the tread portion under severe operating conditions of load and running speed, so it is desirable to ensure heat resistance.

[0005] An object of the present invention is to provide a tire that can improve heat resistance.

[0006] In order to achieve the above object, a tire according to one aspect of the present invention has a tread portion including two or more longitudinal grooves extending continuously in the tire circumferential direction, a plurality of center lateral grooves extending in the tire width direction and communicating with each of the longitudinal grooves and arranged in the tire circumferential direction, a plurality of shoulder lateral grooves extending in the tire width direction outward of each of the two outermost longitudinal grooves in the tire width direction, communicating with each of the longitudinal grooves and passing through the ground contact edge, and arranged in the tire circumferential direction, a center block defined by the longitudinal grooves and the center lateral groove, and a center block defined by the outermost longitudinal groove and the shoulder lateral groove in the tire width direction. The tire includes shoulder blocks having buttress portions on the outer side of the contact edge in the tire width direction; tread-side dimples that open in a polygonal shape on the tread surface of at least the center block of the center block and the shoulder block, with a cross-sectional shape along the tire radial direction that tapers from the opening toward the groove bottom; and buttress-side dimples that open in a polygonal shape on the surface of the buttress portion, with a cross-sectional shape along the tire radial direction that tapers from the opening toward the groove bottom, wherein the opening area of ​​the tread-side dimples is 10% or more and 125% or less of the opening area of ​​the buttress-side dimples.

[0007] According to this invention, heat resistance can be improved.

[0008] FIG. 1 is a development view of the tread of a pneumatic tire according to an embodiment. FIG. 2 is a partially enlarged view of a meridian cross section of the pneumatic tire according to an embodiment. FIG. 3 is a plan view showing example dimples of the pneumatic tire according to an embodiment. FIG. 4 is a plan view showing example dimples of the pneumatic tire according to an embodiment. FIG. 5 is a plan view showing example dimples of the pneumatic tire according to an embodiment. FIG. 6 is a plan view showing example dimples of the pneumatic tire according to an embodiment. FIG. 7 is a plan view showing example dimples of the pneumatic tire according to an embodiment. FIG. 8 is a plan view showing example dimples of the pneumatic tire according to an embodiment. FIG. 9 is a plan view showing example dimples of the pneumatic tire according to an embodiment. FIG. 10 is a plan view showing example dimples of the pneumatic tire according to an embodiment. FIG. 11 is an explanatory diagram defining the center (center of gravity) of a block. FIG. 12 is a table showing results of a performance test of the pneumatic tire according to an embodiment. FIG. 13 is a table showing results of a performance test of the pneumatic tire according to an embodiment. FIG. 14 is a table showing results of a performance test of the pneumatic tire according to an embodiment. Fig. 15 is a table showing the results of a performance test of a pneumatic tire according to an embodiment. Fig. 16 is a table showing the results of a performance test of a pneumatic tire according to an embodiment. Fig. 17 is a table showing the results of a performance test of a pneumatic tire according to an embodiment. Fig. 18 is a table showing the results of a performance test of a pneumatic tire according to an embodiment. Fig. 19 is a table showing the results of a performance test of a pneumatic tire according to an embodiment. Fig. 20 is a table showing the results of a performance test of a pneumatic tire according to an embodiment. Fig. 21 is a table showing the results of a performance test of a pneumatic tire according to an embodiment.

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to these embodiments. Furthermore, the components of these embodiments include those that can be substituted and are obvious substitutes while maintaining the identity of the invention. Furthermore, the multiple modifications described in these embodiments can be arbitrarily combined within the scope obvious to those skilled in the art.

[0010] In the following description, the tire radial direction refers to a direction perpendicular to the tire rotation axis (not shown), which is the rotation axis of the pneumatic tire 1 of this embodiment. The tire radially inner side refers to the side toward the tire rotation axis in the tire radial direction, and the tire radially outer side refers to the side away from the tire rotation axis in the tire radial direction. The tire circumferential direction refers to the direction around the tire rotation axis as the central axis. The tire width direction refers to a direction parallel to the tire rotation axis. The tire widthwise inner side refers to the side toward the tire equatorial plane (tire equator line) CL in the tire width direction, and the tire widthwise outer side refers to the side away from the tire equatorial plane CL in the tire width direction. The tire equatorial plane CL is a plane that is perpendicular to the tire rotation axis and passes through the center of the tire width of the pneumatic tire 1. The tire equatorial plane CL coincides in position in the tire width direction with the tire widthwise centerline, which is the center position of the pneumatic tire 1 in the tire width direction. The tire equator line refers to a line that is on the tire equatorial plane CL and runs along the tire circumferential direction of the pneumatic tire 1. Further, a cross section in the tire meridian direction (meridian cross section) refers to a cross section of the tire cut along a plane including the tire rotation axis.

[0011] 1 is a development view of a tread of a pneumatic tire according to an embodiment. In this embodiment, a heavy-duty pneumatic radial tire to be mounted on heavy-duty vehicles such as trucks and buses, particularly heavy-duty vehicles for construction or industrial use, will be described as an example.

[0012] The pneumatic tire 1 is formed symmetrically in the tire width direction with respect to the tire equatorial plane CL. Fig. 2 is an enlarged meridian cross-sectional view of the pneumatic tire 1, showing a cross section along a center lateral groove 41 and a shoulder lateral groove 51, which will be described later.

[0013] As shown in FIG. 2 , the pneumatic tire 1 of the embodiment has an annular structure centered on the tire rotation axis, and includes a pair of bead cores (not shown), a pair of bead fillers (not shown), a carcass layer 13, a belt layer 14, a tread rubber 15, a pair of sidewall rubbers 16, and a pair of rim cushion rubbers (not shown).

[0014] Although not shown in the figure, the pair of bead cores are made by winding one or more steel bead wires in a circular and multiple manner, and are embedded in the bead portions to form the cores of the bead portions on both sides in the tire width direction.

[0015] Although not shown in the drawings, the pair of bead fillers are made up of a lower filler and an upper filler, and are respectively disposed on the outer periphery of the pair of bead cores in the tire radial direction to reinforce the bead portion.

[0016] The carcass layer 13 has a single-layer structure consisting of one carcass ply or a multi-layer structure consisting of multiple carcass plies stacked together. In the pneumatic tire 1 of the embodiment, the carcass layer 13 is shown as a single carcass ply. The carcass layer 13 is toroidally laid between the bead cores to form the tire framework. Both ends of the carcass layer 13 are wound back and secured to the outside in the tire width direction so as to enclose the bead cores and bead fillers. The carcass ply of the carcass layer 13 is formed by coating multiple steel carcass cords with coating rubber and rolling them. The carcass ply has a cord angle (defined as the inclination angle of the carcass cords in the longitudinal direction relative to the tire circumferential direction) of 80 degrees or more and 90 degrees or less in absolute value for a radial tire, or 20 degrees or more and 45 degrees or less in absolute value for a bias tire.

[0017] The belt layer 14, also referred to as a belt member, is formed by laminating multiple belt plies (also referred to as belts) 141-146 and is disposed around the outer periphery of the carcass layer 13. These belt plies 141-146 are combined with belts of various configurations, such as a 0-degree belt or a pair of cross belts. In the pneumatic tire 1 of the embodiment, the belt layer 14 is preferably formed by laminating five or more belt plies so as to be suitable for use in heavy-duty vehicles for construction and industrial use. The belt plies are formed by coating multiple steel belt cords (also referred to as wire rods) with coating rubber and rolling them. The pair of cross belts are formed by coating multiple steel belt cords with coating rubber and rolling them, and have cord angles of opposite signs. The belt cords are laminated so that their longitudinal directions cross each other, forming a so-called cross-ply structure.

[0018] The tread rubber 15 is disposed on the outer periphery of the carcass layer 13 and the belt layer 14 in the tire radial direction to form a tread portion of the pneumatic tire 1. The tread rubber 15 forms a tread surface (also simply referred to as the tread surface) 15A on the outer surface of the tread portion that comes into contact with the road surface during running. The outer ends (corners) of the tread surface 15A in the tire width direction form ground contact edges T. The tread rubber 15 also has buttress portions 15B in the tread portion that do not come into contact with the road surface during running, on side portions on both outer sides in the tire width direction than the ground contact edges T of the tread surface 15A. The buttress portions 15B are provided in the tread rubber 15 from the ground contact edges T to the outer side in the tire width direction and the inner side in the tire radial direction, up to the sidewall rubber 16.

[0019] The pair of sidewall rubbers 16 are respectively arranged on the outer sides of the carcass layer 13 in the tire width direction, and constitute sidewall portions on both sides of the pneumatic tire 1 in the tire width direction, on the inner side of the buttress portion 15B in the tire radial direction.

[0020] Although not shown in the drawings, the pair of rim cushion rubbers extend from the radially inner side of each bead core and the turned-up portion of the carcass layer 13 to the widthwise outer side of the tire, and form the rim fitting surface of the bead portion.

[0021] The pneumatic tire 1 of the embodiment has a tread pattern in the tread portion (tread surface 15A and buttress portion 15B) as shown in Fig. 2. Here, each dimension of the tread pattern is measured in an unloaded state with the tire mounted on a specified rim and inflated to a specified internal pressure.

[0022] "Specified rim" refers to the "standard rim" specified by JATMA, the "design rim" specified by TRA, or the "measuring rim" specified by ETRTO. Also, "specified internal pressure" refers to the "maximum air pressure" specified by JATMA, the maximum value of the "tire load limits at various cold inflation pressures" specified by TRA, or the "inflation pressures" specified by ETRTO. Also, "specified load" refers to the "maximum load capacity" specified by JATMA, the maximum value of the "tire load limits at various cold inflation pressures" specified by TRA, or the "load capacity" specified by ETRTO.

[0023] The groove width (opening width) is measured as the maximum distance between opposing groove walls of a groove opening on the surface of the tread surface 15A or buttress portion 15B when the tire is mounted on a specified rim, inflated to a specified internal pressure, and in an unloaded state. In a configuration in which the groove opening has a notch or chamfer, the groove width (opening width) is measured using the intersection of an extension of the tread surface and an extension of the groove wall as the endpoint in a cross section parallel to the tire width direction and the tire radial direction.

[0024] The groove depth is measured as the maximum distance from the surface of the tread surface 15A or the buttress portion 15B to the groove bottom when the tire is mounted on a specified rim, inflated to a specified internal pressure, and under no load. In addition, if the groove bottom has partial unevenness or sipes, the groove depth is measured excluding these.

[0025] As shown in Figure 1, the pneumatic tire 1 of the embodiment has at least two longitudinal grooves 21, 22 and lateral grooves 41, 51 communicating with the respective longitudinal grooves on the tread surface 15A. Also, as shown in Figures 1 and 2, the pneumatic tire 1 of the embodiment has dimples 61, 62 on the tread surface 15A. Also, as shown in Figures 1 and 2, the pneumatic tire 1 of the embodiment has a dimple 63 on the surface of the buttress portion 15B.

[0026] The longitudinal grooves 21 are grooves that extend continuously along the tire circumferential direction. In the embodiment, the longitudinal grooves 21 are also referred to as circumferential grooves. A pair of longitudinal grooves 21 is arranged on the tread surface 15A, one on each side at the outermost positions in the tire width direction, with the tire equatorial plane CL as the boundary. The area between this pair of longitudinal grooves 21 is referred to as a center region CE, the area from each longitudinal groove 21 in the tire width direction outward to the ground contact edge T is referred to as a shoulder region SE, and the area outward in the tire width direction of the ground contact edge T is referred to as a buttress region BE. In the embodiment, when there are two longitudinal grooves 21, these longitudinal grooves 21 are included.

[0027] The longitudinal groove 21 has linear inclined portions 21a. The inclined portions 21a are arranged at an angle relative to the tire circumferential direction. The inclined portions 21a have angles with opposite signs relative to the tire circumferential direction, and these are arranged alternately and continuously in the tire circumferential direction and connected by bent portions 21b. Therefore, the longitudinal groove 21 extends continuously along the tire circumferential direction and is formed in a zigzag shape. The longitudinal groove 21 may also be formed in a linear shape that continues along the tire circumferential direction.

[0028] The longitudinal groove 22 is a groove that extends continuously along the tire circumferential direction. In the embodiment, the longitudinal groove 22 is also referred to as a circumferential groove. In the embodiment, one longitudinal groove 22 is arranged along the tire equatorial plane CL.

[0029] The longitudinal grooves 22 have linear inclined portions 22a. The inclined portions 22a are arranged at an angle relative to the tire circumferential direction. The inclined portions 22a have angles with opposite signs relative to the tire circumferential direction, and these are arranged alternately in succession in the tire circumferential direction and connected by bent portions 22b. Therefore, the longitudinal grooves 22 extend continuously along the tire circumferential direction in a zigzag shape. The longitudinal grooves 21 and 22 are arranged such that the bent portion 21b facing inward in the tire width direction of the adjacent longitudinal groove 21 on one side of the tire width direction is located closest to one bent portion 22b facing inward in the tire width direction of the adjacent longitudinal groove 21 on the other side of the tire width direction, and the bent portion 21b facing inward in the tire width direction of the adjacent longitudinal groove 21 on the other side of the tire width direction is located closest to one bent portion 22b facing inward in the tire width direction of the adjacent longitudinal groove 21 on the other side of the tire width direction. The longitudinal grooves 22 may also be formed in a continuous linear shape along the tire circumferential direction.

[0030] In the pneumatic tire 1 of the embodiment, two land portions (hereinafter referred to as center land portions) 31 that are adjacent in the tire width direction along the tire circumferential direction are defined in the center region CE between the pair of longitudinal grooves 21 by two longitudinal grooves 21 and one longitudinal groove 22. In the pneumatic tire 1 of the embodiment, one land portion (hereinafter referred to as shoulder land portion) 32 that is aligned along the tire circumferential direction is defined in each shoulder region SE on the outer side in the tire width direction of each longitudinal groove 21.

[0031] When there are two longitudinal grooves, one center land portion 31 is defined between a pair of adjacent longitudinal grooves 21 in the tire width direction. When there are more than three longitudinal grooves, two or more longitudinal grooves 22 are arranged between the outermost longitudinal grooves 21 in the tire width direction, including a longitudinal groove 22 arranged off the tire equatorial plane CL. When there are more than three longitudinal grooves, three or more center land portions 31 are defined in the center region CE.

[0032] The lateral grooves 41, also referred to as center lateral grooves, are disposed in a center land portion 31 defined in a center region CE between a pair of longitudinal grooves 21. In this embodiment, the lateral grooves 41 extend linearly or curvedly along the tire width direction, with one end communicating with the longitudinal groove 21 and the other end communicating with the longitudinal groove 22. A plurality of lateral grooves 41 are disposed side by side in the tire circumferential direction. One end of each lateral groove 41 communicates with a bent portion 21b of the longitudinal groove 21 facing inward in the tire width direction, and the other end communicates with a bent portion 22b of the longitudinal groove 22 closest to the bent portion 21b. Therefore, the center land portion 31 is defined into a plurality of center blocks 31A arranged side by side in the tire circumferential direction by the longitudinal grooves 21, 22 adjacent in the tire width direction and the plurality of lateral grooves 41. The tread surface 15A of each center block 31A here is formed in a hexagonal shape.

[0033] In addition, when there are two longitudinal grooves, the lateral grooves 41 are arranged in one center land portion 31 between a pair of longitudinal grooves 21 adjacent in the tire width direction, with their ends communicating with the respective longitudinal grooves 21. When there are two longitudinal grooves, the ends of the lateral grooves 41 are connected to the bent portions 21b closest to each of the adjacent longitudinal grooves 21 in the tire width direction. Furthermore, when there are more than three longitudinal grooves, the lateral grooves 41 are also arranged between adjacent longitudinal grooves 22 in the tire width direction, with their ends communicating with the respective longitudinal grooves 22. In this case, the lateral grooves 41 are connected to the bent portions 22b closest to each of the adjacent longitudinal grooves 22 in the tire width direction and to which the lateral grooves 41 of other center land portions 31 do not communicate. Therefore, when there are more than three longitudinal grooves, the center land portion 31 between each of the longitudinal grooves 22 is partitioned into center blocks 31A.

[0034] The lateral grooves 51, also known as shoulder lateral grooves, are arranged in the shoulder land portion 32 defined in the shoulder region SE on the tire widthwise outer side of each longitudinal groove 21. The lateral grooves 51 have the same groove width and groove depth as the lateral grooves 41. The lateral grooves 51 extend linearly or curvedly along the tire width direction, with one end communicating with the longitudinal groove 21 and the other end extending beyond the ground contact edge T to the buttress region BE and opening onto the surface of the buttress portion 15B. Multiple lateral grooves 51 are arranged side by side in the tire circumferential direction. One end of each lateral groove 51 communicates with the bent portion 21b of the longitudinal groove 21 facing outward in the tire width direction. Therefore, the shoulder land portion 32 is defined by the longitudinal grooves 21 and the multiple lateral grooves 51 into multiple shoulder blocks 32A arranged side by side in the tire circumferential direction. The tread surface 15A of each shoulder block 32A here is formed into a pentagonal shape.

[0035] Furthermore, the lateral grooves 51 extend beyond the ground contact edge T to the buttress region BE and open onto the surface of the buttress portion 15B, so that the shoulder block 32A has the buttress portion 15B and is partitioned into multiple buttress blocks 32Aa arranged circumferentially of the tire.

[0036] The dimples 61 are recesses formed in the tread surface 15A of the center blocks 31A defined in the center region CE. These are also called tread-side dimples and are hereinafter referred to as center dimples. Preferably, one center dimple 61 is disposed in each center block 31A. The center dimples 61 may be disposed in all center blocks 31A. Alternatively, for example, the center dimples 61 may be disposed in all center blocks 31A of a specific center land portion 31, or in specific center blocks 31A of a specific center land portion 31. As shown in FIG. 1 , the center dimple 61 has an opening 61a (see FIG. 2 ) formed in a polygonal shape (shown as a triangular shape with arcuate corners in FIG. 1 ) on the tread surface 15A. The center dimple 61 may have a polygonal shape that continues from the opening 61a to the groove bottom 61b, or may cease to have a polygonal shape midway to the groove bottom 61b. 2, the center dimple 61 is formed so that, in the tire radial cross section, it tapers from an opening 61a that opens onto the tread surface 15A toward the groove bottom 61b. The center dimple 61 is formed so that its depth D1 is 25% or more of the groove depth D of the shoulder lateral groove 51. The center dimple 61 is formed so that the opening area of ​​the opening 61a (or the total opening area if there are multiple center dimples) is more than 6% and less than 20% of the block surface area of ​​the tread surface 15A of the single center block 31A in which the center dimple 61 is formed.

[0037] The dimples 62 are recesses formed in the tread surface 15A of the shoulder blocks 32A defined in the shoulder region SE. These dimples are also called tread-side dimples and are hereinafter referred to as "shoulder dimples." Preferably, one shoulder dimple 62 is disposed in each shoulder block 32A. The shoulder dimples 62 may be disposed in all shoulder blocks 32A. However, for example, the shoulder dimples 62 may be disposed in all shoulder blocks 32A of a given shoulder land portion 32, or in a given shoulder block 32A of a given shoulder land portion 32. As shown in FIG. 1 , the shoulder dimple 62 has an opening 62a (see FIG. 2 ) formed in a polygonal shape (shown as a square with arcuate corners in FIG. 1 ) on the tread surface 15A. The shoulder dimple 62 may have a polygonal shape that continues from the opening 62a to the groove bottom 62b, or it may cease to be polygonal midway to the groove bottom 62b. 2, the shoulder dimples 62 are formed so that, in the tire radial cross section, they taper from their openings 62a that open to the tread surface 15A toward the groove bottoms 62b. The shoulder dimples 62 are formed so that their depths D2 are 25% or more of the groove depth D of the shoulder lateral grooves 51. The opening areas of the openings 62a of the shoulder dimples 62 (or the total opening area if there are multiple dimples) are greater than 6% and less than 20% of the block surface area of ​​the tread surface 15A of the single shoulder block 32A in which the dimples are formed. The pneumatic tire 1 of this embodiment may also have a configuration in which the shoulder dimples 62 are not provided.

[0038] The dimples 63 are recesses formed in the surface of the buttress portion 15B in the buttress blocks 32Aa defined in the buttress region BE. They are also called buttress-side dimples and will be referred to hereinafter as buttress dimples. Preferably, one buttress dimple 63 is provided in each buttress block 32Aa. The buttress dimples 63 may be provided in all buttress blocks 32Aa, but for example, they may be provided in all buttress blocks 32Aa in a specific buttress region BE, or in a specific buttress block 32Aa in a specific buttress region BE. As shown in FIG. 1, the buttress dimple 63 has an opening 63a (see FIG. 2) formed in a polygonal shape on the surface of the buttress portion 15B. The buttress dimple 63 may have a continuous polygonal shape from the opening 63a to the groove bottom 63b, or it may not have a polygonal shape partway to the groove bottom 63b. As shown in FIG. 2, the buttress dimple 63 is formed so that, in a cross section in the tire radial direction, it narrows from an opening 63a that opens on the surface of the buttress portion 15B toward a groove bottom 63b.

[0039] The shapes of the openings 61a, 62a, 63a of the center dimple 61, shoulder dimples 62, and buttress dimples 63 will be described below with reference to FIGS.

[0040] The center dimple 61, shoulder dimples 62, and buttress dimples 63 are collectively referred to as dimples 61, 62, and 63, and these dimples 61, 62, and 63 have a primary shape of a triangle or a square with arcuate corners, as shown in Figure 1, or a pentagon or hexagon, although not explicitly shown. Also, as shown in Figures 3 to 10, the dimples 61 and 62 may be formed as concave polygons having at least one inward interior angle 6b in addition to an outward interior angle 6a. The outward interior angle 6a has an angle θ of less than 180 degrees, and the inward interior angle 6b has an angle θ of greater than 180 degrees.

[0041] 3 are formed in a concave polygonal shape including three outward interior angles 6a and three inward interior angles 6b. The outward interior angles 6a and the inward interior angles 6b are alternately arranged in the circumferential direction.

[0042] The dimples 61, 62, and 63 shown in Figure 4 have a shape in which the inward interior angle 6b is formed into a rounded chamfer 6b', as compared to the dimples 61, 62, and 63 shown in Figure 3. The angle θ in this shape is represented by the angle formed by extending the two sides on either side of the inward interior angle 6b.

[0043] 5 are formed in the shape of a concave polygon including five outward interior angles 6a and one inward interior angle 6b. The one inward interior angle 6b is located between two outward interior angles 6a.

[0044] 6 are formed in the shape of a concave polygon including four outward interior angles 6a and four inward interior angles 6b. The outward interior angles 6a and the inward interior angles 6b are alternately arranged in the circumferential direction.

[0045] 7 are formed in the shape of a concave polygon including five outward-facing interior angles 6a and five inward-facing interior angles 6b. The outward-facing interior angles 6a and the inward-facing interior angles 6b are alternately arranged in the circumferential direction.

[0046] 8 are formed in a concave polygonal shape that includes many outward-facing interior angles 6a and many inward-facing interior angles 6b. The outward-facing interior angles 6a and the inward-facing interior angles 6b are alternately arranged in the circumferential direction.

[0047] 9 are formed in a concave polygonal shape including four outward interior angles 6 a and two inward interior angles 6 b. Each inward interior angle 6 b is located between two outward interior angles 6 a and faces each other.

[0048] 10, the dimples 61, 62, and 63 are formed in a polygonal shape with a circular outer diameter and eight outward-facing interior angles 6a and four inward-facing interior angles 6b. Each inward-facing interior angle 6b is located between two outward-facing interior angles 6a.

[0049] The above-described dimples 61, 62, and 63 are disposed at the center of the tread surface 15A of the blocks 31A and 32A or at the center of the surface of the block 32Aa. The centers of the blocks 31A, 32A, and 32Aa refer to the centers of gravity of the tread surface 15A of the blocks 31A and 32A or the center of gravity of the surface of the block 32Aa, which are calculated using the center-of-gravity calculation formulas shown in FIG. 11 and the following formulas 1 and 2.

[0050]

[0051]

[0052] The pneumatic tire 1 of the above-described embodiment is characterized by having, in the tread portion, two or more longitudinal grooves 21, 22 extending continuously along the tire circumferential direction, a plurality of center lateral grooves 41 extending along the tire width direction and communicating between the respective longitudinal grooves 21, 22 and arranged in the tire circumferential direction, a plurality of shoulder lateral grooves 51 extending along the tire width direction outward of each of the two outermost longitudinal grooves 21 in the tire width direction, communicating with each of the longitudinal grooves 21 and passing through the ground contact edge T and arranged in the tire circumferential direction, a center block 31A defined by the longitudinal grooves 21, 22 and the center lateral groove 41, a shoulder block 32A defined by the outermost longitudinal groove 21 in the tire width direction and the shoulder lateral groove 51 and having a buttress portion on the tire width direction outer side of the ground contact edge T, and a center block 31A defined by the center lateral grooves 41. The tread-side dimples 61, 62 open in a polygonal shape on the tread surface 15A of at least the center block 31A of the turbo block 31A and the shoulder block 32A, and have a cross-sectional shape along the tire radial direction that decreases from opening 61a, 62a to groove bottom 61b, 62b, and a buttress-side dimple 63 open in a polygonal shape on the surface of the buttress portion 15B, and have a cross-sectional shape along the tire radial direction that decreases from opening 63a to groove bottom 63b, and the opening area of ​​the tread-side dimples 61, 62 of a single block 31A, 32A is 10% or more and 125% or less of the opening area of ​​the buttress-side dimple 63 of the buttress portion 15B (buttress block 32Aa) of a single shoulder block 32A.

[0053] In this pneumatic tire 1, by arranging tread-side dimples 61, 62 forming polygonal openings 61a, 62a on the tread surfaces 15A of the blocks 31A, 32A, the opening area can be increased without increasing the opening range relative to the block tread area, thereby achieving sufficient heat dissipation and improved heat resistance. Moreover, in this pneumatic tire 1, by providing buttress-side dimples 63 on the surface of the buttress portion 15B, further heat dissipation can be achieved and heat resistance can be further improved. Moreover, in this pneumatic tire 1, the cross-sectional shape of the dimple 61 along the tire radial direction is formed to become smaller from the opening 61a toward the groove bottom 61b, so that appropriate block rigidity can be maintained and heat generation can be suppressed even when the rubber volume of the blocks 31A, 32A decreases with wear.

[0054] In addition, in the pneumatic tire 1 of the embodiment, the opening area of ​​the tread-side dimples 61, 62 of a single block 31A, 32A is 10% to 50% of the opening area of ​​the buttress-side dimple 63 of the buttress portion 15B (buttress block 32Aa) of a single shoulder block 32A.

[0055] In this pneumatic tire 1, by setting the opening area of ​​the tread-side dimples 61, 62 on the tread surface 15A to between 10% and 50% of the opening area of ​​the buttress-side dimples 63, an effective heat generation effect can be achieved while suppressing a decrease in rigidity of the center and shoulder blocks 31A, 32A. In this pneumatic tire 1, if the opening area is less than 10%, the buttress-side dimples 63 will be large, increasing vibration of the shoulder blocks 32A and worsening heat generation. If the opening area exceeds 50%, the heat dissipation ability of the buttress portion 15B will be relatively reduced, tending to reduce heat generation resistance in the shoulder blocks 32A. Therefore, the opening area is set to between 10% and 50%. In this pneumatic tire 1, a ratio of between 20% and 40% is more preferable to improve heat generation properties of the shoulder blocks 32A.

[0056] Furthermore, in the pneumatic tire 1 of the embodiment, the relationship between the opening areas of the tread-side dimples 61, 62 and the buttress-side dimples 63 is 10% or more and 50% or less, and the opening area of ​​the buttress-side dimples of the buttress portion 15B (buttress block 32Aa) of a single shoulder block 32A is 10% or more and 55% or less of the tread area of ​​the single shoulder block 32A. Note that in the pneumatic tire 1 of the embodiment, if a shoulder dimple 62 is present on the tread surface 15A of the shoulder block 32A, the opening area of ​​the shoulder dimple 62 is excluded.

[0057] In this pneumatic tire 1, if the buttress-side dimples 63 account for less than 10% of the tread area of ​​the shoulder blocks 32A, the heat dissipation effect is poor, and if it exceeds 55%, the buttress portion 15B tends to bend too much and the strength tends to be insufficient, so the ratio is set to 10% to 55%. In this pneumatic tire 1, to improve the heat dissipation effect and to counteract the lack of strength of the shoulder blocks 32A, it is more preferable that the ratio be set to 20% to 45%.

[0058] In addition, in the pneumatic tire 1 of the embodiment, the opening area of ​​the tread-side dimples 61, 62 of a single block 31A, 32A is 51% or more and 125% or less of the opening area of ​​the buttress-portion-side dimple 63 of the buttress portion 15B (buttress block 32Aa) of a single shoulder block 32A.

[0059] In this pneumatic tire 1, by setting the opening area of ​​the tread-side dimples 61, 62 on the tread surface 15A to be 51% or more and 125% or less of the opening area of ​​the buttress-side dimples 63, the rigidity of the shoulder blocks 32A can be ensured, the burden on the center blocks 31A can be reduced, and heat resistance can be improved without impairing uneven wear resistance. In this pneumatic tire 1, if the opening area is less than 51%, the buttress-side dimples 63 will be large, reducing the rigidity of the shoulder blocks 32A and tending to deteriorate uneven wear resistance. If the opening area exceeds 125%, the buttress-side dimples 63 will be small, tending to reduce heat dissipation effectiveness. Therefore, the opening area of ​​this pneumatic tire 1 is set to be 51% or more and 125% or less. To improve uneven wear resistance, it is more preferable for the pneumatic tire 1 to be 80% or more and 100% or less.

[0060] Furthermore, in the pneumatic tire 1 of the embodiment, the relationship between the opening areas of the tread-side dimples 61, 62 and the buttress-side dimples 63 is 51% or more and 125% or less, and the opening area of ​​the buttress-side dimples of the buttress portion 15B (buttress block 32Aa) of a single shoulder block 32A is 5% or more and 20% or less of the tread area of ​​the single shoulder block 32A. Note that in the pneumatic tire 1 of the embodiment, if a shoulder dimple 62 is present on the tread surface 15A of the shoulder block 32A, the opening area of ​​the shoulder dimple 62 is excluded.

[0061] In this pneumatic tire 1, if the buttress portion-side dimples 63 account for less than 5% of the tread area of ​​the shoulder blocks 32A, the heat dissipation effect is poor, and if it exceeds 20%, the rigidity of the buttress portion 15B decreases and uneven wear resistance tends to deteriorate, so the ratio is set to between 5% and 20%. In order to improve the heat dissipation effect and uneven wear resistance of this pneumatic tire 1, it is more preferable that the ratio be between 10% and 15%.

[0062] In the pneumatic tire 1 of the embodiment, the depth D3 of the buttress-side dimples 63 is 10% to 55% of the depths D1, D2 of the tread-side dimples 61, 62.

[0063] This pneumatic tire 1 can provide effective heat dissipation while suppressing a decrease in block rigidity within the above range. In this pneumatic tire 1, if the ratio is less than 10%, the heat dissipation effect of the center blocks 31A and shoulder blocks 32A is weak. If the ratio exceeds 55%, the block rigidity of the shoulder blocks 32A is low, and heat generation tends to increase due to block movement when in contact with the ground. Therefore, the ratio is set to 10% or more and 55% or less. To ensure good heat dissipation, this pneumatic tire 1 preferably has a ratio of 30% or more and 50% or less.

[0064] In the pneumatic tire 1 of the embodiment, the depths D1, D2 of the tread-side dimples 61, 62 are 25% or more of the groove depth D of the shoulder lateral groove 51.

[0065] In this pneumatic tire 1, if the depths D1 and D2 of the tread-side dimples 61 and 62 are less than 25% of the groove depth D of the shoulder lateral groove 51, the tire tends to be unable to exhibit sufficient heat dissipation, so the depths are set to 25% or more. However, in this pneumatic tire 1, if the depths D1 and D2 of the dimples 61 and 62 exceed 75% of the groove depth D of the shoulder lateral groove 51, the tire tends to have reduced block rigidity, so a depth of 75% or less is desirable.

[0066] In the pneumatic tire 1 of the embodiment, the opening area of ​​the tread-side dimples 61, 62 is greater than 6% and smaller than 20% of the block tread area of ​​the blocks 31A, 32A on which they are provided.

[0067] According to this pneumatic tire 1, if the opening area of ​​the tread side dimples 61, 62 is 6% or less of the tread area of ​​the blocks 31A, 32A, it becomes difficult for heat to be dissipated effectively from the tread side dimples 61, 62, and if it is 20% or more, the rigidity of the blocks 31A, 32A will be insufficient and the impact of worsening heat generation will tend to be greater than the heat dissipation effect, so the opening area is set to be greater than 6% and less than 20%.

[0068] In the pneumatic tire 1 of the embodiment, the tread-side dimples 62 are also provided on the tread surface 15A of the shoulder block 32A.

[0069] In this pneumatic tire 1, the center block 31A has the highest heat generation property, so providing tread side dimples 61 is highly effective, but by also providing tread side dimples 62 on the tread surface 15A of the shoulder block 32A, the heat resistance performance of the entire tread portion can be uniformly improved.

[0070] In addition, in the pneumatic tire 1 of the embodiment, the opening area of ​​the tread side dimples 62 provided on the shoulder blocks 32A is 60% or more and 100% or less of the opening area of ​​the tread side dimples 61 provided on the center blocks 31A.

[0071] In this pneumatic tire 1, the shoulder blocks 32A have buttress portions 15B and include buttress-side dimples 63, so it is desirable to provide tread-side dimples 62 that are smaller than the tread-side dimples 61 of the center blocks 31A. Furthermore, in the pneumatic tire 1, if the tread-side dimples 62 are less than 60%, the heat dissipation effect of the tread-side dimples 62 is insufficient, and if the tread-side dimples are greater than 100%, the rigidity of the shoulder blocks 32A tends to decrease. For this pneumatic tire 1, a tread-side dimple ratio of 70% to 90% is preferred to ensure good heat dissipation and rigidity.

[0072] Furthermore, the pneumatic tire 1 of the embodiment has five or more belt plies (141 to 146) arranged on the radially inner side of the tread portion, and is used for heavy-duty construction or industrial vehicles.

[0073] In the present embodiment, as described above, the pneumatic tire 1 has been described as an example of a tire. The pneumatic tire 1 can be filled with air, an inert gas such as nitrogen, or other gases. However, the tread pattern configuration of the pneumatic tire 1 described in the present embodiment can be applied to other tires as desired within the scope of what is obvious to those skilled in the art. Examples of other tires include airless tires and solid tires.

[0074] 12 to 21 are tables showing the results of performance tests of pneumatic tires according to the embodiment. Performance evaluation tests conducted on a conventional pneumatic tire and an example pneumatic tire according to the embodiment will be described below. The performance evaluation tests were conducted on heat resistance and uneven wear resistance.

[0075] The heat resistance evaluation test involves mounting a 2400R35 pneumatic tire (test tire) on a specified rim, inflating it to a specified internal pressure, and applying 85% of the specified load. An indoor drum test is then conducted at a test speed of 10 km / h for 24 hours, and the temperature of the tread portion is measured. Based on the measurement results, an index evaluation is performed, with the conventional example being used as the reference (100). The higher the evaluation value, the better.

[0076] The evaluation test for uneven wear resistance is performed by mounting a 2400R35 pneumatic tire (test tire) on a specified rim, inflating it to the specified internal pressure, and mounting it on a dump truck for construction machinery. The tire is then driven off-road for 3,000 hours at speeds of 10 to 25 km / h, measuring the amount of wear on the tread surface at the center and shoulder, and calculating the amount of center wear / shoulder wear. Evaluation is then performed based on the results of this calculation. The closer the deviation value is to 1.0, the better the evaluation.

[0077] The conventional pneumatic tire has two zigzag longitudinal grooves (longitudinal groove 21), one longitudinal groove on the tire equatorial plane (longitudinal groove 22), lateral grooves in the center region and lateral grooves in the shoulder regions, a center dimple, and a buttress dimple, but does not satisfy the specified range.

[0078] The pneumatic tire of the example satisfies the specified range based on the tread pattern shown in FIG.

[0079] As shown in the test results, the pneumatic tires of the present invention have improved heat resistance performance compared to the conventional tires, and from Example 32 onwards, the uneven wear resistance performance is also improved.

[0080] The present disclosure includes the following inventions: [Invention 1] A tread portion comprising: two or more longitudinal grooves extending continuously in the tire circumferential direction; a plurality of center lateral grooves extending in the tire width direction and communicating between the longitudinal grooves, arranged in the tire circumferential direction; a plurality of shoulder lateral grooves extending in the tire width direction outward of each of the two outermost longitudinal grooves in the tire width direction, communicating with each of the longitudinal grooves and passing through the ground contact edge, arranged in the tire circumferential direction; center blocks defined by the longitudinal grooves and the center lateral grooves; shoulder blocks defined by the outermost longitudinal groove and shoulder lateral groove in the tire width direction and having buttress portions outward in the tire width direction from the ground contact edge; tread-side dimples that open in a polygonal shape on the tread surface of at least the center blocks of the center blocks and shoulder blocks, with a cross section along the tire radial direction that tapers from the opening toward the groove bottom; and buttress-side dimples that open in a polygonal shape on the surface of the buttress portion, with a cross section along the tire radial direction that tapers from the opening toward the groove bottom. A tire in which the opening area of ​​the tread-side dimples is 10% to 125% of the opening area of ​​the buttress-side dimples. [Invention 2] The tire according to Invention 1, in which the opening area of ​​the tread-side dimples is 10% to 50% of the opening area of ​​the buttress-side dimples. [Invention 3] The tire according to Invention 2, in which the opening area of ​​the buttress-side dimples is 10% to 55% of the tread area of ​​the shoulder blocks. [Invention 4] The tire according to Invention 1, in which the opening area of ​​the tread-side dimples is 51% to 125% of the opening area of ​​the buttress-side dimples. [Invention 5] The tire according to Invention 4, in which the opening area of ​​the buttress-side dimples is 5% to 20% of the tread area of ​​the shoulder blocks. [Invention 6] The tire according to any one of Inventions 1 to 5, wherein the depth of the buttress-side dimples is 10% to 55% of the depth of the tread-side dimples.[Invention 7] The tire according to any one of Inventions 1 to 6, wherein the depth of the tread-side dimples is 25% or more of the groove depth of the shoulder lateral grooves. [Invention 8] The tire according to any one of Inventions 1 to 7, wherein the opening area of ​​the tread-side dimples is more than 6% and less than 20% of the block tread area of ​​the block in which the tread-side dimples are provided. [Invention 9] The tire according to any one of Inventions 1 to 8, wherein the tread-side dimples are also provided on the treads of the shoulder blocks. [Invention 10] The tire according to Invention 9, wherein the opening area of ​​the tread-side dimples provided on the shoulder blocks is 60% or more and 100% or less of the opening area of ​​the tread-side dimples provided on the center blocks. [Invention 11] The tire according to any one of Inventions 1 to 10, wherein five or more belt plies are arranged radially inward of the tread portion, and the tire is used for heavy-duty vehicles for construction or industry.

[0081] 1 Pneumatic tire (tire) 15A Tread surface (tread surface) 15B Buttress portion 21, 22 Longitudinal groove 31A Center block 32A Shoulder block 41 Center lateral groove 51 Shoulder lateral groove 61 Center dimple (tread side dimple) 61a Opening 61b Groove bottom 62 Shoulder dimple (tread side dimple) 62a Opening 62b Groove bottom 63 Buttress dimple (buttress portion side dimple) 63a Opening 63b Groove bottom 141 to 146 Belt ply

Claims

1. A tread portion comprising: two or more longitudinal grooves extending continuously in the tire circumferential direction; a plurality of center lateral grooves extending in the tire width direction and connecting between the longitudinal grooves, which are aligned in the tire circumferential direction; a plurality of shoulder lateral grooves extending in the tire width direction outward of each of the two outermost longitudinal grooves in the tire width direction, which extend in the tire width direction and connect to each of the longitudinal grooves, which pass through the ground contact edge, and which are aligned in the tire circumferential direction; center blocks defined by the longitudinal grooves and the center lateral grooves; shoulder blocks defined by the outermost longitudinal groove and shoulder lateral groove in the tire width direction, which have buttress portions outward in the tire width direction from the ground contact edge; tread-side dimples that open in a polygonal shape on the ground contact surface of at least the center blocks of the center blocks and shoulder blocks, with a cross section along the tire radial direction that tapers from the opening toward the groove bottom; and buttress-side dimples that open in a polygonal shape on the surface of the buttress portion, which cross section along the tire radial direction that tapers from the opening toward the groove bottom, A tire, wherein the opening area of ​​the tread-side dimples is 10% or more and 125% or less of the opening area of ​​the buttress-side dimples.

2. The tire according to claim 1, wherein the opening area of ​​the tread-side dimples is 10% to 50% of the opening area of ​​the buttress-side dimples.

3. A tire as set forth in claim 2, wherein the opening area of ​​the buttress-side dimples is 10% to 55% of the tread area of ​​the shoulder blocks.

4. The tire according to claim 1, wherein the opening area of ​​the tread-side dimples is 51% or more and 125% or less of the opening area of ​​the buttress-side dimples.

5. A tire as set forth in claim 4, wherein the opening area of ​​the buttress-side dimples is 5% to 20% of the tread area of ​​the shoulder blocks.

6. A tire as set forth in claim 1, wherein the depth of the buttress-side dimples is between 10% and 55% of the depth of the tread-side dimples.

7. The tire according to claim 1, wherein the depth of the tread-side dimples is 25% or more of the groove depth of the shoulder lateral grooves.

8. A tire as set forth in claim 1, wherein the opening area of ​​the tread-side dimple is greater than 6% and less than 20% of the block tread area of ​​the block on which the dimple is provided.

9. The tire according to claim 1, wherein the tread-side dimples are also provided on the tread surfaces of the shoulder blocks.

10. The tire according to claim 9, wherein the opening area of ​​the tread-side dimples provided on the shoulder blocks is 60% or more and 100% or less of the opening area of ​​the tread-side dimples provided on the center blocks.

11. A tire according to claim 1, wherein five or more belt plies are arranged on the radially inner side of the tread portion, and the tire is used for heavy-duty vehicles for construction or industry.

Images