tire

Abstract

To improve traction performance while securing heat build-up resistance.SOLUTION: Groove widths of narrow grooves 21, 22 and 41 with respect to groove depths thereof are 10[%] or more and 25[%] or less. Center blocks 31A have protruding parts 31Ab formed so that either of the parts adjacent to each other in a tire width direction protrudes toward the other. The protruding parts are arranged so that the parts fit to a space between protruding parts of the other center blocks formed adjacently in a tire circumferential direction. Width-directional narrow grooves and shoulder lug groove 43 are arranged so that respective end parts 41a and 43a thereof oppose to each other. An angle θa1 of the shoulder lug groove with respect to the tire circumferential direction is 80[Deg] or more and less than 100 [Deg]. The width-directional narrow grooves are larger in inclination with respect to the tire width direction than the shoulder lug grooves. The number of shoulder blocks 32A arranged in the tire circumferential direction is 28 or more and 43 or less. In a tread part, a center tread gauge on a tire equatorial plane CL is 40[mm] or more, and a ratio of the center tread gauge with respect to groove depths of the shoulder lug grooves is 105[%] or more and 185[%] or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to tires. [Background technology]

[0002] For example, Patent Document 1 describes a tire having, in its tread portion, one central narrow groove extending circumferentially in the tire central region, a pair of lateral narrow grooves extending circumferentially with the central narrow groove between them, lug grooves extending lateral to the tire width direction and passing through the single narrow groove, widthwise narrow grooves communicating with the lug grooves on the inner side in the tire width direction and extending to the central narrow groove, and a plurality of block land portions partitioned by the central narrow groove, the lateral narrow grooves, the lug grooves, and the widthwise narrow grooves. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-152836 Summary of the Invention [Problem to be solved by the invention]

[0004] For example, in heavy-duty tires such as OTR (Off-The-Road) tires, heat generation in the tread area is likely to cause heat separation under severe operating conditions of load and speed, so ensuring heat generation resistance is desirable. Furthermore, in order to increase running costs, it is desirable to ensure wear resistance. Therefore, one approach for this type of tire is to improve heat generation resistance without sacrificing wear resistance by narrowing the heat generation grooves and suppressing block movement. However, this approach tends to deteriorate traction performance due to the reduced groove area. Therefore, in tires based on block patterns, there is a need to improve traction performance while ensuring heat generation resistance.

[0005] An object of the present invention is to provide a tire that can improve traction performance while ensuring heat resistance. [Means for solving the problem]

[0006] In order to achieve the above object, a tire according to one aspect of the present invention includes, in a tread portion, a center circumferential narrow groove extending continuously along the tire circumferential direction, a pair of shoulder circumferential narrow grooves extending continuously along the tire circumferential direction and arranged adjacent to each other on the tire widthwise outer side of the center circumferential narrow groove, widthwise narrow grooves extending along the tire width direction so as to divide a center land portion between each of the circumferential narrow grooves into center blocks, and shoulder lug grooves extending along the tire width direction so as to divide each shoulder land portion on both tire widthwise outer sides of each of the shoulder circumferential narrow grooves into shoulder blocks, and having one end communicating with the shoulder circumferential narrow groove and the other end passing through a ground contact edge, wherein the groove width of each of the circumferential narrow grooves and the widthwise narrow grooves is 10% or more and 25% or less of the groove depth of each of the circumferential narrow grooves and the widthwise narrow grooves. the center blocks have adjacent convex portions in the tire width direction, each protruding toward the other adjacent center block in the tire width direction, and the convex portions are arranged so that the apex of the convex shape fits between the convex portions of the other center blocks adjacent in the tire circumferential direction; the widthwise narrow grooves are arranged with their ends facing the ends of the shoulder lug grooves, and the shoulder lug grooves have an angle with respect to the tire circumferential direction of 80 degrees or more and less than 100 degrees, and the widthwise narrow grooves have a greater inclination with respect to the tire width direction than the shoulder lug grooves; the number of shoulder blocks lined up in the tire circumferential direction is 28 to 43; the tread portion has a center tread gauge of 40 mm or more at the tire equatorial plane, and the center tread gauge is 105% to 185% of the groove depth of the shoulder lug grooves. [Effects of the Invention]

[0007] According to the present invention, it is possible to improve traction performance while ensuring heat resistance. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a plan view of a tread of a pneumatic tire according to an embodiment. [Figure 2] FIG. 2 is a partially enlarged meridian cross-sectional view of the pneumatic tire according to the embodiment. [Figure 3] FIG. 3 is a cross-sectional view taken along line AA in FIG. [Figure 4] FIG. 4 is a cross-sectional view taken along the line BB in FIG. [Figure 5] FIG. 5 is a table showing the results of a performance test of the pneumatic tire according to the embodiment. [Figure 6] FIG. 6 is a table showing the results of a performance test of the pneumatic tire according to the embodiment. [Figure 7] FIG. 7 is a table showing the results of a performance test of the pneumatic tire according to the embodiment. [Figure 8] FIG. 8 is a table showing the results of a performance test of the pneumatic tire according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[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 the direction perpendicular to the tire rotational axis (not shown), which is the rotational axis of the pneumatic tire 1 of this embodiment. The tire radial inner side refers to the side toward the tire rotational axis in the tire radial direction, and the tire radial outer side refers to the side away from the tire rotational axis in the tire radial direction. The tire circumferential direction refers to the direction around the tire rotational axis as the central axis. The tire width direction refers to the direction parallel to the tire rotational axis. The tire width inner side refers to the side toward the tire equatorial plane (tire equator line) CL in the tire width direction, and the tire width 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 rotational 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 width 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. Also, a cross section in the tire meridian direction (meridian cross section) refers to a cross section of the tire cut by a plane including the tire rotation axis.

[0011] 1 is a meridian cross section of a pneumatic tire 1 according to an embodiment. In this embodiment, a heavy-duty pneumatic radial tire mounted on heavy-duty vehicles such as trucks and buses will be described as an example. The pneumatic tire 1 according to this embodiment is particularly suitable for use as a tire mounted on the steering axle and drive axle of a heavy-duty vehicle.

[0012] The pneumatic tire 1 is formed symmetrically in the tire width direction with respect to the tire equatorial plane CL. For this reason, Fig. 2 shows a portion of one side in the tire width direction with the tire equatorial plane CL as the boundary. Note that Fig. 2 is an enlarged view of a meridian cross section of the pneumatic tire 1, and shows a cross section along widthwise narrow grooves 41 and shoulder lug grooves 43, which will be described later.

[0013] 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 portion 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 this embodiment, the carcass layer 13 is formed by stacking two carcass plies. The carcass layer 13 is toroidally laid between both 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 covering multiple carcass cords made of steel with coating rubber and rolling them, and has a cord angle (defined as the inclination angle of the carcass cords in the longitudinal direction with respect to the tire circumferential direction) of 80° to 90° in absolute value for radial tires, and 30° to 45° in absolute value for bias tires.

[0017] The belt layer 14 is also referred to as a belt member, and is formed by laminating a plurality of belt plies (also referred to as belts) 141-147, and is disposed by being wound around the outer periphery of the carcass layer 13. These belt plies 141-147 are combinations of belts of various configurations, such as a 0-degree belt and 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 that the tire is suitable for use in heavy-duty vehicles for construction and industrial use. The belt plies are formed by coating a plurality of steel belt cords (also referred to as wire rods) with coating rubber and rolling them. The pair of cross belts are formed by coating a plurality of steel belt cords with coating rubber and rolling them, and have cord angles of opposite signs to each other. 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 called a tread surface) 15A on the outer peripheral surface of the tread portion that comes into contact with the road surface during running. The outer ends of the tread surface 15A in the tire width direction are 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 of 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. The linear distance in the tire width direction when the tread surface 15A is unfolded between each ground contact edge T is defined as the unfolded width TDW.

[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 inner side in the tire radial direction of each bead core and the turned-up portion of the carcass layer 13 to the outer side in the tire width direction, 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. 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. 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 (also called the open groove width) is measured as the maximum distance between the 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 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 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 tire has partial unevenness or sipes at the groove bottom, the groove depth is measured excluding these.

[0025] As shown in Fig. 1, the pneumatic tire 1 of the embodiment has, on a tread surface 15A, a center circumferential narrow groove 21, shoulder circumferential narrow grooves 22, widthwise narrow grooves 41, one-side open narrow grooves 42, shoulder lug grooves 43, and shoulder dimples 51. Furthermore, as shown in Fig. 1, the pneumatic tire 1 of the embodiment has buttress dimples 52 on the surface of the buttress portion 15B.

[0026] The center circumferential narrow groove 21 is a groove that extends continuously along the tire circumferential direction. The center circumferential narrow groove 21 is arranged on the tire equatorial plane CL. The shoulder circumferential narrow grooves 22 are grooves that extend continuously along the tire circumferential direction. A pair of shoulder circumferential narrow grooves 22 are arranged adjacent to each other on both outer sides in the tire width direction of the center circumferential narrow groove 21. Therefore, in the pneumatic tire 1, center land portions 31 are defined along the tire circumferential direction between the circumferential narrow grooves 21, 22, and shoulder land portions 32 are defined along the tire circumferential direction on the tire width direction outer sides of the shoulder circumferential narrow grooves 22.

[0027] The widthwise narrow grooves 41 are grooves that extend along the tire width direction. A plurality of widthwise narrow grooves 41 are provided in each center land portion 31, lined up in the tire circumferential direction. Each end 41a of the widthwise narrow groove 41 communicates with the center circumferential narrow groove 21 and the shoulder circumferential narrow groove 22 that are adjacent in the tire width direction. Therefore, in the pneumatic tire 1, the plurality of widthwise narrow grooves 41 divide each center land portion 31 into a plurality of center blocks 31A.

[0028] The one-side open narrow groove 42 is a groove that extends along the tire width direction, and one one-side open narrow groove 42 is provided in each center block 31A.

[0029] The shoulder lug grooves 43 are grooves that extend along the tire width direction. A plurality of shoulder lug grooves 43 are provided in each shoulder land portion 32, lined up in the tire circumferential direction. One end 43a of each shoulder lug groove 43 communicates with the shoulder circumferential narrow groove 22. Therefore, in the pneumatic tire 1, the shoulder land portion 32 is divided into a plurality of shoulder blocks 32A by the plurality of shoulder lug grooves 43. The number of shoulder blocks 32A lined up in the tire circumferential direction on one side of the tire width direction is 28 to 43 around the tire (one circumference in the tire circumferential direction). The other end 43a of each shoulder lug groove 43 passes through the ground contact edge T and reaches the buttress portion 15B. Therefore, in the pneumatic tire 1, the buttress portion 15B is divided into a plurality of sections together with the shoulder blocks 32A. Therefore, like the shoulder blocks 32A, the number of sections of the buttress portion 15B lined up in the tire circumferential direction is 28 to 43 around the tire (one circumference in the tire circumferential direction).

[0030] The shoulder dimples 51 are recesses recessed from the tread surface 15A. One shoulder dimple 51 is disposed in each shoulder block 32A between shoulder lug grooves 43 adjacent to each other in the tire circumferential direction.

[0031] The buttress dimples 52 are recesses recessed from the surface of the buttress portion 15B. One buttress dimple 52 is arranged in each section of the buttress portion 15B defined together with the shoulder blocks 32A between shoulder lug grooves 43 adjacent to each other in the tire circumferential direction.

[0032] The above-mentioned grooves and dimples will now be described in detail.

[0033] As shown in FIG. 1 , the center circumferential narrow groove 21 has linear first groove portions 21a and second groove portions 21b. The first groove portions 21a are relatively longer in the tire circumferential direction than the second groove portions 21b and are arranged at an incline relative to the tire circumferential direction. The second groove portions 21b are relatively shorter in the tire circumferential direction than the first groove portions 21a and are arranged at an incline relative to the tire circumferential direction. The first groove portions 21a and the second groove portions 21b have angles with respect to the tire circumferential direction that are opposite in sign to each other and are arranged alternately and continuously in the tire circumferential direction. Therefore, the center circumferential narrow groove 21 is formed into a zigzag shape extending continuously along the tire circumferential direction by the first groove portions 21a and the second groove portions 21b being arranged alternately in the tire circumferential direction. Here, one end 41a of the widthwise narrow groove 41 is connected to the center circumferential narrow groove 21 and the other end 41a is connected to the shoulder circumferential narrow groove 22. One end 41a of the widthwise narrow groove 41 communicates with a bent portion where the first groove portion 21a and the second groove portion 21b of the center circumferential narrow groove 21 communicate with each other. In the center circumferential narrow groove 21, one first groove portion 21a and one second groove portion 21b are arranged in one center block 31A defined by adjacent widthwise narrow grooves 41 in the tire width direction.

[0034] Center blocks 31A are arranged on both sides of the center circumferential narrow groove 21 in the tire width direction. Each center block 31A has one first groove portion 21a and one second groove portion 21b of the center circumferential narrow groove 21, forming a convex portion 31Ab that protrudes outward in the tire width direction. In each of the center blocks 31A adjacent to each other in the tire width direction, the convex portion 31Ab protrudes from one side toward the other, with the center circumferential narrow groove 21 as the boundary. Each convex portion 31Ab is arranged so that the apex of its protruding shape fits between the convex portions 31Ab of two center blocks 31A adjacent to each other in the tire circumferential direction. The center blocks 31A adjacent to each other in the tire width direction are arranged so that the convex portions 31Ab intermesh with each other, and are formed in a point-symmetrical shape. 1, the protrusions 31Ab are configured so that adjacent center blocks 31A in the tire width direction mesh with each other, and the protrusion dimension Ma of the protrusions 31Ab from the tire equatorial plane CL in the tire width direction satisfies the relationship 2.5%≦Ma / TDW≦10% with respect to the developed width TDW of the tread surface 15A. The apex position La of the protrusions 31Ab is within the range of 40%≦La / Lmax≦60% with respect to the maximum circumferential dimension Lmax of one center block 31A. The maximum widthwise dimension Wmax of the center block 31A satisfies the relationship 20%≦Wmax / TDW≦35% with respect to the developed width TDW of the tread surface 15A.

[0035] The center circumferential narrow groove 21 has a groove width Wa that satisfies the relationship of 10%≦Wa / Da≦25% with respect to its groove depth Da. The center circumferential narrow groove 21 has a groove depth Da that satisfies the relationship of 50%≦Da / De≦100% with respect to the groove depth De of the shoulder lug grooves 43.

[0036] As shown in Fig. 1, the widthwise narrow grooves 41 and the shoulder lug grooves 43 are provided continuously along the tire width direction. The shoulder circumferential narrow grooves 22 communicate with the widthwise narrow grooves 41 and the shoulder lug grooves 43 at positions where the widthwise narrow grooves 41 and the shoulder lug grooves 43 communicate with each other. Therefore, the center blocks 31A and the shoulder blocks 32A are arranged adjacent to each other in the tire width direction with the shoulder circumferential narrow groove 22 between them. Therefore, like the shoulder blocks 32A, the number of center blocks 31A lined up in the tire circumferential direction is 28 to 43 around the tire (one circumferential revolution).

[0037] As shown in FIG. 1 , each end 22a of the shoulder circumferential narrow groove 22 extending in the tire circumferential direction communicates with the widthwise narrow groove 41 and the shoulder lug groove 43 between the adjacent center block 31A and shoulder block 32A. The shoulder circumferential narrow groove 22 is formed in a zigzag shape along the tire circumferential direction between the adjacent center block 31A and shoulder block 32A, with multiple bends 22b between each end 22a. In the pneumatic tire 1 of the embodiment, the shoulder circumferential narrow groove 22 is formed with two bends 22b between each end 22a. Therefore, the center block 31A and the shoulder block 32A adjacent to each other in the tire width direction have circumferential concave and convex portions 31Aa, 32Aa that mesh with each other in the tire circumferential direction. The circumferential uneven portions 31Aa, 32Aa are engaged with each other at two or more locations (two locations in the pneumatic tire 1 of the embodiment) between each pair of adjacent blocks 31A, 32A in the tire width direction.

[0038] The groove width Wb of the shoulder circumferential narrow groove 22 and the groove depth Db thereof satisfy the relationship of 10%≦Wb / Db≦25%. The groove depth Db of the shoulder circumferential narrow groove 22 and the groove depth De of the shoulder lug groove 43 satisfy the relationship of 50%≦Db / De≦100%.

[0039] As shown in FIG. 1 , the widthwise narrow grooves 41 are formed linearly, and within the tire width direction range of one center block 31A, one end 41a is connected to the center circumferential narrow groove 21, and the other end 41a is connected to the shoulder circumferential narrow groove 22. The widthwise narrow grooves 41 are inclined at an angle θb with respect to the tire width direction. The angle θb is 15 degrees or more and 35 degrees or less. The angle θb of the widthwise narrow grooves 41 with respect to the tire width direction is in the same direction as the angle θa2 of the shoulder lug grooves 43 with respect to the tire width direction, but the angle is greater.

[0040] Furthermore, the widthwise narrow groove 41 has a larger groove width at its other end 41a, which is connected to the shoulder circumferential narrow groove 22, compared to other areas. The groove width Wc is measured excluding the groove width at this other end 41a. The widthwise narrow groove 41 has a groove width Wc that satisfies the relationship of 10%≦Wc / Dc≦25% with respect to its own groove depth Dc. The widthwise narrow groove 41 has a groove depth Dc that satisfies the relationship of 50%≦Dc / De≦100% with respect to the groove depth De of the shoulder lug groove 43.

[0041] As shown in FIG. 1, the one-side open narrow groove 42 is formed linearly, and within the range of one center block 31A, one end 42a is connected to the shoulder circumferential narrow groove 22, and the other end 42a terminates within the center block 31A. The one-side open narrow groove 42 has a widened portion 42c at the terminating end 42a, where the groove width is widened. Although the widened portion 42c is formed in a rectangular shape in FIG. 1, it may be circular or elliptical. The one-side open narrow groove 42 is inclined at an angle θc with respect to the tire width direction. The angle θc is 15 degrees or more and 35 degrees or less. The angle θc of the one-side open narrow groove 42 is the same as the angle θb of the widthwise narrow groove 41, and the inclination direction with respect to the tire width direction is the same. Therefore, the angle θc of the one-side open narrow groove 42 with respect to the tire width direction is in the same direction as and larger than the angle θa2 of the shoulder lug groove 43 with respect to the tire width direction. The extension length L1 of the one-side open narrow groove 42 with respect to the extension length L2 of the widthwise narrow groove 41 satisfies the relationship 60[%]≦L1 / L2≦80[%].

[0042] The groove width Wd of the one-sided open narrow groove 42 satisfies the relationship of 10%≦Wd / Dd≦25% with respect to the groove depth Dd of the one-sided open narrow groove 42. The groove depth Dd of the one-sided open narrow groove 42 satisfies the relationship of 75%≦Dd / De≦100% with respect to the groove depth De of the shoulder lug groove 43 (see FIG. 2).

[0043] The shoulder lug grooves 43 are provided on the surfaces of the tread surface 15A and the buttress portion 15B. The groove depth De is measured as a maximum value based on the tread surface 15A. As shown in FIG. 1, the groove width We of the shoulder lug grooves 43 satisfies the relationship 10%≦We / P≦35% with respect to the pitch length P of the shoulder blocks 32A. The shoulder lug grooves 43 are inclined with respect to the tire circumferential direction and the tire width direction on the tread surface 15A. The angle θa1 of the shoulder lug grooves 43 with respect to the tire circumferential direction is 80 degrees or more and 100 degrees or less. That is, the shoulder lug grooves 43 are inclined at ±10 degrees with respect to the tire width direction.

[0044] The depth Df of the shoulder dimple 51 satisfies the relationship of 10[%]≦Df / De≦50[%] with respect to the groove depth De of the shoulder lug groove 43.

[0045] The buttress dimples 52 have a depth Dg that satisfies the relationship 1[%]≦Dg / TDW≦2.5[%] relative to the developed width TDW of the tread surface 15A.

[0046] As shown in Fig. 2, the tread portion having the above-described grooves and dimples has a center tread gauge Ga at the tire equatorial plane CL of 40 mm≦Ga. The center tread gauge Ga is the shortest distance from the tread surface 15A to the belt cord of the outermost belt ply (belt ply 147) in the tire radial direction at the tire equatorial plane CL. The center tread gauge Ga satisfies the relationship 105%≦Ga / De≦185% with respect to the groove depth De of the shoulder lug grooves 43.

[0047] The pneumatic tire 1 of the above-described embodiment is characterized in that the groove widths Wa, Wb, and Wc of the circumferential narrow grooves 21, 22 and widthwise narrow grooves 41 are 10% to 25% of the groove depths Da, Db, and Dc of the circumferential narrow grooves 21, 22 and widthwise narrow grooves 41, respectively, and the center blocks 31A have convex portions 31Ab that protrude toward each other adjacent to each other in the tire width direction, and the convex portions 31Ab are arranged so that the apex of the convex shape fits between the convex portions 31Ab of other center blocks 31A adjacent to each other in the tire circumferential direction, and the widthwise narrow grooves 41 are arranged so that their ends 41a are aligned with the ends 41a of the shoulder lug grooves 43. 3a, and the shoulder lug grooves 43 have an angle θa1 with respect to the tire circumferential direction of 80 degrees or more and less than 100 degrees, the widthwise narrow grooves 41 have a greater inclination with respect to the tire width direction than the shoulder lug grooves 43, the number of shoulder blocks 32A arranged in the tire circumferential direction is 28 or more and 43 or less, the tread portion has a center tread gauge Ga of 40 mm or more at the tire equatorial plane CL, and the center tread gauge Ga is 105% or more and 185% or less of the groove depth De of the shoulder lug grooves 43.

[0048] According to the pneumatic tire 1, by configuring the above pattern, when the narrow grooves 21, 22, and 41 close during contact with the ground, the rigidity of the tread portion increases, strain in the tread portion can be reduced, and heat resistance can be improved. Furthermore, according to the pneumatic tire 1, the narrow grooves 21, 22, and 41 are arranged along the tire circumferential direction and tire width direction, thereby improving heat dissipation performance. In the pneumatic tire 1, the groove widths Wa, Wb, and Wc of the narrow grooves 21, 22, and 41 satisfy a relationship of 10% to 25% of the groove depths Da, Db, and Dc, thereby ensuring heat dissipation performance and the function of the grooves closing during contact with the ground to increase rigidity. If the relationship is less than 10%, the heat dissipation effect is reduced, and if the relationship is more than 25%, the narrow grooves 21, 22, and 41 are less likely to close during contact with the ground, resulting in reduced rigidity. Furthermore, in this pneumatic tire 1, the convex portions 31Ab of the center blocks 31A are positioned so that they fit between the convex portions 31Ab of other center blocks 31A adjacent to each other in the tire circumferential direction, thereby ensuring the function of the center blocks 31A supporting each other when in contact with the ground, thereby increasing the rigidity of the tread portion. Furthermore, in this pneumatic tire 1, the ends 41a of the widthwise narrow grooves 41 and the ends 43a of the shoulder lug grooves 43 are positioned opposite and continuous to each other, thereby enhancing the edge effect and improving traction performance. This traction performance is significantly achieved when the angle θa1 of the shoulder lug grooves 43 relative to the tire circumferential direction is 80 degrees or more but less than 100 degrees, and when the widthwise narrow grooves 41 are inclined more sharply relative to the tire width direction than the shoulder lug grooves 43. If the angle θa1 is less than 80 degrees or greater than 100 degrees, the edge effect in the tire circumferential direction is reduced. Moreover, by specifying the number of shoulder blocks 32A arranged circumferentially, the pneumatic tire 1 can ensure heat dissipation and rigidity. If the number of shoulder blocks 32A is less than 28, the number of shoulder lug grooves 43 will be reduced, resulting in poor heat dissipation. If the number of shoulder blocks 32A exceeds 43, the number of shoulder lug grooves 43 will be increased, resulting in reduced rigidity and poor heat resistance. Moreover, by specifying the relationship between the center tread gauge Ga and the groove depth De of the shoulder lug grooves 43, the pneumatic tire 1 can prevent the effects of heat accumulation and ensure heat dissipation.As a result, the pneumatic tire 1 can have improved heat resistance and wear resistance.

[0049] In the pneumatic tire 1 of the embodiment, the center blocks 31A are arranged such that the protrusions 31Ab adjacent to each other in the tire width direction mesh with each other in the tire circumferential direction.

[0050] In this pneumatic tire 1, adjacent protrusions 31Ab in the tire width direction interlock with each other, thereby sufficiently increasing block rigidity. The protrusions 31Ab preferably have a protrusion dimension Ma in the tire width direction from the tire equatorial plane CL within a range of 2.5% to 10% of the developed width TDW. If the protrusion dimension Ma is less than 2.5% of the developed width TDW, the interlocking tends to be insufficient and the rigidity tends to be weak. If the protrusion dimension Ma exceeds 10%, the rigidity of the protrusions 31Ab itself tends to be weak. Furthermore, the tire circumferential position La of the apex of each protrusion 31Ab is preferably within a range of 40% to 60% of the maximum circumferential dimension Lmax of the center block 31A. If the protrusion dimension Ma is outside this range of 40% to 60%, the interlocking in the tire width direction is insufficient, the center block 31A tends to move easily in the tire circumferential direction, and the rigidity tends to be weak.

[0051] In addition, in the pneumatic tire 1 of the embodiment, the center block 31A has a one-sided opening narrow groove 42 whose one end 42a is connected to the shoulder circumferential narrow groove 22 and whose other end 42a terminates within the center block 31A and extends along the tire width direction, and the one-sided opening narrow groove 42 is arranged in the same inclination direction with respect to the tire width direction as the widthwise narrow groove 41.

[0052] According to this pneumatic tire 1, the one-side open narrow groove 42 enhances heat dissipation and improves the edge effect. Furthermore, this pneumatic tire 1 can prevent a local decrease in block rigidity by providing the one-side open narrow groove 42 with the same inclination direction with respect to the tire width direction as the widthwise narrow groove 41. To fully achieve this effect, it is preferable that the one-side open narrow groove 42 and the widthwise narrow groove 41 have the same angle with respect to the tire width direction. Furthermore, this pneumatic tire 1 can ensure sufficient edge effect and block rigidity by setting the extension length L1 of the one-side open narrow groove 42 to be 60% or more and 80% or less of the extension length L2 of the widthwise narrow groove 41. If the extension length L1 is less than 60%, the edge effect tends to be reduced, and if it exceeds 80%, the block rigidity tends to be reduced. Furthermore, this pneumatic tire 1 can enhance heat dissipation by providing a widened portion 42c at the end of the one-side open narrow groove 42.

[0053] In the pneumatic tire 1 of the embodiment, the center block 31A and the shoulder block 32A have circumferential concave and convex portions 31Aa, 32Aa at two or more locations where adjacent blocks in the tire width direction mesh with each other in the tire circumferential direction.

[0054] According to this pneumatic tire 1, the circumferential uneven portions 31Aa, 32Aa restrict the center block 31A and the shoulder block 32A from moving in the tire circumferential direction, thereby improving heat resistance.

[0055] In the pneumatic tire 1 of the embodiment, the center block 31A has a maximum dimension Wmax in the tire width direction that is 20% or more and 35% or less of the developed width TDW of the tread surface 15A.

[0056] In this pneumatic tire 1, by specifying the tire width direction dimension of the center block 31A, excessive movement of the center block 31A can be suppressed, block rigidity can be ensured, and heat resistance can be improved. If the ratio is less than 20%, block rigidity tends to be low, and if the ratio is more than 35%, the block rigidity of the center block 31A increases, but the movement of the shoulder block 43 increases accordingly, tending to deteriorate heat resistance.

[0057] In the pneumatic tire 1 of the embodiment, the groove depths Da, Db, Dc of the circumferential narrow grooves 21, 22 and the widthwise narrow groove 41 are 50% to 100% of the groove depth De of the shoulder lug groove 43.

[0058] According to this pneumatic tire 1, the groove depths Da, Db, and Dc of the circumferential narrow grooves 21, 22 and the widthwise narrow groove 41 are ensured, thereby ensuring heat dissipation and suppressing a decrease in heat resistance. The shallower the groove depths Da, Db, and Dc of the circumferential narrow grooves 21, 22 and the widthwise narrow groove 41, the lower the heat dissipation and the worse the heat resistance. If the depths Da, Db, and Dc are less than 50%, the heat dissipation tends to worsen, and if the depths are more than 100%, the effect of heat dissipation is reduced.

[0059] In the pneumatic tire 1 of the embodiment, the shoulder lug groove 43 has a groove width We of 10% or more and 35% or less of the pitch length P of the shoulder block 32A.

[0060] In this pneumatic tire 1, the relationship between the groove width We of the shoulder lug grooves 43 and the pitch length P of the shoulder blocks 32A ensures heat dissipation and prevents a decrease in heat resistance, while ensuring block rigidity and heat resistance. If the relationship is less than 10%, heat dissipation tends to decrease and heat resistance tends to deteriorate, while if it exceeds 35%, the rigidity of the shoulder blocks 32A decreases, tending to deteriorate heat resistance.

[0061] In addition, in the pneumatic tire 1 of the embodiment, the one-sided opening narrow groove 42 has a groove width Wd of 10% or more and 25% or less of its groove depth Dd, and its groove depth Dd is 75% or more and 100% or less of the groove depth De of the shoulder lug groove 43.

[0062] According to this pneumatic tire 1, the arrangement of the one-sided open narrow grooves 42 can improve heat dissipation and heat resistance. By specifying the groove width Wd and groove depth Dd of the one-sided open narrow grooves 42, a decrease in rigidity and heat dissipation of the center block 31A can be suppressed, and heat resistance can be ensured. If the groove width Wd is less than 10% of the groove depth Dd, heat dissipation tends to deteriorate. If it exceeds 25%, the one-sided open narrow grooves 42 do not close, which reduces rigidity and tends to deteriorate heat resistance. Furthermore, if the groove depth Dd is less than 75% of the groove depth De, heat dissipation tends to deteriorate. If it exceeds 100%, the effect of heat dissipation is reduced.

[0063] In the pneumatic tire 1 of the embodiment, the buttress dimples 52 on the surface of the buttress portion 15B have a depth Dg of 1% to 2.5% of the developed width TDW of the tread surface 15A.

[0064] In this pneumatic tire 1, the placement of buttress dimples 52 in the buttress portion 15B improves heat dissipation and reduces the volume of the tread rubber 15, improving heat resistance. Furthermore, by specifying the depth Dg of the buttress dimples 52, this pneumatic tire 1 achieves the above-mentioned effects significantly while suppressing deterioration in durability due to a decrease in the rigidity of the buttress portion 15B. If the depth Dg is less than 1%, the effects of the buttress portion 15B cannot be expected, and if the depth exceeds 2.5%, the rigidity of the buttress portion 15B will decrease, tending to reduce durability.

[0065] In the pneumatic tire 1 of the embodiment, the shoulder dimple 51 of the shoulder block 32A has a depth Df of 10% to 50% of the groove depth De of the shoulder lug groove 43.

[0066] In this pneumatic tire 1, the shoulder dimples 51 are arranged in the shoulder blocks 32A, improving heat dissipation and reducing the volume of the tread rubber 15, improving heat resistance. Furthermore, by specifying the depth Df of the shoulder dimples 51, the pneumatic tire 1 significantly achieves the above effects while suppressing deterioration of durability due to reduced rigidity of the shoulder blocks 32A. If the depth Df is less than 10%, the reduced volume of the tread rubber 15 tends to reduce the heat resistance effect, while if the depth Df exceeds 50%, the reduced rigidity tends to reduce heat resistance.

[0067] Furthermore, the pneumatic tire 1 of the embodiment has five or more belt plies arranged therein and is used for heavy-duty construction or industrial vehicles.

[0068] In the present embodiment, as described above, a 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. [Example]

[0069] 5 to 8 are tables showing the results of performance tests of the 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 traction performance.

[0070] 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, measuring the temperature of the tread center (tire equatorial plane). Based on the measurement results, an index rating is then calculated, with the conventional tire being used as the benchmark (100). The higher the rating, the better.

[0071] The traction performance evaluation test involves 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 at speeds of 10 to 25 km / h for 3,000 hours, and a sensory evaluation is conducted by a test driver. Based on the evaluation results, an index rating is then calculated, with the conventional tire being assigned a standard value of 100. The higher the rating, the better.

[0072] The conventional pneumatic tire does not have a center circumferential narrow groove, but has shoulder blocks formed by shoulder circumferential narrow grooves and shoulder lug grooves.

[0073] The pneumatic tire of the example mainly has a center circumferential narrow groove, shoulder circumferential narrow grooves, widthwise narrow grooves, shoulder lug grooves, center blocks, and shoulder blocks, and satisfies the specified range.

[0074] As shown in the test results, it is clear that the pneumatic tire of this example has improved heat resistance and wear resistance compared to the conventional tire.

[0075] The present disclosure includes the following inventions. [Invention 1] In the tread area, a center circumferential narrow groove extending continuously along the tire circumferential direction; a pair of shoulder circumferential narrow grooves extending continuously along the tire circumferential direction and arranged adjacent to each other on the tire width direction outer sides of the center circumferential narrow groove; widthwise narrow grooves extending along the tire width direction so as to divide a center land portion between each of the circumferential narrow grooves into center blocks, each end of which is connected to each of the adjacent circumferential narrow grooves; shoulder lug grooves, one end of which extends along the tire width direction so as to divide each shoulder land portion on both outer sides in the tire width direction of each shoulder circumferential narrow groove into shoulder blocks and which communicate with the shoulder circumferential narrow groove and the other end of which passes through the ground contact edge; Including, Each of the circumferential narrow grooves and the widthwise narrow grooves has a groove width of 10% or more and 25% or less of its groove depth, The center blocks each have a protrusion that protrudes toward the other adjacent block in the tire width direction, The convex portion is arranged so that the top of the convex shape fits between the convex portions of other center blocks adjacent to each other in the tire circumferential direction, The widthwise narrow grooves are arranged such that their ends face the ends of the shoulder lug grooves, The shoulder lug groove has an angle of 80 degrees or more and less than 100 degrees with respect to the tire circumferential direction, the widthwise narrow groove has a larger inclination with respect to the tire width direction than the shoulder lug groove, The number of the shoulder blocks arranged in the tire circumferential direction is 28 or more and 43 or less, The tread portion has a center tread gauge of 40 mm or more at the tire equatorial plane, The center tread gauge is 105% or more and 185% or less of the groove depth of the shoulder lug groove. tire. [Invention 2] The center blocks are arranged such that the convex portions adjacent to each other in the tire width direction mesh with each other in the tire circumferential direction. A tire according to invention 1. [Invention 3] The center block has a narrow groove that is open on one side and that extends along the tire width direction, one end of which is connected to the shoulder circumferential narrow groove and the other end of which terminates within the center block, The one-side opening narrow groove is provided in the same inclination direction with respect to the tire width direction as the width direction narrow groove. The tire according to claim 1 or 2. [Invention 4] The center block and the shoulder block have circumferential concave-convex portions at two or more locations in each block, where adjacent blocks in the tire width direction mesh with each other in the tire circumferential direction. A tire according to any one of inventions 1 to 3. [Invention 5] The center block has a maximum dimension in the tire width direction of 20% to 35% of the developed width of the tread surface. A tire according to any one of inventions 1 to 4. [Invention 6] The groove depth of each of the circumferential narrow grooves and the widthwise narrow grooves is 50% or more and 100% or less of the groove depth of the shoulder lug groove. A tire according to any one of inventions 1 to 5. [Invention 7] The shoulder lug groove has a groove width of 10% or more and 35% or less of the pitch length of the shoulder block. A tire according to any one of inventions 1 to 6. [Invention 8] The center block has a narrow groove that is open on one side and that extends along the tire width direction, one end of which is connected to the shoulder circumferential narrow groove and the other end of which terminates within the center block, The one-side open narrow groove has a groove width of 10% or more and 25% or less of its groove depth, and a groove depth of 75% or more and 100% or less of the groove depth of the shoulder lug groove. A tire according to any one of inventions 1 to 7. [Invention 9] The buttress dimples are recessed from the surface of the buttress portion. The depth of the buttress dimples is 1% or more and 2.5% or less of the developed width of the tread surface. A tire according to any one of inventions 1 to 8. [Invention 10] a shoulder dimple recessed from the surface of the shoulder block; The depth of the shoulder dimple is 10% or more and 50% or less of the groove depth of the shoulder lug groove. A tire according to any one of inventions 1 to 9. [Invention 11] 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. A tire according to any one of inventions 1 to 10. [Explanation of symbols]

[0076] 1. Pneumatic tires (tires) 15A tread surface 15B Buttress section 21 Center circumferential narrow groove 22 Shoulder circumferential narrow groove 31 Center Land Section 31A Center Block 31Aa Circumferential unevenness 31Ab convex part 32 Shoulder land area 32A Shoulder Block 32Aa Circumferential unevenness 41 Width direction thin groove 41a end 42 One-sided opening narrow groove 42a end 43 Shoulder lug groove 43a edge 51 Shoulder dimple 52 Buttress dimples

Claims

1. In the tread area, a center circumferential narrow groove extending continuously along the tire circumferential direction; a pair of shoulder circumferential narrow grooves extending continuously along the tire circumferential direction and arranged adjacent to each other on the outer sides of the center circumferential narrow groove in the tire width direction; widthwise narrow grooves extending along the tire width direction so as to divide a center land portion between each of the circumferential narrow grooves into center blocks, each end of which is connected to each of the adjacent circumferential narrow grooves; shoulder lug grooves, one end of which extends along the tire width direction so as to divide each shoulder land portion on both outer sides in the tire width direction of each shoulder circumferential narrow groove into shoulder blocks and which communicate with the shoulder circumferential narrow groove and the other end of which passes through the ground contact edge; Including, Each of the circumferential narrow grooves and the widthwise narrow grooves has a groove width of 10% or more and 25% or less of its groove depth, The center blocks each have a protrusion that protrudes toward the other adjacent block in the tire width direction, The convex portion is arranged so that the top of the convex shape fits between the convex portions of other center blocks adjacent to each other in the tire circumferential direction, The widthwise narrow grooves are arranged such that their ends face the ends of the shoulder lug grooves, the shoulder lug groove has an angle with respect to the tire circumferential direction of 80 degrees or more and less than 100 degrees, the widthwise narrow groove has a larger inclination with respect to the tire width direction than the shoulder lug groove, the number of shoulder blocks arranged in the tire circumferential direction is equal to or greater than 28 and is equal to or less than 43, The tread portion has a center tread gauge of 40 mm or more at the tire equatorial plane, the center tread gauge is 105% or more and 185% or less of the groove depth of the shoulder lug groove; tire.

2. The center blocks are arranged such that the convex portions adjacent to each other in the tire width direction mesh with each other in the tire circumferential direction.

2. The tire of claim 1.

3. The center block has a narrow groove that is open on one side and that extends along the tire width direction, one end of which is connected to the shoulder circumferential narrow groove and the other end of which terminates within the center block, The one-side opening narrow groove is provided in the same inclination direction with respect to the tire width direction as the width direction narrow groove.

2. The tire of claim 1.

4. The center block and the shoulder block have circumferential concave-convex portions at two or more locations in each block, where adjacent blocks in the tire width direction mesh with each other in the tire circumferential direction.

2. The tire of claim 1.

5. The center block has a maximum dimension in the tire width direction of 20% to 35% of the developed width of the tread surface.

2. The tire of claim 1.

6. The groove depth of each of the circumferential narrow grooves and the widthwise narrow grooves is 50% or more and 100% or less of the groove depth of the shoulder lug groove.

2. The tire of claim 1.

7. The shoulder lug groove has a groove width of 10% or more and 35% or less of the pitch length of the shoulder block.

2. The tire of claim 1.

8. The center block has a narrow groove that is open on one side and that extends along the tire width direction, one end of which is connected to the shoulder circumferential narrow groove and the other end of which terminates within the center block, The one-side open narrow groove has a groove width of 10% to 25% of its groove depth, and a groove depth of 75% to 100% of the groove depth of the shoulder lug groove.

2. The tire of claim 1.

9. The buttress dimples are recessed from the surface of the buttress portion. The buttress dimples have a depth of 1% or more and 2.5% or less of the developed width of the tread surface.

2. The tire of claim 1.

10. a shoulder dimple recessed from the surface of the shoulder block; The depth of the shoulder dimple is 10% or more and 50% or less of the groove depth of the shoulder lug groove.

2. The tire of claim 1.

11. 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.

2. The tire of claim 1.

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