Pneumatic tire

Abstract

To provide a pneumatic tire which can suppress damages of projections.SOLUTION: A pneumatic tire 1 includes a center circumferential direction groove 12 which has a plurality of first bent parts 12a bent in a protruding manner in a tire axial direction TW1, and a plurality of second bent parts 12b bent in the protruding manner in a tire axial direction TW2, in which the plurality of first bent parts 12a and the plurality of second bent parts 12b are alternately arranged in a tire circumferential direction TC and extend in a zigzag manner in the tire circumferential direction TC. The center circumferential direction groove 12 includes projections 50 composed of a plurality of first projections 50a and a plurality of second projections 50b, in which the plurality of first projections 50a and the plurality of second projections 50b are alternately arranged in the tire circumferential direction TC. The respective first projections 50a are bent in the protruding manner in the tire axial direction TW1 in the respective first bent parts 12a, and the respective second projections 50b are bent in the protruding manner on the other side in the tire axial direction in the respective second bent parts 12b.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a pneumatic tire. [Background technology]

[0002] 2. Description of the Related Art Conventionally, pneumatic tires are known in which protrusions are arranged at the bottoms of grooves formed in the tread in order to suppress stone trapping in the grooves (see, for example, Patent Documents 1 to 5). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2008-296795 A [Patent Document 2] JP 2016-068635 A [Patent Document 3] JP 2012-056513 A [Patent Document 4] Japanese Patent Application Publication No. 6-183212 [Patent Document 5] Japanese Patent Application Publication No. 11-180112 Summary of the Invention [Problem to be solved by the invention]

[0004] Conventional pneumatic tires have room for improvement in terms of suppressing damage from lugs.

[0005] An object of the present invention is to provide a pneumatic tire capable of suppressing damage to protrusions. [Means for solving the problem]

[0006] One aspect of the present invention is The tread has a plurality of first bent portions bent in a convex shape toward one side in the tire axial direction and a plurality of second bent portions bent in a convex shape toward the other side in the tire axial direction, and the plurality of first bent portions and the plurality of second bent portions are alternately arranged in the tire circumferential direction, and the main groove extends in a zigzag shape along the tire circumferential direction, The main groove is A pair of groove wall surfaces extending radially inward from the tread surface of the tread; a groove bottom surface connecting the tire radial direction inner ends of the pair of groove wall surfaces; a plurality of first protrusions and a plurality of second protrusions arranged at intervals from the pair of groove wall surfaces and protruding from the groove bottom surface toward an outer side in the tire radial direction, the plurality of first protrusions and the plurality of second protrusions being arranged alternately along the tire circumferential direction; Equipped with One of the pair of groove wall surfaces has a wall surface extending from the tread surface toward the tire radial direction inward so as to approach the other of the pair of groove wall surfaces in the tire axial direction, The present invention provides a pneumatic tire, in which each first projection is bent convexly toward one side in the tire axial direction at each first bent portion, and each second projection is bent convexly toward the other side in the tire axial direction at each second bent portion.

[0007] According to this configuration, since the first projection is bent in a convex shape toward one side in the tire axial direction, the rigidity of the first projection can be increased compared to when the first projection extends linearly. Similarly, since the second projection is bent in a convex shape toward the other side in the tire axial direction, the rigidity of the second projection can be increased compared to when the second projection extends linearly. This makes it possible to prevent the first projection and the second projection from being damaged due to excessive deformation. As a result, it is possible to prevent damage to the projection consisting of the first projection and the second projection.

[0008] In addition, according to this configuration, one of the pair of groove wall surfaces has a wall surface that extends from the tread surface toward the tire radial direction inward so as to approach the other of the pair of groove wall surfaces. This allows stones in the main groove to roll along the wall surface and be easily discharged from the main groove, thereby preventing the stones from getting stuck in the main groove. As a result, the stones are prevented from coming into contact with the protrusions, and damage to the protrusions is prevented.

[0009] Also, according to this configuration, the protrusions are configured such that the first protrusions bent along the first bend portion and the second protrusions bent along the second bend portion are alternately arranged along the tire circumferential direction. This makes it possible to reduce the load applied to the protrusions when the pneumatic tire contacts the road surface during cornering or the like and the tread is twisted, thereby suppressing damage to the protrusions. Effect of the Invention

[0010] According to the present invention, a pneumatic tire capable of suppressing damage to protrusions can be provided. [Brief description of the drawings]

[0011] [Figure 1] 1 is a schematic diagram of a tread of a pneumatic tire according to an embodiment of the present invention, viewed from the radially outer side. [Diagram 2] FIG. 2 is a radial cross-sectional view of the tire taken along line II in FIG. [Diagram 3] FIG. 2 is a radial cross-sectional view of the tire taken along line III in FIG. 1 . [Figure 4] FIG. 2 is a radial cross-sectional view of the tire taken along line IV in FIG. 1 . [Diagram 5] FIG. 2 is a radial cross-sectional view of the tire taken along line V in FIG. [Figure 6] FIG. 2 is a radial cross-sectional view of the tire taken along line VI in FIG. 1 . [Figure 7] FIG. 7 is a radial cross-sectional view of the tire taken along line VII in FIG. [Figure 8] FIG. 8 is a radial cross-sectional view of the tire taken along line VIII in FIG. [Figure 9] FIG. 2 is a radial cross-sectional view of the tire taken along line IX in FIG. 1 . [Figure 10] FIG. 2 is a radial cross-sectional view of the tire taken along line X in FIG. 1 . DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0013] FIG. 1 is a schematic diagram of a tread of a pneumatic tire (hereinafter, simply referred to as "tire") according to one embodiment of the present invention, viewed from the radial outside. The tire 1 of this embodiment is configured as a heavy-duty rubber tire. Heavy-duty tires are tires defined in the JATMA YEAR BOOK (Chapter C: for trucks and buses, Chapter D: for construction vehicles). In this embodiment, the left-right direction in FIG. 1 is referred to as the tire axial direction TW, and the up-down direction in FIG. 1 is referred to as the tire circumferential direction TC. In particular, within the tire axial direction TW, the rightward direction in FIG. 1 is referred to as TW1, and the leftward direction in FIG. 1 is referred to as TW2. Also, within the tire circumferential direction TC, the upward direction in FIG. 1 is referred to as TC1, and the downward direction in FIG. 1 is referred to as TC2.

[0014] [Tire structure] The tire 1 has a tread 11 extending in the tire circumferential direction TC so as to extend cylindrically around the axis of the tire 1, and ground contact edges 11a, 11b located at both ends in the tire axial direction TW of the tread 11. The tread 11 is located at the outer end in the tire radial direction, and has a tread surface 11c that is a contact surface that comes into contact with the ground when the tire rolls.

[0015] The tread 11 has a center circumferential groove 12 extending in a zigzag manner in the tire circumferential direction TC, and a pair of shoulder circumferential grooves 13a, 13b extending in a zigzag manner in the tire circumferential direction TC, located on both sides in the tire axial direction TW of the center circumferential groove 12. The center circumferential groove 12 and the pair of shoulder circumferential grooves 13a, 13b are each recessed from the tread surface 11c toward the tire radially inward.

[0016] The center circumferential groove 12 is located on the center side of the tread 11 in the tire axial direction TW. In this embodiment, the center circumferential groove 12 is located on the tire equator CL, but it does not necessarily have to be located on the tire equator CL. The center circumferential groove 12 extends in a zigzag shape along the tire circumferential direction TC. Specifically, the center circumferential groove 12 has a plurality of first bent portions 12a bent in a convex shape in the tire axial direction TW1 and a plurality of second bent portions 12b bent in a convex shape in the tire axial direction TW2. The plurality of first bent portions 12a and the plurality of second bent portions 12b are alternately arranged along the tire circumferential direction TC.

[0017] The central circumferential groove 12 includes a pair of groove wall surfaces 30A, 30B, a groove bottom surface 40 connecting radially inner ends of the pair of groove wall surfaces 30A, 30B, and a protrusion 50 protruding radially outward from the groove bottom surface 40. In the following description, when there is no need to particularly distinguish between the pair of groove wall surfaces 30A, 30B, one of the pair of groove wall surfaces 30A, 30B may be simply referred to as groove wall surface 30.

[0018] The groove wall surface 30 extends in a zigzag shape along the tire circumferential direction TC. Specifically, the groove wall surface 30 is bent in a convex shape in the tire axial direction TW1 at the first bent portion 12a, and is bent in a convex shape in the tire axial direction TW2 at the second bent portion 12b.

[0019] The protrusion 50 extends in a zigzag manner along the tire circumferential direction TC. In other words, the protrusion 50 extends along the extension direction of the central circumferential groove 12. Specifically, the protrusion 50 is bent in a convex manner in the tire axial direction TW1 at the first bent portion 12a, and is bent in a convex manner in the tire axial direction TW2 at the second bent portion 12b.

[0020] The protrusion 50 is divided at a predetermined interval in the tire circumferential direction TC. Specifically, the protrusion 50 is composed of a plurality of first protrusions 50a and a plurality of second protrusions 50b arranged at intervals in the tire circumferential direction TC. Each of the first protrusions 50a is bent in a convex shape in the tire axial direction TW1 at the first bend portion 12a. Each of the second protrusions 50b is bent in a convex shape in the tire axial direction TW2 at the second bend portion 12b. The first protrusions 50a and the second protrusions 50b are alternately arranged along the tire circumferential direction TC, so that the protrusion 50 extends in a zigzag shape along the tire circumferential direction TC as a whole. Each of the first protrusions 50a and each of the second protrusions 50b are arranged at an interval d along the direction in which the center circumferential groove 12 extends. In this embodiment, the interval d is set to 2.5 mm. The interval d is preferably 11% or more and 16% or less of the length of the first projection 50a or the second projection 50b along the direction in which the center circumferential groove 12 extends.

[0021] Fig. 2 is a tire radial cross-sectional view taken along line II in Fig. 1, showing a cross-section of the central circumferential groove 12. The central circumferential groove 12 has a groove depth D1 of a predetermined dimension. In this embodiment, the dimension of the groove depth D1 is set to 17 mm.

[0022] The groove wall surface 30 extends radially inward from the tread surface 11c. Specifically, the groove wall surface 30 includes a first wall surface 31 extending from the tread surface 11c along the tire radial direction, and a second wall surface 32 extending from the groove bottom surface 40 along the tire radial direction.

[0023] The first wall surface 31 of this embodiment extends from the tread surface 11c toward the tire radially inward, inclining toward the center of the center circumferential groove 12 in the tire axial direction TW. Specifically, the first wall surface 31 of the groove wall surface 30A extends from the tread surface 11c toward the tire radially inward, inclining toward the groove wall surface 30B in the tire axial direction TW, i.e., in a linear manner in the tire axial direction TW2. The first wall surface 31 of the groove wall surface 30B extends from the tread surface 11c toward the tire radially inward, inclining toward the groove wall surface 30A in the tire axial direction TW, i.e., in a linear manner in the tire axial direction TW1.

[0024] In this embodiment, the inclination angle θ1 of the first wall surface 31 with respect to the tire radial direction is 10° in a cross section (for example, the cross section shown in FIG. 2) perpendicular to the extension direction of the central circumferential groove 12. The inclination angle θ1 of the first wall surface 31 with respect to the tire radial direction is preferably 5° or more and 15° or less in a cross section perpendicular to the extension direction of the central circumferential groove 12.

[0025] In this embodiment, the dimension H1 of the first wall surface 31 in the tire radial direction is 65% of the dimension of the central circumferential groove 12 in the tire radial direction, i.e., the groove depth D1. The dimension H1 of the first wall surface 31 in the tire radial direction is preferably 60% or more and 70% or less of the groove depth D1 of the central circumferential groove 12.

[0026] The first wall surface 31 in this embodiment is a straight line inclined from the tread surface 11c, but is not limited thereto. The first wall surface 31 may extend from the tread surface 11c toward the tire radially inward so as to approach the center of the center circumferential groove 12 in the tire axial direction TW as a whole. For example, the first wall surface 31 may extend from the tread surface 11c toward the tire radially inward in parallel with the tire radial direction, and then extend toward the tire radially inward at an incline toward the center of the center circumferential groove 12 in the tire axial direction TW. In other words, the first wall surface 31 may have a vertical wall portion extending from the tread surface 11c toward the tire radially inward in parallel with the tire radial direction, and an inclined portion extending from the tire radially inner end of the vertical wall portion toward the tire radially inward at an incline toward the center of the center circumferential groove 12 in the tire axial direction TW.

[0027] The second wall surface 32 of this embodiment is disposed in continuity with the groove bottom surface 40 and extends outward in the tire radial direction, inclined away from the center of the center circumferential groove 12 in the tire axial direction TW. In other words, the second wall surface 32 extends inward in the tire radial direction, inclined toward the center of the center circumferential groove 12 in the tire axial direction TW. Specifically, the second wall surface 32 of the groove wall surface 30A extends inward in the tire radial direction, inclined linearly toward the groove wall surface 30B in the tire axial direction TW2. The second wall surface 32 of the groove wall surface 30B extends inward in the tire radial direction, inclined linearly toward the groove wall surface 30A in the tire axial direction TW1.

[0028] In this embodiment, the inclination angle θ2 of the second wall surface 32 with respect to the tire radial direction is 5° in a cross section (for example, the cross section shown in FIG. 2) perpendicular to the extension direction of the central circumferential groove 12. The inclination angle θ2 of the second wall surface 32 with respect to the tire radial direction is preferably 0° or more and 5° or less in a cross section perpendicular to the extension direction of the central circumferential groove 12.

[0029] In this embodiment, the tire radial direction outer end of the second wall surface 32 is connected to the tire radial direction inner end 31a of the first wall surface 31. That is, the second wall surface 32 in this embodiment is continuous with the first wall surface 31.

[0030] The protrusion 50 protrudes from the groove bottom surface 40 toward the tire radial direction outside. In this embodiment, the protrusion 50 is rectangular in a cross section perpendicular to the direction in which the central circumferential groove 12 extends (for example, the cross section shown in FIG. 2). The protrusion 50 includes a pair of side surfaces 51A, 51B extending from the groove bottom surface 40 toward the tire radial direction outside, and an upper surface 52 connecting the tire radial direction outer ends of the pair of side surfaces 51A, 51B. In the following description, when there is no need to particularly distinguish between the pair of side surfaces 51A, 51B, one of them may be simply referred to as side surface 51.

[0031] An upper surface 52 of the protrusion 50, i.e., an outer end of the protrusion 50 in the tire radial direction, is located radially inward of an inner end 31a of the first wall surface 31 in the tire radial direction. In this embodiment, the dimension in the tire radial direction of the protrusion 50, i.e., the height H2, is 20% of the dimension in the tire radial direction of the central circumferential groove 12, i.e., the groove depth D1. The height H2 of the protrusion 50 is preferably 15% or more and 30% or less of the groove depth D1 of the central circumferential groove 12.

[0032] The side surface 51A is disposed opposite the groove wall surface 30A. The side surface 51B is disposed opposite the groove wall surface 30B. The side surface 51 extends from the groove bottom surface 40 toward the tire radial outside, inclining toward the center of the center circumferential groove 12 in the tire axial direction TW. Specifically, the side surface 51A extends from the groove bottom surface 40 toward the tire radial outside, inclining in the tire axial direction TW2. The side surface 51B extends from the groove bottom surface 40 toward the tire radial outside, inclining in the tire axial direction TW1. The inclination angle θ3 of the side surface 51 with respect to the tire radial direction is 5° in a cross section (for example, the cross section shown in FIG. 2) perpendicular to the direction in which the center circumferential groove 12 extends. The inclination angle θ3 of the side surface 51 with respect to the tire radial direction is preferably 0° or more and 5° or less in a cross section (for example, the cross section shown in FIG. 2) perpendicular to the direction in which the center circumferential groove 12 extends. The space between the side surface 51 and the groove wall surface 30 is defined so as to gradually increase in size toward the outside in the tire radial direction.

[0033] The groove bottom surface 40 is disposed adjacent to each of the groove wall surfaces 30A and 30B, and includes a pair of first curved surfaces 41A and 41B that extend in a curved manner in a cross section (for example, the cross section shown in FIG. 2) perpendicular to the direction in which the central circumferential groove 12 extends. When there is no need to particularly distinguish between the pair of first curved surfaces 41A and 41B, one of them may be simply referred to as the first curved surface 41. The first curved surface 41A extends from the groove wall surface 30A toward the tire radially inward in a concave curve in the tire axial direction TW2. The first curved surface 41B extends from the groove wall surface 30B toward the tire radially inward in a concave curve in the tire axial direction TW1.

[0034] The groove bottom surface 40 is provided with a pair of second curved surfaces 42A, 42B that are arranged to be continuous with the side surfaces 51A, 51B of the protrusion 50 and extend in a curved manner in a cross section (for example, the cross section shown in FIG. 2) perpendicular to the direction in which the central circumferential groove 12 extends. When there is no need to particularly distinguish between the pair of second curved surfaces 42A, 42B, one of them may be simply referred to as the second curved surface 42. The second curved surface 42A extends from the side surface 51A of the protrusion 50 toward the tire radially inward in a concave curve in the tire axial direction TW1. The second curved surface 42B extends from the side surface 51B of the protrusion 50 toward the tire radially inward in a concave curve in the tire axial direction TW2.

[0035] The second curved surface 42 in this embodiment is disposed continuous with the first curved surface 41. In addition, in a cross section perpendicular to the direction in which the central circumferential groove 12 extends (for example, the cross section shown in FIG. 2), the curvature of the second curved surface 42 is smaller than the curvature of the first curved surface 41. In other words, in a cross section perpendicular to the direction in which the central circumferential groove 12 extends (for example, the cross section shown in FIG. 2), the curvature radius r1 of the first curved surface 41 is larger than the curvature radius r2 of the second curved surface 42.

[0036] Fig. 3 is a radial cross-sectional view of the tire taken along line III in Fig. 1, showing a cross section of the pair of shoulder circumferential grooves 13a, 13b. The pair of shoulder circumferential grooves 13a, 13b have a groove depth D2 of a predetermined dimension.

[0037] As shown in Fig. 1, the tread 11 has a pair of center lands 14a, 14b defined between the center circumferential groove 12 and the pair of shoulder circumferential grooves 13a, 13b. The tread 11 also has a plurality of first center dividing grooves 15 and a plurality of second center dividing grooves 16 that are alternately arranged at intervals in the tire circumferential direction TC and extend in the tire axial direction TW between the center circumferential groove 12 and the pair of shoulder circumferential grooves 13a, 13b so as to divide the pair of center lands 14a, 14b in the tire circumferential direction TC. The plurality of first center dividing grooves 15 and the plurality of second center dividing grooves 16 are respectively connected to the center circumferential groove 12 and the pair of shoulder circumferential grooves 13a, 13b.

[0038] The first center dividing groove 15 extends from the tire axial direction TW2 toward the tire axial direction TW1, and is inclined from the tire circumferential direction TC2 toward the tire circumferential direction TC1. The second center dividing groove 16 extends in a zigzag manner from the tire axial direction TW2 toward the tire axial direction TW1, and is inclined from the tire circumferential direction TC1 toward the tire circumferential direction TC2. At least three or more small grooves inclined at different angles to the tire axial direction TW are connected to each other, so that the second center dividing groove 16 extends in a zigzag manner in the tire axial direction TW. In this embodiment, the second center dividing groove 16 has a first dividing small groove 16a, a second dividing small groove 16b, and a third dividing small groove 16c inclined at different angles to the tire axial direction TW from the tire axial direction TW2 toward the tire axial direction TW1, and the first dividing small groove 16a, the second dividing small groove 16b, and the third dividing small groove 16c are connected to each other, so that the second center dividing groove 16 extends in a zigzag manner in the tire axial direction TW.

[0039] Each of the pair of shoulder circumferential grooves 13a, 13b has a plurality of small grooves inclined at different angles with respect to the tire circumferential direction TC, and the plurality of small grooves are connected to each other to form a zigzag shape in the tire circumferential direction TC. In particular, each of the pair of shoulder circumferential grooves 13a, 13b has a first shoulder circumferential small groove 13c that extends from the tire circumferential direction TC2 to the tire circumferential direction TC1 at a position where the pair of shoulder circumferential grooves 13a, 13b communicate with the plurality of first center dividing grooves 15 and inclines from the tire axial direction TW2 to the tire axial direction TW1. Also, each of the pair of shoulder circumferential grooves 13a, 13b has a second shoulder circumferential small groove 13d that extends from the tire circumferential direction TC2 to the tire circumferential direction TC1 at a position where the pair of shoulder circumferential grooves 13a, 13b communicate with the plurality of second center dividing grooves 16 and inclines from the tire axial direction TW2 to the tire axial direction TW1. The angle A1 at which the first shoulder circumferential small groove 13c is inclined with respect to the tire axial direction TW is the same as the angle A2 at which the second shoulder circumferential small groove 13d is inclined with respect to the tire axial direction TW.

[0040] Each of the pair of center lands 14a, 14b has a first center dividing land 14c and a second center dividing land 14d that are divided in the tire circumferential direction TC by a plurality of first center dividing grooves 15 and a plurality of second center dividing grooves 16. The first center dividing land 14c has a length dimension along the tire circumferential direction TC in the tire axial direction TW1 that is greater than the length dimension along the tire circumferential direction TC in the tire axial direction TW2. The second center dividing land 14d has a length dimension along the tire circumferential direction TC in the tire axial direction TW1 that is smaller than the length dimension along the tire circumferential direction TC in the tire axial direction TW2. The first center dividing land 14c and the second center dividing land 14d are alternately positioned in the tire circumferential direction TC so as to be adjacent to each other in the pair of center lands 14a, 14b.

[0041] Fig. 4 is a tire radial cross-sectional view taken along line IV in Fig. 1, showing a cross-section of the first center dividing groove 15. The first center dividing groove 15 has a groove depth D3 from the tread surface 11c to the groove bottom. The dimension of the groove depth D3 of the first center dividing groove 15 is set to 15 to 20% of the dimension of the groove depth D1 of the central circumferential groove 12. In this embodiment, the dimension of the groove depth D3 of the first center dividing groove 15 is set to 2.9 mm.

[0042] The first center dividing groove 15 has a first sipe 17 at its groove bottom, which extends in the tire axial direction TW along the first center dividing groove 15. The first sipe 17 has a groove depth D4 from the tread surface 11c to the groove bottom. The dimension of the groove depth D4 of the first sipe 17 is set to 80 to 90% of the dimension of the groove depth D1 of the central circumferential groove 12. In this embodiment, the dimension of the groove depth D4 of the first sipe 17 is set to 15.2 mm.

[0043] Fig. 5 is a radial cross-sectional view of the tire taken along line V in Fig. 1, showing a cross-section of the first sipe 17. The first sipe 17 has a stepped shape in which the groove bottoms on both ends in the tire axial direction TW are positioned higher than the groove bottom on the center side. Therefore, the groove depth of the first sipe 17 at the center in the tire axial direction TW is deeper than the groove depth at both ends in the tire axial direction TW.

[0044] 1, the first sipe 17 has bent portions 17a at both ends in the tire axial direction TW that are substantially perpendicular to the center circumferential groove 12 or the shoulder circumferential grooves 13a, 13b. The state in which the bent portions 17a are substantially perpendicular to the center circumferential groove 12 or the shoulder circumferential grooves 13a, 13b means that the bent portions 17a intersect with the center circumferential groove 12 or the shoulder circumferential grooves 13a, 13b at an angle of 85 degrees or more and 92 degrees or less.

[0045] Fig. 6 is a tire radial cross-sectional view taken along line VI in Fig. 1, showing a cross-section of the second center dividing groove 16. The second center dividing groove 16 has a groove depth D5 from the tread surface 11c to the groove bottom. The dimension of the groove depth D5 of the second center dividing groove 16 is set to 15 to 20% of the dimension of the groove depth D1 of the central circumferential groove 12. In this embodiment, the dimension of the groove depth D5 of the second center dividing groove 16 is set to 2.9 mm.

[0046] The second center dividing groove 16 has, at its groove bottom, a second sipe 18 extending in the tire axial direction TW along the second center dividing groove 16. The second sipe 18 has a groove depth D6 from the tread surface 11c to the groove bottom. The dimension of the groove depth D6 of the second sipe 18 is set to 80 to 90% of the dimension of the groove depth D1 of the central circumferential groove 12. In this embodiment, the dimension of the groove depth D6 of the second sipe 18 is set to 15.2 mm.

[0047] Fig. 7 is a tire radial cross-sectional view taken along line VII in Fig. 1, showing a cross-section of the second sipe 18. The second sipe 18 has a shape with a uniform groove depth. Therefore, the groove depth of the second sipe 18 at the center in the tire axial direction TW is approximately equal to the groove depth at both ends in the tire axial direction TW.

[0048] As shown in FIG. 1, the length of the second sipes 18 in the tire axial direction TW is shorter than the length of the first sipes 17 in the tire axial direction TW.

[0049] The first center dividing land 14c has a first narrow groove 19a that extends in the tire circumferential direction TC1 from the end of the second dividing small groove 16b located in the center of the second center dividing groove 16 in the tire axial direction TW1, inclined in the tire axial direction TW2 toward the center of the first center dividing land 14c, and closed at the center of the first center dividing land 14c. The second center dividing land 14d has a second narrow groove 19b that extends in the tire circumferential direction TC2 from the end of the second dividing small groove 16b located in the center of the second center dividing groove 16 in the tire axial direction TW2, inclined in the tire axial direction TW1 toward the center of the second center dividing land 14d, and closed at the center of the second center dividing land 14d. The first narrow groove 19a and the second narrow groove 19b extend parallel to each other and have the same dimensions of groove width and groove depth.

[0050] The minimum distance D7 between the first narrow groove 19a and the second narrow groove 19b in the tire axial direction TW is within 2 mm. In this embodiment, the minimum distance D7 between the first narrow groove 19a and the second narrow groove 19b in the tire axial direction TW is set to 2 mm.

[0051] 8 is a tire radial cross-sectional view taken along line VIII in FIG. 1, showing a cross-section of the first narrow groove 19a. The first narrow groove 19a has a groove depth D8 from the tread surface 11c to the groove bottom. The dimension of the groove depth D8 of the first narrow groove 19a is within 1 mm. In this embodiment, the dimension of the groove depth D8 of the first narrow groove 19a is set to 1 mm. The second narrow groove 19b also has a cross-sectional shape similar to that of the first narrow groove 19a.

[0052] As shown in Fig. 1, the tread 11 has a pair of shoulder lands 20a, 20b defined between the pair of shoulder circumferential grooves 13a, 13b and the ground contact ends 11a, 11b of the tread 11. The tread 11 also has a plurality of shoulder dividing grooves 21 arranged alternately at intervals in the tire circumferential direction TC and extending in a zigzag pattern in the tire axial direction TW between the pair of shoulder circumferential grooves 13a, 13b and the ground contact ends 11a, 11b of the tread 11. The angle A3 at which the zigzag shape of the shoulder dividing groove 21 is inclined with respect to the tire axial direction TW is larger than the angles A1, A2 at which the zigzag shape of the shoulder circumferential grooves 13a, 13b is inclined with respect to the tire circumferential direction.

[0053] Fig. 9 is a tire radial cross-sectional view taken along line IX in Fig. 1, showing a cross-section of the shoulder dividing groove 21. The shoulder dividing groove 21 has, at the groove bottom, a shoulder sipe 22 extending in the tire axial direction along the shoulder dividing groove 21. As shown in Fig. 1, the shoulder sipe 22 is divided in the tire axial direction and has a first divided sipe 22a and a second divided sipe 22b.

[0054] Fig. 10 is a tire radial cross-sectional view taken along line X in Fig. 1, showing a cross-section of the shoulder sipe 22. The first divided sipe 22a and the second divided sipe 22b each have a shape with a uniform groove depth. The length of the second divided sipe 22b in the tire axial direction is longer than the length of the first divided sipe 22a in the tire axial direction.

[0055] [Effects] The tire 1 thus constructed has the following features.

[0056] Tire 1 is The tread 11 has a plurality of first bent portions 12a bent in a convex shape in a tire axial direction TW1 and a plurality of second bent portions 12b bent in a convex shape in a tire axial direction TW2, and is provided with a center circumferential groove 12 in which the plurality of first bent portions 12a and the plurality of second bent portions 12b are alternately arranged in the tire circumferential direction TC and extend in a zigzag shape along the tire circumferential direction TC, The center circumferential groove 12 is A pair of groove wall surfaces 30A, 30B extending radially inward from the tread surface 11c of the tread 11; A groove bottom surface 40 connecting the tire radial direction inner ends of the pair of groove wall surfaces 30A, 30B; a protrusion 50 including a plurality of first protrusions 50a and a plurality of second protrusions 50b arranged at intervals from a pair of groove wall surfaces 30A, 30B and protruding from a groove bottom surface 40 toward the tire radial direction outside, the plurality of first protrusions 50a and the plurality of second protrusions 50b being arranged alternately along the tire circumferential direction TC; Equipped with One groove wall surface 30A of the pair of groove wall surfaces 30A, 30B has a first wall surface 31 extending from the tread surface 11c toward the tire radially inward and toward the other groove wall surface 30B of the pair of groove wall surfaces 30A, 30B in the tire axial direction TW, Each of the first projections 50a is bent in a convex shape toward the tire axial direction TW1 at each of the first bent portions 12a, and each of the second projections 50b is bent in a convex shape toward the other side in the tire axial direction at each of the second bent portions 12b.

[0057] According to this configuration, since the first protrusion 50a is bent in a convex shape in the tire axial direction TW1, the rigidity of the first protrusion 50a can be increased compared to when the first protrusion 50a extends linearly. Similarly, since the second protrusion 50b is bent in a convex shape in the tire axial direction TW2, the rigidity of the second protrusion 50b can be increased compared to when the second protrusion 50b extends linearly. This makes it possible to prevent the first protrusion 50a and the second protrusion 50b from being damaged due to excessive deformation. As a result, it is possible to prevent damage to the protrusion 50 consisting of the first protrusion 50a and the second protrusion 50b.

[0058] Also, according to this configuration, one of the pair of groove wall surfaces 30A, 30B has a first wall surface 31 that extends from the tread surface 11c toward the tire radial inside so as to approach the other of the pair of groove wall surfaces 30A, 30B. As a result, stones in the center circumferential groove 12 roll along the first wall surface 31, making it easier to be discharged from the center circumferential groove 12, and it is possible to prevent the stones from getting caught in the center circumferential groove 12. As a result, the stones are prevented from coming into contact with the protrusion 50, and therefore damage to the protrusion 50 can be prevented.

[0059] Also, according to this configuration, the protrusion 50 is configured such that the first protrusion 50a bent along the first bent portion 12a and the second protrusion 50b bent along the second bent portion 12b are alternately arranged along the tire circumferential direction TC. This makes it possible to reduce the load applied to the protrusion 50 when the tire 1 contacts the road surface during cornering or the like and the tread surface 11c is twisted, thereby suppressing damage to the protrusion 50.

[0060] An outer end of the protrusion 50 in the tire radial direction is located more inward in the tire radial direction than an inner end 31a of the first wall surface 31 in the tire radial direction.

[0061] According to this configuration, the outer end of the protrusion 50 in the tire radial direction is located radially inward of the inner end of the first wall surface 31 in the tire radial direction, so that stones that are caught in the center circumferential groove 12 and lodged on the first wall surface 31 are prevented from coming into contact with the protrusion 50. As a result, damage to the protrusion 50 can be suppressed.

[0062] In addition, since the outer end of the protrusion 50 in the tire radial direction is located radially inward of the inner end 31a of the first wall surface 31 in the tire radial direction, it is possible to prevent the rigidity of the protrusion 50 from being excessively reduced. As a result, damage to the protrusion 50 can be suppressed.

[0063] A dimension H1 of the first wall surface 31 in the tire radial direction is 60% or more and 70% or less of the dimension of the central circumferential groove 12 in the tire radial direction, that is, the groove depth D1 of the central circumferential groove 12.

[0064] Since the dimension H1 of the first wall surface 31 in the tire radial direction is 60% or more of the dimension of the center circumferential groove 12 in the tire radial direction, i.e., the groove depth D1 of the center circumferential groove 12, the first wall surface 31 is disposed over a wider range in the tire radial direction compared to the case where the dimension H1 of the first wall surface 31 in the tire radial direction is less than 60% of the dimension D1 of the center circumferential groove 12 in the tire radial direction. As a result, stones in the center circumferential groove 12 roll along the first wall surface 31, making it easier to be discharged from the center circumferential groove 12, and it is possible to further suppress the stones from getting stuck in the center circumferential groove 12. In addition, since the dimension H1 of the first wall surface 31 in the tire radial direction is 70% or less of the dimension D1 of the center circumferential groove 12 in the tire radial direction, the width of the groove bottom surface 40 is not excessively narrowed. As a result, it is possible to suppress the width of the protrusion 50 from being excessively narrowed and the rigidity of the protrusion 50 from being excessively reduced. As a result, it is possible to suppress damage to the protrusion 50. Therefore, according to this configuration, the tire radial dimension H1 of the first wall surface 31 is 60% or more and 70% or less of the tire radial dimension D1 of the center circumferential groove 12, so that damage to the protrusion 50 can be further suppressed while suppressing stone entrapment in the center circumferential groove 12.

[0065] The inclination angle θ1 of the first wall surface 31 with respect to the tire radial direction is equal to or greater than 5° and equal to or less than 15° in a cross section perpendicular to the direction in which the central circumferential groove 12 extends.

[0066] Since the inclination angle θ1 of the first wall surface 31 with respect to the tire radial direction is 5° or more in a cross section perpendicular to the direction in which the center circumferential groove 12 extends, stones in the center circumferential groove 12 are easily discharged from the center circumferential groove 12, and the stones can be further prevented from getting caught in the center circumferential groove 12. In addition, since the inclination angle θ1 of the first wall surface 31 with respect to the tire radial direction is 15° or less in a cross section perpendicular to the direction in which the center circumferential groove 12 extends, the width of the groove bottom surface 40 does not become excessively narrow. As a result, the width of the protrusion 50 is prevented from becoming excessively narrow and the rigidity of the protrusion 50 is prevented from becoming excessively low. As a result, damage to the protrusion 50 can be suppressed. According to this configuration, since the inclination angle θ1 of the first wall surface 31 with respect to the tire radial direction is 5° or more and 15° or less in a cross section perpendicular to the direction in which the center circumferential groove 12 extends, damage to the protrusion 50 can be further suppressed while suppressing the stones from getting caught in the center circumferential groove 12.

[0067] A dimension H2 of the protrusion 50 in the tire radial direction is 15% to 30% of a dimension D1 of the central circumferential groove 12 in the tire radial direction.

[0068] Since the dimension H2 of the protrusion 50 in the tire radial direction is 15% or more of the dimension D1 of the center circumferential groove 12 in the tire radial direction, stones in the center circumferential groove 12 can be prevented from getting caught in the center circumferential groove 12 without coming into contact with the protrusion 50. Furthermore, since the dimension H2 of the protrusion 50 in the tire radial direction is 30% or less of the dimension D1 of the center circumferential groove 12 in the tire radial direction, the rigidity of the protrusion 50 can be prevented from being excessively reduced. As a result, damage to the protrusion 50 can be prevented. According to this configuration, since the dimension H2 of the protrusion 50 in the tire radial direction is 15% or more and 30% or less of the dimension D1 of the center circumferential groove 12 in the tire radial direction, stones in the center circumferential groove 12 can be prevented from getting caught in the center circumferential groove 12 without coming into contact with the protrusion 50, damage to the protrusion 50 can be further prevented.

[0069] The protrusion 50 has a side surface 51 that extends from the groove bottom surface 40 toward the tire radial direction outside so as to approach the center of the central circumferential groove 12 in the tire axial direction TW, The inclination angle θ3 of the side surface 51 with respect to the tire radial direction is equal to or greater than 0° and equal to or less than 5° in a cross section perpendicular to the direction in which the central circumferential groove 12 extends.

[0070] According to this configuration, the inclination angle θ3 of the side surface of the protrusion 50 with respect to the tire radial direction is 0° or more and 5° or less in a cross section perpendicular to the extending direction of the central circumferential groove 12, so that it is possible to prevent the rigidity of the protrusion 50 from being excessively reduced. As a result, it is possible to prevent damage to the protrusion 50.

[0071] The protrusion 50 is disposed opposite one of the groove wall surfaces 30A and has a side surface 51A extending from the groove bottom surface 40 toward the outside in the tire radial direction, The groove bottom surface 40 is a first curved surface 41A that is arranged in connection with one of the groove wall surfaces 30A and extends in a curved manner; a second curved surface 42B that is arranged adjacent to the side surface 51A and extends with a curvature larger than that of the first curved surface 41A; Equipped with.

[0072] According to this configuration, the groove bottom surface 40 is arranged in continuity with the groove wall surface 30A and has a first curved surface 41A that extends in a curved manner, so that it is possible to suppress the occurrence of cracks starting from the connection part of the groove bottom surface 40 with the groove wall surface 30A. In addition, the groove bottom surface 40 is arranged in continuity with the side surface 51A of the protrusion 50 and has a second curved surface 42A that extends in a curved manner, so that it is possible to suppress the occurrence of cracks starting from the connection part of the groove bottom surface 40 with the side surface 51A of the protrusion 50. In addition, since the curvature of the second curved surface 42A is larger than the curvature of the first curved surface 41A, it is possible to suppress the width of the protrusion 50 from being excessively narrowed and the rigidity of the protrusion 50 from being excessively reduced. As a result, it is possible to suppress damage to the protrusion 50.

[0073] One groove wall surface 30A is disposed adjacent to the groove bottom surface 40 and has a second wall surface 32 extending toward the tire radially inward direction so as to approach the other groove wall surface 30B of the pair of groove wall surfaces 30A, 30B in the tire axial direction TW. The inclination angle θ2 of the second wall surface 32 with respect to the tire radial direction is equal to or greater than 0° and equal to or less than 5° in a cross section perpendicular to the direction in which the central circumferential groove 12 extends.

[0074] According to this configuration, one of the pair of groove wall surfaces 30A, 30B has a second wall surface 32 that is disposed continuous with the groove bottom surface 40 and extends toward the tire radially inward so as to approach the other of the pair of groove wall surfaces 30A, 30B. This allows stones in the center circumferential groove 12 to roll along the second wall surface 32, making it easier to be discharged from the center circumferential groove 12, and thus making it possible to prevent stones from getting caught in the center circumferential groove 12. As a result, stones are prevented from coming into contact with the protrusion 50, and therefore damage to the protrusion 50 can be prevented.

[0075] In addition, since the inclination angle θ2 of the second wall surface 32 with respect to the tire radial direction is 0° or more and 5° or less in a cross section perpendicular to the extending direction of the center circumferential groove 12, the width of the groove bottom surface 40 does not become excessively narrow. As a result, it is possible to prevent the width of the protrusion 50 from becoming excessively narrow and the rigidity of the protrusion 50 from becoming excessively low. As a result, it is possible to prevent damage to the protrusion 50.

[0076] [Other embodiments] The present invention is not limited to the configurations of the above-described embodiments, and various modifications are possible.

[0077] In the above embodiment, the center circumferential groove 12 has been described as an example of the main groove according to the present invention, but the main groove according to the present invention is not limited to the center circumferential groove 12 and may be the shoulder circumferential grooves 13a, 13b. In other words, the protrusions according to the present invention may be disposed in the shoulder circumferential grooves 13a, 13b.

[0078] In the above embodiment, the tire 1 is configured as a rubber tire for heavy loads, but may be configured as a rubber tire for small trucks. A rubber tire for small trucks is a tire specified in the JATMA YEAR BOOK (Chapter B: For small trucks).

[0079] The first aspect of the present invention is The tread has a plurality of first bent portions bent in a convex shape toward one side in the tire axial direction and a plurality of second bent portions bent in a convex shape toward the other side in the tire axial direction, and the plurality of first bent portions and the plurality of second bent portions are alternately arranged in the tire circumferential direction, and the main groove extends in a zigzag shape along the tire circumferential direction, The main groove is A pair of groove wall surfaces extending radially inward from the tread surface of the tread; a groove bottom surface connecting the tire radial direction inner ends of the pair of groove wall surfaces; a plurality of first protrusions and a plurality of second protrusions arranged at intervals from the pair of groove wall surfaces and protruding from the groove bottom surface toward an outer side in the tire radial direction, the plurality of first protrusions and the plurality of second protrusions being arranged alternately along the tire circumferential direction; Equipped with One of the pair of groove wall surfaces has a wall surface extending from the tread surface toward the tire radial direction inward so as to approach the other of the pair of groove wall surfaces in the tire axial direction, The present invention provides a pneumatic tire, in which each first projection is bent convexly toward one side in the tire axial direction at each first bent portion, and each second projection is bent convexly toward the other side in the tire axial direction at each second bent portion.

[0080] A second aspect of the present invention is The present invention provides a pneumatic tire according to a first aspect, wherein an outer end of the protrusion in the tire radial direction is located more inward in the tire radial direction than an inner end of the wall surface in the tire radial direction.

[0081] A third aspect of the present invention is The present invention provides a pneumatic tire according to the first or second aspect, wherein a dimension of the wall surface in the tire radial direction is 60% to 70% of a dimension of the main groove in the tire radial direction.

[0082] A fourth aspect of the present invention is The present invention provides a pneumatic tire according to any one of first to third aspects, wherein an inclination angle of the wall surface with respect to the tire radial direction is 5° or more and 15° or less in a cross section perpendicular to a direction in which the main groove extends.

[0083] A fifth aspect of the present invention is The present invention provides a pneumatic tire according to any one of first to fourth aspects, wherein a dimension of the protrusion in the tire radial direction is 15% to 30% of a dimension of the main groove in the tire radial direction.

[0084] A sixth aspect of the present invention is a method for producing a composition comprising the steps of: the protrusion has a side surface that extends from the groove bottom surface toward the outside in the tire radial direction and is inclined so as to approach a center of the main groove in the tire axial direction, The present invention provides a pneumatic tire according to any one of first to fifth aspects, wherein an inclination angle of the side surface with respect to the tire radial direction is equal to or greater than 0° and equal to or less than 5° in a cross section perpendicular to a direction in which the main groove extends.

[0085] A seventh aspect of the present invention is a method for producing a composition comprising the steps of: the protrusion is disposed opposite the one groove wall surface and has a side surface extending from the groove bottom surface toward an outer side in the tire radial direction, The groove bottom surface is a first curved surface that is arranged in connection with the one groove wall surface and extends in a curved manner; a second curved surface that is arranged adjacent to the side surface and extends with a curvature smaller than that of the first curved surface; The present invention provides a pneumatic tire according to any one of the first to sixth aspects, comprising:

[0086] An eighth aspect of the present invention is a method for producing a composition comprising the steps of: The one groove wall surface has a second wall surface that is arranged continuous with the groove bottom surface and extends toward the tire radially inward direction so as to approach the other of the pair of groove wall surfaces in the tire axial direction, The present invention provides a pneumatic tire according to any one of the first to seventh aspects, wherein an inclination angle of the second wall surface with respect to the tire radial direction is not less than 0° and not more than 5° in a cross section perpendicular to a direction in which the main groove extends. [Explanation of symbols]

[0087] 1. Pneumatic tires 11 Tread 11c Tread 12 Center circumferential groove (main groove) 12a 1st bending part 12b 2nd bending part 30A,30B Groove wall surface 31 First Wall 31a end 32 Second Wall 40 Groove bottom surface 41 First curved surface 42 Second curved surface 50 protrusions 50a 1st protrusion 50b 2nd protrusion 51A,51B Side 52 Top side

Claims

1. The tread has a plurality of first bent portions bent in a convex shape toward one side in the tire axial direction and a plurality of second bent portions bent in a convex shape toward the other side in the tire axial direction, and the plurality of first bent portions and the plurality of second bent portions are alternately arranged in the tire circumferential direction, and the main groove extends in a zigzag shape along the tire circumferential direction, The main groove is A pair of groove wall surfaces extending radially inward from the tread surface of the tread; a groove bottom surface connecting the tire radial direction inner ends of the pair of groove wall surfaces; a plurality of first protrusions and a plurality of second protrusions arranged at intervals from the pair of groove wall surfaces and protruding from the groove bottom surface outward in the tire radial direction, the plurality of first protrusions and the plurality of second protrusions being arranged alternately along the tire circumferential direction; Equipped with One of the pair of groove wall surfaces has a wall surface extending from the tread surface toward the tire radial direction inward so as to approach the other of the pair of groove wall surfaces in the tire axial direction, A pneumatic tire, wherein each first projection is bent convexly toward one side in the tire axial direction at each first bend portion, and each second projection is bent convexly toward the other side in the tire axial direction at each second bend portion.

2. The pneumatic tire according to claim 1 , wherein an outer end of the protrusion in the tire radial direction is located inward in the tire radial direction with respect to an inner end of the wall surface in the tire radial direction.

3. The pneumatic tire according to claim 1 , wherein a dimension of the wall surface in a radial direction of the tire is 60% or more and 70% or less of a dimension of the main groove in the radial direction of the tire.

4. The pneumatic tire according to claim 1 , wherein an inclination angle of the wall surface with respect to a tire radial direction is equal to or greater than 5° and equal to or less than 15° in a cross section perpendicular to a direction in which the main groove extends.

5. The pneumatic tire according to claim 1 , wherein a dimension of the protrusion in a radial direction of the tire is equal to or greater than 15% and equal to or less than 30% of a dimension of the main groove in the radial direction of the tire.

6. the protrusion has a side surface that extends from the groove bottom surface toward the outside in the tire radial direction and is inclined so as to approach a center of the main groove in the tire axial direction, The pneumatic tire according to claim 1 , wherein an inclination angle of the side surface with respect to a tire radial direction is equal to or greater than 0° and equal to or less than 5° in a cross section perpendicular to a direction in which the main groove extends.

7. the protrusion is disposed opposite the one groove wall surface and has a side surface extending from the groove bottom surface toward an outer side in the tire radial direction, The groove bottom surface is a first curved surface that is arranged in connection with the one groove wall surface and extends in a curved manner; a second curved surface that is arranged adjacent to the side surface and extends with a curvature smaller than that of the first curved surface; The pneumatic tire of claim 1 .

8. the one groove wall surface has a second wall surface that is arranged continuous with the groove bottom surface and extends toward the tire radially inward and toward the other of the pair of groove wall surfaces in the tire axial direction, The pneumatic tire according to claim 1 , wherein an inclination angle of the second wall surface with respect to a tire radial direction is equal to or greater than 0° and equal to or less than 5° in a cross section perpendicular to a direction in which the main groove extends.

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