tire

Abstract

To provide a tire that can be improved in anti-stone biting performance.SOLUTION: A tire 1 comprises a tread part 2 having a grounding surface 2a. The tread part 2 has a plurality of circumferential grooves 3 continuously extending zigzag in a tire circumferential direction. The circumferential grooves 3 have groove bottoms 3a and a pair of groove walls 3b extending from the groove bottom 3a toward the grounding surface 2a respectively. At least one of the circumferential grooves 3 includes a first inclining part 5 inclining toward one side in the tire circumferential direction, a second inclining part 6 inclining toward the opposite side of the first inclining part 5 and a crossing part 7 at which the first inclining part 5 and the second inclining part 6 crossed each other. The first inclining part 5 and the second inclining part 6 are respectively provided with one or more first protrusion parts 8 protruding from the groove bottom 3a to outside in a tire radial direction to connect the pair of groove walls 3b to each other. At least one of the crossing parts 7 is provided with a second protrusion part 9 protruding from the groove bottom 3a to outside in the tire radial direction and separating from the pair of groove walls 3b.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a tire having a tread portion having a contact surface. [Background technology]

[0002] Conventionally, tires suitable for running on rough terrain include tires with a tread portion having a plurality of circumferential grooves extending in a zigzag pattern around the tire circumferential direction. For example, Patent Document 1 below proposes a tire with improved stone trapping resistance by forming protrusions extending in the groove width direction of the main grooves at the groove bottoms of the main grooves extending in a zigzag pattern around the tire circumferential direction. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-107941 Summary of the Invention [Problem to be solved by the invention]

[0004] However, even in the main groove of Patent Document 1, the distance between the protrusions in the bent portion is large, which can cause stone trapping, and further improvement in stone trapping resistance has been desired.

[0005] The present disclosure has been devised in view of the above circumstances, and has as its main object to provide a tire that can improve stone trapping resistance. [Means for solving the problem]

[0006] The present disclosure relates to a tire having a tread portion with a contact surface, wherein the tread portion has a plurality of circumferential grooves extending continuously in a zigzag pattern around the tire, each of the circumferential grooves having a groove bottom and a pair of groove walls extending from the groove bottom toward the contact surface, at least one of the circumferential grooves including a first inclined portion inclined toward one side in the tire circumferential direction, a second inclined portion inclined toward the opposite side from the first inclined portion, and an intersection portion where the first inclined portion and the second inclined portion intersect, the first inclined portion and the second inclined portion each having at least one first protrusion protruding radially outward from the groove bottom and connecting the pair of groove walls, and at least one of the intersection portions having a second protrusion protruding radially outward from the groove bottom and spaced apart from the pair of groove walls. [Effects of the Invention]

[0007] By providing the above-described configuration, the tire of the present disclosure can improve stone trapping resistance. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a developed view showing one embodiment of a tread portion of a tire of the present disclosure. [Figure 2] FIG. 2 is an enlarged view of the circumferential groove of FIG. [Figure 3] FIG. 3 is an end view of line AA in FIG. 2. [Figure 4] FIG. 3 is an end view of line BB in FIG. 2. [Figure 5] FIG. 3 is an end view of line CC in FIG. 2. [Figure 6] FIG. 3 is an end view of line DD in FIG. 2. [Figure 7] FIG. 2 is a tire meridian cross-sectional view of the tire. [Figure 8] FIG. 10 is an enlarged view of a circumferential groove of the second embodiment. [Figure 9] FIG. 10 is an enlarged view of a circumferential groove of the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the drawings. Fig. 1 is a developed view showing a tread portion 2 of a tire 1 of this embodiment. As shown in Fig. 1, the tire 1 of this embodiment has a tread portion 2 having a contact surface 2a. The tread portion 2 of this embodiment has a plurality of circumferential grooves 3 extending continuously in a zigzag pattern in the tire circumferential direction, and a plurality of land portions 4 separated by the circumferential grooves 3.

[0010] 1 illustrates four land portions 4 separated by three circumferential grooves 3, but the number of circumferential grooves 3 is not limited to this and may be, for example, two or four or more. The number of land portions 4 is determined by the number of circumferential grooves 3.

[0011] Fig. 2 is an enlarged view of the circumferential groove 3 in Fig. 1, and Fig. 3 is a cross-sectional view taken along line AA in Fig. 2. As shown in Fig. 1 to Fig. 3, each of the circumferential grooves 3 of this embodiment includes a groove bottom 3a and a pair of groove walls 3b extending from the groove bottom 3a toward the ground contact surface 2a.

[0012] At least one of the circumferential grooves 3, and in this embodiment, all of the circumferential grooves 3, includes a first inclined portion 5 inclined toward one side in the tire circumferential direction, and a second inclined portion 6 inclined toward the opposite side from the first inclined portion 5. The circumferential groove 3 of this embodiment further includes an intersection portion 7 where the first inclined portion 5 and the second inclined portion 6 intersect. The intersection portion 7 of this embodiment includes a bending point p1 where a center line c1 of the first inclined portion 5 and a center line c2 of the second inclined portion 6 intersect.

[0013] At least one, and in this embodiment, multiple, first protrusions 8 are provided on each of the first inclined portion 5 and the second inclined portion 6. The first protrusions 8 in this embodiment protrude outward in the tire radial direction from the groove bottom 3a and connect a pair of groove walls 3b.

[0014] Such a first protrusion 8 can prevent foreign objects such as stones from getting caught in the first inclined portion 5 and the second inclined portion 6. Furthermore, since the first protrusion 8 connects the pair of groove walls 3b, it is possible to improve the rigidity of the circumferential groove 3 and reliably prevent stone getting caught even during cornering. Fig. 4 is a cross-sectional view taken along line BB in Fig. 2. As shown in Fig. 2 and Fig. 4, a second protrusion 9 is provided at at least one of the intersections 7, and in this embodiment, at all of the intersections 7. The second protrusion 9 in this embodiment protrudes from the groove bottom 3a outward in the tire radial direction and is spaced apart from the pair of groove walls 3b.

[0015] Such second protrusions 9 can suppress stone trapping even at intersections 7 where it is difficult to provide first protrusions 8 connecting a pair of groove walls 3b. Furthermore, the second protrusions 9 allow the groove walls 3b to deform between contact with the ground and take-off, so that even if a foreign object such as a stone gets caught during contact with the ground, it can be expelled during take-off. As a result, the tire 1 of this embodiment can improve its stone trapping resistance.

[0016] 1, in a more preferred embodiment, the circumferential groove 3 includes a crown circumferential groove 3A disposed on the tire equator C and a shoulder circumferential groove 3B disposed between the crown circumferential groove 3A and the tread edge Te. The crown circumferential groove 3A and the shoulder circumferential groove 3B in this embodiment each extend in a zigzag pattern in the tire circumferential direction and include a first inclined portion 5, a second inclined portion 6, and an intersection portion 7. Such a tire 1 is suitable for running on rough terrain.

[0017] Here, in the case where the tire 1 is a pneumatic tire, the "tread edge Te" is the axially outermost contact point when the tire 1 is in a normal state and is subjected to a normal load and contacts a flat surface with a camber angle of 0°. The "tire equator C" is the axial center position between the tread edges Te.

[0018] "Normal condition" refers to a condition in which the tire 1 is mounted on a normal rim, adjusted to a normal internal pressure, and no load is applied. Unless otherwise specified, the dimensions of each part of the tire 1 are values ​​measured in this normal condition.

[0019] A "genuine rim" is a rim that is specified for each tire in a standard system that includes the standard on which tire 1 is based, such as a "standard rim" for JATMA, a "design rim" for TRA, or a "measuring rim" for ETRTO. If there is no standard system that includes the standard on which tire 1 is based, a "genuine rim" is a rim that is specified for each tire by the manufacturer, etc.

[0020] "Normal internal pressure" is the air pressure specified for each tire by the standard system, including the standard on which tire 1 is based. For JATMA, it is the "maximum air pressure," for TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES," and for ETRTO, it is the "INFLATION PRESSURE." If there is no standard system including the standard on which tire 1 is based, "normal internal pressure" is the air pressure specified for each tire by the manufacturer, etc.

[0021] "Normal load" is the load determined for each tire by the standard system including the standard on which tire 1 is based, and is the "maximum load capacity" for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and "LOAD CAPACITY" for ETRTO. "Normal load" is the load determined for each tire by the manufacturer, etc., when there is no standard system including the standard on which tire 1 is based.

[0022] 1 illustrates an example in which the crown circumferential groove 3A and the shoulder circumferential groove 3B have approximately the same groove width, but the groove width of the circumferential groove 3 is not limited to this example. The groove width of the circumferential groove 3 may be different between the crown circumferential groove 3A and the shoulder circumferential groove 3B, or may be different between a pair of shoulder circumferential grooves 3B, for example.

[0023] Here, the groove width of the circumferential groove 3 is the distance on the ground contact surface 2a between a pair of groove walls 3b in a direction perpendicular to the center line of the circumferential groove 3. The groove width of the circumferential groove 3 is recognized based on the imaginary groove wall 3b that does not include recesses, slots, bends, etc. locally provided on the groove wall 3b.

[0024] The land portion 4 includes, for example, a crown land portion 4A divided between the crown circumferential groove 3A and the shoulder circumferential groove 3B, and a shoulder land portion 4B divided between the shoulder circumferential groove 3B and the tread edge Te.

[0025] The crown land portion 4A is provided with, for example, crown lateral grooves 10 that connect the intersections 7 of the crown circumferential grooves 3A and the intersections 7 of the shoulder circumferential grooves 3B. The crown lateral grooves 10 of this embodiment divide the crown land portion 4A into a plurality of crown blocks 11. Although not shown, the crown lateral grooves 10 may also be provided with, for example, first protrusions 8. The land portion 4 may also be provided with other lateral grooves, narrow grooves, recesses, slots, sipes, etc., as appropriate (not shown). Such a tire 1 is suitable for running on rough terrain.

[0026] 1 and 2, the first protrusions 8 and the second protrusions 9 of this embodiment are spaced apart from each other. Such a circumferential groove 3 can improve the stone trapping resistance of the tire 1 while maintaining the wet performance and rough road performance by ensuring the groove volume.

[0027] In a plan view of the tread, the first protrusions 8 have a rectangular shape in which the length La in the groove width direction is greater than the length Lb in the center line direction of the circumferential groove 3. Such first protrusions 8 can connect the groove walls 3b while ensuring the groove volume, thereby further improving the rough road performance of the tire 1.

[0028] Here, the length La of the first protrusion 8 in the groove width direction and the length Lb of the circumferential groove 3 in the center line direction are each the lengths when the first top surface 8a, which constitutes the outer surface of the first protrusion 8 in the tire radial direction, is projected onto a plane.

[0029] The length Lb of the first protrusions 8 in the center line direction of the circumferential grooves 3 is preferably 10% to 50% of the minimum groove width W of the circumferential grooves 3. When the length Lb of the first protrusions 8 in the center line direction is 10% or more of the minimum groove width W of the circumferential grooves 3, the effect of suppressing stone trapping can be reliably achieved. When the length Lb of the first protrusions 8 in the center line direction is 50% or less of the minimum groove width W of the circumferential grooves 3, deformation between contact with the ground and take-off is promoted, and stones trapped during contact with the ground can be expelled during take-off. Here, the minimum groove width W of the circumferential grooves 3 is the smallest among the groove widths of the circumferential grooves 3.

[0030] The angle θa between the side 8b connecting the pair of groove walls 3b of the first protrusion 8 and the center line of the circumferential groove 3 is 80 to 90°. Such a first protrusion 8 prevents the length La in the groove width direction from becoming excessively large and maintains appropriate rigidity, thereby suppressing deformation during cornering and preventing stone trapping even during cornering. From this perspective, the angle θa between the side 8b and the center line of the circumferential groove 3 is more preferably 90°.

[0031] Here, the side 8b connecting the groove walls 3b of the first protrusion 8 is the side on the first top surface 8a. The angle θa between the side 8b and the center line of the circumferential groove 3 is recognized as an acute angle or a right angle.

[0032] The distance Lc between adjacent first protrusions 8 is preferably equal to or less than the minimum groove width W of the circumferential groove 3. Such first protrusions 8 prevent stones or other foreign objects from getting caught between the first protrusions 8, thereby further improving stone trapping resistance. Furthermore, even if a stone or other foreign object gets caught in the circumferential groove 3, the first protrusions 8 prevent the foreign object from coming into contact with the groove bottom 3a, thereby preventing so-called drilling, in which the foreign object penetrates the groove bottom 3a and damages the internal structure of the tire 1. Here, the distance Lc between the first protrusions 8 is the distance between the sides 8b of adjacent first protrusions 8 on the center line of the circumferential groove 3.

[0033] The distance Lc between the first protrusions 8 is preferably 20% to 100% of the minimum groove width W of the circumferential groove 3. When the distance Lc between the first protrusions 8 is 20% or more of the minimum groove width W of the circumferential groove 3, the radius of curvature between the first protrusions 8 and the groove bottom 3a can be increased, and damage due to stress concentration can be suppressed.

[0034] The second protrusion 9 in this embodiment is provided at a position including the bending point p1. Therefore, the second protrusion 9 is provided at the center of the intersection 7. Such a second protrusion 9 can effectively suppress stone trapping, and can further improve the stone trapping resistance of the tire 1.

[0035] In this embodiment, the second protrusions 9 have a concave polygonal shape that bends around a bending point p1 in a plan view of the tread. Such second protrusions 9 can maintain high rigidity without being connected to the groove wall 3b, and can suppress deformation when foreign objects such as stones get caught in them.

[0036] The angle θb of the reentrant angle 9a of the reentrant polygonal shape is desirably equal to or greater than the angle θc between the center line c1 of the first inclined portion 5 and the center line c2 of the second inclined portion 6 at the bending point p1. By increasing the bending angle, such second protrusions 9 can suppress breakage due to stress concentration. Here, the angle θb of the reentrant angle 9a is the angle at the second top surface 9c that constitutes the outer surface of the second protrusion 9 in the tire radial direction.

[0037] The distance Ld between the second protrusion 9 and the first protrusion 8 adjacent to the second protrusion 9 is preferably equal to or less than the minimum groove width W of the circumferential groove 3. Such an intersection 7 can prevent foreign matter such as stones from getting caught between the first protrusion 8 and the second protrusion 9, thereby further improving stone trapping resistance. Furthermore, the intersection 7 can prevent drilling even if foreign matter such as stones gets caught in the circumferential groove 3. Here, the distance Ld between the second protrusion 9 and the first protrusion 8 is the distance at the center line of the circumferential groove 3 when the first top surface 8a and the second top surface 9c are projected onto a plane.

[0038] The distance Ld between the second protrusions 9 and the first protrusions 8 is preferably 10% to 85% of the minimum groove width W of the circumferential groove 3. By making the distance Ld between the second protrusions 9 and the first protrusions 8 10% or more of the minimum groove width W of the circumferential groove 3, the radius of curvature between the first protrusions 8 and the groove bottom 3a and the second protrusions 9 can be increased, and breakage due to stress concentration can be suppressed. By making the distance Ld between the second protrusions 9 and the first protrusions 8 85% or less of the minimum groove width W of the circumferential groove 3, it is possible to help suppress stone trapping at the intersections 7, which have complex shapes and are prone to stone trapping.

[0039] It is desirable that the distance Ld between the second protrusion 9 and the first protrusion 8 adjacent to the second protrusion 9 is smaller than the distance Lc between adjacent first protrusions 8. Such an intersection 7 can more reliably prevent stone trapping even at intersections 7 with complex shapes that are prone to stone trapping.

[0040] The distance Ld between the second protrusions 9 and the first protrusions 8 is preferably 45% to 85% of the distance Lc between the first protrusions 8. When the distance Ld is 45% or more of the distance Lc, the radius of curvature between the first protrusions 8 and the second protrusions 9 and the groove bottom 3a can be increased, making it possible to suppress breakage due to stress concentration. When the distance Ld is 85% or less of the distance Lc, stone trapping at the intersection 7 can be more reliably suppressed.

[0041] In the present embodiment, the second protrusions 9 have sides 9b that are parallel to the side 8b that connects the pair of groove walls 3b of the first protrusions 8 in a plan view of the tread. In this case, the distance Ld between the second protrusions 9 and the first protrusions 8 is the distance between the side 9b of the second protrusions 9 and the side 8b of the first protrusions 8 in a plan view of the tread. Such an intersection 7 can make the distance Ld between the second protrusions 9 and the first protrusions 8 uniform, thereby further improving the stone-trapping resistance of the tire 1.

[0042] Fig. 5 is a cross-sectional view taken along line CC in Fig. 2. As shown in Figs. 3 and 5, the height Ha of the first protrusions 8 from the groove bottom 3a is preferably 10% to 50% of the maximum depth D of the circumferential groove 3. When the height Ha of the first protrusions 8 is 10% or more of the maximum depth D, it is possible to reliably prevent foreign matter such as stones from getting caught. When the height Ha of the first protrusions 8 is 50% or less of the maximum depth D, it is possible to maintain the rigidity of the first protrusions 8 and prevent deformation due to contact with foreign matter such as stones.

[0043] Here, the maximum depth D of the circumferential groove 3 is the largest among the groove depths of the circumferential grooves 3 in which the first protrusions 8 are formed. The groove depth of the circumferential groove 3 is the distance in the tire radial direction from the contact surface 2a to the deepest part of the groove bottom 3a.

[0044] It is desirable that the length Le of the first protrusion 8 on the groove bottom 3a side in the center line direction of the circumferential groove 3 is greater than the length Lb of the first top surface 8a in the center line direction of the circumferential groove 3. Even when a foreign object such as a stone becomes lodged between adjacent first protrusions 8 during ground contact, such first protrusions 8 can expel the object by deformation during ground release, thereby improving the stone trapping resistance of the tire 1.

[0045] The angle θd of the surface extending from the side 8b of the first top surface 8a of the first protrusion 8 toward the groove bottom 3a with respect to the tire radial direction is preferably 5 to 60°. When the angle θd of the surface extending from the side 8b toward the groove bottom 3a is 5° or more, foreign matter such as stones is prevented from getting caught in the vicinity of the groove bottom 3a, and drilling can be reliably suppressed. When the angle θd of the surface extending from the side 8b toward the groove bottom 3a is 60° or less, the height Ha of the first protrusion 8 can be sufficiently secured, and the getting of foreign matter such as stones is reliably suppressed. From this viewpoint, the angle θd of the surface extending from the side 8b toward the groove bottom 3a is more preferably 10 to 50°.

[0046] Fig. 6 is a cross-sectional view taken along line DD in Fig. 2. As shown in Figs. 4 and 6, the height Hb of the second protrusions 9 from the groove bottom 3a is preferably 10% to 60% of the maximum depth D of the circumferential groove 3. When the height Hb of the second protrusions 9 is 10% or more of the maximum depth D, it is possible to reliably prevent foreign matter such as stones from getting caught. When the height Hb of the second protrusions 9 is 60% or less of the maximum depth D, it is possible to maintain the rigidity of the second protrusions 9 and prevent deformation due to contact with foreign matter such as stones.

[0047] 3 to 6, the height Hb of the second protrusions 9 is preferably 100% to 120% of the height Ha of the first protrusions 8. Such first protrusions 8 and second protrusions 9 can improve the stone trapping resistance of the tire 1 in a well-balanced manner.

[0048] It is desirable that the length Lf of the second protrusion 9 along the center line of the circumferential groove 3 be greater than the length Lb of the first protrusion 8 in the direction of the center line of the circumferential groove 3. Such a second protrusion 9 has high rigidity and can further improve the stone trapping resistance of the tire 1. Here, the length Lf of the second protrusion 9 along the center line of the circumferential groove 3 is the length when the second top surface 9c of the second protrusion 9 is projected onto a plane.

[0049] It is desirable that the length Lg of the second protrusion 9 on the groove bottom 3a side along the center line of the circumferential groove 3 is greater than the length Lf of the second top surface 9c along the center line of the circumferential groove 3. Even when a foreign object such as a stone becomes lodged between the second protrusion 9 and the first protrusion 8 during ground contact, such a second protrusion 9 can eject the object by deformation during ground release, thereby improving the stone-trapping resistance of the tire 1.

[0050] The angle θe of the surface extending from the side 9b of the second top surface 9c of the second protrusion 9 toward the groove bottom 3a with respect to the tire radial direction is preferably 5 to 60°. When the angle θe of the surface extending from the side 9b toward the groove bottom 3a is 5° or more, foreign matter such as stones is prevented from getting caught in the vicinity of the groove bottom 3a, and drilling can be reliably suppressed. When the angle θe of the surface extending from the side 9b toward the groove bottom 3a is 60° or less, a sufficient area of ​​the second top surface 9c can be secured, and the getting of foreign matter such as stones into the groove can be reliably suppressed.

[0051] The length Lh of the cross section of the second protrusion 9 perpendicular to the center line of the circumferential groove 3 is preferably 30% or less of the minimum groove width W of the circumferential groove 3. By making the length Lh of the cross section of the second protrusion 9 perpendicular to the center line of the circumferential groove 3 30% or less of the minimum groove width W of the circumferential groove 3, deformation between contact with the tire and take-off is promoted, and even if a foreign object such as a stone becomes caught during contact with the tire, it is useful for expelling it during take-off. Here, the length Lh of the cross section of the second protrusion 9 perpendicular to the center line of the circumferential groove 3 is the length of the second top surface 9c of the second protrusion 9 when projected onto a plane.

[0052] The length Lh of the cross section of the second protrusion 9 perpendicular to the center line of the circumferential groove 3 is preferably 50% to 100% of the length Li of the cross section of the second protrusion 9 on the groove bottom 3a side perpendicular to the center line of the circumferential groove 3. Even when a foreign object such as a stone gets caught between the second protrusion 9 and the groove wall 3b during ground contact, such second protrusion 9 can eject the object by deformation during ground release, thereby improving the stone trapping resistance of the tire 1.

[0053] The angle θf of the side surface of the second protrusion 9 relative to the tire radial direction in a cross section perpendicular to the center line of the circumferential groove 3 is preferably 5 to 22°. When the angle θf of the side surface of the second protrusion 9 in a cross section perpendicular to the center line of the circumferential groove 3 is 5° or more, foreign matter such as stones is prevented from getting caught near the groove bottom 3a, and drilling can be reliably prevented. When the angle θf of the side surface of the second protrusion 9 in a cross section perpendicular to the center line of the circumferential groove 3 is 22° or less, a sufficient area of ​​the second top surface 9c can be secured, and the getting of foreign matter such as stones can be reliably prevented.

[0054] Fig. 7 is a tire meridian cross-sectional view including the rotation axis of the tire 1 of this embodiment in a normal state. As shown in Fig. 7, the tire 1 is suitably used as a heavy-duty tire for use on trucks and buses, for example. The tire 1 is not limited to being a heavy-duty tire, and can be applied to various types of tires 1, such as pneumatic tires for passenger cars, motorcycles, and racing tires, and non-pneumatic tires that are not filled with pressurized air inside.

[0055] The tire 1 of this embodiment includes a tread portion 2 extending annularly, a pair of sidewall portions 13 extending annularly on both sides of the tread portion 2, and a pair of bead portions 14 extending annularly and connected to the sidewall portions 13. The tire 1 has, for example, a toroidal carcass 16 extending across between bead cores 15 of the pair of bead portions 14, and a belt layer 17 disposed outward from the carcass 16 in the tire radial direction and inward from the tread portion 2 in the tire radial direction.

[0056] The carcass 16 is made up of, for example, one carcass ply 16A. The carcass ply 16A includes carcass cords and a topping rubber covering the carcass cords. The carcass cords are arranged, for example, at an angle of 75 to 90 degrees relative to the tire circumferential direction. The carcass cords are preferably made up of, for example, organic fiber cords such as nylon, polyester, rayon, or steel cords. The carcass 16 may be made up of, for example, two or more carcass plies 16A.

[0057] The carcass ply 16A has, for example, a main body portion 16a and a turned-up portion 16b. The main body portion 16a desirably extends from the tread portion 2 through the sidewall portion 13 to the bead core 15 of the bead portion 14. The turned-up portion 16b, for example, is continuous with the main body portion 16a and is turned back around the bead core 15 from the axially inner side to the outer side, extending radially outward in the tire. For example, the carcass ply 16A may have a so-called ultra-high turn-up structure in which the end of the turned-up portion 16b reaches between the main body portion 16a and the belt layer 17.

[0058] The belt layer 17 includes at least one belt ply 17A, 17B, 17C, and 17D (in this embodiment, four belt plies). The belt layer 17 preferably includes two or more belt plies 17A, 17B, 17C, and 17D adjacent to each other in the tire radial direction. In such a belt layer 17, the multiple belt plies 17A, 17B, 17C, and 17D cooperate with each other to improve the rigidity of the tread portion 2 and help reduce the rolling resistance of the tire 1.

[0059] It is desirable that the belt plies 17A, 17B, 17C, and 17D have the same configuration. Such belt plies 17A, 17B, 17C, and 17D can be manufactured and managed as a single belt ply 17a, which reduces production costs. Note that the belt plies 17A, 17B, 17C, and 17D may have different configurations, for example.

[0060] 1 to 7, the distance Lj in the tire radial direction from the groove bottom 3a of the circumferential groove 3 to the outermost side surface of the belt layer 17 is preferably greater than the sum (D-Ha+Lc) of the depth (D-Ha) from the contact patch 2a to the first top surface 8a and the distance Lc between the first protrusions 8. In such a tread portion 2, even if a foreign object such as a stone gets caught between the first protrusions 8, there is no risk of the foreign object reaching the belt layer 17, and the occurrence of drilling can be reliably suppressed. Here, the outermost side surface of the belt layer 17 is the outer surface of the belt ply 17D located outermost in the tire radial direction.

[0061] The distance Lj in the tire radial direction from the groove bottom 3a of the circumferential groove 3 to the outermost side surface of the belt layer 17 is preferably greater than the sum (D-Hb+Ld) of the depth (D-Hb) from the contact patch 2a to the second top surface 9c and the distance Ld between the second protrusions 9 and the first protrusions 8. In such a tread portion 2, even if a foreign object such as a stone becomes lodged between the first protrusions 8 and the second protrusions 9, there is no risk of the foreign object reaching the belt layer 17, and drilling can be reliably suppressed.

[0062] In the above-described embodiment, the second protrusion 9 has a concave polygonal shape that is bent around the bending point p1, but the shape of the second protrusion 9 is not limited to this.

[0063] Fig. 8 is an enlarged view of the circumferential groove 20 of the second embodiment. As shown in Fig. 8, the circumferential groove 20 of the second embodiment has the same configuration as the above-mentioned circumferential groove 3 except for the shape of the second protrusion 22 provided at the intersection 21. The same components as the above-mentioned circumferential groove 3 are denoted by the same reference numerals, and the description thereof will be omitted.

[0064] In the second embodiment, the second protrusions 22 have a polygonal shape with one vertex 22a at the same circumferential position as the bending point p1 in a plan view of the tread. Such second protrusions 22 can maintain high rigidity even when external forces act in complex directions around the bending point p1, thereby improving the stone trapping resistance of the tire 1.

[0065] Fig. 9 is an enlarged view of the circumferential groove 25 of the third embodiment. As shown in Fig. 9, the circumferential groove 25 of the third embodiment has the same configuration as the above-described circumferential groove 3 except for the shape of the second protrusion 27 provided at the intersection 26. The same components as the above-described circumferential groove 3 are denoted by the same reference numerals, and the description thereof will be omitted.

[0066] The second protrusions 27 of the third embodiment have a polygonal shape with two vertices 27a, 27b at the same circumferential position as the bending point p1 in a plan view of the tread. Such second protrusions 27 can maintain high rigidity even when an external force acts in complex directions around the bending point p1, thereby improving the stone trapping resistance of the tire 1.

[0067] Although particularly preferred embodiments of the present disclosure have been described in detail above, the present disclosure is not limited to the above-described embodiments and can be modified and implemented in various forms. [Example]

[0068] A tire having the basic tread pattern shown in Figure 1 was prototyped based on the specifications in Table 1. The prototype tire was tested for stone-biting resistance. The common specifications and test method are as follows:

[0069] <Common specifications> Tire size: 315 / 80R22.5 Rim size: 9.00 x 22.5 Test vehicle: large truck Minimum circumferential groove width W: 14mm Maximum depth of circumferential groove D: 20.9 mm Distance from the bottom of the circumferential groove to the belt layer Lj: 17.8 mm

[0070] <Stone trap resistance> The prototype tires were adjusted to the standard internal pressure and fitted to all wheels of a test vehicle, and a test driver drove the tires 100 km at 20 km / h on an unpaved gravel test course with 20 turning points per 10 km, after which the occurrence of stone entrapment was evaluated. The results were expressed as an index, with Comparative Example 1 being set at 100, and a smaller index indicates fewer stones trapped and better stone entrapment resistance.

[0071] The test results are shown in Table 1. [Table 1]

[0072] As a result of the test, it was confirmed that the number of stones trapped in the tire of the example was smaller than that of the comparative example, and that the tire had improved stone trapping resistance.

[0073] [Note] The present disclosure is as follows.

[0074] [Disclosure 1] a tire having a tread portion with a contact surface, the tread portion having a plurality of circumferential grooves extending continuously in a zigzag pattern around the tire circumferential direction, each of the circumferential grooves having a groove bottom and a pair of groove walls extending from the groove bottom toward the contact surface, at least one of the circumferential grooves including a first inclined portion inclined toward one side in the tire circumferential direction, a second inclined portion inclined toward the opposite side from the first inclined portion, and an intersection portion where the first inclined portion and the second inclined portion intersect, the first inclined portion and the second inclined portion each having at least one first protrusion protruding radially outward from the groove bottom and connecting the pair of groove walls, and at least one of the intersection portions having a second protrusion protruding radially outward from the groove bottom and spaced apart from the pair of groove walls.

[0075] [Disclosure 2] The tire according to Disclosure 1, wherein the first protrusions and the second protrusions are spaced apart from each other.

[0076] [Disclosure 3] The tire described in Disclosure 1 or 2, wherein the intersection portion includes a bending point where a center line of the first inclined portion and a center line of the second inclined portion intersect, and the second protrusion portion is provided at a position including the bending point.

[0077] [Disclosure 4] The tire according to Disclosure 3, wherein the second projections have a polygonal shape with a vertex at the same position in the tire circumferential direction as the bending point in a plan view of the tread.

[0078] [Disclosure 5] The tire according to Disclosure 3 or 4, wherein the second projection has a concave polygonal shape that is bent around the bending point in a plan view of the tread.

[0079] [Disclosure 6] The tire according to the present disclosure 5, wherein an angle θb of a reentrant angle of the reentrant polygonal shape is equal to or greater than an angle θc formed between a center line of the first inclined portion and a center line of the second inclined portion at the bending point.

[0080] [Disclosure 7] A tire described in any one of Disclosures 1 to 6, wherein the first protrusion portion has a rectangular shape in a plan view of the tread, with a length La in the groove width direction being greater than a length Lb in the center line direction of the circumferential groove, and an angle θa between the side connecting the pair of groove walls and the center line of the circumferential groove is 80 to 90 degrees.

[0081] [Disclosure 8] The tire according to Disclosure 7, wherein the second projection has a side parallel to the side connecting the pair of groove walls of the first projection in a plan view of the tread.

[0082] [Disclosure 9] A tire described in any one of Disclosures 1 to 8, wherein the first inclined portion and the second inclined portion each have a plurality of the first protrusions, and the distance Lc between adjacent first protrusions and the distance Ld between the second protrusion and the first protrusion adjacent to the second protrusion are each less than or equal to the minimum groove width W of the circumferential groove.

[0083] [Disclosure 10] A tire described in any one of Disclosures 1 to 9, wherein the first inclined portion and the second inclined portion each have a plurality of the first protrusions, and a distance Ld between the second protrusion and the first protrusion adjacent to the second protrusion is smaller than a distance Lc between the first protrusions adjacent to each other.

[0084] [Disclosure 11] A tire described in any one of disclosures 1 to 10, wherein a height Ha of the first protrusion from the groove bottom and a height Hb of the second protrusion from the groove bottom are each 10% to 50% of a maximum depth D of the circumferential groove.

[0085] [Disclosure 12] A tire described in any one of disclosures 1 to 11, wherein a length Lf of the second protrusion along the center line of the circumferential groove is greater than a length Lb of the first protrusion along the center line of the circumferential groove. [Explanation of symbols]

[0086] 1 tire 2 Tread section 2a Ground plane 3 Circumferential groove 3a groove bottom 3b Groove wall 5 1st slope 6 Second slope 7 Intersection 8 1st protrusion 9 Second protrusion

Claims

1. A tire having a tread portion with a contact surface, The tread portion has a plurality of circumferential grooves extending continuously in a zigzag pattern in the tire circumferential direction, Each of the circumferential grooves includes a groove bottom and a pair of groove walls extending from the groove bottom toward the ground contact surface, At least one of the circumferential grooves includes a first inclined portion inclined toward one side in the tire circumferential direction, a second inclined portion inclined toward the opposite side from the first inclined portion, and an intersection portion where the first inclined portion and the second inclined portion intersect, a plurality of first protrusions are provided on the first inclined portion and the second inclined portion, the first protrusions protruding from the groove bottom toward an outer side in the tire radial direction and connecting the pair of groove walls; a second protrusion protruding from the groove bottom toward an outer side in the tire radial direction and spaced apart from the pair of groove walls is provided at at least one of the intersections; the first protrusion and the second protrusion are spaced apart from each other, a distance Ld between the second protrusion and the first protrusion adjacent to the second protrusion is smaller than a distance Lc between the first protrusions adjacent to each other; a length Lf of the second protrusion along the center line of the circumferential groove is greater than a length Lb of the first protrusion along the center line of the circumferential groove; tire.

2. The tire has a belt layer, 2. The tire according to claim 1, wherein a distance Lj in the tire radial direction from the groove bottom of the circumferential groove to the outermost side surface of the belt layer is greater than a sum (D-Ha+Lc) of a depth (D-Ha) from the ground contact surface to a first top surface that constitutes the outer side surface of the first protrusion in the tire radial direction and a distance Lc between the first protrusions.

3. the intersecting portion includes a bending point where a center line of the first inclined portion intersects with a center line of the second inclined portion, The tire according to claim 1 or 2, wherein the second projection is provided at a position including the bending point.

4. The tire according to claim 3 , wherein the second projections have a polygonal shape having a vertex at the same position in the tire circumferential direction as the bending point in a plan view of the tread.

5. The tire according to claim 3 or 4, wherein the second projection has a concave polygonal shape that is bent around the bending point in a plan view of the tread.

6. The tire according to claim 5 , wherein an angle θb of a reentrant angle of the reentrant polygonal shape is equal to or greater than an angle θc formed between a center line of the first inclined portion and a center line of the second inclined portion at the bending point.

7. 7. The tire according to claim 1, wherein the first protrusions have a rectangular shape in a tread plan view, the length La in a groove width direction being greater than the length Lb in a center line direction of the circumferential groove, and the angle θa between a side connecting the pair of groove walls and the center line of the circumferential groove is 80 to 90 degrees.

8. The tire according to claim 7 , wherein the second projection has a side parallel to the side connecting the pair of groove walls of the first projection in a plan view of the tread.

9. a plurality of the first protrusions are provided on the first inclined portion and the second inclined portion, 9. The tire according to claim 1, wherein a distance Lc between the adjacent first protrusions and a distance Ld between the second protrusion and the first protrusion adjacent to the second protrusion are each equal to or less than a minimum groove width W of the circumferential groove.

10. A tire described in any one of claims 1 to 9, wherein the height Ha of the first protrusion from the bottom of the groove and the height Hb of the second protrusion from the bottom of the groove are each 10% to 50% of the maximum depth D of the circumferential groove.

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