tire

Abstract

To provide a tire that can suppress the deterioration of wet performance as wear progresses. [Solution] The tire 10 has a tread surface 14 and a tread portion 12 provided with tread rubber, the tread surface 14 having a plurality of circumferential main grooves 16, a plurality of lug grooves 32, 38, and a plurality of land portions 26 partitioned by the plurality of circumferential main grooves 16 and the plurality of lug grooves 32, 38. A wear layer 56 is provided on a part of the surface of at least one of the plurality of circumferential main grooves 16 and the plurality of lug grooves 32, 38. The wear layer 56 has lower wear resistance than the tread rubber according to the Lambourn wear test and has a wall portion 58 provided on the surface of at least one of a pair of groove walls 52 of the grooves on which the wear layer 56 is provided. The thickness of the wall portion 58 gradually increases from the outer side in the radial direction of the tire towards the inner side in the radial direction of the tire.

Description

Technical Field

[0001] The present invention relates to a tire.

Background Art

[0002] In order to increase the block rigidity of a new tire, main grooves with a groove width gradually decreasing from the outer side in the tire radial direction to the inner side in the tire radial direction are widely adopted. In such a tire, when wear progresses, the groove volume significantly decreases, so the wet performance is also likely to deteriorate.

[0003] In view of such problems, a pneumatic tire has been disclosed that aims to suppress a decrease in drainage performance even after wear of the tread portion progresses (for example, Patent Document 1). In Patent Document 1, the first land portion is configured to include at least a first rubber portion and a second rubber portion. The first rubber portion forms a corner region where the tread surface of the first land portion and the first groove wall intersect. When the first rubber portion peels off from the second rubber portion, a portion occupied by the first rubber portion in the corner region of the first land portion is provided as a new groove space, and it is disclosed that the volume of the main groove is expanded.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the case of Patent Document 1 above, until wear progresses and the first rubber portion peels off from the second rubber portion, the groove area continues to decrease, so the wet performance is also likely to deteriorate. That is, the tire of Patent Document 1 has a problem that it cannot suppress a decrease in wet performance until wear progresses and the first rubber portion peels off from the second rubber portion.

[0006] The present invention aims to provide a tire that can suppress the deterioration of wet performance as wear progresses. [Means for solving the problem]

[0007] A tire according to one aspect of the present invention is a tire comprising a tread portion having a tread surface and provided with tread rubber, wherein the tread surface has a plurality of circumferential main grooves, a plurality of lug grooves, and a plurality of land portions partitioned by the plurality of circumferential main grooves and the plurality of lug grooves, and a wear layer is provided on a part of the surface of at least one of the plurality of circumferential main grooves and the plurality of lug grooves, wherein the wear layer has lower wear resistance than the tread rubber according to the Lambourn wear test, and has a wall portion provided on the surface of at least one of a pair of groove walls of the groove on which the wear layer is provided, and the thickness of the wall portion gradually increases from the outer side in the radial direction of the tire to the inner side in the radial direction of the tire. [Effects of the Invention]

[0008] According to the present invention, it is possible to suppress the decrease in wet performance as wear progresses. [Brief explanation of the drawing]

[0009] [Figure 1] This is a partial plan view showing the tread portion of a tire according to this embodiment. [Figure 2] This is a partial cross-sectional view along line II-II in Figure 1. [Figure 3] This is a schematic diagram used to explain the tire manufacturing method according to this embodiment. [Figure 4] This is a schematic diagram illustrating the operation and effects of the tire according to this embodiment. [Figure 5] This is a partial cross-sectional view of the tire according to Modification 1, along the line III-III in Figure 1. [Figure 6] This is a partial cross-sectional view of the tire according to Modification Example 2, along the line II-II in Figure 1. [Figure 7] This is a partial cross-sectional view of the tire according to Modification Example 3, along the line II-II in Figure 1. [Figure 8] This is a partial cross-sectional view of the tire according to Modification 4, along the line II-II in Figure 1. [Modes for carrying out the invention]

[0010] Embodiments of the present invention relate to the following aspects. [Aspect 1] A tire having a tread surface and a tread portion provided with tread rubber, The tread surface has a plurality of circumferential main grooves, a plurality of lug grooves, and a plurality of land areas partitioned by the plurality of circumferential main grooves and the plurality of lug grooves, A wear layer is provided on a portion of the surface of at least one of the plurality of circumferential main grooves and the plurality of lug grooves. The abrasion layer has lower abrasion resistance than the tread rubber according to the Lambourn abrasion test, and has a wall portion provided on at least one surface of a pair of groove walls of the groove in which the abrasion layer is provided. The aforementioned wall portion is a tire in which the thickness gradually increases from the outer side in the radial direction of the tire towards the inner side in the radial direction of the tire. [Aspect 2] The tire according to embodiment 1, wherein the groove depth D1 of the groove provided with the wear layer and the length D2 in the tire radial direction from the bottom of the groove of the wall to the outer tip in the tire radial direction satisfy the relationship 0.5 ≤ D2 / D1 ≤ 0.9. [Aspect 3] The tire according to embodiment 1 or 2, wherein the thickness W2t of the wall portion at 50% of the effective groove depth of the groove provided with the wear layer and the thickness W2b of the wall portion at 100% wear satisfy the relationship W2b / W2t ≥ 1.1. [Aspect 4] A tire according to any one of embodiments 1 to 3, wherein the thickness W2 of the wall portion and the distance W1 between grooves provided with the wear layer satisfy the relationship W2 / W1 ≤ 0.2. [Aspect 5] A tire according to any one of embodiments 1 to 4, wherein the wear resistance of the wear layer according to the Lamborn abrasion test is 60% or more and 90% or less compared to the wear resistance of the tread rubber according to the Lamborn abrasion test.

[0011] (Definition) The tire radial direction means the direction orthogonal to the tire rotation axis. The inner side in the tire radial direction means the side facing the tire rotation axis in the tire radial direction, and the outer side in the tire radial direction means the side away from the tire rotation axis in the tire radial direction. The tire circumferential direction means the circumferential direction around the tire rotation axis as the central axis. The tire width direction means the direction parallel to the tire rotation axis. The inner side in the tire width direction means the side facing the tire equatorial plane (tire equatorial plane) in the tire width direction, and the outer side in the tire width direction means the side away from the tire equatorial plane in the tire width direction. The tire equatorial plane means a plane that is orthogonal to the tire rotation axis and passes through the center of the tire width of the tire. "Along with" a certain reference means including along the direction within a range of less than ±20°, less than ±10°, or less than ±5° with respect to a certain reference. "Center" means the midpoint where the distances from two certain points are equal, and includes the range of ±10% of the distance between the two points from the midpoint. The circumferential main groove is a circumferential groove having a wear indicator indicating the end stage of wear, and generally has a groove width of 5.0 [mm] or more and a groove depth of 7.5 [mm] or more. Note that the groove width and groove depth of the circumferential main groove are not limited to the above ranges. The groove width is measured as the maximum value of the distance between the opposing groove walls of the groove opening on the tread surface in a no-load state where the tire is mounted on a standard rim and filled with the specified internal pressure. In the case of a configuration having a notch or chamfer at the groove opening, the groove width is the value measured with the intersection of the extension line of the tread surface and the extension line of the groove wall in a cross-sectional view parallel to the groove width direction and the groove depth direction as the end point. The groove depth is measured as the maximum value of the distance from the tread surface to the groove bottom in a no-load state where the tire is mounted on a standard rim and filled with the standard internal pressure. When the target groove has partial unevenness or sipes at the groove bottom, the groove depth is the value measured excluding the partial unevenness or sipes. The grounding end is the maximum position in the tire width direction on the contact surface between the tire and the flat plate when the tire is mounted on a regular rim, given a regular internal pressure, placed perpendicular to the flat plate in a stationary state, and a load corresponding to a regular load (80% of the maximum load capacity) is applied. The regular rim refers to the "Applicable Rim" defined by JATMA, the "Design Rim" defined by TRA, or the "Measuring Rim" defined by ETRTO. The regular internal pressure refers to the "Maximum Air Pressure" defined by JATMA, the maximum value described in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" defined by TRA, or the "INFLATION PRESSURES" defined by ETRTO. Also, the regular load refers to the "Maximum Load Capacity" defined by JATMA, the maximum value described in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" defined by TRA, or the "LOAD CAPACITY" defined by ETRTO.

[0012] (First Embodiment) Hereinafter, the first embodiment of the present invention will be described with reference to the drawings. Although the entire tire 10 of the first embodiment is not shown, it has a meridian cross-sectional shape similar to that of a conventional pneumatic tire. That is, the tire 10 of the first embodiment has, in a tire meridian cross-sectional view, a bead portion, a sidewall portion, a shoulder portion, and a tread portion 12 from the inner side to the outer side in the tire diameter direction. And the tire 10 has, for example, in a tire meridian cross-sectional view, a carcass layer extending from the tread portion 12 to the bead portions on both sides and wound around a pair of bead cores, and a belt layer and optionally a belt cover layer are provided on the outer side in the tire diameter direction of the carcass layer.

[0013] The tread portion 12 has a tread surface 14 and is provided with tread rubber. The tread rubber is disposed on the outer side in the tire diameter direction of the carcass layer, the belt layer, and the belt cover layer, and extends from the shoulder portion on one side in the tire width direction through the tire equatorial plane CP to the shoulder portion on the other side in the tire width direction.

[0014] The tread rubber is formed from a rubber material with excellent contact characteristics and weather resistance, and is exposed on the tread surface. Preferably, the tread rubber contains silica, wax, and an anti-aging agent.

[0015] The wax can be selected from plant-derived waxes, paraffin wax, microcrystalline wax, polyethylene wax, or a mixture thereof. The tread rubber preferably contains 1.0 part by mass or more of wax when the rubber component is 100 parts by mass.

[0016] The anti-aging agent is preferably an amine-based anti-aging agent. Examples of amine-based anti-aging agents include "N-phenyl-N'-1,3-dimethylbutyl-p-phenylenediamine" and "2,2,4-trimethyl-1,2-dihydroquinoline polymer".

[0017] The tread surface 14 is annular in shape with respect to the tire's axis of rotation and is continuous in the circumferential direction of the tire. The tread surface 14 has multiple circumferential main grooves 16 and one circumferential narrow groove 18, in the case of Figure 1. The circumferential main grooves 16 and the circumferential narrow groove 18 are annular in shape and continuous in the circumferential direction of the tire. The three circumferential main grooves 16 and the circumferential narrow groove 18 are arranged sequentially from one side to the other in the tire width direction at predetermined intervals. That is, the first circumferential main groove 20, the second circumferential main groove 22, the third circumferential main groove 24, and the circumferential narrow groove 18 are arranged sequentially from one side to the other in the tire width direction. In this specification, unless specifically distinguished, the first circumferential main groove 20, the second circumferential main groove 22, and the third circumferential main groove 24 are collectively referred to as the circumferential main groove 16.

[0018] The tread surface 14 is divided into multiple, five rows of land areas 26 in the case of Figure 1, by circumferential main grooves 16 and circumferential narrow grooves 18. The land areas 26 located outside the first circumferential main groove 20 and circumferential narrow grooves 18, which are located on the outermost side in the tire width direction, are designated as shoulder land areas 28, and the three land areas 26 located inside the first circumferential main groove 20 and circumferential narrow grooves 18 are designated as center land areas 30.

[0019] Each pair of shoulder land portions 28 has multiple shoulder lug grooves 32 arranged at predetermined intervals in the circumferential direction of the tire. The inner tip 34 of each shoulder lug groove 32 is located within the shoulder land portion 28 in the tire width direction, and the outer tip 36 in the tire width direction is located outside the tread edge E in the tire width direction.

[0020] Multiple center lug grooves 38 are arranged in the center land portion 30 at predetermined intervals in the circumferential direction of the tire. One end 40 of the center lug groove 38 in the tire width direction is connected to the circumferential main groove 16, and the other end 42 in the tire width direction is located within the center land portion 26.

[0021] In the center land area 26, which is divided by the first circumferential main groove 20 and the second circumferential main groove 22, the center lug groove 38 has its tip 40 connected to the first circumferential main groove 20 and its tip 42 located within the center land area 26.

[0022] In the center land area 26, which is divided by the second circumferential main groove 22 and the third circumferential main groove 24, the center lug groove 38 has its tip 40 connected to the second circumferential main groove 22 and its tip 42 located within the center land area 26.

[0023] In the center land area, which is divided by a third circumferential main groove 24 and a circumferential narrow groove 18, a center lug groove 38 and a small lug groove 44 are provided. The center lug groove 38 has its tip 40 connected to the third circumferential main groove 24 and its tip 42 located within the center land area 26. The small lug groove 44 has its tip 46 on one side in the tire width direction located within the center land area 30, and its tip 48 on the other side in the tire width direction connected to the circumferential narrow groove 18.

[0024] As shown in Figure 2, the circumferential main groove 16 has a groove bottom 50, a pair of groove walls 52, and a pair of edges 54. The groove bottom 50 is the bottom of the circumferential main groove 16 and defines the groove depth of the circumferential main groove 16. The groove bottom 50 has a surface that follows the tread surface 14, with the tire width direction as the short direction and the tire circumferential direction as the long direction. The pair of groove walls 52 are continuous with the outer edge of the groove bottom 50 in the tire width direction and define the groove width of the circumferential main groove 16. The pair of groove walls 52 have a surface that intersects the tread surface 14, with the tire radial direction as the short direction and the tire circumferential direction as the long direction. The pair of edges 54 are the boundary between the pair of groove walls 52 and the tread surface 14. The edges 54 extend in the circumferential direction of the tire along the circumferential main groove 16. The circumferential main groove 16 shown in Figure 2 has a shape in which the groove width gradually decreases from the tread surface 14 side toward the groove bottom 50.

[0025] (Abrasion layer) The tire 10 is provided with a wear layer 56 on the surface of a pair of groove walls 52 of the circumferential main groove 16. The wear layer 56 is integrally formed with the circumferential main groove 16. The wear layer 56 is made of rubber that has lower wear resistance according to the Lamborn wear test compared to the wear resistance of the tread rubber according to the Lamborn wear test. Preferably, the wear resistance of the wear layer 56 is 60% to 90% of the wear resistance of the tread rubber according to the Lamborn wear test. The wear layer 56 can be made of rubber with a lower carbon content or a larger average particle size of carbon contained compared to the tread rubber. More preferably, the wear resistance of the wear layer 56 according to the Lamborn wear test is 70% to 90% of the wear resistance of the tread rubber according to the Lamborn wear test.

[0026] The wear resistance measured by the Lambourn abrasion test conforms to JIS K6264, using a Lambourn abrasion tester (manufactured by Iwamoto Seisakusho Co., Ltd.) under conditions of a load of 15.0 kg (147.1 N) and a slip ratio of 25%, and the amount of wear measured is defined as the wear amount.

[0027] The wear layer 56 has a wall portion 58 provided on the groove wall 52 of the circumferential main groove 16 and a bottom portion 60 provided on the groove bottom 50. The wall portion 58 is annular and continuous in the circumferential direction of the tire along the circumferential main groove 16. The inner tip 62 in the tire radial direction of the wall portion 58 is connected to the groove bottom 50 of the circumferential main groove 16, and the outer tip 64 in the tire radial direction of the wall portion 58 is located within the groove wall 52. The tips on both sides of the bottom portion 60 in the tire width direction are each connected to the inner tip 62 in the tire radial direction of the wall portion 58. The bottom portion 60 is annular and continuous in the circumferential direction of the tire along the circumferential main groove 16.

[0028] If D1 is the groove depth of the circumferential main groove 16, and D2 is the length in the radial direction of the tire from the groove bottom 50 to the outer tip 64 of the wall portion 58 in the radial direction of the tire, then D1 and D2 satisfy the relationship 0.50 ≤ D2 / D1 ≤ 0.90. It is more preferable that D1 and D2 satisfy the relationship 0.60 ≤ D2 / D1 ≤ 0.85.

[0029] The thickness of the wall portion 58 gradually increases from the outer side in the tire radial direction toward the inner side in the tire radial direction. The thickness of the wall portion 58 is the length of the wall portion 58 in the direction perpendicular to the extending direction of the circumferential main groove 16. If the thickness of the wall portion 58 at 50% of the effective groove depth is W2t and the thickness of the wall portion 58 at 100% wear is W2b, then it is preferable that W2t and W2b satisfy the relationship W2b / W2t ≥ 1.1. It is also preferable that W2t and W2b satisfy the relationship W2b / W2t ≤ 1.5.

[0030] The effective groove depth is the distance in the depth direction of the circumferential main groove 16 from the tread surface 14 to the upper end surface of the wear indicator (not shown) formed at the groove bottom 50 of the circumferential main groove 16. In other words, it is the depth obtained by subtracting the height of the wear indicator (usually 1.7 mm) from the groove depth D1 of the circumferential main groove 16.

[0031] Let W1 be the distance between adjacent circumferential main grooves 16. Distance W1 is the distance in the tire width direction of the land area 26 that is partitioned by adjacent circumferential main grooves 16. In other words, distance W1 is the distance between the opposing edges 54 of adjacent circumferential main grooves 16. The thickness of the wall portion 58 is not particularly limited, but for example, it is 0.5 mm or more and 3.0 mm or less. It is preferable that the relationship between distance W1 and the thickness W2 of the wall portion 58 at any position satisfies 0.01 ≤ W2 / W1 ≤ 0.20. It is more preferable that W2 and W1 satisfy the relationship 0.05 ≤ W2 / W1 ≤ 0.15.

[0032] The tire 10 of this embodiment described above is obtained through the usual manufacturing processes, namely the tire material mixing process, the tire material processing process, the green tire molding process, the vulcanization process, and the post-vulcanization inspection process.

[0033] When manufacturing the tire 10 of this embodiment, an unvulcanized wear layer 56 is provided in a green tire before vulcanization at a predetermined location, i.e., as shown in Figure 3, in a predetermined area of ​​the unvulcanized tread rubber 65 that includes the location where the circumferential main groove 16 is formed, i.e., in the area corresponding to the circumferential main groove 16. Subsequently, the green tire is vulcanized using a vulcanization mold 66 having protrusions 68 and recesses corresponding to a predetermined tread pattern formed on its inner wall. The mold 66 is positioned so that the protrusions 68 that form the circumferential main groove 16 face the unvulcanized wear layer 56. During the vulcanization process, gas is drawn in from vent holes (not shown) provided in the mold 66, causing the tread rubber 65 and the wear layer 56 to move along the surface of the mold 66. The wear layer 56 moves as if being pulled along the protrusions 68 of the mold 66 that form the circumferential main groove 16, resulting in a shape in which the thickness gradually decreases from the groove bottom 50 toward the tread surface 14. In this way, a tire 10 can be obtained in which a wear layer 56 is formed on at least the groove walls 52 of the circumferential main groove 16.

[0034] As tire 10 wears down, the groove volume of the circumferential main groove 16 decreases. This decrease in groove volume tends to reduce drainage performance. In this embodiment, the circumferential main groove 16 has a shape in which the groove width gradually decreases from the tread surface 14 side toward the groove bottom 50, so the rate of decrease in groove volume of the circumferential main groove 16 increases as tire 10 wears down.

[0035] Generally, higher pressure is applied to the edges 54 on the tread surface 14. In this embodiment, the tire 10 is more prone to wear than the tread rubber because the wear layer 56 provided in the circumferential main groove 16 has lower wear resistance than the tread rubber. As a result, as shown in Figure 4, when the tire 10 wears down, the wall portion 58 provided in the groove wall 52 wears down before the tread surface 14, causing a chamfer 70 to be formed on the edges 54 of the circumferential main groove 16. This suppresses the reduction in the groove volume of the circumferential main groove 16.

[0036] The formation of a chamfer 70 on the edge 54 reduces the surface area on the ground. This reduction in surface area increases the ground pressure, thus suppressing a decrease in wet braking performance.

[0037] Therefore, the tire 10 can suppress the deterioration of wet performance as wear progresses by forming a chamfer 70 on the edge 54 prior to the wear of the tread surface 14.

[0038] Because the thickness of the wall portion 58 gradually increases from the outer side in the tire radial direction to the inner side in the tire radial direction, a larger chamfer 70 can be formed as tire 10 wears down, thus more reliably suppressing the deterioration of wet braking performance.

[0039] In the initial stages of wear, the rate of decrease in groove volume of the circumferential main groove 16 due to wear is small, resulting in a small decrease in wet braking performance. In the tire 10 according to this embodiment, the groove depth D1 of the circumferential main groove 16, where the wear layer 56 is provided, and the length D2 of the wall portion 58 from the groove bottom 50 to the outer tip 64 in the radial direction of the tire satisfy the relationship 0.5 ≤ D2 / D1 ≤ 0.9. That is, since the wall portion of the tire 10 is not exposed to the tread surface 14 when unused, the tire 10 can exhibit the original performance of the tread rubber in the initial stages of wear.

[0040] Furthermore, since D1 and D2 are within the above range, when wear progresses to a point where it can affect wet braking performance, the wall portion 58 is exposed on the tread surface 14, thereby forming a chamfer 70 on the edge 54. Therefore, the tire 10 can obtain the original performance of the tread rubber in the initial stages of wear, and as wear progresses, the formation of a chamfer 70 on the edge 54 in accordance with the progression of wear can suppress the deterioration of wet braking performance.

[0041] The thickness W2t of the wall portion 58 at 50% of the effective groove depth and the thickness W2b of the wall portion 58 at 100% wear satisfy the relationship W2b / W2t ≥ 1.1, which allows for a larger chamfer 70 on the edge 54 formed as wear progresses. Therefore, as wear progresses, the tire 10 can more reliably suppress the rate of decrease in the groove volume of the circumferential main groove 16 and increase the contact pressure due to the reduction in the land area, thereby more reliably suppressing the deterioration of wet braking performance.

[0042] The thickness W2 of the wall portion 58 and the distance W1 between the circumferential main grooves 16 provided with the wear layer 56 satisfy the relationship W2 / W1 ≤ 0.2. If it is above the lower limit of the above range, the effect of increasing the contact pressure by the chamfer 70 formed on the edge 54 can be obtained more reliably. If it is below the upper limit of the above range, the ratio of the wear layer 56 to the tread rubber is appropriately maintained, so that excellent wear resistance can be obtained for the tire 10.

[0043] The wear resistance of the wear layer 56 is 60% to 90% of the wear resistance of the tread rubber as measured by the Lambourn wear test. Being above the lower limit of this range ensures that the tire 10 maintains its wear resistance. Furthermore, being below the upper limit of this range allows for more reliable formation of the chamfer 70 on the edge 54 prior to wear on the tread surface 14.

[0044] (Second Embodiment) A second embodiment of the present invention will now be described. The tire of the second embodiment differs from that of the first embodiment in that the wear layer is provided in the lug grooves. The second embodiment can be implemented in combination with the first embodiment.

[0045] The center lug groove 38 shown in Figure 5 has a groove bottom 72, a pair of groove walls 74, and a pair of edges 76. The wear layer 56A has a wall portion 78 provided on the groove wall 74 of the center lug groove 38 and a bottom portion 80 provided on the groove bottom 72. If the groove depth of the center lug groove 38 is D1 and the length in the tire radial direction from the groove bottom 72 to the outer tip 82 of the wall portion 78 in the tire radial direction is D2, then D1 and D2 satisfy the relationship 0.50 ≤ D2 / D1 ≤ 0.90. It is more preferable that D1 and D2 satisfy the relationship 0.60 ≤ D2 / D1 ≤ 0.85.

[0046] The thickness of the wall portion 78 gradually increases from the outer side in the tire radial direction toward the inner side in the tire radial direction. The thickness of the wall portion 78 is the length of the wall portion 78 in the direction perpendicular to the extending direction of the center lug groove 38. If the thickness of the wall portion 78 at 50% of the effective groove depth of the center lug groove 38 is W2t, and the thickness of the wall portion 78 at 100% wear is W2b, then it is preferable that W2t and W2b satisfy the relationship W2b / W2t ≥ 1.1. It is also preferable that W2t and W2b satisfy the relationship W2b / W2t ≤ 1.5.

[0047] The effective groove depth of the center lug groove 38 is the distance in the depth direction of the center lug groove 3 from the tread surface 14 to the groove bottom 72 of the center lug groove 38.

[0048] Let W1 be the distance between two center lug grooves 38. Distance W1 is the distance in the tire circumferential direction of the center land area 30 that is partitioned by adjacent center lug grooves 38. In other words, distance W1 is the distance between the opposing edges 76 of adjacent center lug grooves 38. The thickness of the wall portion 78 is not particularly limited, but for example, it is 0.5 mm or more and 3.0 mm or less. It is preferable that the relationship between distance W1 and the thickness W2 of the wall portion 78 at any position satisfies 0.01 ≤ W2 / W1 ≤ 0.20. It is more preferable that W2 and W1 satisfy the relationship 0.05 ≤ W2 / W1 ≤ 0.15.

[0049] Even when a wear layer 56A is provided in the center lug groove 38 as described above, the same effects as in the first embodiment can be obtained.

[0050] In the second embodiment, the case in which the wear layer 56A is provided in the center lug groove 38 has been described, but the present invention is not limited to this. The wear layer 56A may also be provided in the shoulder lug groove 32.

[0051] (modified version) The present invention is not limited to the embodiments described above, and can be modified as appropriate within the scope of the spirit of the invention. The following modifications can be implemented individually or in combination with the above embodiments.

[0052] In the above embodiment, the case in which the wear layer has a continuous shape along the groove on which the wear layer is formed has been described, but the present invention is not limited to this, and the wear layer may be formed only in a region having a certain length relative to the length in the extending direction of the groove. Here, "certain" means 10% or more, 20% or more, 30% or more, 40% or more, or 50% or more, where L is the length in the extending direction of the groove.

[0053] In the above embodiment, the case in which the wear layer is provided in a plurality of circumferential main grooves or a plurality of lug grooves has been described, but the present invention is not limited to this, and it is sufficient if it is provided in at least one of the plurality of circumferential main grooves or a plurality of lug grooves.

[0054] In the above embodiment, the case in which the wear layer is provided on each of the pair of groove walls was described, but the present invention is not limited to this, and it is sufficient if it is provided on at least a part of the surface of the groove, for example, if it is provided on at least one of the pair of groove walls.

[0055] In the above embodiment, the circumferential main groove was described as having a shape in which the groove width gradually decreases from the tread surface side toward the groove bottom, but the present invention is not limited to this. For example, as shown in Figure 6, the circumferential main groove 16A of the tire may have a constant groove width from the tread surface 14 side toward the groove bottom 50. In this case, "constant" includes a difference of ±10% or less in the groove width.

[0056] Furthermore, as shown in Figure 7, the circumferential main groove 16B may have a shape in which the groove width gradually increases from the tread surface 14 side toward the groove bottom 50.

[0057] In the above embodiment, the case in which the wear layer has a bottom has been described, but the present invention is not limited to this. For example, as shown in Figure 8, the wear layer 56B does not have to have a bottom.

[0058] In the above embodiment, the tread surface was described as having three circumferential main grooves and one circumferential fine groove, but the present invention is not limited to this. The tread surface may have one, two, or four or more circumferential main grooves, may not have any circumferential fine grooves, or may have two or more circumferential fine grooves.

[0059] The groove depth D1 of the groove where the wear layer is provided and the length D2 from the bottom of the groove on the wall to the outer edge in the radial direction of the tire are not limited to satisfying the relationship 0.5 ≤ D2 / D1 ≤ 0.9. D2 / D1 may be less than 0.5 or greater than 0.9. The wall thickness W2t at 50% of the effective groove depth of a groove with an abrasion layer, and the wall thickness W2b at 100% wear, do not necessarily have to satisfy the relationship W2b / W2t ≥ 1.1. W2b / W2t may be less than 1.1. The wall thickness W2 and the distance W1 between grooves where the wear layer is provided do not necessarily satisfy the relationship W2 / W1 ≤ 0.2. W2 / W1 may be greater than 0.2. Regarding the wear resistance of the tread rubber as determined by the Lambourn wear test, the wear resistance of the wear layer is not limited to 60% or more and 90% or less; it may also be less than 60% or more than 90%. [Examples]

[0060] (sample) Examples 1 to 12 and a comparative example were manufactured, both with a tire size of 235 / 60R18 103H (as defined by JATMA) and having the shape shown in Figure 1 when mounted on a rim. The detailed specifications of these tires are shown in Table 1 below. Examples 1 to 12 are tires having the wear layer described in the above embodiments. In contrast, the comparative example is a tire without a wear layer.

[0061] The tires manufactured in this manner according to Examples 1 to 12, as well as the comparative example tire, were mounted on rims with a rim size of 18 x 7J at an air pressure (F / R) of 230 kPa / 230 kPa. Each test tire was then mounted on a front-wheel-drive test vehicle (engine displacement 2000 cc), and its performance was evaluated according to the following procedure.

[0062] (Wet performance) The test vehicle drove on a wet road surface with a water depth of 2 mm, and the braking distance from an initial speed of 100 km / h to a complete stop was measured. Based on these measurement results, an index evaluation was performed using a reference example as the baseline (100).

[0063] (Wear life performance) On a test course, a test vehicle equipped with the test tire was driven 10,000 km on a dry road surface. The groove depth after driving was measured, and the difference from the initial groove depth was calculated as the amount of wear. Wear performance was evaluated by expressing the reciprocal of the calculated amount of wear as an index with the conventional example described later set to 100. A larger index indicates less wear and superior wear performance.

[0064] [Table 1]

[0065] As shown in Table 1, Examples 1 to 12 were found to have superior wet performance at 80% wear compared to the comparative examples due to the presence of a wear layer. Example 2 was found to have suppressed the decline in wet performance at 50% wear compared to Example 1 due to a D2 / D1 ratio of 0.5. Example 6 was found to have suppressed the decline in wet performance at 80% wear, where wear had progressed, compared to Examples 1 to 5, due to a W2b / W2t ratio of 1.10. Example 7 was found to have superior wear resistance as a tire compared to Example 6 due to a W2 / W1 ratio of 0.20. Example 9 was found to have superior wear resistance as a tire compared to Example 7, while suppressing the decline in wet performance during wear, due to the wear resistance of the wear layer in the Lamborn wear test being 90% of that of the tread rubber in the Lamborn wear test. [Explanation of symbols]

[0066] 10 tires 12 Tread section 14 Tread surface 16 Circumferential main groove 18 Circumferential thin groove 20 1st circumferential main groove 22 2nd circumferential main groove 24 3rd circumferential main groove 26 Land 28 Shoulder Track and Field Club 30 Center Track and Field Club 32 Shoulder lug grooves 34. Tip (inside in the tire width direction) 36. Tip (outer side in the tire width direction) 38 Center lug groove 40 Tip (one side in the tire width direction) 42 Tip (other side in the tire width direction) 44 Small lug grooves 46. ​​Tip (one side in the tire width direction) 48. Tip (other side in the tire width direction) 50 groove bottom 52 Ditch wall 54 Edge 56, 56A wear layer 58 Wall 60 bottom 62 Tip (inward side of the wall in the tire width direction) 64. Tip (outer side of the wall in the tire width direction) 65 Tread Rubber 66 molds 68 Convex part 70 Chamfer 72 Groove bottom (center lug groove) 74. Groove wall (center lug groove) 76 Edge (center lug groove) 78 Wall 80 bottom 82 Tip (outer side in the tire width direction) CP Tire Equatorial Plane E Tread edge

Claims

1. A tire having a tread surface and a tread portion provided with tread rubber, The tread surface has a plurality of circumferential main grooves, a plurality of lug grooves, and a plurality of land areas partitioned by the plurality of circumferential main grooves and the plurality of lug grooves, A wear layer is provided on a portion of the surface of at least one of the plurality of circumferential main grooves and the plurality of lug grooves. The abrasion layer has lower abrasion resistance than the tread rubber according to the Lambourn abrasion test, and has a wall portion provided on at least one surface of a pair of groove walls of the groove in which the abrasion layer is provided. The aforementioned wall portion is a tire in which the thickness gradually increases from the outer side in the radial direction of the tire towards the inner side in the radial direction of the tire.

2. The tire according to claim 1, wherein the groove depth D1 of the groove provided with the wear layer and the length D2 in the tire radial direction from the bottom of the groove of the wall to the outer tip in the tire radial direction satisfy the relationship 0.5 ≤ D2 / D1 ≤ 0.

9.

3. The tire according to claim 1, wherein the thickness W2t of the wall portion at 50% of the effective groove depth of the groove provided with the wear layer and the thickness W2b of the wall portion at 100% wear satisfy the relationship W2b / W2t ≥ 1.

1.

4. The tire according to claim 1, wherein the thickness W2 of the wall portion and the distance W1 between grooves provided with the wear layer satisfy the relationship W2 / W1 ≤ 0.

2.

5. The tire according to claim 1, wherein the wear resistance of the wear layer, as measured by the Lambourn abrasion test, is 60% or more and 90% or less compared to the wear resistance of the tread rubber as measured by the Lambourn abrasion test.

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