Pneumatic tire

Abstract

To provide a pneumatic tire that can enhance traction performance in a tire circumferential direction and can suppress early partial wearing on a dry road surface.SOLUTION: A tire includes a tread having two inner lands provided between two shoulder lands and opposing to each other through a main groove. The two inner lands are a first inner land having two first protrusions, which separate in a tire circumferential direction and protrude toward the main groove with respect to a tire axial direction, when viewed from outside in a tire radial direction, and a second inner land having a second protrusion intruding into a first groove between the two first protrusions, which protrude toward the main groove with respect to the tire axial direction and whose edges at the main groove side on a ground-contact surface are formed in a V-shape, when viewed from the outside in the tire radial direction. A rib protruding toward outside in the tire radial direction and having a dimple dented from the ground-contact surface on an outer surface in the tire radial direction is formed to be connected to a corner part of at least either of the first groove and the second protrusion.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to pneumatic tires, and more particularly to pneumatic tires having a tread including a plurality of lands. [Background technology]

[0002] Patent Document 1 describes that chamfers are formed on all edge sides of the tread surface of blocks provided in the tread, and closed sipes are formed in the blocks. Patent Document 2 describes that closed grooves are formed on the surfaces of blocks provided in the tread. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-49730 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-97712 Summary of the Invention [Problem to be solved by the invention]

[0004] A pneumatic tire may have a tread with two inner land portions facing each other via a main groove, with two second protrusions protruding in the tire axial direction provided on the first inner land portion, and the second protrusions protruding in the tire axial direction provided on the second inner land portion inserted into a V-shaped groove between the two first protrusions. In this case, it may be possible to hollow out the inside of the corners of the V-shaped grooves and protrusions to suppress the concentration of surface pressure near the edges when the tire comes into contact with the ground on dry roads and to suppress localized premature wear. However, hollowing out the inside of the corners reduces the rigidity of the corners, which reduces circumferential traction performance of the tire. Therefore, there is room for improvement in terms of improving circumferential traction performance and suppressing localized premature wear on dry roads.

[0005] An object of the present invention is to provide a pneumatic tire that can improve traction performance in the tire circumferential direction and can suppress early partial wear on dry road surfaces. [Means for solving the problem]

[0006] The pneumatic tire of the present invention is a pneumatic tire having a tread with two shoulder lands provided at both axial ends of the tire and two inner lands provided between the two shoulder lands and facing each other in the tire axial direction with the main grooves interposed therebetween, wherein the two inner lands are a first inner land that, when viewed from the radially outer side of the tire, are separated in the tire circumferential direction, protrude toward the main grooves in the tire axial direction, and have two first protrusions with V-shaped edges on the main groove side at the contact patch, and a second inner land that, when viewed from the radially outer side of the tire, protrudes toward the main grooves in the tire axial direction, and has V-shaped edges on the main groove side at the contact patch and is embedded in the V-shaped first groove between the two first protrusions, and a rib is formed on the radially outer side of the tire that protrudes radially outward and has dimples recessed from the contact patch so as to be connected to the inside of at least one corner of the first grooves and the second protrusions. [Effects of the Invention]

[0007] In the pneumatic tire according to the present invention, a rib protruding radially outward is connected to the inside of at least one corner of the V-shaped first groove and the second projection inserted into the first groove, thereby increasing rigidity near the corner. This improves traction performance in the tire circumferential direction. Furthermore, a dimple recessed from the contact patch is formed on the rib's radially outer surface, which reduces the concentration of surface pressure near the edge of the corner when the corner comes into contact with the ground, thereby reducing localized premature wear on dry roads. Increasing rigidity near the corner also reduces localized premature wear. [Brief explanation of the drawings]

[0008] [Figure 1]1 is a perspective view of a portion in the tire circumferential direction of a pneumatic tire that is an example of an embodiment. [Figure 2] FIG. 2 is a plan view of the pneumatic tire shown in FIG. 1, showing a part of the tread in the circumferential direction. [Figure 3] FIG. 3 is an enlarged perspective view of part A in FIG. 2. [Figure 4] 3 is a cross-sectional view of FIG. 2 taken along line B-B. [Figure 5] FIG. 3 is an enlarged view of part C in FIG. 2. [Figure 6A] FIG. 5 is an enlarged view of the left half of FIG. [Figure 6B] FIG. 6B is an enlarged view of part D in FIG. 6A. [Figure 6C] FIG. 6B is an enlarged view of part E in FIG. 6A. [Figure 6D] FIG. 6B is an enlarged view of part F in FIG. 6A. [Figure 6E] FIG. 6B is an enlarged view of part G in FIG. 6A. [Figure 6F] FIG. 1(a) is a schematic cross-sectional view showing the contact state between the road surface and the vicinity of the shoulder main groove of the contact patch when it is assumed that no ground contact load is applied to the tire in a comparative example, and FIG. 1(b) is a view corresponding to FIG. 1(a) when a ground contact load is applied. [Figure 6G] FIG. 1(a) is a schematic cross-sectional view showing the contact state between the road surface and the vicinity of the shoulder main groove of the contact patch when it is assumed that no ground load is applied to the tire in an embodiment, and FIG. 1(b) is a view corresponding to FIG. 1(a) when a ground load is applied. [Figure 6H] FIG. 3 is a cross-sectional view of FIG. 2 taken along the line H-H. [Figure 6I] FIG. 2 is a cross-sectional view of FIG. [Figure 6J] FIG. 6 is a cross-sectional view of FIG. 5 . [Figure 6K] FIG. 6 is a cross-sectional view of FIG. 5 taken along the line K-K. [Figure 7] FIG. 3 is an enlarged view of part L in FIG. 2. [Figure 8] FIG. 8 is a cross-sectional view of FIG. 7 taken along line MM. [Figure 9] FIG. 10 is a perspective view of a portion in the tire circumferential direction of a pneumatic tire according to another embodiment. [Figure 10]FIG. 10 is a plan view of the pneumatic tire shown in FIG. 9, showing a part of the tread in the circumferential direction. [Figure 11] 11 is a cross-sectional view of FIG. 10 taken along the line N-N. [Figure 12] 11 is a cross-sectional view of FIG. 10 taken along a plane P-P line. [Figure 13] FIG. 10 is a schematic diagram showing some blocks of the first inner land and the second inner land in a tire according to another example of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an example of an embodiment of a pneumatic tire according to the present invention will be described in detail with reference to the drawings. The embodiment described below is merely an example, and the present invention is not limited to the following embodiment. Furthermore, the present invention includes selective combinations of the components of the multiple embodiments and modified examples described below.

[0010] [Overall tire configuration] FIG. 1 is a perspective view of a portion of a pneumatic tire 1 according to an embodiment in the circumferential direction of the tire. FIG. 2 is a plan view of the pneumatic tire 1 shown in FIG. 1, illustrating a portion of a tread 10 in the circumferential direction. FIG. 3 is an enlarged perspective view of portion A in FIG. 2. FIG. 4 is a cross-sectional view taken along line B-B in FIG. 2. FIG. 5 is an enlarged view of portion C in FIG. 2. FIG. 6A is an enlarged view of the left half of FIG. 4. As shown in FIGS. 1 to 6A, the pneumatic tire 1 includes a tread 10 that is a portion that comes into contact with the road surface. Hereinafter, the "pneumatic tire 1" will be referred to as the "tire 1." The tread 10 has a tread pattern including a plurality of lands spaced apart in the tire axial direction and a plurality of grooves spaced apart in the tire axial direction, and is formed in an annular shape along the tire circumferential direction (the vertical direction in FIGS. 1 and 2). In FIGS. 1 to 6A, the tire circumferential direction is indicated by arrow X, the tire axial direction is indicated by arrow Y, and the tire radial direction is indicated by arrow Z.

[0011] 1, the tire 1 is mounted on a vehicle so that the left side is on the outer side (OUT side) in the width direction of the vehicle and the right side is on the inner side (IN side) in the width direction of the vehicle, and the IN side and OUT side are specified for explanation. However, in reality, the mounting direction of the front and back of the tire 1 on the vehicle is not specified.

[0012] The tread 10 has multiple main grooves 20, 21, 22 arranged axially around the entire tire. The multiple main grooves 20, 21, 22 include a pair of shoulder main grooves 20, 21 arranged closest to the axially opposite ground-contact edges of the tire, and one center main groove 22 arranged axially between the pair of shoulder main grooves 20, 21. The tread 10 has four lands 41, 42, 43, 44 separated by the three main grooves 20, 21, 22. Each shoulder main groove 20, 21 extends annularly in the tire circumferential direction while bending slightly axially. The center main groove 22 extends annularly in the tire circumferential direction while bending in a zigzag pattern.

[0013] The four lands 41, 42, 43, and 44 are protrusions that protrude radially outward from the reference plane of the tread 10. The "reference plane" is an imaginary plane that follows the bottom surfaces of the deepest main grooves 20, 21, and 22, and refers to the outer peripheral surface of the tread 10 when the lands 41, 42, 43, and 44 do not exist. The shoulder main grooves 20 and 21 and the center main groove 22 have approximately the same maximum radial depth.

[0014] The four lands 41, 42, 43, and 44 include a shoulder land 41 located axially outward of the outboard shoulder main groove 20, a first inner land 42 located between the shoulder main groove 20 and the center main groove 22, a second inner land 43 located between the center main groove 22 and the inboard shoulder main groove 21, and a shoulder land 44 located axially outward of the shoulder main groove 21. Thus, the tread 10 has two shoulder lands 41 and 44 located at both axial ends of the tire, and two inner lands 42 and 43 located between the two shoulder lands 41 and 44 and axially facing each other across the center main groove 22. Each inner land 42 and 43 is located between the two shoulder lands 41 and 44, with a pair of shoulder main grooves 20 and 21 between them. The center main groove 22 and each inner land 42 and 43 are located axially across the tire equator, i.e., the axial center CL (FIG. 2). Each of the inner lands 42 and 43 corresponds to an inner block group.

[0015] Each shoulder land 41, 44 is divided by lug grooves 50, 51 extending axially at multiple positions around the tire and is composed of multiple shoulder blocks 60, 61, 62, 63 arranged in the tire circumferential direction. Each shoulder block 60, 61, 62, 63 is located at a position that includes the ground contact edges T1, T2. Each inner land 42, 43 is formed into a rib-like shape that continues around the entire tire circumferential direction by connecting multiple inner blocks 70, 71 in the tire circumferential direction with multiple connecting ribs 72, 73 that extend in the tire circumferential direction.

[0016] The tire 1 includes a sidewall 12 that is provided axially outward of the tread 10 and bulges outward most axially, and a bead 14 that is fixed to the rim of a wheel. The sidewall 12 and the bead 14 are formed in an annular shape along the circumferential direction of the tire and form a tire side surface 13. The sidewall 12 extends radially inward from both axial ends of the tread 10.

[0017] The tire 1 is a pneumatic tire that is filled with air at a predetermined pressure. The tread 10 and the sidewall 12 are made of, for example, different types of rubber.

[0018] The shoulder lands 41, 44 disposed at both axial ends of the tread 10 include contact edges T1, T2 which are the axially outer ends of the contact surface.

[0019] The axial end of each shoulder land 41, 44 extends axially outward from the ground contact edges T1, T2 and curves gently radially inward so that the outer peripheral surface is convex outward. The portions of each shoulder land 41, 44 extending axially outward from the ground contact edges T1, T2 are called buttresses.

[0020] "Touching edges T1, T2" refer to both axial ends of the area of ​​the tire that comes into contact with a flat road surface when an unused tire 1 is mounted on a standard rim, inflated to the standard internal pressure, and subjected to a load of 70% of the standard load at the standard internal pressure.

[0021] Here, a "regular rim" is a rim specified by the tire standard, and is a "standard rim" for JATMA, a "design rim" for TRA, and a "measuring rim" for ETRTO. "Regular internal pressure" is the "maximum air pressure" for JATMA, the maximum value listed in the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" table for TRA, and "INFLATION PRESSURE" for ETRTO. "Regular load" is the "maximum load capacity" for JATMA, the maximum value listed in the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" table for TRA, and "LOAD CAPACITY" for ETRTO.

[0022] The tire 1 includes a carcass, a belt, and an inner liner. The carcass is a cord layer coated with rubber and forms the framework of the tire 1, which can withstand loads, impacts, air pressure, etc. The belt is a reinforcing band placed between the carcass and the rubber that makes up the tread 10. The belt tightly fastens the carcass, increasing the rigidity of the tire 1. The inner liner is a rubber layer provided on the inner surface of the carcass, and maintains the air pressure of the tire 1. The bead 14 includes a bead core and a bead filler.

[0023] [Configuration of tread features] 2, in the present embodiment, the first inner land 42 has two first protrusions 80 that are spaced apart in the tire circumferential direction when viewed from the outside in the tire radial direction, protruding toward the center main groove 22 in the tire axial direction and having a V-shaped edge on the contact patch facing the center main groove 22. Meanwhile, the second inner land 43 has a second protrusion 83 that protrudes toward the center main groove 22 in the tire axial direction when viewed from the outside in the tire radial direction, having a V-shaped edge on the contact patch facing the center main groove 22, and that is inserted into a first groove 81 that is a circumferential part of the V-shape of the center main groove 22 between the two first protrusions 80. The center main groove 22 is formed by connecting multiple V-shaped first grooves 81 that are oriented differently in the tire axial direction, alternately in the tire circumferential direction.

[0024] As shown in Figures 3 and 5, the tread 10 is formed with a first rib 74 that protrudes radially outward in the tire direction so as to be connected to the inside of the corners of the center main groove 22 and has dimples 75 on its radially outer surface that are recessed from the contact patch S1, and a second rib 76 that protrudes radially outward in the tire direction so as to be connected to the inside of the corners of the second protrusions 83 and has dimples 77 on its radially outer surface that are recessed from the contact patch S2. Each dimple 75, 77 corresponds to a shallow groove. The first rib 74 corresponds to a second block. This improves traction performance in the tire circumferential direction and suppresses early partial wear on dry roads.

[0025] Specifically, the inner block 70 constituting the first inner land 42 is formed into a shape including an inverted S-shape by alternately connecting a plurality of inclined portions U1, U3, and U5 inclined with respect to the tire circumferential direction and a plurality of circumferential portions U2, U4, and U6 extending in the tire circumferential direction. The inverted S-shape is the shape of an S when viewed from the back. The plurality of circumferential portions U2, U4, and U6 also have an end circumferential portion U6 provided at one end of the inner block 70 in the tire circumferential direction. The end circumferential portion U6 is disposed between both axial ends of the inner block 70 in the tire axial direction.

[0026] In this example, the first inner land 42 and the second inner land 43 are arranged in a state where their shapes, which are opposite to each other in the tire axial direction and the tire circumferential direction, are shifted by half a pitch in the tire circumferential direction and interdigitate with each other when viewed from the outside in the tire radial direction. Each inner land 42, 43 is formed by repeating a part of the shape in the tire circumferential direction multiple times around the entire tire.

[0027] Therefore, the inner block 71 constituting the second inner land 43 is formed into an inverted S-shape by connecting a plurality of inclined portions V1, V3, V5 inclined with respect to the tire circumferential direction and a plurality of circumferential portions V2, V4, V6 extending in the tire circumferential direction alternately one by one in the reverse order in the tire circumferential direction of the inner block 70. The plurality of circumferential portions V2, V4, V6 also have an end circumferential portion V6 provided at the other end of the inner block 71 in the tire circumferential direction. The end circumferential portion V6 is arranged between both axial ends of the inner block 71 in the tire axial direction.

[0028] At the ends of the ground contact surfaces of the inclined portions U1, U3, U5, V1, V3, and V5, the connecting portions with the wall surface on the side of the center main groove 22 are not chamfered but are angular. On the other hand, at the ends of the ground contact surfaces of the circumferential portions U2, U6, V2, and V6, the connecting portions with the wall surface on the side of the center main groove 22 are chamfered to have an arc-shaped cross section, as will be described later.

[0029] The corner where the first rib 74 is provided is substantially V-shaped when viewed from the outside in the tire radial direction, and the first rib 74 is provided at the back of the corner. As a result, the portion of the center main groove 22 provided inside the corner has a U-shape that widens toward the side away from the first rib 74, and is configured to include inclined portions U3 and U5 that are inclined in opposite directions around the tire circumferential direction, and a circumferential portion U4 that connects one end of the inclined portions U3 and U5 and extends around the tire circumferential direction.

[0030] As shown in FIG. 3, the first rib 74 has a contact surface S1, which is its top surface, that is generally U-shaped. The first rib 74 has a wall surface 75a that includes a generally U-shaped inclined surface on its inner side, and a bottom surface 75b connected to the bottom of the wall surface 75a, forming a dimple 75 that is recessed radially inward in the tire. The dimple depth d1 from the contact surface S1 to the bottom surface 75b is 50% or less of the maximum depth d2 of the center main groove 22. For example, the dimple depth d1 is 15% or more and 20% or less of the maximum depth d2 of the center main groove 22. As shown in FIG. 4, the bottom surface 75b of the dimple 75 and the bottom surface 22b of the center main groove 22 are smoothly connected by a curved surface that has a generally arc-shaped cross section.

[0031] Furthermore, as shown in FIGS. 3 and 5 , in the first inner land 42, a sipe 85, which is a thin line having a substantially U-shape when viewed from the outside in the tire radial direction, is formed between the U-shaped contact surface S1 of the first rib 74 and the edge of the contact surface S3 at the corner of the first inner land 42 on the side of the center main groove 22. Both ends of the sipe 85 open into the center main groove 22. As described below, the sipe 85 is smallest near the center of a circumferential portion 85a extending in the tire circumferential direction in the middle, and is deepest at leg portions 85b whose spacing widens toward the center main groove 22 at both ends. The inner block 70 including the U-shape at the corner surrounding the first rib 74 of the first inner land 42 and on the opposite side of the sipe 85 from the first rib 74 corresponds to the first block.

[0032] Meanwhile, the second rib 76 is provided on the inner block 71 of the second inner land 43, inside the corner of the second protrusion 83. When viewed from the outer side in the tire radial direction, the second protrusion 83 is generally J-shaped, widening toward the IN side, which is one side in the tire axial direction, and including inclined portions V1 and V3 inclined in opposite directions around the tire circumferential direction, and a circumferential portion V2 that connects one ends of the inclined portions V1 and V3 and extends around the tire circumferential direction.

[0033] As shown in FIG. 3 , one longitudinal end of an inner block 70 on one circumferential side of the tire faces the longitudinal end of the adjacent inner block 70 on that side of the tire in the tire circumferential direction, via a circumferential portion 86a of a V-shaped lug groove 86 extending in the tire circumferential direction. One end of the circumferential portion 86a is connected to the center main groove 22, and the other end is connected to an inclined portion 86b of the lug groove 86 that is inclined with respect to the tire circumferential direction. The inclined portion 86b faces a linear lug groove 87 inclined to the opposite side of the tire circumferential direction in the tire axial direction, via a circumferentially intermediate portion of the connecting rib 72. The connecting rib 72 corresponds to a second block.

[0034] As shown in FIG. 3 , the second rib 76 has a dimple 77 on its top surface that is recessed radially inward from the contact patch S2, which is the top surface of the corner of the second protrusion 83. When viewed from the radially outer side of the tire, the dimple 77 has a triangular shape with one corner removed. The periphery of the bottom surface 77a of the dimple 77 and the contact patch S2 of the second protrusion 83 are connected by a wall surface 77b that includes a sloped surface along the periphery of the bottom surface 77a. The wall surface 77b and the contact patch S2 are connected by a dimple chamfer 95 that is a curved surface with an arc-shaped cross section. The dimple 77 opens at the other circumferential end of the circumferential portion 88a of the V-shaped lug groove 88 and at the sloped portion 88b. The depth of the dimple 77 can be set to, for example, 5% to 50% of the maximum depth of the center main groove 22. The bottom surface 77a of the dimple 77 is connected to the wall surface of the lug groove 88.

[0035] The connecting rib 72 connecting the inner blocks 70 protrudes radially outward so as to extend in the tire circumferential direction. When viewed from the outside in the tire radial direction, the connecting rib 72 has a trapezoidal shape with its axially outer side longer than its axially inner side, and the height of the contact surface S5, which is its top surface, is approximately the same as the height of the contact surface S3 of each inner block 70. Both circumferential ends of the connecting rib 72 are connected to the two inner blocks 70, each extending circumferentially deeper than the circumferentially facing wall surfaces of the two circumferentially adjacent inner blocks 70. Furthermore, a dimple 90 is provided on the inside of the contact surface S5 of the connecting rib 72, extending in the tire circumferential direction and recessed radially inward. When viewed from the outside in the tire radial direction, the wall surface 90a of the dimple 90 has an oval shape extending in the tire circumferential direction. A dimple chamfer 90b with an arc-shaped cross section is formed at the top of an inclined surface that is inclined around the entire circumference of the dimple 90 relative to the contact surface S5 of the connecting rib 72. The above describes the connecting rib 72 that connects adjacent inner blocks 70, but the connecting rib 73 (Figures 2 and 3) that connects adjacent inner blocks 71 is similar to the connecting rib 72, except that its shape when viewed from the outside in the tire radial direction is opposite in the tire circumferential direction and tire axial direction.

[0036] Furthermore, on the contact surface of each inner land 42, 43, sipes 91, which are thin lines having a substantially U-shape when viewed from the outside in the tire radial direction, are formed between the contact surface S5 of the connecting rib 72, 73 and the contact surfaces S3, S2 of the inner blocks 70, 71. Both ends of the sipe 91 open to the inclined portions 86b, 88b of the V-shaped lug grooves 86, 88 and the lug grooves 87, 89. The depth of the sipe 91 is shallowest at the connection portions with the lug grooves 86, 87, 88, 89, gradually deepens toward the inner ends of the inner blocks 70, 71, and is deepest at the inner ends of the inner blocks 70, 71 at inclined portions 91a that are linearly inclined relative to the tire axial direction.

[0037] [Structure and effect of ribs inside corners] As described above, the first rib 74 and the second rib 76 that protrude radially outward are connected to the inside of both corners of the V-shaped first groove 81 and the second protrusion 83 that is inserted into the first groove 81, respectively, thereby increasing the rigidity near each corner. This makes it possible to suppress collapse of each corner and uneven wear. Therefore, at each corner, the angular edges of the inclined portions U3, U5, V1, and V3 that are inclined relative to the tire circumferential direction and face the center main groove 22 are more likely to exhibit an edge effect, thereby improving traction performance in the tire circumferential direction.

[0038] Furthermore, each rib 74, 76 has a dimple 75, 77 formed on its radially outer surface, recessed from the contact patch. This reduces the concentration of surface pressure near the edge of the contact patch when the corners touch down on a dry road, thereby preventing premature partial wear. Although the recessed shape from the contact patches S1, S2 tends to reduce rigidity, this reduction in rigidity can be compensated for by the reinforcement of each rib 74, 76. This prevents significant changes near the contact patches S1, S2 when the tire touches down. Increasing the rigidity near the corners in this way also helps prevent premature partial wear. This further improves handling and traction performance on dry roads, while also preventing premature partial wear.

[0039] Additionally, the dimples 75, 77 formed in each rib 74, 76 open to the center main groove 22 or lug grooves 86, 88 connected to the center main groove 22. This allows rainwater that seeps in between the tire's contact patch and the road surface when driving in the rain to flow from the dimples 75, 77 through the deeper center main groove 22 or lug grooves 86, 88 to the rear of the tire's direction of travel. This improves the tire's drainage performance.

[0040] As shown in Figures 3 and 6A, in each of the first inner land 42 and the second inner land 43, outer corner chamfers 92, 93 having an arc-shaped cross section are connected to the edges A1, A3 located on the outer side of the corner, opposite the inner side of the corner across the contact patch, and extending along the circumferential direction of the tire on the contact patch.

[0041] 6B, 6C, 6D, and 6E are enlarged views of section D, section E, section F, and section G of Fig. 6A, respectively. As shown in Fig. 6B, the outer corner chamfer 92 of the first inner land 42 is a portion connected to the contact patch S3 of the inner block 70, and is a main groove chamfer formed at the apex of the wall surface 20a on the tire axial center CL side that constitutes the shoulder main groove 20. The outer corner chamfer 92 corresponds to the first outer corner chamfer and the second chamfer.

[0042] As shown in Figure 6D, the outer corner chamfer 93 of the second inner land 43 is a main groove chamfer that is connected to the contact patch S2 of the inner block 71 and is formed on the apex of the wall surface 22a that constitutes the center main groove 22. The outer corner chamfer 93 of the second inner land 43 corresponds to the second outer corner chamfer and the second chamfer. This further reduces early wear near the circumferential edge in the early stages of wear compared to when there is no chamfer on the outer corner.

[0043] 3, 6A, 6C, and 6E, dimple chamfers 94, 95 with an arc-shaped cross section are formed at the tops of the wall surfaces 75a, 77b that form the dimples 75, 77 of each rib 74, 76. The dimple chamfers 94, 95 correspond to shallow groove chamfers. This also serves to prevent surface pressure from concentrating on the edges of the tire's contact patch, further suppressing early wear near the edges of the tire's contact patch in the early stages of wear.

[0044] As shown in Figures 6B and 6C, the radius of curvature Ra of the outer corner chamfer 92 of the first inner land 42 is greater than the radius of curvature Rb of the dimple chamfer 94 of the first rib 74. Also, as shown in Figures 6D and 6E, the radius of curvature Rc of the outer corner chamfer 93 of the second inner land 43 is greater than the radius of curvature Rd of the dimple chamfer 95 of the second rib 76. This allows the rubber to be appropriately compressed while suppressing inward deformation of the wall surfaces of the inner land 42, 43, depending on the maximum depths d3 and d2 of the shoulder main groove 20 and the center main groove 22, or the dimple depths d1 and d4. This effectively prevents pressure buildup at the edges of the contact patch of the inner land 42, 43. This effectively distributes the contact pressure across the contact patch, thereby effectively suppressing initial wear.

[0045] Furthermore, with reference to FIGS. 6B and 6D, the radius of curvature Ra of the outer corner chamfer 92 of the first inner land 42 is smaller than the radius of curvature Rc of the outer corner chamfer 93 of the second inner land 43.

[0046] [Structure and effect of chamfering on both sides of shoulder main groove] Furthermore, in the embodiment, edges A1, A2 located at the end of the contact surface of each inner land 42, 43 on the shoulder main groove 20, 21 side in the tire axial direction and running along the tire circumferential direction, and edges located at the end of the contact surface of each shoulder land 41, 44 on the shoulder main groove 20, 21 side in the tire axial direction and running along the tire circumferential direction, are connected to at least a portion of the tire circumferential direction by a chamfer having an arc-shaped cross section.

[0047] For example, as shown in FIGS. 3 and 6B, the edge A1 of the contact surface of the first inner land 42 on the shoulder main groove 20 side extends along the tire circumferential direction and is connected to a corner outer chamfer 92 with an arc-shaped cross section. Also, as shown in FIG. 3, the edge A2 of the contact surface of the second inner land 43 on the shoulder main groove 21 side extends along the tire circumferential direction and is connected to a chamfer 96 with an arc-shaped cross section. The edges A1 and A2 correspond to the first circumferential edges. The height-direction middle portion of the wall surface of each inner land 42, 43 on the shoulder main groove 20, 21 side is an inclined surface that slopes axially outward toward the tire radially outer side, as shown for the wall surface 20a of the inner land 42 in FIG. 6B. The middle portion of the wall surface 20a is inclined at a predetermined angle θ1, for example, 10 degrees or less, with respect to an imaginary plane 105 along the tire radial direction. The corner outer chamfer 92 is formed at the top of the wall surface 20a and connected to the inclined middle portion of the wall surface 20a.

[0048] 3, the edges B1, B2 of the contact-ground surfaces of the shoulder blocks 60, 61 constituting the shoulder land 41 on the main groove side are aligned along the tire circumferential direction, and at least a portion of each edge is connected to a chamfer 97, 98 with an arc-shaped cross section. The shoulder main groove 20-side edge and the shoulder main groove 20-side wall surface of the contact-ground surface of the shoulder block 61 are located closer to the tire axial center CL than the shoulder main groove 20-side edge and the shoulder main groove 20-side wall surface of the shoulder block 60. Accordingly, the wall surface of the first inner land 42 facing the shoulder block 61 is located closer to the tire axial center CL than the wall surface of the first inner land 42 facing the shoulder block 60. As a result, the wall surface of the first inner land 42 on the shoulder main groove 20 side has a shape in which the first land end J1 and a recess 150 recessed in the tire axial direction from the wall surface of the first land end J1 facing axially outward are arranged alternately in the tire circumferential direction. Similarly, the wall surface of the second inner land 43 on the shoulder main groove 21 side has a shape in which first land ends K1 and recesses 151 recessed in the tire axial direction relative to the wall surface of the first land end K1 facing axially outward in the tire circumferential direction are alternately arranged in the tire circumferential direction. Furthermore, outer chamfers 92 and 96 each having an arc-shaped cross section are formed at the top of the wall surface of each first land end J1, K1, respectively.

[0049] As a result, as will be described later, the occurrence of impact noise at the first land ends J1, K1 during tire rotation can be reduced, thereby suppressing pitch noise.

[0050] The edges B3, B4 of the contact surfaces of the shoulder blocks 62, 63 constituting the shoulder land 44 on the shoulder main groove 21 side are aligned along the tire circumferential direction, and are connected to at least a portion of the tire circumferential direction by chamfers 99, 100 having an arc-shaped cross section. The chamfers 97, 98, 99, 100 formed at the top of the wall surface on the contact edge T1, T2 side of each shoulder main groove 20, 21 in at least a portion of the tire circumferential direction, which are connected to the contact surfaces of the shoulder lands 41, 44, correspond to first chamfers.

[0051] As a result, the chamfers 92, 96, 97, 98, 99, and 100, which have an arc-shaped cross section, are connected to the edges located at the axial ends of the contact patch of each land 41, 42, 43, and 44. This prevents uneven wear and changes in the contact patch shape of each land 41, 42, 43, and 44 in the early stages of wear. In addition, the edges A1, A2, B1, B2, B3, and B4 to which the chamfers 92, 96, 97, 98, 99, and 100 are connected are aligned along the tire circumferential direction, preventing the chamfers 92, 96, 97, 98, 99, and 100 from deteriorating the traction performance in the tire circumferential direction.

[0052] As shown in FIG. 2, each of the inner lands 42, 43, which are connected around the entire circumferential circumference of the tire, has a plurality of edges A1, A2 connected by chamfers 92, 96 at the end of the shoulder main groove 20, 21 side, which is on one side or the other of the contact patch in the axial direction of the tire, along the tire circumferential direction. These edges A1, A2 are connected by chamfers 92, 96, and edges C1, C2 are formed as edges without chamfers and correspond to a plurality of second circumferential edges along the tire circumferential direction. Furthermore, the edge A1 (or A2) or a group of adjacent edges A1 (or A2) in each of the shoulder main grooves 20, 21 alternates with the edge C1 (or C2) or a group of adjacent edges C1 (or C2) in the tire circumferential direction. While FIG. 2 shows only a portion of the tread 10 around the tire circumferential direction, the shape of this portion of the tread 10 is repeated and connected throughout the entire circumferential direction of the tire.

[0053] The edges C1, C2 formed as edges along the tire circumferential direction at the ends of the inner land portions 42, 43 on the shoulder main groove 20, 21 side enhance the edge effect of the tire when cornering. Moreover, the edges A1 (or A2) or groups of adjacent edges A1 (or A2) of each shoulder main groove 20, 21 and the edges C1 (or C2) or groups of adjacent edges C1 (or C2) are alternately arranged in the tire circumferential direction, which achieves both the edge effect when cornering and suppression of sudden changes in the contact shape and uneven wear in the early stages of tire wear.

[0054] Furthermore, when the total length of the edge around the entire circumference of the tire is L1 and the total length of the edge around the entire circumference is L2, the relationship 0.4≦L1 / (L1+L2)≦0.9 is satisfied. This makes it easier to restrict the ratio of the edge connected to the chamfer to the ratio of the edge formed as an edge to the entire circumference within an appropriate range during one tire rotation, thereby achieving a better balance between the edge effect when the vehicle turns and the suppression of sudden changes in the contact shape and uneven wear in the early stages of wear.

[0055] According to the embodiment, the apex of the wall surface forming the shoulder main grooves 20, 21, where the apex connects to the ground contact surface of each inner land 42, 43, is formed with an outer corner chamfer 92 or chamfer 96 having an arc-shaped cross section, and the apex of the wall surface forming the dimple 75, where the apex connects to the ground contact surface of each inner land 42, 43, is formed with a dimple chamfer 94 having an arc-shaped cross section. This reduces the surface pressure exerted on the edges of the ground contact surface of each inner land 42, 43. Furthermore, as described above, the radius of curvature of the outer corner chamfer formed at the apex of the wall surface of the deeper shoulder main grooves 20, 21 is greater than the radius of curvature of the dimple chamfer 94 formed at the apex of the wall surface of the shallower dimple 75. This allows the rubber to be appropriately compressed while suppressing inward deformation of the wall surface of each inner land 42, 43, depending on the maximum depth of the shoulder main grooves 20, 21 or the dimple depth, when the wall surface of each inner land 42, 43 deforms due to tire contact with the ground. That is, the amount of rubber compression near the contact patch where the dimples 75 are formed is smaller than in the area where the shoulder main grooves 20 are formed, so the radius of curvature of the dimple chamfers 94 can be made smaller than in the area where the shoulder main grooves 20 are formed. This effectively prevents pressure from building up at the edges of the apexes of the inner lands 42, 43. This allows for dispersion of contact pressure across the contact patch, thereby effectively suppressing initial uneven wear.

[0056] Also, according to the embodiment, the radius of curvature of the outer corner chamfer 92 and the chamfer 96 is 6 mm or more, and the radius of curvature of the dimple chamfer 94 is less than 6 mm, for example, 5 mm or less.

[0057] Preferably, the radius of curvature Ra of the outer corner chamfer 92 is 40% to 85% of the maximum value of the shoulder main groove depth d3, and the radius of curvature Rb of the dimple chamfer 94 is 1 mm or greater. For example, the shoulder main groove depth d3 is 13 mm, and the dimple depth d1 is 3 mm. More preferably, the radius of curvature Rb of the dimple chamfer 94 is 2 mm or greater. For example, the radius of curvature Ra of the outer corner chamfer 92 can be 7 mm, and the radius of curvature Rb of the dimple chamfer 94 can be 4 mm. As shown in FIG. 6C for the inner land 42, a chamfer 101 having an arc-shaped cross section is also formed at the junction between the wall of each inner land 42, 43 on the center main groove 22 side and the bottom surface 75b of the dimple 75.

[0058] Furthermore, in at least a portion of the circumferential direction of each shoulder main groove 20, 21, chamfers 97, 98, 99, 100 with an arc-shaped cross section are formed on the apex of the wall surface on the side of the ground contact edge T1, T2, which connects to the ground contact surface of the shoulder land 41, 44. Furthermore, the outer corner chamfer 92 and chamfer 96 are formed on the apex of the wall surface of each shoulder main groove 20, 21 on the side of the axial center CL, which connects to the ground contact surface of the inner land 42, 43.

[0059] This prevents the pressure at the edges of the land on both sides of the shoulder main grooves 20, 21 from increasing when the tire makes contact with the ground, causing wiping deformation in which the rubber deforms toward the axial center of the tire. This effectively distributes the contact pressure at the contact patch, thereby more effectively suppressing initial uneven wear. This will be explained in detail using Figures 6F and 6G.

[0060] 6F is a schematic cross-sectional view showing the state of contact between the road surface 200 and the vicinity of the shoulder main grooves 20, 21 of the contact patches 15, 16 when no ground contact load is applied to tire 1b in a comparative example, and (b) is a view corresponding to (a) when a ground contact load is applied. In tire 1b of the comparative example shown in FIG. 6F, as shown in (a), no chamfer is formed between the tops of both side walls constituting the shoulder main grooves 20, 21 of the tread and the contact patches 15, 16, and edges 17, 18 of the contact patches 15, 16 on the shoulder main groove 20, 21 side are angular.

[0061] In tire 1b of this comparative example, when a ground contact load is applied to tire 1b as a reaction from the road surface due to the vehicle weight, as shown in (b), the rubber is compressed so that the wall surfaces on both sides of shoulder main grooves 20, 21 are pushed into shoulder main grooves 20, 21. Furthermore, due to wiping deformation, the rubber of tire 1b is likely to experience the highest ground contact pressure in the areas forming shoulder main grooves 20, 21. As a result, high ground contact pressure is generated at edges 17, 18 of contact surfaces 15, 16 on the shoulder main groove 20, 21 side, making it more likely for initial uneven wear to occur.

[0062] On the other hand, Figure 6G is a view corresponding to Figures 6F(a) and 6F(b) in an embodiment. As described above, in the embodiment, in the tire 1, chamfers 97, 98, 99, 100, 92, and 96 with an arc-shaped cross section are formed between the tops of both side walls constituting the shoulder main grooves 20 and 21 of the tread and the ground contact surfaces 15 and 16. In this embodiment, when a ground contact load is applied to the tire 1, deformation of the chamfers 97, 98, 99, 100, 92, and 96 can be prevented, so that the wall surfaces on both sides of the shoulder main grooves 20 and 21 are pushed into the groove. As a result, even when a ground contact load is applied to the tire 1, large ground contact pressure can be prevented from being generated at the edges 17 and 18 of the ground contact surfaces 15 and 16 on the shoulder main groove side, thereby suppressing initial uneven wear.

[0063] FIG. 6H is an H-H cross-sectional view of FIG. 2. As shown in FIGS. 3 and 6H, shoulder shallow grooves 106 are provided at both circumferential ends of the contact surface of each shoulder land 41, 44 on the shoulder main groove 20, 21 side. The shoulder shallow grooves 106 are provided in a generally U-shape along the periphery of the contact surface of each shoulder block 60, 61, 62, 63 on the shoulder main groove 20, 21 side. A wall surface 107 is provided between the bottom surface of the shoulder shallow groove 106 and the contact surface, which is the top surface of the shoulder block, and is inclined radially outward toward the circumferential center of the shoulder block. The wall surface 107 and the contact surface of the shoulder block are connected by a shallow groove chamfer 108 with an arc-shaped cross section. The shoulder shallow groove 106 is provided between adjacent shoulder blocks 60, 61, 62, 63 and opens into the lug grooves 50, 51 inclined relative to the tire axial direction and the shoulder main grooves 20, 21. The shallow groove depth from the bottom surface of the shoulder shallow groove 106 to the ground contact surface of the shoulder block can be set to, for example, 5 to 50% of the maximum depth d3 of the shoulder main groove.

[0064] This makes it easier for the shoulder shallow grooves 106 to compact mud on muddy ground, improving traction performance in the circumferential direction of the tire and more effectively dispersing ground pressure on the contact surface of the shoulder blocks, thereby more effectively suppressing initial uneven wear.

[0065] Additionally, in shoulder blocks provided with shoulder shallow grooves 106, chamfers 97, 98, 99, and 100 with an arc-shaped cross section are formed as main groove chamfers at the edges of the tops facing shoulder main grooves 20 and 21 and connecting to the wall surfaces of shoulder shallow groove 106. This allows for more effective distribution of ground pressure on the contact surface of the shoulder blocks, even when the ground pressure on the edges of shoulder shallow grooves 106 of the shoulder blocks increases, thereby more effectively suppressing initial uneven wear.

[0066] In the configuration of this example, the shoulder shallow groove 106 of the shoulder block is also provided on the wall surface on the shoulder main groove side in the circumferentially intermediate portion of the tire, so that it is provided so as to form a continuous U-shape when viewed from the radially outer side of the tire. On the other hand, the shoulder shallow groove 106 of the shoulder block may not be provided on the wall surface on the shoulder main groove side in the circumferentially intermediate portion of the tire, and two shoulder shallow grooves 106 may be provided separately at both circumferential ends of the shoulder block.

[0067] Two shallow grooves 109 are formed in the axially middle of the ground contact surface of each shoulder block, aligned in the circumferential direction of the tire. The two shallow grooves 109 are aligned approximately axially, and the wall surfaces on both sides of the shallow grooves 109 in the circumferential direction of the tire are inclined relative to the radial direction of the tire so that the distance between them increases radially outward. A chamfer with an arc-shaped cross section is formed at the connection between the inclined surfaces of the shallow grooves 109 and the ground contact surface of the shoulder block.

[0068] [Configuration and effect of chamfering near the sipe] Furthermore, in this embodiment, the above-mentioned sipes are formed on the contact surface of each inner land 42, 43. Specifically, as shown in Fig. 3, in each inner land 42, 43, sipes 85, which are thin lines that are approximately U-shaped when viewed from the outside in the tire radial direction, are formed between the U-shaped contact surface S1 of the first rib 74 and the edge of the contact surface S3 of the corner of each inner land 42, 43 on the center main groove 22 side. Furthermore, in the contact surface of each inner land 42, 43, sipes 91, which are thin lines that are approximately U-shaped when viewed from the outside in the tire radial direction, are formed in the portion that surrounds the contact surface at both ends of the connecting ribs 72, 73.

[0069] Furthermore, each inner land 42, 43 has a dimple 75, 90, which is a groove having an edge located within 10 mm of each sipe 85, 91, and is a groove to which a dimple chamfer 94, 90b with an arc-shaped cross section is connected at the edge. This prevents the inner land 42, 43 having the sipe 85, 91 from increasing in pressure at the edge near the sipe 85, 91, where ground pressure tends to be high. This allows the ground pressure on the contact surface where the sipe 85, 91 is formed to be dispersed, thereby preventing initial uneven wear. Furthermore, since there is no need to form a chamfer at the top of the wall surface of the sipe 85, 91, a decrease in the rigidity of the inner land 42, 43 is prevented.

[0070] Additionally, the wall surfaces of the dimples 75, 90 having the dimple chamfers 94, 90b are parallel to at least a portion of the sipes 85, 91. This further prevents high pressure at the edges near the sipes 85, 91, where high ground contact pressure is likely to occur, on the inner lands 42, 43. This further distributes the ground contact pressure on the contact surface where the sipes 85, 91 are formed, thereby further suppressing initial uneven wear.

[0071] Additionally, when viewed from the radially outer side of the tire, each sipe 85, 91 has a U-shape that surrounds the portion where the dimple chamfer 94, 90b of the dimple 75, 90 is formed. This allows the area of ​​the groove required to suppress initial uneven wear to be smaller than when the sipes are linear and grooves are provided near the sipes.

[0072] The maximum depth of each sipe 85, 91 is 40% or more of the maximum depth of each main groove 20, 21, 22, and each sipe 85, 91 is provided so as to divide each inner land 42, 43 when viewed from the outside in the tire radial direction.

[0073] Fig. 6I is a cross-sectional view taken along line II in Fig. 2. As shown in Fig. 6I, the sipe 85 has the smallest depth near the center of the circumferential portion 85a extending in the tire circumferential direction in the middle portion. The sipe 85 also has the deepest depth at the leg portions 85b where the spacing widens toward the center main grooves 22 at both ends, and the maximum depth is 40% or more of the maximum depth of each of the main grooves 20, 21, and 22.

[0074] Fig. 6J is a cross-sectional view taken along line JJ in Fig. 5. Fig. 6K is a cross-sectional view taken along line KK in Fig. 5. As shown in Figs. 6J and 6K, both ends of the sipe 91 open to the lug grooves 86 and 87. The sipe 91 is shallowest at the connection with the lug grooves 86 and 87, gradually deepens toward the inner end of the inner block 70, and is deepest at an inclined portion 91a inclined with respect to the tire circumferential direction at the inner end of the inner block 70. The maximum depth of the inclined portion 91a is 40% or more of the maximum depth of each main groove 20, 21, 22.

[0075] This allows the inner blocks 70, 71, the first rib 74, and the connecting rib 72, which are divided by the sipes 85, 91, to move more easily, making it easier to distribute the pressure on the contact surfaces of the inner lands 42, 43.

[0076] Furthermore, the inner lands 42, 43 on which the sipes 91 are formed have inner blocks 70, 71, which are first blocks having a concave shape provided on one side of the sipes 85, 91, and a first rib 74 and a connecting rib 72, which are second blocks having insertion portions provided on the other side of the sipes 85, 91 and positioned inside the concave shapes of the inner blocks 70, 71. The entire first rib 74 and both circumferential end portions of the connecting rib are the insertion portions.

[0077] Additionally, dimples 75, 90 with a depth smaller than the maximum depth of each main groove 20, 21, 22 are provided on the side of the first rib 74 and the connecting rib 72 away from the sipes 85, 91. The apex of the wall surface of the dimples 75, 90 is formed with dimple chamfers 94, 90b with an arc-shaped cross section. This prevents the inner blocks 70, 71 from collapsing between the separated portions on both sides of the U-shape by the first rib 74 and connecting ribs 72, 73 on the inside of the U-shape. Conversely, the collapse of the first rib 74 and connecting ribs 72, 73 is prevented by the inner blocks 70, 71. This increases the rigidity of the inner blocks 70, 71, the first rib 74, and the connecting ribs 72, 73. Furthermore, the contact pressure of the contact surface of each rib 74, 72, 73 can be dispersed, thereby suppressing initial uneven wear.

[0078] [Circumferential unevenness configuration of tire, and chamfer configuration and effect of the unevenness configuration] Furthermore, in this embodiment, the inner blocks 70, 71 constituting each inner land 42, 43 are arranged in the tire circumferential direction. The inner blocks 70, 71 include circumferential portions U2, V2, which are the axial ends of the tire, U-shaped wall surfaces formed by inclined portions U3, U5, V3, V5 and circumferential portions U4, V4, which are recessed in the tire axial direction from the wall surfaces of the circumferential portions U2, V2 facing the tire axial direction, and end circumferential portions U6, V6 connected to one circumferential end of the wall surfaces and extending in the tire circumferential direction. The axial ends of the circumferential portions U2, V2 are first land ends. The axial ends of the end circumferential portions U6, V6 are second land ends. Furthermore, chamfers 110, 111 with an arc-shaped cross section are formed at the tops of the wall surfaces of the circumferential portions U2, V2 facing the center main groove 22 in the tire axial direction, and at the tops of the wall surfaces of the end circumferential portions U6, V6 facing the circumferential portions 86a, 88a of the lug grooves 86, 88 in the tire axial direction.

[0079] As a result, each inner land 42, 43 has a shape in which a single land defines a first land edge, a second land edge, and a recess recessed in the axial direction from the wall surface of each land edge facing the tire axial direction, arranged in the tire circumferential direction in the order of the first land edge, the recess, and the second land edge. Furthermore, the chamfers 110, 111 described above are formed at the top of the wall surface facing the tire axial direction of each land edge. As described above, the first land edge, the recess, and the second land edge form unevenness in the tire circumferential direction, giving the center main groove 22 a zigzag shape, thereby reducing air columnar resonance noise, a type of tire noise. Furthermore, the chamfers 110, 111, each with an arc-shaped cross section, are formed at the top of the wall surface of each land edge, thereby reducing impact noise at each land edge during tire rotation, even when the vehicle weight is heavy. This suppresses pitch noise. Furthermore, the chamfers 110, 111 described above reduce pressure at the edge of the contact surface of each land edge during contact with the tire, thereby suppressing initial uneven wear.

[0080] Furthermore, in this embodiment, each inner land 42, 43 is a single land that constitutes one of a pair of wall surfaces on both axial sides of the shoulder main groove 20, 21. As described above, the wall surface of each inner land 42, 43 on the shoulder main groove 20, 21 side has a shape in which first land ends J1, K1 and recesses 150, 151 recessed in the tire axial direction from the wall surface facing axially outward of the first land ends J1, K1 are alternately arranged in the tire circumferential direction. Furthermore, outer chamfers 92 and 96 with arc-shaped cross sections are formed at the tops of the wall surfaces of each first land end J1, K1, respectively.

[0081] This creates unevenness in the tire circumferential direction, so that the shoulder main grooves 20, 21 extend circumferentially while bending in the tire axial direction, thereby reducing air columnar resonance noise. Furthermore, the outer chamfers 92 and 96, each with an arc-shaped cross section, are formed at the top of the wall surface of each first land end J1, K1, so that impact noise at the first land ends J1, K1 during tire rotation can be reduced, even when the vehicle weight is heavy. This further reduces pitch noise. Furthermore, the chamfers 92, 96 reduce the pressure at the edge of the contact surface of each first land end J1, K1 when the tire comes into contact with the ground, thereby suppressing initial uneven wear.

[0082] 1 and 6, in this embodiment, the shoulder blocks 60, 61 constituting the outboard shoulder land 41 of the pair of shoulder lands 41, 44 are arranged alternately in the tire circumferential direction, with shoulder blocks 60 having a first land end E1 and shoulder blocks 61 having a recess 114 recessed in the tire axial direction from a wall surface 116 of the first land end E1 facing axially outward. The shoulder blocks 60 correspond to the first blocks, and the shoulder blocks 61 correspond to the second blocks.

[0083] The recess 114 of the shoulder block 61 is provided in the circumferentially intermediate portion of the axially outer surface of the shoulder block 61 and extends radially. The recess 114 has a shape in which a pair of inclined surfaces that increase in depth from both radial ends toward the center of the tire and a pair of inclined surfaces that increase in depth from both radial ends toward the center of the tire are connected at their bottoms. The radially outer end of the recess 114 substantially coincides with the ground-contact edge T1.

[0084] On the other hand, the shoulder block 60 has a recess 115 provided on the radially inner portion of the tire at the circumferentially intermediate portion of the axially outer surface of the tire.

[0085] 6, the wall surface 116 of the first land end E1 of the shoulder block 60 is provided near the ground contact edge T1 and includes an inclined surface 116b that slopes axially outward toward the tire radially inward. As a result, the first land end E1 and the recess 114 form a circumferential unevenness in the tire circumferential direction, particularly at the tire radially outer end portion near the ground contact edge T1 on the axially outer surface of the tire.

[0086] Furthermore, a chamfer 116a having an arc-shaped cross section is formed at the top of the wall surface 116 of each first land end E1 facing axially outward, and the chamfer 116a connects the inclined surface 116b and the contact surface of the shoulder block 60.

[0087] As a result, the axially outer end of the shoulder land 41 has a shape in which the first land ends E1 and recesses 114 recessed in the tire axial direction from the wall surfaces 116 of the first land ends E1 facing the tire axial direction are alternately arranged in the tire circumferential direction by combining multiple shoulder blocks 60, 61. The chamfers 116a described above are formed at the tops of the wall surfaces 116 facing the tire axial direction of each first land end E1. The first land ends E1 and the recesses 114 thus form unevenness in the tire circumferential direction, improving traction performance on rough roads. Furthermore, the chamfers 116a, each with an arc-shaped cross section, are formed at the tops of the wall surfaces 116 of each first land end E1, reducing impact noise at the first land ends E1 during tire rotation, even when the vehicle weight is heavy. This further reduces pitch noise. Furthermore, the chamfers described above reduce contact pressure at the edges of the contact surface of each first land end E1, thereby suppressing initial uneven wear.

[0088] 7 and 8, in this embodiment, the shoulder blocks 62, 63 constituting the IN shoulder land 44 of the pair of shoulder lands 41, 44 are arranged alternately in the tire circumferential direction. The shoulder blocks 63 have a first land end F1, and the shoulder blocks have a wall surface 119 recessed in the tire axial direction from a wall surface 118 of the first land end F1 facing axially outward in the tire axial direction. The shoulder blocks 63 correspond to the first blocks, and the shoulder blocks 62 correspond to the second blocks. Specifically, the axially outer edge M1 of the top surface of the shoulder block 63, which includes the contact patch, extends axially outward by an amount δ as shown in FIG. 7 beyond the axially outer edge M2 of the top surface of the second shoulder block 62, which includes the contact patch. As a result, the wall surface 118 of the first land end F1 of the shoulder block 63, which includes the axially outer edge M1, and the wall surface 119 recessed at the axially outer end of the shoulder block 62 are arranged alternately in the tire circumferential direction.

[0089] Two recesses 120a, 120b, 121a, 121b extending radially and aligned in the tire circumferential direction are formed in the wall surfaces 119, 118 of each shoulder block 62, 63. Each recess 120a, 120b of the shoulder block 62 extends significantly in the tire radial direction so that both radial ends thereof nearly reach the radially inner and outer ends of the wall surface 119 of the shoulder block 62. Meanwhile, the radially inner ends of each recess 121a, 121b of the shoulder block 63 nearly reach the radially inner ends of the wall surface 118 of the shoulder block 63, but the radially outer ends of each recess 121a, 121b are shortened in the tire radial direction so as not to reach the radially outer ends of the wall surfaces 118.

[0090] In this way, the wall surfaces 119, 118 of each shoulder block 62, 63 are formed with recesses 120a, 120b formed in the wall surface 119 of the shoulder block 62 and wall surface 119 as a recess recessed axially inward from wall surface 118, so that when a vehicle travels on rough terrain, rocks, soil, mud, etc. are more easily caught in each recess, improving traction performance.

[0091] Furthermore, as shown in FIG. 8, a chamfer 118a having an arc-shaped cross section is formed at the top of the wall surface 118 of each first land end F1 facing outward in the tire axial direction.

[0092] As a result, the axially outer end of the shoulder land 44 has a shape in which the first land ends F1 and recesses recessed in the tire axial direction from the wall surfaces 118 of the first land ends F1 facing the tire axial direction are alternately arranged in the tire circumferential direction by combining multiple shoulder blocks 62, 63, which are lands. Furthermore, the chamfers 118a are formed at the tops of the wall surfaces 118 facing the tire axial direction of each first land end F1. This reduces the generation of impact noise at the first land ends F1 during tire rotation, even when the vehicle weight is heavy. This further suppresses pitch noise. Furthermore, the chamfers 118a reduce the pressure at the edges of the contact surface of each first land end F1 when the tire comes into contact with the ground, thereby suppressing initial uneven wear.

[0093] Note that the recesses 120a, 120b may not be formed on the wall surface 119 of the shoulder block 62 having the recessed wall surface 119. Even in this configuration, the unevenness formed in the tire circumferential direction, including the wall surface of the shoulder block 63, can improve traction performance on rough roads.

[0094] [Composition and effects of the inner land block shape] Furthermore, according to this embodiment, each inner land 42, 43 includes a plurality of inner blocks 70, 71 arranged side by side in the tire circumferential direction, with one axial end or the other end of the tire adjacent to one shoulder main groove 20 or the other shoulder main groove 21. Each inner block 70, 71 is formed into a shape including an inverted S-shape by alternately connecting a plurality of inclined portions U1, U3, U5, V1, V3, V5 inclined with respect to the tire circumferential direction and a plurality of circumferential portions U2, U4, U6, V2, V4, V6 extending in the tire circumferential direction.

[0095] The multiple circumferential portions U2, U4, U6, V2, V4, V6 each have an end circumferential portion U6, V6 provided at one circumferential end or the other circumferential end of the inner blocks 70, 71. Furthermore, the end circumferential portions U6, V6 are disposed between both axial ends of the inner blocks 70, 71 in the tire axial direction.

[0096] This allows the axial extent of the continuous portion of the ground contact patch to be expanded compared to a configuration in which three or more inner lands are provided between a pair of shoulder main grooves in the tread, separated in the axial direction by two or more circumferential main grooves along the tire circumferential direction. This improves the rigidity of the inner lands 42, 43 located between the pair of shoulder main grooves 20, 21. Furthermore, the inclined portions U1, U3, U5, V1, V3, V5 of the inner blocks 70, 71 improve circumferential traction performance. Furthermore, circumferential portions 86a, 88a can be formed adjacent to the end circumferential portions U6, V6, which can be located near the tire's axial center. This prevents a decrease in drainage performance due to a reduction in the number of circumferential main grooves along the tire circumferential direction between the pair of shoulder main grooves 20, 21 in the tread 10. This makes it possible to improve the rigidity of the inner land grooves 42, 43 arranged between the pair of shoulder main grooves 20, 21, improve the traction performance in the tire circumferential direction, and suppress a decrease in drainage performance.

[0097] The tread 10 also includes a first inner land 42 and a second inner land 43, which are two inner block groups arranged to intermesh with each other when viewed from the outside in the tire radial direction. This makes it possible to suppress collapse of the inner land 42, 43 at the contact portion of the tread 10 even if the inner land 42, 43 tends to collapse during running, thereby increasing the rigidity of the inner land 42, 43.

[0098] When a predetermined range in the tire circumferential direction of a set block group 130 consisting of two inner lands 42, 43 is viewed from the tire radially outer side, the set includes inclined portions 86b, 88b and lug grooves 87, 89 of lug grooves 86, 88, which are inclined grooves connected to at least one of the shoulder main grooves 20, 21 and the center main groove 22 and inclined relative to the tire circumferential direction, and circumferential portions 86a, 88a of the lug grooves 86, 88, which are circumferential grooves connected to the center main groove 22 and extending in the tire circumferential direction. In this case, the total area of ​​the inclined portions 86b, 88b and the circumferential portions 86a, 88a as inclined grooves connected to the center main groove 22 and not connected to either of the pair of shoulder main grooves 20, 21 is greater than the total area of ​​the lug grooves 87, 89 as inclined grooves connected to one or the other of the shoulder main grooves 20, 21. For example, in the length range of the tire circumferential direction block group 130 indicated by arrow G1 in Fig. 2, if the total area of ​​the lug grooves 87, 89 is S1a and the total area of ​​the inclined portions 86b, 88b and the circumferential portions 86a, 88a is S2a, then S2a > S1a. This increases the total area of ​​the inclined portions 86b, 88b, which are inclined grooves, and the circumferential portions 86a, 88a, which are circumferential grooves, in the axial central region of the tire where drainage performance is particularly required, thereby efficiently suppressing a decrease in drainage performance.

[0099] The multiple circumferential portions U2, U4, U6, V2, V4, V6 of the inner blocks 70, 71 are provided at the other end or one end of the inner blocks 70, 71 in the tire axial direction, which is the end that protrudes most in the tire axial direction, and include circumferential portions U2, V2 as protrusion-side circumferential portions that form protrusions that are convex on the other end or one end of the tire axial direction.

[0100] The ratio L1 / L2, which is the ratio of the second axial length L2 (FIG. 2) from the axial end of the inner blocks 70, 71 opposite the circumferential portions U2, V2 to the end of the end circumferential portions U6, V6 on the circumferential portions U2, V2 side, to the first axial length L1 (FIG. 2), which is the maximum axial length of the inner blocks 70, 71, is 1.9 or greater and 2.1 or less. This allows the axial lengths of the inclined portions U1, U3, U5, V1, V3, V5 of the inner blocks 70, 71 to be increased while improving drainage in the axial center region. This improves circumferential traction performance.

[0101] In addition, in the inner blocks 70 and 71, the angle formed by the extensions of the edges forming the center main groove 22 at the contact patch of at least two adjacent inclined portions U1, U3, U5, V1, V3, V5 among the multiple inclined portions U1, U3, U5, V1, V3, V5 is an acute angle. For example, the angle formed by the edges H1 and H2 in FIG. 2 is an acute angle. As a result, the inclined portions U1, U3, U5, V1, V3, V5 are arranged in a direction approaching the tire axial direction, thereby further improving the traction performance in the tire circumferential direction.

[0102] [Configuration of another example] Fig. 9 is a perspective view of a portion in the circumferential direction of a tire 1a according to another example of the embodiment. Fig. 10 is a plan view of the tire 1a, showing a portion in the circumferential direction of a tread 10a. Fig. 11 is a cross-sectional view taken along line NN of Fig. 10. Fig. 12 is a cross-sectional view taken along line PP of Fig. 10.

[0103] In the configuration of this example, in the tread 10a, the connecting ribs 140, 141 provided on the first inner land 42a and the second inner land 43a include two rib ends 142 at both ends in the tire circumferential direction, which extend from the tire circumferential side surfaces of the two inner blocks 70a, 71a to the inside of the inner blocks 70a, 71a. The top surfaces of the intermediate portions 143 of the connecting ribs 140, 141, which are located between the tire circumferential side surfaces of the two inner blocks 70a, 71a, are lower than the top surfaces of the rib ends 142.

[0104] 12, the top surface of the intermediate portion 143 is recessed in the shape of a valley with a generally V-shaped cross section so as to become deeper toward the tire circumferential center of the intermediate portion 143. Furthermore, a sipe 144 extending in the tire circumferential direction is formed in the tire axial center of the connecting ribs 140, 141.

[0105] Furthermore, shallow grooves 152 are formed on the top surfaces of the inner blocks 70a, 71a of the inner lands 42a, 43a at the ends of the shoulder main grooves 20, 21 in the circumferentially intermediate portions of the tire, forming triangular recesses as viewed from the radially outer side of the tire. The circumferential width of the shallow grooves 152 narrows toward the shoulder main grooves 20, 21 connected to the shallow grooves 152.

[0106] On the top surface of each inner block 70a, 71a, shallow grooves 145 are formed at the tips of the first protrusions 80a and second protrusions 83a in the circumferentially intermediate portion of the tire, forming triangular recesses as viewed from the radially outer side. The circumferential width of the shallow grooves 145 narrows toward the center main groove 22. The top of the wall surface of each shallow groove 145 is not chamfered to have an arc-shaped cross section, but forms an edge that is inclined with respect to the circumferential direction of the tire or that runs along the circumferential direction of the tire. This improves traction performance in the circumferential direction of the tire and enhances the edge effect when the vehicle is cornering.

[0107] Furthermore, a sipe 146 that is approximately U-shaped when viewed from the outside in the tire radial direction is formed on the contact surfaces of the shoulder blocks 60, 61, 62, and 63 of each shoulder land 41a and 44a. The sipe 146 is connected to both axial ends of the two shallow grooves 109a, and one axial end of the sipe 146 opens into the shoulder main grooves 20 and 21.

[0108] Sipes 147, 148, 149 inclined relative to the tire circumferential direction are also formed on the contact surfaces of the inner lands 42a, 43a. Some of the sipes 148, 149 are connected to the shallow grooves 145, and one end of the sipe 149 opens near the axial center of the center main groove 22. In this example, the other configurations and functions are the same as those in FIGS. 1 to 8.

[0109] FIG. 13 is a schematic diagram illustrating some blocks of the first inner land 42b and the second inner land 43b in a tire according to another embodiment. In the above embodiment, the inner blocks constituting each inner land have a shape that includes an inverted S-shape. In the configuration of this example, however, each inner block 70b, 71b is formed to have a shape that includes an S-shape. Specifically, in each inner block 70b, 71b, the tire circumferential arrangement of the multiple circumferential portions U2, U4, U6 and multiple inclined portions U1, U3, U5 of each inner block 70, 71 in the configurations shown in FIGS. 1 to 8 is reversed. Furthermore, the multiple blocks 70b, 71b constituting the two inner land 42b, 43b are arranged axially opposite each other, thereby forming a center main groove 22 between the two inner land 42b, 43b. In each of the inner land portions 42b, 43b, a plurality of inner blocks 70b, 71b adjacent to each other in the tire circumferential direction are connected to each other by connecting ribs (not shown in FIG. 13) that extend in the tire circumferential direction.

[0110] Even when the inner blocks 70b, 71b having the above-described shapes are used, similarly to the above-described examples, it is possible to simultaneously achieve improved rigidity of the inner lands 42b, 43b arranged between a pair of shoulder main grooves in the tread, improved traction performance in the tire circumferential direction, and suppressed deterioration of drainage. In this example, other configurations and functions are the same as those in Figures 1 to 8.

[0111] In the above examples, in each of the inner land sections 42, 43, 42a, 43a, 42b, and 43b, the inner blocks 70, 71, 70a, 71a, 70b, and 71b adjacent in the tire circumferential direction are connected by the connecting ribs 72, 73, 140, and 141. However, each of the inner land sections may be configured such that the multiple inner blocks lined up in the tire circumferential direction are not connected by the connecting ribs along the tire circumferential direction but are separated by grooves.

[0112] Furthermore, in the above embodiment, a case has been described in which the first rib 74 having the dimple 75 is connected to the inside of a corner of the V-shaped first groove 81 between the two first protrusions 80, 80a, and the second rib 76 having the dimple 77 is connected to the inside of a corner of the second protrusions 83, 83a that enter the first groove 81. However, a rib having a dimple that protrudes outward in the tire radial direction and is recessed from the ground contact patch on the tire radially outer surface may be connected to the inside of only one of the corners of the first groove and the second protrusion.

[0113] The present disclosure is further illustrated by the following embodiments. Configuration 1: A pneumatic tire having a tread having two shoulder lands provided at both ends of the tire axial direction, and two inner lands provided between the two shoulder lands and facing each other in the tire axial direction with main grooves interposed therebetween, The two inner land sections are a first inner land section having two first protrusions that are spaced apart in the tire circumferential direction, protrude toward the main groove in the tire axial direction, and have V-shaped edges on the main groove side in the contact patch when viewed from the outside in the tire radial direction, and a second inner land section having a second protrusion that protrudes toward the main groove in the tire axial direction, and has V-shaped edges on the main groove side in the contact patch when viewed from the outside in the tire radial direction, and that is inserted into the V-shaped first groove between the two first protrusions, a rib is formed on the outer surface in the tire radial direction, the rib protruding outward in the tire radial direction and having a dimple recessed from the ground contact surface, so as to be connected to the inside of at least one corner of the first groove and the second projection; Pneumatic tires. Configuration 2: The dimples open into the main grooves or into lug grooves connected to the main grooves. 10. The pneumatic tire according to claim 1. Configuration 3: In the first inner land or the second inner land, a corner outer chamfer having an arc-shaped cross section is located on the inside of the one corner and on the outside of the corner opposite to the contact patch, and is connected to an edge along the tire circumferential direction. 3. The pneumatic tire according to claim 1 or 2. Configuration 4: a dimple chamfer having an arc-shaped cross section is formed at the top of the wall surface forming the dimple; 4. The pneumatic tire according to any one of claims 1 to 3. Configuration 5: a dimple chamfer having an arc-shaped cross section is formed at the top of the wall surface forming the dimple, and the radius of curvature of the outer corner chamfer is greater than the radius of curvature of the dimple chamfer; 4. The pneumatic tire according to claim 3. Configuration 6: a first rib is connected to the inside of the corner of the first groove, and a second rib is connected to the inside of the corner of the second protrusion, 6. The pneumatic tire of any one of configurations 1 to 5. Configuration 7: In the first inner land, a first outer corner chamfer having an arc-shaped cross section is located on the outer side of the corner of the first groove, opposite the inner side of the corner with the contact patch therebetween, and is connected to an edge along the tire circumferential direction; and in the second inner land, a second outer corner chamfer having an arc-shaped cross section is located on the outer side of the corner of the second projection, opposite the inner side of the corner with the contact patch therebetween, and is connected to an edge along the tire circumferential direction. 7. A pneumatic tire according to claim 6. Configuration 8: The radius of curvature of the first outer corner chamfer is smaller than the radius of curvature of the second outer corner chamfer. 8. The pneumatic tire according to claim 7. Configuration 9: The dimple depth from the ground contact surface to the bottom of the dimple is 15% or more and 20% or less of the maximum depth of the first groove. 9. The pneumatic tire of any one of configurations 1 to 8. [Explanation of symbols]

[0114] 1,1a,1b Pneumatic tire (tire), 10,10a Tread, 12 Sidewall, 13 Tire side, 14 Bead, 15,16 Contact surface, 17,18 Edge, 20,21 Shoulder main groove, 22 Center main groove, 41 Shoulder land, 42,42a First inner land, 43,43a Second inner land, 44 Shoulder land, 50,51 Lug groove, 60,61,62,63 Shoulder block, 70,71,70a,71a Inner block, 72,73 Connecting rib, 74 First rib, 75 Dimple, 76 Second rib, 77 Dimple, 80,80a First protrusion, 81 First groove, 83,83a Second protrusion, 85 Sipe, 86,87,88,89 Lug groove, 90 Dimple, 91 Sipes, 92, 93 outer corner chamfers, 94, 95 dimple chamfers, 96, 97, 98, 99, 100, 101 chamfers, 105 imaginary planes, 106 shoulder shallow grooves, 107 wall surfaces, 108 shallow groove chamfers, 109, 109a shallow grooves, 110, 111 chamfers, 114, 115 recesses, 116, 118, 119 wall surfaces, 120, 121 130 group of blocks, 140, 141 connecting ribs, 142 rib ends, 143 middle portions, 144 sipes, 145 shallow grooves, 146 sipes, 147, 148, 149 sipes, 150, 151 recesses, 152 shallow grooves, 200 road surface.

Claims

1. A pneumatic tire having a tread having two shoulder lands provided at both ends of the tire axial direction, and two inner lands provided between the two shoulder lands and facing each other in the tire axial direction with main grooves interposed therebetween, The two inner land sections are a first inner land section having two first protrusions that are spaced apart in the tire circumferential direction, protrude toward the main groove in the tire axial direction, and have V-shaped edges on the main groove side in the contact patch when viewed from the outside in the tire radial direction, and a second inner land section having a second protrusion that protrudes toward the main groove in the tire axial direction, and has V-shaped edges on the main groove side in the contact patch when viewed from the outside in the tire radial direction, and that enters the V-shaped first groove between the two first protrusions, a rib that protrudes outward in the tire radial direction and has a dimple recessed from the ground contact surface on its outer surface in the tire radial direction so as to be connected to the inside of at least one corner of the first groove and the second projection; Pneumatic tires.

2. the dimples open into the main grooves or into lug grooves connected to the main grooves; The pneumatic tire according to claim 1 .

3. In the first inner land or the second inner land, a corner outer chamfer having an arc-shaped cross section is located on the inside of the one corner and on the outside of the corner opposite to the one corner across the contact patch, and is connected to an edge along the tire circumferential direction. The pneumatic tire according to claim 1 .

4. a dimple chamfer having an arc-shaped cross section is formed at the top of the wall surface forming the dimple; The pneumatic tire according to claim 1 .

5. a dimple chamfer having an arc-shaped cross section is formed at the top of the wall surface forming the dimple, and the radius of curvature of the outer corner chamfer is greater than the radius of curvature of the dimple chamfer; The pneumatic tire according to claim 3.

6. a first rib is connected to the inside of the corner of the first groove, and a second rib is connected to the inside of the corner of the second protrusion, The pneumatic tire according to claim 1 .

7. In the first inner land, a first outer corner chamfer having an arc-shaped cross section is located on the outer side of the corner of the first groove, opposite the inner side of the corner with the ground contact patch therebetween, and is connected to an edge along the tire circumferential direction; and in the second inner land, a second outer corner chamfer having an arc-shaped cross section is located on the outer side of the corner of the second projection, opposite the inner side of the corner with the ground contact patch therebetween, and is connected to an edge along the tire circumferential direction. The pneumatic tire according to claim 6.

8. The radius of curvature of the first outer corner chamfer is smaller than the radius of curvature of the second outer corner chamfer. The pneumatic tire according to claim 7.

9. a dimple depth from the ground contact surface to the bottom of the dimple is 15% or more and 20% or less of the maximum depth of the first groove; The pneumatic tire according to claim 1 .

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