tire

Abstract

To achieve a balance between snow traction performance, wear resistance, and stone drilling resistance. [Solution] The tread portion includes at least one circumferential main groove 20 extending along the tire circumferential direction, a plurality of center lug grooves 50 extending along the tire width direction and opening into the circumferential main groove 20 in the tire circumferential direction, a center block 301 partitioned by the circumferential main groove 20 and the center lug groove 50 and arranged in a staggered pattern via the circumferential main groove 20, and a widthwise bottom upper portion 55 protruding from a part of the groove bottom of the center lug groove 50 and connected to the groove wall of the center lug groove 50, wherein in one center lug groove 50, the total length L2 of the widthwise bottom upper portion 55 along the extending direction of the center lug groove 50 is longer than the length L1 of one opening end 50a of the groove width W1 of the center lug groove 50.

Description

Technical Field

[0001] This invention relates to a tire.

Background Art

[0002] Conventionally, for example, Patent Document 1 discloses a technique for improving the uneven wear resistance of a studless tire.

[0003] Also conventionally, for example, Patent Document 2 discloses a technique for improving the stone drilling resistance performance, in which at least one of the circumferential grooves and the widthwise grooves has a groove wall with a bent portion, and the groove width on the groove bottom side from the bent portion is formed narrower than the groove width of the opening portion.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] For example, in the case of studless tires in a category that is often used throughout the year, a block pattern tends to be adopted in order to drive on an icy or snowy road surface from a dry road surface. However, the block pattern has a large groove area, and there is a risk that the wear resistance performance and the stone drilling resistance performance will deteriorate.

[0006] An object of this invention is to provide a tire capable of achieving both snow traction performance and wear resistance performance and stone drilling resistance performance.

Means for Solving the Problems

[0007] To achieve the above objective, a tire according to one aspect of the present invention includes, in the tread portion, at least one circumferential main groove extending along the tire circumferential direction, a plurality of lug grooves extending along the tire width direction and opening into the circumferential main groove in a row along the tire circumferential direction, and arranged in a staggered pattern through the circumferential main groove, blocks partitioned by the circumferential main groove and the lug groove and arranged in a staggered pattern through the circumferential main groove, and a widthwise bottom portion protruding from a part of the groove bottom of the lug groove and connected to the groove wall of the lug groove, wherein in one lug groove, the total length of the widthwise bottom portion along the extending direction of the lug groove is longer than the length of one opening end of the groove width of the lug groove. [Effects of the Invention]

[0008] This invention makes it possible to achieve both snow traction performance and wear resistance and stone drilling resistance. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a meridional cross-sectional view of a pneumatic tire according to an embodiment. [Figure 2] Figure 2 is a plan view of the tread portion of a pneumatic tire according to an embodiment. [Figure 3] Figure 3 is a partially enlarged plan view of the tread portion of a pneumatic tire according to an embodiment. [Figure 4] Figure 4 is a partially enlarged cross-sectional view (cross-sectional view AA in Figure 3) of the tread portion of the pneumatic tire according to the embodiment. [Figure 5] Figure 5 is a partially enlarged plan view of the tread portion of a pneumatic tire according to an embodiment. [Figure 6] Figure 6 is a partially enlarged cross-sectional view of the tread portion of the pneumatic tire according to the embodiment (BB cross-sectional view in Figure 5). [Figure 7] Figure 7 is a partially enlarged plan view of the tread portion of a pneumatic tire according to an embodiment. [Figure 8] Figure 8 is a partially enlarged cross-sectional view of the tread portion of a pneumatic tire according to an embodiment. [Figure 9]Figure 9 is a chart showing the results of a performance test of a pneumatic tire according to the embodiment. [Figure 10] Figure 10 is a chart showing the results of a performance test of a pneumatic tire according to the embodiment. [Figure 11] Figure 11 is a chart showing the results of a performance test of a pneumatic tire according to the embodiment. [Figure 12] Figure 12 is a chart showing the results of a performance test of a pneumatic tire according to the embodiment. [Modes for carrying out the invention]

[0010] Embodiments of the present invention will be described in detail below with reference to the drawings. However, the present invention is not limited by these embodiments. Furthermore, the components of these embodiments include those that are substituted and obvious for substitution while maintaining the identity of the invention. In addition, the multiple modifications described in these embodiments can be arbitrarily combined within the scope of what is obvious to those skilled in the art.

[0011] In the following description, the tire radial direction refers to the direction perpendicular to the tire rotation axis (not shown), which is the rotation axis of the pneumatic tire 1 of the embodiment. The inner side of the tire radial direction refers to the side toward the tire rotation axis in the tire radial direction, and the outer side of the tire radial direction refers to the side away from the tire rotation axis in the tire radial direction. The tire circumferential direction refers to the direction around the tire rotation axis as the central axis. The tire width direction refers to the direction parallel to the tire rotation axis. The inner side of the tire width direction refers to the side toward the tire equatorial plane (tire equator line) CL in the tire width direction, and the outer side of the tire width direction refers to the side away from the tire equatorial plane CL in the tire width direction. The tire equatorial plane CL is a plane perpendicular to the tire rotation axis and passing through the center of the tire width of the pneumatic tire 1. The position of the tire equatorial plane CL in the tire width direction coincides with the tire width direction center line, which is the center position of the pneumatic tire 1 in the tire width direction. The tire equator line refers to a line on the tire equatorial plane CL that runs along the tire circumferential direction of the pneumatic tire 1. Furthermore, a meridional cross-section of a tire (meridian section) refers to the cross-section obtained when the tire is cut along a plane containing the tire's axis of rotation.

[0012] FIG. 1 is a meridian cross-sectional view of the pneumatic tire 1 of the embodiment. In this embodiment, a radial tire for heavy-duty vehicles, which is a tire mounted on a heavy-duty vehicle and is often used throughout the year, will be described as a studless tire in a category that is often used throughout the year.

[0013] The pneumatic tire 1 of the embodiment has an annular structure centered on the tire rotation axis, and includes a pair of bead cores 11, a pair of bead fillers 12, a carcass layer 13, a belt layer 14, a tread rubber 15, a pair of sidewall rubbers 16, and a pair of rim cushion rubbers 17.

[0014] The pair of bead cores 11 is formed by winding one or more bead wires made of steel in an annular and multiple manner, and are respectively embedded in the bead portions on both sides in the tire width direction to constitute the cores of the bead portions.

[0015] The pair of bead fillers 12 are respectively disposed on the outer circumference in the tire radial direction of the pair of bead cores 11 to reinforce the bead portions.

[0016] The carcass layer 13 has a single-layer structure composed of a single carcass ply or a multi-layer structure formed by laminating a plurality of carcass plies. In the pneumatic tire 1 of the embodiment, the carcass layer 13 is composed of a single carcass ply. The carcass layer 13 is bridged in a toroidal shape between the two bead cores to constitute the skeleton of the tire. Further, both ends of the carcass layer 13 are wound back and locked to the outside in the tire width direction so as to wrap the bead core 11 and the bead filler 12. In addition, the carcass layer 13 is formed by covering a plurality of carcass cords made of steel with a coating rubber and performing rolling processing, and in the case of a radial tire, it has a cord angle (defined as the inclination angle of the longitudinal direction of the carcass cord with respect to the tire circumferential direction) of 80° or more and 90° or less in absolute value.

[0017] The belt layer 14 is made up of multiple belt plies 141 to 144 stacked together and arranged around the outer circumference of the carcass layer 13. These belt plies 141 to 144 are a combination of belts of various configurations, such as zero-degree belts, high-angle belts, and a pair of crossing belts. The belt plies are made by coating multiple belt cords (also called wires) made of steel with rubber and rolling them. A zero-degree belt is defined as a belt ply in which the belt cords extend along the circumferential direction of the tire. A high-angle belt is defined as a belt ply in which the angle of inclination of the belt cords extending with respect to the circumferential direction of the tire is, for example, 45° to 70°. A pair of crossing belts has a so-called cross-ply structure in which each belt cord has a cord angle with a different sign from the others, and the extension directions of the belt cords are stacked together so as to intersect each other.

[0018] The tread rubber 15 is arranged on the outer circumference in the radial direction of the carcass layer 13 and belt layer 14 to form the tread portion of the pneumatic tire 1. In the tread portion, the tread rubber 15 forms a tread surface (also called a tread) 15A on the outer surface that comes into contact with the road surface during driving. The outer end of the tread surface 15A in the tire width direction becomes the contact end T (see Figure 2). The straight-line distance in the tire width direction when the tread surface 15A is unfolded between each contact end T is defined as the unfolded width TDW.

[0019] A pair of sidewall rubbers 16 are positioned on the outer side of the carcass layer 13 in the tire width direction, forming the sidewall portions on both sides of the pneumatic tire 1 in the tire width direction.

[0020] A pair of rim cushion rubbers 17 extend from the inside in the tire radial direction to the outside in the tire width direction of the folded-over portion of each bead core 11 and carcass layer 13, forming the rim fitting surface of the bead portion.

[0021] As shown in Figure 2, the pneumatic tire 1 of the embodiment has a tread pattern on the tread surface 15A of the tread portion. Here, each dimension of the tread pattern is measured in an unloaded state with the pneumatic tire 1 mounted on a specified rim and filled with a specified internal pressure. The above-mentioned contact end T is defined as the position of the maximum width in the tire width direction at the contact surface between the tread surface 15A and the flat plate when the tire is mounted on a specified rim, filled with a specified internal pressure, the tire equatorial plane CL is placed perpendicular to the flat plate, and a load corresponding to a specified load is applied.

[0022] A specified rim refers to a "standard rim" as defined by JATMA, a "design rim" as defined by TRA, or a "measuring rim" as defined by ETRTO. Furthermore, specified internal pressure refers to the "maximum air pressure" as defined by JATMA, the maximum value of "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" as defined by TRA, or "INFLATION PRESSURES" as defined by ETRTO. Finally, specified load refers to the "maximum load capacity" as defined by JATMA, the maximum value of "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" as defined by TRA, or "LOAD CAPACITY" as defined by ETRTO.

[0023] The groove width is measured as the maximum distance between opposing groove walls at the groove opening (opening end) on the surface of the tread surface 15A when the tire is mounted on a specified rim and filled to the specified internal pressure in an unloaded state. In configurations where the groove opening has a notch or chamfer, the groove width is measured using the intersection point of the extension line (profile) of the tread surface 15A and the extension line of the groove wall as the endpoint in a cross section parallel to the tire width direction and tire diameter direction.

[0024] The groove depth is measured as the maximum distance from the surface of the tread surface 15A to the bottom of the groove when the tire is mounted on a specified rim and filled to the specified internal pressure in an unloaded state. In addition, if the groove depth has a configuration with partial irregularities or sipes at the bottom of the groove, these are excluded from the measurement.

[0025] As shown in Figures 1 to 3, the pneumatic tire 1 of the embodiment has a circumferential main groove 20, lug grooves 50, 60, circumferential fine grooves 40, and sipes 71, 81 on the tread surface 15A of the tread portion.

[0026] The circumferential main grooves 20 are provided extending along the circumferential direction of the tire. In embodiments, at least four circumferential main grooves 20 are provided side by side in the tire width direction. In embodiments, the circumferential main grooves 20 include two center circumferential main grooves 21 provided on both sides of the tire equatorial plane CL in the tire width direction, and two shoulder circumferential main grooves 22 provided on the tire width side of each center circumferential main groove 21. Each circumferential main groove 20 may be defined as a groove that has a wear indicator display obligation as specified by JATMA.

[0027] The circumferential main groove 20 is formed to meander in the tire width direction while extending along the tire circumferential direction. Specifically, the circumferential main groove 20 has straight sections 20S along the tire circumferential direction and bent sections 20F that have angles in the tire circumferential and tire width directions. The bent sections 20F are positioned between the straight sections 20S, and the groove is formed to meander such that the straight sections 20S are shifted in position in the tire width direction via the bent sections 20F. As shown in Figures 3 and 6, the circumferential main groove 20 meanders with recesses 20D in which a part of the groove wall 20e of the straight section 20S is recessed in the tire width direction via the bent sections 20F, and protrusions 20P in which a part of the groove wall 20e of the straight section 20S protrudes in the tire width direction via the bent sections 20F. Also, as shown in Figure 3, the recesses 20D and protrusions 20P and recesses 20D are positioned opposite each other in the tire width direction on each groove wall 20e facing each other in the tire width direction, and are arranged alternately in the tire circumferential direction on one of the groove walls 20e.

[0028] The circumferential main groove 20 has a groove width W3 (dimension between the open ends 20a: see Figure 6) of 2.0 [mm] to 15.0 [mm]. The groove width W3 of the circumferential main groove 20 includes the maximum dimension W3a (see Figure 6) in the meandering tire width direction between the open ends 20a, and the minimum dimension 3Wb (see Figure 6) between the open ends 20a. The circumferential main groove 20 also has a groove depth D3 (dimension from the open end 20a to the groove bottom 20b: see Figure 6) of 7.0 [mm] to 26.0 [mm]. Furthermore, the maximum dimension W3a (see Figure 6) in the meandering tire width direction between the open ends 20a of the circumferential main groove 20 is 2.5 [mm] to 22.0 [mm]. The maximum dimension W3a is measured in one circumferential main groove 20 having the minimum dimension W3b.

[0029] Each circumferential main groove 20 defines land areas 31, 32, and 33 in the tire width direction. In this embodiment, the land areas 31, 32, and 33 include a single row of center land areas 31 located between two center circumferential main grooves 21 and provided on the tire equatorial plane CL, which is the center in the tire width direction; two rows of middle land areas 32 located between each center circumferential main groove 21 and each shoulder circumferential main groove 22; and two rows of shoulder land areas 33 located between each shoulder circumferential main groove 22 and each contact end T. The center land areas 31 and each middle land area 32 are collectively defined as the center land areas 30 located on the outer side in the tire width direction of each circumferential main groove 20 (shoulder circumferential main groove 22) in the tire width direction.

[0030] Although not explicitly shown in the diagram, in a configuration with one circumferential main groove 20, two rows of land areas corresponding to the shoulder land area 33 are partitioned, and the shoulder land area 33 does not exist. Also, although not explicitly shown in the diagram, in a configuration with five or more circumferential main grooves 20, six or more rows of land areas are partitioned, with each of the outermost land areas in the tire width direction being designated as the shoulder land area 33, and multiple adjacent rows of land areas on the inner side of each shoulder land area 33 in the tire width direction being designated as the center land area 30.

[0031] The lug groove 50, also called the center lug groove, extends along the tire width direction as shown in Figures 2 and 3, and divides each center land portion 30 into multiple sections in the tire circumferential direction. The center lug groove 50 includes a center lug groove 51 that divides the center land portion 31 and a middle lug groove 52 that divides the middle land portion 32.

[0032] As shown in Figures 2 and 3, the center lug grooves 50 are provided with their ends opening into each circumferential main groove 20 so as to penetrate each center land portion 30 in the tire width direction.

[0033] The center lug groove 50 has a groove width W1 of 2.0 mm to 10.0 mm (minimum dimension between the open ends 50a: see Figure 4). The center lug groove 50 also has a groove depth D1 of 4.0 mm to 26.0 mm (dimension from the open end 50a to the groove bottom 50b: see Figure 4).

[0034] As shown in Figure 2, the center lug groove 50 is formed such that the straight line connecting the centers of the groove width W1 (see Figure 4) at both ends that penetrate the center land portion 30 is inclined by more than ±5° with respect to the tire width direction. The center lug groove 50 has an angle θ1 (see Figure 2) with respect to the tire width direction that is between 5° and 45° in absolute value.

[0035] As shown in Figure 3, the center lug groove 50 has chamfered portions 50c formed at both ends that penetrate the center land portion 30, widening from the groove width W1 described above. The chamfered portions 50c are formed in a range of depth D2 (see Figure 4) from the opening end 50a of the center lug groove 50 to the upper bottom portion 55 in the width direction, which will be described later. In the center lug groove 50, the groove width W1 at both ends that serves as the reference for the straight line defining its angle θ1 is located at the position closest to the edge where there is no chamfered portion 50c. Furthermore, both ends of the center lug groove 50 open at the position of the bend 20F of the circumferential main groove 20. At its end, one of the chamfered portions 50c of the center lug groove 50 constitutes a part of the bend 20F of the circumferential main groove 20.

[0036] Furthermore, as shown in Figure 3, the center lug groove 50 is formed by bending midway between its two ends. Specifically, the center lug groove 50 has two bends 50F along its length, and includes two straight sections 50S extending towards the end closest to either of the bends 50F, and one straight section 50S between the two bends 50F. The two straight sections 50S (open ends 50a) extending towards the ends are arranged approximately parallel within a range of ±5[%], and the one straight section 50S (open end 50a) between the two bends 50F is inclined beyond a range of ±5[°] relative to the two straight sections 50S. Here, regarding the inclination angle of the straight section 50S (open end 50a) that forms the groove width W1 of the center lug groove 50 with respect to the tire width direction, as shown in Figure 3, the angle θa on the end side with respect to the tire width direction from the bent section 50F to the end in the extending direction is in the range of 5[°] to 45[°], and the angle θb of the straight section 50S (open end 50a) between the bent sections 50F with respect to the tire width direction is in the range of 6[°] to 90[°].

[0037] The center lug grooves 50 are arranged in a row in the circumferential direction of the tire, penetrating the center land portion 30, thereby dividing the center land portion 30 into multiple center blocks 301 in the circumferential direction of the tire. The center lug grooves 50 include a center lug groove 51 that defines the center block 301 of the center land portion 31 as a center block. The center lug grooves 50 also include a middle lug groove 52 that defines the center block 301 of the middle land portion 32 as a middle block. These center lug grooves 50 are arranged in a staggered pattern via the circumferential main grooves 20, so that each center block 301 is arranged in a staggered pattern via the circumferential main grooves 20.

[0038] Each of these center blocks 301 has an edge that runs along each groove 20, 50 due to the shape of the circumferential main groove 20, the shape of the center lug groove 50, and the staggered arrangement of each center block 301. Specifically, the edge of each center block 301 that runs along the open end 20a of the circumferential main groove 20 is formed by a straight portion running along the straight portion 20S of the circumferential main groove 20 and a bent portion that bends from the straight portion at the bent portion 20F between these straight portions, and there are no other parts that are cut out in the middle. Furthermore, each center block 301 has an edge along the open end 50a of the center lug groove 50, which is formed by a straight portion along the straight portion 50S of the center lug groove 50, a bent portion that bends from the straight portion at the bent portion 50F between the straight portions, and a bent portion at the end of each straight portion that follows the chamfered portion 50c of the center lug groove 50, and there are no other parts that are cut off in the middle.

[0039] As shown in Figure 2, the circumferential groove 40 extends along the circumferential direction of the tire and divides the shoulder portion 33 into an inner shoulder portion 33A and an outer shoulder portion 33B in the tire width direction. The circumferential groove 40 is formed with a groove width W5 (see Figure 8) that is narrower than that of the circumferential main groove 20. The circumferential groove 40 is bent in the tire width direction and has a zigzag shape.

[0040] The circumferential groove 40 has a groove width W5 of 1.5 mm to 16 mm (minimum dimension between the opening ends 40a: see Figure 8). The circumferential groove 40 also has a groove depth D5 of 3.5 mm to 23.5 mm (dimension from the opening end 40a to the groove bottom 40b: see Figure 8).

[0041] The lug groove 60, also called the shoulder lug groove, extends along the tire width direction as shown in Figure 2 and divides the inner shoulder portion 33A and the outer shoulder portion 33B into multiple sections in the circumferential direction of the tire. The lug groove 60 includes an inner shoulder lug groove 61 that divides the inner shoulder portion 33A and an outer shoulder lug groove 62 that divides the outer shoulder portion 33B.

[0042] The lug grooves 60 (inner lug groove 61 on the shoulder portion and outer lug groove 62 on the shoulder portion) have a groove width W6 of 1.5 mm to 10 mm (minimum dimension between the open ends 60a: see Figure 8). The lug grooves 60 also have a groove depth D6 of 3.5 mm to 23.5 mm (dimension from the open end 60a to the groove bottom 60b: see Figure 8).

[0043] As shown in Figure 2, the inner shoulder lug groove 61 is provided so as to penetrate the inner shoulder land portion 33A in the tire width direction, with one end opening into the outermost circumferential main groove 20 (shoulder circumferential main groove 22) in the tire width direction, and the other end opening into the bent portion of the circumferential narrow groove 40 that faces inward in the tire width direction. The centerlines of the groove width W6 (see Figure 8) of the inner shoulder lug groove 61 are arranged to be approximately parallel to the tire width direction within a range of ±5[°]. At the end of the inner shoulder lug groove 61 that penetrates the inner shoulder land portion 33A, a chamfered portion 60c is formed so as to widen from the groove width W6. The chamfered portion 60c is formed on only one side of the groove width W6 of the inner shoulder lug groove 61 and is formed in the range from the opening end 60a of the inner shoulder lug groove 61 to the groove bottom 60b (groove depth D6: see Figure 8). Furthermore, one end of the inner lug groove 61 of the shoulder portion opens at the position of the bend 20F of the circumferential main groove 20. At one end of the inner lug groove 61 of the shoulder portion, the chamfered portion 60c forms part of the bend 20F of the circumferential main groove 20. Multiple inner lug grooves 61 of the shoulder portion are arranged in the circumferential direction of the tire and penetrate the inner land portion 33A of the shoulder portion, thereby dividing the inner land portion 33A of the shoulder portion into multiple inner blocks 33A1 of the shoulder portion in the circumferential direction of the tire.

[0044] As shown in Figure 2, the outer shoulder lug groove 62 is provided so as to penetrate the outer shoulder land portion 33B in the tire width direction, with one end opening at the bent portion of the circumferential narrow groove 40 facing outward in the tire width direction, and the other end opening at the contact end T. The centerlines of the groove width W6 (see Figure 8) of the outer shoulder lug groove 62 are arranged to be approximately parallel to the tire width direction within a range of ±5[°]. The outer shoulder lug groove 62 is arranged to be approximately parallel to the inner shoulder lug groove 61, with their respective centerlines within a range of ±5[°]. At the other end of the outer shoulder lug groove 62 that penetrates the outer shoulder land portion 33B, a tapered portion 60d is formed so as to widen from the groove width W6. The tapered portion 60d is formed in the range from the opening end 60a of the outer shoulder lug groove 62 to the groove bottom 60b (groove depth D6: see Figure 8). The tapered portion 60d is formed in every other shoulder portion outer lug groove 62, which are arranged in multiple rows in the circumferential direction of the tire. These shoulder portion outer lug grooves 62 are arranged in multiple rows in the circumferential direction of the tire and penetrate the shoulder portion outer land portion 33B, thereby dividing the shoulder portion outer land portion 33B into multiple shoulder portion outer blocks 33B1 in the circumferential direction of the tire.

[0045] The inner lug groove 61 and the outer lug groove 62 of the shoulder portion are provided with alternating openings relative to the circumferential narrow groove 40 in the circumferential direction of the tire. Therefore, the inner block 33A1 and the outer block 33B1 of the shoulder portion are arranged in a staggered pattern via the circumferential narrow groove 40.

[0046] The inner shoulder block 33A1 has edges formed along each groove 20, 40, and 61 due to the shape of the circumferential main groove 20 (shoulder circumferential main groove 22), the shape of the circumferential narrow groove 40, and the shape of the inner shoulder lug groove 61. Specifically, the edge of the inner shoulder block 33A1 along the opening end 20a of the circumferential main groove 20 is formed by a straight portion along the straight portion 20S of the circumferential main groove 20 and a bent portion that bends from the straight portion at the bent portion 20F between these straight portions, with no other parts cut off in the middle. Similarly, the edge of the inner shoulder block 33A1 along the opening end 40a of the circumferential narrow groove 40 is formed by straight portions on both sides of a single bent portion, with no other parts cut off in the middle. Furthermore, the inner shoulder block 33A1 has an edge along the open end 60a of the inner shoulder lug groove 61 that is formed as a straight section substantially parallel to the tire width direction, and there are no other sections that are cut out in the middle.

[0047] The outer shoulder block 33B1 has edges formed along each groove 40 and 62 due to the shape of the circumferential narrow groove 40 and the shape of the outer shoulder lug groove 62. Specifically, the edge of the outer shoulder block 33B1 along the open end 40a of the circumferential narrow groove 40 is formed by straight sections on both sides of a single bend, and there are no other sections that are cut off in the middle. Similarly, the edge of the outer shoulder block 33B1 along the open end 60a of the outer shoulder lug groove 62 is formed by a straight section, and there are no other sections that are cut off in the middle.

[0048] As shown in Figure 2, the sipes 71 are provided on each center block 301 of each center land portion 30. The sipes 71 are called open sipes and are provided extending along the tire width direction, with at least one end opening into the circumferential main groove 20. In this embodiment, all sipes 71 have both ends opening into the circumferential main groove 20. The sipes 71 are formed in a zigzag shape on the tread surface 15A. The sipes 71 are formed in a straight line in the depth direction (depth D7: see Figure 8). The sipes 71 may also be formed in a zigzag shape in the depth direction. In addition to the open sipes 71 described above, the sipes 71 provided on the center land portion 30 may also be closed sipes, with both ends closed within the block.

[0049] The sipe 71 has a groove width W7 of less than 1.0 mm (minimum dimension: see Figure 8). The sipe 71 also has a depth D7 of 3.5 mm or more and 23.5 mm or less (dimension from the opening end to the bottom of the groove: see Figure 8).

[0050] The sipes 71 are arranged so that the straight line connecting both ends is inclined beyond ±5° with respect to the tire width direction. The straight line connecting both ends of the sipes 71 are arranged approximately parallel to the tire width direction within a range of ±5° with respect to the angle θa on the end side with respect to the tire width direction, from the bent portion 50F of the center lug groove 50 to the end in the extending direction. The sipes 71 provided on the center block 301 are arranged approximately parallel to each other within a range of ±5°.

[0051] As shown in Figure 2, the sipes 81 are provided on each inner block 33A1 and each outer block 33B1 of each shoulder portion land portion 33. The sipes 81 are called closed sipes, and are provided extending along the tire width direction, with both ends closed within the block. The sipes 81 are formed in a zigzag shape on the tread surface 15A. The sipes 81 are formed in a straight line in the depth direction (depth D8: see Figure 8). The sipes 81 may also be formed in a zigzag shape in the depth direction. It is preferable that all the sipes 81 provided on each inner block 33A1 and each outer block 33B1 of each shoulder portion are closed sipes.

[0052] Sipe 81 has a groove width W8 of less than 1.0 mm (minimum dimension: see Figure 8). Sipe 81 also has a depth D8 of 3.5 mm or more and 23.5 mm or less (dimension from the opening end to the bottom of the groove: see Figure 8).

[0053] The sipes 81 have a straight line connecting both ends that is arranged approximately parallel to the inner lug groove 61 and outer lug groove 62 of the shoulder section, within a range of ±5° with respect to the tire width direction. The sipes 81 provided on one inner shoulder block 33A1 and one outer shoulder block 33B1 are arranged approximately parallel to each other within a range of ±5°.

[0054] In addition to the above configuration, the pneumatic tire 1 of this embodiment has a widthwise bottom upper part 55 positioned at the bottom 50b of the center lug groove 50, as shown in Figure 4, and a circumferential bottom upper part 25 positioned at the bottom 20b of the circumferential main groove 20, as shown in Figure 6. The widthwise bottom upper part 55 and the circumferential bottom upper part 25 are shown in each plan view with multiple lines in the circumferential direction of the tire to distinguish them from other parts.

[0055] The widthwise bottom portion 55 is positioned to protrude from a part of the groove bottom 50b of the center lug groove 50 and to connect with at least one groove wall 50e (see Figure 4) of the center lug groove 50. In the plan view shown in Figure 3, the widthwise bottom portion 55 is positioned to connect with one groove wall 50e from one end of the center lug groove 50 toward the center in the extending direction of the center lug groove 50, and to connect with the other groove wall 50e from the other end of the center lug groove 50 toward the center in the extending direction of the center lug groove 50, and is positioned opposite to the groove width W1 of the center lug groove 50 in the straight portion 50S between the central bend portion 50F in the extending direction of the center lug groove 50.

[0056] The circumferential bottom upper portion 25 is positioned to protrude from a portion of the groove bottom 20b of the circumferential main groove 20 and to connect with at least one groove wall 20e (see Figure 6) of the circumferential main groove 20. The circumferential bottom upper portion 25 is positioned in the recess 20D of the circumferential main groove 20 and is positioned within the range of the recess 20D in the plan view shown in Figure 3.

[0057] The pneumatic tire 1 of the embodiment is characterized as follows, as shown in Figures 2 to 4, in the tread portion, at least one circumferential main groove 20 extending along the tire circumferential direction, a plurality of center lug grooves 50 extending along the tire width direction and opening into the circumferential main groove 20 in a row along the tire circumferential direction and arranged in a staggered pattern via the circumferential main groove 20, and a section partitioned by the circumferential main groove 20 and the center lug groove 50 and arranged in a staggered pattern via the circumferential main groove 20. The center section block 301 includes, as shown in Figure 4, a widthwise bottom upper section 55 that protrudes from a part of the groove bottom 50b of the center section lug groove 50 and is connected to the groove wall 50e of the center section lug groove 50. In one center section lug groove 50, as shown in Figure 3, the total length L2 (shown as a dashed line in Figure 3) of the widthwise bottom upper section 55 along the extending direction of the center section lug groove 50 is longer than the length L1 (shown as a thick solid line in Figure 3) of one open end 50a of the groove width W1 of the center section lug groove 50.

[0058] In the case of a single circumferential main groove 20, the center block 301, which is demarcated by the circumferential main groove 20 and the center lug groove 50, is arranged as a shoulder block that forms the ground contact end T.

[0059] According to this pneumatic tire 1, the center lug groove 50 has a widthwise bottom upper part 55, which prevents foreign objects such as stones from entering the groove bottom 50b of the center lug groove 50, thereby improving resistance to stone drilling, and also increases the rigidity of the center block 301, thereby improving wear resistance. Moreover, according to this pneumatic tire 1, the center lug groove 50 is arranged in a staggered pattern via the circumferential main groove 20, so there are no wide grooves where the openings of the center lug groove 50 face each other via the circumferential main groove 20, which prevents foreign objects such as stones from entering the intersection of the center lug groove 50 and the circumferential main groove 20, thereby improving resistance to stone drilling. Furthermore, with this pneumatic tire 1, by making the total length L2 of the upper bottom portion 55 in the width direction along the extending direction of the center lug groove 50 longer than the length L1 of one open end 50a of the groove width W1 of the center lug groove 50, the upper bottom portion 55 in the width direction has a portion where it faces the groove walls 50e of the center lug groove 50 within the length L1 of the center lug groove 50, thereby preventing foreign objects such as stones from entering the groove bottom 50b of the center lug groove 50 and improving resistance to stone drilling. Moreover, with this pneumatic tire 1, by having the upper bottom portion 55 in the width direction in a part of the center lug groove 50, groove volume is secured and snow traction performance is maintained by obtaining shear force in the snow. As a result, this pneumatic tire 1 can achieve both snow traction performance and wear resistance and stone drilling resistance. In this pneumatic tire 1, if the shoulder portion lug groove 60 is included, it is preferable that the center lug groove 50 occupies 30% or more of all lug grooves in the tread portion in order to obtain the above effects.

[0060] In this pneumatic tire 1, it is preferable that the maximum dimension WC (see Figure 3) in the tire width direction of the center portion 30 satisfies the relationship 5.0 ≤ WC / TDW ≤ 30.0 between the maximum dimension WC (see Figure 3) in the tire width direction of the shoulder portion 33 and the maximum dimension WC (see Figure 3) of the center portion 30 in the tire width direction of the center portion 30 satisfies the relationship 10.0 ≤ WS / WC ≤ 35.0. In this pneumatic tire 1, the block rigidity of the tread portion can be maintained in relation to each portion 30,33, thereby improving wear resistance.

[0061] Furthermore, in this pneumatic tire 1, the open sipes 71 are preferably formed with a tire width dimension of 90% or more, with the tire width dimension when both ends penetrate the center block 301 being 100%. The closed sipes 81 are preferably formed with a tire width dimension of 10% to 80%, with the maximum tire width dimension of the inner shoulder block 33A1 and outer shoulder block 33B1 being 100%. In this pneumatic tire 1, the edge component of the open sipes 71 in the tire width dimension can be increased to improve snow traction performance, and the edge component of the closed sipes 81 can be increased while maintaining block rigidity to achieve both snow traction performance and wear resistance.

[0062] Furthermore, in the pneumatic tire 1 of the embodiment, as shown in Figure 4, the groove width W1 of the center lug groove 50 and the width W2 of the widthwise bottom upper part 55 (if the widthwise bottom upper part 55 is continuous with both groove walls 50e of the center lug groove 50, the sum of the widths W2) satisfy the relationship 0.2 ≤ W2 / W1.

[0063] The width W2 of the upper bottom portion 55 in the width direction is the shortest distance between the portion of the upper bottom portion 55 rising from the groove bottom 50b of the center lug groove 50 and the portion of the upper bottom portion 55 connecting to the groove wall 50e of the center lug groove 50, as shown in Figure 4. The portion of the upper bottom portion 55 rising from the groove bottom 50b of the center lug groove 50 is defined as the intersection point between the rising surface and a virtual line extending in the tire width direction from the upper end of the upper bottom portion 55 in the width direction. Furthermore, the portion of the upper bottom portion 55 connecting to the groove wall 50e of the center lug groove 50 is defined as the intersection point between the extension of the groove wall 50e of the center lug groove 50 and a virtual line extending in the tire width direction from the upper end of the upper bottom portion 55 in the width direction.

[0064] This pneumatic tire 1 satisfies the relationship 0.2 ≤ W2 / W1, thereby preventing foreign objects such as stones from entering the groove bottom 50b of the center lug groove 50 through the upper bottom 55 in the width direction, improving resistance to stone drilling, and increasing the rigidity of the center block 301 to improve wear resistance. Furthermore, this pneumatic tire 1 utilizes the groove bottom 50b of the center lug groove 50 to secure groove volume, obtain shear force in the snow, and maintain snow traction performance. In this pneumatic tire 1, it is preferable to satisfy the relationship 0.2 ≤ W2 / W1 ≤ 0.6 in order to obtain the above effects.

[0065] Furthermore, in the pneumatic tire 1 of the embodiment, as shown in Figure 4, the groove depth D1 of the center lug groove 50 and the depth D2 of the upper part of the bottom 55 in the width direction satisfy the relationship 0.5 ≤ D2 / D1 ≤ 0.9.

[0066] Here, the depth D2 of the upper part 55 in the width direction is the dimension from the opening end 50a of the center lug groove 50 to the upper end of the upper part 55 in the width direction, as shown in Figure 4.

[0067] According to this pneumatic tire 1, by satisfying the relationship 0.5 ≤ D2 / D1 ≤ 0.9, the upper bottom portion 55 in the width direction prevents foreign objects such as stones from entering the groove bottom 50b of the center lug groove 50, thereby improving resistance to stone drilling, and also increases the rigidity of the center block 301, improving wear resistance. Moreover, according to this pneumatic tire 1, groove volume is secured, and shear force in the snow is obtained to maintain snow traction performance.

[0068] Furthermore, in the pneumatic tire 1 of the embodiment, as shown in Figure 3, the center lug groove 50 has two bends 50F along its extension, and the angle θb between the bends 50F is greater than the angle θa from the bend 50F to the end in the extension direction of the open end 50a that forms the groove width W1.

[0069] According to this pneumatic tire 1, by having a bent section 50F, an edge component is obtained to improve snow traction performance, and by overlapping the center blocks 301, which are arranged in the circumferential direction of the tire, in the tire width direction due to the inclination of the center lug groove 50, rigidity is improved and wear resistance is improved.

[0070] Furthermore, in the pneumatic tire 1 of this embodiment, as shown in Figure 3, the center lug groove 50 has two bends 50F along its extension, and the widthwise bottom upper part 55 is arranged in conjunction with both groove walls 50e of the center lug groove 50 between the bends 50F.

[0071] In this pneumatic tire 1, the bent section 50F is wider than the groove width W1, making it prone to getting stuck in foreign objects such as stones. However, in this bent section 50F, the widthwise bottom upper part 55 is placed on both groove walls 50e of the center lug groove 50 to improve resistance to stone drilling.

[0072] Furthermore, in the pneumatic tire 1 of the embodiment, as shown in Figure 3, the center lug groove 50 includes a circumferential bottom upper portion 25 that protrudes from a part of the groove bottom 20b of the circumferential main groove 20 and is connected to the groove wall 20e of the circumferential main groove 20. When projected in the extending direction of the center lug groove 50, the circumferential bottom upper portion 25 and the widthwise bottom upper portion 55 overlap in the portion where the center lug groove 50 opens into the circumferential main groove 20, and the wall of the center block 301 facing the opening of the center lug groove 50 via the circumferential main groove 20 corresponds to the bent portion 20F of the circumferential main groove 20 and is formed to protrude toward the opening of the center lug groove 50.

[0073] In this pneumatic tire 1, the intersection where the center lug groove 50 opens into the circumferential main groove 20 is prone to trapping foreign objects such as stones. However, in this area, the circumferential bottom upper part 25 and the widthwise bottom upper part 55 are positioned in the extending direction of the center lug groove 50 to improve resistance to stone drilling. Furthermore, in this pneumatic tire 1, the wall of the center block 301 is positioned to protrude at the intersection of the center lug groove 50 and the circumferential main groove 20 toward the opening of the center lug groove 50, thereby improving resistance to stone drilling while increasing the edge component and maintaining snow traction performance.

[0074] Furthermore, in the pneumatic tire 1 of the embodiment, as shown in Figures 5 and 6, it includes a circumferential bottom upper part 25 that protrudes from a part of the groove bottom 20b of the circumferential main groove 20 and is connected to the groove wall 20e of the circumferential main groove 20, and the groove width W3 of the circumferential main groove 20 and the width W4 of the circumferential bottom upper part 25 (if the circumferential bottom upper part 25 is connected to both groove walls 20e of the circumferential main groove 20, the width W4 is the sum of the widths W4) satisfy the relationship 0.2 ≤ W4 / W3.

[0075] The width W4 of the circumferential bottom upper part 25 is the shortest distance between the portion of the circumferential bottom upper part 25 that rises from the groove bottom 20b of the circumferential main groove 20 and the portion of the circumferential bottom upper part 25 that connects to the groove wall 20e of the circumferential main groove 20, as shown in Figure 6. The portion of the circumferential bottom upper part 25 that rises from the groove bottom 20b of the circumferential main groove 20 is defined as the intersection point between the rising surface and a virtual line extending in the tire width direction from the upper end of the circumferential bottom upper part 25. Furthermore, the portion of the circumferential bottom upper part 25 that connects to the groove wall 20e of the circumferential main groove 20 is defined as the intersection point between the extension of the groove wall 20e of the circumferential main groove 20 and a virtual line extending in the tire width direction from the upper end of the circumferential bottom upper part 25.

[0076] This pneumatic tire 1 satisfies the relationship 0.2 ≤ W4 / W3, thereby preventing foreign objects such as stones from entering the groove bottom 20b of the circumferential main groove 20 with the circumferential bottom upper part 25, improving stone drilling resistance, and increasing the rigidity of the center block 301 to improve wear resistance. Furthermore, this pneumatic tire 1 utilizes the groove bottom 20b of the circumferential main groove 20 to secure groove volume, obtain shear force in the snow, and maintain snow traction performance. In this pneumatic tire 1, it is preferable to satisfy the relationship 0.2 ≤ W4 / W3 ≤ 0.6 in order to obtain the above effects.

[0077] Furthermore, in the pneumatic tire 1 of the embodiment, as shown in Figures 5 and 6, it includes a circumferential bottom upper portion 25 that protrudes from a part of the groove bottom 20b of the circumferential main groove 20 and is connected to the groove wall 20e of the circumferential main groove 20, and the groove depth D3 of the circumferential main groove 20 and the depth D4 of the circumferential bottom upper portion 25 satisfy the relationship 0.2 ≤ D4 / D3 ≤ 0.7.

[0078] Here, the depth D4 of the circumferential bottom upper portion 25 is the dimension from the opening end 20a of the circumferential main groove 20 to the upper end of the circumferential bottom upper portion 25, as shown in Figure 6.

[0079] This pneumatic tire 1 satisfies the relationship 0.5 ≤ D4 / D3 ≤ 0.7, thereby preventing foreign objects such as stones from entering the groove bottom 20b of the circumferential main groove 20 through the circumferential bottom upper part 25, improving resistance to stone drilling, and increasing the rigidity of the center block 301 to improve wear resistance. Moreover, this pneumatic tire 1 ensures groove volume and obtains shear force in the snow to maintain snow traction performance.

[0080] Furthermore, in the pneumatic tire 1 of the embodiment, as shown in Figures 5 and 6, it includes a circumferential bottom upper portion 25 that protrudes from a part of the groove bottom 20b of the circumferential main groove 20 and is connected to the groove wall 20e of the circumferential main groove 20. The circumferential main groove 20 is formed by bending at the portion where the center lug groove 50 opens and meandering in the tire width direction, and the circumferential bottom upper portion 25 is positioned by switching from one side to the other of the groove wall 20e of the circumferential main groove 20, with the bending portion as the starting point.

[0081] With this pneumatic tire 1, the circumferential main groove 20 is formed in a meandering manner in the tire width direction, thereby obtaining an edge component and improving snow traction performance. Furthermore, with this pneumatic tire 1, the circumferential main groove 20 is bent at the point where the center lug groove 50 opens, and the circumferential bottom upper part 25 is positioned by switching from one side to the other of the groove wall 20e of the circumferential main groove 20, using the bent part as a base point. This ensures a balanced arrangement of the circumferential bottom upper part 25, preventing the intrusion of foreign objects such as stones and maintaining stone drilling resistance, while also ensuring drainage of the circumferential main groove 20 and maintaining snow traction performance.

[0082] Furthermore, in the pneumatic tire 1 of the embodiment, as shown in Figure 7, four circumferential main grooves 20 are arranged in a row in the tire width direction, and between each circumferential main groove 20, both ends of the center lug groove 50 open into the circumferential main groove 20, thereby dividing the center block 301. When the portion of any center lug groove 50 that opens into the circumferential main groove 20 is projected in the tire width direction as shown by the dashed line L, the openings of the center lug grooves 50 that divide adjacent center blocks 301 in the tire width direction with respect to the circumferential main groove 20 overlap each other.

[0083] With this pneumatic tire 1, the openings of the center lug grooves 50 into the circumferential main grooves 20 can be evenly distributed, balancing snow traction performance, wear resistance, and stone drilling resistance. Furthermore, when projected in the tire width direction, the configuration in which the openings of the center lug grooves 50 that demarcate adjacent center blocks 301 in the tire width direction with respect to the circumferential main grooves 20 overlap can be achieved even if there is only one circumferential main groove 20.

[0084] Furthermore, in the pneumatic tire 1 of the embodiment, as shown in Figure 7, there are at least three center lug grooves 50 that demarcate adjacent rows of center blocks 301 in the circumferential direction of the tire within the contact surface R.

[0085] This pneumatic tire 1 improves snow traction performance by obtaining an edge component by ensuring a sufficient number of center lug grooves 50 within the contact surface R. Furthermore, a configuration in which at least three center lug grooves 50 demarcate adjacent rows of center blocks 301 in the circumferential direction of the tire within the contact surface R can be achieved even if there is only one circumferential main groove 20.

[0086] By the way, in this embodiment, as described above, a pneumatic tire 1 was described as an example of a tire. This pneumatic tire 1 can be filled with air, an inert gas such as nitrogen, or other gases. However, the tread pattern configuration of the pneumatic tire 1 described in this embodiment can be arbitrarily applied to other tires within the scope of what is obvious to those skilled in the art. Other tires include, for example, airless tires and solid tires. [Examples]

[0087] Figures 9 to 12 are charts showing the results of performance tests of the pneumatic tire according to the embodiment. Below, we will describe the performance evaluation tests conducted on the conventional and comparative examples of pneumatic tires and the pneumatic tire according to the embodiment. The performance evaluation tests included tests for wear resistance, snow traction performance, and stone drilling resistance. The test tires were sized 245 / 70R19.5, mounted on a specified rim (19.5 × 6.75), and filled to a specified internal pressure (850 kPa).

[0088] The wear resistance performance evaluation test is conducted by measuring the mileage traveled by a heavy-duty vehicle (low-floor 4-axle (2·2-D·D)) equipped with the test tire, from new to the end of wear (when the wear indicator appears on the tread surface). This evaluation is performed using an index evaluation with the conventional example as the baseline (100), and a higher value is preferable.

[0089] Snow traction performance evaluation tests are conducted using a heavy-duty vehicle (low-floor 4-axle (2·2-D·D)) equipped with test tires, under test conditions compliant with UN R117-04 (UN Regulation No. 117 Revision 4), on a snow-covered test course. The distance required to accelerate from the specified initial speed to the terminal speed is measured, and the acceleration is calculated. This evaluation is performed using an index evaluation with the conventional example as the baseline (100), and a higher value is preferable.

[0090] The stone drilling resistance evaluation test involves using a heavy-duty vehicle (low-floor 4-axle (2·2-D·D)) equipped with test tires. The number of stones reaching the bottom of the groove is measured and compared after 10 hours of off-road (unpaved road) driving followed by 2 hours of on-road (paved road) driving. This evaluation is performed using an index that is the reciprocal of the previous example as the baseline (100), with a higher value indicating a better result.

[0091] In conventional pneumatic tires, as shown in Figures 1 and 2, the center section block is demarcated by a single circumferential groove and a center lug groove, but the center section block is not arranged in a staggered pattern and does not have a bottom upper section in the width direction.

[0092] In the comparative example, the pneumatic tire has the configuration shown in Figures 1 and 2, in which the center section block is divided by a single circumferential groove and a center section lug groove, and the center section blocks are arranged in a staggered pattern, but it does not have a bottom upper section in the width direction.

[0093] The pneumatic tire of the embodiment has the configuration shown in Figures 1 and 2. In Embodiment 1, the center section block is divided by a single circumferential groove and a center section lug groove. The center section block is arranged in a staggered pattern and has a widthwise bottom section, with the sum of the widthwise bottom section sections being longer than the center section lug groove.

[0094] As shown in the test results, the pneumatic tire of the example demonstrates improved wear resistance and ice / snow performance (ice performance and snow traction performance) compared to the conventional example and each comparative example.

[0095] This disclosure includes the following inventions: [Invention 1] In the tread portion, there is at least one circumferential main groove extending along the tire circumferential direction, and a plurality of lug grooves extending along the tire width direction, opening into the circumferential main groove in the tire circumferential direction, and arranged in a staggered pattern through the circumferential main groove, Blocks are partitioned by the circumferential main groove and the lug groove, and are arranged in a staggered pattern via the circumferential main groove, A portion of the bottom of the lug groove protrudes from a part of the groove bottom and is connected to the groove wall in the width direction, Includes, In one of the lug grooves, the total length of the upper part of the widthwise bottom along the extending direction of the lug groove is longer than the length of one open end of the groove width of the lug groove. tire. [Invention 2] The groove width W1 of the lug groove and the width W2 of the upper part of the bottom in the width direction satisfy the relationship 0.2 ≤ W2 / W1. The tire described in Invention 1. [Invention 3] The groove depth D1 of the lug groove and the depth D2 of the upper part of the bottom in the width direction satisfy the relationship 0.5 ≤ D2 / D1 ≤ 0.9. A tire according to invention 1 or 2. [Invention 4] The lug groove has two bends along its extension, and the angle of inclination of the open end forming the groove width with respect to the tire width direction is such that the angle between the bends is greater than the angle from the bend to the end in the extension direction. A tire according to any one of inventions 1 to 3. [Invention 5] The aforementioned lug groove has two bends along its extension. The upper part of the bottom in the width direction is arranged in conjunction with both groove walls of the lug groove between the bent portions. A tire according to any one of inventions 1 to 4. [Invention 6] The circumferential main groove includes a portion of the groove bottom that protrudes from a part of the groove bottom and is connected to the groove wall of the circumferential main groove, With respect to the portion where the lug groove opens into the circumferential main groove, When projected in the extending direction of the lug groove, the circumferential bottom portion and the widthwise bottom portion overlap, and the wall of the block facing the opening of the lug groove is formed to protrude toward the opening of the lug groove via the circumferential main groove. A tire according to any one of inventions 1 to 5. [Invention 7] The circumferential main groove includes a portion of the groove bottom that protrudes from a part of the groove bottom and is connected to the groove wall of the circumferential main groove, The groove width W3 of the circumferential main groove and the width W4 of the circumferential bottom portion satisfy the relationship 0.2 ≤ W4 / W3. A tire according to any one of inventions 1 to 6. [Invention 8] The circumferential main groove includes a portion of the groove bottom that protrudes from a part of the groove bottom and is connected to the groove wall of the circumferential main groove, The groove depth D3 of the circumferential main groove and the depth D4 of the circumferential bottom portion satisfy the relationship 0.5 ≤ D4 / D3 ≤ 0.7. A tire according to any one of inventions 1 to 7. [Invention 9] The circumferential main groove includes a portion of the groove bottom that protrudes from a part of the groove bottom and is connected to the groove wall of the circumferential main groove, The circumferential main groove is formed by bending at the portion where the lug groove opens and meandering in the tire width direction, and at the bent portion, the upper part of the circumferential bottom is positioned so that it is on the other side of the groove wall of the circumferential main groove. A tire according to any one of inventions 1 to 8. [Invention 10] The aforementioned circumferential main grooves are arranged in a row of four in the tire width direction, and between each of the circumferential main grooves, both ends of the lug grooves open into the circumferential main grooves, thereby dividing the block. When the portion of any lug groove that opens into the circumferential main groove is projected in the tire width direction, the openings of the lug grooves that demarcate adjacent blocks in the tire width direction with respect to the circumferential main groove overlap each other. A tire as described in any one of inventions 1 to 9. [Invention 11] Within the contact surface, there are at least three lug grooves that demarcate each row of adjacent blocks in the circumferential direction of the tire. A tire according to any one of inventions 1 to 10. [Explanation of Symbols]

[0096] 1. Pneumatic tire (tire) 20 Circumferential main groove 25 Upper circumferential bottom 301 Center Block (Block) 50 Center lug groove (lug groove) 50F bent part 55 Bottom top in width direction

Claims

1. In the tread portion, there is at least one circumferential main groove extending along the tire circumferential direction, and a plurality of lug grooves extending along the tire width direction, opening into the circumferential main groove in the tire circumferential direction, and arranged in a staggered pattern through the circumferential main groove, Blocks are partitioned by the circumferential main groove and the lug groove, and are arranged in a staggered pattern via the circumferential main groove, A portion of the bottom of the lug groove protrudes from a part of the groove bottom and is connected to the groove wall in the width direction, Includes, In one of the lug grooves, the total length of the upper part of the widthwise bottom along the extending direction of the lug groove is longer than the length of one of the opening ends of the groove width of the lug groove. tire.

2. The groove width W1 of the lug groove and the width W2 of the upper part of the bottom in the width direction satisfy the relationship 0.2 ≤ W2 / W1. The tire according to claim 1.

3. The groove depth D1 of the lug groove and the depth D2 of the upper part of the bottom in the width direction satisfy the relationship 0.5 ≤ D2 / D1 ≤ 0.

9. The tire according to claim 1.

4. The lug groove has two bends along its extension, and the angle of inclination of the open end forming the groove width with respect to the tire width direction is such that the angle between the bends is greater than the angle from the bend to the end in the extension direction. The tire according to claim 1.

5. The aforementioned lug groove has two bends along its extension. The upper part of the bottom in the width direction is arranged in conjunction with both groove walls of the lug groove between the bent portions. The tire according to claim 1.

6. The circumferential main groove includes a portion of the groove bottom that protrudes from a part of the groove bottom and is connected to the groove wall of the circumferential main groove, With respect to the portion where the lug groove opens into the circumferential main groove, When projected in the extending direction of the lug groove, the circumferential bottom portion and the widthwise bottom portion overlap, and the wall of the block facing the opening of the lug groove is formed to protrude toward the opening of the lug groove via the circumferential main groove. The tire according to claim 1.

7. The circumferential main groove includes a portion of the groove bottom that protrudes from a part of the groove bottom and is connected to the groove wall of the circumferential main groove, The groove width W3 of the circumferential main groove and the width W4 of the circumferential bottom portion satisfy the relationship 0.2 ≤ W4 / W3. The tire according to claim 1.

8. The circumferential main groove includes a portion of the groove bottom that protrudes from a part of the groove bottom and is connected to the groove wall of the circumferential main groove, The groove depth D3 of the circumferential main groove and the depth D4 of the circumferential bottom portion satisfy the relationship 0.5 ≤ D4 / D3 ≤ 0.

7. The tire according to claim 1.

9. The circumferential main groove includes a portion of the groove bottom that protrudes from a part of the groove bottom and is connected to the groove wall of the circumferential main groove, The circumferential main groove is formed by bending at the portion where the lug groove opens and meandering in the tire width direction, and at the bent portion, the upper part of the circumferential bottom is positioned so that it is on the other side of the groove wall of the circumferential main groove. The tire according to claim 1.

10. The aforementioned circumferential main grooves are arranged in a row of four in the tire width direction, and between each of the aforementioned circumferential main grooves, both ends of the lug grooves open into the circumferential main grooves, thereby dividing the block. When the portion of any lug groove that opens into the circumferential main groove is projected in the tire width direction, the openings of the lug grooves that demarcate adjacent blocks in the tire width direction with respect to the circumferential main groove overlap each other. The tire according to claim 1.

11. Within the contact surface, there are at least three lug grooves that demarcate each row of adjacent blocks in the circumferential direction of the tire. The tire according to claim 1.

Images