tire

Abstract

To achieve a balance between center wear resistance and wet performance. [Solution] The tire comprises a center circumferential groove 21 having alternating first inclined grooves 21Sa and second inclined grooves 21Sb arranged on the tire equatorial plane CL, a shoulder circumferential groove 22 having alternating third inclined grooves 22Sa and fourth inclined grooves 22Sb on the outer side of the center circumferential groove 21 in the tire width direction, a center land portion 31 between each circumferential groove 21, 22, and a center lug groove 50 connecting the tops of the center circumferential groove 21 and the shoulder circumferential groove 22. The center circumferential groove 21 has a first inclined groove 21Sa with an angle θ1 of 5° to 24° in absolute value relative to the tire circumferential direction, and a second inclined groove 21Sb with an angle θ2 of 20° to 40° in absolute value relative to the tire circumferential direction. Each center lug groove 50 is composed of an inner groove 50i with a groove width W1 on the center circumferential groove 21 side and an outer groove 50o with a groove width W2 on the shoulder circumferential groove 22 side, with the groove width W1 being narrower than the groove width W2.

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 resistance to uneven wear in a pneumatic tire for heavy loads.

[0003] Also conventionally, for example, Patent Document 2 discloses a technique for improving both ice performance and snow performance in a pneumatic tire for ice and snow roads.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Regarding the problem of improving wet performance, there is a technique of providing circumferential grooves in the pattern center portion to improve drainage. However, since the tread volume in the center portion with relatively high ground pressure decreases, the center portion tends to wear more easily than the shoulder portion.

[0006] An object of this invention is to provide a tire capable of achieving both center wear resistance performance and wet 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, a center circumferential groove formed in a zigzag shape in the tire width direction, having alternate first inclined grooves and second inclined grooves that extend along the tire circumferential direction and are inclined with respect to the tire circumferential direction, and positioned on the tire equatorial plane; in the tread portion, a shoulder circumferential groove formed in a zigzag shape in the tire width direction, having alternate third inclined grooves and fourth inclined grooves that extend along the tire circumferential direction and are inclined with respect to the tire circumferential direction, and positioned on the outside of the center circumferential groove in the tire width direction; two rows of center land portions partitioned between each of the circumferential grooves; and in each of the center land portions... The tire comprises a plurality of center lug grooves arranged in the circumferential direction of the tire, connecting the opposing zigzag-shaped tops of the center circumferential groove and the shoulder circumferential groove, and a plurality of center blocks partitioned by each of the circumferential grooves and each of the center lug grooves, wherein the center circumferential groove has an angle θ1 of 5[°] to 24[°] in absolute value with respect to the tire circumferential direction for the first inclined groove, and an angle θ2 of 20[°] to 40[°] in absolute value with respect to the tire circumferential direction for the second inclined groove, and each of the center lug grooves is composed of an inner groove with a groove width W1 that opens into the center circumferential groove and an outer groove with a groove width W2 that opens into the shoulder circumferential groove, with the groove width W1 being narrower than the groove width W2. [Effects of the Invention]

[0008] This invention makes it possible to achieve both center wear resistance and wet performance. [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 plan view of the tread portion of another example of a pneumatic tire according to the embodiment. [Figure 6] Figure 6 is a chart showing the results of a performance test of a pneumatic tire according to the embodiment. [Figure 7] Figure 7 is a chart showing the results of a performance test of a pneumatic tire according to the embodiment. [Figure 8] Figure 8 is a chart showing the results of a performance test of a pneumatic tire according to the 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. [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] Figure 1 is a meridional cross-sectional view of the pneumatic tire 1 of the embodiment. This embodiment describes a tire for light trucks, which are classified as vehicles such as light cargo vehicles and light trucks, and is a radial tire for light trucks that is applied as a studless tire.

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

[0014] A pair of bead cores 11 are formed by winding one or more bead wires made of steel in a ring-like and multi-layered manner, and are embedded in the bead portions on both sides in the tire width direction to constitute the core of the bead portion.

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

[0016] The carcass layer 13 has a single-layer structure composed of one 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 two carcass plies 131 and 132. The carcass layer 13 is bridged in a toroidal shape between both 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. Further, the carcass layer 13 is configured by covering a plurality of carcass cords made of an organic fiber material or steel with a coating rubber and performing rolling processing. 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 formed by laminating a plurality of belt plies 141 to 144, and is wound around the outer circumference of the carcass layer 13. In the pneumatic tire 1 of the embodiment, the belt plies 141 to 144 are composed of cross belts 141, 142, a belt cover 143, and a pair of belt edge covers 144, 144. The cross belts 141, 142 are formed by coating a plurality of belt cords made of steel or organic fiber material with cover rubber and rolling them. The cross belts 141, 142 have a so-called cross ply structure in which the belt cords have mutually different signed cord angles with respect to the tire circumferential direction and are laminated so as to cross each other. The cross belts 141, 142 are laminated and arranged on the outer side in the tire radial direction of the carcass layer 13. The belt cover 143 and the pair of belt edge covers 144 are formed by coating a belt cover cord made of steel or organic fiber material with cover rubber. The belt cover 143 and the pair of belt edge covers 144 have a cord angle in which the belt cover cord extends along the tire circumferential direction. The belt cover 143 and the belt edge covers 144 are formed, for example, by winding a strip material formed by coating one or a plurality of belt cover cords with cover rubber around the outer peripheral surface of the cross belts 141, 142 a plurality of times in a spiral manner in the tire circumferential direction. The belt cover 143 is arranged to cover the entire area of the cross belts 141, 142. The pair of belt edge covers 144 are arranged to cover the edge portions on both sides in the tire width direction of the cross belts 141, 142 from the outer side in the tire radial direction.

[0018] The tread rubber 15 is arranged on the outer side in the tire radial direction of the carcass layer 13 and the belt layer 14, and constitutes the tread portion of the pneumatic tire 1. The tread rubber 15 forms a tread surface 15A (also referred to as a running surface) on the outer peripheral surface that contacts the road surface during running in the tread portion. The end portion on the outer side in the tire width direction of the tread surface 15A becomes the grounding end T (see FIG. 2).

[0019] The pair of sidewall rubbers 16 are respectively arranged on the outer sides in the tire width direction of the carcass layer 13, and constitute the sidewall portions on both sides in the tire width direction of the pneumatic tire 1.

[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 minimum 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 circumferential grooves 20, circumferential fine grooves 40, lug grooves 50, 60, and sipes 70, 80 on the tread surface 15A of the tread portion.

[0026] The circumferential grooves 20 are provided extending along the circumferential direction of the tire. Three circumferential grooves 20 are provided side by side in the tire width direction. The circumferential grooves 20 have a groove width of 6 mm to 15 mm. The circumferential grooves 20 also have a groove depth of 9 mm to 21.5 mm. The circumferential grooves 20 include one center circumferential groove 21 on the tire equatorial plane CL and two shoulder circumferential grooves 22 provided on the tire width side of each center circumferential groove 21. Each circumferential groove 20 may be defined as a groove that has a wear indicator display obligation as specified by JATMA.

[0027] The center circumferential groove 21 extends along the tire circumferential direction and is bent in the tire width direction to form a zigzag shape. Specifically, as shown in Figure 2, the center circumferential groove 21 has a zigzag shape because the bent portion 21F reverses its bending direction in the tire circumferential direction, and between it it alternately has a linear first inclined groove 21Sa and a second inclined groove 21Sb inclined with respect to the tire circumferential direction in the tire circumferential direction.

[0028] As shown in Figure 3, the first inclined groove 21Sa is formed to be longer than the second inclined groove 21Sb. The first inclined groove 21Sa is positioned in the opposite inclination direction to the second inclined groove 21Sb, with the acute angle θ1 of the opening edge (groove wall) in the groove width direction that opens to the tread surface 15A relative to the tire circumferential direction being between 5° and 24° in absolute value.

[0029] As shown in Figure 3, the second inclined groove 21Sb is formed to be shorter than the first inclined groove 21Sa. The second inclined groove 21Sb is positioned in the opposite inclination direction to the first inclined groove 21Sa, with the acute angle θ2 of the opening edge (groove wall) in the groove width direction that opens to the tread surface 15A relative to the tire circumferential direction being between 20° and 40° in absolute value.

[0030] Each shoulder circumferential groove 22 extends along the tire circumferential direction and is bent in the tire width direction to form a zigzag shape. Specifically, as shown in Figure 2, each shoulder circumferential groove 22 has a zigzag shape because the bent portion 22F reverses its bending direction in the tire circumferential direction, and between them it alternately has a linear third inclined groove 22Sa and a fourth inclined groove 22Sb inclined with respect to the tire circumferential direction.

[0031] As shown in Figure 3, the third inclined groove 22Sa is formed to be longer than the fourth inclined groove 22Sb. The third inclined groove 22Sa is positioned in the opposite inclination direction to the fourth inclined groove 22Sb, with the acute angle θ3 of the opening edge (groove wall) in the groove width direction that opens to the tread surface 15A relative to the tire circumferential direction being between 5° and 24° in absolute value.

[0032] As shown in Figure 3, the fourth inclined groove 22Sb is formed to be shorter than the third inclined groove 22Sa. The fourth inclined groove 22Sb is positioned in the opposite inclination direction to the third inclined groove 22Sa, with the acute angle θ4 of the opening edge (groove wall) in the groove width direction that opens to the tread surface 15A having an absolute value of 20[°] or more and 40[°] or less.

[0033] Furthermore, the center circumferential groove 21 and each shoulder circumferential groove 22 are arranged facing each other so that their respective bent portions 21F and 22F are adjacent to each other in the tire width direction with the same bending direction.

[0034] Each circumferential groove 20 defines a land area 30 in the tire width direction. The land area 30 includes two rows of center land areas 31 defined between the center circumferential groove 21 and each shoulder circumferential groove 22, and two rows of shoulder land areas 32 defined between each shoulder circumferential groove 22 and each contact end T. Furthermore, the area on the inner side in the tire width direction between each shoulder circumferential groove 22 is defined as the center section, which includes each center land area 31 and the center circumferential groove 21, and the area on the outer side in the tire width direction of each shoulder circumferential groove 22 is defined as the shoulder section, which includes the shoulder land area 32.

[0035] As shown in Figure 2, the circumferential groove 40 extends along the circumferential direction of the tire and divides the shoulder land portion 32 in the tire width direction. The circumferential groove 40 is a groove with a narrower groove width than the circumferential groove 20. The circumferential groove 40 has a groove width of 1 [mm] to 6 [mm]. In addition, the circumferential groove 40 has a groove depth of 3 [mm] to 13 [mm].

[0036] The circumferential groove 40 extends along the tire's circumferential direction and bends in the tire's width direction, forming a zigzag shape. Although not explicitly shown in the figure, the circumferential groove 40 also includes forms that are formed linearly along the tire's circumferential direction. Specifically, as shown in Figure 2, the circumferential groove 40 has a zigzag shape because the bent portion 40F reverses its bending direction in the tire's circumferential direction, and the section between them is a straight portion 40S inclined with respect to the tire's circumferential direction. Therefore, the circumferential groove 40 has a narrower groove width than the circumferential groove 20 and extends along the tire's circumferential direction and bends in the tire's width direction, forming a zigzag shape. The circumferential groove 40 has an acute angle of inclination with respect to the tire's circumferential direction of the opening edge (groove wall) in the groove width direction that opens to the tread surface 15A of the straight portion 40S, which is between 10° and 25° in absolute value. Furthermore, the circumferential grooves 40 are arranged so that their bent portions 40F and 22F are positioned opposite each other in the tire width direction, either approaching or separating in the tire width direction, with adjacent shoulder circumferential grooves 22 in the tire width direction.

[0037] The lug groove 50, also called the center lug groove, extends linearly or in an arc along the tire width direction in each center land portion 31, with each end opening into the center circumferential groove 21 and the shoulder circumferential groove 22. Multiple lug grooves are arranged in a row along the tire circumferential direction, dividing each center land portion 31 into multiple center blocks 31A in the tire circumferential direction. Although not explicitly shown in the figure, at least two shoulder circumferential grooves 22 may be arranged on both outer sides of the center circumferential groove 21 in the tire width direction. In this case, the center land portion 31 and the center blocks 31A are divided between the circumferential grooves 21 and 22, and the center portion is the area in the tire width direction between the outermost shoulder circumferential grooves 22 in the tire width direction.

[0038] The center lug groove 50 opens at the nearest bends 21F and 22F of the center circumferential groove 21 and the shoulder circumferential groove 22 that bend toward each other, connecting the tops of the zigzag shape of the center circumferential groove 21 and the shoulder circumferential groove 22 (the nearest bends 21F and 22F). The center lug groove 50 does not open at the bends 21F and 22F of the center circumferential groove 21 and the shoulder circumferential groove 22 that bend toward each other. Accordingly, as shown in Figure 3, the center block 31A, which is partitioned by two adjacent center lug grooves 50 in the circumferential direction of the tire, is arranged on the tread surface 15A with an edge shape enclosed by the first side B1 at the angle θ1 formed by the opening edge of the first inclined groove 21Sa of the center circumferential groove 21 and the second side B2 at the angle θ2 formed by the opening edge of the second inclined groove 21Sb, the third side B3 at the angle θ3 formed by the opening edge of the third inclined groove 22Sa of the shoulder circumferential groove 22 and the fourth side B4 at the angle θ4 formed by the opening edge of the fourth inclined groove 22Sb, and the fifth side B5, sixth side B6, and seventh side B7 formed by the opening edges of the center lug grooves 50.

[0039] The center lug groove 50 is formed by the inner groove 50i on the inner side in the tire width direction opening into the center circumferential groove 21 and the outer groove 50o on the outer side in the tire width direction opening into the shoulder circumferential groove 22 being in communication. The inner groove 50i has a groove width W1 (see FIG. 3) of 1.0 [mm] or more and 6.0 [mm] or less. The inner groove 50i has a groove depth of 5.0 [mm] or more and 20.0 [mm] or less. Further, the outer groove 50o has a groove width W2 (see FIG. 3) of 4.5 [mm] or more and 10.0 [mm] or less. The outer groove 50o has a groove depth of 5.5 [mm] or more and 21.5 [mm] or less. The inner groove 50i and the outer groove 50o have a variable region where the groove widths gradually change in the middle of each other, and the middle (center) of the variable region serves as the boundary between the inner groove 50i and the outer groove 50o. Therefore, the groove width of the inner groove 50i ranges from 1.2×W1 including a part of the variable region, and the groove width of the outer groove 50o ranges from 0.8×W2 including a part of the variable region. The center lug groove 50 satisfies the relationship W1 < W2 between the groove width W1 of the inner groove 50i and the groove width W2 of the outer groove 50o. And, in the part where the inner groove 50i and the outer groove 50o communicate, one of both opening edges in the groove width direction opening to the tread surface 15A is continuous with a straight line or an arc, and the other is continuous through an inclination that gradually varies the groove width. In this center lug groove 50, one of both opening edges in the groove width direction that is continuous with a straight line or an arc forms the fifth side B5 of the center block 31A, and the other of both opening edges of the inner groove 50i that is continuous through the inclination forms the sixth side B6 of the center block 31A, and the other of both opening edges of the outer groove 50o that is continuous through the inclination forms the seventh side B7 of the center block 31A. Here, the fifth side B5 has an acute inclination angle with respect to the tire circumferential direction of the straight line connecting both ends with an absolute value of 5 [°] or more and 25 [°] or less. Also, the sixth side B6 has an acute inclination angle with respect to the tire circumferential direction of the straight line connecting both ends within the range of the groove width W1 with an absolute value of 45 [°] or more and 80 [°] or less. Also, the seventh side B7 has an acute inclination angle with respect to the tire circumferential direction of the straight line connecting both ends within the range of the groove width W2 with an absolute value of 45 [°] or more and 80 [°] or less.

[0040] In addition, as shown in FIG. 4, the center lug groove 50 has a bottom upper portion 50u that protrudes from the groove bottom toward the tread surface 15A on the side opening to the center circumferential groove 21. And as shown in FIG. 4, the center lug groove 50 has a groove depth h1 on the center circumferential groove 21 side having the bottom upper portion 50u and a groove depth h2 on the shoulder circumferential groove 22 side not having the bottom upper portion 50u, and these groove depths h1 and h2 satisfy the relationship of h1 < h2.

[0041] The lug groove 60, also referred to as a shoulder lug groove, extends linearly or curvedly along the tire width direction at each shoulder land portion 32 as shown in FIG. 2, is provided in a plurality in the tire circumferential direction, and divides each shoulder land portion 32 into a plurality in the tire circumferential direction.

[0042] The shoulder lug groove 60 includes a shoulder inner lug groove 61 and a shoulder outer lug groove 62.

[0043] The inner shoulder lug groove 61 is located inward in the tire width direction, separated by the circumferential narrow groove 40, within the shoulder lug groove 60 provided in each shoulder land portion 32. The inner shoulder lug groove 61 has a groove width of 2 mm to 10 mm. The inner shoulder lug groove 61 also has a groove depth of 3 mm to 15 mm. The inner shoulder lug groove 61 is provided with one end opening into the circumferential narrow groove 40 and the other end opening into the shoulder circumferential groove 22. The inner shoulder lug groove 61 opens at the position of a bend 40F that faces inward in the tire width direction of the circumferential narrow groove 40, and has one bend 40F that faces outward in the tire width direction between adjacent inner shoulder lug grooves 40 in the tire circumferential direction. The circumferential narrow groove 40 has two straight sections 40S that extend in different inclination directions separated by one bend 40F between adjacent inner shoulder lug grooves 61 in the tire circumferential direction. Furthermore, the inner shoulder lug groove 61 opens at the position of a bent portion 22F at the other end of the shoulder circumferential groove 22 that faces outward in the tire width direction, and has one bent portion 22F that faces inward in the tire width direction between adjacent inner shoulder lug grooves 61 in the tire circumferential direction. The shoulder circumferential groove 22 has a third inclined groove 22Sa and a fourth inclined groove 22Sb that extend in different inclination directions with respect to the one bent portion 22F between adjacent inner shoulder lug grooves 61 in the tire circumferential direction. In addition, the center lug groove 50 provided on the center land portion 31 with respect to the shoulder circumferential groove 22 has openings that do not face each other in the tire width direction but are offset in the tire circumferential direction. Furthermore, each inner shoulder lug groove 61 provided on each shoulder land portion 32 has an inclination angle of 0[°]±5[°] with respect to the tire width direction of the opening edge (groove wall) in the groove width direction that opens to the tread surface 15A and is arranged approximately parallel to the tire width direction.

[0044] The outer shoulder lug groove 62 is located on the outer side in the tire width direction, separated by the circumferential narrow groove 40, within the shoulder lug groove 60 provided on each shoulder land portion 32. The outer shoulder lug groove 62 has a groove width of 2 mm to 10 mm. The outer shoulder lug groove 62 also has a groove depth of 3 mm to 15 mm. The outer shoulder lug groove 62 is provided with one end opening into the circumferential narrow groove 40 and the other end opening into the contact edge T. The outer shoulder lug groove 62 opens at the position of the bend 40F of the circumferential narrow groove 40 that faces outward in the tire width direction, and has one bend 40F that faces inward in the tire width direction between adjacent grooves in the tire circumferential direction. The inner shoulder lug groove 61 and the outer shoulder lug groove 62 open alternately in the tire circumferential direction at the position of the bend 40F of the circumferential narrow groove 40, and are arranged in a staggered pattern that does not overlap with each other in the projection in the tire width direction. Furthermore, at the other end of the shoulder outer lug groove 62 that opens to the contact end T, a chamfered portion 62a is formed in the groove depth direction from the tread surface 15A such that the groove width widens outward in the tire width direction. Each shoulder outer lug groove 62 provided on each shoulder land portion 32 is arranged substantially parallel to the tire width direction of the opening edge (groove wall) in the groove width direction that opens to the tread surface 15A at an angle of 0[°]±5[°].

[0045] The inner shoulder lug groove 61, along with the circumferential narrow groove 40 and the circumferential shoulder groove 22, divides the inner side of each shoulder land portion 32 in the tire width direction into multiple inner shoulder blocks 32A arranged in the tire circumferential direction. The outer shoulder lug groove 62, along with the circumferential narrow groove 40 and the contact end T, divides the outer side of each shoulder land portion 32 in the tire width direction into multiple outer shoulder blocks 32B arranged in the tire circumferential direction. The inner shoulder blocks 32A and outer shoulder blocks 32B are arranged in a staggered pattern in the tire width direction.

[0046] The inner shoulder block 32A has edges formed along each groove 22, 40, and 61 by the third inclined groove 22Sa and the fourth inclined groove 22Sb of the circumferential shoulder groove 22, the one bent portion 40F and two straight portions 40S of the circumferential narrow groove 40, and the straight or curved shape of the inner shoulder lug groove 61. The outer shoulder block 32B has edges formed along each groove 40, 62 and the ground contact end T by the one bent portion 40F and two straight portions 40S of the circumferential narrow groove 40, the straight shape of the ground contact end T, and the straight or curved shape and chamfered portion 62a of the outer shoulder lug groove 62.

[0047] As shown in Figure 2, the sipes 70 are provided on each center block 31A of each center land portion 31. The sipes 70 are formed in a zigzag shape on the tread surface 15A. The sipes 70 are formed in a straight line in the depth direction (tire diameter direction). The sipes 70 may be formed in a zigzag shape in the depth direction. The sipes 70 include open sipes 71 and closed sipes 72. The open sipes 71 are provided on each center block 31A, extending along the tire width direction, and at least one end opens into the center circumferential groove 21 or the shoulder circumferential groove 22. The open sipes 71 have a groove width of less than 1.0 [mm]. The open sipes 71 also have a depth of 3 [mm] or more and 12 [mm] or less. The closed sipes 72 are terminated at both ends within the block on each center block 31A. The closed sipes 72 have a groove width of less than 1.0 [mm]. Furthermore, the closed sipe 72 has a depth of 3 mm to 12 mm. The open sipe 71 and closed sipe 72 are arranged in each center block 31A such that the straight line connecting both ends extends approximately parallel to the tire width direction within a range of 0° ± 3°.

[0048] As shown in Figure 2, the sipes 80 are provided on each inner shoulder block 32A and each outer shoulder block 32B of each shoulder land portion 32. The sipes 80 are formed in a zigzag shape on the tread surface 15A. The sipes 80 are formed in a straight line in the depth direction (tire diameter direction). The sipes 80 may be formed in a zigzag shape in the depth direction. The sipes 80 include closed sipes 81 and open sipes 82. The closed sipes 81 have both ends terminated within the block in each inner shoulder block 32A and each outer shoulder block 32B. The closed sipes 81 have a groove width of less than 1.0 [mm]. The closed sipes 81 also have a depth of 3 [mm] or more and 12 [mm] or less. The open sipes 82 are provided in each outer shoulder block 32A, extending along the tire width direction, and at least one end opens into the circumferential narrow groove 40 or the shoulder circumferential groove 22. The open sipe 82 has a groove width of less than 1.0 mm. The open sipe 82 also has a depth of 3 mm or more and 12 mm or less. The closed sipe 81 and closed sipe 82 are arranged such that the straight line connecting both ends of each shoulder inner block 32A and each shoulder outer block 32B extends approximately parallel to the tire width direction within a range of 0° ± 3°.

[0049] Figure 5 is a plan view of the tread portion of another example of a pneumatic tire according to the embodiment. The pneumatic tire 1 shown in Figure 5 differs slightly from the pneumatic tire 1 shown in Figure 2 in the shape of the shoulder land portion 32, but has a similar configuration and produces similar effects. Here, the pneumatic tire 1 shown in Figure 5 has a larger groove width in the shoulder lug grooves 60 (61, 62) compared to the pneumatic tire 1 shown in Figure 2. Also, the pneumatic tire 1 shown in Figure 5 does not have open sipes in the outer shoulder block 32A compared to the pneumatic tire 1 shown in Figure 2, and only closed sipes 81 are arranged therein.

[0050] The pneumatic tire 1 of the embodiment is characterized by having a center circumferential groove 21 in the tread portion that extends along the circumferential direction of the tire and has alternating first inclined grooves 21Sa and second inclined grooves 21Sb that are inclined with respect to the circumferential direction of the tire, forming a zigzag shape in the tire width direction and positioned on the tire equatorial plane CL; shoulder circumferential grooves 22 in the tread portion that extends along the circumferential direction of the tire and has alternating third inclined grooves 22Sa and fourth inclined grooves 22Sb that are inclined with respect to the circumferential direction of the tire, forming a zigzag shape in the tire width direction and positioned on the outside of the center circumferential groove 21 in the tire width direction; two rows of center land portions 31 partitioned between the circumferential grooves 21 and 22; and in each center land portion 31, The tire comprises a center lug groove 50 arranged in a row in the circumferential direction of the tire, connecting the opposing zigzag-shaped peaks of the center circumferential groove 21 and the shoulder circumferential groove 22, and a plurality of center blocks 31A partitioned by each circumferential groove 21, 22 and each center lug groove 50. As shown in Figure 3, the center circumferential groove 21 has a first inclined groove 21Sa with an angle θ1 of 5[°] to 24[°] in absolute value with respect to the tire circumferential direction, and a second inclined groove 21Sb with an angle θ2 of 20[°] to 40[°] in absolute value with respect to the tire circumferential direction. Each center lug groove 50 consists of an inner groove 50i with a groove width W1 that opens into the center circumferential groove 21 and an outer groove 50o with a groove width W2 that opens into the shoulder circumferential groove 22, with the groove width W1 being narrower than the groove width W2.

[0051] This pneumatic tire 1 distributes the contact pressure near the circumferential grooves 21 and 22 by employing zigzag-shaped circumferential grooves 21 and 22. Furthermore, this pneumatic tire 1 improves drainage performance and wet performance by providing a small angle between the first inclined groove 21Sa and the second inclined groove 21Sb, which form the center block 31A, and the tire circumferential direction. Furthermore, this pneumatic tire 1 improves drainage performance and wet performance by connecting the center lug groove 50 to the top of the zigzag shape of the circumferential grooves 21 and 22. Moreover, this pneumatic tire 1 achieves both improved rigidity of the center block 31A and improved drainage performance to the circumferential grooves 21 and 22 by having both narrow and wide groove sections in the center lug groove 50. As a result, this pneumatic tire 1 can achieve both center wear resistance and wet performance by increasing the rigidity of the center block 31A while improving drainage to the circumferential grooves 21 and 22. Furthermore, this pneumatic tire 1 can improve uneven wear between the center and shoulder sections by improving its resistance to center wear.

[0052] Furthermore, in the pneumatic tire 1 of the embodiment, as shown in Figure 3, each shoulder circumferential groove 22 has an angle θ3 of 5[°] to 24[°] in absolute value with respect to the tire circumferential direction for the third inclined groove 22Sa, and an angle θ4 of 20[°] to 40[°] in absolute value with respect to the tire circumferential direction for the fourth inclined groove 22Sb.

[0053] According to this pneumatic tire 1, the third inclined groove 22Sa and fourth inclined groove 22Sb forming the center block 31A also have portions with small angles to the tire circumferential direction, thereby improving drainage performance and wet performance.

[0054] Furthermore, in the pneumatic tire 1 of the embodiment, as shown in Figure 3, the center block 31A satisfies the relationship 0.2 ≤ L2 / L1 ≤ 0.5 between the extended length L1 of the first side B1 formed by the first inclined groove 21Sa in the center circumferential groove 21 and the extended length L2 of the second side B2 formed by the second inclined groove 21Sb, and the relationship 0.5 ≤ L4 / L3 ≤ 0.9 between the extended length L3 of the third side B3 formed by the third inclined groove 22Sa in the shoulder circumferential groove 22 and the extended length L4 of the fourth side B4 formed by the fourth inclined groove 22Sb.

[0055] This pneumatic tire 1 improves drainage performance and wet performance by providing long sections in the zigzag shape of the center circumferential groove 21 and the shoulder circumferential groove 22. However, if the short section becomes extremely short, the bending of the zigzag shape will become too sharp, affecting drainage performance, so it should be kept within a suitable range. In order to significantly obtain the above effect, it is preferable that the relationships 0.3 ≤ L2 / L1 ≤ 0.5 and 0.5 ≤ L4 / L3 ≤ 0.7 are set for this pneumatic tire 1.

[0056] Furthermore, in the pneumatic tire 1 of the embodiment, as shown in Figure 3, the center lug groove 50 satisfies the relationship 0.1 ≤ W1 / W2 ≤ 0.6 between the groove width W1 of the inner groove 50i and the groove width W2 of the outer groove 50o.

[0057] When W1 / W2 is less than 0.1, the inner groove 50i tends to become relatively narrow, reducing drainage performance. When it exceeds 0.6, the outer groove 50o tends to become relatively wide, reducing the rigidity of the center block 31A and accelerating center wear. Therefore, with this pneumatic tire 1, it is possible to achieve both center wear resistance and wet performance by increasing the rigidity of the center block 31A while improving drainage to the circumferential grooves 21 and 22.

[0058] Furthermore, in the pneumatic tire 1 of the embodiment, as shown in Figure 3, the angle θ5 between the first side B1 formed by the first inclined groove 21Sa of the center circumferential groove 21 and the fifth side B5 formed by one of the opening edges of the center lug groove 50 is in the range of 90[°] to 150[°].

[0059] With this pneumatic tire 1, by setting the angle θ5 between the center circumferential groove 21 and the center lug groove 50 to 90° or more, drainage performance is enhanced and wet performance is improved. Furthermore, by setting the angle θ5 to 120° or more, drainage performance can be further enhanced and wet performance can be improved even more. In addition, by setting the angle θ5 to 150° or less, the angle θ1 of the first inclined groove 21Sa of the center circumferential groove 21 with respect to the tire circumferential direction becomes excessive, which increases the curvature with the second inclined groove 21Sb and suppresses the tendency for it to affect the drainage performance of the center circumferential groove 21.

[0060] Furthermore, in the pneumatic tire 1 of the embodiment, as shown in Figure 3, the angle θ6 between the third side B3 formed by the third inclined groove 22Sa of the shoulder circumferential groove 22 and the seventh side B7 formed by the other side of the opening edge of the center lug groove 50 of the center block 31A is in the range of 90[°] to 150[°].

[0061] With this pneumatic tire 1, by setting the angle θ6 between the shoulder circumferential groove 22 and the center lug groove 50 to 90° or more, drainage performance is enhanced and wet performance is improved. Furthermore, by setting the angle θ6 to 120° or more, drainage performance can be further enhanced and wet performance can be further improved. In addition, by setting the angle θ6 to 150° or less, the angle θ3 of the third inclined groove 22Sa of the shoulder circumferential groove 22 with respect to the tire circumferential direction becomes excessive, increasing the curvature with the fourth inclined groove 22Sb and suppressing the tendency for this to affect the drainage performance of the shoulder circumferential groove 22.

[0062] Furthermore, in the pneumatic tire 1 of the embodiment, as shown in Figure 3, the extended length L6 of the inner groove 50i and the extended length L7 of the outer groove 50o satisfy the relationship 0.5 ≤ L6 / L7 ≤ 1.5.

[0063] With this pneumatic tire 1, by making the lengths of the inner groove 50i and outer groove 50o, which are adjacent to each other and have different groove widths, equal, the rigidity of the center block 31A is increased, and the tendency for center wear to progress can be suppressed. Furthermore, in order to make the rigidity of adjacent center blocks 31A in the tire circumferential direction with respect to the center lug groove 50 uniform, it is desirable to maintain the angle difference between the fifth side B5 and the sixth side B6 that form the groove width W1 of the inner groove 50i to be approximately parallel with a value of 0[°]±5[°], and to maintain the angle difference between the fifth side B5 and the seventh side B7 that form the groove width W2 of the outer groove 50o to be approximately parallel with a value of 0[°]±5[°].

[0064] Furthermore, in the pneumatic tire 1 of the embodiment, as shown in Figure 4, the center lug groove 50 satisfies the relationship 0.3 ≤ h1 / h2 ≤ 0.9 between the groove depth h1 on the center circumferential groove 21 side and the groove depth h2 on the shoulder circumferential groove 22 side.

[0065] According to this pneumatic tire 1, the rigidity of the center block 31A is increased by making the groove depth h1 on the center circumferential groove 21 side of the center lug groove 50 shallower, and the drainage performance is improved by making the groove depth h2 on the shoulder circumferential groove 22 side deeper. The groove depth h1 is measured within the groove width W1 range of the inner groove 50i, and the groove depth h2 is measured within the groove width W2 range of the outer groove 50o.

[0066] Furthermore, in the pneumatic tire 1 of the embodiment, as shown in Figure 4, the center lug groove 50 has a bottom upper part 50u at the bottom of the groove on the inner side in the tire width direction, and the length L8 of the center lug groove 50 in the extending direction of the bottom upper part 50u and the extending length L6 of the inner groove 50i on the inner side in the tire width direction satisfy the relationship 0.8 ≤ L6 / L8 ≤ 1.2.

[0067] According to this pneumatic tire 1, by aligning the position of the point of change in groove depth from the bottom upper part 50u on the center circumferential groove 21 side with the position of the point of change in groove width from the groove width W1 of the inner groove 50i on the center circumferential groove 21 side, it contributes to increasing the rigidity of the center block 31A and improving the center wear resistance performance. The bottom upper part 50u is defined as a section with a groove depth h1 that is 60% or less of the groove depth h2 at the measurement point of the groove width W2 of the outer groove 50o.

[0068] Furthermore, in the pneumatic tire 1 of this embodiment, as shown in Figure 3, the center block 31A is formed by a continuous straight line or a continuous arc on the fifth side B5 formed by the center lug groove 50.

[0069] According to this pneumatic tire 1, the drainage performance is improved by forming one of the fifth sides B5 of the opening edge of the center lug groove 50 continuously without a corner.

[0070] Furthermore, in the pneumatic tire 1 of the embodiment, as shown in Figure 2, the amplitude T1 of the zigzag shape of the center circumferential groove 21 in the tire width direction satisfies the relationship 0.01 ≤ T1 / TDW ≤ 0.05 with respect to the tire unfolded width TDW.

[0071] With this pneumatic tire 1, by appropriately defining the amplitude T1 in the tire width direction of the zigzag shape of the center circumferential groove 21, it is possible to obtain the effect of distributing the contact pressure due to the amplitude T1 while suppressing the impact on wet performance due to excessive amplitude T1.

[0072] Furthermore, in the pneumatic tire 1 of the embodiment, as shown in Figure 2, the maximum dimension TB of the center block 31A in the tire width direction satisfies the relationship 0.25 ≤ TB / TDW ≤ 0.35 with respect to the tire unfolded width TDW.

[0073] With this pneumatic tire 1, by appropriately defining the maximum dimension TB in the tire width direction of the center block 31A, it is possible to improve the rigidity of the center block 31A by increasing the maximum dimension TB, while suppressing the impact on wet performance due to a reduction in groove volume caused by an excessive maximum dimension TB.

[0074] 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]

[0075] Figures 6 to 10 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 wet performance and resistance to uneven center wear. The test tire was a 205 / 85R16 tire size, mounted on a specified rim, filled to the specified internal pressure, and mounted on a test vehicle (2-D: light truck).

[0076] The wet performance evaluation test is conducted under test conditions compliant with UN R117-04 (UN Regulation No. 117 Revision 4). A test vehicle equipped with the test tire measures the grip index (ratio of the test tire's performance to the reference tire's performance) on a wet surface with a water depth of 1 mm. Based on these measurement results, an index evaluation is performed using the conventional example as the baseline (100). A higher numerical value is preferable.

[0077] The evaluation test for resistance to uneven wear at the center is conducted on a test vehicle equipped with the test tire on a dry road surface test course, and the ratio of wear between the center and shoulder sections when the center section is 50% worn is calculated. This evaluation is performed using an index evaluation with the conventional example as the baseline (100), and a higher value is preferable.

[0078] Conventional pneumatic tires have three circumferential grooves forming four land sections, and a center lug groove connecting to each circumferential groove forms the center block. However, each circumferential groove is straight, and the groove width of the center lug groove is outside the specified range.

[0079] In the comparative example pneumatic tire, three circumferential grooves form four land sections, and a center lug groove connects to each circumferential groove, forming a center block, with each circumferential groove arranged in a zigzag pattern. In comparative example 1, the center lug groove connects to the straight section of the circumferential groove, and the θ1 and θ2 of the center circumferential groove deviate from the specifications. In comparative example 2, the center lug groove connects to the apex of the circumferential groove, but the groove width of the center lug groove and the θ1 and θ2 of the center circumferential groove deviate from the specifications.

[0080] In the embodiment, the pneumatic tire has four land sections formed by three circumferential grooves, a center block formed by a center lug groove connected to each circumferential groove, the circumferential grooves arranged in a zigzag shape, the center lug groove connected to the apex of the circumferential grooves, and the groove width of the center lug groove and the θ1 and θ2 of the center circumferential groove are within the specified range.

[0081] As shown in the test results, the pneumatic tire of the example shows improved wet performance and resistance to uneven wear at the center compared to the conventional example and each comparative example.

[0082] This disclosure includes the following inventions: [Invention 1] In the tread portion, a center circumferential groove is formed in a zigzag shape in the tire width direction, having alternating first and second inclined grooves that extend along the tire circumferential direction and are inclined with respect to the tire circumferential direction, and is positioned on the tire equatorial plane. In the tread portion, shoulder circumferential grooves are formed in a zigzag shape in the tire width direction, having alternating third and fourth inclined grooves that extend along the tire circumferential direction and are inclined with respect to the tire circumferential direction, and are respectively located on the outside of the center circumferential groove in the tire width direction. Two rows of central land areas are separated between each of the aforementioned circumferential grooves, In each of the aforementioned center land portions, a plurality of center lug grooves are arranged in the circumferential direction of the tire, connecting the opposing zigzag-shaped peaks of the center circumferential groove and the shoulder circumferential groove, A plurality of center blocks, each partitioned by the circumferential groove and each of the center lug grooves, Equipped with, The center circumferential groove has the first inclined groove having an angle θ1 of 5° to 24° in absolute terms with respect to the tire circumferential direction, and the second inclined groove having an angle θ2 of 20° to 40° in absolute terms with respect to the tire circumferential direction. Each of the center lug grooves is composed of an inner groove with a groove width W1 that opens into the center circumferential groove and an outer groove with a groove width W2 that opens into the shoulder circumferential groove, wherein the groove width W1 is narrower than the groove width W2. tire. [Invention 2] Each of the shoulder circumferential grooves has the third inclined groove having an angle θ3 of 5° to 24° in absolute terms with respect to the tire circumferential direction, and the fourth inclined groove having an angle θ4 of 20° to 40° in absolute terms with respect to the tire circumferential direction. The tire described in Invention 1. [Invention 3] The aforementioned center block is The extended length L1 of the first side formed by the first inclined groove and the extended length L2 of the second side formed by the second inclined groove satisfy the relationship 0.2 ≤ L2 / L1 ≤ 0.5. The extended length L3 of the third side formed by the third inclined groove and the extended length L4 of the fourth side formed by the fourth inclined groove satisfy the relationship 0.5 ≤ L4 / L3 ≤ 0.9. A tire according to invention 1 or 2. [Invention 4] Each of the center lug grooves satisfies the relationship 0.1 ≤ W1 / W2 ≤ 0.6 between the groove width W1 of the inner groove and the groove width W2 of the outer groove. A tire according to any one of inventions 1 to 3. [Invention 5] The aforementioned center block is The angle θ5 between the first side formed by the first inclined groove and the fifth side formed by one of the opening edges of the center lug groove is in the range of 90° to 150°. A tire according to any one of inventions 1 to 4. [Invention 6] The aforementioned center block is The angle θ6 between the third side formed by the third inclined groove and the seventh side formed by the other side of the opening edge of the center lug groove is in the range of 90° to 150°. A tire according to any one of inventions 1 to 5. [Invention 7] The extended length L6 of the inner groove and the extended length L7 of the outer groove satisfy the relationship 0.5 ≤ L6 / L7 ≤ 1.5. A tire according to any one of inventions 1 to 6. [Invention 8] The center lug groove satisfies the relationship 0.3 ≤ h1 / h2 ≤ 0.9 between the groove depth h1 on the center circumferential groove side and the groove depth h2 on the shoulder circumferential groove side. A tire according to any one of inventions 1 to 7. [Invention 9] The aforementioned center lug groove has a bottom upper portion at the groove bottom on the inner side in the tire width direction. The length L8 in the extending direction of the center lug groove on the bottom upper part and the extending length L6 of the inner groove satisfy the relationship 0.8 ≤ L6 / L8 ≤ 1.2. A tire according to any one of inventions 1 to 8. [Invention 10] The aforementioned center block is The fifth side of the center lug groove is formed by a continuous straight line or a continuous circular arc. A tire according to any one of inventions 1 to 9. [Invention 11] The amplitude T1 of the zigzag shape of the center circumferential groove in the tire width direction satisfies the relationship 0.01 ≤ T1 / TDW ≤ 0.05 with respect to the tire unfolded width TDW. A tire according to any one of inventions 1 to 10. [Invention 12] The maximum dimension TB in the tire width direction of the center block satisfies the relationship 0.25 ≤ TB / TDW ≤ 0.35 with respect to the tire unfolded width TDW. A tire according to any one of inventions 1 to 11. [Explanation of symbols]

[0083] 1. Pneumatic tire (tire) 15A Tread surface 21 Center circumferential groove (circumferential groove) 21Sa First inclined groove 21Sb Second inclined groove 22. Shoulder circumferential groove (circumferential groove) 22Sa Third inclined groove 22Sb Fourth inclined groove 31 Center Track and Field Club 31A Center Block 50 Center lug groove 50i Inner groove 50° Outer groove 50u bottom top B1 First side B2 second side B3 Third side B4 Fourth side B5, fifth side B6 Sixth side B7 Seventh side T ground end

Claims

1. In the tread portion, a center circumferential groove is formed in a zigzag shape in the tire width direction, having alternating first and second inclined grooves that extend along the tire circumferential direction and are inclined with respect to the tire circumferential direction, and is positioned on the tire equatorial plane. In the tread portion, shoulder circumferential grooves are formed in a zigzag shape in the tire width direction, having alternating third and fourth inclined grooves that extend along the tire circumferential direction and are inclined with respect to the tire circumferential direction, and are respectively located on the outside of the center circumferential groove in the tire width direction. Two rows of central land areas are separated between each of the aforementioned circumferential grooves, In each of the aforementioned center land portions, a plurality of center lug grooves are arranged in the circumferential direction of the tire, connecting the opposing zigzag-shaped peaks of the center circumferential groove and the shoulder circumferential groove, A plurality of center blocks, each partitioned by the circumferential groove and each of the center lug grooves, Equipped with, The center circumferential groove has the first inclined groove having an angle θ1 of 5° to 24° in absolute terms with respect to the tire circumferential direction, and the second inclined groove having an angle θ2 of 20° to 40° in absolute terms with respect to the tire circumferential direction. Each of the center lug grooves is composed of an inner groove with a groove width W1 that opens into the center circumferential groove and an outer groove with a groove width W2 that opens into the shoulder circumferential groove, wherein the groove width W1 is narrower than the groove width W2. tire.

2. Each of the shoulder circumferential grooves has the third inclined groove having an angle θ3 of 5° to 24° in absolute terms with respect to the tire circumferential direction, and the fourth inclined groove having an angle θ4 of 20° to 40° in absolute terms with respect to the tire circumferential direction. The tire according to claim 1.

3. The aforementioned center block is The extended length L1 of the first side formed by the first inclined groove and the extended length L2 of the second side formed by the second inclined groove satisfy the relationship 0.2 ≤ L2 / L1 ≤ 0.

5. The extended length L3 of the third side formed by the third inclined groove and the extended length L4 of the fourth side formed by the fourth inclined groove satisfy the relationship 0.5 ≤ L4 / L3 ≤ 0.

9. The tire according to claim 1.

4. Each of the center lug grooves satisfies the relationship 0.1 ≤ W1 / W2 ≤ 0.6 between the groove width W1 of the inner groove and the groove width W2 of the outer groove. The tire according to claim 1.

5. The aforementioned center block is The angle θ5 between the first side formed by the first inclined groove and the fifth side formed by one of the opening edges of the center lug groove is in the range of 90° to 150°. The tire according to claim 1.

6. The aforementioned center block is The angle θ6 between the third side formed by the third inclined groove and the seventh side formed by the other side of the opening edge of the center lug groove is in the range of 90° to 150°. The tire according to claim 1.

7. The extended length L6 of the inner groove and the extended length L7 of the outer groove satisfy the relationship 0.5 ≤ L6 / L7 ≤ 1.

5. The tire according to claim 1.

8. The center lug groove satisfies the relationship 0.3 ≤ h1 / h2 ≤ 0.9 between the groove depth h1 on the center circumferential groove side and the groove depth h2 on the shoulder circumferential groove side. The tire according to claim 1.

9. The aforementioned center lug groove has a bottom upper portion at the groove bottom on the inner side in the tire width direction. The length L8 in the extending direction of the center lug groove on the bottom upper part and the extending length L6 of the inner groove satisfy the relationship 0.8 ≤ L6 / L8 ≤ 1.

2. The tire according to claim 1.

10. The aforementioned center block is The fifth side of the center lug groove is formed by a continuous straight line or a continuous circular arc. The tire according to claim 1.

11. The amplitude T1 of the zigzag shape of the center circumferential groove in the tire width direction satisfies the relationship 0.01 ≤ T1 / TDW ≤ 0.05 with respect to the tire unfolded width TDW. The tire according to claim 1.

12. The maximum dimension TB of the center block in the tire width direction satisfies the relationship 0.25 ≤ TB / TDW ≤ 0.35 with respect to the tire unfolded width TDW. The tire according to claim 1.

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