Tires

Abstract

Task To provide low rolling resistance performance and wet traction performance in a compatible manner. Solution: A tire (1) includes: in a tread surface (15A), of four circumferential grooves (20), a pair of circumferential main grooves (21) arranged on respective outermost sides in the tire width direction and defining a central portion (31) therebetween; of the circumferential grooves, a narrow circumferential groove (22) arranged in the central portion and formed with a groove width (WH) of 30% or less of a groove width (W1) of the circumferential main grooves; and in three land portions (31A, 31B) defined by the circumferential grooves in the central portion, lug grooves (41, 42), both ends of each communicating with the adjacent circumferential grooves, and dividing each of the land portions into a plurality of blocks (31Aa, 31Ba). The central portion is provided closer to a center in the tire width direction within a range of 45% or more of a development width (TW) of the tread surface.The blocks divided into the land section closer to the center in the tire width direction are longer in the tire circumferential direction. The blocks have ends in the tire circumferential direction that are offset in the tire circumferential direction in each of the land sections.

Description

Technical area

[0001] The invention relates to a tire. State of the art

[0002] For example, Patent Document 1 discloses a tire having a pair of shoulder main grooves extending in the tire circumferential direction, a pair of shoulder regions, and a single center region defined by the pair of shoulder main grooves, the center region including center lug grooves having one end portion open to the shoulder main grooves and the other end portion located in a ground contact surface of the center region, and center lug grooves having both end portions located in the ground contact surface of the center region. Literature listPatent literature

[0003] Patent document 1: JP 2022-057908 A Brief description of the inventionTechnical problem

[0004] For example, in order to increase block stiffness for low rolling resistance, a heavy-duty drive shaft tire adopted a pattern in which the main groove width of a central section was set to a narrow groove and block rows were concentrated in the central section. However, there are concerns that such a tire would reduce groove volume and deteriorate drainage performance, leading to a deterioration of the original wet traction performance of the block pattern.

[0005] An object of the invention is to provide a tire that can provide low rolling resistance performance and wet traction performance in a compatible manner. Solution to the problem

[0006] To achieve the above-described object, a tire according to one aspect of the present invention includes: in a tread surface, of at least four circumferential grooves extending in the tire circumferential direction, a pair of circumferential main grooves arranged at the outermost sides in the tire width direction and defining a central portion therebetween; of the four circumferential grooves, one or more narrow circumferential grooves arranged in the central portion and having a groove width of 30% or less of the groove width of the circumferential main grooves;and in at least three land portions defined by at least two of the circumferential grooves in the central portion, a plurality of lug grooves extending in the tire width direction, arranged in the tire circumferential direction, with both ends of each communicating with the circumferential grooves adjacent in the tire width direction, and dividing each of the land portions into a plurality of blocks. The central portion is provided closer to a center in the tire width direction within a range of 45% or more of a development width of the tread surface. The blocks divided in the land portion closer to the center in the tire width direction are formed longer in the tire circumferential direction. The blocks have ends in the tire circumferential direction that are staggered in the tire circumferential direction in each of the land portions. Advantageous effects of the invention

[0007] One aspect of the invention can provide low rolling resistance performance and wet traction performance in a compatible manner. Brief description of the drawings Fig. 1 is a meridian cross-sectional view of a pneumatic tire according to an embodiment. Fig. 2 is a plan view of a tread surface of the pneumatic tire according to the embodiment. Fig. 3 is a cross-sectional view taken along line AA of Fig. 2. Fig. 4 is a table showing results of performance tests of pneumatic tires according to the embodiment. Fig. 5 is a table showing results of performance tests of pneumatic tires according to embodiments. Description of embodiments

[0008] The embodiment according to the present invention will be described in detail below with reference to the drawings. However, the invention is not limited to this embodiment. Components of the embodiments include elements that are interchangeable while maintaining consistency with the invention, as well as obviously interchangeable elements. The various modified examples described in the embodiments can be combined as needed within the scope obvious to a person skilled in the art.

[0009] In the following description, the term "tire radial direction" refers to a direction perpendicular to the tire rotation axis (not illustrated), which is a rotation axis of a pneumatic tire 1. The term "tire radial direction inner side" refers to a side toward the tire rotation axis in the tire radial direction, and the term "tire radial direction outer side" refers to a side away from the tire rotation axis in the tire radial direction of the embodiment. The term "tire circumferential direction" refers to a circumferential direction with the tire rotation axis as the center axis.The term "tire width direction" refers to a direction parallel to the tire rotation axis, the term "tire width direction inner side" refers to a side toward the tire equatorial plane (tire equator line) CL in the tire width direction, and the term "tire width direction outer side" refers to an equatorial plane of the tire CL in the tire width direction. The term "tire equatorial plane CL" refers to a plane perpendicular to the tire rotation axis and passing through the tire width center of the pneumatic tire 1. The tire equatorial plane CL is aligned at a position in the tire width direction with the tire width center line, which corresponds to the tire width center position of the pneumatic tire 1. The "tire equator line" refers to a line in the tire circumferential direction of the pneumatic tire 1 that lies on the tire equatorial plane CL.The term “cross-section in the tire meridian direction (meridian cross-sectional view)” refers to a cross-section of the tire along a plane that includes the tire’s axis of rotation.

[0010] Fig. Figure 1 is a meridian cross section of a pneumatic tire 1 of the present embodiment, illustrating a cross section of a region on one side of the tire rotation axis in the tire radial direction. In the present embodiment, a heavy-duty radial pneumatic tire mounted on a heavy-duty vehicle such as a truck or bus will be described as an example. The pneumatic tire 1 of the present embodiment is particularly suitable for use as a tire mounted on a drive shaft of a heavy-duty vehicle.

[0011] The pneumatic tire 1 of the embodiment has a ring structure whose center is the tire rotation axis and includes, as shown in Fig. 1, 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.

[0012] The pair of bead cores 11 includes one or more bead wires made of steel and formed by multiple annular winding, is embedded in bead portions, and forms cores of bead portions on both sides in the tire width direction.

[0013] The pair of bead fillers 12 are each composed of a lower filler 121 and an upper filler 122. The pair of bead fillers 12 are arranged on an outer circumference in the tire radial direction of the pair of bead cores 11 and reinforce the bead portions.

[0014] The carcass layer 13 has a single-layer structure including one carcass ply or a multi-layer structure including a plurality of laminated carcass plies. The carcass layer 13 extends in a toroidal shape between both bead cores 11 and forms a support structure of the tire. Both end portions of the carcass layer 13 are folded toward the outer sides in the tire width direction and are fixed to wrap the bead cores 11 and the bead fillers 12.The carcass ply of the carcass layer 13 is formed by covering a plurality of carcass cords made of steel with coating rubber and performing a rolling process thereon, and has, as absolute values, a cord angle (defined as an inclination angle in a longitudinal direction of the carcass cord with respect to a tire circumferential direction) of 80 degrees or more and 90 degrees or less for radial tires and 30 degrees or more and 45 degrees or less for a bias tire.

[0015] The belt layer 14 is formed by laminating a plurality of belt plies 141 to 144, and is wound and arranged around an outer periphery of the carcass layer 13. The belt plies 141 to 144 include a high-angle belt 141, a pair of cross belts 142 and 143, and a belt cover 144. The high-angle belt 141 is formed by covering a plurality of steel belt cords with coating rubber and performing a rolling process thereon, and has, in absolute value, a cord angle (defined as an inclination angle in a longitudinal direction of the belt cord with respect to the tire circumferential direction) of 45 degrees or more and 70 degrees or less. The pair of cross belts 142 and 143 is manufactured by covering a plurality of belt cords made of steel with coating rubber and performing a rolling process thereon, and has a cord angle of 10 degrees or more and 55 degrees or less in absolute value.The pair of cross belts 142 and 143 have cord angles of opposite signs, and are layered by causing the belt cords to intersect in the longitudinal direction of the belt cords (a so-called cross-ply structure is formed). The belt cover 144 is formed by covering a plurality of belt cover cords made of steel or an organic fiber material with coating rubber and subjecting them to a rolling process, and has a cord angle of 10 degrees or more and 55 degrees or less in absolute value.

[0016] The tread rubber 15 is arranged on an outer circumference in the tire radial direction of the carcass layer 13 and the belt layer 14 and constitutes a tread portion of the pneumatic tire 1. In the tread portion, the tread rubber 15 forms a tread surface (tread contact surface) 15A on an outer peripheral surface, which comes into contact with a road contact surface during running.

[0017] The pair of sidewall rubbers 16 are each arranged on outer sides of the carcass layer 13 in the tire width direction and form sidewall portions on both sides in the tire width direction.

[0018] The pair of rim cushion rubbers 17 extend from an inner side in the tire radial direction of the respective bead cores 11 and the turned-up portions of the carcass layer 13 toward the outer side in the tire width direction and form rim fitting surfaces of the bead portions.

[0019] As in Fig. As illustrated in Fig. 2, the pneumatic tire 1 of the embodiment includes a tread pattern on the tread surface 15A. Here, each dimension in the tread pattern is measured in a state where the tire is not mounted on a rim and the width between a pair of bead portions is set to a certain rim width.

[0020] "Specified rim" refers to a "standard rim" defined by JATMA, a "design rim" defined by the Tire and Rim Association Inc. (TRA), or a "measurement rim" defined by the European Tire and Rim Technical Organization (ETRTO). The "specified internal pressure" refers to a "maximum inflation pressure" specified by JATMA, the maximum value in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified by TRA, or "INFLATION PRESSURES" specified by ETRTO. A specified load refers to a "maximum load capacity" specified by JATMA, the maximum value in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified by TRA, or a "LOAD CAPACITY" specified by ETRTO.

[0021] A groove width is measured as the maximum value of a distance between opposing groove walls of a groove opening portion on the tread contact surface in a state where the tire is not mounted on a rim and the width between the pair of bead portions is set to the specified rim width. In a configuration where the groove opening portion includes a notch portion or a chamfered portion, the groove width is measured by using as endpoints the intersection points of an extension line of a tread contact surface and the extension lines of the groove walls in a cross-sectional view parallel to the tire width direction and the tire radial direction.

[0022] A groove depth is measured as the maximum value of a distance from the tread contact surface to a groove bottom in the state where the tire is not mounted on a rim and the width between the pair of bead portions is set to the specified rim width. In a configuration where a groove bottom partially includes recessed / projected portions or a sipe, the groove depth is measured without the partial recessed / projected portions or the sipe.

[0023] The pneumatic tire 1 includes at least four circumferential grooves 20 on the tread surface 15A. The circumferential groove 20 extends in the tire circumferential direction and has an annular structure that extends continuously along the entire circumference of the tire. The pneumatic tire 1 has two main circumferential grooves 21 among the at least four circumferential grooves 20. The pneumatic tire 1 has at least one narrow circumferential groove 22 among at least four circumferential grooves 20.

[0024] The circumferential main grooves 21 are provided as a pair (two) on outermost sides in the tire width direction, with the tire equatorial plane CL interposed therebetween. The circumferential main groove 21 is defined as a groove in which a treadwear indicator, as required by JATMA, is provided at a groove bottom 21b.

[0025] As in the meridian cross-section of Fig. 3, the pair of circumferential main grooves 21 each includes, at the outermost sides in the tire width direction, a pair of first groove walls 21c, a pair of platform portions 21d, and a pair of second groove walls 21e between an opening portion 21a and a groove bottom 21e. The pair of first groove walls 21c extend from the tread surface 15A toward the groove bottom 21b side on both sides of the opening portion 21b in the tire width direction. The pair of platform portions 21d are connected to the groove bottom 21b side of each of the first groove walls 21c and form raised platforms on the outer side in the tire radial direction with respect to the groove bottom 21b along the tread surface 15A. The pair of second groove walls 21e is arranged closer to the groove center (the center of the circumferential main groove 21 in the tire width direction) than each of the first groove walls 21c and extends from each of the platform portions 21d to the groove bottom 21b.The circumferential main groove 21 is formed in a zigzag shape extending in the tire circumferential direction and meandering in the tire width direction. As shown in . Fig. 3, the circumferential main groove 21 has a groove width W1 of 10.0 mm or more and 20.0 mm or less at the opening portion 21a, a groove width W2 of 3.0 mm or more and 4.5 mm or less between the second groove walls 21e (distance between the platform portions 21d), a groove depth D1 of 13.5 mm or more and 23.5 mm or less from the tread surface 15A to the groove bottom 21b, and a groove depth D2 of 7.5 mm or more and 17.5 mm or less from the tread surface 15A to the platform portion 21d. As shown in Fig. 3, the circumferential main groove 21 is formed such that an angle θ1 of each of the first groove walls 21c widens from the groove bottom 21b side toward the opening portion 21a side toward the tread surface 15A, and is 10 degrees or more and 14 degrees or less with respect to a normal of a profile of the tread surface 15A at one end of the opening portion 21a in the tire width direction.

[0026] In the pneumatic tire 1, land portions arranged in three rows in the tire width direction and extending along the tire circumferential direction are formed by the pair of circumferential main grooves 21 on the tread surface 15A. Specifically, the pneumatic tire 1 includes a central portion 31 defined between the two circumferential main grooves 21 and shoulder portions 32 respectively defined on outer sides of the respective circumferential main grooves 21 in the tire width direction. The central portion 31 is arranged to enclose the equatorial plane of the tire CL. Specifically, as shown in Fig. 1, the central portion 31 is provided closer to a tire width direction center within a tire width direction range CW of 45% to 60% with respect to a development width TW of the tread surface 15A. The shoulder portions 32 are respectively arranged on the two outermost sides of the tread surface 15A in the tire width direction.

[0027] Here, the developed width TW is a developed dimension between the ground contact ends T on both sides of the tread surface 15A in the tire width direction. The ground contact end T is defined as a position of maximum width in the tire width direction of the contact surface between the pneumatic tire 1 and a flat plate when the pneumatic tire 1 is mounted on a predetermined rim, inflated to a predetermined internal pressure, placed vertically on the flat plate, and loaded with a load corresponding to a predetermined load. The tire width direction area CW of the central portion 31 is a developed dimension between the tire width-direction inner ends of the opening portion 21a of each of the circumferential main grooves 21 on the outermost sides in the tire width direction.

[0028] The two circumferential narrow grooves 22 are arranged adjacent to each other in the tire width direction, with the equatorial plane of the tire CL interposed at the central portion 31. The circumferential narrow groove 22 is formed linearly along the tire circumferential direction. In the embodiment, the circumferential narrow groove 22 has a groove width of 1.0 mm or more and 5.0 mm or less, and a groove depth of 10.0 mm or more and 23.5 mm or less. The circumferential narrow groove 22 has a narrow groove width WH relative to the circumferential main groove 21 and is formed to be 30% or less of the groove width W1 of the circumferential narrow groove 21 on the outer side in the tire width direction.

[0029] It should be noted that one or more narrow circumferential grooves 22 may be provided in the central portion 31. That is, the pneumatic tire 1 may have the circumferential main groove 21 in addition to the narrow circumferential groove 22 in the central portion 31 between the pair of circumferential main grooves 21 arranged on the outermost sides of the at least four circumferential grooves 20 in the tire width direction. Note that, although not illustrated in the drawings, the other circumferential main groove 21 in the central portion 31 has a linear shape along the tire circumferential direction and has a groove width of 5.0 mm or more and 20.0 mm or less, and a groove depth of 13.5 mm or more and 23.5 mm or less.

[0030] When the pneumatic tire 1 has four circumferential grooves 20, the central portion 31 includes two-row central land portions 31A, each defined between the circumferential main groove 21 and the circumferential narrow groove 22 and adjacent to each other in the tire width direction. When the pneumatic tire 1 includes four circumferential grooves 20, the central portion 31 includes a one-row central land portion 31B defined between the two narrow circumferential grooves 22 (or between the circumferential main groove 21 and the circumferential narrow groove 22) between the two-row central land portions 31A. The one-row central land portion 31B is located closest to the center in the tire width direction, including the tire equatorial plane CL.

[0031] It should be noted that when the number of circumferential grooves 20 exceeds four, the central portion 31 includes a plurality of rows of central land portions 31B defined by the other main circumferential grooves 21 and narrow circumferential grooves 22 between the central land portions 31B of two rows.

[0032] As in Fig. As illustrated in Fig. 2, the center land portion 31A is provided with center lug grooves 41. A plurality of the center lug grooves 41 extend in the tire width direction and are arranged in the tire circumferential direction, and their two ends 41a communicate with the circumferential main groove 21 outermost in the tire width direction and the circumferential narrow groove 22 (or circumferential main groove 21) adjacent to the circumferential main groove 21 in the tire width direction. Thus, the center lug grooves 41 configure the center land portion 31A as a center block row divided into a plurality of center blocks 31Aa. The center lug groove 41 is curved in a seamless S-shape in its extension direction. The center lug groove 41 communicates with a tire width-inward meandering position of the zigzag shape of the circumferential main groove 21 on the tire width-outermost side.The center lug groove 41 has a groove width of 1.5 mm or more and 9 mm or less, which is narrower than the main circumferential groove 21, and a groove depth of 13.5 mm or more and 23.5 mm or less.

[0033] The center lug groove 41 is provided inclined with respect to the tire width direction. Specifically, the center lug groove 41 is provided such that an angle θ of a straight line connecting the centers of the respective ends 41a with respect to the tire width direction is 20 degrees or more. All the center lug grooves 41 provided in a center land portion 31A are provided inclined in the same direction with respect to the tire width direction. As indicated by the arrow R in Fig. 2, for the pneumatic tire 1 of the embodiment, a rotation direction during forward travel of the vehicle is indicated in use. Specifically, the pneumatic tire 1 has an indicator (not shown) for indicating a rotation direction, for example, on a sidewall portion. All the center lug grooves 41 provided in all the center land portions 31A are provided to be inclined in the same direction so that the end 41a on the inner side in the tire width direction faces forward in the rotation direction, and the end 41a on the outer side in the tire width direction, which communicates with the circumferential main groove 21, comes into contact with the ground later.

[0034] As in Fig. As illustrated in Figure 2, the center land portion 31A is provided with center sipes 51. A plurality of the center sipes 51 extend in the tire width direction and are arranged in the tire circumferential direction, and their two ends 51a communicate with the circumferential main groove 21 outermost in the tire width direction and the circumferential narrow groove 22 (or circumferential main groove 21) adjacent to the circumferential main groove 21 in the tire width direction. The center sipes 51 are arranged alternately with respect to the center lug grooves 41 in the tire circumferential direction. Accordingly, the center sipe 51 is provided to divide the center block 31Aa defined by the center lug groove 41 into two parts in the tire circumferential direction. The center sipes 51 are provided substantially parallel to the direction in which the center lug grooves 41 extend.The center sipe 51 is connected to a tire width-outwardly meandering position of the zigzag shape of the circumferential main groove 21 on the outermost side in the tire width direction. The center sipe 51 has a groove width of 1 mm or less and a groove depth of 10.0 mm or more and 18.0 mm or less.

[0035] The center block 31Aa is formed so that a flat shape, viewed from the tread surface 15A, is a parallelogram shape. In the center block 31Aa, a notch portion 31Ab is formed at a corner portion where the end 41a of the center lug groove 41 communicates with the circumferential main groove 21 and the circumferential narrow groove 22. The notch portion 31Ab is formed at an acute angle portion of a diagonal position of the parallelogram shape of the center block 31Aa. The notch portion 31Ab is formed at a corner portion of the center block 31Aa that is first loaded in the rotational direction and at a corner portion of a diagonal position that finally yields.

[0036] As in Fig. As illustrated in FIG. 2, the central land portion 31B is provided with central lug grooves 42. A plurality of the central lug grooves 42 extend in the tire width direction and are arranged in the tire circumferential direction, and both ends 42a communicate with the circumferential narrow grooves 22 (or circumferential main grooves 21) adjacent in the tire width direction. Thus, the central lug grooves 42 configure the central land portion 31B as a central block row divided into a plurality of central blocks 31Ba. All the central lug grooves 42 provided in one central land portion 31B are formed to be curved in a gentle arc shape in their extension direction.All the central lug grooves 42 provided in all the central land portions 31B are provided to be curved in the same direction so that the center on the inner side in the tire width direction faces further forward in the rotational direction than each end 42a. The central lug groove 42 is provided at a position in the tire circumferential direction where one end 42a thereof in the tire width direction does not face the end 41a on the inner side in the tire width direction of the central lug groove 41 of the central lug portion 31A. The central lug groove 42 has a groove width of 1.5 mm or more and 9 mm or less, which is narrower than the circumferential main groove 21, and a groove depth of 13.5 mm or more and 23.5 mm or less.

[0037] The central lug groove 42 is formed with a notch portion 42b at the end 42a, which communicates with the narrow circumferential groove 22 (or main circumferential groove 21). In other words, the notch portion 42b is formed at a corner portion of the central block 31Ba, which has a rectangular shape. The notch portion 42b is formed at an acute-angled side of the central block 31Ba, where the central lug groove 42 is arcuately curved and communicates with the narrow circumferential groove 22 (or main circumferential groove 21). The notch portions 42b are formed at corner portions on both sides in the tire width direction where the central block 31Ba finally yields in the rotational direction.

[0038] As in Fig. As illustrated in FIG. 2, the central land portion 31B is provided with central sub-lug grooves 43. A plurality of the central sub-lug grooves 43 extend in the tire width direction and are arranged in the tire circumferential direction, and one end 43a communicates with the narrow circumferential groove 22 (or main circumferential groove 21) adjacent in the tire width direction, and the other end 43a terminates within the central land portion 31B. A central sub-lug groove 43 is provided in each central block 31Ba. The central sub-lug grooves 43 are arranged alternately with the central lug grooves 42 in the tire circumferential direction. The central sub-lug grooves 43 are arranged alternately in the tire width direction toward the tire circumferential direction with the central lug groove 42 interposed therebetween.The central sub-lug groove 43 is provided at a position in the tire circumferential direction where one end 43a thereof in the tire width direction faces the end 41a on the inner side in the tire width direction of the central lug groove 41 of the central land portion 31A. The central sub-lug groove 43 has a groove width of 1.5 mm or more and 9 mm or less, which is narrower than the circumferential main groove 21, and a groove depth of 13.5 mm or more and 23.5 mm or less.

[0039] As in Fig. As illustrated in Fig. 2, the central land portion 31B is provided with central sipes 52. A plurality of the central sipes 52 extend in the tire width direction and are arranged in the tire circumferential direction, and one end 52a communicates with the narrow circumferential groove 22 (or main circumferential groove 21) adjacent in the tire width direction, and the other end 52a terminates within the central land portion 31B and communicates with the other end 43a at which the central sub-lug groove 43 terminates. One central sipe 52 is provided in each central block 31Ba. The central sipes 52 are arranged alternately with the central lug grooves 42 in the tire width direction. The central sipes 52 are arranged alternately in the tire width direction toward the tire circumferential direction with the central lug groove 42 interposed therebetween.The central sipe 52 and the central sub-lug groove 43 communicate with each other and are provided substantially parallel to each other along the direction in which the central lug groove 42 extends. The central sipe 52 is provided at a position in the tire circumferential direction where one end 52a thereof in the tire width direction is opposite to the end 51a on the inner side in the tire width direction of the center sipe 51 of the center land portion 31A. The central sipe 52 has a groove width of 1 mm or less and a groove depth of 10.0 mm or more and 18.0 mm or less.

[0040] As in Fig. 2 and Fig. As illustrated in Figure 3, the shoulder portion 32 is provided with shoulder lug grooves 45. The shoulder lug grooves 45 extend in the tire width direction and are arranged at equal intervals in the tire circumferential direction, and one end 45a communicates with the circumferential main groove 21 on the outermost side in the tire width direction, and the other end 45a opens to the ground contact end T. Thus, the shoulder lug grooves 45 configure the shoulder portion 32 as a shoulder block row divided into a plurality of shoulder blocks 32a. All the shoulder lug grooves 45 provided in the shoulder portion 32 are curved in a gentle arc shape in their extension direction. The shoulder lug groove 45 is provided inclined with respect to the tire width direction. Specifically, all the shoulder lug grooves 45 provided in the shoulder portion 32 are inclined in the same direction as the center lug grooves 41.All shoulder lug grooves 45 provided in the shoulder portion 32 are provided so as to be inclined in the same direction, such that one end 45a on the inner side in the tire width direction points further forward in the rotational direction than the other end 45a on the outer side in the tire width direction. The shoulder lug groove 45 has a groove width of 7.0 mm or more and 15.0 mm or less, and a groove depth of 7.5 mm or more and 17.5 mm or less.

[0041] In the shoulder lug groove 45, the end 45a communicating with the main circumferential groove 21 is formed with a notch portion 45c. In other words, the notch portion 45c is formed in a rectangular shape at a corner portion of the shoulder block 32a. The notch portion 45c is formed on an acute-angled side of the shoulder block 32a where the shoulder lug groove 45 is arcuately curved and communicates with the main circumferential groove 21. The notch portion 45c is formed at a corner portion on an inner side in the tire width direction where the shoulder block 32a is first loaded in the rotational direction. The notch portion 45c is chamfered to reach the platform portion 21d of the main circumferential groove 21 on the outermost side in the tire width direction and to be inclined on the inner side in the tire radial direction.

[0042] The shoulder lug groove 45 is formed with a raised bottom portion 45b protruding outward from the groove bottom in the tire radial direction. In the raised bottom portion 45b, along the profile of the tread surface 15A where the shoulder lug groove 45 opens, a top portion 45ba protruding furthest from the groove bottom is provided. In the shoulder lug groove 45, a groove depth D3 to the top portion 45ba of the raised bottom portion 45b is 2.0 mm or more and 8.0 mm or less, which is smaller than the groove depth D1 from the tread surface 15A to the groove bottom 21b of the circumferential main groove 21 on the outermost side in the tire width direction and the groove depth D2 from the tread surface 15A to the platform portion 21d of the circumferential main groove 21 on the outermost side in the tire width direction. These groove depths D1, D2 and D3 satisfy the relationships 0.50 ≤ D2 / D1 ≤ 0.90 and 0.10 ≤ D3 / D1 ≤ 0.40.

[0043] The raised land portion 45b has an inclined surface 45bb inclined from the upper portion 45ba on the inner side in the tire radial direction toward the platform portion 21d of the circumferential main groove 21 on the inner side in the tire width direction. An angle θ2 of the inclined surface 45bb with respect to a normal of the profile of the tread surface 15A where the shoulder lug groove 45 opens is 20 degrees or more and 60 degrees or less. The inclined surface 45bb is seamlessly connected to the upper portion 45ba by an arc 45bc. The inclined surface 45bb is seamlessly connected to the platform portion 21d of the circumferential main groove 21 on the outermost side in the tire width direction by an arc 45bd.

[0044] The raised land portion 45b has an inclined surface 45be inclined from the inner side in the tire radial direction on one side toward the other end 45a of the shoulder lug groove 45 on the outer side in the tire width direction. An angle θ3 of the inclined surface 45bb with respect to the profile normal of the tread surface 15A where the shoulder lug groove 45 opens is 10 degrees or more and 30 degrees or less. The inclined surface 45be is seamlessly connected to the upper portion 45ba by an arc 45bf.

[0045] In the raised land portion 45b, a distance in the tire width direction between the normal of the profile of the tread surface 15A at which the shoulder lug groove 45 opens, at an intersection point of extension lines of the inclined surface 45bb and the top portion 45ba, and the normal of the profile of the tread surface 15A at which the shoulder lug groove 45 opens, at the intersection point of the extension lines of the inclined surface 45bb and the top portion 45ba is defined as a dimension WS2 in the tire width direction of the top portion 45ba.In the shoulder lug groove 45 having the raised bottom portion 45b, a distance in the tire width direction between the normal line of the profile of the tread surface 15A at an outermost end in the tire width direction of the opening portion 21a of the circumferential main groove 21 on the outermost side in the tire width direction and the normal line of the profile of the tread surface 15A at the ground contact end T is defined as the tire width direction dimension WS1. In this case, the tire width direction dimension WS1 of the shoulder lug groove 45 and the tire width direction dimension WS2 of the top portion 45ba satisfy the relationship 0.50≤WS2 / WS1≤0.90. Preferably, the tire width direction dimension WS1 of the shoulder lug groove 45 and the tire width direction dimension WS2 of the upper portion 45ba satisfy the relationship 0.60 ≤ WS2 / WS1 ≤ 0.80.

[0046] The pneumatic tire 1 according to the present embodiment includes, as features in the tread surface, at least four circumferential grooves 20 extending in the tire circumferential direction; a pair of circumferential main grooves 21 each disposed at the outermost sides in the tire width direction and defining the central portion 31 therebetween; of the four circumferential grooves 20, one or more narrow circumferential grooves 22 disposed in the central portion 31 and formed with a groove width WH of 30% or less of the groove width W1 of the circumferential main grooves 21; and in at least three land portions 31A, 31B defined by at least two of the circumferential grooves 20 in the central portion 31, a plurality of lug grooves 41, 42 extending in the tire width direction and arranged in the tire circumferential direction, both ends of each communicating with the circumferential grooves 20 adjacent in the tire width direction.and divides each of the land portions 31A, 31B into a plurality of blocks 31Aa, 31Ba. The central portion 31 is provided closer to a tire width-direction center within a range of the tire width-direction dimension CW of 45% or more of the development width TW of the tread surface 15A. The blocks 31Aa, 31Ba divided in the land portion 31B closer to the tire width-direction center are formed longer in the tire circumferential direction. The blocks 31Aa, 31Ba have ends in the tire circumferential direction that are staggered in the tire circumferential direction in each of the land portions 31A, 31B.

[0047] In the pneumatic tire 1, since the pair of circumferential main grooves 21 on the outermost sides in the tire width direction has a groove width larger than the circumferential main groove 21 of the central portion 31, the ground contact surface pressure of the central portion 31 becomes high, and the blocks 31Aa, 31Ba are arranged in the central portion 31 to suppress deformation of the entire tread surface 15A. As a result, the pneumatic tire 1 can provide improved low rolling resistance performance. Moreover, the pneumatic tire 1 can provide further improved low rolling resistance performance by making the block 31Ba longer in the tire circumferential direction closer to the center where the ground contact pressure is high.On the other hand, in the pneumatic tire 1, the lug grooves 41 open to the pair of circumferential main grooves 21 on the outermost sides in the tire width direction, and the blocks 31Aa, 31Ba sequentially come into contact with the ground intermittently, thereby ensuring an efficient drainage effect. This enables the pneumatic tire 1 to provide improved wet traction performance. In the pneumatic tire 1, the blocks 31Aa, 31Ba sequentially come into contact with the ground intermittently to prevent the blocks 31Aa, 31Ba from collapsing and deforming in the forward / backward direction. Therefore, it is possible to suppress deterioration of the low rolling resistance performance due to the arrangement of the lug grooves 41, 42. As a result, the pneumatic tire 1 according to the embodiment can provide low rolling resistance performance and wet traction performance in a compatible manner.

[0048] In the pneumatic tire 1 of the embodiment, in the central portion 31, a tire circumferential direction length L1 of the block 31Ba in the central land portion 31B closest to the center in the tire width direction and a tire circumferential direction length L2 of the block 31Aa in the center land portion 31A adjacent to the center land portion 31B in the tire width direction satisfy the relationship 1.2 ≤ L1 / L2 ≤ 1.9.

[0049] The pneumatic tire 1 can provide further improved low rolling resistance performance by increasing the tire circumferential direction length of the block 31Ba of the central land portion 31B. By not excessively increasing the tire circumferential direction length of the block 31Ba of the central land portion 31B, the pneumatic tire 1 can have the total number of lug grooves 42 in the entire tire circumferential direction while maintaining wet traction performance.

[0050] In the pneumatic tire 1 of the embodiment, in the central portion 31, with respect to the tire circumferential length L1 of the block 31Ba in the central land portion 31B closest to the center in the tire width direction, a misalignment amount D in the tire circumferential direction between an end of the central land portion 31B in the tire circumferential direction and an end of the block 31Aa in the central land portion 31A adjacent to the central land portion 31B in the tire width direction satisfies the relationship 0.1 ≤ D / L1 ≤ 0.5.

[0051] By arranging the blocks 31Aa, 31Ba offset from each other in the tire circumferential direction, the pneumatic tire 1 can prevent the adjacent blocks 31Aa, 31Ba from falling off simultaneously during rotation, thereby providing improved low rolling resistance performance.

[0052] In the pneumatic tire 1 of the embodiment, the groove width WH of the narrow circumferential groove 22 is 5 mm or less.

[0053] The pneumatic tire 1 increases rigidity by arranging the blocks 31Aa, 31Ba close to each other in the central portion 31, which has a high ground contact pressure, which is beneficial for improving low rolling resistance. In the pneumatic tire 1, the groove width WH of the circumferential narrow groove 22 is preferably 3 mm or less to make the effect more advantageous, but the groove width WH of the circumferential narrow groove 22 is preferably 1.5 mm or more to ensure drainage performance.

[0054] In the pneumatic tire 1 of the embodiment, the groove width WL of the center lug grooves 41 communicating with the pair of circumferential main grooves 21 arranged on the outermost sides in the tire width direction is 1.5 mm or more and 9 mm or less.

[0055] In the pneumatic tire 1, by defining the groove width WL of the center lug grooves 41, the rigidity of the center blocks 31Aa is maintained or the center blocks 31Aa are supported from each other, which is beneficial for improving low rolling resistance performance. To make the effects more advantageous, in the pneumatic tire 1, the groove width WL of the center lug groove 41 is preferably 1.5 mm or more and 7 mm or less.

[0056] In the pneumatic tire 1 of the embodiment, the center lug grooves 41 communicating with the pair of circumferential main grooves 21 arranged on the outermost sides in the tire width direction extend at an angle of 20 degrees or more with respect to the tire width direction.

[0057] By defining the angle at which the center lug groove 41 extends, the pneumatic tire 1 increases drainage to the circumferential main groove 21, which is beneficial for improving wet traction performance. In the pneumatic tire 1 of the embodiment, the end 41a of the center lug groove 41 that communicates with the circumferential main groove 21 is inclined to contact the ground later, thereby further improving drainage to the circumferential main groove 21, which is more beneficial for improving wet traction performance.

[0058] In the pneumatic tire 1 of the embodiment, the circumferential main groove 21 includes the pair of first groove walls 21c extending in a meridian cross-sectional shape from the tread surface 15A toward the groove bottom 21b side, the pair of platform portions 21d connected to the groove bottom 21b side of each of the first groove walls 21c and forming a platform along the tread surface 15A, and the pair of second groove walls 21c located closer to the groove center side than each of the first groove walls 21d and extending from each of the platform portions 21d toward the groove bottom 21b side.In the shoulder portions 32 defined on the outer sides in the tire width direction of the circumferential main grooves 21, a plurality of shoulder lug grooves 45 are provided, extending in the tire width direction, arranged in the tire circumferential direction, having an end 45a communicating with the circumferential main groove 21, and including the raised bottom portion 45b formed on the groove bottom. The raised bottom portion 45b of the shoulder lug groove 45 and the platform portion 21d of the circumferential main groove 21 are seamlessly connected by the arc 45bd.

[0059] By forming the groove shape of the circumferential main groove 21 on the outermost side in the tire width direction into the platform groove shape, in the pneumatic tire 1, the narrow second groove walls 21e on the groove bottom 21b side of the platform portions 21e tend to be closed when in contact with the ground. In addition, in the pneumatic tire 1, by seamlessly connecting the raised bottom portion 45b to the platform portion 21d, it is possible to eliminate a stepped space that may occur at a connecting portion between the circumferential main groove 21 outermost in the tire width direction and the shoulder lug groove 45. For this reason, the pneumatic tire 1 has such a shape that causes stones that may penetrate into the connecting portion between the circumferential main groove 21 and the shoulder lug groove 45 to not reach the groove bottom 21b of the circumferential main groove 21, thereby improving the stone ejection performance.In order to advantageously exhibit the above-described effects, it is preferable that the groove width W2 between the second groove walls 21e is 3.0 mm or more and 4.5 mm or less, and the radius of the arc 45bd is 2.0 mm or more and 15.0 mm or less in the pneumatic tire 1. Furthermore, by disposing the raised land portion 45b, sound is less likely to leak outward in the tire width direction, which is advantageous for reducing pass-by noise.

[0060] In the pneumatic tire 1 of the embodiment, the groove depth D1 of the circumferential main groove 21 on the outermost side in the tire width direction, the groove depth D2 up to the platform portion 21d and the groove depth D3 up to the raised bottom portion 45b of the shoulder lug groove 45 satisfy the relationships 0.50 ≤ D2 / D1 ≤ 0.90 and 0.10 ≤ D3 / D1 ≤ 0.40.

[0061] In the pneumatic tire 1, by defining the groove depth D2 of the platform portion 21d within an appropriate range, it is possible to achieve the effect of easily ejecting a picked-up stone without the stone reaching the groove bottom 21b of the circumferential main groove 21. Furthermore, by defining the groove depth D3 up to the raised bottom portion 45b within an appropriate range, the effect of suppressing the leakage of sound to the outside in the tire width direction becomes advantageous. To make these effects more advantageous, the pneumatic tire 1 preferably satisfies the relationships 0.60 ≤ D2 / D1 ≤ 0.70 and 0.25 ≤ D3 / D1 ≤ 0.35.

[0062] In the pneumatic tire 1 of the embodiment, the pair of first groove walls 21c of the circumferential main groove 21 on the outermost side in the tire width direction is shaped to widen toward the tread surface 15A.

[0063] In the pneumatic tire 1, by providing an angle to the pair of first groove walls 21c leading to the tread surface 15A, a difference in groove width is created between the tread surface 15A side and the platform portion 21d side, resulting in improved removability of the picked-up stone. In the pneumatic tire 1, since the groove volume of the circumferential main groove 21 decreases toward the groove bottom portion 21b, the effect of reducing pass-by noise is not impaired.

[0064] In the pneumatic tire 1 of the embodiment, the tire width direction dimension WS1 of the shoulder lug groove 45 and the tire width direction dimension WS2 of the upper portion 45ba of the raised land portion 45b satisfy the relationship 0.50 ≤ WS2 / WS1 ≤ 0.90.

[0065] In the pneumatic tire 1, the stone ejection performance of the shoulder lug groove 45 is improved by defining the tire width direction dimension WS2 of the raised land portion 45b within an appropriate range. Furthermore, in the pneumatic tire 1, by disposing the raised land portion 45b in the shoulder lug groove 45 of the shoulder portion 32 through which sound is likely to leak, the sound leakage is reduced and the groove volume is reduced to reduce pass-by noise. To make these effects more advantageous, the pneumatic tire 1 preferably satisfies the relationship 0.60 ≤ WS2 / WS1 ≤ 0.80.

[0066] In the pneumatic tire 1 of this embodiment, the raised land portion 45b on the inner side in the tire width direction includes the inclined surface (first inclined surface) 45bb inclined on the inner side in the tire radial direction from the upper portion 45ba toward the platform portion 21d of the circumferential main groove 21, and the inclined surface (second inclined surface) 45be inclined on the inner side in the tire radial direction from the upper portion 45ba toward the other end 45a of the shoulder lug groove 45. The inclined surface 45bb has an angle θ2 of 20 degrees or more and 60 degrees or less with respect to the profile normal of the tread surface 15A where the shoulder lug groove 45 opens, and the inclined surface 45be has an angle θ3 of 10 degrees or more and 30 degrees or less with respect to the profile normal of the tread surface 15A where the shoulder lug groove 45 opens.

[0067] In the pneumatic tire 1, by defining the angle θ2 of the inclined surface 45bb of the raised land portion 45b and the angle θ3 of the inclined surface 45be of the raised land portion 45b, which face the outer side in the tire width direction, at the connecting portion between the outermost circumferential main groove 21 in the tire width direction and the raised land portion 45b within an appropriate range, the picked-up stone is smoothly removed and the stone ejection performance is improved. Moreover, in the pneumatic tire 1, by setting the angle θ2 and the angle θ3 within the predetermined ranges, the effect of reducing pass-by noise is not impaired. In order to make these effects more advantageous, it is preferable that the angle θ2 be 40 degrees or more and 50 degrees or less, and that the angle θ3 be 15 degrees or more and 25 degrees or less, in the pneumatic tire 1.

[0068] In the pneumatic tire 1 of the embodiment, the shoulder lug grooves 45 extend arcuately in the tire width direction and are arranged at regular intervals in the tire circumferential direction. As a preferable range of regular intervals, the pitch in the tire circumferential direction is 65 mm or more and 75 mm or less.

[0069] By arranging the shoulder lug grooves 45 at equal intervals in the tire circumferential direction, the groove areas of the shoulder portions 32 of the pneumatic tire 1 are uniform, and the effect of reducing pass-by noise is maintained. Furthermore, the shoulder lug grooves 45 in the pneumatic tire 1 extend in a circular arc, allowing the trapped stone to be removed smoothly.

[0070] In the pneumatic tire 1 of the embodiment, in the shoulder blocks 32a in which the shoulder portion 32 is defined by the shoulder lug grooves 45, the notch portion 45c, which is chamfered to reach the platform portion 21d in the circumferential main groove 21 and inclined toward the inside in the tire radial direction, is formed at the acute angle portion where the shoulder lug groove 45 communicates with the circumferential main groove 21.

[0071] In the pneumatic tire 1, the generation of impact noise during driving is suppressed by chamfering the acute-angled portion of the shoulder block 32a. In the pneumatic tire 1, the groove width of the shoulder lug groove 45 opening to the tread surface 15A becomes wider due to the inclined chamfers, and the groove width becomes narrower toward the platform portion 21d. Therefore, this does not affect the stone ejection performance. To make the effects more advantageous, the pneumatic tire 1 preferably satisfies the inclination angle of the chamfer of the notch portion 45c of 6 degrees or more and 10 degrees or less.

[0072] In the present embodiment, as described above, the pneumatic tire 1 was described as an example of a tire. The pneumatic tire 1 can be inflated with any gas, including air and inert gas such as nitrogen. However, the configuration of the tread pattern of the pneumatic tire 1 described in the present embodiment can be applied to other tires as desired within the scope apparent to one skilled in the art. Examples of other tires include an airless tire and a solid tire. Examples

[0073] Fig. 4 and Fig. 5 are tables showing performance test results of pneumatic tires according to the embodiment. The following describes the performance tests conducted on the pneumatic tires of the conventional example and the pneumatic tires of the examples according to the embodiment. For the performance evaluation tests, rolling resistance performance and wet grip performance (wet traction performance) were conducted.

[0074] In rolling resistance performance evaluation tests, pneumatic tires (test tires) of size 315 / 70R22.5 are mounted on a specified rim, inflated to a specified air pressure, and mounted on a heavy-duty vehicle. The rolling resistance coefficient (ratio of rolling resistance to a load applied to the test tire) is measured under test conditions according to UN R117-04 (UN Regulation No. 117 Revision 4). Based on the measurement results, the evaluation is expressed as index values, with the value of the prior art example assigned the reference (100). Higher values ​​are preferable in this evaluation.

[0075] In wet grip performance evaluation tests, pneumatic tires (test tires) of the above size are mounted on a specified rim and inflated to a specified air pressure. A grip index value (ratio of the test tire's performance to the reference tire's performance) is then measured on a wet surface with a water depth of 1 mm under test conditions compliant with UN R117-04 (UN Regulation No. 117 Revision 4). Based on the measurement results, the evaluation is expressed as index values, with the prior art example assigned the reference (100). Higher values ​​are preferable in this evaluation.

[0076] The pneumatic tire of the prior art example is based on the Fig. 2, but is outside the specified range with respect to the specified contents (1) to (12) shown in Fig. 4 and Fig. 5 are illustrated.

[0077] The pneumatic tires in the examples are based on the Fig. 2 and are within the specified range with respect to the specified contents (1) to (12) shown in Fig. 4 and Fig. 5 are illustrated.

[0078] As can be seen from the test results, the rolling resistance performance and wet traction performance of the pneumatic tires of the examples are improved compared to the prior art example.

[0079] The present disclosure includes the following inventions. Invention 1

[0080] One tire, including: in a tread surface, of at least four circumferential grooves extending in the tire circumferential direction, a pair of main circumferential grooves formed at the respective outermost sides in the tire width direction and defining a central portion therebetween; of the four circumferential grooves, one or more narrow circumferential grooves arranged in the central portion and having a groove width of 30% or less of the groove width of the main circumferential grooves; and in at least three land portions defined by at least two of the circumferential grooves in the central portion and extending in the tire width direction, a plurality of lug grooves arranged in the tire circumferential direction with both ends of each communicating with the circumferential grooves adjacent in the tire width direction, and dividing each of the land portions into a plurality of blocks; wherein the central portion is provided closer to a center in the tire width direction within a range of 45% or more of a development width of the tread surface, the blocks divided in the web section closer to the center in the tire width direction are longer in the tire circumferential direction, and wherein the blocks have ends in the tire circumferential direction which are arranged offset in the tire circumferential direction in each of the web sections. Invention 2

[0081] The tire according to invention 1, wherein in the central portion, a tire circumferential direction length L1 of the block in the central land portion closest to the center in the tire width direction and a tire circumferential direction length L2 of the block in a middle land portion adjacent to the central land portion in the tire width direction satisfy the relationship 1.2 ≤ L1 / L2 ≤ 1.9. Invention 3

[0082] The tire according to invention 1 or 2, wherein in the central portion, a misalignment amount D in the tire circumferential direction between an end of the central land portion in the tire circumferential direction and an end of each of the blocks in middle land portions adjacent to the central land portion in the tire width direction with respect to a length in the tire circumferential direction L1 of the blocks in the central land portion closest to the center in the tire width direction satisfies the relationship 0.1 ≤ D / L1 ≤ 0.5. Invention 4

[0083] The tire according to any one of inventions 1 to 3, wherein the narrow circumferential groove has a groove width of 5 mm or less. Invention 5

[0084] The tire according to any one of inventions 1 to 4, wherein the lug grooves communicating with the circumferential main grooves have a groove width of 1.5 mm or more and 9 mm or less. Invention 6

[0085] The tire according to any one of inventions 1 to 5, wherein the lug grooves communicating with the circumferential main grooves extend at an angle of 20 degrees or more with respect to the tire width direction. Invention 7

[0086] The tire according to any one of inventions 1 to 6, wherein the main circumferential grooves include a pair of first groove walls extending from the tread surface toward a groove bottom side in a meridian cross-sectional shape, a pair of platform portions connected to the groove bottom side of each of the first groove walls and forming a platform along the tread surface, and a pair of second groove walls arranged closer to a groove center side than each of the first groove walls and extending from each of the platform sections toward the groove bottom side, wherein, in shoulder portions defined on outer sides in the tire width direction of the circumferential main grooves, a plurality of shoulder lug grooves are provided, extending in the tire width direction, arranged in the tire circumferential direction, having one end communicating with the circumferential main grooves, and including a raised bottom portion formed at a groove bottom, and the raised bottom portion of each of the shoulder lug grooves and each of the platform portions of the circumferential main grooves are seamlessly connected by an arc. List of reference symbols 1 pneumatic tire (tire) 15A tread surface 20 circumferential groove 21 Main circumferential groove 21b Grooved bottom 21c First groove wall 21d platform section 21e Second groove wall 22 Narrow circumferential groove 31 Central Section 31B Central bridge section 31Ba Central Block 31A Middle bridge section 31Aa Middle Block 32 shoulder section 41 Middle lug groove 41a End 42 Central lug groove 42a An End 45 shoulder lug groove 45a End 45b Raised floor section 45bc bow 45bd sheet QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2022-057908 A

[0003]

Claims

[1] Tires, comprising: in a tread surface, of at least four circumferential grooves extending in the tire circumferential direction, a pair of main circumferential grooves arranged on the respective outermost sides in the tire width direction and defining a central portion therebetween; of the four circumferential grooves, one or more narrow circumferential grooves arranged in the central portion and having a groove width of 30% or less of the groove width of the main circumferential grooves; and in at least three land portions defined by at least two of the circumferential grooves in the central portion, a plurality of lug grooves extending in the tire width direction are arranged in the tire circumferential direction, both ends of each communicating with the circumferential grooves adjacent in the tire width direction, and dividing each of the land portions into a plurality of blocks; wherein the central portion is provided closer to a center in the tire width direction within a range of 45% or more of a development width of the tread surface, wherein the blocks divided in the land portion closer to the center in the tire width direction are longer in the tire circumferential direction, and wherein the blocks have ends in the tire circumferential direction which are arranged offset in the tire circumferential direction in each of the web sections. [2] The tire according to claim 1, wherein, in the central portion, a tire circumferential direction length L1 of the blocks in the central land portion closest to the center in the tire width direction and a tire circumferential direction length L2 of the blocks in middle land portions adjacent to the central land portion in the tire width direction satisfy the relationship 1.2 ≤ L1 / L2 ≤ 1.

9. [3] The tire according to claim 1, wherein, in the central portion, a misalignment amount D in the tire circumferential direction between an end of the central land portion in the tire circumferential direction and an end of each of the blocks in middle land portions adjacent to the central land portion in the tire width direction with respect to a length in the tire circumferential direction L1 of the blocks in the central land portion closest to the center in the tire width direction satisfies a relationship of 0.1 ≤ D / L1 ≤ 0.

5. [4] A tire according to claim 1, wherein the narrow circumferential groove has a groove width of 5 mm or less. [5] A tire according to claim 1, wherein the lug grooves communicating with the circumferential main grooves have a groove width of 1.5 mm or more and 9 mm or less. [6] A tire according to claim 1, wherein the lug grooves communicating with the circumferential main grooves extend at an angle of 20 degrees or more with respect to the tire width direction. [7] Tire according to claim 1, wherein the main circumferential grooves include a pair of first groove walls extending from the tread surface toward a groove bottom side in a meridian cross-sectional shape, a pair of platform portions connected to the groove bottom side of each of the first groove walls and forming a platform along the tread surface, and a pair of second groove walls arranged closer to a groove center side than each of the first groove walls and extending from each of the platform sections toward the groove bottom side, wherein in shoulder portions defined on outer sides in the tire width direction of the circumferential main grooves, a plurality of shoulder lug grooves are provided, extending in the tire width direction, arranged in the tire circumferential direction, having one end, communicating with the main circumferential grooves and including a raised bottom portion formed at a groove bottom, and the raised bottom portion of each of the shoulder lug grooves and each of the platform portions of the main circumferential grooves are seamlessly connected by an arc.

Images