TIRES

Abstract

Task To provide a tire that can provide resistance to uneven wear and performance on snow in a compatible manner. Solution: A plurality of circumferential grooves (20) arranged in a tread surface (15A) includes a pair of outermost circumferential grooves (21) arranged on respective outermost sides in the tire width direction, and a narrow circumferential groove (22) having a groove width of 30% or less of a groove width of the outermost circumferential grooves (21). A central portion (31) has a width (CW) of 45% or more of a development width (TW) in the tire width direction. A lug groove (40) includes a closed lug groove (40a) that closes on one side of the groove bottom (40ab) from a position of at least half a groove depth (Dc) during ground contact, and an open lug groove (40b) that does not close during ground contact.A block (30) includes central blocks (31Ba) defined by the circumferential grooves (20) arranged on an inner side in the tire width direction of each of the outermost circumferential grooves (21). In a central block row (31B) in which the central blocks (31Ba) are arranged in the tire circumferential direction, the closed lug groove (40a) and the open lug groove (40b) are arranged alternately in the tire circumferential direction.

Description

Technical area

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

[0002] A vehicle-mounted tire includes a groove formed in a tread portion to ensure various performances according to a tire usage, and the performance is improved by designing the shape of the groove. For example, the pneumatic tire described in Patent Document 1 has a configuration in which a narrow circumferential groove extending along a tire circumferential direction is arranged in a tread portion to define a central rib-like land portion. An opening of the circumferential groove, which is closed during ground contact, brings the central rib-like land portions, positioned adjacent to each other via the circumferential groove, into contact with each other to support each other. Literature listPatent literature

[0003] Patent Document 1: JP 2012-020714 A Brief description of the inventionTechnical problem

[0004] In recent years, in order to reduce rolling resistance in a drive shaft tire, block rows have been intensively arranged in a central portion in the tire width direction with a circumferential groove as a narrow groove in many cases. Since the deformation of blocks during ground contact can be reduced by intensively arranging a block row near the central portion, it can also be expected to suppress uneven wear. Furthermore, intensively arranging the block row with the circumferential groove as a narrow groove also has the effect of reducing the groove volume. As the groove volume of the tread portion decreases, the snow column shear force is likely to decrease when driving on a snow-covered road surface, and therefore, the traction performance on a snow-covered road surface is likely to decrease.Therefore, it has been very difficult to provide suppression of uneven wear and mileage on a snow-covered road surface in a compatible manner.

[0005] The present invention has been made in view of the foregoing, and an object is to provide a tire that can provide resistance to uneven wear and performance on snow in a compatible manner. Solution to the problem

[0006] To solve the problems described above and achieve the object, a tire according to an embodiment of the present invention includes: at least four circumferential grooves arranged in a tread surface and extending in the tire circumferential direction; a plurality of lug grooves arranged at least between the circumferential grooves in the tread surface and extending in the tire width direction; and a block defined by the circumferential grooves and the lug grooves. The plurality of circumferential grooves includes a pair of outermost circumferential grooves arranged on the respective outermost sides in the tire width direction among the plurality of circumferential grooves, and a narrow circumferential groove having a groove width of 30% or less of a groove width of the outermost circumferential groove.A central portion, which is a portion of the tread between the pair of outermost circumferential grooves, has a tire width-direction width of 45% or more of a development width of the tread surface. The lug groove includes a closed lug groove that closes on a groove bottom side from a position of at least half a groove depth during block ground contact, and an open lug groove that does not close during block ground contact. The block includes central blocks defined by the circumferential grooves arranged on an inner side in the tire width direction of the outermost circumferential grooves. In a central block row in which the central blocks are arranged in the tire circumferential direction, the closed lug groove and the open lug groove are alternately arranged in the tire circumferential direction. Advantageous effects of the invention

[0007] The tire according to the present invention has the effect of being able to provide resistance to uneven wear and performance on snow in a compatible manner. Brief description of the drawings Fig. 1 illustrates a meridional cross-section of a pneumatic tire according to an embodiment, the cross-section of a lateral region of a tire rotation axis in the tire radial direction. 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 along line AA of Fig. 2. Fig. 4 is a cross-sectional view along BB of Fig. 2. Fig. 5 is a cross-sectional view along line CC of Fig. 2 and is a cross-sectional view of an open lug groove when the open lug groove is viewed along an extending direction of the open lug groove. Fig. 6 is a cross-sectional view along line EE of Fig. 2 and is a cross-sectional view of a closed lug groove when the closed lug groove is viewed along a direction of extension of the closed lug groove. Fig. Figure 7 is a cross-sectional view of the open lug groove of a block adjacent to the open lug groove during ground contact. Fig. Figure 8 is a cross-sectional view of the closed lug groove of a block adjacent to the closed lug groove during ground contact. Fig. 9 is a cross-sectional view along line FF of Fig. 2. Fig. 10 is a cross-sectional view along line GG of Fig. 2. Fig. 11A is a table showing the results of performance evaluation tests of pneumatic tires. Fig. Figure 11B is a table showing the results of performance evaluation tests of pneumatic tires. Description of embodiments

[0008] An 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 embodiment include elements that are interchangeable while maintaining consistency with the invention, as well as obviously interchangeable elements. The various modified examples described in the embodiment can be combined as needed within the scope obvious to a person skilled in the art. Embodiments

[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. The term "tire circumferential direction" refers to a circumferential direction with the tire rotation axis as a 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 CL (tire equator line) 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 direction center line corresponding to the tire width direction center position of the pneumatic tire 1. The term "tire equator line" refers to a line extending on the tire equatorial plane CL along the tire circumferential direction of the pneumatic tire 1. The term "cross section in the tire meridian direction (meridian cross-sectional view)" refers to a cross section of the tire along a plane including the tire rotation axis.

[0010] Fig. 1 illustrates a meridian cross section of the pneumatic tire 1 according to an embodiment, the cross section of a side portion of a 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 according to the present embodiment is particularly suitable for a tire mounted on a drive shaft of a heavy-duty vehicle. The pneumatic tire 1 according to the present embodiment is the pneumatic tire 1 in which the rotation direction is determined upon mounting on the vehicle. Therefore, the pneumatic tire 1 according to the present embodiment includes a rotation direction indicating portion (not illustrated) that indicates the rotation direction. The rotation direction indicating portion is configured, for example, by a mark or unevenness on a sidewall portion.

[0011] The pneumatic tire 1 according to the embodiment has an annular structure centered on 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 is formed by winding one or a plurality of bead wires made of steel in a ring-shaped and multiply manner, and is embedded in bead portions to form cores of bead portions on both sides in the tire width direction.

[0013] The pair of bead fillers 12 are each formed of a lower filler 121 and an upper filler 122. The pair of bead fillers 12 are arranged on the respective outer peripheries of the pair of bead cores 11 in the tire radial direction 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 is bridged in a torus shape between the two bead cores 11 to form a skeleton 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 layer 13 comprises a carcass ply formed by covering a plurality of carcass cords made of steel with coating rubber and performing a rolling process on the carcass cords, and has a cord angle (defined as an inclination angle in the longitudinal direction of the carcass cords with respect to the tire circumferential direction) of 80 degrees or more and 90 degrees or less as an absolute value in the case of a radial tire and 30 degrees or more and 45 degrees or less in the case of a bias tire.

[0015] The belt layer 14 is made of a plurality of belt plies 141 to 144 that are laminated and arranged around an outer periphery of the carcass ply 13. These 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 subjecting the belt cords to a rolling process, and has 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 in absolute value.The pair of cross belts 142 and 143 are formed by covering a plurality of belt cords made of steel with coating rubber and subjecting the belt cords to a rolling process, and each 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 that are opposite in sign and are layered so that the belt cords 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 the belt cover cords 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 forms 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 that comes into contact with a road surface during running.

[0017] The pair of sidewall rubbers 16 are arranged on an outer side in the tire width direction of the carcass layer 13 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 to an outer side in the tire width direction of a turned-up portion of each of the bead cores 11 and the carcass layer 13 to form a rim fitting surface of the bead portion.

[0019] Fig. 2 is a plan view of a tread surface 15A of the pneumatic tire 1 according to the embodiment. As shown in Fig. As illustrated in Fig. 2, the pneumatic tire 1 according to the embodiment includes a tread pattern on the tread surface 15A. Here, the dimensions in the tread pattern are measured in an unloaded state, with the tire mounted on a predetermined rim and inflated to the predetermined internal pressure.

[0020] The "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. The "specified internal pressure" refers to a "maximum inflation pressure" as defined by JATMA, the maximum value in "tire load limits at various cold inflation pressures" as defined by TRA, or "inflation pressures" as defined by ETRTO. A “specified load” refers to a “maximum load capacity” as specified by JATMA, to the maximum value in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” as specified by TRA or a “LOAD CAPACITY” as specified by ETRTO.

[0021] The pneumatic tire 1 includes at least four circumferential grooves 20 arranged in the tread surface 15A. In the present embodiment, four circumferential grooves 20 are arranged, and the circumferential grooves 20 extend along the tire circumferential direction and have an annular structure provided continuously over the entire circumference of the tire. The four circumferential grooves 20 include a pair of outermost circumferential grooves 21 and at least one narrow circumferential groove 22.

[0022] The pair of outermost circumferential grooves 21 are arranged on the respective outermost sides among the four circumferential grooves 20 in the tire width direction, with the circumferential grooves 20 having the widest groove width. That is, the two outermost circumferential grooves 21 are provided at positions on the outermost side among the four circumferential grooves 20 in the tire width direction, with the tire equatorial plane CL therebetween. In the present embodiment, each of the pair of outermost circumferential grooves 21 is formed in a zigzag shape that meanders in the tire width direction by repeatedly bending it while extending along the tire circumferential direction.

[0023] In the present embodiment, the outermost circumferential groove 21 is configured as a so-called main groove. The main groove mentioned here is defined as a groove that has the indication requirement of a tread wear indicator defined in JATMA on a groove bottom 21b.

[0024] In the pneumatic tire 1, three rows of land portions are formed on the tread surface 15A by the pair of outermost circumferential grooves 21, which are arranged along the tire circumferential direction in the tire width direction. Specifically, the pneumatic tire 1 includes a center portion 31 defined between the two outermost circumferential grooves 21 in the tire width direction, and shoulder portions 32 each defined on an outer side in the tire width direction of the outermost circumferential groove 21.

[0025] The central portion 31 is arranged to enclose the equatorial plane CL of the tire. Specifically, the central portion 31 has a width CW in the tire width direction within a range of 45% or more and 60% or less with respect to a development width TW of the tread surface 15A and is provided near the center in the tire width direction. The shoulder portions 32 defined on the outer side in the tire width direction of the outermost circumferential groove 21 are arranged on the respective two outermost sides of the tread surface 15A in the tire width direction.

[0026] Here, the development width TW is a dimensional development between ground ends T on both sides of the tread surface 15A in the tire width direction. The ground end T is defined as a position of maximum width in the tire width direction on a contact surface between the pneumatic tire 1 and a flat plate when the pneumatic tire 1 is mounted on the predetermined rim to exert the predetermined internal pressure and is placed perpendicular to the flat plate and a load corresponding to the predetermined load is applied. The width CW of the central portion 31 in the tire width direction is a dimension determined by the development between the ends on an inner side in the tire width direction of the opening portions 21a (see Fig. 9) of the outermost circumferential grooves 21 on the outermost side in the tire width direction.

[0027] Among the four circumferential grooves 20, the narrow circumferential groove 22 is located in the central portion 31. In the present embodiment, two narrow circumferential grooves 22 are provided adjacent to each other in the tire width direction, with the tire equatorial plane CL interposed therebetween. The narrow circumferential groove 22 is formed in a linear shape along the tire circumferential direction.

[0028] In the narrow circumferential groove 22, a groove width Wh is small compared to a groove width W1 in the opening portion 21a of the outermost circumferential groove 21. Specifically, the groove width Wh of the narrow circumferential groove 22 is 30% or less of the groove width W1 of the outermost circumferential groove 21.

[0029] Fig. 3 is a cross-sectional view along line AA of Fig. 2. The groove width Wh of the circumferential narrow groove 22 mentioned here is the groove width Wh at a position 50% of a groove depth Dn, which is a distance in the tire radial direction from the position of an opening portion 22a of the circumferential narrow groove 22 to a groove bottom 22b. That is, in the circumferential narrow groove 22, on the outer side in the tire radial direction from the position of the groove bottom 22b of the circumferential narrow groove 22, the groove width Wh at a position having a distance of 50% of the groove depth Dn of the circumferential narrow groove 22 is 30% or less of the groove width W1 of the outermost circumferential groove 21.

[0030] Fig. 4 is a cross-sectional view along BB of Fig. 2. In the present embodiment, in some blocks 30 defined by the narrow circumferential groove 22 in the tread surface 15A, a chamfered portion 61 and a recessed portion 60, which will be described later, are formed at positions adjacent to the narrow circumferential groove 22, and these chamfered portion 61 and the recessed portion 60 are positioned further on an outer side in the tire radial direction from the groove bottom 22b of the narrow circumferential groove 22 than a position of 50% of the groove depth Dn on the outer side in the tire radial direction.Therefore, even if the chamfered portion 61 or the recessed portion 60 is formed at a position adjacent to the narrow circumferential groove 22 in the block 30, in the narrow circumferential groove 22, the groove width Wh at a position of 50% of the groove depth Dn on an outer side in the tire radial direction from the groove bottom 22b is 30% or less of the groove width W1 of the outermost circumferential groove 21.

[0031] In the narrow circumferential groove 22 formed in this way, the groove width Wh at the position of 50% of the groove depth Dn on the outer side in the tire radial direction from the groove bottom 22b is in a range of 1 mm or more and 3 mm or less, and the groove depth Dn is in a range of 10 mm or more and 23.5 mm or less.

[0032] Note 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 groove 20 other than the narrow circumferential groove 20 in addition to the narrow circumferential groove 22 in the central portion 31 located between the pair of outermost circumferential grooves 21 located on the outermost side in the tire width direction as described above among the at least four circumferential grooves 22. When the circumferential groove 20 different from the narrow circumferential groove 22 is provided in the central portion 31, the circumferential groove 20, although not clearly illustrated in the figure, is formed in a linear shape along the tire circumferential direction and preferably has a groove width within a range of 5 mm or more and 20 mm or less and a groove depth within a range of 13.5 mm or more and 23.5 mm or less.

[0033] A plurality of lug grooves 40 extending in the tire width direction are formed in the tread surface 15. The lug groove 40 mentioned here is a groove extending in the tire width direction and having a groove width of more than 1 mm. The plurality of lug grooves 40 are arranged at least between the circumferential grooves 20 on the tread 15A. On the tread surface 15A, where the plurality of circumferential grooves 20 and the plurality of lug grooves 40 are arranged as described above, a plurality of blocks 30 defined by the circumferential grooves 20 and the lug grooves 40 are arranged.

[0034] The lug groove 40 includes a center lug groove 41 disposed between the outermost circumferential groove 21 and the narrow circumferential groove 22 adjacent to each other in the tire width direction, a center lug groove 42 disposed between the two narrow circumferential grooves 22, and a shoulder lug groove 45 disposed on an outer side in the tire width direction of the outermost circumferential groove 21.

[0035] The center lug groove 41 has an end portion on an outer side in the tire width direction that communicates with the outermost circumferential groove 21, and an end portion on an inner side in the tire width direction that communicates with the narrow circumferential groove 22. A plurality of the center lug grooves 41 thus formed are arranged in the tire circumferential direction. Therefore, a center block 31Aa, which is the block 30 defined by the outermost circumferential groove 21, the narrow circumferential groove 22, and the center lug groove 41, is formed between the outermost circumferential groove 21 and the narrow circumferential groove 22 in the tire width direction.The center block 31Aa has an outer side part in the tire width direction defined by the outermost circumferential groove 21, an inner side part in the tire width direction defined by the narrow circumferential groove 22, and parts on both sides in the tire circumferential direction defined by the center lug grooves 41.

[0036] Since the plurality of center lug grooves 41 are arranged side by side in the tire circumferential direction, the plurality of center blocks 31Aa are arranged side by side in the tire circumferential direction between the outermost circumferential groove 21 and the narrow circumferential groove 22, adjacent to each other in the tire width direction. The plurality of center blocks 31Aa arranged between the outermost circumferential groove 21 and the narrow circumferential groove 22 in the tire circumferential direction form a center block row 31A. In other words, the center block row 31A in which the plurality of center blocks 31Aa are arranged in the tire circumferential direction is provided between the outermost circumferential groove 21 and the narrow circumferential groove 22, which are adjacent to each other in the tire width direction.

[0037] The center lug groove 41 is formed to be inclined in the tire circumferential direction with respect to the tire width direction while being curved in a gentle S-shape in a direction in which the center lug groove 41 extends. A portion of the center lug groove 41 communicating with the outermost circumferential groove 21 communicates with a portion of the zigzag shape of the outermost circumferential groove 21 that protrudes and is bent on an inner side in the tire width direction.

[0038] The pneumatic tire 1 according to the present embodiment is the pneumatic tire 1 in which the direction of rotation is fixed, and the direction of a Fig. The direction of arrow R illustrated in FIG. 2 is the predetermined rotation direction. The center lug groove 41 inclined with respect to the tire width direction is inclined in an orientation in which the end portion on the inside in the tire width direction contacts the ground first when the tire rotates, and the end portion on the outside in the tire width direction contacts the ground later when the tire rotates.

[0039] In the central lug groove 42, both ends of the central lug groove 42 communicate with the respective two narrow circumferential grooves 22 adjacent to each other in the tire width direction. A plurality of the thus formed central lug grooves 42 are arranged in the tire circumferential direction. Therefore, a central block 31Ba, which is the block 30 defined by the two narrow circumferential grooves 22 and the central lug groove 42, is formed between the two narrow circumferential grooves 22 adjacent to each other in the tire width direction. That is, the central block 31Ba is the block 30 defined by the narrow circumferential grooves 22 arranged on the inner side in the tire width direction of the outermost circumferential groove 21.The central block 31Ba has parts defined by the narrow circumferential groove 22 on both sides in the tire width direction and parts defined by the central lug groove 42 on both sides in the tire circumferential direction.

[0040] Since the plurality of center lug grooves 42 are arranged side by side in the tire circumferential direction, the plurality of center blocks 31Ba are arranged side by side in the tire circumferential direction between the two narrow circumferential grooves 22 that are adjacent to each other in the tire width direction. The plurality of center blocks 31Ba arranged between the two narrow circumferential grooves 22 in the tire circumferential direction form a center block row 31B. In other words, the center block row 31B in which the plurality of center blocks 31Ba are arranged in the tire circumferential direction is provided between the two narrow circumferential grooves 22 that are adjacent to each other in the tire width direction. Since the two narrow circumferential grooves 22 are arranged on both sides of the equatorial plane of the tire CL in the tire width direction, the center block row 31B is arranged transversely to the equatorial plane of the tire CL in the tire width direction.

[0041] The center lug groove 42 is formed to be curved in a gentle arc shape in the direction in which the center lug groove 42 extends. The center lug groove 42 is curved in a direction in which a position near the center in the tire width direction faces forward in the tire rotation direction. Both the center lug groove 42 and the center lug groove 41 communicate with the circumferential narrow groove 22, but the tire circumferential direction position of a part where the center lug groove 42 communicates with the circumferential narrow groove 22 and the tire circumferential direction position of a part where the center lug groove 41 communicates with the circumferential narrow groove 22 are different from each other.

[0042] The shoulder lug groove 45 has an end portion on an inner side in the tire width direction that communicates with the outermost circumferential groove 21, extends on an outer side in the tire width direction from the position of the outermost circumferential groove 21, and intersects the bottom end T. A plurality of the shoulder lug grooves 45 thus formed are arranged in the tire circumferential direction. Therefore, a shoulder block 32a, which is the block 30 defined by the outermost circumferential groove 21 and the shoulder lug groove 45, is formed in an outer portion of the outermost circumferential groove 21 in the tire width direction. The shoulder block 32a has an inner side part in the tire width direction defined by the outermost circumferential groove 21, parts on both sides in the tire circumferential direction defined by the shoulder lug groove 45, and an outer side part in the tire width direction positioned at the bottom end T.

[0043] Since the plurality of shoulder lug grooves 45 are arranged side by side in the tire circumferential direction, the plurality of shoulder blocks 32a are arranged side by side in the tire circumferential direction in the part on the outer side in the tire width direction of the outermost circumferential groove 21. The shoulder portion 32 defined on the outer side in the tire width direction of the outermost circumferential groove 21 has the plurality of shoulder blocks 32a arranged in this manner in the tire circumferential direction.

[0044] The shoulder lug groove 45 is formed to be inclined in the tire circumferential direction with respect to the tire width direction while being curved in a gentle arc shape in the direction in which the shoulder lug groove 45 extends. Specifically, similar to the center lug groove 41, the shoulder lug groove 45 is inclined in an orientation in which the end portion on the inner side in the tire width direction contacts the ground first when the tire rotates, and the end portion on the outer side in the tire width direction contacts the ground later when the tire rotates.Both the shoulder lug groove 45 and the center lug groove 41 communicate with the outermost circumferential groove 21, but the position in the tire circumferential direction of a part where the shoulder lug groove 45 communicates with the outermost circumferential groove 21 and the position in the tire circumferential direction of a part where the center lug groove 41 communicates with the outermost circumferential groove 21 are positions different from each other.

[0045] The plurality of shoulder lug grooves 45 thus formed are preferably arranged at equal intervals in the tire circumferential direction and have a pitch in the tire circumferential direction within a range of 65 mm or more and 75 mm or less.

[0046] A central sub-lug groove 43 is arranged in the central block row 31. The central sub-lug groove 43 is the lug groove 40 extending in the tire width direction, with one end communicating with the circumferential narrow groove 22 and the other end terminating in the central block 31Ba. A plurality of the central sub-lug grooves 43 are arranged in the tire circumferential direction, and one central sub-lug groove 43 is provided for each central block 31Ba. That is, the central sub-lug groove 43 is arranged between the central lug grooves 42 that are adjacent to each other in the tire circumferential direction. Therefore, the plurality of central lug grooves 42 and the plurality of central sub-lug grooves 43 arranged in the central block row 31B are alternately arranged in the tire circumferential direction.

[0047] The central sub-lug grooves 43, which extend across the central lug groove 42 adjacent to each other in the tire circumferential direction, communicate with the circumferential narrow grooves 22 that are different from each other. That is, the central sub-lug grooves 43 arranged in the respective adjacent central blocks 31Ba in the tire circumferential direction include the circumferential narrow grooves 22 with which the central sub-lug grooves 43 communicate in different ways. The end portions of the central sub-lug grooves 43 on the side ending in the central block 31Ba are all positioned near the equatorial plane CL of the tire. In other words, the central sub-lug groove 43, one end of which ends in the central block 31Ba, ends near the center of the central block 31Ba in the tire width direction.Therefore, the central sub-lug groove 43 is arranged in a range from the vicinity of the center of the central block 31Ba in the tire width direction to one side of the central block 31Ba in the tire width direction.

[0048] The central sub-lug groove 43 communicates with the above-described narrow circumferential groove 22, but the position in the tire circumferential direction where the central sub-lug groove 43 communicates with the narrow circumferential groove 22 is the same position as the position in the tire circumferential direction where a center lug groove 41 of the plurality of center lug grooves 41, which communicates with the narrow circumferential groove 22, communicates with the narrow circumferential groove 22. Therefore, the part where the central sub-lug groove 43 communicates with the narrow circumferential groove 22 faces the part where any center lug groove 41 of the plurality of center lug grooves 41 communicates with the narrow circumferential groove 22. This causes the central sub-lug groove 43 to communicate with the center lug groove 41 via the narrow circumferential groove 22.

[0049] A plurality of sipes 50 are further arranged in the tread surface 15A. The sipe 50 mentioned here is formed in a narrow groove shape in the tread surface 15A and refers to a sipe in which the pneumatic tire 1 is provided on a predetermined rim, and the wall surfaces forming the narrow groove do not come into contact with each other under a state of internal pressure of a predetermined internal pressure at the time of no load, but the wall surfaces forming the narrow groove come into contact with each other by deformation of the block 30 when the narrow groove is positioned in a portion of a ground surface formed on a flat plate when it is loaded onto the flat plate in a vertical direction, or when the block 30 in which the narrow groove is formed falls.In the present embodiment, the sipe 50 has a groove width of 1 mm or less, and a maximum depth from the tread surface 15A is within a range of 10 mm or more and 18 mm or less.

[0050] The sipe 50 arranged in the tread surface 15A has a middle sipe 51 arranged on the middle block 31Aa and a central sipe 52 arranged on the central block 31Ba.

[0051] The center sipe 51 arranged in the center block 31Aa extends in the tire width direction and has an end portion on an outer side in the tire width direction that communicates with the outermost circumferential groove 21 and an end portion on an inner side in the tire width direction that communicates with the narrow circumferential groove 22. The part where the center sipe 51 communicates with the outermost circumferential groove 21 communicates with the part bent on an outer side in the tire width direction in the outermost circumferential groove 21 extending in the tire circumferential direction while being repeatedly bent in a zigzag shape. A plurality of the center sipes 51 are arranged in the center block row 31A and are arranged alternately in the tire circumferential direction with the center lug grooves 41 in the center block row 31A.Therefore, the center sipe 51 is provided to bisect the center block 31Aa in the tire circumferential direction, with both ends in the tire circumferential direction defined by the center lug groove 41. In this way, the center sipes 51, which are provided to bisect the center block 31Aa, are provided substantially in parallel along the direction in which the center lug groove 41 extends.

[0052] The central sipe 52, arranged in the center block 31Ba, extends in the tire width direction and has an end portion on an outer side in the tire width direction that communicates with the circumferential groove 22 and an end portion on an inner side in the tire width direction that terminates in the center block 31Ba. An end portion of the central sipe 52 on a side that terminates in the center block 31Ba communicates with an end portion of the central sub-lug groove 43 on a side that terminates in the center block 31Ba.

[0053] Specifically, the central sipe 52 is arranged on an extension line of the central sub-lug groove 43, and the circumferential narrow groove 22 with which the central sipe 52 communicates with the circumferential groove 22 is different from the circumferential narrow groove 22 with which the central sub-lug groove 43 communicates. That is, the central sipe 52 is arranged in a region on the opposite side to the side on which the central sub-lug groove 43 is arranged, in a region on both sides near the tire width direction center of the central block 31Ba in which the central sipe 52 is arranged.At this time, since the central sub-lug grooves 43 arranged in the central blocks 31Ba adjacent to each other in the tire circumferential direction communicate with the circumferential grooves 22 different from each other also in the central sipe 52, the central sipes 52 arranged in the central blocks 31Ba adjacent to each other in the tire circumferential direction communicate with the circumferential grooves 22 different from each other.

[0054] The position in the tire circumferential direction of the part where the central sipe 52 communicates with the circumferential narrow groove 22 is equal to the position in the tire circumferential direction of the part where any one of the middle sipes 51 arranged in the center block row 31A communicates with the circumferential narrow groove 22. Therefore, the part where the central sipe 52 communicates with the circumferential narrow groove 22 faces the part where any one of the middle sipes 51 of the plurality of middle sipes 51 communicates with the circumferential narrow groove 22. This causes the central sipe 52 to communicate with the middle sipe 51 via the circumferential narrow groove 22.

[0055] The plurality of central sipes 52 are arranged in the central block row 31B together with the central sub-lug groove 43, and are arranged alternately with the central lug groove 42 in the tire circumferential direction in the central block row 31B. Therefore, the central sub-lug groove 43 and the central sipe 52, which are provided for mutual communication, are provided so as to bisect the central block 31Ba, both ends of which in the tire circumferential direction are defined by the central lug groove 42, in the tire circumferential direction by the central sub-lug groove 43 and the central sipe 52. In this way, the central sub-lug groove 43 and the central sipe 52, which are provided for bisecting the central block 31Ba, are provided substantially in parallel along the direction in which the central sub-lug groove 43 extends.

[0056] In the block 30 in which a plurality of them are defined on the tread surface 15A by the circumferential groove 20 and the lug groove 40, the recess portion 60 is formed in an opening portion of the lug groove 40 to the circumferential groove 20.

[0057] Specifically, the center block 31Aa includes the recess portion 60 formed in each of an opening portion of the center lug groove 41 with respect to the narrow circumferential groove 22 and an opening portion of the center lug groove 41 with respect to the outermost circumferential groove 21. The recess portion 60 on the narrow circumferential groove 22 side and the recess portion 60 on the outermost circumferential groove 21 side in the center block 31Aa are formed at an acute angle part at a diagonal position of the center block 31Aa.

[0058] That is, since the center lug groove 41 defining the center block 31Aa is inclined in the tire circumferential direction with respect to the tire width direction, the center block 31Aa is formed in a parallelogram shape in plan view. The two recess portions 60 formed in the center block 31Aa are formed at acute angles at diagonal positions of the parallelogram shape in the center block 31Aa thus formed in the parallelogram shape. Therefore, the two recess portions 60 formed in the center block 31Aa are formed in a corner portion that is first loaded in the center block 31Aa when the pneumatic tire 1 rotates, and in a corner portion in a diagonal position that eventually yields.

[0059] The central block 31Ba includes the recess portion 60 formed in an opening portion of the central lug groove 42 with respect to the circumferential groove 22. The recess portion 60 of the central block 31Ba is formed at a corner portion of the central block 31Ba on a side where the angle formed by the groove wall of the curved central lug groove 42 and the groove wall of the narrow circumferential groove 22 is an acute angle among the central blocks 31Ba on both sides of the central lug groove 42 in the tire circumferential direction. As described above, the recess portion 60 formed in the opening portion of the central lug groove 42 to the narrow circumferential groove 22 is formed in the central block 31Ba in corner portions on both sides in the tire width direction, which eventually yield in the central block 31Ba when the pneumatic tire 1 rotates.

[0060] The shoulder block 32a includes the recess portion 60 formed in an opening portion of the shoulder lug groove 45 with respect to the outermost circumferential groove 21. The recess portion 60 of the shoulder block 32a is formed at a corner portion of the shoulder block 32a on a side where an angle formed between the groove wall of the curved shoulder lug groove 45 and the groove wall of the outermost circumferential groove 21 is an acute angle between the shoulder blocks 32a on both sides of the shoulder lug groove 45 in the tire circumferential direction. As described above, the recess portion 60 formed in the opening portion of the shoulder lug groove 45 with respect to the outermost circumferential groove 21 is formed in a corner portion that is first loaded in the shoulder block 32a when the pneumatic tire 1 rotates.

[0061] Furthermore, the center block 31Ba includes the chamfered portion 61 formed at an end portion on one side of end portions on both sides in the tire width direction. That is, the center block 31Ba includes the chamfered portion 61 formed at an edge on one side in the tire width direction. The chamfered portion 61 is formed such that the chamfer size is smallest near the center of the center block 31Ba in the tire circumferential direction, and the chamfer size increases toward both ends of the center block 31Ba in the tire circumferential direction.

[0062] The chamfered portion 61 thus formed in the central block 31Ba is formed at the edge on the side formed by the narrow circumferential groove 22 with which the central sipe 52 communicates between the edges on both sides of the central block 31Ba in the tire width direction. Therefore, in the chamfered portion 61 formed in the central block 31Ba, similar to the central sipe 52, the chamfered portions 61 formed in the central blocks 31Ba are adjacent to each other across the central lug groove 42 in the tire circumferential direction, at the edges of the central blocks 31Ba on sides different from each other in the tire width direction.

[0063] A tread pattern is formed in the tread surface 15A by the plurality of circumferential grooves 20 and the plurality of lug grooves 40. Among them, the lug groove 40 includes a closed lug groove 40a and an open lug groove 40b. The closed lug groove 40a is the lug groove 40 that closes on the groove bottom side from a position of at least half the groove depth during ground contact of the block 30 adjacent to the closed lug groove 40a. The open lug groove 40b is the lug groove 40 that is not closed during ground contact of the block 30 adjacent to the open lug groove 40b.

[0064] Among the 40 lug grooves arranged in the central block row 31B, the central lug groove 42 is the closed lug groove 40a, and the central sub-lug groove 43 is the open lug groove 40b. Therefore, in the central block row 31B in which the central blocks 31Ba are arranged in the tire circumferential direction, the closed lug grooves 40a and the open lug grooves 40b are alternately arranged in the tire circumferential direction. In the present embodiment, the closed lug groove 40a arranged in the central block row 31B consists of the central lug groove 42, both ends of which communicate with the respective narrow circumferential grooves 22. Since the open lug groove 40b arranged in the central block row 31B is formed from the central sub-lug groove 43, one end thereof communicates with the narrow circumferential groove 22 and the other end thereof terminates in the central block 31Ba.

[0065] The center lug grooves 41, which are the lug grooves 40 arranged in the center block row 31A, are all closed lug grooves 40a. Therefore, the lug grooves 40 defining the majority of the center blocks 31Aa arranged in the center block row 31A are all closed lug grooves 40a. In the present embodiment, since the closed lug groove 40a arranged in the center block row 31A is formed from the center lug groove 41, the end portion on the outer side in the tire width direction communicates with the outermost circumferential groove 21, and the end portion on the inner side in the tire width direction communicates with the narrow circumferential groove 22.

[0066] Fig. 5 is a cross section along line CC of Fig. 2 and is a cross section of the open lug groove 40b when the open lug groove 40b is viewed along the extending direction of the open lug groove 40b. Fig. 6 is a cross section along line EE of Fig. 2 is a cross-sectional view of the closed lug groove 40a when the closed lug groove 40a is viewed along the extending direction of the closed lug groove 40a. The open lug groove 40b has a ratio between a groove width Wo and a groove depth Do within a range of 3.5 ≤ Do / Wo ≤ 15. The groove width Wo of the open lug groove 40b in this case is the groove width at the position of an opening portion 40ba, and the groove depth Do is the distance in the tire radial direction from the position of the opening portion 40ba to the position of a groove bottom 40bb.

[0067] The closed lug groove 40a has a ratio between a groove width Wc and a groove depth Dc within a range of 5.0 ≤ Dc / Wc ≤ 15. The groove width Wc of the closed lug groove 40a in this case is the groove width at the position of an opening portion 40aa, and the groove depth Dc is the distance in the tire radial direction from the position of the opening portion 40aa to the position of a groove bottom 40ab.

[0068] Fig. 7 is a cross-sectional view of the open lug groove 40b of the block 30 adjacent to the open lug groove 40b during ground contact. When the block 30 adjacent to the open lug groove 40b comes into contact with the ground, the block 30 is deformed by the load during ground contact, and therefore, the groove width of the open lug groove 40b decreases. The open lug groove 40b has a width Wog of the opening portion 40ba of the block 30 adjacent to the open lug groove 40b during ground contact within a range of 1.5 mm ≤ Wog ≤ 7 mm.

[0069] Fig. 8 is a cross-sectional view of the closed lug groove 40a of the block 30 adjacent to the closed lug groove 40a during ground contact. Similarly, in the closed lug groove 40a, when the block 30 adjacent to the closed lug groove 40a comes into contact with the ground, the block 30 is deformed by the load during ground contact, and therefore, the groove width of the closed lug groove 40a decreases. This causes the closed lug groove 40a to close on the groove bottom 40ab side from the position of at least half the groove depth Dc during ground contact of the block 30 adjacent to the closed lug groove 40a.In the present embodiment, the closed lug groove 40a has a ratio between a height Hc from the groove bottom 40ab at a position of closing during ground contact of the block 30 adjacent to the closed lug groove 40a and the groove depth Dc of the closed lug groove 40a within a range of 0.5 ≤ Hc / Dc ≤ 0.8.

[0070] Therefore, even if a part on the groove bottom 40ab side is closed because the block 30 adjacent to the closed lug groove 40a is in contact with the ground, the closed lug groove 40a remains in a state where a part near the opening portion 40aa is open. As described above, the closed lug groove 40a, which is maintained in the state where the opening portion 40aa side is open during the ground contact of the block 30 adjacent to the closed lug groove 40a, has a width Wcg of the opening portion 40aa of the block 30 during the ground contact within a range of 1.5 mm≤Wcg≤5 mm.

[0071] The groove widths of the closed lug groove 40a and the open lug groove 40b during ground contact are measured using, for example, a CT scan image or the like in a state where the pneumatic tire 1 is applied with a load of 70% to 100% of the predetermined load.

[0072] Fig. 9 is a cross-sectional view along line FF of Fig. 2. Among the four circumferential grooves 20, the pair of outermost circumferential grooves 21, located on the outermost side in the tire width direction, includes a pair of first groove walls 21c, a pair of platform portions 21d, and a pair of second groove walls 21e between the opening portion 21a and the groove bottom 21b. 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 21a 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 a platform that is higher on the outer side in the tire radial direction than the groove bottom 21b along the tread surface 15A.The pair of second groove walls 21e is positioned closer to the central side in the groove width direction of the outermost circumferential groove 21 than each of the first groove walls 21c and extends from each of the platform portions 21d to the groove bottom 21b.

[0073] The outermost circumferential groove 21 formed in this way has a groove width W1 of the opening portion 21a within a range of 10.0 mm or more and 20.0 mm or less, and a groove width W2 between the second groove walls 21e or a distance W2 between the platform portions 21d within a range of 3.0 mm or more and 4.5 mm or less. The outermost circumferential groove 21 has a groove depth D1 from the tread surface 15A to the groove bottom 21b within a range of 13.5 mm or more and 23.5 mm or less, and a groove depth D2 from the tread surface 15A to the platform portion 21d within a range of 7.5 mm or more and 17.5 mm or less.

[0074] The outermost circumferential groove 21 is formed such that an angle θ1 of each of the first groove walls 21c extends from the groove bottom 21b side to the opening portion 21a side toward the tread surface 15A. The angle θ1 of the first groove wall 21c of the outermost circumferential groove 21 is within a range of 10 degrees or more and 14 degrees or less with respect to a normal line of a profile of the tread surface 15A at one end in the tire width direction of the opening portion 21a.

[0075] Fig. 10 is a cross-sectional view along line GG of Fig. 2. In the shoulder lug groove 45, which communicates with the outermost circumferential groove 21 from the outer side in the groove width direction, a raised bottom portion 45b is formed, which protrudes from the groove bottom to the outer side in the tire radial direction. In the raised bottom portion 45b, a top portion 45ba, which protrudes furthest from the groove bottom, is provided along the profile of the tread surface 15A where the shoulder lug groove 45 opens.

[0076] In the shoulder lug groove 45, a groove depth D3 from the tread surface 15A to the upper portion 45ba of the raised land portion 45b is shallower than the groove depth D1 (see Fig. 9) from the tread surface 15A to the groove bottom 21b in the outermost circumferential groove 21 and the groove depth D2 (see Fig. 9) from the tread surface 15A to the platform portion 21d in the outermost circumferential groove 21. The groove depth D3 of the shoulder lug groove 45 to the upper portion 45ba of the raised land portion 45b is within a range of 2.0 mm or more and 8.0 mm or less.

[0077] The groove depths D1, D2, and D3 of the outermost circumferential groove 21 and the shoulder lug groove 45 satisfy the relationships 0.50 ≤ D2 / D1 ≤ 0.90 and 0.10 ≤ D3 / D1 ≤ 0.40. The groove depths D1, D2, and D3 of the outermost circumferential groove 21 and the shoulder lug groove 45 preferably satisfy the relationships 0.60 ≤ D2 / D1 ≤ 0.70 and 0.25 ≤ D3 / D1 ≤ 0.35.

[0078] The raised land portion 45b has, on the inner side in the tire width direction, an inclined surface 45bb which is inclined on an inner side in the tire radial direction from the upper portion 45ba toward the platform portion 21d of the outermost circumferential groove 21. The inclined surface 45bb has an angle θ2 with respect to the profile normal of the tread surface 15A, and the shoulder lug groove 45 is opened within a range of 20 degrees or more and 60 degrees or less. The angle θ2 of the inclined surface 45bb is preferably within a range of 40 degrees or more and 50 degrees or less. The inclined surface 45bb is smoothly connected to the upper portion 45ba of the raised land portion 45b by an arc 45bc in a meridional cross section of a tire.The inclined surface 45bb is smoothly connected to the platform portion 21d of the outermost circumferential groove 21 on the outermost side in the tire width direction by an arc 45bd in a meridional cross-section of the tire. The arc 45bd connecting the inclined surface 45bb of the raised land portion 45b and the platform portion 21d of the outermost circumferential groove 21 preferably has a radius r within a range of 2 mm ≤ r ≤ 15 mm.

[0079] The raised lower portion 45b has, on the outer side in the tire width direction, an inclined surface 45be which is inclined on an inner side in the tire radial direction from the upper portion 45ba to an end 45a on an outer side of the shoulder lug groove 45 in the tire width direction. The inclined surface 45be has an angle θ3 with respect to the normal of the profile of the tread surface 15A, and the shoulder lug groove 45 is opened within a range of 10 degrees or more and 30 degrees or less. The angle θ3 of the inclined surface 45be is preferably within a range of 15 degrees or more and 25 degrees or less. The inclined surface 45be is smoothly connected to the upper portion 45ba of the raised lower portion 45b by an arc 45bf in a meridional cross section of the tire.

[0080] In the raised bottom portion 45b of the shoulder lug groove 45, a tire width direction WS1 of the shoulder lug groove 45 and a tire width direction WS2 of the upper portion 45ba of the raised bottom portion 45b satisfy the relationship 0.50≤WS2 / WS1≤0.90. The tire width direction dimension WS2 of the upper portion 45ba in this case is a tire width direction distance between the normal of the profile of the tread surface 15A passing through an intersection point of an extension line of the inclined surface 45bb of the raised bottom portion 45b and an extension line of the upper portion 45ba, and the normal of the profile of the tread surface 15A passing through an intersection point of an extension line of the inclined surface 45be and an extension line of the upper portion 45ba.The tire width direction dimension WS1 of the shoulder lug groove 45 is a tire width direction distance between the normal of the profile of the tread surface 15A at the position of the end on the outside in the tire width direction in the opening portion 21a of the outermost circumferential groove 21 and the normal of the profile of the tread surface 15A at the position of the bottom end T.

[0081] The tire width direction dimension WS1 of the shoulder lug groove 45 defined as described above and the tire width direction dimension WS2 of the upper portion 45ba preferably satisfy the relationship 0.60 ≤ WS2 / WS1 ≤ 0.80.

[0082] In the case of mounting the pneumatic tire 1 according to the present embodiment on a vehicle, the pneumatic tire 1 is mounted on a rim wheel, and inflated internally to an inflated state, and then mounted on the vehicle. Since the rotational direction is fixed at this time, the pneumatic tire 1 according to the present embodiment is mounted on the vehicle in an orientation in which the pneumatic tire 1 rotates in a fixed direction as the vehicle moves forward. That is, the pneumatic tire 1 is mounted on the vehicle in the orientation in which the pneumatic tire 1 rotates in the rotational direction indicated by the rotational direction indicating portion attached to the sidewall portion.

[0083] When the vehicle on which the pneumatic tire 1 is mounted travels, the pneumatic tire 1 rotates while the tread surface 15A positioned below the tread surfaces 15A of the tire comes into contact with the road surface. When a vehicle on which the pneumatic tire 1 is mounted travels on a dry road surface, the vehicle travels by transmitting the driving force and braking force to the road surface and generating a rotational force by means of a friction force between the tread surface 15A and the road surface.

[0084] When the vehicle travels on a wet road surface, water between the tread surface 15A and the road surface enters grooves such as the circumferential groove 20, the lug groove 40, and the sipe 50, and the vehicle travels while using these grooves to drain the water between the tread surface 15A and the road surface. This allows the tread surface 15A to easily contact the road surface, allowing the vehicle to travel through the frictional force between the tread surface 15A and the road surface.

[0085] When driving on a snow-covered road surface, the pneumatic tire 1 compresses and solidifies the snow on the road surface through the tread surface 15A, and the snow on the road surface enters the circumferential groove 20 and the lug groove 40, thereby compressing and solidifying the snow in the grooves. In this state, when driving force or braking force acts on the pneumatic tire 1, or when a force in the tire width direction acts due to the vehicle's cornering, a so-called snow column shear force is generated between the pneumatic tire 1 and the snow, which is a shear force acting on the snow in the grooves.When driving on snow-covered road surfaces, the resistance between the pneumatic tire 1 and the road surfaces is generated by the snow column shear force, and thus, driving force and braking force can be transmitted to the road surfaces, ensuring snow traction characteristics. This enables the vehicle to drive on snow-covered road surfaces.

[0086] When the vehicle runs on a snow-covered road surface or an icy road surface, the vehicle also utilizes the edge action of the circumferential groove 20, the lug grooves 40, and the sipe 50. That is, when the vehicle runs on a snow-covered road surface or an icy road surface, the vehicle also runs by utilizing the resistance caused by the edges of the circumferential groove 20, the edges of the lug groove 40, and the edges of the sipe 50 sticking to snow surfaces or ice surfaces.

[0087] When the vehicle travels on an ice-covered road surface, water on the surface of the ice-covered road surface is absorbed by the sipe 50, and a water film between the ice-covered road surface and the tread surface 15A is removed, whereby the ice-covered road surface and the tread surface 15A easily come into contact with each other. This increases the resistance between the tread surface 15A and the ice-covered road surface due to frictional force and edge action, and can ensure the mileage of the vehicle mounted with the pneumatic tire 1.

[0088] During travel of the vehicle mounted with the pneumatic tire 1, the tread surface 15A comes into contact with the road surface as described above, and the vehicle travels while friction is generated between the tread surface 15A and the road surface. Therefore, the tread surface 15A gradually wears as the travel distance increases. When the tread surface 15A comes into contact with the road surface, slippage may occur between the tread surface 15A and the road surface, and therefore, the tread surface 15A also gradually wears.

[0089] On the other hand, when the tread surface 15A comes into contact with the road surface during vehicle travel, the block 30, whose tread surface 15A is in contact, is deformed by the load acting on the block 30. During vehicle travel, the block 30 moves while being deformed as described above. However, in the tread surface 15A, due to the deformation of the block 30, the amount of friction with the road surface varies slightly depending on the position of the tread surface 15A or the amount of slip with the road surface varies slightly. As described above, if the amount of friction with the road surface or the amount of slip with the road surface varies depending on the position of the tread surface 15A, uneven wear of the tread surface 15A may occur.

[0090] On the other hand, in the present embodiment, among the plurality of circumferential grooves 20 extending in the tire circumferential direction, the groove width of the pair of outermost circumferential grooves 21 located on the outermost side in the tire width direction is wider than the groove width of the narrow circumferential groove 22 located on the inner side in the tire width direction of the outermost circumferential groove 21. Therefore, it is possible to intensively arrange the blocks 30 in a part near the center in the tire width direction where the ground contact surface pressure tends to become high during ground contact of the tread surface 15A. This can suppress deformation during ground contact of the block 30 of the central portion 31, where a high ground contact surface pressure tends to occur, and suppress uneven wear due to the deformation of the block 30.

[0091] On the other hand, if the block 30 is concentrated near the center in the tire width direction, the groove area of ​​the circumferential groove 20 decreases near the center in the tire width direction, and thus, it may be difficult to ensure snow performance. On the other hand, in the present embodiment, the arrangement of the plurality of lug grooves 40 between the circumferential grooves 20 enables the snow column shear force to be ensured by the lug grooves 40 and enables the mileage to be maintained on the snow-covered road surface.

[0092] Furthermore, since the closed lug grooves 40a and the open lug grooves 40b in the central block row 31B are alternately arranged in the tire circumferential direction, the deformation of the block 30 caused by the closed lug grooves 40a being closed during ground contact can be suppressed even when the majority of the lug grooves 40 are arranged in the central portion 31, which tends to have high ground contact surface pressure. This can suppress the occurrence of uneven wear caused by the arrangement of a large number of the lug grooves 40 near the tire width-direction center, where the ground contact surface pressure tends to be high. This can provide uneven wear resistance and snow performance in a compatible manner.

[0093] Since the lug grooves 40 defining the center block 31Aa are all closed lug grooves 40a, it is possible to suppress the deformation of the center block 31Aa of the center block 31Aa during ground contact. This can suppress the occurrence of uneven wear in the center block row 31A in which the center blocks 31Aa are arranged in the tire circumferential direction. As a result, it is possible to more reliably improve the uneven wear resistance.

[0094] Since the closed lug groove 40a has a ratio between the groove width Wc and the groove depth Dc within a range of 5.0 ≤ Dc / Wc ≤ 15, the occurrence of uneven wear during running on a snow-covered road surface can be suppressed. That is, during ground contact, the relationship between the groove width Wc and the groove depth Dc of the closed lug groove 40a is Dc / Wc < 5.0, the groove depth Dc of the closed lug groove 40a is too shallow, and the closed lug groove 40a may therefore be difficult to close during ground contact of the block 30 adjacent to the closed lug groove 40a. In this case, it may be difficult to suppress the deformation of the block 30 during ground contact by the closed lug groove 40a, and it may be difficult to suppress the occurrence of uneven wear.When the ratio between the groove width Wc and the groove depth Dc of the closed lug groove 40a is Dc / Wc>15, the groove width Wc of the closed lug groove 40a is too narrow, and therefore, it may be difficult to ensure the snow column shear force in the closed lug groove 40a. In this case, it may even be difficult to provide the closed lug groove 40a to effectively ensure mileage on a snow-covered road surface.

[0095] On the other hand, when the ratio between the groove width Wc and the groove depth Dc of the closed lug groove 40a is within a range of 5.0 ≤ Dc / Wc ≤ 15, it is possible to suppress the groove depth Dc of the closed lug groove 40a from becoming too shallow and to suppress the groove width Wc of the closed lug groove 40a from becoming too narrow. This can suppress the occurrence of uneven wear by closing the closed lug groove 40a during ground contact of the block 30 adjacent to the closed lug groove 40a, while ensuring the snow column shear force in the closed lug groove 40a and ensuring mileage on the snow-covered road surface. This can more reliably provide uneven wear resistance performance and wet performance in a compatible manner.

[0096] Since the ratio between the groove width Wo and the groove depth Do in the open lug groove 40b is within the range of 3.5 ≤ Do / Wo ≤ 15, the snow column shear force in the open lug groove 40b can be more reliably ensured, and the running performance on a snow-covered road surface can be ensured. That is, when the ratio between the groove width Wo and the groove depth Do of the open lug groove 40b is Do / Wo < 3.5, the groove depth Do of the open lug groove 40b is too shallow, and therefore, it may be difficult to ensure the snow column shear force in the open lug groove 40b. In this case, it may even be difficult to provide the open lug groove 40b to effectively ensure the running performance on the snow-covered road surface.When the ratio between the groove width Wo and the groove depth Do of the open lug groove 40b (Do / Wo) is > 15, the groove depth Do of the open lug groove 40b is too deep, and therefore, it may be difficult to maintain the state in which the open lug groove 40b is open during ground contact of the block 30 adjacent to the open lug groove 40b. In this case, it may be difficult to ensure the snow column shear force in the open lug groove 40b. Even if the open lug groove 40b is provided, it may be difficult to effectively ensure mileage on the snow-covered road surface.

[0097] On the other hand, if the ratio between the groove width Wo and the groove depth Do of the open lug groove 40b is within a range of 3.5 ≤ Do / Wo ≤ 15, the groove depth Do can be specified with an appropriate depth relative to the groove width Wo of the open lug groove 40b. This can more reliably ensure the snow column shear force in the open lug groove 40b and ensure mileage on the snow-covered road surface. As a result, the on-snow performance can be more reliably improved.

[0098] Since the closed lug groove 40a has the width Wcg of the opening portion 40aa of the block 30 adjacent to the closed lug groove 40a during ground contact, the width Wcg being within the range of 1.5 mm ≤ Wcg ≤ 5 mm, it is possible to ensure the snow column shear force in the closed lug groove 40a and at the same time suppress the deformation of the block 30 during ground contact by the closed lug groove 40a. That is, when the width Wcg of the opening portion 40aa of the closed lug groove 40a of the block 30 during ground contact satisfies Wcg < 1.5 mm, the width Wcg of the opening portion 40aa of the closed lug groove 40a during ground contact is too narrow, and therefore it may be difficult to ensure the snow column shear force in the closed lug groove 40a.When the width Wcg of the opening portion 40aa of the closed lug groove 40a during ground contact of the block 30 satisfies Wcg>5 mm, the width Wcg of the opening portion 40aa of the closed lug groove 40a during ground contact is too wide, and the deformation of the block 30 during ground contact is difficult to suppress by the closed lug groove 40a, and the occurrence of uneven wear is difficult to suppress.

[0099] On the other hand, if the width Wcg of the opening portion 40aa of the block 30 adjacent to the closed lug groove 40a during ground contact is within the range of 1.5 mm ≤ Wcg ≤ 5 mm, the width Wcg of the opening portion 40aa of the block 30 during ground contact can be specified with an appropriate width. This can ensure the snow column shear force in the closed lug groove 40a and ensure running performance on the snow-covered road surface, while suppressing the deformation of the block 30 during ground contact and suppressing the occurrence of uneven wear by the closed lug groove 40a. This can more reliably provide uneven wear resistance and wet performance in a compatible manner.

[0100] Since the closed lug groove 40a has the ratio between the height Hc from the groove bottom 40ab at the position where the closed lug groove 40 of the block 30 is closed during ground contact and the groove depth Dc of the closed lug groove 40a within a range of 0.5 ≤ Hc / Dc ≤ 0.8, it is possible to ensure the snow column shear force in the closed lug groove 40a while suppressing the deformation of the block 30 during ground contact by the closed lug groove 40a.That is, if the ratio between the height Hc in the closed position during ground contact of the block 30 adjacent to the closed lug groove 40a and the groove depth Dc is Hc / Dc < 0.5, the height Hc in the closed position is too low, and deformation of the block 30 during ground contact is difficult to suppress by the closed lug groove 40a, and the occurrence of uneven wear is difficult to suppress. If the ratio between the height Hc in the closed position during ground contact of the block 30 adjacent to the closed lug groove 40a and the groove depth Dc is Hc / Dc > 0.8, the height Hc in the closed position is too high, and therefore it may be difficult to ensure the snow column shear force in the closed lug groove 40a.

[0101] On the other hand, when the ratio between the height Hc in the closed position of the block 30 adjacent to the closed lug groove 40a during ground contact and the groove depth Dc is within a range of 0.5 ≤ Hc / Dc ≤ 0.8, the height Hc in the closed position during ground contact of the block 30 can be specified as a suitable height. This can ensure the snow column shear force in the closed lug groove 40a and ensure mileage on the snow-covered road surface, while suppressing the deformation of the block 30 during ground contact and suppressing the occurrence of uneven wear by the closed lug groove 40a. This can more reliably provide uneven wear resistance and wet performance in a compatible manner.

[0102] Since the open lug groove 40b has the width Wog of the opening portion 40ba of the block 30 adjacent to the open lug groove 40b during ground contact within a range of 1.5 mm ≤ Wog ≤ 7 mm, a snow column shear force is possible in the open lug groove 40b while maintaining the rigidity of the block 30 adjacent to the open lug groove 40b. That is, if the width Wog of the opening portion 40ba of the open lug groove 40b of the block 30 during ground contact is Wog < 1.5 mm, the width Wog of the opening portion 40ba of the open lug groove 40b during ground contact is too narrow, and therefore it may be difficult to ensure the snow column shear force in the open lug groove 40b.If the width Wog of the opening portion 40ba of the open lug groove 40b of the block 30 during ground contact is Wog>7 mm, the width Wog of the opening portion 40ba of the open lug groove 40b during ground contact is too wide, and therefore, the rigidity of the block 30 adjacent to the open lug groove 40b may be slightly reduced. In this case, since the block 30 is easily deformed during ground contact of the block 30 adjacent to the open lug groove 40b, it may be difficult to suppress the occurrence of uneven wear.

[0103] On the other hand, if the width Wog of the opening portion 40ba of the block 30 adjacent to the open lug groove 40b during ground contact is within the range of 1.5 mm ≤ Wog ≤ 7 mm, the width Wog of the opening portion 40ba of the block 30 during ground contact can be specified with an appropriate width. This can ensure the snow column shear force in the open lug groove 40b and ensure running performance on the snow-covered road surface, while ensuring the rigidity of the block 30 adjacent to the open lug groove 40b and suppressing the deformation of the block 30 during ground contact. This can more reliably provide uneven wear resistance and wet performance in a compatible manner.

[0104] Since the block 30 includes the recess portion 60 formed in the opening portion of the lug groove 40 to the circumferential groove 20, the groove volume can be increased by the recess portion 60. This can more reliably ensure the snow column shear force and can ensure running performance on the snow-covered road surface. As a result, the performance on snow can be more reliably improved.

[0105] Since the narrow circumferential groove 22 has a groove width Wh at a position of 50% of the groove depth Dn of 3 mm or less, the distance between the blocks 30 arranged in the central portion 31 can be reduced. This can suppress deformation of the block 30 during ground contact of the block 30 arranged in the central portion 31, where the ground contact surface pressure tends to increase, by bringing the blocks 30 into contact with each other to support each other and suppressing the occurrence of uneven wear. As a result, it is possible to more reliably improve the uneven wear resistance.

[0106] Since the raised bottom portion 45b is formed in the shoulder lug groove 45, it is possible to suppress the leakage of sound from the outermost circumferential groove 21 through the shoulder lug groove 45 to an outer side in the tire width direction by the raised bottom portion 45b when the pneumatic tire 1 rolls. This can suppress the passage noise, which is noise generated when the pneumatic tire 1 rolls, and improve the passage noise performance.

[0107] Since the outermost circumferential groove 21 is formed in the shape of a plane-divided platform with the pair of platform portions 21d, it is possible to define the rigidity of the block 30 by the outermost circumferential groove 21 while the groove width W1 is at the position of the opening portion 21a. Furthermore, since the raised bottom portion 45b of the shoulder lug groove 45 and the platform portion 21d of the outermost circumferential groove 21 are smoothly connected by the arc 45bd, the rigidity of the block 30 can be more reliably ensured. This can suppress the deformation of the block 30 while maintaining drainage performance in the outermost circumferential groove 21, and thus can reduce rolling resistance while maintaining wet performance, which is running performance on a wet road surface. As a result, rolling resistance can be reduced while improving passage noise performance and wet performance.

[0108] The outermost circumferential groove 21 is formed in a stepped platform shape, the raised bottom portion 45b is formed in the shoulder lug groove 45, and the raised bottom portion 45b of the shoulder lug groove 45 and the platform portion 21d of the outermost circumferential groove 21 are smoothly connected by the arc 45bd, thereby making it possible to provide a shape that prevents a stone that may penetrate into a connecting portion between the outermost circumferential groove 21 and the shoulder lug groove 45 from reaching the groove bottom 21b of the outermost circumferential groove 21. This can improve the anti-stone accumulation performance.

[0109] Since the groove depth D1 of the outermost circumferential groove 21 and the groove depth D2 up to the platform portion 21d satisfy the relationship 0.50 ≤ D2 / D1 ≤ 0.90, the groove depth D2 of the platform portion 21d can be defined within a suitable range, and the stone can be prevented from becoming lodged in the groove bottom 21b of the outermost circumferential groove 21, and the stone can be easily removed. Since the groove depth D1 of the outermost circumferential groove 21 and the groove depth D3 up to the raised bottom portion 45b of the shoulder lug groove 45 satisfy the relationship 0.10 ≤ D3 / D1 ≤ 0.40, the groove depth D3 up to the raised bottom portion 45b can be defined within a suitable range, and the noise escaping outward in the tire width direction can be suppressed to improve the through noise performance.

[0110] Since the pair of first groove walls 21c enclosed in the outermost circumferential groove 21 is formed to expand toward the tread surface 15A, a difference in groove width occurs between the tread surface 15A side and the platform portion 21d side, and the removal performance of stuck stones is improved. Since the groove volume of the outermost circumferential groove 21 decreases toward the groove bottom 21b, the effect of reducing passage noise is not impaired.

[0111] Since 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 bottom portion 45b satisfy the relationship 0.50 ≤ WS2 / WS1 ≤ 0.90, the tire width direction dimension WS2 of the raised bottom portion 45b can be defined within a suitable range. This improves the anti-stone accumulation performance in the shoulder lug groove 45. By disposing the raised bottom portion 45b in the shoulder lug groove 45 of the shoulder portion 32 where sound can easily escape on an outer side in the tire width direction, the escaping sound is reduced, and the passage noise is reduced due to the reduced groove volume.

[0112] Since the raised bottom portion 45b of the shoulder lug groove 45 has the angle θ2 of the inclined surface 45bb being 20 degrees or more and 60 degrees or less, and the angle θ3 of the inclined surface 45be being 10 degrees or more and 30 degrees or less, the angle θ2 of the inclined surface 45bb and the angle θ3 of the inclined surface 45be can be defined within a suitable range. This smoothly releases the stone stuck in the shoulder lug groove 45, improving the anti-stone accumulation performance. By assigning fixed ranges to the angle θ2 and the angle θ3 of the raised bottom portion 45b, the effect of reducing passage noise will not be impaired.

[0113] When the majority of shoulder lug grooves 45 are arranged at equal intervals in the tire circumferential direction, since the groove area of ​​the shoulder portion 32 can be made uniform, the effect of reducing passage noise is maintained. Since the shoulder lug groove 45 extends in an arc shape, the stuck stone can be removed smoothly.

[0114] The shoulder block 32a includes the recess portion 60 formed at an acute angle where the shoulder lug groove 45 communicates with the outermost circumferential groove 21. The recess portion 60 reaches the platform portion 21d of the outermost circumferential groove 21 and is chamfered to be inclined on an inner side in the tire radial direction. This can suppress the generation of impact noise during driving. Modified examples

[0115] In the above-described embodiment, the circumferential grooves 20 include the two narrow circumferential grooves 22 among the four circumferential grooves 20, but the number of narrow circumferential grooves 22 may be other than two, for example, one. In this case, the circumferential groove 20, which is positioned further on an inner side in the tire width direction than the outermost circumferential groove 21 and is different from the narrow circumferential groove 22, is formed in a groove width wider than the narrow circumferential groove 22.

[0116] In the embodiment described above, four circumferential grooves 20 are provided, but the number of circumferential grooves 20 may be different from four. The number of circumferential grooves 20 may be five or six, for example, but need only be four or more.

[0117] In the embodiment described above, the open lug groove 40b arranged in the central block row 31B ends in the central block 31Ba, but the open lug grooves 40b do not have to end in the central block 31Ba, but may be connected to the circumferential groove 20 at both ends.

[0118] In the above-described embodiment, the majority of the lug grooves 40 arranged in the center block row 31A are all closed lug grooves 40a, but the open lug grooves 40b may be arranged in the center block row 31A. In the center block row 31A, the closed lug grooves 40a and the open lug grooves 40b may be arranged alternately in the tire circumferential direction, similar to, for example, the center block row 31B.

[0119] 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 filled 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 also be applied to other tires, as far as one skilled in the art can appreciate. Examples of other tires include an airless tire and a solid tire. Examples

[0120] Fig. 11A and Fig. 11B are tables showing the results of performance evaluation tests of the pneumatic tire 1. Performance evaluation tests conducted on the pneumatic tire 1 of the prior art example and the pneumatic tire 1 according to the present invention will be described below. In the performance evaluation test, tests for uneven wear resistance performance and snow acceleration performance were conducted.

[0121] The performance evaluation tests were conducted under the condition that pneumatic tire 1 with the tire designation 315 / 80R22.5 724D was mounted on a rim wheel with a rim size of 22.5 × 9.00 and the air pressure was adjusted to a specified air pressure.

[0122] The evaluation method for each test item was carried out for the uneven wear resistance performance by mounting a test tire on a heavy-duty vehicle, conducting a road test, and checking the degree of so-called heel and toe wear after driving until the wear rate of the outermost circumferential groove 21, which is a main circumferential groove, reached 30%. Specifically, for each block 30, the difference between the wear amounts of the edges at both ends in the tire circumferential direction was measured, and the reciprocal of the measured difference between the wear amounts was expressed as an index, with the known example described later being indicated as 100. This numerical value, which is larger, indicates that the uneven wear of the block 30 is smaller and that the uneven wear resistance performance is better.

[0123] The snow acceleration performance was conducted in accordance with UN R117-04 (UN Regulation No. 117, Revision 4). The acceleration was calculated by measuring the distance required to accelerate from a specified initial speed to a final speed on a snow-covered road surface using a heavy-duty vehicle mounted with the test tire. When evaluating snow acceleration performance, the calculated acceleration is evaluated using an index with the familiar example described later as 100. The larger the numerical value, the more excellent the acceleration performance on the snow-covered road surface and the higher the snow acceleration performance.

[0124] The performance evaluation test was conducted on 16 types of pneumatic tires, including a pneumatic tire of the conventional example and Examples 1 to 15, which are the pneumatic tires 1 according to the present invention. Among them, the pneumatic tire of the conventional example has a narrow circumferential groove but no closed lug groove, and the closed lug groove and the open lug groove are not arranged alternately in the tire circumferential direction.

[0125] On the other hand, Examples 1 to 15, which are examples of the pneumatic tires 1 according to the present invention, all have the closed lug grooves 40a and the open lug grooves 40b, and the closed lug grooves 40a and the open lug grooves 40b are alternately arranged in the tire circumferential direction in the center block row 31B.In addition, in the pneumatic tires 1 according to Examples 1 to 15, the width Wcg of the opening portion of the closed lug groove 40a during ground contact, the ratio Hc / Dc between the height Hc of the closing position of the closed lug groove 40a and the groove depth Dc, the width Wog of the opening portion of the open lug groove 40b during ground contact, the presence or absence of the recess portion 60 formed in the opening portion of the lug groove 40 to the circumferential groove 20 in the block 30, and whether the groove width Wh of the narrow circumferential groove 22 is 3 mm or smaller are different from each other.

[0126] As a result of conducting the performance evaluation test using these pneumatic tires 1 as shown in Fig. 11A and Fig.As shown in Figure 11B, it was found that the pneumatic tires 1 according to Examples 1 to 15 can improve both the uneven wear resistance performance and the snow acceleration performance compared to the prior art example. That is, the pneumatic tire 1 according to Examples 1 to 15 can provide uneven wear resistance and snow acceleration performance in a compatible manner.

[0127] The present disclosure includes the following embodiments of the inventions. Invention [1]

[0128] Tires, including: at least four circumferential grooves arranged in a tread surface and extending in the tire circumferential direction; a plurality of lug grooves arranged at least between the circumferential grooves in the tread surface and extending in the tire width direction; and a block defined by the circumferential grooves and the lug grooves; wherein the plurality of circumferential grooves include a pair of outermost circumferential grooves arranged on the respective outermost sides in the tire width direction among the plurality of circumferential grooves, and a narrow circumferential groove having a groove width of 30% or less of a groove width of the outermost circumferential grooves, wherein a central portion, which is a portion of the tread surface between the pair of outermost circumferential grooves, has a width in the tire width direction of 45% or more of a development width of the tread surface, wherein the lug groove includes a closed lug groove that closes on a groove bottom side from a position of at least one half of a groove depth during ground contact of the block, and an open lug groove that does not close during ground contact of the block, wherein the block includes central blocks defined by the circumferential grooves arranged on an inner side in the tire width direction of the outermost circumferential grooves, and wherein in a central block row in which the central blocks are arranged in the tire circumferential direction, the closed lug groove and the open lug groove are arranged alternately in the tire circumferential direction. Invention [2]

[0129] The tire according to invention [1], wherein the block includes center blocks defined by the circumferential grooves and the outermost circumferential grooves arranged on the inner side in the tire width direction of the outermost circumferential grooves, and all the lug grooves defining the center blocks are closed lug grooves. Invention [3]

[0130] The tire according to invention [1] or [2], wherein the closed lug groove has a ratio between a groove width Wc and a groove depth Dc within a range of 5.0 ≤ Dc / Wc ≤ 15. Invention [4]

[0131] The tire according to any one of the inventions [1] to [3], wherein the open lug groove has a ratio between a groove width Wo and a groove depth Do in a range of 3.5 ≤ Do / Wo ≤ 15. Invention [5]

[0132] The tire according to any one of the inventions [1] to [4], wherein the closed lug groove has a width Wcg of an opening portion of the block during ground contact within a range of 1.5 mm ≤ Wcg ≤ 5 mm. Invention [6]

[0133] The tire according to any one of the inventions [1] to [5], wherein the closed lug groove has a ratio between a height Hc from the groove bottom at a closing position during ground contact of the block and a groove depth Dc of the closed lug groove within a range of 0.5 ≤ Hc / Dc ≤ 0.8. Invention [7]

[0134] The tire according to any one of the inventions [1] to [6], wherein the open lug groove has a width Wog of an opening portion of the block during ground contact within a range of 1.5 mm ≤ Wog ≤ 7 mm. Invention [8]

[0135] The tire according to any one of the inventions [1] to [7], wherein the block includes a recess portion formed in an opening portion of the lug grooves to the circumferential grooves. Invention [9]

[0136] The tire according to any one of the inventions [1] to [8], wherein the narrow circumferential groove has a groove width Wh at a position of 50% of a groove depth of 3 mm or less. Invention

[10]

[0137] The tire according to any one of the inventions [1] to [9], wherein the outermost circumferential grooves a pair of first groove walls extending from the tread surface to a groove bottom side, a pair of platform portions connected to the groove bottom of each of the first groove walls and forming a platform along the tread surface, and include a pair of second groove walls positioned further on a central side in a groove width direction than each of the first groove walls and extending from each of the platform portions to the groove bottom side, the lug groove includes a shoulder lug groove disposed on an outer side in the tire width direction of the outermost circumferential grooves, communicating with the outermost circumferential grooves, and including a raised bottom portion formed at a groove bottom, and the raised bottom portion of the shoulder lug groove and each of the platform portions of the outermost circumferential grooves are smoothly connected by an arc in a meridional cross-section of the tire. List of reference symbols 1 pneumatic tire 11 Bead core 12 bead fillers 13 carcass layers 14 Belt layer 15 Tread rubber 15A tread surface 16 sidewall rubber 17 Wheel rim cushion rubber 20 circumferential groove 21 Outermost circumferential groove 22 Narrow circumferential groove 30 blocks 31 Central Section 31A Middle Block Row 31Aa Middle Block 31B Central Block Row 31Ba Central Block 32 shoulder section 32a Shoulder block 40 lug groove 40a Closed lug groove 40b Open lug groove 41 Middle lug groove 42 Central lug groove 43 Middle sub-lug groove 45 shoulder lug groove 45b Raised floor section 50 slats 60 recess section 61 Bevelled section 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 2012-020714 A

[0003]

Claims

[1] Tires, comprising: at least four circumferential grooves arranged in a tread surface and extending in the tire circumferential direction; a plurality of lug grooves arranged at least between the circumferential grooves in the tread surface and extending in the tire width direction; and a block defined by the circumferential grooves and the lug grooves; wherein the plurality of circumferential grooves include a pair of outermost circumferential grooves arranged on the respective outermost sides in the tire width direction among the plurality of circumferential grooves, and a narrow circumferential groove having a groove width of 30% or less one groove width of the outermost circumferential groove, wherein a central portion, which is a portion of the tread surface between the pair of outermost circumferential grooves, has a width in the tire width direction of 45% or more of a development width of the tread surface, wherein the lug groove comprises a closed lug groove which closes on a groove bottom side from a position of at least half a groove depth during ground contact of the block, and an open lug groove which does not close during ground contact of the block, wherein the block comprises central blocks defined by the circumferential grooves arranged on an inner side in the tire width direction of the outermost circumferential grooves, and wherein in a central block row in which the central blocks are arranged in the tire circumferential direction, the closed lug groove and the open lug groove is arranged alternately in the tire circumferential direction. [2] A tire according to claim 1, wherein the block comprises center blocks defined by the circumferential grooves and the outermost circumferential grooves arranged on the inner side in the tire width direction of the outermost circumferential grooves, and all the lug grooves defining the center blocks are closed lug grooves. [3] The tire according to claim 1, wherein the closed lug groove has a ratio between a groove width Wc and a groove depth Dc within a range of 5.0 ≤ Dc / Wc ≤ 15. [4] A tire according to claim 1, wherein the open lug groove has a ratio between a groove width Wo and a groove depth Do within a range of 3.5 ≤ Do / Wo ≤ 15. [5] The tire according to claim 1, wherein the closed lug groove has a width Wcg of an opening portion of the block during ground contact within a range of 1.5 mm ≤ Wcg ≤ 5 mm. [6] The tire according to claim 1, wherein the closed lug groove has a ratio between a height Hc from the groove bottom at a closing position during ground contact of the block and a groove depth Dc of the closed lug groove within a range of 0.5 ≤ Hc / Dc ≤ 0.

8. [7] The tire according to claim 1, wherein the open lug groove has a width Wog of an opening portion of the block during ground contact within a range of 1.5 mm ≤ Wog ≤ 7 mm. [8] A tire according to claim 1, wherein the block includes a recess portion formed in an opening portion of the lug grooves to the circumferential grooves. [9] A tire according to claim 1, wherein the narrow circumferential groove has a groove width Wh at a position of 50% of a groove depth of 3 mm or less. [10] Tire according to claim 1, wherein the outermost circumferential grooves a pair of first groove walls extending from the tread surface to a groove bottom side, a pair of platform portions connected to the groove bottom of each of the first groove walls and forming a platform along the tread surface, and comprise a pair of second groove walls positioned further on a central side in a groove width direction than each of the first groove walls and extending from each of the platform portions to the groove bottom side, the lug groove comprises a shoulder lug groove arranged on an outer side of the outermost circumferential grooves in the tire width direction, communicating with the outermost circumferential grooves, and comprising a raised bottom portion formed at a groove bottom, and the raised bottom portion of the shoulder lug groove and each of the platform portions of the outermost circumferential grooves are smoothly connected by an arc in a meridian cross-section of the tire.

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