Tire

Abstract

A tire 10 comprises: circumferential main grooves 16; an inner land section 18 delimited and formed by at least two of the circumferential main grooves 16; and outer land sections 20 each disposed outward of the inner land section 18 in the tire width direction. In each of the outer land sections 20, inclined grooves 50, inclined narrow grooves 52, and reverse inclined grooves 54 are arranged. Each of the inclined grooves 50 extends outward in the tire width direction from a circumferential main groove 16, is inclined from the step-in side to the kick-out side, and has a tip 60 connected to a tread end T. Each of the inclined narrow grooves 52 extends outward in the tire width direction from the circumferential main groove 16, is inclined from the step-in side to the kick-out side, and has a tip 76 disposed in the outer land section 20. Each of the reverse inclined grooves 54 extends from the kick-out side to the step-in side, and is inclined outward from the inside in the tire width direction. The groove width W2 of each of the inclined narrow grooves 52 is 20-80% of the groove width W1 of each of the inclined grooves 50.

Description

tire

[0001] The present invention relates to a tire.

[0002] Winter tires with improved braking performance on snowy roads are known. For example, Patent Document 1 discloses a tire in which a plurality of block rows are formed on the tread surface by at least two circumferential main grooves extending in the circumferential direction and a plurality of lateral grooves extending from both tread edges toward the tire centerline at an inclination in the radial direction, and each block has a plurality of sipes.

[0003] Japanese Patent Application Publication No. 5-301508

[0004] In recent years, winter tires have been required to have high levels of wet and dry performance in addition to performance on snowy roads.

[0005] An object of the present invention is to provide a tire that is excellent in snow performance, wet performance and dry performance.

[0006] a narrow inclined groove extending from the circumferential main groove toward the outside in the tire width direction, inclined from the leading edge to the trailing edge in the tire circumferential direction, and having a tip connected to a tread edge; a narrow inclined groove extending from the circumferential main groove toward the outside in the tire width direction, inclined from the leading edge to the trailing edge in the tire circumferential direction, and having a tip located within the outer land portion; and a reverse inclined groove extending from the trailing edge to the leading edge in the tire circumferential direction, inclined from the inside to the outside in the tire width direction, and having a groove width of the narrow inclined groove that is 20% to 80% of the groove width of the oblique groove.

[0007] The tire of the present invention is excellent in snow performance, wet performance and dry performance.

[0008] 10 is a partial plan view of a tire according to a first embodiment. A partial enlarged plan view of a tire according to the first embodiment, centered on the tire equatorial plane. A partial enlarged cross-sectional view taken along line III-III in FIG. 2. A partial enlarged plan view of one side in the tire width direction from the tire equatorial plane of a tire according to the first embodiment. A partial enlarged cross-sectional view taken along line V-V in FIG. 4. A partial enlarged cross-sectional view taken along line VI-VI in FIG. 2. A partial enlarged cross-sectional view taken along line VII-VII in FIG. 4. A partial enlarged cross-sectional view taken along line VIII-VIII in FIG. 4. A partial plan view of a tire according to a second embodiment. A partial enlarged plan view of a tire according to a second embodiment, centered on a tread edge. A partial enlarged cross-sectional view taken along line XI-XI in FIG. 10. A partial enlarged cross-sectional view taken along line V-V in FIG. 4 of a tire according to a modified example (1). A partial enlarged plan view of a tire according to a modified example (2), centered on the tire equatorial plane. A partial enlarged plan view of a tire according to a modified example (3), centered on the tire equatorial plane. A partial enlarged plan view of a tire according to a modified example (4), centered on the tire equatorial plane. FIG. 10 is a partially enlarged cross-sectional view of a tire according to a modified example (5) taken along line XVI-XVI in FIG. 4.

[0009] The embodiments of the present invention relate to the following aspects.

[0010] [Aspect 1] A tire comprising: a circumferential main groove; an inner land portion defined by at least two of the circumferential main grooves; and outer land portions arranged on either side of the circumferential main groove on the outer side in the tire width direction of the inner land portion, wherein the tire has an inclined groove, an inclined narrow groove, and a reverse inclined groove arranged in the outer land portion, wherein the inclined groove extends from the circumferential main groove outward in the tire width direction, is inclined from the leading-in side to the trailing-out side in the tire circumferential direction, and has a tip connected to a tread edge, the inclined narrow groove extends from the circumferential main groove outward in the tire width direction, is inclined from the leading-in side to the trailing-out side in the tire circumferential direction, and has a tip arranged within the outer land portion, the reverse inclined groove extends from the trailing-out side to the leading-out side in the tire circumferential direction, and is inclined from the inner side to the outer side in the tire width direction, and the groove width of the inclined narrow groove is 20% to 80% of the groove width of the inclined groove.

[0011] [Aspect 2] The tire according to aspect 1, wherein an angle formed between the extending direction of the reverse inclined groove and the tire circumferential direction is 5° or more and 50° or less.

[0012] [Aspect 3] The tire according to Aspect 1 or 2, wherein the inclined groove has: a main inclined portion having a first groove depth; and a bottom-up portion having a second groove depth shallower than the first groove depth, between an end of the main inclined portion on an inner side in the tire width direction and the circumferential main groove.

[0013] Aspect 4: The tire according to any one of Aspects 1 to 3, wherein the inner land portion is disposed at a position including the tire equatorial plane and includes an inner inclined groove, the inner inclined groove including a first inner inclined groove and a second inner inclined groove extending inward in the tire width direction from the circumferential main groove and inclined from the trailing edge to the leading edge in the tire circumferential direction, the first inner inclined groove intersecting the tire equatorial plane.

[0014] [Aspect 5] The tire according to Aspect 4, wherein the first inner inclined groove has a first inclined portion, a second inclined portion, and a bent portion, the first inclined portion and the second inclined portion are connected via the bent portion, and the extending directions of the first inclined portion and the second inclined portion change at the bent portion.

[0015] [Aspect 6] The tire according to Aspect 5, wherein θa is an angle formed between the extension direction of the first inclined portion and the tire circumferential direction, and θb is an angle formed between the extension direction of the second inclined portion and the tire circumferential direction, θa is 30° or more and 70° or less, and satisfies the following formula (1): θa+5°≦θb≦90°... formula (1)

[0016] [Aspect 7] The tire according to any one of Aspects 4 to 6, wherein the groove depth of the inner oblique groove is 30% to 80% of the groove depth of the circumferential main groove.

[0017] [Aspect 8] The tire according to Aspect 4, wherein the inclined groove or the inclined narrow groove is disposed on an extension line of the inner inclined groove.

[0018] [Aspect 9] The tire according to any one of Aspects 1 to 8, wherein the distance between tread ends in the tire width direction is LDE and the length of the inner land portion in the tire width direction is Wce, satisfies the following formula (2): 0.08≦Wce / LDE≦0.20 (2)

[0019] [Aspect 10] The tire according to any one of Aspects 1 to 9, wherein the groove width of the opening end of the inclined groove connected to the circumferential main groove is Wa, and the groove width of the opening end of the inclined groove at the tread edge is Wb, the following formula (3) is satisfied: 0.3≦Wa / Wb≦0.8 (3)

[0020] [Aspect 11] The tire according to any one of Aspects 1 to 10, wherein the groove depth of the inclined narrow groove is 20% to 60% of the groove depth of the circumferential main groove.

[0021] [Aspect 12] The tire according to any one of Aspects 1 to 11, wherein the narrow inclined groove has a groove bottom sipe, the groove bottom sipe is formed at the groove bottom of the narrow inclined groove, and the following formula (4) is satisfied, where Dg is the groove depth of the narrow inclined groove and Ds is the groove depth of the groove bottom sipe: 0.7≦Ds / Dg≦1.3... formula (4):

[0022] [Aspect 13] The tire according to any one of Aspects 1 to 12, wherein the groove depth of the reverse oblique groove is 40% to 80% of the groove depth of the circumferential main groove.

[0023] [Aspect 14] The tire according to any one of Aspects 1 to 13, wherein the outer land portion has a plurality of blocks defined by the inclined grooves, the inclined narrow grooves, and the reverse inclined grooves, and some of the plurality of blocks have outer sipes.

[0024] [Aspect 15] The tire according to aspect 14, wherein the outer sipe extends along the oblique narrow groove.

[0025] [Aspect 16] The tire according to any one of Aspects 1 to 15, wherein the inner land portion has an inner sipe, and the inner sipe extends along the tire width direction.

[0026] [Aspect 17] The tire according to Aspect 14 or 15, wherein, of the plurality of blocks, an outermost block arranged outermost in the tire width direction has a recessed portion, the recessed portion being arranged outward in the tire width direction from a tip end of the inclined narrow groove, and the recessed portion has a plurality of edges intersecting in the tire circumferential direction.

[0027] [Aspect 18] The tire according to aspect 17, wherein the depth of the recess is 0.5 mm or more and 3.0 mm or less.

[0028] [Aspect 19] The tire according to any one of Aspects 1 to 18, having circumferential narrow grooves extending from the ground contact edge toward the inner side in the tire width direction, in a range of 5% to 15% of the tire width direction length from the tire equatorial plane to the ground contact edge.

[0029] [Aspect 20] The tire according to Aspect 19, wherein two circumferential narrow grooves are provided on each side in the tire width direction, and the groove width of the circumferential narrow groove on the outer side in the tire width direction of the two circumferential narrow grooves is Wout and the groove width of the circumferential narrow groove on the inner side in the tire width direction of the two circumferential narrow grooves is Win, satisfies the following formula (5): 0.3≦Wout / Win≦0.7 (5)

[0030] [Aspect 21] The tire according to Aspect 19 or 20, wherein two circumferential narrow grooves are provided on each side in the tire width direction, and the groove depth of the circumferential narrow groove on the outer side in the tire width direction of the two circumferential narrow grooves is defined as Dout and the groove depth of the circumferential narrow groove on the inner side in the tire width direction of the two circumferential narrow grooves is defined as Din, and the tire satisfies the following formula (6): 0.4≦Dout / Din≦0.8 (6)

[0031] [Aspect 22] The tire according to any one of Aspects 1 to 21, wherein the inclined grooves and the inclined narrow grooves are arranged alternately in the tire circumferential direction.

[0032] (Definitions) The tire radial direction refers to the direction perpendicular to the tire rotation axis, the tire radially inner side refers to the side toward the tire rotation axis in the tire radial direction, and the tire radially outer side refers to the side away from the tire rotation axis in the tire radial direction. The tire circumferential direction refers to the direction around the tire rotation axis as the central axis. The tire width direction refers to the direction parallel to the tire rotation axis, the tire widthwise inner side refers to the side toward the tire equatorial plane in the tire width direction, and the tire widthwise outer side refers to the side away from the tire equatorial plane in the tire width direction. The tire equatorial plane refers to a plane that is perpendicular to the tire rotation axis and passes through the center of the tire width. "Along" a certain reference includes along a direction within a range of less than ±20°, less than ±10°, or less than ±5° from the certain reference. "Center" includes the midpoint that is equidistant from two points, and a range of ±10% of the distance from the midpoint between the two points. The circumferential main groove is a circumferential groove having a wear indicator that indicates the end of wear, and generally has a groove width of 5.0 mm or more and a groove depth of 5.0 mm or more. The groove width and groove depth of the circumferential main groove are not limited to the above ranges. A sipe is a cut formed in a land portion, and generally has a groove width of less than 1.5 mm. The groove width is measured as the maximum distance between opposing groove walls at the groove opening on the tread surface when the tire is mounted on a specified rim, inflated to a specified internal pressure, and in an unloaded state. In the case of a configuration having a notch or chamfered portion at the groove opening, the groove width is measured using the intersection of an extension of the tread surface and an extension of the groove wall as the endpoint in a cross-sectional view parallel to the groove width direction and the groove depth direction. The groove depth is measured as the maximum distance from the tread surface to the groove bottom when the tire is mounted on a specified rim, inflated to a specified internal pressure, and in an unloaded state. If the groove in question has partial unevenness or sipes at the groove bottom, the groove depth shall be the value measured excluding the partial unevenness or sipes. The tread edge is the both ends of the tread pattern of the tire, also called the design end. The contact edge is the maximum position in the tire width direction of the contact surface between the tire and a flat plate when the tire is mounted on a specified rim, pressurized to a specified internal pressure, placed perpendicular to a flat plate in a stationary state, and subjected to a specified load (80% of the maximum load capacity).The length in the tire width direction along the tread surface between the contact edges is called the contact width. The length in the tire width direction along the tread surface from the tire equatorial plane to one of the contact edges is sometimes called the half contact width.

[0033] In the following explanation, "regular rim" refers to the "applicable rim" specified by JATMA, the "design rim" specified by TRA, or the "measuring rim" specified by ETRTO. Similarly, in the following explanation, "regular internal pressure" refers to the "maximum air pressure" specified by JATMA, the maximum value specified in "tire load limits at variable cold inflation pressures" specified by TRA, or the "inflation pressures" specified by ETRTO. Furthermore, "regular load" refers to the "maximum load capacity" specified by JATMA, the maximum value specified in "tire load limits at variable cold inflation pressures" specified by TRA, or the "load capacity" specified by ETRTO.

[0034] 1. First Embodiment (Tire Configuration) A first embodiment of the present invention will be described below with reference to the drawings. Fig. 1 is a diagram showing portions of a tire 10 according to the first embodiment on both sides in the tire width direction with the tire equatorial plane CP as the reference in a plan view seen from the outer side in the tire radial direction. Note that the drawing shows the tire portion in a state where the tire is mounted on a rim and pressurized to the normal internal pressure, and in an unloaded state.

[0035] Although not shown in its entirety, the tire 10 of this embodiment has a meridian cross-sectional shape similar to that of a conventional pneumatic tire. That is, the tire 10 of this embodiment has, from the inner side to the outer side in the tire radial direction in a tire meridian cross-sectional view, a bead portion, a sidewall portion, a shoulder portion, and a tread portion 12. The tire 10 has, for example, a carcass layer extending from the tread portion 12 to both bead portions in a tire meridian cross-sectional view and wound around a pair of bead cores, and a belt layer and, in some cases, a belt cover layer on the tire radial direction outer side of the carcass layer.

[0036] The rotation direction of the tire 10 is specified. The tire 10 is equipped with a rotation direction indicator (not shown) that indicates the tire rotation direction. The tire rotation direction refers to the rotation direction that is frequently used when the tire is in use, for example, the rotation direction when the vehicle is moving forward. Based on the display of this rotation direction indicator, the first-contact side of the block (so-called leading-in side or heel side) and the last-contact side (so-called trailing-out side or toe side) are defined (see FIG. 1). The leading-in side is the side that contacts the ground first when the tire rolls in the specified rotation direction, and the trailing-out side is the side opposite to the leading-in side. The rotation direction indicator is configured, for example, by marks or irregularities provided on the sidewall of the tire 10. The lower side in FIG. 1 is the leading-in side. The upper side in FIG. 1 is the trailing-out side.

[0037] The tread portion 12 is formed of a rubber material (tread rubber). The tread portion 12 has a tread surface 14 that comes into contact with the road surface when the vehicle is traveling. The tread surface 14 is annular, centered on the rotational axis of the tire 10, has a predetermined length in the tire width direction, and is continuous in the tire circumferential direction. A predetermined tread pattern is engraved on the tread surface 14. The tread pattern is asymmetric with respect to the tire equatorial plane CP, between both sides of the tire equatorial plane CP in the tire width direction. In FIG. 1 , the symbol EL indicates a contact edge line (a line connecting consecutive contact edges E in the tire circumferential direction). The distance between the tread edges T along the tire profile is designated as LDE.

[0038] As shown in FIG. 1 , a tire 10 according to the first embodiment includes two circumferential main grooves 16, an inner land portion 18, and an outer land portion 20 on a tread surface 14. The tire 10 includes a first circumferential main groove 22 on one side of the tire equatorial plane CP in the tire width direction and a second circumferential main groove 24 on the other side in the tire width direction. The first circumferential main groove 22 and the second circumferential main groove 24 extend in the tire circumferential direction. That is, the first circumferential main groove 22 and the second circumferential main groove 24 are preferably formed so that imaginary lines parallel to the tire circumferential direction can pass through the grooves. Therefore, at least a portion of water that flows into the first circumferential main groove 22 and the second circumferential main groove 24 can move linearly in the tire circumferential direction through the first circumferential main groove 22 and the second circumferential main groove 24. In the following description, unless otherwise specified, the first circumferential main groove 22 and the second circumferential main groove 24 will be referred to as the circumferential main groove 16.

[0039] The inner land portion 18 is defined by two circumferential main grooves 16. The inner land portion 18 has an outer edge in the tire width direction defined by the two circumferential main grooves 16 and a shape that is continuous in the tire circumferential direction. The inner land portion 18 according to this embodiment is disposed at a position where its center in the tire width direction overlaps with the tire equatorial plane CP. The length of the inner land portion 18 in the tire width direction along the tire profile is defined as Wce.

[0040] The inner land portion 18 may have a circumferential narrow groove 26 extending in the tire circumferential direction. The circumferential narrow groove 26 extends in a direction along the tire circumferential direction. The circumferential narrow groove 26 has a groove width that is 20% to 60% of the groove width Wm of the circumferential main groove 16, and a groove depth that is 5% to 50% of the groove depth Dm of the circumferential main groove 16. The circumferential narrow groove 26 may be disposed at a position that overlaps with the tire equatorial plane CP.

[0041] The inner land portion 18 has an inner inclined groove 28 and an inner sipe 30. The inner inclined groove 28 extends inward in the tire width direction from the circumferential main groove 16 and is inclined from the trailing edge to the leading edge. One end 32 of the inner inclined groove 28 is connected to the circumferential main groove 16, and the other end 34 is located within the inner land portion 18. The inner inclined groove 28 shown in FIG. 1 has a tapered shape in which the groove width gradually decreases from the one end 32 to the other end 34. The inner inclined groove 28 preferably has a groove width of 5% to 125% of the groove width Wm of the circumferential main groove 16. The groove width of the inner inclined groove 28 is the average value of the groove width at the one end 32 and the groove width at the other end 34.

[0042] The inner inclined grooves 28 include a first inner inclined groove 36 and a second inner inclined groove 38. The first inner inclined groove 36 extends inward in the tire width direction from the circumferential main groove 16, inclined from the trailing edge to the leading edge, and intersects with the tire equatorial plane CP. The other end 34f of the first inner inclined groove 36 is disposed between the circumferential main groove 16 opposite the connected circumferential main groove 16 and the tire equatorial plane CP. The second inner inclined groove 38 extends inward in the tire width direction from the circumferential main groove 16, inclined from the trailing edge to the leading edge, and does not intersect with the tire equatorial plane CP. The other end 34s of the second inner inclined groove 38 is disposed between the connected circumferential main groove 16 and the tire equatorial plane CP.

[0043] In this embodiment, the first inner inclined grooves 36 and the second inner inclined grooves 38 are arranged alternately in the tire circumferential direction. The first inner inclined grooves 36 and the second inner inclined grooves 38 are arranged on both sides of the tire equatorial plane CP. That is, in the tire 10 shown in FIG. 1 , the first inner inclined groove 36 and the second inner inclined groove 38 are arranged in this order from the trailing edge to the leading edge on the first circumferential main groove 22 side, and the second inner inclined groove 38 and the first inner inclined groove 36 are arranged in this order from the trailing edge to the leading edge on the second circumferential main groove 24 side. The first inner inclined groove 36 and the second inner inclined groove 38 are arranged in positions facing each other with respect to the tire equatorial plane CP.

[0044] As shown in FIG. 2 , the first inner inclined groove 36 may have a first inclined portion 40, a second inclined portion 42, and a bent portion 44. The first inclined portion 40 and the second inclined portion 42 are connected via the bent portion 44. The extending directions of the first inclined portion 40 and the second inclined portion 42 change at the bent portion 44. One end 32 of the first inclined portion 40 is connected to the circumferential main groove 16. The other end of the first inclined portion 40 is connected to the bent portion 44. One end 34f of the second inclined portion 42 is disposed between the tire equatorial plane CP and the circumferential main groove 16 opposite to the connected circumferential main groove 16.

[0045] The angle between the extension direction of the first inclined portion 40 and the tire circumferential direction is defined as θa. The extension direction of the first inclined portion 40 is defined as the extension direction of an imaginary line connecting the midpoint of the groove width at one end 32 of the first inclined portion 40 to the midpoint of the groove width at the other end 34f. The angle between the extension direction of the second inclined portion 42 and the tire circumferential direction is defined as θb. The extension direction of the second inclined portion 42 is defined as the extension direction of an imaginary line connecting the midpoint of the groove width at one end 34f of the second inclined portion 42 connected to the bent portion 44 to the midpoint of the groove width at the other end 34f.

[0046] As shown in FIG. 3 , the first groove depth D1 , which is the groove depth of the inner inclined groove 28 , is preferably 30% to 80% of the groove depth Dm of the circumferential main groove 16 .

[0047] Each of the inner sipes 30 has a tip 31 on the outer side in the tire width direction connected to each of the circumferential main grooves 16. The inner sipes 30 may have a zigzag shape that inclines alternately to each side in the tire circumferential direction. The angle between the extension direction of the inner sipes 30 and the tire width direction is ±20° or less, 15° or less, or 10° or less. The extension direction of the inner sipes 30 is the direction of an imaginary line connecting each of the tips 31 connected to the circumferential main grooves 16.

[0048] The outer land portion 20 ( FIG. 1 ) is adjacent to the inner land portion 18 on the outer side in the tire width direction, with two circumferential main grooves 16 sandwiched between them. The outer land portion 20 has a plurality of inclined grooves 50, inclined narrow grooves 52, and reverse inclined grooves 54. The outer land portion 20 is defined into a plurality of blocks 56 by the plurality of inclined grooves 50, inclined narrow grooves 52, and reverse inclined grooves 54.

[0049] The inclined groove 50 extends from the circumferential main groove 16 toward the outside in the tire width direction and is inclined from the leading side to the trailing side. A plurality of inclined grooves 50 are arranged at predetermined intervals in the tire circumferential direction. A tip 58 of the inclined groove 50 on the inside in the tire width direction is connected to the circumferential main groove 16, and a tip 60 on the outside in the tire width direction is connected to the tread edge T. The inclined groove 50 may extend in the direction along the tire width direction in a range from the ground contact edge E to the outside in the tire width direction. The inclined groove 50 is preferably arranged on an extension line of the inner inclined groove 28.

[0050] As shown in Figure 4, the opening width of a tip 58 of the inclined groove 50 connected to the circumferential main groove 16 is defined as Wa. The opening width Wa is the distance between the end points where the groove wall 16w of the circumferential main groove 16 intersects with the groove wall 50w of the inclined groove 50. The opening width of a tip 60 of the inclined groove 50 connected to the tread edge T is defined as Wb. The opening width Wb is the distance between the end points where the tread edge T intersects with the groove wall 50w of the inclined groove 50. When the tips 58, 60 of the inclined groove 50 have chamfered portions, the opening widths Wa, Wb are the distances between the end points where an extension line of the groove wall 50w of the inclined groove 50 intersects with an extension line of the groove wall 16w of the circumferential main groove 16 or the tread edge T. The groove width of the inclined groove 50 shown in Figure 4 gradually increases from the inner side in the tire width direction to the outer side in the tire width direction. The groove width W1 of the inclined groove 50 is preferably 70% to 120% and more preferably 80% to 110% of the groove width Wm of the circumferential main groove 16. The groove width W1 of the inclined groove 50 is the average value of the opening width Wa and the opening width Wb.

[0051] As shown in FIG. 5 , the inclined groove 50 has a main inclined portion 62 and a bottom-up portion 64. The main inclined portion 62 has a second groove depth D2. The second groove depth D2 is 50% or more and 120% or less of the groove depth Dm of the circumferential main groove 16. The bottom-up portion 64 is disposed between an inner tip 66 of the main inclined portion 62 in the tire width direction and a groove wall 16w of the circumferential main groove 16. The bottom-up portion 64 has a third groove depth D3. The third groove depth D3 is shallower than the second groove depth D2. The third groove depth D3 is 15% or more and 70% or less of the second groove depth D2. The tire width direction length of the bottom-up portion 64 is preferably 3 mm or more and 15 mm or less, and more preferably 5 mm or more and 10 mm or less.

[0052] The raised bottom portion 64 shown in Figure 5 extends from a tip 66 on the inner side in the tire width direction of the main inclined portion 62 toward the circumferential main groove 16. The raised bottom portion 64 is connected to the circumferential main groove 16. The raised bottom portion 64 has an inclined surface 68 and a flat surface 70. The inclined surface 68 extends from the tip 66 on the inner side in the tire width direction of the main inclined portion 62 toward the circumferential main groove 16 and is inclined outward in the tire radial direction. The flat surface 70 extends from a tip 72 on the inner side in the tire width direction of the inclined surface 68 toward the circumferential main groove 16 in a direction along the tread surface 14.

[0053] The inclined narrow grooves 52 extend from the circumferential main groove 16 toward the outside in the tire width direction and are inclined from the leading-in side to the trailing-out side in the tire circumferential direction ( FIG. 4 ). A plurality of inclined narrow grooves 52 are arranged at predetermined intervals in the tire circumferential direction. The inner tip 74 of the inclined narrow groove 52 in the tire width direction is connected to the circumferential main groove 16, and the outer tip 76 in the tire width direction is arranged in the outer land portion 20. The inclined narrow grooves 52 are preferably arranged on an extension line of the inner inclined groove 28. The inclined narrow grooves 52 and the inclined grooves 50 according to this embodiment are arranged alternately in the tire circumferential direction.

[0054] The groove width W2 of the inclined narrow groove 52 is preferably 20% to 80% of the groove width W1 of the inclined groove 50, and more preferably 35% to 55%.

[0055] The groove width W2 of the inclined narrow groove 52 is preferably 5% to 25% of the block width W4, and more preferably 10% to 20%. The block width W4 refers to the widthwise length of the block 56c adjacent to the circumferential main groove 16. The widthwise length of the block 56c is measured as follows. First, the intersection of an extension of the groove wall 50w of the inclined groove 50 on the trailing edge of the target block 56c and an extension of the groove wall 16w of the circumferential main groove 16 is defined as a first endpoint P1. Next, the intersection of a line drawn from the first endpoint P1 and perpendicular to the trailing edge groove wall 50w of the block 56c with the leading edge groove wall 50w of the block 56c is defined as a second endpoint P2. The distance between the first endpoint P1 and the second endpoint P2 is defined as the block width W4.

[0056] The inclined narrow groove 52 has a groove bottom sipe 78. As shown in Fig. 6 , the groove bottom sipe 78 is formed at the groove bottom 52u of the inclined narrow groove 52. That is, the groove bottom sipe 78 is a groove that has an opening 78t at the groove bottom 52u of the inclined narrow groove 52 and a bottom surface 78b on the inner side in the tire radial direction, and extends in a direction along the inclined narrow groove 52.

[0057] The groove depth of the inclined narrow groove 52 is Dg, and the groove depth of the groove bottom sipe 78 is Ds. The groove depth Dg of the inclined narrow groove 52 is preferably 20% to 60% of the groove depth Dm of the circumferential main groove 16, and more preferably 30% to 50%. The inclined narrow groove 52 is arranged along the inclined groove 50. The groove bottom sipe 78 is arranged at the center of the inclined narrow groove 52 in the groove width direction.

[0058] The groove bottom sipes 78 are preferably shorter than the groove length of the inclined narrow grooves 52 and do not communicate with the reverse inclined grooves 54 ( FIG. 4 ). That is, the length of the groove bottom sipes 78 is defined as Ls, and the groove length of the inclined narrow grooves 52 is defined as Lg. The length Ls of the groove bottom sipes 78 is the length in a direction perpendicular to the groove width direction and groove depth direction of the groove bottom sipes 78. The groove length Lg of the inclined narrow grooves 52 is defined as the distance between the midpoints of the groove widths at the tips 74, 76 of the inclined narrow grooves 52 that connect to the reverse inclined grooves 54, when targeting the inclined narrow grooves 52 provided in a certain block 56 defined by reverse inclined grooves 54 on both sides in the tire width direction. In this case, the groove length Ls of the groove bottom sipes 78 is preferably 0.75 or more ≦(Ls / Lg)≦0.95.

[0059] The reverse inclined grooves 54 extend from the trailing edge toward the leading edge in the tire circumferential direction and are inclined from the inner side to the outer side in the tire width direction ( FIG. 4 ). Preferably, there are two to four reverse inclined grooves 54 on each side of the tire equatorial plane CP. Although not shown, the inner and outer ends of the reverse inclined grooves 54 in the tire width direction are located within the outer land portion 20. The reverse inclined grooves 54 intersect with the inclined grooves 50 and the inclined narrow grooves 52. The groove width W3 of the reverse inclined groove 54 is preferably 30% to 90% of the groove width Wm of the circumferential main groove 16, and more preferably 40% to 60%.

[0060] The angle θc between the extension direction of the reverse inclined groove 54 and the tire circumferential direction is preferably 5° to 50°, and more preferably 10° to 30° ( FIG. 1 ). The angle θc between the extension direction of the reverse inclined groove 54 and the tire circumferential direction may be specified for each block. That is, the angle θc between the extension direction of the reverse inclined groove 54 and the tire circumferential direction is the angle between the tire circumferential direction and a first imaginary line L1 connecting the midpoint of the groove width at the trailing-side end and the midpoint of the groove width at the leading-side end of the reverse inclined groove 54 in each block 56.

[0061] As shown in FIG. 7, the fourth groove depth D4, which is the groove depth of the reverse inclined groove 54, is preferably 40% or more and 80% or less of the groove depth Dm of the circumferential main groove 16, and more preferably 50% or more and 70% or less.

[0062] Each of the multiple blocks 56 has an outer sipe 84 ( FIG. 4 ). Preferably, one or two outer sipes 84 are provided in each block 56. Preferably, one or two outer sipes 84 are provided in each block 56, on both sides of the inclined narrow groove 52 in the tire circumferential direction. The outer sipes 84 may have a zigzag shape that alternately inclines toward each side in the tire circumferential direction. The angle θd between the extension direction of the outer sipe 84 and the extension direction of the inclined narrow groove 52 is ±20° or less, ±15° or less, or ±10° or less. The extension direction of the outer sipe 84 is the direction of an imaginary line connecting the inner end and the outer end in the tire width direction. The extension direction of the inclined narrow groove 52 is the direction of an imaginary line connecting the midpoint of the groove width at the inner end in the tire width direction within the block 56 in which the outer sipe 84 is formed and the midpoint of the groove width at the outer end in the tire width direction.

[0063] The outer land portion 20 has an outermost block 56s arranged on the outermost side in the tire width direction. The outermost block 56s has an outer edge in the tire circumferential direction defined by the inclined grooves 50, an outer edge on the inner side in the tire width direction defined by the reverse inclined grooves 54, and an inclined narrow groove 52 in the tire circumferential center.

[0064] The outermost block 56s is provided with a tip 76 of the inclined narrow groove 52 on the outer side in the tire width direction. The outermost block 56s has a recess 86. The recess 86 is provided on the outer side in the tire width direction of the outermost tip 76 of the inclined narrow groove 52 on the outer side in the tire width direction. It is preferable that at least a portion of the recess 86 is provided in a region on the outer side in the tire width direction of the ground contact edge E.

[0065] In this embodiment, the recessed portion 86 is rectangular. A total of six recessed portions 86 are arranged in each outermost block 56s, including multiple recessed portions 86 arranged in the tire circumferential direction (three in the case of FIG. 4 ) and multiple recessed portions 86 arranged in the tire width direction (two in the case of FIG. 4 ). The recessed portions 86 provided in each outermost block 56s have different tire circumferential lengths. In this embodiment, the tire circumferential length gradually increases from the trailing edge to the leading edge. The recessed portion 86 has an edge 86e extending in a direction intersecting the tire circumferential direction. The depth D5 of the recessed portion 86 shown in FIG. 8 is 0.5 mm or more and 3.0 mm or less. Multiple edges 86e are arranged in the tire circumferential direction.

[0066] The angle θa formed between the extension direction of the first inclined portion 40 and the tire circumferential direction is preferably smaller than the angle θb formed between the extension direction of the second inclined portion 42 and the tire circumferential direction. Specifically, the angle θa formed between the extension direction of the first inclined portion 40 and the tire circumferential direction is preferably 30° or more and 70° or less, and the angle θa and the angle θb formed between the extension direction of the second inclined portion 42 and the tire circumferential direction preferably satisfy the following formula (1):

[0067] θa+5°≦θb≦90°...(1)

[0068] When the distance LDE between the tread ends T in the tire width direction and the length Wce of the inner land portion 18 in the tire width direction are taken as LDE and Wce, respectively, it is preferable that the following formula (2) be satisfied.

[0069] 0.08≦Wce / LDE≦0.20...Formula (2)

[0070] It is preferable that the groove width Wa of the tip 58 of the inclined groove 50 connecting to the circumferential main groove 16 and the groove width Wb of the tip 60 of the inclined groove 50 at the tread edge T satisfy the following formula (3).

[0071] 0.3≦Wa / Wb≦0.8 (3) It is preferable that the groove depth Dg of the inclined narrow groove 52 and the groove depth Ds of the groove bottom sipe 78 satisfy the following formula (4).

[0072] 0.7≦Ds / Dg≦1.3...Formula (4)

[0073] The tire 10 of this embodiment described above is obtained through each of the usual manufacturing steps, i.e., a tire material mixing step, a tire material processing step, a green tire molding step, a vulcanization step, and a post-vulcanization inspection step, etc. When manufacturing the tire of this embodiment, convex portions and concave portions corresponding to a predetermined tread pattern are formed on the inner wall of a vulcanization mold, and vulcanization is carried out using this mold.

[0074] (Operations and Effects) The tire 10 according to this embodiment includes a circumferential main groove 16, an inner land portion 18 defined by the two circumferential main grooves 16, and outer land portions 20 disposed on the outer side of the inner land portion 18 in the tire width direction, with the circumferential main groove 16 sandwiched between them. The tire also includes an inclined groove 50, an inclined narrow groove 52, and a reverse inclined groove 54 disposed in the outer land portion 20. The inclined groove 50 is inclined from the leading edge to the trailing edge in the tire circumferential direction, and its tip 60 connects to the tread edge T. The inclined narrow groove 52 extends from the circumferential main groove 16 toward the outer side in the tire width direction, and is inclined from the leading edge to the trailing edge in the tire circumferential direction. The reverse inclined groove 54 extends from the trailing edge to the leading edge in the tire circumferential direction, and is inclined from the inner side to the outer side in the tire width direction.

[0075] On snowy roads, the tire 10 compacts snow that has entered the grooves. When driving force, braking force, or lateral force during cornering acts on the tire in this state, so-called snow column shear force is generated on the snow in the grooves. The tire 10 has circumferential main grooves 16, inclined grooves 50, inclined narrow grooves 52, and reverse inclined grooves 54, which allows it to exert excellent snow column shear force and provide excellent drainage. This gives the tire 10 excellent snow and wet performance.

[0076] The outer tip 76 of the inclined narrow groove 52 in the tire width direction is disposed within the outermost block 56s. This prevents a decrease in the rigidity of the outermost block 56s. The groove width W2 of the inclined narrow groove 52 is 20% to 80% of the groove width W1 of the inclined groove 50, which prevents a decrease in the rigidity of the outer land portion 20. This provides the tire 10 with excellent dry performance.

[0077] As a result, the tire 10 has excellent snow performance, wet performance, and dry performance.

[0078] By providing two or more reverse inclined grooves 54 on each side of the tire width direction relative to the tire equatorial plane CP, the tire 10 has excellent snow performance and wet performance. By providing four or fewer reverse inclined grooves 54, the reduction in rigidity of each block 56 is suppressed. Therefore, the tire 10 has excellent dry performance.

[0079] By making the groove width W2 of the inclined narrow groove 52 5% or more of the block width W4, snow column shear force can be more reliably exerted. By making the groove width W2 of the inclined narrow groove 52 25% or less of the block width W4, a sufficient ground contact area can be secured. Therefore, the tire 10 can suppress a decrease in dry performance.

[0080] When the angle θc between the extension direction of the reverse inclined grooves 54 and the tire circumferential direction is 5° or more, the tire 10 can more reliably exert snow shear force during driving or braking. When the angle θc is 50° or less, the tire 10 can more reliably exert snow column shear force during cornering.

[0081] The inclined groove 50 has the bottom-raised portion 64, which can suppress a decrease in rigidity on the inner side in the tire width direction of the outer land portion 20. The tire 10 has excellent dry performance because a decrease in rigidity on the inner side in the tire width direction where the ground contact pressure is higher is suppressed.

[0082] The first inner inclined grooves 36 intersect with the tire equatorial plane CP, and are therefore formed in an area with higher ground contact pressure, thereby more reliably exerting snow column shear force. The inner ends of the second inner inclined grooves 38 in the tire width direction are positioned between the connected circumferential main grooves 16 and the tire equatorial plane CP, thereby maintaining the rigidity of the inner land portion 18. Therefore, by including the first inner inclined grooves 36 and the second inner inclined grooves 38, the tire 10 has excellent snow and dry performance.

[0083] The first inner inclined groove 36 has a first inclined portion 40, a second inclined portion 42, and a bent portion 44. The extending directions of the first inclined portion 40 and the second inclined portion 42 change at the bent portion 44. The first inner inclined groove 36 has the bent portion 44, thereby ensuring the groove length and groove area. This allows the first inner inclined groove 36 to receive more snow, allowing the tire 10 to more reliably exert snow column shear force.

[0084] The angle θa between the extension direction of the first inclined portion 40 and the tire circumferential direction is smaller than the angle θb between the extension direction of the second inclined portion 42 and the tire circumferential direction, so that the bent portion 44 has a shape that is convex toward the leading edge. By having the bent portion 44 that is convex toward the leading edge, the tire 10 can more reliably exert snow column shear force during driving.

[0085] The angle θa between the extension direction of the first inclined portion 40 and the tire circumferential direction is greater than or equal to 30° and less than or equal to 70°, and the angle θa and the angle θb between the extension direction of the second inclined portion 42 and the tire circumferential direction satisfy the above formula (1), thereby allowing the tire 10 to more reliably exert snow column shear force when driven.

[0086] The first groove depth D1 of the inner inclined groove 28 is 30% or more of the groove depth Dm of the circumferential main groove 16, thereby making it possible to more reliably exert snow column shear force. The first groove depth D1 of the inner inclined groove 28 is 80% or less of the groove depth Dm of the circumferential main groove 16, thereby making it possible to suppress a decrease in the rigidity of the inner land portion 18 of the tire 10.

[0087] By arranging the inclined grooves 50 or the inclined narrow grooves 52 on the extension lines of the inner inclined grooves 28, water can easily flow from the inner inclined grooves 28 on the inner side in the tire width direction to the outer side in the tire width direction through the inclined grooves 50 or the inclined narrow grooves 52. Therefore, the tire 10 has improved drainage and excellent wet performance.

[0088] The distance LDE in the tire width direction between the tread edges T and the length Wce in the tire width direction of the inner land portion 18 satisfy the above formula (2). The tire 10 obtains excellent dry performance when the relationship between the distance LDE and the length Wce is equal to or greater than the lower limit of the above formula (2). The tire 10 obtains excellent snow performance when the relationship between the distance LDE and the length Wce is equal to or less than the upper limit of the above formula (2).

[0089] The groove width Wa of the tip 58 of the inclined groove 50 connecting to the circumferential main groove 16 and the groove width Wb of the tip 60 of the inclined groove 50 at the tread edge T satisfy the above formula (3). When the relationship between the groove width Wa and the groove width Wb is within the range of the above formula (3), the tire 10 can obtain the desired rigidity on the inner side in the tire width direction, and can obtain excellent snow column shear force by ensuring the groove area on the outer side in the tire width direction.

[0090] The tire 10 can more reliably exert snow column shear force by making the groove depth Dg of the inclined narrow groove 52 20% or more of the groove depth Dm of the circumferential main groove 16. The tire 10 can suppress a decrease in block rigidity by making the groove depth Dg of the inclined narrow groove 52 60% or less of the groove depth Dm of the circumferential main groove 16.

[0091] Because the inclined narrow groove 52 has the groove bottom sipe 78, the cross-sectional area of ​​the groove is larger than that of an inclined narrow groove having the same groove width and groove depth without the groove bottom sipe 78, so the tire 10 can improve its snow performance and wet performance while suppressing a decrease in block rigidity.

[0092] The groove depth Dg of the inclined narrow groove 52 and the groove depth Ds of the groove bottom sipe 78 satisfy the above formula (4). In the tire 10, the relationship between the groove depth Dg and the groove depth Ds is equal to or greater than the lower limit of the above formula (4), so that the proportion of the groove bottom sipe 78 is equal to or greater than a certain value, i.e., the cross-sectional area of ​​the inclined narrow groove 52 is equal to or less than a predetermined size, thereby suppressing a decrease in block rigidity and providing excellent dry performance. In the tire 10, the relationship between the groove depth Dg and the groove depth Ds is equal to or less than the upper limit of the above formula (4), so that the proportion of the groove bottom sipe 78 is equal to or less than a certain value, i.e., the cross-sectional area of ​​the inclined narrow groove 52 is equal to or greater than a predetermined size, thereby providing excellent wet and snow performance.

[0093] The groove depth D4 of the reverse oblique groove 54 is 40% or more of the groove depth Dm of the circumferential main groove 16, thereby enabling the snow column shear force to be exerted more reliably. The groove depth D4 of the reverse oblique groove 54 is 80% or less of the groove depth Dm of the circumferential main groove 16, thereby suppressing a decrease in block rigidity of the tire 10 and providing excellent dry performance.

[0094] Some of the multiple blocks 56 in the outer land portion 20 have outer sipes 84, which deform when the tire is stepped on so that the groove walls come into contact with each other, and one edge of the outer sipes 84 comes into contact with the road surface. This allows the tire 10 to achieve excellent snow performance. By providing each block 56 with two or fewer outer sipes 84, it is possible to prevent a decrease in the rigidity of the block 56. Because the outer sipes 84 extend along the inclined narrow grooves 52, the blocks 56 in which the outer sipes 84 are formed are more likely to deform in the direction that widens the groove width of the inclined narrow grooves 52 when the tire is stepped on, thereby more reliably exerting snow column shear force.

[0095] The inner sipes 30 extend along the tire width direction, and therefore, the inner land portion 18 deforms during driving and braking, forming edges on the inner sipes 30. Therefore, the tire 10 has excellent driving and braking performance on snow.

[0096] The recesses 86 are positioned outward in the tire width direction from the tips 76 of the inclined narrow grooves 52, and have multiple edges 86e that intersect in the tire circumferential direction, thereby achieving the effect of shoveling snow when driving on snow. By setting the depth D5 of the recesses 86 to 0.5 mm or more, the snow-shoveling effect is more reliably achieved. By setting the depth D5 of the recesses 86 to 3.0 mm or less, a decrease in rigidity of the outer land portion 20, particularly at the outer side in the tire width direction, is suppressed, and a decrease in cornering performance is suppressed.

[0097] 2. Second Embodiment A second embodiment of the present invention will be described with reference to Fig. 9, in which the same components as those in Fig. 1 are designated by the same reference numerals. Fig. 9 is a diagram showing portions of a tire 10A according to the second embodiment on both sides in the tire width direction with the tire equatorial plane CP as the reference, in a plan view seen from the outer side in the tire radial direction. Note that Fig. 9 shows the tire portion in a state where the tire is mounted on a rim, has a normal internal pressure applied, and is in an unloaded state.

[0098] The tire 10A according to the second embodiment has two circumferential main grooves 16, an inner land portion 18, and an outer land portion 20 on a tread surface 14. The outer land portion 20 is adjacent to the inner land portion 18 on the outer side in the tire width direction, with the two circumferential main grooves 16 sandwiched between them. The outer land portion 20 has an inclined groove 50, an inclined narrow groove 52, and a reverse inclined groove 54. The outer land portion 20 has a plurality of blocks 56 defined by the inclined grooves 50, the inclined narrow grooves 52, and the reverse inclined grooves 54.

[0099] Furthermore, the tire 10A shown in Figure 9 has a circumferential narrow groove 88 in the outer land portion 20. The circumferential narrow groove 88 is continuous in the tire circumferential direction and intersects with the oblique grooves 50 and the oblique narrow grooves 52. The groove width Wsub of the circumferential narrow groove 88 is preferably 15% to 70% of the groove width Wm of the circumferential main groove, and more preferably 20% to 50%. The groove depth Dsub of the circumferential narrow groove 88 is preferably 10% to 60% of the groove depth Dm of the circumferential main groove, and more preferably 15% to 50%.

[0100] The circumferential narrow grooves 88 are arranged in an outer region SH in the tire width direction of the outer land portion 20. The outer region SH is a region that is continuous in the tire circumferential direction, and refers to a range of 0.05 × Wh (mm) or more and 0.15 Wh (mm) or less from the tire contact edge E to the inner side in the tire width direction, where Wh is the distance in the tire width direction along the tire profile from the tire equatorial plane CP to the tire contact edge E.

[0101] 9, a line extending from the ground edge E inward in the tire width direction and parallel to the ground edge line EL at a position 5% of half the ground edge width Wh is defined as a second imaginary line L2. A line extending from the ground edge E inward in the tire width direction and parallel to the ground edge line EL at a position 15% of half the ground edge width Wh is defined as a third imaginary line L3. The outer region SH is the range between the second imaginary line L2 and the third imaginary line L3.

[0102] The tire 10A has excellent wet and snow performance because the circumferential narrow grooves 88 are arranged from a position 0.05 × Wh (mm) inward in the tire width direction from the ground contact edge E to the inner side in the tire width direction, which improves drainage and provides snow column shear force during cornering. The tire 10A has excellent dry performance because the circumferential narrow grooves 88 are arranged from a position 0.15 Wh (mm) inward in the tire width direction from the ground contact edge E to the outer side in the tire width direction, which prevents a decrease in rigidity of the outer land portion 20.

[0103] Preferably, two circumferential narrow grooves 88 are formed in the outer regions SH on each side of the tire equatorial plane CP. That is, the tire 10A preferably has an outer narrow groove 90 and an inner narrow groove 92 in the outer regions SH on each side of the tire equatorial plane CP in the tire width direction. The outer narrow groove 90 is disposed on the outer side in the tire width direction. The inner narrow groove 92 is disposed on the inner side of the outer narrow groove 90 in the tire width direction.

[0104] 10 and 11, the groove width of the outer narrow groove 90 is Wout, and the groove depth of the outer narrow groove 90 is Dout. The groove width of the inner narrow groove 92 is Win, and the groove depth of the inner narrow groove 92 is Din.

[0105] The groove width Wout of the outer narrow groove 90 is preferably smaller than the groove width Win of the inner narrow groove 92. A smaller groove width Wout of the outer narrow groove 90 can suppress a decrease in block rigidity near the tread edge E and suppress a decrease in dry performance. Specifically, the groove width Wout of the outer narrow groove 90 and the groove width Win of the inner narrow groove 92 preferably satisfy the following formula (5).

[0106] 0.3≦Wout / Win≦0.7...Formula (5)

[0107] The groove depth Dout of the outer narrow groove 90 is preferably shallower than the groove depth Din of the inner narrow groove 92. A smaller groove depth Dout of the outer narrow groove 90 suppresses a decrease in block rigidity near the tread edge E, resulting in excellent dry performance. Specifically, the groove depth Dout of the outer narrow groove 90 and the groove depth Din of the inner narrow groove 92 preferably satisfy the following formula (6):

[0108] 0.4≦Dout / Din≦0.8...Formula (6)

[0109] (Modifications) The present invention is not limited to the above-described embodiment, and can be modified as appropriate within the scope of the invention.

[0110] For example, in the above embodiment, the tire 10 has been described as having the raised bottom portion 64 in the inclined groove 50, but the present invention is not limited to this, and the raised bottom portion 64 may not be included. The raised bottom portion 64 is connected to the circumferential main groove 16, but the present invention is not limited to this. As shown in FIG. 12 , a deep groove portion 94 may be included between the raised bottom portion 64 and the circumferential main groove 16. The groove depth of the deep groove portion 94 may be the same as the second groove depth D2 of the main inclined portion 62. Furthermore, the raised bottom portion 64 is not limited to having an inclined surface 68 and a flat surface 70, and may not have the flat surface 70. The raised bottom portion 64 may not have an inclined surface 68.

[0111] Although the case where the inner inclined groove 28 has a first inner inclined groove 36 and a second inner inclined groove 38 and the second inner inclined groove 38 does not intersect with the tire equatorial plane CP has been described, the present invention is not limited to this. For example, as shown in Fig. 13, the inner inclined groove 28 may have the first inner inclined groove 36 and the second inner inclined groove 38 each extending inward in the tire width direction from the circumferential main groove 16, inclining from the trailing edge to the leading edge, and intersecting with the tire equatorial plane CP.

[0112] Although the first inner oblique grooves 36 and the second inner oblique grooves 38 are described as being alternately arranged in the tire circumferential direction, the present invention is not limited to this. A plurality of first inner oblique grooves 36 may be arranged consecutively in the tire circumferential direction. Furthermore, a plurality of second inner oblique grooves 38 may be arranged consecutively in the tire circumferential direction. Furthermore, as shown in FIG. 14 , the first inner oblique grooves 36 and the second inner oblique grooves 38 may intersect with each other at the tire equatorial plane.

[0113] Although the first inner inclined groove 36 has been described as having the first inclined portion 40, the second inclined portion 42, and the bent portion 44, the present invention is not limited to this. The first inner inclined groove 36 may not have the bent portion 44 and may intersect with the tire equatorial plane.

[0114] Although the angle θa between the extension direction of the first inclined portion 40 and the tire circumferential direction is smaller than the angle θb between the extension direction of the second inclined portion 42 and the tire circumferential direction in the above description, the present invention is not limited to this. For example, as shown in Fig. 15, the tire 10 may have a bent portion 44A in which the angle θa is larger than the angle θb, i.e., the bent portion 44A is convex toward the trailing edge. This allows the tire 10 to more reliably exert snow column shear force during braking.

[0115] It is preferable that the groove bottom sipes 78 do not communicate with the circumferential main groove 16. As shown in Fig. 16, the groove depth Dg of the inclined narrow groove 52 is preferably shallower than the groove depth Dm of the circumferential main groove 16. In this case, the inner tip 78ce of the groove bottom sipe 78 in the tire width direction is disposed within the inclined narrow groove 52. That is, the groove bottom 52u of the inclined narrow groove 52 is disposed between the inner tip 78ce of the groove bottom sipe 78 in the tire width direction and the groove wall 16w of the circumferential main groove 16. This enables the tire 10 to suppress a decrease in tread rigidity in the vicinity of the tire equatorial plane CP.

[0116] In the above embodiment, the tread pattern is asymmetric with respect to the tire equatorial plane CP, but the present invention is not limited to this, and the tread pattern may be symmetric with respect to the tire equatorial plane CP.

[0117] The inner land portion 18 is not limited to being disposed at a position where its center in the tire width direction overlaps with the tire equatorial plane CP, but may be disposed at a position where its center in the tire width direction is away from the tire equatorial plane CP to one or the other side in the tire width direction. The inner land portion 18 may be disposed at a position where it does not overlap with the tire equatorial plane CP.

[0118] The number of circumferential main grooves 16 is not limited to two, but may be three or more. When three or more circumferential main grooves 16 are included, the land portion closest to the tire equatorial plane CP or including the tire equatorial plane CP is defined as the inner land portion 18.

[0119] The inclined groove 50 is not limited to a groove width that gradually increases from Wa to Wb from the inner side in the tire width direction to the outer side in the tire width direction. For example, the inclined groove 50 may have a portion where the groove width gradually increases and a portion where the groove width gradually decreases from the inner side in the tire width direction to the outer side in the tire width direction. The inclined groove 50 may include, at any position between the tip on the inner side in the tire width direction and the tip on the outer side in the tire width direction, a portion whose groove width is smaller than the groove width of the inclined groove 50 located on the inner side in the tire width direction.

[0120] The inner land portion 18 is not limited to a case in which it has a circumferential narrow groove 26 extending in the tire circumferential direction, and may not have the circumferential narrow groove 26 .

[0121] Although the case where two circumferential narrow grooves 88 are formed in each of the outer regions SH on each side in the tire width direction has been described, the present invention is not limited to this. One circumferential narrow groove 88 may be formed in each of the outer regions SH on each side in the tire width direction, or three or more circumferential narrow grooves 88 may be formed. When there are three or more circumferential narrow grooves 88, the groove arranged on the outermost side in the tire width direction in the outer region SH is referred to as the outer narrow groove 90, and the groove arranged on the innermost side in the tire width direction in the outer region SH is referred to as the inner narrow groove 92.

[0122] The inner land portion 18 is not limited to having the inner inclined groove 28 and the inner sipe 30, and may include either one of them, or may not include both.

[0123] The inner sipes 30 are not limited to being zigzag slanted alternately to each side in the tire circumferential direction, but may also be linear. The outer sipes 84 are not limited to being zigzag slanted alternately to each side in the tire circumferential direction, but may also be linear.

[0124] The inclined grooves 50 and the inclined narrow grooves 52 are not limited to being arranged alternately in the tire circumferential direction, but may be arranged such that, for example, a plurality of inclined grooves 50 are continuously arranged in the tire circumferential direction. Alternatively, a plurality of inclined narrow grooves 52 are continuously arranged in the tire circumferential direction.

[0125] The inclined narrow groove 52 is not limited to having the groove bottom sipe 78. The inclined narrow groove 52 does not have to have the groove bottom sipe 78.

[0126] At least a portion of the recessed portion 86 is not limited to being disposed in a region on the outer side of the ground contact edge E in the tire width direction. The recessed portion 86 may be disposed in a region on the inner side of the ground contact edge E in the tire width direction.

[0127] The angle formed between the extension direction of the reverse inclined groove 54 and the tire circumferential direction may be less than 5° or may be greater than 50°.

[0128] The angle θa formed between the extension direction of the first inclined portion 40 and the tire circumferential direction may be less than 30° or may be greater than 70°.

[0129] The inclined groove 50 or the inclined narrow groove 52 is not limited to being arranged on the extension line of the inner inclined groove 28, but may also be arranged between the extension lines of multiple inner inclined grooves 28 arranged in the circumferential direction of the tire.

[0130] The groove depth D1 of the inner inclined groove 28 may be the same as the groove depth Dm of the circumferential main groove 16. The groove depth D1 of the inclined groove 50 may be the same as the groove depth Dm of the circumferential main groove 16. The groove depth Dg of the inclined narrow groove 52 may be the same as the groove depth Dm of the circumferential main groove 16. The groove depth D4 of the reverse inclined groove 54 may be the same as the groove depth Dm of the circumferential main groove 16. The groove depth D1 of the inner inclined groove 28 may be less than 30% or more than 80% of the groove depth Dm of the circumferential main groove 16. The groove depth Dg of the inclined narrow groove 52 may be less than 20% or more than 60% of the groove depth Dm of the circumferential main groove 16. The groove depth D4 of the reverse inclined groove 54 may be less than 40% or more than 80% of the groove depth Dm of the circumferential main groove 16.

[0131] The outer sipes 84 are not limited to extending along the inclined narrow grooves 52, but may extend in a direction exceeding ±20° with respect to the extension direction of the inclined narrow grooves 52. The inner sipes 30 are not limited to extending along the tire width direction, but may extend in a direction exceeding ±20° with respect to the tire width direction.

[0132] The outermost block 56s does not necessarily have to have the recess 86. The depth D5 of the recess 86 may be less than 0.5 mm or may be greater than 2.0 mm.

[0133] (Examples) Tires according to Examples 1 to 31 and pneumatic tires according to Reference Examples 1 to 3 were manufactured, each having a tire size of 245 / 45R19 102V (specified by JATMA) and having a raised portion with the shape shown in Fig. 1 when mounted on a rim. Detailed conditions of these tires are as shown in Tables 1 and 2 below.

[0134] In Tables 1 and 2, each item conforms to the definition described in this specification. For example, in the column "Positional relationship between inner oblique groove and oblique groove or oblique narrow groove," if the oblique groove or oblique narrow groove is arranged on an extension line of the inner oblique groove, it is written as "on extension line," if it is not on the extension line, it is written as "different," and if there is no inner oblique groove, it is written as "-." In the column "Extending direction of oblique narrow groove relative to outer sipe," if the outer sipe extends along the oblique narrow groove, it is written as "parallel." In the column "Circumferential narrow groove," if a circumferential narrow groove is provided in the outer region, it is written as "present," and if it is not provided, it is written as "absent." In the column "Positional relationship between oblique groove and oblique narrow groove," if the oblique groove and the oblique narrow groove are arranged alternately in the tire circumferential direction, it is written as "alternate," if they are not arranged alternately, it is written as "different," and if there is no inner oblique groove, it is written as "-."

[0135] The tires of Examples 1 to 31 and the tires of Reference Examples 1 to 3 thus prepared were mounted on 19x9.0J aluminum rims at an air pressure (F / R) of 250 kPa / 250 kPa, and each test tire was mounted on a 4WD test vehicle (displacement: 3000 cc). Evaluations were then carried out on the handling stability on wet roads, snowy roads, and dry roads according to the following procedures.

[0136] (Steering stability on wet roads) A test driver performed a sensory evaluation while driving on a wet road (water depth 1 mm). The evaluation results were expressed as an index, with Reference Example 1 being assigned an index value of 100. A higher index value indicates better steering stability on wet roads.

[0137] (Steering stability on snowy roads) A test driver performed a sensory evaluation while driving on a packed snowy road. The evaluation results were expressed as an index, with Reference Example 1 being set at 100. A higher index value means better steering stability on snowy roads.

[0138] (Dry road handling stability) A test driver performed a sensory evaluation while driving on a dry road surface where high-speed driving is possible. The evaluation results were expressed as an index, with Reference Example 1 being set at 100. A larger index value means better dry road handling stability.

[0139]

[0140]

[0141] From Tables 1 and 2 above, it can be seen that the tires of the examples are superior in steering stability on wet roads, on snowy roads, and on dry roads compared to the tires of the reference examples.

[0142] REFERENCE SIGNS LIST 10 Tire 12 Tread portion 14 Tread surface 16 Circumferential main groove 16w Groove wall (circumferential main groove) 18 Inner land portion 20 Outer land portion 22 First circumferential main groove 24 Second circumferential main groove 26 Circumferential narrow groove 28 Inner inclined groove 30 Inner sipe 31 Tip (inner sipe) 32 One end (inner inclined groove) 34 Other end (inner inclined groove) 34f Other end of first inner inclined groove 34s Other end of second inner inclined groove 36 First inner inclined groove 38 Second inner inclined groove 40 First inclined portion 41 Groove wall (first inclined portion) 42 Second inclined portion 43 Groove wall (second inclined portion) 44 Bend portion 46 Tip (first inclined portion) on the outer side in the tire width direction 50 Inclined groove 50w Groove wall (inclined groove) 52 Oblique narrow groove 52w Groove wall (oblique narrow groove) 52u Groove bottom (oblique narrow groove) 54 Reverse oblique groove 56 Block 56c Block (adjacent to circumferential main groove) 56s Outermost block 58 Inner tip in the tire width direction (oblique groove) 60 Outer tip in the tire width direction (oblique groove) 62 Main oblique portion 64 Bottom-raised portion 66 Inner tip in the tire width direction (main oblique portion) 68 Inclined surface 70 Flat surface 72 Inner tip in the tire width direction (oblique surface) 74 Inner tip in the tire width direction (oblique narrow groove) 76 Outer tip in the tire width direction (oblique narrow groove) 78 Groove bottom sipe 78t Opening (groove bottom sipe) 78b Bottom surface (groove bottom sipe) 80 Inner tip in the tire width direction (reverse oblique groove) 82 Outer tip in the tire width direction (reverse oblique groove) 84 Outer sipe 86 Recess 86e Edge (recess) 88 Circumferential narrow groove 90 Outer narrow groove 92 Inner narrow groove 94 Deep groove portion CP Tire equatorial plane E Ground contact edge EL Ground contact edge line LDE Distance in the tire width direction between tread edges Wce Length in the tire width direction of the inner land portion Wm Groove width of circumferential main groove W1 Groove width (inclined groove) W2 Groove width (inclined narrow groove) W3 Groove width (reverse inclined groove) W4 Block width Dm Groove depth of circumferential main groove D1 First groove depth (inner inclined groove) D2 Second groove depth (main inclined portion) D3 Third groove depth (bottom raised portion) D4 Groove depth (reverse inclined groove) D5 Depth (recess) Dg Groove depth (inclined narrow groove) Ds Groove depth (groove bottom sipe) T Tread edge P1 First end point P2 Second end point Lg: Groove length (inclined narrow groove); Ls: Groove length (groove bottom sipe); L1: First imaginary line (extension direction of reverse inclined groove); L2: Second imaginary line (outer region);L3: Third virtual line (outer region) SH: Outer region θa: Angle (angle between the extension direction of the first inclined portion and the tire circumferential direction) θb: Angle (angle between the extension direction of the second inclined portion and the tire circumferential direction) θc: Angle (angle between the extension direction of the reverse inclined groove and the tire circumferential direction) θd: Angle (outer sipe)

Claims

1. A tire comprising: a circumferential main groove; an inner land portion defined by at least two of the circumferential main grooves; and outer land portions arranged on either side of the circumferential main groove on the outer side in the tire width direction of the inner land portion, wherein the tire has an inclined groove, an inclined narrow groove, and a reverse inclined groove arranged in the outer land portion, wherein the inclined groove extends from the circumferential main groove outward in the tire width direction, is inclined from the leading-in side to the trailing-out side in the tire circumferential direction, and has a tip connected to a tread edge, the inclined narrow groove extends from the circumferential main groove outward in the tire width direction, is inclined from the leading-in side to the trailing-out side in the tire circumferential direction, and has a tip arranged within the outer land portion, the reverse inclined groove extends from the trailing-out side to the leading-in side in the tire circumferential direction, and is inclined from the inner side to the outer side in the tire width direction, and the groove width of the inclined narrow groove is 20% to 80% of the groove width of the inclined groove.

2. The tire according to claim 1, wherein the angle formed between the extending direction of the reverse inclined groove and the tire circumferential direction is 5 degrees or more and 50 degrees or less.

3. The tire according to claim 1, wherein the inclined groove has: a main inclined portion having a first groove depth; and a bottom-up portion having a second groove depth shallower than the first groove depth, between an end of the main inclined portion on the inner side in the tire width direction and the circumferential main groove.

4. A tire as described in claim 1, wherein the inner land portion is arranged at a position including the tire equatorial plane and has an inner inclined groove, the inner inclined groove extending inward in the tire width direction from the circumferential main groove and inclined from the trailing-edge side to the leading-edge side in the tire circumferential direction, the inner inclined groove having a first inner inclined groove and a second inner inclined groove with a tip located within the inner land portion, and the first inner inclined groove intersects with the tire equatorial plane.

5. A tire as described in claim 4, wherein the first inner inclined groove has a first inclined portion, a second inclined portion, and a bent portion, the first inclined portion and the second inclined portion are connected via the bent portion, and the extending directions of the first inclined portion and the second inclined portion change at the bent portion.

6. The tire according to claim 5, wherein θa is the angle formed between the extension direction of the first inclined portion and the tire circumferential direction, and θb is the angle formed between the extension direction of the second inclined portion and the tire circumferential direction, θa is 30° or more and 70° or less, and satisfies the following formula (1): θa+5°≦θb≦90°...formula (1) 7. The tire according to claim 4, wherein the groove depth of the inner oblique groove is 30% to 80% of the groove depth of the circumferential main groove.

8. The tire according to claim 4, wherein the inclined groove or the inclined narrow groove is disposed on an extension line of the inner inclined groove.

9. The tire according to claim 1, wherein the distance between tread ends in the tire width direction is LDE and the length of the inner land portion in the tire width direction is Wce, and the tire satisfies the following formula (2): 0.08≦Wce / LDE≦0.20...formula (2).

10. The tire according to claim 1, wherein the following formula (3) is satisfied, where Wa is the groove width of the opening end of the inclined groove that connects to the circumferential main groove, and Wb is the groove width of the opening end of the inclined groove at the tread edge: 0.3≦Wa / Wb≦0.8 (3) 11. The tire according to claim 1, wherein the groove depth of the inclined narrow groove is 20% to 60% of the groove depth of the circumferential main groove.

12. The tire according to claim 1, wherein the narrow inclined groove has a groove bottom sipe, the groove bottom sipe is formed at the groove bottom of the narrow inclined groove, and the following formula (4) is satisfied, where Dg is the groove depth of the narrow inclined groove and Ds is the groove depth of the groove bottom sipe: 0.7≦Ds / Dg≦1.3...formula (4) 13. The tire according to claim 1, wherein the groove depth of the reverse oblique groove is 40% or more and 80% or less of the groove depth of the circumferential main groove.

14. A tire according to claim 1, wherein the outer land portion has a plurality of blocks defined by the inclined grooves, the inclined narrow grooves, and the reverse inclined grooves, and some of the plurality of blocks have outer sipes.

15. The tire of claim 14, wherein the external sipes extend along the oblique grooves.

16. The tire according to claim 1, wherein the inner land portion has an inner sipe, and the inner sipe extends along the tire width direction.

17. The tire according to claim 14, wherein of the plurality of blocks, the outermost block arranged outermost in the tire width direction has a recessed portion, the recessed portion being arranged outward in the tire width direction from the tip of the inclined narrow groove, and the recessed portion has a plurality of edges that intersect in the tire circumferential direction.

18. The tire according to claim 17, wherein the depth of the recess is 0.5 mm or more and 3.0 mm or less.

19. The tire according to claim 1, which has circumferential narrow grooves extending from the ground contact edge to the inner side in the tire width direction, in a range of 5% to 15% of the tire width direction length from the tire equatorial plane to the ground contact edge.

20. The tire according to claim 19, wherein two circumferential narrow grooves are provided on each side in the tire width direction, and the groove width of the circumferential narrow groove on the outer side in the tire width direction of the two circumferential narrow grooves is Wout, and the groove width of the circumferential narrow groove on the inner side in the tire width direction of the two circumferential narrow grooves is Win, the following formula (5) is satisfied: 0.3≦Wout / Win≦0.7...formula (5) 21. The tire according to claim 19, wherein two circumferential narrow grooves are provided on each side in the tire width direction, and the groove depth of the circumferential narrow groove on the outer side in the tire width direction of the two circumferential narrow grooves is Dout and the groove depth of the circumferential narrow groove on the inner side in the tire width direction of the two circumferential narrow grooves is Din, and the tire satisfies the following formula (6): 0.4≦Dout / Din≦0.8...formula (6)

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