tire

Abstract

Among a plurality of circumferential grooves 30 provided in a pneumatic tire 1, an inner shoulder circumferential groove 31, which is the innermost circumferential groove 30 in a vehicle mounting direction, and an inner center circumferential groove 32, which is a circumferential groove 30 adjacent to the inner shoulder circumferential groove 31, are positioned on an inner side in the vehicle mounting direction with respect to a tire equatorial plane CL. The inner shoulder circumferential groove 31 satisfies the relationship A > B between a groove wall angle A of a groove wall 31a positioned closer to the inner side in the vehicle mounting direction and a groove wall angle B of the groove wall 31a positioned closer to an outer side in the vehicle mounting direction. The groove wall angle A is in the range of 13° to 20°, and the groove wall angle B is in the range of 8° to 12°. For the inner center circumferential groove 32, a groove wall angle C of a groove wall 32a positioned closer to the inner side in the vehicle mounting direction and a groove wall angle D of the groove wall 32a positioned closer to the outer side in the vehicle mounting direction are both in the range of 8° to 12°; therefore, the pneumatic tire 1 can achieve both NV performance and wet performance.

Description

tire

[0001] The present invention relates to a tire.

[0002] Since various performance requirements are required for tires mounted on vehicles, some conventional tires satisfy the desired performance by devising the shape of the grooves arranged on the surface of the tread. For example, the tire described in Patent Document 1 suppresses the occurrence of uneven wear and groove cracks by specifying the groove wall angle and the curvature radius of the bottom of the groove wall.

[0003] In addition, the pneumatic radial tire described in Patent Document 2 has divergent inclined portions on the groove walls of the circumferential grooves in the tread side regions located on the outer side of the vehicle when the tire is mounted on the vehicle, thereby greatly increasing cornering force. In addition, the pneumatic radial tire described in Patent Document 3 has one circumferential main groove in one half of the tread surface with the tire equator as the boundary, and two circumferential main grooves in the other half, and by specifying the angles of the groove walls of the three circumferential groove portions, it achieves both hydroplaning resistance and quietness during cornering.

[0004] Japanese Patent No. 5436439 Japanese Patent No. 2977879 Japanese Patent Laid-Open No. 2013-189126

[0005] Here, grooves formed on the tread surface of a tire are primarily intended to improve wet performance, which is driving performance on wet roads. However, grooves formed on the tread surface also affect NV (Noise Vibration) performance, which is performance related to noise generated from the tire while the vehicle is running. Reducing the groove width and groove volume of the grooves formed on the tread surface is effective for improving NV performance, but reducing the groove width and groove volume of the grooves makes it difficult to ensure drainage, which tends to deteriorate wet performance. For this reason, it is very difficult to achieve both NV performance and wet performance.

[0006] The present invention has been made in view of the above, and has an object to provide a tire that can achieve both NV performance and wet performance.

[0007] In order to solve the above-mentioned problems and achieve the object, a tire according to the present invention includes a plurality of circumferential grooves extending in a tire circumferential direction, and when the innermost circumferential groove in a vehicle mounting direction among the plurality of circumferential grooves is an inner shoulder circumferential groove and the circumferential groove adjacent to the inner shoulder circumferential groove in the tire width direction is an inner center circumferential groove, the inner shoulder circumferential groove is located on the inner side of the tire equatorial plane in the vehicle mounting direction, and the inner center circumferential groove is located on the inner side of the tire equatorial plane in the vehicle mounting direction or is located on the tire equatorial plane, and the inner shoulder circumferential grooves are a pair of grooves facing each other in the tire width direction. Among the walls, a groove wall angle A with respect to the tire radial direction of the groove wall located closer to the inner side in the vehicle mounting direction and a groove wall angle B with respect to the tire radial direction of the groove wall located closer to the outer side in the vehicle mounting direction satisfy the relationship A>B, and the groove wall angle A is within a range of 13° or more and 20° or less, and the groove wall angle B is within a range of 8° or more and 12° or less, and the inner center circumferential groove is characterized in that, of a pair of groove walls opposing each other in the tire width direction, a groove wall angle C with respect to the tire radial direction of the groove wall located closer to the inner side in the vehicle mounting direction and a groove wall angle D with respect to the tire radial direction of the groove wall located closer to the outer side in the vehicle mounting direction are both within a range of 8° or more and 12° or less.

[0008] In the tire, it is preferable that the groove wall angle B of the inner shoulder circumferential groove and the groove wall angle C of the inner center circumferential groove satisfy the relationship of -1°≦B−C≦1°.

[0009] In the tire, it is preferable that the groove wall angle B of the inner shoulder circumferential groove and the groove wall angle C of the inner center circumferential groove satisfy the relationship B<C.

[0010] In the tire, it is preferable that the groove wall angle C and the groove wall angle D of the inner center circumferential groove satisfy the relationship of -2°≦D−C≦2°.

[0011] In the tire, it is preferable that the inner shoulder circumferential groove and the inner center circumferential groove have a groove width W1 of the inner shoulder circumferential groove and a groove width W2 of the inner center circumferential groove satisfy the relationship W2<W1.

[0012] In the tire, the groove width W1 of the inner shoulder circumferential groove and the groove width W2 of the inner center circumferential groove preferably satisfy the relationship 1.0≦W1 / W2≦1.2.

[0013] Furthermore, in the above tire, it is preferable that the tire has a plurality of land portions defined by the circumferential grooves, and that sipes are arranged in the inner shoulder land portion, which is the land portion defined on the inner side in the tire width direction by the inner shoulder circumferential groove, and in the inner intermediate land portion, which is the land portion defined on both sides in the tire width direction by the inner shoulder circumferential groove and the inner center circumferential groove.

[0014] In addition, in the tire described above, it is preferable that the sipes arranged in the inner intermediate land portion communicate with both the inner shoulder circumferential groove and the inner center circumferential groove, and have sipes that communicate with the inner shoulder circumferential groove via cutouts and sipes that communicate with the inner center circumferential groove via cutouts, the sipes arranged in the inner shoulder land portion extend in the tire width direction across the ground contact edge and communicate with the inner shoulder circumferential groove, and at least some of the multiple sipes arranged in the inner shoulder land portion communicate with the inner shoulder circumferential groove via cutouts, and a sipe that communicates with the inner center circumferential groove via cutouts is arranged in a center land portion, which is a land portion that is located on the opposite side of the inner intermediate land portion in the tire width direction from the inner center circumferential groove and is defined by the inner center circumferential groove, among the multiple land portions.

[0015] Furthermore, in the tire described above, it is preferable that the cutout portion disposed in the inner shoulder land portion and communicating with the inner shoulder circumferential groove has a maximum length Dc1 in the tire width direction, where Dc1 is the contact width Wb1 of the inner shoulder land portion, in a range of 0.10≦Dc1 / Wb1≦0.15; the cutout portion disposed in the inner intermediate land portion and communicating with the inner shoulder circumferential groove has a maximum length Dc2 in the tire width direction, where Dc2 is the contact width Wb2 of the inner intermediate land portion, in a range of 0.35≦Dc2 / Wb2≦0.45; and the relationship between the maximum length Dc2 in the tire width direction of the cutout portion disposed in the inner intermediate land portion and communicating with the inner shoulder circumferential groove and the maximum length Dc3 in the tire width direction of the cutout portion disposed in the inner intermediate land portion and communicating with the inner center circumferential groove is within a range of 1.1≦Dc2 / Dc3≦1.5.

[0016] Furthermore, in the tire, it is preferable that the cutout portion disposed in the inner shoulder land portion and communicating with the inner shoulder circumferential groove has a maximum depth h1 in the tire radial direction, where h1 is the maximum depth Hs of the inner shoulder circumferential groove, in a range of 0.45≦h1 / Hs≦0.55; the cutout portion disposed in the inner intermediate land portion and communicating with the inner shoulder circumferential groove has a maximum depth h2 in the tire radial direction, where hs is the maximum depth Hs of the inner shoulder circumferential groove, in a range of 0.55≦h2 / Hs≦0.65; and the relationship between the maximum depth h2 in the tire radial direction of the cutout portion disposed in the inner intermediate land portion and communicating with the inner shoulder circumferential groove and the maximum depth h3 in the tire radial direction of the cutout portion disposed in the inner intermediate land portion and communicating with the inner center circumferential groove is within a range of 0.99≦h2 / h3≦1.01.

[0017] In addition, in the above tire, it is preferable that the width in the tire circumferential direction of the cutout portion to which the sipe communicates is within a range of 7 to 13 times the width in the tire circumferential direction of the sipe communicating with the cutout portion.

[0018] In addition, in the tire, it is preferable that the cutouts arranged in the inner intermediate land portion are arranged such that the cutouts communicating with the inner shoulder circumferential groove and the cutouts communicating with the inner center circumferential groove are alternately arranged in the tire circumferential direction.

[0019] In the tire, the sipe disposed in the inner shoulder land portion preferably has a three-dimensional shape.

[0020] In the tire, the tread portion preferably has a cap tread having a tan δ at 0° C. in the range of 0.88 to 0.94 and a rubber hardness in the range of 58 to 63.

[0021] Furthermore, in the above tire, four circumferential grooves are arranged, the tread pattern of the tread portion is an asymmetric pattern that is asymmetric on both sides of the tire equatorial plane in the tire width direction, and it is preferable that, among the multiple land portions, the outer shoulder land portion, which is the land portion located outermost in the vehicle mounting direction, has multiple sipes arranged side by side in the tire circumferential direction without having lug grooves and extending in the tire width direction.

[0022] In the tire, it is preferable that the four circumferential grooves have groove widths that narrow from the inner side toward the outer side in the vehicle mounting direction.

[0023] The tire according to the present invention has an effect of achieving both NV performance and wet performance.

[0024] FIG. 1 is a meridian cross-sectional view of a tire showing a main portion of a pneumatic tire according to an embodiment. FIG. 2 is a view seen from the arrows E-E in FIG. 1. FIG. 3 is a cross-sectional view taken along line F-F in FIG. 2. FIG. 4 is a detailed view of a portion of the tread portion shown in FIG. 2 that is located inward of the tire equatorial plane in the vehicle mounting direction. FIG. 5 is a cross-sectional view taken along line F-F in FIG. 2, and is an explanatory diagram of a notch that communicates with a circumferential groove. FIG. 6A is a table showing the results of a performance evaluation test of a pneumatic tire. FIG. 6B is a table showing the results of a performance evaluation test of a pneumatic tire. FIG. 6C is a table showing the results of a performance evaluation test of a pneumatic tire.

[0025] Hereinafter, embodiments of a tire according to the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to these embodiments. Furthermore, the components in the following embodiments include those that are replaceable and easily conceivable by a person skilled in the art, or those that are substantially the same.

[0026] [Embodiment] In the following description, a pneumatic tire 1 will be used as an example of a tire according to the present invention. The pneumatic tire 1, which is an example of a tire, can be filled with air, an inert gas such as nitrogen, or other gases.

[0027] In the following description, the tire radial direction refers to the direction perpendicular to the tire rotation axis (not shown), which is the rotation axis of the pneumatic tire 1. 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 (tire equator line) CL in the tire width direction, and the tire widthwise outer side refers to the side away from the tire equatorial plane CL in the tire width direction. The tire equatorial plane CL is a plane that is perpendicular to the tire rotation axis and passes through the center of the tire width of the pneumatic tire 1. The tire equatorial plane CL coincides in position in the tire width direction with the tire widthwise centerline, which is the center position of the pneumatic tire 1 in the tire width direction. The tire width is the width in the tire width direction between the portions located outermost in the tire width direction, that is, the distance in the tire width direction between the portions farthest from the tire equatorial plane CL. The tire equator line refers to a line that is on the tire equatorial plane CL and extends along the tire circumferential direction of the pneumatic tire 1. In the following description, the tire meridian cross section refers to a cross section obtained by cutting the tire along a plane that includes the tire rotation axis.

[0028] FIG. 1 is a tire meridian cross-section showing a main portion of a pneumatic tire 1 according to an embodiment. The pneumatic tire 1 according to this embodiment has a specified mounting direction relative to a vehicle, i.e., the direction when mounted on a vehicle. That is, the side of the pneumatic tire 1 according to this embodiment that faces the inside of the vehicle when mounted on the vehicle is the inside of the vehicle mounting direction, and the side that faces the outside of the vehicle when mounted on the vehicle is the outside of the vehicle mounting direction. Note that the designation of the inside of the vehicle mounting direction and the outside of the vehicle mounting direction is not limited to when the tire is mounted on a vehicle. For example, when mounted on a rim, the orientation of the rim relative to the inside and outside of the vehicle in the tire width direction is determined. Therefore, when mounted on a rim, the orientation of the pneumatic tire 1 relative to the inside and outside of the vehicle in the tire width direction is specified. The pneumatic tire 1 also has a mounting direction indicator (not shown) that indicates the mounting direction relative to the vehicle. The mounting direction indicator is, for example, configured by a mark or a concavo-convex shape on the sidewall portion 8 of the tire. For example, Article 30 of the Economic Commission for Europe (ECER 30) requires that a mounting direction indicator be provided on the sidewall portion 8 that is on the outer side in the vehicle mounting direction when mounted on the vehicle. The pneumatic tire 1 according to this embodiment is a pneumatic tire 1 that is mainly used for passenger cars.

[0029] A pneumatic tire 1 according to this embodiment has a tread portion 2 disposed at the radially outermost portion of the tire when viewed in a tire meridian cross section, and the tread portion 2 has a cap tread 4 made of a rubber composition. The surface of the tread portion 2, i.e., the portion that comes into contact with the road surface when a vehicle (not shown) equipped with the pneumatic tire 1 is traveling, is formed as a tread contact surface 3, and the tread contact surface 3 constitutes part of the contour of the pneumatic tire 1.

[0030] The cap tread 4 of the tread portion 2 uses a compound having a tan δ at 0°C in the range of 0.88 to 0.94 and a rubber hardness in the range of 58 to 63. Note that tan δ at 0°C is measured in accordance with JIS K6394 using a viscoelasticity spectrometer (for example, manufactured by Toyo Seiki Seisakusho) under conditions of a frequency of 20 Hz, an initial strain of 10%, a dynamic strain of ±2%, and a temperature of 0°C. The rubber hardness is JIS-A hardness, which is a durometer hardness measured in accordance with JIS K6253 using an A-type durometer at a temperature of 20°C.

[0031] Shoulder portions 5 are located at both outer ends of the tread portion 2 in the tire width direction, and sidewall portions 8 are arranged radially inward of the shoulder portions 5. That is, the sidewall portions 8 are arranged on both sides in the tire width direction of the tread portion 2. In other words, the sidewall portions 8 are arranged in two locations on both sides of the pneumatic tire 1 in the tire width direction, and form the outermost exposed portions of the pneumatic tire 1 in the tire width direction.

[0032] Bead portions 10 are located radially inward of each sidewall portion 8 located on both sides in the tire width direction. Similar to the sidewall portions 8, the bead portions 10 are located at two locations on both sides of the tire equatorial plane CL; that is, a pair of bead portions 10 are located on both sides of the tire equatorial plane CL in the tire width direction. Each bead portion 10 is provided with a bead core 11, and a bead filler 12 is provided on the tire radially outer side of the bead core 11. The bead core 11 is an annular member formed by bundling bead wires, which are steel wires, into a circular shape, and the bead filler 12 is a rubber member located on the tire radially outer side of the bead core 11.

[0033] A belt layer 14 is also disposed in the tread portion 2. The belt layer 14 has a multi-layer structure in which multiple belts 141, 142 and a belt cover 143 are laminated. In this embodiment, two layers of belts 141, 142 are laminated. The belts 141, 142 constituting the belt layer 14 are formed by coating multiple belt cords made of steel or organic fiber materials such as polyester, rayon, or nylon with a coating rubber and rolling them. The belt angle, defined as the inclination angle of the belt cords with respect to the tire circumferential direction, is within a predetermined range (e.g., 20° to 55°). The two-layer belts 141, 142 have different belt angles. Therefore, the belt layer 14 has a so-called cross-ply structure in which the two-layer belts 141, 142 are laminated with the inclination directions of the belt cords crossing each other. In other words, the two-layer belts 141, 142 are provided as so-called cross belts in which the belt cords of the respective belts 141, 142 are arranged in a direction in which they cross each other.

[0034] The belt cover 143 is formed by covering a plurality of belt cover cords made of steel or organic fiber material such as polyester, rayon, or nylon with coating rubber and rolling the covered cords, and the belt angle, defined as the inclination angle of the belt cover cords with respect to the tire circumferential direction, is within a predetermined range (for example, 0° to 10°). The belt cover 143 is, for example, a strip material formed by covering one or more belt cover cords with coating rubber, and is formed by winding this strip material spirally around the tire rotation axis from the outer side in the tire radial direction of the two-layered belts 141 and 142.

[0035] A carcass layer 13 containing the cords of the radial ply is provided continuously on the tire radially inward side of the belt layer 14 and on the tire equatorial plane CL side of the sidewall portion 8. Therefore, the pneumatic tire 1 according to this embodiment is configured as a so-called radial tire. The carcass layer 13 has a single-layer structure consisting of one carcass ply or a multi-layer structure consisting of a plurality of carcass plies stacked together, and is toroidally spanned between a pair of bead portions 10 arranged on both sides in the tire width direction to form the framework of the tire.

[0036] Specifically, the carcass layer 13 is disposed from one bead portion 10 to the other of a pair of bead portions 10 located on both sides in the tire width direction, and is wound back along the bead core 11 at the bead portion 10 toward the outside in the tire width direction so as to enclose the bead core 11 and the bead filler 12. The bead filler 12 is made of a rubber material that is disposed in a space formed on the outside in the tire radial direction of the bead core 11 by folding back the carcass layer 13 at the bead portion 10 in this manner. The belt layer 14 is disposed on the outside in the tire radial direction of the portion of the carcass layer 13 that is positioned in the tread portion 2 and that is stretched between the pair of bead portions 10. The carcass ply of the carcass layer 13 is formed by coating a plurality of carcass cords made of steel or an organic fiber material such as aramid, nylon, polyester, or rayon with coating rubber and rolling the coated cords. The carcass cords constituting the carcass ply are arranged in parallel at a certain angle relative to the tire circumferential direction, along the tire meridian direction.

[0037] In the bead portion 10, a rim cushion rubber 17 that forms the contact surface of the bead portion 10 with the rim flange is arranged on the tire radially inner side and tire widthwise outer side of the bead core 11 and the turned-up portion of the carcass layer 13. Furthermore, an inner liner 16 is formed along the carcass layer 13 on the inner side of the carcass layer 13 or on the inner side of the carcass layer 13 in the pneumatic tire 1. The inner liner 16 forms a tire inner surface 18, which is the inner surface of the pneumatic tire 1.

[0038] 2 is a view taken along the arrows E-E in FIG. 1. The tread portion 2 has a plurality of circumferential grooves 30 formed in the tread contact surface 3, extending in the tire circumferential direction. The circumferential grooves 30 define a plurality of land portions 20 on the surface of the tread portion 2. In this embodiment, four circumferential grooves 30 are formed side by side in the tire width direction. The four circumferential grooves 30 are arranged two on each side of the tire equatorial plane CL in the tire width direction. These circumferential grooves 30 are grooves that are required to display a wear indicator as defined by JATMA. The circumferential grooves 30 have a groove width in the range of 8.0 mm to 15.0 mm, and a groove depth in the range of 6.9 mm to 9.0 mm.

[0039] In this embodiment, the so-called tread pattern of the tread portion 2, which is a pattern of the shapes and arrangements of the circumferential grooves 30 and the like formed in the tread portion 2, is an asymmetric pattern on both sides in the tire width direction with the tire equatorial plane CL as the boundary. That is, the tread pattern of the tread portion 2 is not line-symmetric with the tire equatorial plane CL as the axis of symmetry, but is an asymmetric pattern that is asymmetric on both sides of the tire equatorial plane CL in the tire width direction. In this embodiment, in which the tread pattern is an asymmetric pattern, the groove widths of the four circumferential grooves 30 narrow from the inner side to the outer side in the vehicle mounting direction. In this case, the groove width is the groove width at the position of the opening of the circumferential grooves 30 relative to the tread contact surface 3.

[0040] The four circumferential grooves 30 are, from the inner side in the vehicle mounting direction to the outer side in the vehicle width direction, an inner shoulder circumferential groove 31, an inner center circumferential groove 32, an outer center circumferential groove 33, and an outer shoulder circumferential groove 34. Of the four circumferential grooves 30, the inner shoulder circumferential groove 31 and the inner center circumferential groove 32 are arranged on the inner side in the vehicle mounting direction with respect to the tire equatorial plane CL, and the outer center circumferential groove 33 and the outer shoulder circumferential groove 34 are arranged on the outer side in the vehicle mounting direction with respect to the tire equatorial plane CL.

[0041] Specifically, the inner shoulder circumferential groove 31 is the innermost circumferential groove 30 in the vehicle mounting direction, and the inner center circumferential groove 32 is the circumferential groove 30 adjacent to the inner shoulder circumferential groove 31 on the outer side in the vehicle mounting direction in the tire width direction. Also, the outer shoulder circumferential groove 34 is the outermost circumferential groove 30 in the vehicle mounting direction, and the outer center circumferential groove 33 is the circumferential groove 30 adjacent to the outer shoulder circumferential groove 34 on the inner side in the vehicle mounting direction in the tire width direction.

[0042] The land portions 20 defined by the circumferential groove 30 include an inner shoulder land portion 21, an inner intermediate land portion 22, a center land portion 23, an outer intermediate land portion 24, and an outer shoulder land portion 25. Of these, the inner shoulder land portion 21 is disposed outward in the tire width direction from the inner shoulder circumferential groove 31, and its inner portion in the tire width direction is the land portion 20 defined by the inner shoulder circumferential groove 31. In other words, the inner shoulder land portion 21 is the land portion 20 disposed innermost in the vehicle mounting direction.

[0043] The inner intermediate land portion 22 is a land portion 20 that is defined on both sides in the tire width direction by the inner shoulder circumferential groove 31 and the inner center circumferential groove 32. That is, the outer portion of the inner intermediate land portion 22 in the tire width direction is defined by the inner shoulder circumferential groove 31, and the inner portion in the tire width direction is defined by the inner center circumferential groove 32.

[0044] The center land portion 23 is located on the opposite side of the inner center circumferential groove 32 in the tire width direction from the side where the inner intermediate land portion 22 is located, and is a land portion 20 that is defined by the inner center circumferential groove 32 and the outer center circumferential groove 33. That is, the center land portion 23 is a land portion 20 that is defined on both sides in the tire width direction by the inner center circumferential groove 32 and the outer center circumferential groove 33. In this way, the center land portion 23 that is defined on both sides in the tire width direction by the inner center circumferential groove 32 and the outer center circumferential groove 33 is located on the tire equatorial plane CL.

[0045] The outer intermediate land portion 24 is a land portion 20 that is defined on both sides in the tire width direction by the outer center circumferential groove 33 and the outer shoulder circumferential groove 34. That is, the inner portion of the outer intermediate land portion 24 in the tire width direction is defined by the outer center circumferential groove 33, and the outer portion in the tire width direction is defined by the outer shoulder circumferential groove 34.

[0046] The outer shoulder land portion 25 is disposed outward in the tire width direction relative to the outer shoulder circumferential groove 34, and its inner portion in the tire width direction is the land portion 20 defined by the outer shoulder circumferential groove 34. In other words, the outer shoulder land portion 25 is the land portion 20 disposed outermost in the vehicle mounting direction.

[0047] Additionally, a circumferential narrow groove 40 extending in the tire circumferential direction is arranged in the outer shoulder land portion 25. The circumferential narrow groove 40 is arranged further outward in the tire width direction than the outer shoulder circumferential groove 34, and has a narrower groove width than the circumferential narrow groove 40. In this embodiment, the circumferential narrow groove 40 has a groove width in the range of 1.5 mm to 2.0 mm, and a groove depth in the range of 3.5 mm to 4.5 mm.

[0048] The outer shoulder land portion 25 has the circumferential narrow grooves 40 arranged in this manner, and thus the outer shoulder land portion 25 is divided in the tire width direction by the circumferential narrow grooves 40. That is, the outer shoulder land portion 25 has a first outer shoulder land portion 25a located on the inner side of the circumferential narrow groove 40 in the tire width direction, and a second outer shoulder land portion 25b located on the outer side of the circumferential narrow groove 40 in the tire width direction.

[0049] As described above, sipes 50 and cutout portions 60 are arranged in each land portion 20 defined by the circumferential grooves 30. The sipes 50 arranged in the land portion 20 are formed, for example, to extend in the tire width direction. The ends of the sipes 50 may terminate within the land portion 20, or may open into other grooves. The sipes 50 may extend in the tire width direction and be inclined toward the tire circumferential direction, or may extend in the tire width direction and bend toward the tire circumferential direction.

[0050] The sipes 50 referred to here are narrow grooves formed in the tread contact surface 3, and when the pneumatic tire 1 is mounted on a specified rim and under a specified internal pressure condition and no load is applied, the wall surfaces constituting the narrow grooves do not come into contact with each other. However, when a load is applied vertically on a flat plate and the narrow grooves are located in a portion of the contact surface formed on the flat plate, or when the land portion 20 on which the narrow grooves are formed collapses, the wall surfaces constituting the narrow grooves, or at least a portion of the portions provided on the wall surfaces, come into contact with each other due to deformation of the land portion 20. In this embodiment, the sipes 50 have a groove width of 0.8 mm or less, and a maximum depth from the tread contact surface 3 within a range of 5.0 mm to 7.0 mm.

[0051] The specified rim here refers to the "standard rim" specified by JATMA, the "design rim" specified by TRA, or the "measuring rim" specified by ETRTO. The specified internal pressure refers to the "maximum air pressure" specified by JATMA, the maximum value listed in the "tire load limits at various cold inflation pressures" specified by TRA, or the "inflation pressures" specified by ETRTO.

[0052] The sipe 50 may be a so-called three-dimensional sipe or a two-dimensional sipe. The three-dimensional sipe here refers to a sipe 50 having a curved wall surface with amplitude in the width direction of the sipe 50 in both a cross-sectional view in which the length direction of the sipe 50 is the normal direction (a cross-sectional view including the width direction and depth direction of the sipe 50) and a cross-sectional view in which the depth direction of the sipe 50 is the normal direction (a cross-sectional view including the width direction and length direction of the sipe 50). The two-dimensional sipe refers to a sipe 50 having a straight wall surface in any cross-sectional view in which the length direction of the sipe 50 is the normal direction (a cross-sectional view including the width direction and depth direction of the sipe 50).

[0053] The cutout portion 60 arranged in the land portion 20 is formed in the shape of a narrow groove that is relatively short in length and extends in the tire width direction, with one end communicating with the circumferential groove 30 and the other end terminating within the land portion 20. The cutout portion 60 that is short in length and extends in the tire width direction may be inclined toward the tire circumferential direction while extending in the tire width direction.

[0054] The sipes 50 arranged in the land portion 20 include an inner shoulder sipe 51, an inner intermediate sipe 52, a center sipe 53, an outer intermediate sipe 54, and an outer shoulder sipe 55. The cutouts 60 arranged in the land portion 20 include an inner shoulder cutout 61, an inner intermediate cutout 62, a center cutout 63, an outer intermediate cutout 64, and an outer shoulder cutout 65.

[0055] Of these, the inner shoulder sipe 51 is a sipe 50 arranged in the inner shoulder land portion 21. The inner shoulder sipe 51 extends in the tire width direction, straddling the ground contact edge T located on the inner shoulder land portion 21, and its inner end in the tire width direction communicates with the inner shoulder circumferential groove 31 that defines the inner shoulder land portion 21. In the inner shoulder land portion 21, multiple inner shoulder sipes 51 extending in the tire width direction and straddling the ground contact edge T are arranged side by side in the tire circumferential direction.

[0056] In this case, the ground contact edge T is the maximum width position in the tire width direction at the contact surface between the pneumatic tire 1 and a flat plate when the pneumatic tire 1 is mounted on a specified rim, pressurized to a specified internal pressure, and placed perpendicular to a flat plate in a stationary state and subjected to a load corresponding to a specified load. The specified load here refers to the "maximum load capacity" specified by JATMA, the maximum value of the "tire load limits at various cold inflation pressures" specified by TRA, or the "load capacity" specified by ETRTO. However, in JATMA, for passenger car tires, the specified internal pressure is 180 kPa and the specified load is 88% of the maximum load capacity. In this embodiment, the ground contact edge T is located on the inner shoulder land portion 21 and the second outer shoulder land portion 25b of the outer shoulder land portion 25.

[0057] The inner shoulder cutout 61 is a cutout 60 arranged in the inner shoulder land portion 21. The inner shoulder cutout 61 has an inner end in the tire width direction that communicates with the inner shoulder circumferential groove 31 and extends a short length from the position of the inner shoulder circumferential groove 31 toward the outside in the tire width direction. The outer end of the inner shoulder cutout 61 in the tire width direction terminates within the inner shoulder land portion 21. A plurality of inner shoulder cutouts 61 are arranged side by side in the tire circumferential direction in the inner shoulder land portion 21. At least some of the inner shoulder sipes 51 of the plurality of inner shoulder sipes 51 arranged in the inner shoulder land portion 21 communicate with the inner shoulder circumferential groove 31 via the inner shoulder cutout 61.

[0058] In this embodiment, the number of inner shoulder cutouts 61 is half the number of inner shoulder sipes 51. The inner shoulder sipes 51 communicate with every other inner shoulder cutout 61 in the tire circumferential direction. Therefore, the inner shoulder sipes 51 are arranged alternately in the tire circumferential direction, with the inner shoulder sipes 51 communicating with the inner shoulder circumferential groove 31 via the inner shoulder cutout 61 and the inner shoulder sipes 51 directly communicating with the inner shoulder circumferential groove 31 without via the inner shoulder cutout 61.

[0059] The inner shoulder sipe 51, which communicates with the inner shoulder circumferential groove 31 via the inner shoulder cutout 61, communicates with the end of the inner shoulder cutout 61 that terminates within the inner shoulder land portion 21, and thereby communicates with the inner shoulder circumferential groove 31 via the inner shoulder cutout 61.

[0060] The inner intermediate sipes 52 are sipes 50 arranged in the inner intermediate land portion 22. The inner intermediate sipes 52 extend in the tire width direction and are arranged between the inner shoulder circumferential groove 31 and the inner center circumferential groove 32, and are connected to both the inner shoulder circumferential groove 31 and the inner center circumferential groove 32. In the inner intermediate land portion 22, a plurality of inner intermediate sipes 52 extending in the tire width direction are arranged side by side in the tire circumferential direction.

[0061] The inner intermediate cutout 62 is a cutout 60 disposed in the inner intermediate land portion 22. The inner intermediate cutout 62 has an inner intermediate cutout 62 that communicates with the inner shoulder circumferential groove 31 and an inner intermediate cutout 62 that communicates with the inner center circumferential groove 32. The inner intermediate cutout 62 that communicates with the inner shoulder circumferential groove 31 has an outer end on the tire width direction that communicates with the inner shoulder circumferential groove 31, extends a short length from the position of the inner shoulder circumferential groove 31 toward the tire width direction inward, and its inner end in the tire width direction terminates within the inner intermediate land portion 22. The inner intermediate cutout 62 that communicates with the inner center circumferential groove 32 has an inner end on the tire width direction that communicates with the inner center circumferential groove 32, extends a short length from the position of the inner center circumferential groove 32 toward the tire width direction outward, and its outer end in the tire width direction terminates within the inner intermediate land portion 22.

[0062] In the inner intermediate land portion 22, inner intermediate cutouts 62 communicating with the inner shoulder circumferential groove 31 and inner intermediate cutouts 62 communicating with the inner center circumferential groove 32 are arranged alternately in the tire circumferential direction. In other words, the inner intermediate cutouts 62 communicating with the inner shoulder circumferential groove 31 and the inner intermediate cutouts 62 communicating with the inner center circumferential groove 32 are arranged in a staggered manner in the tire circumferential direction.

[0063] In the present embodiment, the same number of inner intermediate sipes 52 and inner intermediate cutouts 62 are arranged in the inner intermediate land portion 22. The inner intermediate sipes 52 are arranged alternately in the tire circumferential direction, with the inner intermediate sipes 52 communicating with the inner intermediate cutout 62 on the side communicating with the inner shoulder circumferential groove 31 and the inner intermediate sipes 52 communicating with the inner intermediate cutout 62 on the side communicating with the inner center circumferential groove 32.

[0064] The inner intermediate sipe 52 communicating with the inner intermediate cutout 62 on the side communicating with the inner shoulder circumferential groove 31 has an outer end in the tire width direction communicating with an end of the inner intermediate cutout 62 on the side terminating within the inner intermediate land portion 22, and communicates with the inner shoulder circumferential groove 31 via the inner intermediate cutout 62. Furthermore, the inner end in the tire width direction of the inner intermediate sipe 52 communicating with the inner intermediate cutout 62 on the side communicating with the inner shoulder circumferential groove 31 directly communicates with the inner center circumferential groove 32.

[0065] The inner intermediate sipe 52 communicating with the inner intermediate cutout 62 on the side communicating with the inner center circumferential groove 32 has an inner end in the tire width direction communicating with the end of the inner intermediate cutout 62 on the side terminating within the inner intermediate land portion 22, and communicates with the inner center circumferential groove 32 via the inner intermediate cutout 62. Furthermore, the outer end in the tire width direction of the inner intermediate sipe 52 communicating with the inner intermediate cutout 62 on the side communicating with the inner center circumferential groove 32 directly communicates with the inner shoulder circumferential groove 31.

[0066] The center sipes 53 are sipes 50 arranged in the center land portion 23, and the center cutouts 63 are cutouts 60 arranged in the center land portion 23. In this embodiment, the same number of center sipes 53 and center cutouts 63 are arranged in the center land portion 23. More specifically, the center cutouts 63 have their inner ends in the vehicle mounting direction connected to the inner center circumferential groove 32, extend a short distance from the position of the inner center circumferential groove 32 toward the outer side in the vehicle mounting direction, and terminate within the center land portion 23.

[0067] The center sipe 53 has an inner end in the vehicle mounting direction that communicates with the end of the center cutout 63 that terminates within the center land portion 23, and extends outward in the vehicle mounting direction from the end that communicates with the center cutout 63. Therefore, the center sipe 53 communicates with the inner center circumferential groove 32 via the center cutout 63. The end of the center sipe 53 opposite the end that communicates with the center cutout 63, i.e., the outer end of the center sipe 53 in the vehicle mounting direction, terminates within the center land portion 23. In the center land portion 23, a plurality of center sipes 53 and a plurality of center cutouts 63 that extend in the tire width direction and communicate with each other are arranged side by side in the tire circumferential direction.

[0068] The outer intermediate sipes 54 are sipes 50 arranged in the outer intermediate land portion 24, and the outer intermediate cutouts 64 are cutouts 60 arranged in the outer intermediate land portion 24. In this embodiment, the same number of outer intermediate sipes 54 and outer intermediate cutouts 64 are arranged in the outer intermediate land portion 24. More specifically, the outer intermediate cutouts 64 have their inner ends in the vehicle mounting direction connected to the outer center circumferential groove 33, extend a short distance from the position of the outer center circumferential groove 33 toward the outer side in the vehicle mounting direction, and their outer ends in the vehicle mounting direction terminate within the outer intermediate land portion 24.

[0069] The outer intermediate sipes 54 have their inner ends in the vehicle mounting direction connected to the outer intermediate cutouts 64 at the ends that terminate within the outer intermediate land portion 24, and extend outward in the vehicle mounting direction from the ends that communicate with the outer intermediate cutouts 64. Therefore, the outer intermediate sipes 54 communicate with the outer center circumferential groove 33 via the outer intermediate cutouts 64. The ends of the outer intermediate sipes 54 opposite the ends that communicate with the outer intermediate cutouts 64, i.e., the outer ends of the outer intermediate sipes 54 in the vehicle mounting direction, terminate within the outer intermediate land portion 24. In the outer intermediate land portion 24, a plurality of outer intermediate sipes 54 and a plurality of outer intermediate cutouts 64 that extend in the tire width direction and communicate with each other are arranged side by side in the tire circumferential direction.

[0070] The outer shoulder sipes 55 are sipes 50 arranged in the outer shoulder land portion 25, and the outer shoulder cutouts 65 are cutouts 60 arranged in the outer shoulder land portion 25. More specifically, the outer shoulder sipes 55 are arranged in the second outer shoulder land portion 25b in the outer shoulder land portion 25, and the outer shoulder cutouts 65 are arranged in the first outer shoulder land portion 25a in the outer shoulder land portion 25.

[0071] The outer shoulder cutout 65 arranged in the first outer shoulder land portion 25a has an end portion on the inner side in the vehicle mounting direction that communicates with the outer shoulder circumferential groove 34. The outer shoulder cutout 65 that communicates with the outer shoulder circumferential groove 34 extends a short length outward in the vehicle mounting direction from the position of the outer shoulder circumferential groove 34, and its end portion on the outer side in the vehicle mounting direction terminates within the first outer shoulder land portion 25a. The first outer shoulder land portion 25a has multiple outer shoulder cutouts 65 arranged side by side in the tire circumferential direction, one end of which communicates with the outer shoulder circumferential groove 34 and the other end of which terminates within the first outer shoulder land portion 25a.

[0072] The outer shoulder sipes 55 arranged in the second outer shoulder land portion 25b extend in the tire width direction, straddling the ground contact edge T located on the second outer shoulder land portion 25b, and their inner ends in the tire width direction communicate with the circumferential narrow grooves 40 formed in the outer shoulder land portion 25. In the second outer shoulder land portion 25b, multiple outer shoulder sipes 55 extending in the tire width direction and straddling the ground contact edge T are arranged side by side in the tire circumferential direction.

[0073] Of the sipes 50 and cutouts 60 formed in this manner, the inner intermediate sipe 52, the center sipe 53, the outer intermediate sipe 54, the inner intermediate cutout 62, the center cutout 63, the outer intermediate cutout 64, and the outer shoulder cutout 65 extend in the tire width direction and are inclined in the same direction in the tire circumferential direction with respect to the tire width direction. Furthermore, of the cutouts 60 arranged in the land portion 20, the cutouts 60 that are connected to the sipes 50 have a width in the tire circumferential direction that is within a range of 7 to 13 times the width in the tire circumferential direction of the sipes 50 that are connected to the cutouts 60.

[0074] In this embodiment, each land portion 20 does not have lug grooves extending in the tire width direction, but is formed as a rib extending in the tire circumferential direction. That is, each land portion 20 has a plurality of sipes 50 arranged in the tire width direction and aligned in the tire circumferential direction, without having lug grooves. In particular, the inner shoulder land portion 21, the inner intermediate land portion 22, and the second outer shoulder land portion 25b form sipe-based land portions 20 in which a plurality of sipes 50 extending across the entire contact width of each land portion 20 in the tire width direction are aligned in the tire circumferential direction.

[0075] Figure 3 is a cross-sectional view taken along the line F-F in Figure 2. Note that Figure 3 is a schematic cross-sectional view illustrating, in a single cross-section, the inner shoulder notch 61 and inner intermediate notch 62 that communicate with the inner shoulder circumferential groove 31, and the inner intermediate notch 62 and center notch 63 that communicate with the inner center circumferential groove 32. The inner shoulder circumferential groove 31 and the inner center circumferential groove 32, which are circumferential grooves 30 disposed on the inner side of the tire equatorial plane CL in the vehicle mounting direction, are formed with groove wall angles that have a predetermined relationship with each other. That is, the inner shoulder circumferential groove 31 and the inner center circumferential groove 32 both have groove walls that are inclined in a direction such that the groove width is larger on the opening side of the circumferential groove 30 that faces the tread contact surface 3 than on the groove bottom side, but the inner shoulder circumferential groove 31 and the inner center circumferential groove 32 have inclination angles of the inclined groove walls that have a predetermined relationship.

[0076] Specifically, of a pair of groove walls 31a facing each other in the tire width direction, the groove wall angle A relative to the tire radial direction of the groove wall 31a located closer to the inner side in the vehicle mounting direction and the groove wall angle B relative to the tire radial direction of the groove wall 31a located closer to the outer side in the vehicle mounting direction satisfy the relationship A > B. Furthermore, the groove wall angle A of the groove wall 31a located closer to the inner side in the vehicle mounting direction of the inner shoulder circumferential groove 31 is within a range of 13° to 20°, and the groove wall angle B of the groove wall 31a located closer to the outer side in the vehicle mounting direction is within a range of 8° to 12°.

[0077] The inner center circumferential groove 32 has a pair of groove walls 32a opposing each other in the tire width direction, and the groove wall angle C relative to the tire radial direction of the groove wall 32a located closer to the inside in the vehicle mounting direction and the groove wall angle D relative to the tire radial direction of the groove wall 32a located closer to the outside in the vehicle mounting direction are both within a range of 8° to 12°. Furthermore, the inner center circumferential groove 32 has the groove wall angle C of the groove wall 32a located closer to the inside in the vehicle mounting direction and the groove wall angle D of the groove wall 32a located closer to the outside in the vehicle mounting direction satisfying the relationship -2°≦D−C≦2°.

[0078] In the inner shoulder circumferential groove 31 and the inner center circumferential groove 32, a groove wall angle B of the groove wall 31a located outward in the vehicle mounting direction in the inner shoulder circumferential groove 31 and a groove wall angle C of the groove wall 32a located inward in the vehicle mounting direction in the inner center circumferential groove 32 satisfy the relationship -1°≦B−C≦1°. Furthermore, it is preferable that the groove wall angle B of the groove wall 31a located outward in the vehicle mounting direction in the inner shoulder circumferential groove 31 and the groove wall angle C of the groove wall 32a located inward in the vehicle mounting direction in the inner center circumferential groove 32 satisfy the relationship B<C.

[0079] Note that, when the circumferential grooves 30 are chamfered at their opening portions facing the tread contact surface 3, the groove wall angles of these circumferential grooves 30 are defined by the angles of the groove walls excluding the chamfering. That is, the circumferential grooves 30 may be chamfered, for example, by 1.0 mm or less, at their opening portions facing the tread contact surface 3. In this embodiment as well, the circumferential grooves 30 are chamfered at their opening portions facing the tread contact surface 3, and the groove wall angles A, B, C, and D are the groove wall angles of the groove walls other than the portions where the chamfering is formed.

[0080] 4 is a detailed view of a portion of the tread portion 2 shown in FIG. 2 that is located on the inner side of the tire equatorial plane CL in the vehicle mounting direction. In this embodiment, the four circumferential grooves 30 have groove widths that narrow from the inner side to the outer side in the vehicle mounting direction. Therefore, the inner shoulder circumferential groove 31 and the inner center circumferential groove 32 have a groove width W1 of the inner shoulder circumferential groove 31 and a groove width W2 of the inner center circumferential groove 32 that satisfy the relationship W2<W1. It is preferable that the groove width W1 of the inner shoulder circumferential groove 31 and the groove width W2 of the inner center circumferential groove 32 satisfy the relationship 1.0≦W1 / W2≦1.2.

[0081] Furthermore, the cutouts 60 arranged in each land portion 20 are formed to have a predetermined length in the tire width direction. Specifically, the inner shoulder cutouts 61 arranged in the inner shoulder land portion 21 have a maximum length Dc1 in the tire width direction that is within the range of 0.10≦Dc1 / Wb1≦0.15, where Dc1 / Wb1 is the contact width Wb1 of the inner shoulder land portion 21. In this case, the contact width Wb1 of the inner shoulder land portion 21 is the distance in the tire width direction between the inner shoulder circumferential groove 31 that defines the inner part of the inner shoulder land portion 21 in the tire width direction, and the contact edge T located on the inner shoulder land portion 21.

[0082] Furthermore, of the inner intermediate cutouts 62 arranged in the inner intermediate land portion 22, the inner intermediate cutouts 62 that communicate with the inner shoulder circumferential groove 31 have a maximum length Dc2 in the tire width direction that is within a range of 0.35≦Dc2 / Wb2≦0.45, relative to the ground contact width Wb2 of the inner intermediate land portion 22. In this case, the ground contact width Wb2 of the inner intermediate land portion 22 is the distance in the tire width direction between the inner center circumferential groove 32 that defines the inner part of the inner intermediate land portion 22 in the tire width direction and the inner shoulder circumferential groove 31 that defines the outer part of the inner intermediate land portion 22 in the tire width direction.

[0083] Furthermore, the relationship between the maximum length Dc2 in the tire width direction of the inner intermediate cutout 62 that communicates with the inner shoulder circumferential groove 31 and the maximum length Dc3 in the tire width direction of the inner intermediate cutout 62 that communicates with the inner center circumferential groove 32 for the inner intermediate cutout 62 arranged in the inner intermediate land portion 22 is within the range of 1.1≦Dc2 / Dc3≦1.5.

[0084] Of the land portions 20 in which the cutout portions 60 formed as described above are arranged, the inner shoulder sipe 51, which is the sipe 50 arranged in the inner shoulder land portion 21, is a three-dimensional sipe having a three-dimensional shape. On the other hand, the inner intermediate sipe 52, which is the sipe 50 arranged in the inner intermediate land portion 22, is a two-dimensional sipe having a two-dimensional shape.

[0085] FIG. 5 is an F-F cross-sectional view of FIG. 2 and is an explanatory diagram of a cutout 60 communicating with the circumferential groove 30. Similar to FIG. 3, FIG. 5 is a schematic cross-sectional view illustrating, in a single cross-sectional view, the inner shoulder cutout 61 and inner intermediate cutout 62 communicating with the inner shoulder circumferential groove 31, and the inner intermediate cutout 62 and center cutout 63 communicating with the inner center circumferential groove 32. The cutouts 60 arranged in each land portion 20 are also formed to a predetermined depth in the tire radial direction. Specifically, the inner shoulder cutout 61 arranged in the inner shoulder land portion 21 has a maximum tire radial depth h1, where h1 is the maximum depth Hs of the inner shoulder circumferential groove 31 to which the inner shoulder cutout 61 communicates, within a range of 0.45≦h1 / Hs≦0.55.

[0086] Furthermore, among the inner intermediate cutouts 62 arranged in the inner intermediate land portion 22, the inner intermediate cutouts 62 that communicate with the inner shoulder circumferential groove 31 have a maximum depth h2 in the tire radial direction, relative to the maximum depth Hs of the inner shoulder circumferential groove 31, which is within the range of 0.55≦h2 / Hs≦0.65.

[0087] Furthermore, for the inner intermediate cutout 62 arranged in the inner intermediate land portion 22, the relationship between the maximum depth h2 in the tire radial direction of the inner intermediate cutout 62 communicating with the inner shoulder circumferential groove 31 and the maximum depth h3 in the tire radial direction of the inner intermediate cutout 62 communicating with the inner center circumferential groove 32 is within the range of 0.99≦h2 / h3≦1.01.

[0088] When mounting the pneumatic tire 1 according to this embodiment on a vehicle, the pneumatic tire 1 is mounted on a rim wheel, filled with air, and mounted in an inflated state. Since the mounting direction of the pneumatic tire 1 according to this embodiment relative to the vehicle is specified, the tire is mounted on the vehicle in the specified direction. That is, the tire is mounted on the vehicle in the direction specified by the mounting direction indicator on the sidewall portion 8. As a result, the pneumatic tire 1 is mounted on the vehicle so that the side on which the inner shoulder circumferential groove 31, which connects the inner shoulder cutout 61 and the inner intermediate cutout 62, is located is positioned on the inner side in the vehicle mounting direction, and the side on which the circumferential narrow groove 40 is located is positioned on the outer side in the vehicle mounting direction.

[0089] When a vehicle equipped with the pneumatic tire 1 travels, the pneumatic tire 1 rotates while the lower part of the tread contact surface 3 of the tread portion 2 comes into contact with the road surface. When a vehicle equipped with the pneumatic tire 1 travels on a dry road surface, the vehicle travels by transmitting driving force and braking force to the road surface and generating turning force mainly due to the frictional force between the tread contact surface 3 and the road surface.

[0090] Furthermore, when traveling on a wet road surface, water between the tread contact surface 3 and the road surface enters grooves such as the circumferential grooves 30 and the sipes 50, and these grooves drain the water between the tread contact surface 3 and the road surface while traveling. This makes it easier for the tread contact surface 3 to make contact with the road surface, and the frictional force between the tread contact surface 3 and the road surface enables the vehicle to travel.

[0091] On the other hand, grooves such as the circumferential grooves 30 formed in the tread contact surface 3 can also be a cause of noise generation when the pneumatic tire 1 rotates. In other words, when the pneumatic tire 1 rotates, the tread portion 2 elastically deforms as it comes into contact with the road surface, and the grooves elastically deform together with the tread portion 2, causing the air in the grooves to vibrate and generating air column resonance. When the pneumatic tire 1 rotates, noise is generated due to air column resonance occurring in the grooves in this way.

[0092] In contrast, in the present embodiment, the groove wall angle A of the groove wall 31 a of the inner shoulder circumferential groove 31 located closer to the inside in the vehicle mounting direction and the groove wall angle B of the groove wall 31 a located closer to the outside in the vehicle mounting direction satisfy the relationship A > B. In other words, because the groove wall angle A of the inner shoulder circumferential groove 31 is larger, the volume of the inner shoulder circumferential groove 31 is smaller than when the magnitude of the groove wall angle A is equal to or smaller than the groove wall angle B. As a result, the amount of air in the inner shoulder circumferential groove 31 is reduced, and even if the inner shoulder circumferential groove 31 elastically deforms and the air in the inner shoulder circumferential groove 31 vibrates, the small amount of air can reduce the volume of air column resonance in the inner shoulder circumferential groove 31. This can improve NV performance.

[0093] On the other hand, since the groove wall angle B of the groove wall 31a of the inner shoulder circumferential groove 31 located toward the outer side in the vehicle mounting direction is within a range of 8° to 12°, the volume of the inner shoulder circumferential groove 31 can be prevented from becoming too small. This ensures the drainage performance of the inner shoulder circumferential groove 31 and thereby ensures wet performance. Furthermore, since the groove wall angle A of the inner shoulder circumferential groove 31 is within a range of 13° to 20°, the volume of the inner shoulder circumferential groove 31 can be reduced to an appropriate size that does not impair drainage performance. This ensures the drainage performance of the inner shoulder circumferential groove 31 and reduces the volume of air column resonance in the inner shoulder circumferential groove 31.

[0094] Furthermore, since the groove wall angle C and groove wall angle D of the inner center circumferential groove 32 are both within the range of 8° to 12°, the volume of the inner center circumferential groove 32 can be prevented from becoming too small. This ensures the drainage performance of the inner center circumferential groove 32 and the wet performance. As a result, it is possible to achieve both NV performance and wet performance.

[0095] Furthermore, the groove wall angle B of the inner shoulder circumferential groove 31 and the inner center circumferential groove 32 satisfy the relationship of -1°≦B−C≦1°, so that the volume of the inner shoulder circumferential groove 31 can be appropriately suppressed and the volume of the inner center circumferential groove 32 can be appropriately secured. As a result, both NV performance and wet performance can be achieved.

[0096] Furthermore, when the groove wall angle B of the inner shoulder circumferential groove 31 and the groove wall angle C of the inner center circumferential groove 32 satisfy the relationship B<C, it is possible to prevent the volume of the inner center circumferential groove 32 from becoming too large. This also makes it possible to reduce the volume of air column resonance in the inner center circumferential groove 32. As a result, it is possible to more reliably achieve both NV performance and wet performance.

[0097] Furthermore, since the groove wall angle C and the groove wall angle D of the inner center circumferential groove 32 satisfy the relationship of -2°≦D−C≦2°, the volume of the inner center circumferential groove 32 does not become too large, and an appropriate volume can be ensured for the inner center circumferential groove 32. As a result, it is possible to more reliably achieve both NV performance and wet performance.

[0098] Furthermore, the groove width W1 of the inner shoulder circumferential groove 31 and the groove width W2 of the inner center circumferential groove 32 satisfy the relationship W2<W1, so that both NV performance and wet performance can be achieved. In other words, the groove width W1 of the inner shoulder circumferential groove 31 is wider than the groove width W2 of the inner center circumferential groove 32, so that the volume of the inner shoulder circumferential groove 31, which has a large groove wall angle A, can be prevented from becoming too small. This ensures the drainage performance of the inner shoulder circumferential groove 31, which is prone to becoming small in volume due to a large groove wall angle A.

[0099] Furthermore, by making the groove width W2 of the inner center circumferential groove 32 narrower than the groove width W1 of the inner shoulder circumferential groove 31, the volume of the inner center circumferential groove 32 can be minimized. This also makes it possible to reduce the volume of air column resonance in the inner center circumferential groove 32. As a result, it is possible to more reliably achieve both NV performance and wet performance.

[0100] Furthermore, the groove width W1 of the inner shoulder circumferential groove 31 and the groove width W2 of the inner center circumferential groove 32 satisfy the relationship 1.0≦W1 / W2≦1.2, so the volume of the inner shoulder circumferential groove 31 can be appropriately reduced. That is, if the groove width W1 of the inner shoulder circumferential groove 31 and the groove width W2 of the inner center circumferential groove 32 satisfy 1.0 > W1 / W2, the groove width W1 of the inner shoulder circumferential groove 31 may be too narrow. In this case, the volume of the inner shoulder circumferential groove 31 may be too small, which may make it difficult to ensure the drainage performance of the inner shoulder circumferential groove 31. Furthermore, if the groove width W1 of the inner shoulder circumferential groove 31 and the groove width W2 of the inner center circumferential groove 32 satisfy W1 / W2 > 1.2, the groove width W1 of the inner shoulder circumferential groove 31 may be too wide. In this case, even if the groove wall angle A of the inner shoulder circumferential groove 31 is increased, it becomes difficult to reduce the volume of the inner shoulder circumferential groove 31, which may make it difficult to suppress the volume of air column resonance in the inner shoulder circumferential groove 31.

[0101] In contrast, when the groove width W1 of the inner shoulder circumferential groove 31 and the groove width W2 of the inner center circumferential groove 32 satisfy the relationship 1.0≦W1 / W2≦1.2, the volume of the inner shoulder circumferential groove 31 can be appropriately reduced by increasing the groove wall angle A while preventing the volume of the inner shoulder circumferential groove 31 from becoming too small. This ensures the drainage performance of the inner shoulder circumferential groove 31 while reducing the volume of air column resonance in the inner shoulder circumferential groove 31. As a result, it is possible to more reliably achieve both NV performance and wet performance.

[0102] Furthermore, since the sipes 50 are arranged in the inner shoulder land portion 21 and the inner intermediate land portion 22, drainage performance can be ensured by the sipes 50 without reducing the rigidity of the inner shoulder land portion 21 and the inner intermediate land portion 22, which are arranged on both sides in the tire width direction of the inner shoulder circumferential groove 31. As a result, it is possible to achieve both NV performance and wet performance, and by ensuring the rigidity of the land portion 20, it is possible to improve wear resistance.

[0103] Furthermore, the sipes 50 arranged in the inner shoulder land portion 21, the inner intermediate land portion 22, and the center land portion 23 have sipes 50 that communicate with the circumferential grooves 30 via the cutouts 60. This ensures the rigidity of the land portion 20 while improving the flow of water between the sipes 50 and the circumferential grooves 30 via the cutouts 60, thereby improving drainage. As a result, it is possible to achieve both NV performance and wet performance, and improve wear resistance.

[0104] Furthermore, the maximum length Dc1 of the inner shoulder cutout 61, relative to the contact width Wb1 of the inner shoulder land portion 21, is within the range of 0.10≦Dc1 / Wb1≦0.15, and the maximum length Dc2 of the inner intermediate cutout 62 communicating with the inner shoulder circumferential groove 31, relative to the contact width Wb2 of the inner intermediate land portion 22, is within the range of 0.35≦Dc2 / Wb2≦0.45. Therefore, drainage performance can be ensured without reducing the rigidity of the inner shoulder land portion 21 or the inner intermediate land portion 22.

[0105] In other words, if the maximum length Dc1 of the inner shoulder cutout 61 relative to the ground contact width Wb1 of the inner shoulder land portion 21 satisfies 0.10 > Dc1 / Wb1, the length of the inner shoulder cutout 61 is too short, and it may be difficult to improve drainage even if the inner shoulder cutout 61 is provided in the inner shoulder land portion 21. Similarly, if the maximum length Dc2 of the inner intermediate cutout 62 communicating with the inner shoulder circumferential groove 31 relative to the ground contact width Wb2 of the inner intermediate land portion 22 satisfies 0.35 > Dc2 / Wb2, the length of the inner intermediate cutout 62 is too short, and it may be difficult to improve drainage even if the inner intermediate cutout 62 is provided in the inner intermediate land portion 22.

[0106] Furthermore, if the maximum length Dc1 of the inner shoulder cutout 61 is such that Dc1 / Wb1 > 0.15 relative to the contact width Wb1 of the inner shoulder land portion 21, the length of the inner shoulder cutout 61 is too long, which reduces the rigidity of the inner shoulder land portion 21 and may make it difficult to ensure NV performance and wear resistance. Similarly, if the maximum length Dc2 of the inner intermediate cutout 62 communicating with the inner shoulder circumferential groove 31 is such that Dc2 / Wb2 > 0.45 relative to the contact width Wb2 of the inner intermediate land portion 22, the length of the inner intermediate cutout 62 is too long, which may make it difficult to ensure NV performance and wear resistance.

[0107] In contrast to this, when the maximum length Dc1 of the inner shoulder cutout 61 is within the range of 0.10≦Dc1 / Wb1≦0.15 relative to the contact width Wb1 of the inner shoulder land portion 21, or when the maximum length Dc2 of the inner intermediate cutout 62 communicating with the inner shoulder circumferential groove 31 is within the range of 0.35≦Dc2 / Wb2≦0.45 relative to the contact width Wb2 of the inner intermediate land portion 22, drainage can be ensured by the inner shoulder cutout 61 and the inner intermediate cutout 62 without reducing the rigidity of the inner shoulder land portion 21 and the inner intermediate land portion 22. As a result, wet performance can be improved while ensuring NV performance and wear resistance.

[0108] Furthermore, because the relationship between the maximum length Dc2 of the inner intermediate cutout 62 communicating with the inner shoulder circumferential groove 31 and the maximum length Dc3 of the inner intermediate cutout 62 communicating with the inner center circumferential groove 32 is within the range of 1.1≦Dc2 / Dc3≦1.5, it is possible to facilitate water flow toward the inner shoulder circumferential groove 31 while suppressing imbalance in the rigidity of the inner intermediate land portion 22 on both sides in the tire width direction. This makes it possible to facilitate water flow toward the inner shoulder circumferential groove 31, which has a wider groove width, while suppressing deterioration in wear resistance due to imbalance in the rigidity of the inner intermediate land portion 22, thereby improving drainage. As a result, it is possible to improve wet performance while ensuring wear resistance.

[0109] Furthermore, the maximum depth h1 of the inner shoulder cutout 61, relative to the maximum depth Hs of the inner shoulder circumferential groove 31, is within the range of 0.45≦h1 / Hs≦0.55, and the maximum depth h2 of the inner intermediate cutout 62 communicating with the inner shoulder circumferential groove 31, relative to the maximum depth Hs of the inner shoulder circumferential groove 31, is within the range of 0.55≦h2 / Hs≦0.65. Therefore, drainage performance can be ensured without reducing the rigidity of the inner shoulder land portion 21 or the inner intermediate land portion 22.

[0110] In other words, when the maximum depth h1 of the inner shoulder cutout 61 and the maximum depth Hs of the inner shoulder circumferential groove 31 satisfy the relationship 0.45 > h1 / Hs, the depth of the inner shoulder cutout 61 is too shallow, and it may be difficult to improve drainage even if the inner shoulder cutout 61 is provided in the inner shoulder land portion 21. Similarly, when the maximum depth h2 of the inner intermediate cutout 62 communicating with the inner shoulder circumferential groove 31 satisfies the relationship 0.55 > h2 / Hs, the depth of the inner intermediate cutout 62 is too shallow, and it may be difficult to improve drainage even if the inner intermediate cutout 62 is provided in the inner intermediate land portion 22.

[0111] Furthermore, if the maximum depth h1 of the inner shoulder cutout 61 is relative to the maximum depth Hs of the inner shoulder circumferential groove 31 such that h1 / Hs > 0.55, the inner shoulder cutout 61 is too deep, which reduces the rigidity of the inner shoulder land portion 21 and may make it difficult to ensure the NV performance and wear resistance. Similarly, if the maximum depth h2 of the inner intermediate cutout 62 communicating with the inner shoulder circumferential groove 31 is relative to the maximum depth Hs of the inner shoulder circumferential groove 31 such that h2 / Hs > 0.65, the inner intermediate cutout 62 is too deep, which reduces the rigidity of the inner intermediate land portion 22 and may make it difficult to ensure the NV performance and wear resistance.

[0112] In contrast to this, when the maximum depth h1 of the inner shoulder cutout 61 is within a range of 0.45≦h1 / Hs≦0.55 relative to the maximum depth Hs of the inner shoulder circumferential groove 31, or when the maximum depth h2 of the inner intermediate cutout 62 communicating with the inner shoulder circumferential groove 31 is within a range of 0.55≦h2 / Hs≦0.65 relative to the maximum depth Hs of the inner shoulder circumferential groove 31, drainage performance can be ensured by the inner shoulder cutout 61 and the inner intermediate cutout 62 without reducing the rigidity of the inner shoulder land portion 21 and the inner intermediate land portion 22. As a result, wet performance can be improved while ensuring NV performance and wear resistance.

[0113] Furthermore, because the relationship between the maximum depth h2 of the inner intermediate cutout 62 communicating with the inner shoulder circumferential groove 31 and the maximum depth h3 of the inner intermediate cutout 62 communicating with the inner center circumferential groove 32 is within the range of 0.99≦h2 / h3≦1.01, it is possible to prevent the rigidity of the inner intermediate land portion 22 from becoming uneven on both sides in the tire width direction. This prevents deterioration of wear resistance due to uneven rigidity of the inner intermediate land portion 22, while the inner intermediate cutout 62 makes it easier for water to flow into the inner shoulder circumferential groove 31 and the inner center circumferential groove 32, thereby improving drainage. As a result, it is possible to improve wet performance while ensuring wear resistance.

[0114] Furthermore, the width in the tire circumferential direction of the cutouts 60 to which the sipes 50 are connected is within a range of 7 to 13 times the width in the tire circumferential direction of the sipes 50 that are connected to the cutouts 60, so that it is possible to improve drainage while preventing the rigidity of the land portions 20 from becoming too low. In other words, if the width of the cutouts 60 is less than 7 times the width of the sipes 50, the width of the cutouts 60 is too narrow, and there is a risk that providing the cutouts 60 in the land portions 20 will make it difficult to improve drainage. Furthermore, if the width of the cutouts 60 is more than 13 times the width of the sipes 50, the width of the cutouts 60 is too wide, and there is a risk that the rigidity of the land portions 20 in which the cutouts 60 are arranged will become too low.

[0115] In contrast, when the width of the cutout 60 is within a range of 7 to 13 times the width of the sipe 50, the drainage performance can be improved by the cutout 60 while preventing the rigidity of the land portion 20 where the cutout 60 is arranged from becoming too low. As a result, wet performance can be improved while ensuring wear resistance.

[0116] Furthermore, the inner intermediate cutouts 62 arranged in the inner intermediate land portion 22 are arranged such that the inner intermediate cutouts 62 that communicate with the inner shoulder circumferential groove 31 and the inner intermediate cutouts 62 that communicate with the inner center circumferential groove 32 are alternately arranged in the tire circumferential direction. This makes it possible to distribute the period when the parts of the inner intermediate land portion 22 where the inner intermediate cutouts 62 are arranged come into contact with the ground during vehicle travel, thereby reducing pitch noise. As a result, it is possible to improve NV performance.

[0117] Furthermore, because the inner shoulder sipes 51 arranged in the inner shoulder land portion 21 have a three-dimensional shape, it is possible to arrange the sipes 50 in the inner shoulder land portion 21 while suppressing a decrease in the rigidity of the inner shoulder land portion 21. As a result, it is possible to improve wet performance while ensuring wear resistance.

[0118] Furthermore, the tread portion 2 has a cap tread 4 having a tan δ at 0°C in the range of 0.88 to 0.94 and a rubber hardness in the range of 58 to 63, thereby improving running performance on wet roads while ensuring the rigidity of the land portion 20. As a result, wet performance can be improved while ensuring wear resistance.

[0119] The tread pattern of the tread portion 2 is an asymmetric pattern, and the outer shoulder land portion 25 has a plurality of outer shoulder sipes 55 arranged in the tire circumferential direction, extending in the tire width direction without having lug grooves, so that the outer shoulder sipes 55 can improve drainage while ensuring the rigidity of the outer shoulder land portion 25. As a result, wet performance can be improved while ensuring NV performance and wear resistance.

[0120] Furthermore, since the groove widths of the four circumferential grooves 30 narrow from the inner side to the outer side in the vehicle mounting direction, the groove width of the circumferential grooves 30 on the outer side in the vehicle mounting direction, which tend to leak air column resonance noise to the outside of the vehicle during vehicle operation, can be narrowed. This reduces the volume of air column resonance noise in the circumferential grooves 30, which tend to leak air column resonance noise to the outside of the vehicle, and improves NV performance. Furthermore, since the groove width of the circumferential grooves 30 is wider at positions closer to the inner side in the vehicle mounting direction than at positions closer to the outer side in the vehicle mounting direction, the narrowed groove width of the circumferential grooves 30 on the outer side in the vehicle mounting direction can be compensated for by the circumferential grooves 30 on the inner side in the vehicle mounting direction. This allows the drainage performance improved when the groove width of the circumferential grooves 30 on the outer side in the vehicle mounting direction is narrowed to be compensated for by the circumferential grooves 30 on the inner side in the vehicle mounting direction. As a result, both NV performance and wet performance can be achieved.

[0121] [Modifications] In the above-described embodiment, four circumferential grooves 30 are arranged in the tread portion 2, but the number of circumferential grooves 30 arranged in the tread portion 2 may be other than four. The number of circumferential grooves 30 arranged in the tread portion 2 may be three or five.

[0122] In the above-described embodiment, the inner center circumferential groove 32 adjacent to the inner shoulder circumferential groove 31 arranged on the innermost side in the vehicle mounting direction is located on the inner side of the tire equatorial plane CL in the vehicle mounting direction, but the inner center circumferential groove 32 may be located on a side other than the inner side of the tire equatorial plane CL in the vehicle mounting direction. The inner center circumferential groove 32 may be located on the tire equatorial plane CL, for example. Regardless of the position of the inner center circumferential groove 32, if the groove wall angles A, B, C, and D between the inner shoulder circumferential groove 31 and the inner center circumferential groove 32, which are the two circumferential grooves 30 counting from the inner side in the vehicle mounting direction, satisfy the requirements defined in the above-described embodiment, both NV performance and wet performance can be achieved.

[0123] The above-described embodiments and modified examples may be combined as appropriate. In the above-described embodiments, the pneumatic tire 1 has been used as an example of a tire according to the present invention, but the tire according to the present invention may be a tire other than the pneumatic tire 1. The tire according to the present invention may be, for example, a so-called airless tire that can be used without being filled with gas.

[0124] 6A to 6C are tables showing the results of performance evaluation tests of pneumatic tires. Performance evaluation tests conducted on the above-described pneumatic tire 1 for a conventional pneumatic tire, the pneumatic tire 1 according to the present invention, and a comparative pneumatic tire for comparison with the pneumatic tire 1 according to the present invention will be described below. The performance evaluation tests included tests on wet grip performance, NV performance, and abrasion resistance.

[0125] The performance evaluation test was carried out by mounting a pneumatic tire 1 having a tire nominal size of 235 / 50R18 97W as specified by JATMA on a JATMA standard rim wheel having a rim size of 18 x 7.5J, mounting the test tire on a 2WD minivan-type evaluation vehicle, adjusting the air pressure to 230 kPa for the front wheels and 240 kPa for the rear wheels, and running the evaluation vehicle.

[0126] The evaluation method for each test item was as follows: for wet grip performance, a test vehicle equipped with a test tire was driven by a test driver on a test course with a road surface conforming to R117, and the wet grip performance was measured based on the μ-s characteristics. The wet grip performance was evaluated by expressing the measured wet grip performance as an index, with the conventional example described below being 100, and the higher the index, the better the wet grip performance. Note that if the wet grip performance index is 98 or higher, it is considered that the same level as the conventional example is maintained and that wet grip performance comparable to the conventional example is ensured.

[0127] The NV performance was evaluated by having a test driver drive an evaluation vehicle fitted with the test tires around a test course, and measuring the noise energy at the inner ear of the driver's seat. The NV performance was evaluated by expressing the reciprocal of the measured noise energy as an index, with the conventional example (described later) set at 100, and the higher the index, the better the NV performance.

[0128] The wear resistance was evaluated by measuring the groove depth after a road test of 8,000 km was conducted by a test driver using an evaluation vehicle fitted with the test tire. The wear resistance was evaluated by expressing the measured groove depth as an index, with the conventional example described below being set at 100, and the higher the index, the better the wear resistance.

[0129] The performance evaluation test was conducted on 21 types of pneumatic tires, including a Conventional Example pneumatic tire which is an example of a conventional pneumatic tire, Examples 1 to 17 which are pneumatic tire 1 according to the present invention, and Comparative Examples 1 to 3 which are pneumatic tires compared with pneumatic tire 1 according to the present invention. Of these, the Conventional Example and Comparative Example 3 have the same groove wall angle A and groove wall angle B of the inner shoulder circumferential groove. Furthermore, Comparative Examples 1 and 2 have the groove wall angle A of the inner shoulder circumferential groove which is smaller than groove wall angle B.

[0130] In contrast, in all of Examples 1 to 17, which are examples of the pneumatic tire 1 according to the present invention, the groove wall angle A of the inner shoulder circumferential groove 31 is larger than the groove wall angle B. Furthermore, the pneumatic tires 1 according to Examples 1 to 17 are different from one another in the groove wall angles A and B of the inner shoulder circumferential groove 31, the groove wall angles C and D of the inner center circumferential groove 32, the comparison between the groove width W1 of the inner shoulder circumferential groove 31 and the groove width W2 of the inner center circumferential groove 32, the grooves arranged in the inner shoulder land portion 21 and the inner intermediate land portion 22, the communication between the sipes 50 and the cutouts 60 in the inner shoulder land portion 21 and the inner intermediate land portion 22, the length and depth of the cutouts 60, the width of the cutouts 60 relative to the width of the sipes 50, the shape of the sipes 50 in the inner shoulder land portion 21, the tan δ and rubber hardness of the cap tread 4, and the relative relationship between the groove widths of the circumferential grooves.

[0131] 6A to 6C, performance evaluation tests were conducted using these pneumatic tires 1. As a result, it was found that the pneumatic tires 1 according to Examples 1 to 17 were able to improve NV performance while minimizing the deterioration of wet grip performance compared to the conventional tire, and were able to improve both wet grip performance and NV performance compared to the comparative example. In other words, the pneumatic tires 1 according to Examples 1 to 17 were able to achieve both NV performance and wet performance.

[0132] The present disclosure includes the following inventions: Invention [1] A tire includes a plurality of circumferential grooves extending in a circumferential direction, wherein, among the plurality of circumferential grooves, the innermost circumferential groove in the vehicle mounting direction is an inner shoulder circumferential groove, and the circumferential groove adjacent to the inner shoulder circumferential groove in the tire width direction is an inner center circumferential groove, wherein the inner shoulder circumferential groove is located on the inner side in the vehicle mounting direction with respect to the tire equatorial plane, and the inner center circumferential groove is located on the inner side in the vehicle mounting direction with respect to the tire equatorial plane or is located on the tire equatorial plane, and the inner shoulder circumferential groove has a pair of groove walls opposing each other in the tire width direction, wherein a groove wall angle A relative to the tire radial direction of the groove wall located on the inner side in the vehicle mounting direction and a groove wall angle B relative to the tire radial direction of the groove wall located on the outer side in the vehicle mounting direction satisfy the relationship A > B, and the groove wall angle A is in a range of 13° to 20° and the groove wall angle B is in a range of 8° to 12°, A tire characterized in that, of a pair of groove walls opposing in the tire width direction, the inner center circumferential groove has a groove wall angle C relative to the tire radial direction of the groove wall located inward in the vehicle mounting direction, and a groove wall angle D relative to the tire radial direction of the groove wall located outward in the vehicle mounting direction, both within a range of 8° to 12°. Invention [2] The tire according to Invention [1], wherein the groove wall angle B of the inner shoulder circumferential groove and the groove wall angle C of the inner center circumferential groove satisfy the relationship of -1°≦B−C≦1°. Invention [3] The tire according to Invention [1] or Invention [2], wherein the groove wall angle B of the inner shoulder circumferential groove and the groove wall angle C of the inner center circumferential groove satisfy the relationship of B<C. Invention [4] The tire according to any one of Inventions [1] to [3], wherein the groove wall angle C and the groove wall angle D of the inner center circumferential groove satisfy the relationship of -2°≦D−C≦2°. Invention [5] The tire according to any one of Inventions [1] to [4], wherein the inner shoulder circumferential groove and the inner center circumferential groove have a groove width W1 of the inner shoulder circumferential groove and a groove width W2 of the inner center circumferential groove that satisfy the relationship W2<W1.The tire according to any one of Inventions [1] to [6], further comprising a plurality of land portions defined by the circumferential grooves, wherein sipes are arranged in an inner shoulder land portion, the inner shoulder land portion being the land portion defined on an inner side in the tire width direction by the inner shoulder circumferential groove, and an inner intermediate land portion being the land portion defined on both sides in the tire width direction by the inner shoulder circumferential groove and the inner center circumferential groove. Invention [8] A tire according to invention [7], wherein the sipes arranged in the inner intermediate land portion communicate with both the inner shoulder circumferential groove and the inner center circumferential groove, and include sipes that communicate with the inner shoulder circumferential groove via cutouts and sipes that communicate with the inner center circumferential groove via cutouts, the sipes arranged in the inner shoulder land portion extend in the tire width direction across the ground contact edge and communicate with the inner shoulder circumferential groove, and at least some of the plurality of sipes arranged in the inner shoulder land portion communicate with the inner shoulder circumferential groove via cutouts, and a sipe that communicates with the inner center circumferential groove via cutouts is arranged in a center land portion, which is a land portion that is located on the opposite side of the inner intermediate land portion in the tire width direction from the inner center circumferential groove, and is defined by the inner center circumferential groove, among the plurality of land portions.Invention [9] The tire according to invention [8], wherein the cutout portion disposed in the inner shoulder land portion and communicating with the inner shoulder circumferential groove has a maximum length Dc1 in the tire width direction, where the maximum length Dc1 is a relationship with the ground contact width Wb1 of the inner shoulder land portion, in a range of 0.10≦Dc1 / Wb1≦0.15; the cutout portion disposed in the inner intermediate land portion and communicating with the inner shoulder circumferential groove has a maximum length Dc2 in the tire width direction, where the maximum length Dc2 is a relationship with the ground contact width Wb2 of the inner intermediate land portion, in a range of 0.35≦Dc2 / Wb2≦0.45; and the relationship between the maximum length Dc2 in the tire width direction of the cutout portion disposed in the inner intermediate land portion and communicating with the inner shoulder circumferential groove and the maximum length Dc3 in the tire width direction of the cutout portion disposed in the inner intermediate land portion and communicating with the inner center circumferential groove is in a range of 1.1≦Dc2 / Dc3≦1.5. Invention

[10] The tire according to Invention [8] or Invention [9], wherein the cutouts disposed in the inner shoulder land portion and communicating with the inner shoulder circumferential groove have a maximum depth h1 in the tire radial direction, relative to a maximum depth Hs of the inner shoulder circumferential groove, in a range of 0.45≦h1 / Hs≦0.55; the cutouts disposed in the inner intermediate land portion and communicating with the inner shoulder circumferential groove have a maximum depth h2 in the tire radial direction, relative to a maximum depth Hs of the inner shoulder circumferential groove, in a range of 0.55≦h2 / Hs≦0.65; and the relationship between the maximum depth h2 in the tire radial direction of the cutouts disposed in the inner intermediate land portion and communicating with the inner shoulder circumferential groove and the maximum depth h3 in the tire radial direction of the cutouts disposed in the inner intermediate land portion and communicating with the inner center circumferential groove is within a range of 0.99≦h2 / h3≦1.01. Invention

[11] The tire according to any one of Inventions [8] to

[10] , wherein the width in the tire circumferential direction of the cutout portion to which the sipe is connected is within a range of 7 to 13 times the width in the tire circumferential direction of the sipe that is connected to the cutout portion.Invention

[12] A tire according to any one of Inventions [8] to

[11] , wherein the cutouts arranged in the inner intermediate land portion are arranged such that the cutouts communicating with the inner shoulder circumferential groove and the cutouts communicating with the inner center circumferential groove are alternately arranged in the tire circumferential direction. Invention

[13] A tire according to any one of Inventions [7] to

[12] , wherein the sipes arranged in the inner shoulder land portion have a three-dimensional shape. Invention

[14] A tire according to any one of Inventions [1] to

[13] , wherein the tread portion has a cap tread having a tan δ at 0°C in the range of 0.88 to 0.94 and a rubber hardness in the range of 58 to 63. Invention

[15] A tire according to any one of Inventions [1] to

[14] , wherein four circumferential grooves are arranged, the tread pattern of the tread portion is an asymmetric pattern that is asymmetric on both sides of the tire equatorial plane in the tire width direction, and an outer shoulder land portion that is the land portion located outermost in the vehicle mounting direction among the plurality of land portions has a plurality of sipes that extend in the tire width direction and are arranged side by side in the tire circumferential direction without having lug grooves. Invention

[16] A tire according to Invention

[15] , wherein the four circumferential grooves have a groove width that narrows from the inner side to the outer side in the vehicle mounting direction.

[0133] REFERENCE SIGNS LIST 1 pneumatic tire 2 tread portion 3 tread ground contact surface 4 cap tread 5 shoulder portion 8 sidewall portion 10 bead portion 13 carcass layer 14 belt layer 20 land portion 21 inner shoulder land portion 22 inner intermediate land portion 23 center land portion 24 outer intermediate land portion 25 outer shoulder land portion 25a first outer shoulder land portion 25b second outer shoulder land portion 30 circumferential groove 31 inner shoulder circumferential groove 31a, 32a groove wall 32 inner center circumferential groove 33 outer center circumferential groove 34 outer shoulder circumferential groove 40 circumferential narrow groove 50 sipe 51 inner shoulder sipe 52 inner intermediate sipe 53 center sipe 54 outer intermediate sipe 55 outer shoulder sipe 60 cutout portion 61 inner shoulder cutout portion 62 Inner intermediate cutout 63 Center cutout 64 Outer intermediate cutout 65 Outer shoulder cutout

Claims

1. A tire having a plurality of circumferential grooves extending in a circumferential direction, wherein, among the plurality of circumferential grooves, the innermost circumferential groove in a vehicle mounting direction is an inner shoulder circumferential groove, and the circumferential groove adjacent to the inner shoulder circumferential groove in the tire width direction is an inner center circumferential groove, the inner shoulder circumferential groove is located on the inner side in the vehicle mounting direction with respect to the tire equatorial plane, and the inner center circumferential groove is located on the inner side in the vehicle mounting direction with respect to the tire equatorial plane or is located on the tire equatorial plane, the inner shoulder circumferential groove has a pair of groove walls opposing each other in the tire width direction, wherein a groove wall angle A with respect to the tire radial direction of the groove wall located on the inner side in the vehicle mounting direction and a groove wall angle B with respect to the tire radial direction of the groove wall located on the outer side in the vehicle mounting direction satisfy a relationship A>B, and the groove wall angle A is within a range of 13° to 20° and the groove wall angle B is within a range of 8° to 12°, a groove wall angle C of the inner center circumferential groove relative to the tire radial direction of the groove wall located closer to the inner side in the vehicle mounting direction, and a groove wall angle D of the inner center circumferential groove relative to the tire radial direction of the groove wall located closer to the outer side in the vehicle mounting direction, both of which are within a range of 8° to 12°.

2. The tire according to claim 1, wherein the groove wall angle B of the inner shoulder circumferential groove and the groove wall angle C of the inner center circumferential groove satisfy the relationship: -1°≦B−C≦1°.

3. The tire according to claim 1 or 2, wherein the groove wall angle B of the inner shoulder circumferential groove and the groove wall angle C of the inner center circumferential groove satisfy the relationship B<C.

4. The tire according to claim 1 or 2, wherein the inner center circumferential groove has a groove wall angle C and a groove wall angle D that satisfy the relationship: -2°≦D−C≦2°.

5. The tire according to claim 1 or 2, wherein the inner shoulder circumferential groove and the inner center circumferential groove have a groove width W1 of the inner shoulder circumferential groove and a groove width W2 of the inner center circumferential groove such that W2<W1.

6. The tire according to claim 5, wherein the groove width W1 of the inner shoulder circumferential groove and the groove width W2 of the inner center circumferential groove satisfy the relationship: 1.0≦W1 / W2≦1.

2.

7. A tire as claimed in claim 1, comprising a plurality of land portions defined by the circumferential grooves, and in which sipes are arranged in an inner shoulder land portion, which is a land portion defined on the inside in the tire width direction by the inner shoulder circumferential groove, and in an inner intermediate land portion, which is a land portion defined on both sides in the tire width direction by the inner shoulder circumferential groove and the inner center circumferential groove.

8. A tire as claimed in claim 7, wherein the sipes arranged in the inner intermediate land portion communicate with both the inner shoulder circumferential groove and the inner center circumferential groove, and include a sipe that communicates with the inner shoulder circumferential groove via a cut-out portion and a sipe that communicates with the inner center circumferential groove via a cut-out portion, the sipes arranged in the inner shoulder land portion extend in the tire width direction across the ground contact edge and communicate with the inner shoulder circumferential groove, and at least a part of the plurality of sipes arranged in the inner shoulder land portion communicate with the inner shoulder circumferential groove via a cut-out portion, and a center land portion, which is a land portion located on the opposite side to the side where the inner intermediate land portion is located in the tire width direction with respect to the inner center circumferential groove and is partitioned by the inner center circumferential groove, has a sipe that communicates with the inner center circumferential groove via a cut-out portion arranged therein.

9. A tire as claimed in claim 8, wherein the cutout portion disposed at the inner shoulder land portion and communicating with the inner shoulder circumferential groove has a maximum length Dc1 in the tire width direction in a range of 0.10≦Dc1 / Wb1≦0.15 with respect to the ground contact width Wb1 of the inner shoulder land portion, the cutout portion disposed at the inner intermediate land portion and communicating with the inner shoulder circumferential groove has a maximum length Dc2 in the tire width direction in a range of 0.35≦Dc2 / Wb2≦0.45 with respect to the ground contact width Wb2 of the inner intermediate land portion, and the relationship between the maximum length Dc2 in the tire width direction of the cutout portion disposed at the inner intermediate land portion and communicating with the inner shoulder circumferential groove and the maximum length Dc3 in the tire width direction of the cutout portion disposed at the inner intermediate land portion and communicating with the inner center circumferential groove is within a range of 1.1≦Dc2 / Dc3≦1.

5.

10. A tire as claimed in claim 8 or 9, wherein the cutout portion disposed at the inner shoulder land portion and communicating with the inner shoulder circumferential groove has a maximum depth h1 in the tire radial direction, relative to a maximum depth Hs of the inner shoulder circumferential groove, in a range of 0.45≦h1 / Hs≦0.55; the cutout portion disposed at the inner intermediate land portion and communicating with the inner shoulder circumferential groove has a maximum depth h2 in the tire radial direction, relative to a maximum depth Hs of the inner shoulder circumferential groove, in a range of 0.55≦h2 / Hs≦0.65; and a relationship between the maximum depth h2 in the tire radial direction of the cutout portion disposed at the inner intermediate land portion and communicating with the inner shoulder circumferential groove and the maximum depth h3 in the tire radial direction of the cutout portion disposed at the inner intermediate land portion and communicating with the inner center circumferential groove is within a range of 0.99≦h2 / h3≦1.

01.

11. The tire as described in claim 8, wherein the width in the tire circumferential direction of the cutout portion to which the sipes communicate is within a range of 7 to 13 times the width in the tire circumferential direction of the sipes communicating with the cutout portion.

12. A tire as described in claim 8, wherein the cutouts arranged in the inner intermediate land portion are arranged such that the cutouts communicating with the inner shoulder circumferential groove and the cutouts communicating with the inner center circumferential groove are alternately arranged in the tire circumferential direction.

13. A tire according to claim 7 or 8, wherein the sipe disposed in the inner shoulder land portion has a three-dimensional shape.

14. The tire according to claim 1, wherein the tread portion has a cap tread having a tan δ at 0° C. in the range of 0.88 to 0.94 and a rubber hardness in the range of 58 to 63.

15. A tire as described in claim 7, wherein four circumferential grooves are arranged, the tread pattern of the tread portion is an asymmetric pattern that is asymmetric on both sides of the tire equatorial plane in the tire width direction, and an outer shoulder land portion, which is the land portion located outermost in the vehicle mounting direction among the multiple land portions, has a plurality of sipes arranged side by side in the tire circumferential direction, extending in the tire width direction without having lug grooves.

16. The tire according to claim 15, wherein the four circumferential grooves have a groove width that narrows from the inner side toward the outer side in the vehicle mounting direction.

Images