Tire

Abstract

In order to suppress a decrease in ice performance and to ensure snow performance and wet performance, a pneumatic tire (1) is provided with: a circumferential groove (30) extending along a tire circumferential direction; a cross groove (40) extending along a tire width direction; a land portion (20) divided by the circumferential groove (30) and the cross groove (40); and a circumferential fine groove (50) extending along the tire circumferential direction and disposed in the land portion (20), at least one of the circumferential grooves (30) that divide the land portion (20) in which the circumferential fine groove (50) is disposed is formed in a zigzag shape having long strip portions (32) and short strip portions (33) of relatively different lengths by extending along the tire circumferential direction and undulating in the tire width direction, the circumferential fine groove (50) has long strip portions (50a) and short strip portions (50b) of relatively different lengths by having a change in an extending direction at one or more places within the land portion (20), and an inclination direction of the long strip portions (50a) of the circumferential fine groove (50) with respect to the tire circumferential direction in the tire width direction is in a direction opposite to an inclination direction of the long strip portions (32) of the circumferential groove (30) with respect to the tire circumferential direction in the tire width direction.

Description

TECHNICAL FIELD

[0001] The present application relates to a tire. BACKGROUND

[0002] In a tire attached to a vehicle, grooves are formed in a tread portion for the purpose of securing various performances corresponding to the use plan of the tire, and by designing the shape of the grooves, improvement of the performances is sought. For example, in the pneumatic tire described in Patent Literature 1, by providing a first circumferential main groove extending in a zigzag shape, a second circumferential main groove, and a circumferential auxiliary groove, the performance on snow and the quietness are improved uniformly. Further, in the pneumatic tire described in Patent Literature 2, by providing a circumferential groove extending in a zigzag shape along the tire circumferential direction and a sipe curved and extending along the tire circumferential direction, the driving performance and the braking performance on ice and snow are increased, and the decrease and uneven wear of the drainage performance are suppressed.

[0003] Further, in the pneumatic tire described in Patent Literature 3, by providing curved fine grooves extending in a curved shape at a prescribed circumferential interval in a wide central land portion row, improvement of the braking / driving performance on both wet road surface and ice and snow road surface is sought. Further, in the pneumatic tire described in Patent Literature 4, by forming central transverse grooves having different inclination directions with respect to the tire width direction in a manner that the central transverse grooves cross the central land portion row, and forming a sub groove inclined with respect to the tire circumferential direction in a second land portion row, improvement of each performance of the tire on ice and snow is sought.

[0004] PRIOR ART DOCUMENTS

[0005] PATENT LITERATURE

[0006] Patent Literature 1: Japanese Patent Application Publication No. 2016-2794

[0007] Patent Literature 2: Japanese Patent Application Publication No. 2012-46105

[0008] Patent Literature 3: Japanese Patent Application Publication No. 2006-315433

[0009] Patent Literature 4: International Publication No. 2010 / 008027 SUMMARY

[0010] PROBLEMS TO BE SOLVED BY THE INVENTION

[0011] Here, as the performance required for the grooves formed in the tread portion, the wet performance achieved by ensuring the water drainage performance of the tread portion and the road surface when running on a wet road surface can be cited. Further, in a studless tire that is required to run on a snowy road surface, an icy road surface, the performance on snow, the performance on ice are also important. In order to improve the performance on snow, it is effective to increase the snow column shear force by increasing the area of the grooves formed in the tread portion by connecting the circumferential grooves adjacent in the tire width direction to each other by the cross groove extending in the tire width direction, or by inclining the circumferential groove extending in the tire circumferential direction with respect to the tire circumferential direction. Further, in the case where the area of the grooves is thus increased, the water drainage performance is also improved, and thus the improvement in the wet performance is also effective.

[0012] However, in the case where the area of the grooves is increased, the rigidity of the land portion is decreased, and thus at the time of braking, the land portion collapses, and thus the ground contact area is decreased, and the performance on ice can be decreased. That is, in the case where the area of the grooves is increased, the performance on ice can be decreased. Therefore, it is very difficult to satisfy all of the performance on snow, the wet performance, and the performance on ice.

[0013] The present application has been achieved in view of the above, and aims to provide a tire that can suppress the decrease in the performance on ice and can ensure the performance on snow and the wet performance.

[0014] Technical Solution

[0015] In order to solve the above technical problem and achieve the object, the tire of the present application is characterized by comprising: a plurality of circumferential grooves extending in the tire circumferential direction; a plurality of cross grooves extending in the tire width direction; a plurality of land portions divided by the circumferential grooves and the cross grooves; and a circumferential fine groove extending in the tire circumferential direction and disposed in the land portion, at least one of the circumferential grooves that divide the land portion in which the circumferential fine groove is disposed extends in the tire circumferential direction and undulates in the tire width direction, thereby being formed in a zigzag shape having a long strip portion and a short strip portion having different lengths, the circumferential fine groove has a bending portion in which the extending direction changes at one place or more within the land portion, thereby having a long strip portion and a short strip portion having different lengths, and the inclination direction of the long strip portion of the circumferential fine groove with respect to the tire width direction from the tire circumferential direction is in the opposite direction to the inclination direction of the long strip portion of the circumferential groove with respect to the tire width direction from the tire circumferential direction.

[0016] Further, in the above tire, it is preferable that both of the two circumferential grooves that divide the tire width direction both sides of the land portion in which the circumferential fine groove is provided be formed in a zigzag shape, and the inclination direction of the long portion of the circumferential fine groove with respect to the tire width direction be opposite to the inclination direction of the long portion of the circumferential groove on the inner side in the tire width direction among the two circumferential grooves that divide the tire width direction both sides of the land portion in which the circumferential fine groove is provided.

[0017] Further, in the above tire, it is preferable that at least one end of the circumferential fine groove be open to the cross groove.

[0018] Further, in the above tire, it is preferable that the circumferential fine groove have a change point of groove depth at at least one location within the land portion.

[0019] Further, in the above tire, it is preferable that the inclination of the long portion of the circumferential fine groove with respect to the tire width direction be in a range of 5° or more and 45° or less.

[0020] Further, in the above tire, it is preferable that the inclination of the long portion of the circumferential groove with respect to the tire width direction be in a range of 5° or more and 30° or less.

[0021] Further, in the above tire, it is preferable that the bending angle of at least one of the bending portions of the circumferential fine groove be 90° or more.

[0022] Further, in the above tire, it is preferable that, for the circumferential fine groove, the total length of the long portion of one circumferential fine groove be in a range of 60% or more and 90% or less of the total length of one circumferential fine groove.

[0023] Further, in the above tire, it is preferable that the bending portion of the circumferential fine groove be provided within a range of 40% of the maximum width in the tire width direction of the land portion, with the center of the land portion in the tire width direction in which the circumferential fine groove is provided as the center.

[0024] Further, in the above tire, it is preferable that the groove width of the circumferential groove be in a range of 3.5 mm or more and 12 mm or less, and the groove width of the circumferential fine groove be in a range of 1.5 mm or more and 4 mm or less.

[0025] Further, in the above tire, it is preferable that a plurality of sipes extending along the tire width direction be provided in the land portion.

[0026] Further, in the above tire, it is preferable that the sipe be inclined with respect to the tire circumferential direction in a direction opposite to the inclination direction of the long portion of the circumferential sipe with respect to the tire width direction.

[0027] Effects of Invention

[0028] The tire of the present application has an effect of being able to suppress a decrease in performance on ice and to ensure performance on snow and performance on wet road. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is a meridian cross-sectional view of a pneumatic tire that represents a main part of an embodiment.

[0030] Figure 2 is an A-A view of Figure 1

[0031] Figure 3 is a detailed view of B of Figure 2

[0032] Figure 4 is a detailed view of C of Figure 2

[0033] Figure 5 is a schematic view of a cross section along the extending direction of the circumferential sipe shown in Figure 4

[0034] Figure 6 is a plan view of a land portion provided with a circumferential sipe of a modification example of the pneumatic tire of the embodiment.

[0035] Figure 7 is a graph representing the results of performance evaluation tests of the pneumatic tire. DETAILED DESCRIPTION

[0036] Hereinafter, an embodiment of the tire of the present application will be described in detail based on the drawings. Note that the present application is not limited by the present embodiment. Further, the constituent elements in the following embodiment include those which can be substituted and easily conceived by those skilled in the art or those which are substantially the same.

[0037] [EMBODIMENT]

[0038] In the following description, as one example of the tire of the present application, a pneumatic tire 1 will be described. The pneumatic tire 1 as one example of the tire can be filled with air, an inert gas such as nitrogen, and other gases.

[0039] ​​​​Furthermore, in the following description, the tire radial direction refers to a direction orthogonal to the rotation axis of the pneumatic tire 1, i.e., the tire rotation axis (omitted from the drawing), the tire radial direction inner side refers to the side in the tire radial direction toward the tire rotation axis, and the tire radial direction outer side refers to the side in the tire radial direction away from the tire rotation axis. Furthermore, the tire circumferential direction refers to the circumferential direction with the tire rotation axis as the center axis. Furthermore, the tire width direction refers to a direction parallel to the tire rotation axis, the tire width direction inner side refers to the side in the tire width direction toward the tire equatorial plane (tire equator line) CL, and the tire width direction outer side refers to the side in the tire width direction away from the tire equatorial plane CL. The tire equatorial plane CL refers to a plane orthogonal to the tire rotation axis and passing through the center of the tire width of the pneumatic tire 1, and the position in the tire width direction of the tire equatorial plane CL coincides with the tire width direction center line as the central position in the tire width direction of the pneumatic tire 1. The tire width is the width in the tire width direction of the portions located at the outermost sides of each other, that is, the distance between the portions located at the outermost sides in the tire width direction away from the tire equatorial plane CL. The tire equator line refers to a line located on the tire equatorial plane CL and along the tire circumferential direction of the pneumatic tire 1. Furthermore, in the following description, the tire meridian section refers to the section when the tire is cut by a plane containing the tire rotation axis.

[0040] Figure 1 is a tire meridian sectional view of the main portion of the pneumatic tire 1 according to the embodiment. When observed in the tire meridian section, the pneumatic tire 1 according to the embodiment is provided with a tread portion 2 at the portions becoming the outermost sides in the tire radial direction, and the tread portion 2 has a tread rubber 4 composed of a rubber composition. Furthermore, the surface of the tread portion 2, i.e., the portion contacting the road surface when a vehicle (omitted from the drawing) to which the pneumatic tire 1 is attached is running, is formed as a tread ground surface 3, and the tread ground surface 3 constitutes a portion of the profile of the pneumatic tire 1.

[0041] The shoulder portion 5 is located at both outer side ends of the tread portion 2 in the tire width direction, and a side wall portion 8 is provided at the tire radial direction inner side of the shoulder portion 5. That is, the side wall portion 8 is provided at both sides of the tread portion 2 in the tire width direction. In other words, the side wall portion 8 is provided at both places of both sides of the pneumatic tire 1 in the tire width direction, and forms the portions exposed to the outermost sides in the tire width direction in the pneumatic tire 1.

[0042] The bead portion 10 is located on the tire radial direction inner side of each side wall portion 8 which is located on both sides in the tire width direction. The bead portion 10 is provided on both sides of the tire equatorial plane CL similarly to the side wall portion 8, that is, a pair of bead portions 10 are provided on both sides in the tire width direction of the tire equatorial plane CL. A bead core 11 is provided in each bead portion 10, and a shoulder core 12 is provided on the tire radial direction outer side of the bead core 11. The bead core 11 is a ring-shaped member in which a bead wire which is a steel wire is bundled to be ring-shaped, and the shoulder core 12 is a rubber member which is provided on the tire radial direction outer side of the bead core 11.

[0043] Further, a belt layer 14 is provided in the tread portion 2. The belt layer 14 is composed of a multi-layer structure in which a plurality of belts 141, 142 and a belt cover layer 143 are stacked, and in the present embodiment, two layers of belts 141, 142 are stacked. The belts 141, 142 which constitute the belt layer 14 are composed by coating a plurality of belt cords composed of steel or an organic fiber material such as polyester, rayon, nylon, etc. with a coating rubber and performing rolling processing on the plurality of belt cords, and are defined as having a belt angle which is an inclination angle of the belt cords with respect to the tire circumferential direction within a prescribed range (for example, 20° or more and 55° or less). Further, the belt angles of the two layers of belts 141, 142 are different from each other. Therefore, the belt layer 14 is composed in a so-called bias structure in which the two layers of belts 141, 142 are stacked in a manner such that the inclination directions of the belt cords cross each other. That is, the two layers of belts 141, 142 are provided as so-called crossed belts in which the belt cords which the belts 141, 142 respectively have are provided in a manner such that they cross each other.

[0044] Further, the belt cover layer 143 is composed by coating a plurality of belt cover layer cords composed of steel or an organic fiber material such as polyester, rayon, nylon, etc. with a coating rubber and performing rolling processing on the plurality of belt cover layer cords, and is defined as having a belt angle which is an inclination angle of the belt cover layer cords with respect to the tire circumferential direction within a prescribed range (for example, 0° or more and 10° or less). Further, the belt cover layer 143 is, for example, a belt in which one or a plurality of belt cover layer cords are coated with a coating rubber, and is composed by winding the belt from the tire radial direction outer side of the two layers of belts 141, 142 in a spiral shape around the tire rotation axis.

[0045] A carcass layer 13 in which cords are wrapped radially is continuously provided on the tire radial direction inner side of the belt layer 14 and on the tire equatorial plane CL side of the side wall portion 8. Therefore, the pneumatic tire 1 of the present embodiment is composed as a so-called radial tire. The carcass layer 13 has a single layer structure composed of one ply or a multi-layer structure in which a plurality of plies are stacked, and is ring-shapedly erected between a pair of bead portions 10 which are provided on both sides in the tire width direction to constitute the skeleton of the tire.

[0046] In detail, the carcass layer 13 is provided from one of the pair of bead portions 10 on the both sides in the tire width direction to the other bead portion 10 so as to wrap around the bead core 11 and the chafer core 12 at the bead portion 10 in a manner that the carcass layer 13 is rolled back along the bead core 11 to the outside in the tire width direction. The chafer core 12 becomes a rubber member arranged in a space formed on the outside in the tire radial direction of the bead core 11 by being folded back at the bead portion 10 by the carcass layer 13. Further, the belt layer 14 is arranged on the outside in the tire radial direction of the portion of the carcass layer 13 arranged between the pair of bead portions 10 in the manner described above. Further, the ply of the carcass layer 13 is constituted by coating a plurality of carcass cords made of steel or organic fiber materials such as aramid, nylon, polyester, rayon, etc. with coating rubber and performing calendering processing on the plurality of carcass cords. The angle of the carcass cords constituting the ply with respect to the tire circumferential direction is along the tire meridian direction, and a plurality of the carcass cords are arranged side by side in the tire circumferential direction at an angle.

[0047] A rim cushion rubber 17 constituting a contact surface of the bead portion 10 with respect to the rim flange is arranged on the inside in the tire radial direction and the outside in the tire width direction of the rolled back portion of the bead core 11 and the carcass layer 13 in the bead portion 10. Further, an inner liner 16 is formed along the carcass layer 13 on the inside of the carcass layer 13 or the inside of the pneumatic tire 1. The inner liner 16 forms a tire inner surface 18 on the inside of the pneumatic tire 1.

[0048] Figure 2 is Figure 1 An A-A view of Fig. 1. In the tread portion 2, a plurality of circumferential grooves 30 extending along the tire circumferential direction and a plurality of lateral grooves 40 extending along the tire width direction are formed on the tread ground surface 3, and a plurality of land portions 20 are divided on the surface of the tread portion 2 by the circumferential grooves 30 and the lateral grooves 40. In the present embodiment, four circumferential grooves 30 are formed in a row along the tire width direction. In detail, the circumferential grooves 30 have four grooves including two inner circumferential grooves 31 arranged on both sides of the tire equatorial plane CL in the tire width direction and two outer circumferential grooves 35 each arranged on the outside in the tire width direction of the respective inner circumferential grooves 31. The groove width of these circumferential grooves 30 is in a range of 3.5 mm or more and 12 mm or less, and the groove depth is in a range of 6.0 mm or more and 10.0 mm or less.

[0049] The land portion 20 divided by the circumferential grooves 30 has a center land portion 21, a second land portion 22, and a shoulder land portion 23. The center land portion 21 is the land portion 20 located between the inner circumferential grooves 31, and its both sides in the tire width direction are divided by the inner circumferential grooves 31. Further, the second land portion 22 is the land portion 20 located between the inner circumferential grooves 31 and the outer circumferential grooves 35 adjacent in the tire width direction, and its inner side in the tire width direction is divided by the inner circumferential grooves 31, and its outer side in the tire width direction is divided by the outer circumferential grooves 35. Further, the shoulder land portion 23 is the land portion 20 located outside the outer circumferential grooves 35 in the tire width direction, and its inner side in the tire width direction is divided by the outer circumferential grooves 35. Further, the second land portion 22 and the shoulder land portion 23 are respectively disposed on both sides of the tire equatorial plane CL in the tire width direction.

[0050] Both of the outer circumferential grooves 35 of the four circumferential grooves 30 are formed so as to extend in a straight line shape along the tire circumferential direction. On the other hand, both of the inner circumferential grooves 31 of the four circumferential grooves 30 are formed so as to extend along the tire circumferential direction by at least one of the groove walls on both sides in the groove width direction and to fluctuate in the tire width direction, and thus are formed in a zigzag shape.

[0051] Specifically, when the two inner circumferential grooves 31 are provided as a first inner circumferential groove 31a and a second inner circumferential groove 31b, for the first inner circumferential groove 31a, the groove wall on the outer side in the tire width direction of the groove walls on both sides in the groove width direction is formed in a zigzag shape, and the groove wall on the inner side in the tire width direction is formed so as to extend in a straight line shape along the tire circumferential direction. Further, for the second inner circumferential groove 31b, the entire second inner circumferential groove 31b is formed in a zigzag shape by extending along the tire circumferential direction and fluctuating in the tire width direction. Therefore, for the second inner circumferential groove 31b, the groove width is maintained constant, and the groove walls on both sides in the groove width direction are each formed in a zigzag shape.

[0052] Further, the cross grooves 40 have a center cross groove 41, a curved cross groove 42, a communication cross groove 44, and a shoulder cross groove 45. The center cross groove 41 is disposed between the two inner circumferential grooves 31. The center cross groove 41 extends along the tire width direction, and is inclined to the tire circumferential direction with respect to the tire width direction, and both ends thereof are respectively opened to the inner circumferential grooves 31. Therefore, the center land portion 21 divided by the inner circumferential grooves 31 and the center cross groove 41 forms a block-shaped land portion 20, and both sides in the tire width direction of the block-shaped land portion 20 are divided by the inner circumferential grooves 31, and both sides in the tire circumferential direction thereof are divided by the center cross groove 41.

[0053] Further, the curved sipe 42 is provided between the first inner side circumferential groove 31a and the outer side circumferential groove 35 adjacent to the first inner side circumferential groove 31a. In other words, the curved sipe 42 is provided in the first second land portion 22a, which is the second land portion 22 located between the first inner side circumferential groove 31a and the outer side circumferential groove 35 among the second land portions 22 provided on both sides in the tire width direction of the tire equatorial plane CL. As such, for the sipe 40, i.e., the curved sipe 42, provided in the land portion 20 divided by the circumferential grooves 30 on both sides in the tire width direction, one end thereof is open to the circumferential groove 30, and the other end thereof is terminated within the land portion 20, and the curved sipe 42 is formed in multiple bends. That is, the curved sipe 42 is a one-side open sipe 40 having one end open to the circumferential groove 30 and the other end not open.

[0054] Specifically, for the curved sipe 42, one end thereof is open to the outer side circumferential groove 35, and the other end thereof is terminated within the first second land portion 22a, and the curved sipe 42 is bent at two places between the end portion on the side open to the outer side circumferential groove 35 and the end portion on the side terminated within the first second land portion 22a. That is, the curved sipe 42 is open to the outer side circumferential groove 35, which is one of the two circumferential grooves 30 dividing both sides in the tire width direction of the first second land portion 22a. The plurality of curved sipes 42 are arranged in the same manner along the tire circumferential direction. Further, for the curved sipe 42, one of the two end portions in the extending direction of the curved sipe 42 is terminated within the first second land portion 22a, and thus the first second land portion 22a is not cut by the curved sipe 42 in the tire circumferential direction. Therefore, the first second land portion 22a is a strip patterned land portion 20 continuously formed in the tire circumferential direction.

[0055] Further, the communication sipe 44 is provided between the second inner side circumferential groove 31b and the outer side circumferential groove 35 adjacent to the second inner side circumferential groove 31b. The communication sipe 44 extends along the tire width direction and is inclined to the tire circumferential direction with respect to the tire width direction, and one end thereof is open to the second inner side circumferential groove 31b, and the other end thereof is open to the outer side circumferential groove 35. As such, the communication sipe 44 provided between the second inner side circumferential groove 31b and the outer side circumferential groove 35 is a sipe 40 that divides the second second land portion 22b, which is the second land portion 22 located between the second inner side circumferential groove 31b and the outer side circumferential groove 35. Therefore, the second second land portion 22b is a block patterned land portion 20 divided by the second inner side circumferential groove 31b and the outer side circumferential groove 35 on both sides in the tire width direction and by the communication sipe 44 on both sides in the tire circumferential direction.

[0056] Further, the shoulder sipe 45 is provided on the tire width direction outer side of the outer side circumferential groove 35 located on both sides of the tire equatorial plane CL in the tire width direction. The shoulder sipe 45 is formed so as to extend in the tire width direction, and the end portion on the inner side in the tire width direction thereof is opened to the outer side circumferential groove 35, and the end portion on the outer side in the tire width direction thereof is terminated at the end portion in the tire width direction of the tread pattern of the tread portion 2, that is, the so-called design end. In this way, the shoulder sipe 45 formed between the outer side circumferential groove 35 and the design end is a sipe 40 that divides the shoulder shoulder portion 23 together with the outer side circumferential groove 35. Therefore, the shoulder shoulder portion 23 is a shoulder portion 20 divided into two blocks by the shoulder sipe 45 in the tire circumferential direction.

[0057] The sipe width of the sipe 40 thus formed is in the range of 3.0 mm or more and 8.0 mm or less, and the sipe depth is in the range of 6.0 mm or more and 9.0 mm or less.

[0058] Further, the circumferential fine groove 50 is provided in the second second shoulder portion 22b located between the second inner side circumferential groove 31b and the outer side circumferential groove 35. The circumferential fine groove 50 is a groove having a sipe width narrower than the sipe width of the circumferential groove 30, and is formed so as to have a sipe width in the range of 1.5 mm or more and 4 mm or less. Further, the sipe depth of the circumferential fine groove 50 is in the range of 3.5 mm or more and 7.0 mm or less.

[0059] The circumferential fine groove 50 extends in the tire circumferential direction and is provided in the second second shoulder portion 22b, and both end portions thereof in the tire circumferential direction are opened to the communicating sipe 44 that divides the second second shoulder portion 22b. The circumferential fine groove 50 is formed so as to extend in the tire circumferential direction and have a portion curved in the tire width direction, and in the present embodiment, the circumferential fine groove 50 is curved at two places, thereby being provided in the second second shoulder portion 22b in a meandering shape.

[0060] Further, the shoulder fine groove 55 extending in the tire circumferential direction is provided in the shoulder shoulder portion 23 located on the outer side in the tire width direction of the outer side circumferential groove 35. The shoulder fine groove 55 extending in the tire circumferential direction has one end portion opened to the shoulder sipe 45 and the other end portion terminated within the shoulder shoulder portion 23. The end portion on the side opened to the shoulder sipe 45 of the shoulder fine groove 55 provided in the shoulder shoulder portion 23 and the shoulder fine groove 55 located on the same side in the tire width direction with respect to the tire equatorial plane CL is an end portion on the same side in the tire circumferential direction. That is, the shoulder fine groove 55 provided in the shoulder shoulder portion 23 divided by the same outer side circumferential groove 35 has the same orientation in the tire circumferential direction.

[0061] Further, for the shoulder fine grooves 55 arranged on one side in the tire width direction of the tire equator CL and the shoulder fine grooves 55 arranged on the other side, the end portions on the side opening toward the shoulder sipe 45 and the end portions on the side ending within the shoulder land portion 23 are end portions on different sides. That is, for the shoulder fine grooves 55 arranged on one side in the tire width direction of the tire equator CL and the shoulder fine grooves 55 arranged on the other side, the tire circumferential directions thereof are opposite directions.

[0062] Further, a plurality of sipe patterns 60 extending in the tire width direction are arranged in each land portion 20. The sipe pattern 60 arranged in the land portion 20 is, for example, arranged in a zigzag shape by extending in the tire width direction and repeatedly bending and undulating in the tire circumferential direction. The end portion of each sipe pattern 60 can end within the land portion 20 or can open toward another groove. For the pneumatic tire 1 of the present embodiment, the sipe pattern 60 is thus arranged in each land portion 20, whereby a studless tire for securing the running performance on an icy and snowy road surface or an all-season tire for securing the running performance in winter is achieved.

[0063] The sipe pattern 60 referred to herein is a sipe pattern in which the land portion 20 in which the sipe is formed is formed in a groove shape, and in the case where the pneumatic tire 1 is mounted on a prescribed rim and under an internal pressure condition of a prescribed internal pressure without load, the wall surfaces constituting the groove do not contact each other, but in the case where the land portion 20 in which the sipe is formed collapses or in the case where the land portion 20 in which the sipe is formed is a portion of the land portion on a flat plate on which a load is applied in the vertical direction, at least a portion of the wall surfaces constituting the groove or the portion provided on the wall surfaces contact each other due to the deformation of the land portion 20. In the present embodiment, the sipe pattern 60 has a groove width of 1.4 mm or less, and a maximum depth from the land portion 3 of 3.5 mm or more and 9.0 mm or less.

[0064] The prescribed rim referred to herein is a "standard rim" prescribed by JATMA, a "Design Rim" prescribed by TRA, or a "Measuring Rim" prescribed by ETRTO. Further, the prescribed internal pressure is the maximum value described in "Maximum Air Pressure" prescribed by JATMA, "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" prescribed by TRA, or "INFLATION PRESSURES" prescribed by ETRTO.

[0065] Further, the sipe 60 can be a so-called three-dimensional sipe, or a two-dimensional sipe. The three-dimensional sipe referred to herein is a sipe 60 having a curved wall surface having an amplitude in the width direction of the sipe 60 in both a cross section normal to the length direction of the sipe 60 (a cross section including the width direction and the depth direction of the sipe 60) and a cross section normal to the depth direction of the sipe 60 (a cross section including the width direction and the length direction of the sipe 60). Further, the two-dimensional sipe is a sipe 60 having a linear wall surface in any cross section normal to the length direction of the sipe 60 (a cross section including the width direction and the depth direction of the sipe 60).

[0066] Figure 3 is Figure 2 A detailed view of the B portion of FIG. 10. The curved sipe 42 provided in the first second land portion 22a and formed to be curved at multiple locations is a sipe 40 having two or more curved portions 43 in which the extending direction changes. In the present embodiment, the curved sipe 42 has two curved portions 43, and has a first curved portion 43a which is the curved portion 43 of the curved sipe 42 located on the outer side of the circumferential groove 35 side, and a second curved portion 43b which is the curved portion 43 of the curved sipe 42 located on the end portion side which terminates within the first second land portion 22a. Thus, the curved sipe 42 has a first extending portion 42a, a second extending portion 42b, and a third extending portion 42c, with the two curved portions 43 as boundaries.

[0067] In detail, the first extending portion 42a is a portion of the curved sipe 42 between the end portion on the side which opens to the outer circumferential groove 35 and the first curved portion 43a. Further, the second extending portion 42b is a portion of the curved sipe 42 between the first curved portion 43a and the second curved portion 43b. Further, the third extending portion 42c is a portion of the curved sipe 42 between the end portion on the side which terminates within the first second land portion 22a, i.e., the termination portion 42d, and the second curved portion 43b.

[0068] Further, for the two curved portions 43 of the curved sipe 42, the curved direction in the groove width direction of the curved sipe 42 is the same direction at the first curved portion 43a and the second curved portion 43b. That is, for the two curved portions 43 of the curved sipe 42, the groove wall of the curved sipe 42 on the inferior angle side of the curve is the same side groove wall in the groove width direction at the two curved portions 43.

[0069] Further, the bending angle of the bent portion 43 possessed by the curved sipe 42 is 90° or more. That is, for the curved sipe 42, the angle θ1 of the first bent portion 43a is 90° or more, and the angle θ2 of the second bent portion 43b is also 90° or more. The bending angle of the bent portion 43 in this case is the angle of the obtuse angle side of the bend. That is, the bent portion 43 of the curved sipe 42 is formed so as to have an obtuse bending angle. Further, the bending angle of the bent portion 43 is the angle of the center line of the groove width of the curved sipe 42. Note that the angle θ1 of the first bent portion 43a is preferably within the range of 90°≤ θ1≤ 130°, and the angle θ2 of the second bent portion 43b is also preferably within the range of 90°≤ θ2≤ 130°.

[0070] The curved sipe 42 has the first extension portion 42a, the second extension portion 42b, and the third extension portion 42c by being bent at the two bent portions 43 in this way, and the first extension portion 42a is formed so as to extend at an angle close to the tire width direction, and the second extension portion 42b is formed so as to extend at an angle close to the tire circumferential direction. For example, it is preferable that the inclination angle of the first extension portion 42a with respect to the tire width direction of the tire circumferential direction be within the range of 55° or more and 75° or less. Further, it is preferable that the inclination angle of the second extension portion 42b with respect to the tire width direction of the tire circumferential direction be within the range of 0° or more and 20° or less. Further, it is preferable that the inclination angle of the third extension portion 42c with respect to the tire width direction of the tire circumferential direction be within the range of 65° or more and 85° or less.

[0071] In the present embodiment, the two bent portions 43 of the curved sipe 42 are bent in the same direction, and thus, when the entire curved sipe 42 is observed, the curved sipe 42, which opens to the outer side circumferential groove 35 and extends in the tire width direction, is formed in a shape that folds back toward the outer side circumferential groove 35. That is, the third extension portion 42c of the curved sipe 42 is formed so as to approach the outer side circumferential groove 35 toward which the first extension portion 42a opens, as it goes from the second extension portion 42b side to the terminal portion 42d side.

[0072] Further, the first extension portion 42a, the second extension portion 42b, and the third extension portion 42c possessed by the curved sipe 42 are formed so as to have different lengths. Specifically, for the curved sipe 42, the length of the first extension portion 42a is the longest, the length of the second extension portion 42b is longer, and the length of the third extension portion 42c is the shortest. That is, the lengths of the first extension portion 42a, the second extension portion 42b, and the third extension portion 42c possessed by the curved sipe 42 satisfy the relationship of the length of the first extension portion 42a > the length of the second extension portion 42b > the length of the third extension portion 42c.

[0073] The curved sipe 42 has a plurality of curved portions 43, and the plurality of curved portions 43 of the curved sipe 42 are disposed in a range of 40% of the maximum width in the tire width direction of the land portion 20 in which the curved sipe 42 is disposed, centered on the center in the tire width direction of the land portion 20 in which the curved sipe 42 is disposed. That is, both of the curved portions 43 of the curved sipe 42 are disposed in the range, i.e., the disposition region AP1, of 40% of the maximum width WB1 in the tire width direction of the first second land portion 22a, centered on the center CB1 in the tire width direction of the first second land portion 22a in which the curved sipe 42 is disposed.

[0074] In other words, the disposition region AP1 here is a region in which, on both sides of the center CB1 in the tire width direction of the first second land portion 22a, each of the ranges of 20% of the maximum width WB1 of the first second land portion 22a. That is, the disposition region AP1 is a region of the range between the 30% position and the 70% position in the case where the position of one end side of both ends in the tire width direction of the portion of the first second land portion 22a that becomes the maximum width WB1 is set to 0% and the position of the other end side is set to 100%.

[0075] Further, the terminal portion 42d of the curved sipe 42 in the first second land portion 22a is also located in the disposition region AP1. Therefore, the second extension portion 42b and the third extension portion 42c of the curved sipe 42 are also located in the disposition region AP1.

[0076] The plurality of curved sipes 42 are disposed in the first second land portion 22a, and the plurality of curved sipes 42 are arranged in the same shape along the tire circumferential direction. Thus, it is preferable that the plurality of curved sipes 42 disposed in the first second land portion 22a be formed such that the relationship 0.6 ≤ (L / P) ≤ 0.8 is satisfied between the full length L in the tire circumferential direction of the curved sipe 42 and the pitch P of the curved sipes 42 adjacent to each other in the tire circumferential direction.

[0077] Further, for the curved sipe 42, as it goes from the end portion side that terminates in the land portion 20 to the end portion side that opens toward the circumferential groove 30, the groove width widens, and, further, as it goes from the end portion side that terminates in the land portion 20 to the end portion side that opens toward the circumferential groove 30, the groove depth deepens. In detail, for the curved sipe 42, as it goes from the terminal portion 42d side of the curved sipe 42 in the first second land portion 22a to the end portion side of the curved sipe 42 that opens toward the outer circumferential groove 35, the groove width of the curved sipe 42 widens, and the groove depth of the curved sipe 42 also deepens, with the position of the curved portion 43 as a boundary.

[0078] For the curved sipe 42, the groove width is different at the position of the curved portion 43, and thus the groove width of the curved sipe 42 is different among the first extension portion 42a, the second extension portion 42b, and the third extension portion 42c. Specifically, for the groove width of the curved sipe 42, the relationship of the groove width Wgl of the first extension portion 42a, the groove width Wg2 of the second extension portion 42b, and the groove width Wg3 of the third extension portion 42c satisfies Wgl > Wg2 > Wg3.

[0079] Further, the land portion 20 in which the curved sipe 42 is provided, that is, the first second land portion 22a is provided with a communicating sipe 61 that opens to a circumferential groove 30 different from the circumferential groove 30 on the side on which the curved sipe 42 opens and the curved sipe 42. That is, for the communicating sipe 61, one end thereof opens to the circumferential groove 30 different from the circumferential groove 30 on the side on which the curved sipe 42 opens, that is, the first inner circumferential groove 31a, among the two circumferential grooves 30 that divide the first second land portion 22a, and the other end thereof opens to the curved sipe 42. In detail, the communicating sipe 61 opens to the curved sipe 42 at the position of the first curved portion 43a of the curved sipe 42, is formed along the extension line of the first extension portion 42a toward the first inner circumferential groove 31a side from the position of the first curved portion 43a, and the end portion thereof opens to the first inner circumferential groove 31a. The communicating sipe 61 formed between the curved sipe 42 and the first inner circumferential groove 31a is formed as a straight sipe 60.

[0080] Further, the sipe 60 provided to the first second land portion 22a is provided so as to be inclined with respect to the tire width direction toward the tire circumferential direction, in other words, so as to be inclined with respect to the tire circumferential direction toward the tire width direction. Specifically, the sipe 60 provided to the first second land portion 22a is inclined with respect to the tire circumferential direction in the same direction as the inclination direction of the first extension portion 42a of the curved sipe 42 with respect to the tire circumferential direction toward the tire width direction.

[0081] Figure 4 is Figure 2The circumferential groove 50 of the pattern block-shaped land portion 20, i.e., the second second land portion 22b, has a relatively long strip portion 50a and a relatively short strip portion 50b by having a bend portion 51 that changes the extension direction at one place or more within the second second land portion 22b. For the strip portions 50a and 50b in this case, the length of the strip portion 50a is relatively longer than that of the strip portion 50b. In the present embodiment, the circumferential groove 50 has two bend portions 51, and the circumferential groove 50 is bent at two places. For the two bend portions 51, the bending directions in the groove width direction of the circumferential groove 50 are opposite to each other, and thus the circumferential groove 50 is formed in a meandering shape by extending along the tire circumferential direction and being bent at two places.

[0082] For the bend portion 51 of the circumferential groove 50, the bend angle θb of at least one bend portion 51 is 90° or more, and in the present embodiment, the bend angles θb of the two bend portions 51 of the circumferential groove 50 are each 90° or more. The bend angle θb of the bend portion 51 in this case is the angle on the obtuse angle side of the bend. That is, the bend portion 51 of the circumferential groove 50 is formed so as to have an obtuse bend angle. Further, the bend angle of the bend portion 51 is the angle of the center line of the groove width of the circumferential groove 50. Note that it is preferable that the angle θb of the bend portion 51 of the circumferential groove 50 be within the range of 90°≤θb≤140°.

[0083] For the circumferential groove 50 formed in a meandering shape, the portions between the two bend portions 51 are the short strip portions 50b, and the portions between each bend portion 51 and the end portion of the circumferential groove 50 that opens into the communicating sipe 44 are the long strip portions 50a. That is, the circumferential groove 50 has two long strip portions 50a that each open into the communicating sipe 44 adjacent in the tire circumferential direction, and a short strip portion 50b that is arranged so as to extend between the end portions of the two long strip portions 50a on the opposite side from the side that opens into the communicating sipe 44. The length of each of the two long strip portions 50a is longer than the length of the short strip portion 50b, and the lengths of the long strip portions 50a are substantially the same.

[0084] Further, the total length of the long portions 50a of one of the circumferential fine grooves 50 is in a range of 60% or more and 90% or less of the total length of one of the circumferential fine grooves 50. That is, in a case where the length of one of the long portions 50a is set to LI, the length of the other long portion 50a is set to L2, and further, the length of the short portion 50b is set to L3, the total length (LI + L2) of the long portions 50a is in a range of 60% or more and 90% or less of the total length (LI + L2 + L3) of one of the circumferential fine grooves 50. That is, each length of the circumferential fine grooves 50 satisfies a relationship of 0.6 ≤ (LI + L2) / (LI + L2 + L3) ≤ 0.9.

[0085] The two long portions 50a of the circumferential fine groove 50 are each inclined with respect to the tire width direction relative to the tire circumferential direction, and the inclination angle with respect to the tire circumferential direction is substantially the same between the two long portions 50a. The inclination θn of the long portion 50a of the circumferential fine groove 50 with respect to the tire width direction relative to the tire circumferential direction is in a range of 5° or more and 45° or less.

[0086] Note that the lengths LI, L2 of the long portions 50a of the circumferential fine groove 50, the length L3 of the short portion 50b, and the inclination θn of the long portion 50a are the length, the inclination of the center line of the groove width of the circumferential fine groove 50.

[0087] The inclination direction of the short portion 50b of the circumferential fine groove 50 with respect to the tire width direction relative to the tire circumferential direction is the opposite direction. The circumferential fine groove 50 is formed in a zigzag shape extending along the tire circumferential direction and fluctuating in the tire width direction by thus making the inclination directions of the long portion 50a and the short portion 50b with respect to the tire width direction relative to the tire circumferential direction opposite to each other.

[0088] The sipe 60 arranged in the second land portion 22b is arranged so as to be inclined with respect to the tire circumferential direction relative to the tire width direction, in other words, so as to be inclined with respect to the tire width direction relative to the tire circumferential direction. Specifically, the sipe 60 arranged in the second land portion 22b is inclined with respect to the tire circumferential direction in the opposite direction to the inclination direction of the long portion 50a of the circumferential fine groove 50 with respect to the tire width direction relative to the tire circumferential direction.

[0089] The end portion of the circumferential fine groove 50 opens to the communicating cross groove 44, and the circumferential fine grooves 50 opening to the communicating cross groove 44 from opposite sides in the groove width direction of the communicating cross groove 44 open to the same communicating cross groove 44 at positions close to each other in the tire width direction, or have portions that become the same position in the tire width direction.

[0090] The second inner side circumferential groove 31b, which divides the two sides in the tire width direction of the second second land portion 22b provided with the circumferential fine groove 50, is formed in a zigzag shape by extending along the tire circumferential direction and undulating in the tire width direction. Further, the second inner side circumferential groove 31b is formed in a zigzag shape having long strip portions 32 and short strip portions 33 of relatively different lengths, which are alternately arranged with the bending positions of the zigzag as boundaries. For the long strip portions 32 and the short strip portions 33 in this case, the length of the long strip portions 32 is relatively longer than that of the short strip portions 33.

[0091] Thus, for the second inner side circumferential groove 31b having the long strip portions 32 and the short strip portions 33 and formed in a zigzag shape, the period of the zigzag in the tire circumferential direction is the same size as the interval in the tire circumferential direction between the adjacent communicating sipe grooves 44. Therefore, the long strip portions 32 and the short strip portions 33 possessed by the second inner side circumferential groove 31b each have one in the portion of the second inner side circumferential groove 31b between the adjacent communicating sipe grooves 44 in the tire circumferential direction. Thus, the long strip portions 32 and the short strip portions 33 each have one in the portion of the second inner side circumferential groove 31b dividing one second second land portion 22b. In other words, the portion of one second second land portion 22b formed by the second inner side circumferential groove 31b is divided by one set of the long strip portions 32 and the short strip portions 33 possessed by the second inner side circumferential groove 31b.

[0092] The second inner side circumferential groove 31b is formed by extending along the tire circumferential direction and undulating in the tire width direction, and thus the long strip portions 32 and the short strip portions 33 are each inclined in the tire width direction with respect to the tire circumferential direction, and the inclination directions in the tire width direction of the long strip portions 32 and the short strip portions 33 are opposite directions. For the circumferential fine groove 50 provided in the second second land portion 22b, the inclination direction in the tire width direction with respect to the tire circumferential direction of the long strip portion 50a is in the opposite direction to the inclination direction in the tire width direction with respect to the tire circumferential direction of the long strip portion 32 of the second inner side circumferential groove 31b inclined as described above with respect to the tire circumferential direction. That is, for the circumferential fine groove 50, the inclination directions in the tire width direction with respect to the tire circumferential direction of the two long strip portions 50a possessed by the circumferential fine groove 50 are each in the opposite direction to the inclination direction in the tire width direction with respect to the tire circumferential direction of the long strip portion 32 of the second inner side circumferential groove 31b.

[0093] Note that the inclination θc of the elongated portion 32 of the second inner side circumferential groove 31b with respect to the tire width direction of the tire circumferential direction is in a range of 5° or more and 30° or less. The inclination θc of the elongated portion 32 of the second inner side circumferential groove 31b in this case is the inclination of the center line of the groove width of the second inner side circumferential groove 31b. It is preferable that the inclination θn of the elongated portion 50a of the circumferential fine groove 50 with respect to the tire width direction of the tire circumferential direction be formed to be larger than the inclination θc of the elongated portion 32 of the second inner side circumferential groove 31b.

[0094] Further, the curved portion 51 of the circumferential fine groove 50 is disposed in a range of 40% of the maximum width in the tire width direction of the land portion 20 with the curved portion 51 of the circumferential fine groove 50 disposed thereon as a center. That is, both of the curved portions 51 of the circumferential fine groove 50 are disposed in a range, that is, a disposition region AP2, of 40% of the maximum width WB2 in the tire width direction of the second second land portion 22b with the center CB2 in the tire width direction of the second second land portion 22b with the curved portion 51 of the circumferential fine groove 50 disposed thereon as a center.

[0095] In other words, the disposition region AP2 here is a region in which, on both sides of the center CB2 in the tire width direction of the second second land portion 22b, a range of 20% of the maximum width WB2 of the second second land portion 22b is formed. That is, the disposition region AP2 is a region of a range between a position of 30% and a position of 70% in the case where a position of one end side of both ends in the tire width direction of the portion of the second second land portion 22b that becomes the maximum width WB2 is set to 0% and a position of the other end side is set to 100%.

[0096] Further, the circumferential fine groove 50 is formed to have a change point of groove depth at at least one location within the land portion 20. Figure 5 is Figure 4 is a schematic view of a cross section of the circumferential fine groove 50 along the extending direction. The circumferential fine groove 50 is formed to have a change point of groove depth at at least one location within the land portion 20. In the present embodiment, for the circumferential fine groove 50, the position of the curved portion 51 is the change point of groove depth, and the groove depth of the circumferential fine groove 50 is different with the position of the curved portion 51 as a boundary. That is, the groove depth of the circumferential fine groove 50 is different in the elongated portion 50a and the short portion 50b, and the relationship between the groove depth Dna of the elongated portion 50a and the groove depth Dnb of the short portion 50b satisfies Dna > Dnb.

[0097] When the pneumatic tire 1 of the present embodiment is attached to a vehicle, the pneumatic tire 1 is assembled to a rim wheel, is filled with air inside, and is attached to a vehicle in a state of being inflated. When the vehicle to which the pneumatic tire 1 is attached is driven, the lower of the tread ground surfaces 3 in the tread portion 2 comes into contact with a road surface while the pneumatic tire 1 is rotated. In the case where the vehicle to which the pneumatic tire 1 is attached is driven on a dry road surface, driving force, braking force is transmitted to the road surface or turning force is generated by the frictional force between the tread ground surfaces 3 and the road surface, and thus the vehicle is driven.

[0098] Further, when driven on a wet road surface, water between the tread ground surfaces 3 and the road surface enters the grooves such as the circumferential grooves 30, the cross groove 40, the sipe pattern 60, and is discharged from the tread ground surfaces 3 and the road surface by the grooves while being driven. Thus, the tread ground surfaces 3 easily come into contact with the road surface, and the vehicle can be driven by the frictional force between the tread ground surfaces 3 and the road surface.

[0099] Further, when driven on a snowy road surface, the pneumatic tire 1 presses snow on the road surface with the tread ground surfaces 3, and the snow on the road surface enters the circumferential grooves 30, the cross groove 40, and thus the snow is in a pressed state in the grooves. In this state, when driving force, braking force is applied to the pneumatic tire 1 or force in the tire width direction is applied by turning of the vehicle, shear force acting on the snow in the grooves, so-called snow column shear force, is generated between the pneumatic tire 1 and the snow. When driven on a snowy road surface, by the snow column shear force, resistance is generated between the pneumatic tire 1 and the road surface, and thus driving force, braking force can be transmitted to the road surface, and snow traction can be ensured. Thus, the vehicle can be driven on a snowy road surface.

[0100] Further, when driven on a snowy road surface, an icy road surface, the edge effect of the circumferential grooves 30, the cross groove 40, the sipe pattern 60 is also used for driving. That is, when driven on a snowy road surface, an icy road surface, resistance generated by the edges of the circumferential grooves 30, the edges of the cross groove 40, the edges of the sipe pattern 60 being caught in the snow surface, the ice surface is used for driving. Further, when driven on an icy road surface, water on the surface of the icy road surface is absorbed by the sipe pattern 60, and a water film between the icy road surface and the tread ground surfaces 3 is removed, and thus the icy road surface easily comes into contact with the tread ground surfaces 3. Thus, for the tread ground surfaces 3, the resistance between the tread ground surfaces 3 and the icy road surface becomes large by the frictional force, the edge effect, and thus the driving performance of the vehicle to which the pneumatic tire 1 is attached can be ensured.

[0101] Thus, the circumferential grooves 30, the lateral grooves 40, and the sipe grooves 60 formed in the tread portion 2 contribute to ensuring the running performance on a wet road surface, a snowy road surface, and an icy road surface, and thus, for example, increasing the groove area of the tread portion 2 is effective in improving the running performance on a wet road surface, i.e., the wet performance. That is, in a case where the groove area of the circumferential grooves 30, the lateral grooves 40, and the like is increased, when running on a wet road surface, water on the road surface easily enters the grooves, and thus, the water drainage performance between the tread ground surface 3 and the road surface can be improved, and the wet performance can be improved.

[0102] Further, increasing the groove area is also effective in improving the running performance on a snowy road surface, i.e., the snowy performance. That is, in a case where the groove area is increased, when running on a snowy road surface, the amount of snow that can enter the circumferential grooves 30 and the lateral grooves 40 can be increased, and thus, the snow column shear force acting on the snow that has entered the grooves can be increased. Thus, the snow traction performance when running on a snowy road surface can be improved, and the snowy performance can be improved.

[0103] Here, in a case where the groove area of the tread portion 2 is increased, the volume of the land portion 20d partitioned by the circumferential grooves 30 and the lateral grooves 40 decreases as the groove area increases. In a case where the volume of the land portion 20 decreases, the rigidity of the land portion 20 can decrease, and when a load is applied, the land portion 20 can easily deform and collapse. When the land portion 20 collapses, the ground contact area of the collapsed land portion 20 can decrease, and thus, it can be difficult to ensure the running performance.

[0104] For example, when running on an icy road surface, in addition to the edge effect caused by the edge components of the grooves, the frictional force caused by the ground contact between the tread ground surface 3 and the icy road surface is also important. However, in a case where the rigidity of the land portion 20 decreases due to the increase in the groove area of the tread portion 2, the land portion 20 can easily collapse when a load is applied, and thus, the ground contact area can easily decrease, and it can be difficult to ensure the running performance achieved by the frictional force. Thus, in a case where the rigidity of the land portion 20 decreases due to the increase in the groove area of the tread portion 2, when braking on an icy road surface, the land portion 20 can easily collapse, and thus, the ground contact area can easily decrease, and the braking performance on an icy road surface can easily decrease.

[0105] In contrast, in the pneumatic tire 1 of the present embodiment, by forming the second inner circumferential groove 31b of the plurality of circumferential grooves 30 in a sawtooth shape having the long strip portion 32 and the short strip portion 33, the length of the second inner circumferential groove 31b is ensured. Thus, the groove area of the second inner circumferential groove 31b can be increased, and thus, when running on a snowy road surface, more snow can enter the second inner circumferential groove 31b, and the snow column shear force can be ensured. Thus, the snow traction performance can be improved, and the snowy performance can be improved.

[0106] Further, by ensuring the length of the second inner side circumferential groove 31b and increasing the groove area, when running on a wet road surface, more water can enter the second inner side circumferential groove 31b. Thus, the water drainage performance when draining water between the tread ground surface 3 and the road surface through the second inner side circumferential groove 31b can be improved, and the wet performance can be improved.

[0107] Further, the second inner side circumferential groove 31b is formed in a zigzag shape, and thus the snow column shear force on the snow entering the second inner side circumferential groove 31b can be effectively exerted. Thus, the snow traction can be more reliably improved, and the snow performance can be improved.

[0108] Further, the circumferential fine groove 50 is provided in the second second land portion 22b divided by the second inner side circumferential groove 31b, and thus when running on a wet road surface, water between the tread ground surface 3 and the road surface can also enter the circumferential fine groove 50, and the water drainage performance can also be ensured by the circumferential fine groove 50. Further, by providing the circumferential fine groove 50 in the second second land portion 22b, when running on a snowy road surface, snow can also enter the circumferential fine groove 50, and the snow column shear force can be more reliably ensured. Moreover, the circumferential fine groove 50 has a bend portion 51 in which the extension direction changes at one or more places in the second second land portion 22b, and the length of the circumferential fine groove 50 is increased. Thus, more water and snow can enter the circumferential fine groove 50, and the water drainage performance and the snow column shear force achieved by the circumferential fine groove 50 can be improved.

[0109] Further, the circumferential fine groove 50 having the bend portion 51 has a long strip portion 50a and a short strip portion 50b having relatively different lengths, and the inclination direction of the long strip portion 50a of the circumferential fine groove 50 with respect to the tire width direction of the tire circumferential direction is in the opposite direction to the inclination direction of the long strip portion 32 of the circumferential groove 30 with respect to the tire width direction of the tire circumferential direction. Thus, when the groove area of the tread portion 2 is increased by bending and increasing the length of the circumferential fine groove 50, the rigidity of the second second land portion 22b in which the circumferential fine groove 50 is provided can be suppressed from decreasing. Specifically, the inclination direction of the long strip portion 50a of the circumferential fine groove 50 is in the opposite direction to the inclination direction of the long strip portion 32 of the circumferential groove 30, and thus the rigidity of the second second land portion 22b can be suppressed from appearing directional.

[0110] That is, when the inclination directions are the same direction in the long portions 50a of the circumferential fine grooves 50 and the long portions 32 of the circumferential grooves 30, the land portion 20 provided with the circumferential fine grooves 50 can easily ensure rigidity in the extending direction of the long portions 50a of the circumferential fine grooves 50 and the long portions 32 of the circumferential grooves 30, and can hardly ensure rigidity in a direction close to a direction orthogonal to the extending direction of the long portions 50a of the circumferential fine grooves 50 and the long portions 32 of the circumferential grooves 30. In this case, when a load in the direction close to the direction orthogonal to the extending direction of the long portions 50a of the circumferential fine grooves 50 and the long portions 32 of the circumferential grooves 30 acts on the land portion 20 provided with the circumferential fine grooves 50, the land portion 20 can easily collapse, and thus the ground contact area can decrease and it can be difficult to ensure the braking performance on an icy road surface.

[0111] On the contrary, in the present embodiment, the inclination direction of the long portions 50a of the circumferential fine grooves 50 with respect to the tire width direction from the tire circumferential direction is opposite to the inclination direction of the long portions 32 of the circumferential grooves 30 with respect to the tire width direction from the tire circumferential direction, and thus it is possible to suppress the generation of a direction in which rigidity with respect to an acting load is weak in the second land portion 22b provided with the circumferential fine grooves 50. Thus, it is possible to suppress the collapse of the second land portion 22b when a load acts on the second land portion 22b regardless of the direction of the load. Therefore, it is possible to suppress the decrease in the ground contact area due to the collapse of the second land portion 22b, and thus it is possible to ensure the performance on an icy road surface, i.e., the icy performance, including the braking performance when running on an icy road surface. As a result of these, it is possible to suppress the decrease in the icy performance, and it is possible to ensure the performance on a snowy road surface and the performance on a wet road surface.

[0112] Further, the circumferential fine grooves 50 are formed to be open to the sipe grooves 40, and thus it is possible to cause water entering the circumferential fine grooves 50 to flow to the sipe grooves 40 when running on a wet road surface, or to cause snow entering the circumferential fine grooves 50 to flow to the sipe grooves 40 when running on a snowy road surface. Thus, it is possible to more reliably improve the water drainage performance and the snow drainage performance of the circumferential fine grooves 50. As a result of these, it is possible to more reliably improve the performance on a snowy road surface and the performance on a wet road surface.

[0113] Further, the circumferential fine grooves 50 have a change point of groove depth at least once, and thus it is possible to generate a snow column shear force in the circumferential fine grooves 50 when running on a snowy road surface at the position of the change point of groove depth, and it is possible to more reliably improve the snow traction performance. Further, by providing the change point of groove depth in the circumferential fine grooves 50, it is possible to form the flow of water in the circumferential fine grooves 50 when water enters the circumferential fine grooves 50 when running on a wet road surface, and it is possible to improve the water drainage performance in the circumferential fine grooves 50. As a result of these, it is possible to more reliably improve the performance on a snowy road surface and the performance on a wet road surface.

[0114] Further, the inclination θn of the long portion 50a of the circumferential fine groove 50 with respect to the tire width direction of the tire circumferential direction is in a range of 5° or more and 45° or less, and thus the water drainage performance and the snow column shear force by the circumferential fine groove 50 can be more reliably improved. That is, in a case where the inclination θn of the long portion 50a of the circumferential fine groove 50 with respect to the tire circumferential direction is less than 5°, the inclination θn of the long portion 50a of the circumferential fine groove 50 is too small, and thus even if the circumferential fine groove 50 is bent, it can be difficult to effectively increase the length of the circumferential fine groove 50. In this case, even if the circumferential fine groove 50 is bent, it can be difficult to effectively improve the water drainage performance and the snow column shear force by the circumferential fine groove 50. Further, in a case where the inclination θn of the long portion 50a of the circumferential fine groove 50 with respect to the tire circumferential direction is more than 45°, the inclination θn of the long portion 50a of the circumferential fine groove 50 is too large, and thus the difference between the flow direction of water entering the circumferential fine groove 50 and the rotation direction of the pneumatic tire 1 can become too large. In this case, it can be difficult to efficiently flow water in the circumferential fine groove 50, and it can be difficult to effectively improve the water drainage performance by the circumferential fine groove 50.

[0115] On the contrary, in a case where the inclination θn of the long portion 50a of the circumferential fine groove 50 with respect to the tire circumferential direction is in a range of 5° or more and 45° or less, the difference between the flow direction of water flowing in the circumferential fine groove 50 and the rotation direction of the pneumatic tire 1 can be suppressed from becoming too large, and the length of the circumferential fine groove 50 can be effectively increased. Thus, the water drainage performance and the snow column shear force by the circumferential fine groove 50 can be more reliably improved. As a result, the snow performance and the wet performance can be more reliably improved.

[0116] Further, the inclination θc of the long portion 32 of the circumferential groove 30 with respect to the tire width direction of the tire circumferential direction is in a range of 5° or more and 30° or less, and thus the water drainage performance and the snow column shear force by the circumferential fine groove 50 can be more reliably improved. That is, in a case where the inclination θc of the long portion 32 of the circumferential groove 30 with respect to the tire circumferential direction is less than 5°, the inclination θc of the long portion 32 of the circumferential groove 30 is too small, and thus even if the circumferential groove 30 is formed in a zigzag shape, it can be difficult to effectively increase the length of the circumferential groove 30. In this case, even if the circumferential groove 30 is formed in a zigzag shape, it can be difficult to effectively improve the water drainage performance and the snow column shear force by the circumferential groove 30. Further, in a case where the inclination θc of the long portion 32 of the circumferential groove 30 with respect to the tire circumferential direction is more than 30°, the inclination of the long portion 32 of the circumferential groove 30 is too large, and thus the difference between the flow direction of water entering the circumferential groove 30 and the rotation direction of the pneumatic tire 1 can become too large. In this case, it can be difficult to efficiently flow water in the circumferential groove 30, and it can be difficult to effectively improve the water drainage performance by the circumferential groove 30.

[0117] On the other hand, in the case where the inclination θc of the long portion 32 of the circumferential groove 30 with respect to the tire circumferential direction is in a range of 5° or more and 30° or less, it is possible to suppress the flow direction of water flowing through the circumferential groove 30 from becoming too different from the rotation direction of the pneumatic tire 1, and it is possible to effectively increase the length of the circumferential groove 30. Thus, it is possible to more reliably improve the water drainage performance, the snow column shearing force, and the like achieved by the circumferential groove 30. As a result, it is possible to more reliably improve the snow performance and the wet performance.

[0118] Further, the bending angle θb of the bending portion 51 of the circumferential fine groove 50 is 90° or more, and thus it is possible to more reliably ensure the rigidity of the land portion 20 and to ensure the flow easiness of water in the circumferential fine groove 50. That is, in the case where the bending angle θb of the bending portion 51 is less than 90°, that is, in the case where the bending portion 51 is formed as an acute angle, it can be difficult to ensure the rigidity of the portion of the land portion 20 located on the inferior angle side of the bending portion 51. In this case, it can be difficult to effectively suppress the collapse of the land portion 20 when a load acts on the land portion 20. Further, in the case where the bending angle θb of the bending portion 51 is less than 90°, the flow of water in the circumferential fine groove 50 when water enters the circumferential fine groove 50 can be poor. In this case, it can be difficult to effectively ensure the water drainage performance in the circumferential fine groove 50.

[0119] On the other hand, in the case where the bending angle θb of the bending portion 51 is 90° or more, it is possible to ensure the rigidity of the portion of the land portion 20 located on the inferior angle side of the bending portion 51, to effectively suppress the collapse of the land portion 20, and to ensure the flow easiness of water in the circumferential fine groove 50. Thus, it is possible to more reliably suppress the reduction of the ground contact area due to the collapse of the land portion 20 and to more reliably ensure the water drainage performance in the circumferential fine groove 50. As a result, it is possible to more reliably seek a balance between the ice performance and the wet performance.

[0120] Further, the total length of the long strip portion 50a possessed by one circumferential fine groove 50 is in a range of 60% or more and 90% or less of the total length of one circumferential fine groove 50, thus the rigidity of the land portion 20 can be more reliably ensured, and the edge component of the circumferential fine groove 50 can be ensured. That is, in a case where the total length of the long strip portion 50a possessed by one circumferential fine groove 50 is less than 60% of the total length of one circumferential fine groove 50, the total length of the long strip portion 50a becomes too short, and relatively, the length of the short strip portion 50b becomes too long, thus it can be difficult to ensure the rigidity of the land portion 20 in which the circumferential fine groove 50 is arranged. In this case, it can be difficult to effectively suppress the collapse of the land portion 20 when a load acts on the land portion 20. Further, in a case where the total length of the long strip portion 50a possessed by one circumferential fine groove 50 is more than 90% of the total length of one circumferential fine groove 50, the total length of the long strip portion 50a becomes too long, and relatively, the length of the short strip portion 50b becomes too short, thus it can be difficult to ensure the edge component of the circumferential fine groove 50. In this case, it can be difficult to obtain the edge effect achieved by arranging the circumferential fine groove 50 in the land portion 20.

[0121] In contrast to this, in a case where the total length of the long strip portion 50a possessed by one circumferential fine groove 50 is in a range of 60% or more and 90% or less of the total length of one circumferential fine groove 50, the rigidity of the land portion 20 in which the circumferential fine groove 50 is arranged can be ensured, the collapse of the land portion 20 can be effectively suppressed, and the edge component of the circumferential fine groove 50 can be ensured. Thus, the reduction of the grounding area due to the collapse of the land portion 20 can be more reliably suppressed, and the edge effect achieved by the circumferential fine groove 50 can be more reliably obtained. As a result, the performance on ice and the performance on snow can be more reliably improved.

[0122] Further, the curved portion 51 of the circumferential fine groove 50 is arranged in a range of 40% of the maximum width WB2 in the tire width direction of the second second land portion 22b centered on the center CB2 in the tire width direction of the second second land portion 22b in which the circumferential fine groove 50 is arranged, thus the rigidity of the second second land portion 22b can be more reliably ensured. That is, in a case where the arrangement position of the curved portion 51 is outside the range of 40% of the maximum width WB2 of the second second land portion 22b, the distance between the circumferential groove 30 that divides the second second land portion 22b and the curved portion 51 becomes too small, thus it can be difficult to ensure the rigidity of the portion between the curved portion 51 and the circumferential groove 30 in the second second land portion 22b. In this case, it can be difficult to suppress the collapse of the second second land portion 22b when a load acts on the second second land portion 22b, and it can be difficult to effectively suppress the reduction of the grounding area when a load acts.

[0123] On the other hand, in a case where the arrangement position of the curved portion 51 of the circumferential fine groove 50 is within a range of 40% of the maximum width WB2 of the second second land portion 22b, it is possible to suppress the distance between the circumferential groove 30 and the curved portion 51 from becoming too small, and it is possible to ensure the rigidity of the second second land portion 22b. Thus, it is possible to more reliably suppress a decrease in the ground contact area due to collapse of the second second land portion 22b. As a result, it is possible to more reliably improve the performance on ice.

[0124] Further, the circumferential groove 30 is formed so that the groove width is within a range of 4 mm or more and 12 mm or less, and thus it is possible to suppress the rigidity of the land portion 20 divided by the circumferential groove 30 from becoming too low, and it is possible to ensure the drainability and the snow column shear force achieved by the circumferential groove 30. Further, the circumferential fine groove 50 is formed so that the groove width is within a range of 1.5 mm or more and 4 mm or less, and thus it is possible to suppress the rigidity of the land portion 20 in which the circumferential fine groove 50 is arranged from becoming too low, and it is possible to ensure the drainability and the snow column shear force achieved by the circumferential fine groove 50. As a result, it is possible to more reliably suppress a decrease in the performance on ice, and it is possible to ensure the performance on snow and the performance on wet ground.

[0125] Further, the land portion 20 is arranged with a plurality of sipe grooves 60 extending along the tire width direction, and thus it is possible to increase the edge component, and it is possible to improve the performance on ice by the edge effect when running on an icy road surface. Further, by arranging the plurality of sipe grooves 60 in the land portion 20, it is possible to absorb water on the road surface by the sipe grooves 60 when running on a wet road surface, and it is possible to improve the drainability. As a result, it is possible to more reliably improve the performance on ice and the performance on wet ground.

[0126] Further, the sipe groove 60 arranged in the land portion 20 in which the circumferential fine groove 50 is arranged is inclined with respect to the tire circumferential direction in a direction opposite to the inclination direction of the elongated portion 50a of the circumferential fine groove 50 with respect to the tire width direction, and thus it is possible to suppress a decrease in the rigidity of the land portion 20 in which the circumferential fine groove 50 is arranged. That is, in a case where the inclination direction of the elongated portion 50a of the circumferential fine groove 50 and the sipe groove 60 with respect to the tire circumferential direction is the same direction, the land portion 20 in which the circumferential fine groove 50 is arranged can be difficult to ensure the rigidity with respect to a direction close to a direction orthogonal to the extension directions of the elongated portion 50a of the circumferential fine groove 50 and the sipe groove 60.

[0127] On the other hand, in a case where the inclination direction of the elongated portion 50a of the circumferential fine groove 50 and the sipe groove 60 with respect to the tire circumferential direction is the opposite direction, it is possible to suppress a direction in which the rigidity with respect to an applied load is weak in the land portion 20 in which the circumferential fine groove 50 is arranged. Thus, it is possible to suppress collapse of the land portion 20 when a load is applied to the land portion 20 regardless of the direction of the load, and it is possible to suppress a decrease in the ground contact area due to collapse of the land portion 20. As a result, it is possible to more reliably improve the performance on ice.

[0128] [Modified example]

[0129] Note that, in the above-described embodiment, for the circumferential grooves 30 that divide the land portion 20 provided with the circumferential fine grooves 50, the circumferential groove 30 that divides the inner side in the tire width direction is formed in a zigzag shape, and the circumferential groove 30 that divides the outer side in the tire width direction is formed in a straight line shape, but the circumferential groove 30 can also be in a manner other than this. Figure 6 is a modified example of the pneumatic tire 1 of the embodiment, and is a plan view of the land portion 20 provided with the circumferential fine grooves 50. For the two circumferential grooves 30 that divide the both sides in the tire width direction of the land portion 20 provided with the circumferential fine grooves 50, for example, as shown in Figure 6 , both of the circumferential grooves 30 are formed in a zigzag shape by extending along the tire circumferential direction and undulating in the tire width direction. In other words, the circumferential fine grooves 50 can also be provided to the land portion 20 whose both sides in the tire width direction are divided by the two circumferential grooves 30 formed in a zigzag shape. In this case, it is preferable that the inclination direction of the long portion 50a of the circumferential fine groove 50 with respect to the tire width direction be in the opposite direction to the inclination direction of the long portion 32 of the circumferential groove 30 on the inner side in the tire width direction among the two circumferential grooves 30 that divide the both sides in the tire width direction of the land portion 20 provided with the circumferential fine grooves 50.

[0130] That is, as shown in Figure 6 , in a case where both of the second inner side circumferential groove 31b and the outer side circumferential groove 35 that divide the both sides in the tire width direction of the second land portion 22b provided with the circumferential fine grooves 50 are formed in a zigzag shape, it is preferable that the inclination direction of the long portion 50a of the circumferential fine groove 50 with respect to the tire width direction be in the opposite direction to the inclination direction of the long portion 32 of the second inner side circumferential groove 31b that divides the inner side in the tire width direction of the second land portion 22b. When the vehicle is braking, a larger load is likely to act on the position on the inner side in the tire width direction, and by setting the inclination direction of the long portion 50a of the circumferential fine groove 50 to the opposite direction to the inclination direction of the long portion 32 of the circumferential groove 30 that divides the inner side in the tire width direction of the land portion 20 provided with the circumferential fine grooves 50, the rigidity of the portion of the land portion 20 provided with the circumferential fine grooves 50 on the inner side in the tire width direction than the circumferential fine grooves 50 can be ensured.

[0131] Thus, the rigidity of the portion to which a large load acts during braking in the land portion 20 can be more reliably ensured, the collapse of the land portion 20 can be suppressed, and thus the reduction in the ground contact area of the portion to which a large load acts during braking due to the collapse of the land portion 20 can be suppressed. Thus, the performance on ice, including the braking performance on ice, can be more reliably ensured. As a result, the performance on ice can be more reliably improved.

[0132] Note that in the case where the circumferential groove 30 that divides the inner side in the tire width direction and the circumferential groove 30 that divides the outer side in the tire width direction are formed in straight lines and the circumferential groove 30 that divides the outer side in the tire width direction is formed in a zigzag shape, it is preferable that the long portion 50a of the circumferential fine groove 50 be formed such that the inclination direction thereof is opposite to the inclination direction of the long portion 32 of the circumferential groove 30 that divides the outer side in the tire width direction.

[0133] Further, in the above-described embodiment, the both ends in the length direction of the circumferential fine groove 50 are open to the cross groove 40, but the both ends of the circumferential fine groove 50 can not be open to the cross groove 40, as long as at least one end of the circumferential fine groove 50 is open to the cross groove 40. The circumferential fine groove 50 is open to the cross groove 40 at at least one end in the length direction thereof, and thus water and snow that have entered the circumferential fine groove 50 flow to the cross groove 40, and the water drainage and snow drainage performance of the circumferential fine groove 50 can be improved. Thus, the performance on snow and the performance on wet ground can be improved.

[0134] Further, in the above-described embodiment, the circumferential fine groove 50 has two bent portions 51, but the circumferential fine groove 50 can have more than two bent portions 51. For example, the circumferential fine groove 50 can have one bent portion 51. As long as the circumferential fine groove 50 is formed to have the long portion 50a and the short portion 50b by the bent portion 51 having a change in the extension direction of one or more, and the inclination direction of the long portion 50a is opposite to the inclination direction of the long portion 32 of the circumferential groove 30, the number of the bent portions 51 is not limited.

[0135] Further, in the above-described embodiment, the bent angles of the two bent portions 51 of the circumferential fine groove 50 are each 90° or more, but the bent angles of the bent portions 51 can not be 90° or more for all the bent portions 51. For the bent portions 51, as long as the bent angle of at least one of the bent portions 51 of one circumferential fine groove 50 is 90° or more, the bent angles of the bent portions 51 are not limited. By forming the circumferential fine groove 50 such that the bent angle of at least one of the bent portions 51 is 90° or more, the decrease in the rigidity of the land portion 20 in which the circumferential fine groove 50 is provided can be suppressed, and the ease of flow of water in the circumferential fine groove 50 can be ensured.

[0136] Further, in the above-described embodiment, the circumferential fine groove 50 is provided in the second second land portion 22b among the plurality of land portions 20 arranged in the tire width direction, but the land portion 20 in which the circumferential fine groove 50 is provided can be a land portion 20 other than the second second land portion 22b. Further, the circumferential fine groove 50 can be provided in a plurality of land portions 20 whose positions in the tire width direction are different from each other.

[0137] Further, in the above-described embodiment, the circumferential fine groove 50 is provided in the second second land portion 22b among the plurality of land portions 20 arranged in the tire width direction, but the land portion 20 in which the circumferential fine groove 50 is provided can be a land portion 20 other than the second second land portion 22b. Further, the circumferential fine groove 50 can be provided in a plurality of land portions 20 whose positions in the tire width direction are different from each other.

[0138] [Example]

[0139] Figure 7 is a graph showing the results of performance evaluation tests of the pneumatic tire. Hereinafter, with respect to the above-described pneumatic tire 1, the performance evaluation tests performed on the pneumatic tire of the prior example, the pneumatic tire 1 of the present application, and the pneumatic tire of the comparative example compared with the pneumatic tire 1 of the present application will be described. The performance evaluation tests were performed on tests related to the braking performance on a snowy road surface, the braking performance on an icy road surface, and the braking performance on a wet road surface.

[0140] The performance evaluation tests were performed in such a manner that a pneumatic tire 1 rim having a tire size of 195 / 65R15 91Q prescribed by JATMA was assembled to a JATMA standard rim wheel having a rim size of 15 x 6.5J, a test tire was attached to a front-wheel drive evaluation vehicle having a displacement of 1800 cc, the air pressure was adjusted to 250 kPa for the front wheels and 240 kPa for the rear wheels, and the evaluation vehicle was driven.

[0141] Among the evaluation methods of each test item, the braking on snow was evaluated in such a manner that a braking test was performed on a test course on a snowy road surface with the evaluation vehicle to which the test tire was attached, and the reciprocal of the braking distance was expressed by an index of 100 for the above-described prior example. With respect to the braking on snow, the larger the index, the shorter the braking distance on the snowy road surface, and the more excellent the performance related to the braking on snow.

[0142] Further, the braking on ice was evaluated in such a manner that a braking test was performed on a test course on an icy road surface with the evaluation vehicle to which the test tire was attached, and the reciprocal of the braking distance was expressed by an index of 100 for the above-described prior example. With respect to the braking on ice, the larger the index, the shorter the braking distance on the icy road surface, and the more excellent the performance related to the braking on ice.

[0143] Further, wet road braking was evaluated by performing a braking test on a test course on a wet road surface with an evaluation vehicle equipped with the test tire, and expressing the reciprocal of the braking distance with an index of 100 for the following prior example. The greater the index, the shorter the braking distance on a wet road surface, and the more excellent the performance related to wet road braking.

[0144] Performance evaluation tests were performed on nine pneumatic tires, a prior example pneumatic tire as an example of a conventional pneumatic tire, embodiments 1 to 7 as pneumatic tires 1 of the present application, and comparative examples as pneumatic tires for comparison with the pneumatic tires 1 of the present application. In the prior example, the circumferential fine groove has no curved portion, and the inclination direction of the circumferential fine groove is the same direction as the inclination direction of the elongated portion of the circumferential groove. Further, in the comparative examples, the circumferential fine groove has no curved portion.

[0145] In contrast, in embodiments 1 to 7 as examples of the pneumatic tires 1 of the present application, all of the circumferential fine grooves 50 have curved portions 51, and the inclination direction of the elongated portion 50a of the circumferential fine groove 50 is the opposite direction to the inclination direction of the elongated portion 32 of the circumferential groove 30. Further, for the pneumatic tires 1 of embodiments 1 to 7, the arrangement position of the circumferential groove 30 with respect to the circumferential fine groove 50, whether at least a section of the circumferential fine groove 50 is open to the cross groove 40, the groove depth of the circumferential fine groove 50, the angle θη of the elongated portion 50a of the circumferential fine groove 50 with respect to the tire circumferential direction, and the angle θc of the elongated portion 32 of the circumferential groove 30 with respect to the tire circumferential direction are each different.

[0146] The results of the performance evaluation tests using these pneumatic tires 1 were that, as shown in Table 1, Figure 7 that is, the pneumatic tires 1 of embodiments 1 to 7 can suppress a decrease in ice performance, and can ensure snow performance and wet performance.

[0147] Explanation of Reference Numerals

[0148] 1: Pneumatic tire;

[0149] 2: Tread portion;

[0150] 3: Tread ground contact surface;

[0151] 8: Sidewall portion;

[0152] 10: Bead portion;

[0153] 13: Carcass ply;

[0154] 20: land portion;

[0155] 21: center land portion;

[0156] 22: second land portion;

[0157] 22a: first second land portion;

[0158] 22b: second second land portion;

[0159] 23: shoulder land portion;

[0160] 30: circumferential groove;

[0161] 31: inner circumferential groove;

[0162] 31a: first inner circumferential groove;

[0163] 31b: second inner circumferential groove;

[0164] 32, 50a: long strip portion;

[0165] 33, 50b: short strip portion;

[0166] 35: outer circumferential groove;

[0167] 40: cross groove;

[0168] 42: curved cross groove;

[0169] 43, 51: curved portion;

[0170] 44: communicating cross groove;

[0171] 50: circumferential fine groove;

[0172] 60: sipe.

Claims

1. A tire, characterized in that, have: Multiple circumferential grooves extend along the tire's circumference; Multiple transverse grooves extend along the width of the tire; Multiple circumferential sections are divided by the circumferential grooves and the transverse grooves; as well as Circumferential grooves extend along the tire circumference and are disposed in the annular portion. At least one of the circumferential grooves that divides the annular portion having the circumferential grooves extends along the tire circumferential direction and undulates in the tire width direction, thereby forming a serrated shape with long and short sections of relatively different lengths. The circumferential groove has one or more bends within the annular portion where the direction of extension changes, thereby having long and short sections of relatively different lengths. The inclination direction of the elongated portion of the circumferential groove relative to the tire circumference in the tire width direction is opposite to the inclination direction of the elongated portion of the circumferential groove relative to the tire circumference in the tire width direction. The circumferential land includes a second circumferential land located between a first inner circumferential groove and an outer circumferential groove adjacent in the tire width direction. A curved rib groove is disposed in the second circumferential land. One end of the curved rib groove opens into the outer circumferential groove, and the other end of the curved rib groove terminates within the second circumferential land. The curved rib groove has two curved portions, and the two curved portions bend in the same direction in the groove width direction of the curved rib groove. The bending angle of the two curved portions is greater than 90°.

2. The tire according to claim 1, wherein, The two circumferential grooves that divide the tire width direction of the annular portion, which is equipped with the circumferential grooves, are both formed in a sawtooth shape. The elongated portion of the circumferential groove has an inclination direction relative to the tire circumference towards the tire width direction, which is opposite to the inclination direction relative to the tire circumference of the elongated portion of the circumferential groove located on the inner side of the tire width direction among the two circumferential grooves that divide the tire width direction on both sides of the circumferential groove of the annular portion on which the circumferential groove is disposed.

3. The tire according to claim 1 or 2, wherein, At least one end of the circumferential groove opens into the transverse groove.

4. The tire according to claim 1 or 2, wherein, The circumferential groove has at least one point of varying depth within the circumferential portion.

5. The tire according to claim 1 or 2, wherein, The elongated portion of the circumferential groove has an inclination of more than 5° and less than 45° relative to the tire circumference in the tire width direction.

6. The tire according to claim 1 or 2, wherein, The inclination of the elongated portion of the circumferential groove relative to the tire circumference in the tire width direction is within the range of 5° or more and 30° or less.

7. The tire according to claim 1 or 2, wherein, At least one of the curved portions of the circumferential groove has a bending angle of 90° or more.

8. The tire according to claim 1 or 2, wherein, For the circumferential groove, the total length of the elongated portion of a circumferential groove is within the range of more than 60% and less than 90% of the total length of the circumferential groove.

9. The tire according to claim 1 or 2, wherein, The curved portion of the circumferential groove is disposed within a range of 40% of the maximum width of the circumferential shore portion in the tire width direction, centered on the center of the circumferential shore portion on which the circumferential groove is disposed.

10. The tire according to claim 1 or 2, wherein, The width of the circumferential groove is between 3.5 mm and 12 mm. The width of the circumferential groove is between 1.5 mm and 4 mm.

11. The tire according to claim 1 or 2, wherein, The circumferential section is provided with multiple sipes extending along the width of the tire.

12. The tire according to claim 11, wherein, The groove pattern is inclined relative to the tire circumference in a direction opposite to the inclination direction of the elongated portion of the circumferential groove relative to the tire circumference in the tire width direction.

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