tire

Abstract

To improve dry running performance while ensuring snow and ice performance. [Solution] The tire has four circumferential grooves (31A, 31B, 32A, 32B), five land portions (21, 22A, 22B, 23A, 23B), a first center lug groove (42) of a center land portion (21), a second center lug groove (43) of the center land portion (21), one middle lug groove (41) of one middle land portion (22A), the other first middle lug groove (44) of the other middle land portion (22B), the other second middle lug groove (45) of the other middle land portion (22B), and a center The land portion 21 includes a center communicating sipe 52 and one of the middle land portions 22 includes a middle communicating sipe 51, and the lug grooves 41, 42, 44, 45 are arranged with their inclination directions in the tire width direction alternately in opposite directions, the lug grooves 42, 43 are arranged in fewer numbers in the tire circumferential direction than the other lug grooves 41, 44, 45, and the circumferential grooves 32A have groove walls 32Aa between the multiple lug grooves 41 inclined in the same direction in the tire circumferential direction.

Description

[Technical Field]

[0001] The present invention relates to tires. [Background technology]

[0002] For example, the tire described in Patent Document 1 has a tread pattern in which five ribs are formed by four circumferential grooves, and the three ribs on the inner side in the tire width direction have lug grooves, one end of which connects to the circumferential groove and the other end of which terminates within the rib. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-018605 Summary of the Invention [Problem to be solved by the invention]

[0004] Traditionally, studless tires have been focused on performance on ice, but there is also a demand for improved performance on snow. Generally, improving performance on ice requires improving adhesion friction, but this is achieved by increasing the actual contact area by reducing the groove area ratio, which has the drawback of worsening performance on snow. Furthermore, in recent years, studless tires are also required to improve safety during high-speed driving (dry driving).

[0005] An object of the present invention is to provide a tire that can improve dry running performance while ensuring snow and ice performance by optimizing the pattern configuration. [Means for solving the problem]

[0006] In order to achieve the above object, a tire according to one aspect of the present invention includes one center circumferential groove and the other center circumferential groove formed linearly along the tire circumferential direction and adjacent to each other on either side of the tire equatorial plane, one shoulder circumferential groove and the other shoulder circumferential groove formed linearly along the tire circumferential direction and defined on the tire width direction outer side of each of the center circumferential grooves, a center land portion defined between the center circumferential grooves and continuing in the tire circumferential direction, and one shoulder circumferential groove defined between the shoulder circumferential groove and the center circumferential groove and continuing in the tire circumferential direction. a middle land portion and an other middle land portion, one shoulder land portion and the other shoulder land portion defined on the tire width direction outer side of each shoulder circumferential groove, a first center lug groove extending along the tire width direction in the center land portion, a base end thereof communicating with one of the center circumferential grooves and a tip end thereof terminating inside the center land portion, and a plurality of first center lug grooves arranged side by side in the tire circumferential direction in the center land portion, a base end thereof extending along the tire width direction in the center land portion, communicating with the other center circumferential groove, and a tip end thereof terminating inside the center land portion, and a plurality of first center lug grooves arranged side by side in the tire circumferential direction in the center land portion a second center lug groove; one middle lug groove arranged in a row in the tire circumferential direction in the one middle land portion, with a base end extending along the tire width direction in the one middle land portion communicating with the one shoulder circumferential groove and a tip end terminating inside the one middle land portion; a second first middle lug groove arranged in a row in the tire circumferential direction in the other middle land portion, with a base end extending along the tire width direction in the other middle land portion communicating with the other center circumferential groove and a tip end terminating inside the other middle land portion; a second center lug groove that is connected to the first center lug groove and terminates at the inside of the other middle land portion, the second center lug grooves being arranged in a row in the tire circumferential direction; a center connecting sipe that extends from the tip of the first center lug groove in the center land portion to connect to the other center circumferential groove; and a middle connecting sipe that extends from the tip of one middle lug groove in the one middle land portion to connect to the one center circumferential groove, and the one middle lug groove, the first center lug groove, the other first middle lug groove, and the other second middle lug groove areThe inclination directions with respect to the tire width direction are alternately opposite, the first center lug grooves and the second center lug grooves are arranged in a smaller number in the tire circumferential direction than the other lug grooves, and the one shoulder circumferential groove is formed such that each groove wall between the plurality of one middle lug grooves is inclined in the same direction with respect to the tire circumferential direction. [Effects of the Invention]

[0007] According to this invention, it is possible to improve dry running performance while ensuring snow and ice performance. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a meridian cross-sectional view of a pneumatic tire according to an embodiment. [Figure 2] FIG. 2 is a plan view of a tread portion of the pneumatic tire according to the first embodiment. [Figure 3] FIG. 3 is a cross-sectional view of each circumferential groove of the pneumatic tire according to the first embodiment. [Figure 4] FIG. 4 is a cross-sectional view of each lug groove of the pneumatic tire according to the first embodiment. [Figure 5] FIG. 5 is a plan view of a tread portion of a pneumatic tire according to the second embodiment. [Figure 6] FIG. 6 is a partially enlarged plan view of a tread of a pneumatic tire according to the second embodiment. [Figure 7] FIG. 7 is a partial cross-sectional view of a pneumatic tire according to the second embodiment. [Figure 8] FIG. 8 is a partial cross-sectional view showing the operation of the pneumatic tire according to the second embodiment. [Figure 9] FIG. 9 is a partial cross-sectional view showing the operation of a typical pneumatic tire. [Figure 10] FIG. 10 is a cross-sectional view showing the shape of the bottom of a wide sipe. [Figure 11] FIG. 11 is a cross-sectional view showing another example of the bottom shape of the wide sipe. [Figure 12] FIG. 12 is a cross-sectional view showing another example of the bottom shape of the wide sipe. [Figure 13] FIG. 13 is a partially enlarged plan view of another example of the tread of the pneumatic tire according to the second embodiment. [Figure 14] FIG. 14 is a partially enlarged plan view of another example of the tread of the pneumatic tire according to the second embodiment. [Figure 15] FIG. 15 is a table showing the results of a performance test of the pneumatic tire according to the embodiment. [Figure 16] FIG. 16 is a table showing the results of a performance test of the pneumatic tire according to the embodiment. [Figure 17] FIG. 17 is a table showing the results of a performance test of the pneumatic tire according to the embodiment. [Figure 18] FIG. 18 is a table showing the results of a performance test of the pneumatic tire according to the embodiment. [Figure 19] FIG. 19 is a table showing the results of a performance test of the pneumatic tire according to the embodiment. [Figure 20] FIG. 20 is a table showing the results of a performance test of the pneumatic tire according to the embodiment. [Figure 21] FIG. 21 is a table showing the results of a performance test of the pneumatic tire according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to these embodiments. Furthermore, the components of these embodiments include those that can be substituted and are obvious substitutes while maintaining the identity of the invention. Furthermore, the multiple modifications described in these embodiments can be arbitrarily combined within the scope obvious to those skilled in the art.

[0010] In the following description, the tire radial direction refers to the direction perpendicular to the tire rotational axis (not shown), which is the rotational axis of the pneumatic tire 1 of this embodiment. The tire radial inner side refers to the side toward the tire rotational axis in the tire radial direction, and the tire radial outer side refers to the side away from the tire rotational axis in the tire radial direction. The tire circumferential direction refers to the direction around the tire rotational axis as the central axis. The tire width direction refers to the direction parallel to the tire rotational axis. The tire width inner side refers to the side toward the tire equatorial plane (tire equator line) CL in the tire width direction, and the tire width outer side refers to the side away from the tire equatorial plane CL in the tire width direction. The tire equatorial plane CL is a plane that is perpendicular to the tire rotational axis and passes through the center of the tire width of the pneumatic tire 1. The tire equatorial plane CL coincides in position in the tire width direction with the tire width centerline, which is the center position of the pneumatic tire 1 in the tire width direction. The tire equator line refers to a line that is on the tire equatorial plane CL and runs along the tire circumferential direction of the pneumatic tire 1. Also, a cross section in the tire meridian direction (meridian cross section) refers to a cross section of the tire cut by a plane including the tire rotation axis.

[0011] As shown in FIG. 1, a pneumatic tire 1 of the embodiment has a tread portion 2, a sidewall portion 8, and a bead portion 10.

[0012] The tread portion 2 is disposed at the outermost portion in the tire radial direction when viewed in a tire meridian cross section. The tread portion 2 has tread rubber 2A made of a rubber composition. The surface of the tread portion 2, i.e., the portion that comes into contact with the road surface when a vehicle (not shown) equipped with the pneumatic tire 1 is running, is formed as a tread contact surface (also referred to as a tread surface) 2B. The tread contact surface 2B forms part of the contour of the pneumatic tire 1. The tread portion 2 has shoulder portions 2C formed at both outer ends in the tire width direction.

[0013] The sidewall portions 8 are disposed on both sides in the tire width direction of the tread portion 2 and on the inner side in the tire radial direction of the shoulder portions 2C. The sidewall portions 8 are disposed in two locations on both sides in the tire width direction of the pneumatic tire 1, and form the outermost exposed portions of the pneumatic tire 1 in the tire width direction.

[0014] The bead portions 10 are disposed on the radially inner side of each sidewall portion 8. Like the sidewall portions 8, the bead portions 10 are disposed at two locations on both sides in the tire width direction. Each bead portion 10 is provided with a bead core 11, and a bead filler 12 is provided on the radially outer side of the bead core 11 in the tire radial direction. The bead core 11 is an annular member formed by bundling bead wires, which are steel wires, into a circular shape. The bead filler 12 is a rubber member disposed on the radially outer side of the bead core 11 in the tire radial direction.

[0015] The pneumatic tire 1 has an internal structure including a belt layer 14 and a carcass layer 13 .

[0016] The belt layer 14 is disposed on the tread rubber 2A of the tread portion 2. The belt layer 14 has a multi-layer structure in which a plurality of belts 141, 142 and a belt cover 143 are laminated. In this embodiment, the belt layer 14 has two layers of belts 141, 142 laminated together.

[0017] The belts 141 and 142 are formed by covering a plurality of belt cords made of steel or organic fiber material such as polyester, rayon, or nylon with a coating rubber and rolling the covered belt cords. The belt angles of the belts 141 and 142, defined as the inclination angle of the belt cords relative to the tire circumferential direction, are within a predetermined range (for example, 20° to 55°). The belt angles of the belts 141 and 142 are different from each other. For this reason, the belts 141 and 142 are formed as a so-called cross-ply structure (cross belt) in which the inclination directions of the belt cords are layered crossing each other.

[0018] The belt cover 143 is formed by covering a plurality of belt cover cords made of steel or organic fiber material such as polyester, rayon, or nylon with coating rubber and rolling the covered cords. The belt cover 143 has a belt angle, defined as the inclination angle of the belt cover cords with respect to the tire circumferential direction, within a predetermined range (for example, 0° to 10°). The belt cover 143 is formed, for example, by spirally winding a strip material, made of one or more belt cover cords covered with coating rubber, around the tire radially outer side of the two-layer belts 141 and 142 in the tire circumferential direction.

[0019] The carcass layer 13 is disposed continuously on the radially inner side of the belt layer 14 in the tread portion 2, the sidewall portion 8, and the bead portion 10. Both ends of the carcass layer 13 in the tire width direction are wound back and secured to the outer side in the tire width direction so as to enclose the bead cores 11 and bead fillers 12 of both bead portions 10, and are wound around the tire circumferentially in a toroidal shape to form the tire framework. The carcass layer 13 has a single-layer structure consisting of one carcass ply or a multi-layer structure consisting of multiple carcass plies stacked together. The carcass ply of the carcass layer 13 is formed by coating multiple carcass cords made of steel or organic fiber material such as aramid, nylon, polyester, or rayon with coating rubber and rolling them. The carcass cords that make up the carcass ply are arranged side by side at an angle to the tire circumferential direction, with the angle aligned along the tire meridian direction.

[0020] A rim cushion rubber 17 is arranged on the radially inner side and the widthwise outer side of the turned-up portion of the carcass layer 13. The rim cushion rubber 17 forms the contact surface of the bead portion 10 with the rim flange. An inner liner 16 is formed along the carcass layer 13 on the inner side of the carcass layer 13. The inner liner 16 forms the tire inner surface 18, which is the inner surface of the pneumatic tire 1.

[0021] 1 and 2, a pneumatic tire 1 of the embodiment has a tread pattern on a tread contact surface 2B of a tread portion 2. Here, each dimension of the tread pattern is measured in an unloaded state with the tire mounted on a specified rim and inflated to a specified internal pressure.

[0022] Specified rim refers to the "standard rim" specified by JATMA, the "design rim" specified by TRA, or the "measuring rim" specified by ETRTO. Specified internal pressure refers to the "maximum air pressure" specified by JATMA, the maximum value of the "tire load limits at various cold inflation pressures" specified by TRA, or the "inflation pressures" specified by ETRTO. Specified load refers to the "maximum load capacity" specified by JATMA, the maximum value of the "tire load limits at various cold inflation pressures" specified by TRA, or the "load capacity" specified by ETRTO.

[0023] The groove width (also called the open groove width) is measured as the maximum distance between the opposing groove walls at the groove opening at the tread contact surface 2B when the tire is mounted on a specified rim, inflated to a specified internal pressure, and in an unloaded state. In addition, when the groove opening has a notch or chamfer, the groove width is measured using the intersection of an extension of the tread contact surface 2B and an extension of the groove wall as the endpoint in a cross section parallel to the tire width direction and the tire radial direction.

[0024] The groove depth is measured as the maximum distance from the tread contact surface 2B to the groove bottom when the tire is mounted on a specified rim, inflated to a specified internal pressure, and under no load. If the tire has partial unevenness or sipes at the groove bottom, the groove depth is measured excluding these.

[0025] [Embodiment 1] 1 and 2, the pneumatic tire 1 of the first embodiment mainly includes, as a tread pattern, a center circumferential groove 31 and shoulder circumferential grooves 32. Each of the circumferential grooves 31, 32 may be defined as a groove obligated to display a wear indicator as defined by JATMA.

[0026] The center circumferential groove 31 extends along the tire circumferential direction and has an annular structure provided continuously around the entire tire circumference. Two center circumferential grooves 31 are provided parallel to each other in the tire width direction with the tire equatorial plane CL sandwiched between them. The center circumferential grooves 31 are formed linearly along the tire circumferential direction without any bends. As shown in FIG. 3, the center circumferential groove 31 has a maximum groove width W of 3.0 mm or more and 13.0 mm or less in a cross section perpendicular to the tire circumferential direction, and a groove depth D of 7.0 mm or more and 10.0 mm or less.

[0027] The shoulder circumferential grooves 32 extend in the tire circumferential direction and have an annular structure that is continuously provided around the entire tire circumference. The shoulder circumferential grooves 32 are provided in parallel in the tire width direction on the outer side of the two center circumferential grooves 31 in the tire width direction, with the tire equatorial plane CL sandwiched between them. The shoulder circumferential grooves 32 are formed in straight lines without any bends along the tire circumferential direction. As shown in FIG. 3 , the shoulder circumferential grooves 32 have a maximum groove width W of 3.0 mm or more and 13.0 mm or less in a cross section perpendicular to the tire circumferential direction, and a groove depth D of 7.0 mm or more and 10.0 mm or less.

[0028] In the pneumatic tire 1 of the embodiment, a plurality of land portions 20 are defined in the tread portion 2 by two center circumferential grooves 31 and two shoulder circumferential grooves 32. The land portions 20 include a center land portion 21, a middle land portion 22, and a shoulder land portion 23. The center land portion 21 is formed between the two center circumferential grooves 31 in a single rib-like row along the tire circumferential direction, including the tire equatorial plane CL. The middle land portion 22 is defined between one center circumferential groove 31 and one shoulder circumferential groove 32, and is formed in a total of two rib-like rows along the tire circumferential direction on both outer sides of the center land portion 21 in the tire width direction. The shoulder land portions 23 are defined on the outer side of each shoulder circumferential groove 32 in the tire width direction, and are formed in a single rib-like row along the tire circumferential direction on the outer side of each middle land portion 22 in the tire width direction, for a total of two rows. The shoulder land portions 23 include the ground contact edges T.

[0029] Here, the ground contact edges T refer to the outermost ends in the tire width direction in the area where the tread contact surface 2B of the pneumatic tire 1 comes into contact with the road surface when the pneumatic tire 1 is mounted on a standard rim, inflated to a standard internal pressure, and subjected to 70% of a standard load, and are continuous in the tire circumferential direction.

[0030] Furthermore, the pneumatic tire 1 of the embodiment has a specified orientation relative to the vehicle width direction when mounted on a vehicle. The pneumatic tire 1 of the embodiment has a defined orientation relative to the vehicle width direction (tire width direction) when mounted on a vehicle, i.e., a defined inner side and outer side in the vehicle width direction. Specifically, the pneumatic tire 1 includes a mounting direction indicator (not shown) that indicates the mounting direction of the tire on the vehicle. The mounting direction indicator is configured, for example, by a mark or a concavo-convex portion attached to the sidewall portion of the tire. For example, Article 30 of the Economic Commission for Europe Regulation (ECER) requires that a vehicle mounting direction indicator be provided on the sidewall portion that will be on the outer side in the vehicle width direction when mounted on a vehicle. Note that in the embodiment, the outer side in the vehicle width direction may be expressed as "one side" and the inner side in the vehicle width direction as "the other side." This does not exclude the use of "one side" and "the other side" in reverse, referring to the inner and outer sides in the vehicle width direction.

[0031] Therefore, in the pneumatic tire 1 of the embodiment, the center circumferential groove 31 is a center circumferential groove (also referred to as an outer center circumferential groove or one of the center circumferential grooves) 31A on the outer side in the vehicle width direction, and a center circumferential groove (also referred to as an inner center circumferential groove or the other of the center circumferential grooves) 31B on the inner side in the vehicle width direction. Also, in the pneumatic tire 1 of the embodiment, the shoulder circumferential grooves 32 are a shoulder circumferential groove (also referred to as an outer shoulder circumferential groove or one of the shoulder circumferential grooves) 32A on the outer side in the vehicle width direction, and a shoulder circumferential groove (also referred to as an inner shoulder circumferential groove or the other of the shoulder circumferential grooves) 32B on the inner side in the vehicle width direction.

[0032] In addition, in the pneumatic tire 1 of the embodiment, the middle land portion 22 is made up of an outer middle land portion in the vehicle width direction (also referred to as an outer middle land portion or one middle land portion) 22A and an inner middle land portion in the vehicle width direction (also referred to as an inner middle land portion or the other middle land portion) 22B. In addition, in the pneumatic tire 1 of the embodiment, the shoulder land portions 23 are made up of an outer shoulder land portion in the vehicle width direction (also referred to as an outer shoulder land portion or one shoulder land portion) 23A and an inner shoulder land portion in the vehicle width direction (also referred to as an inner shoulder land portion or the other shoulder land portion) 23B.

[0033] As shown in FIG. 2, the pneumatic tire 1 of the embodiment has an outer middle lug groove (also referred to as one middle lug groove) 41, a middle connecting sipe 51, and an outer middle sipe (also referred to as one middle sipe) 61a (sipe 61) provided in the outer middle land portion 22A.

[0034] The outer middle lug groove 41 extends along the tire width direction, with its base end 41a communicating with the outer shoulder circumferential groove 32A and its tip end 41b terminating inside the outer middle land portion 22A, so that it does not penetrate the outer middle land portion 22A. The outer middle lug groove 41 is formed at an angle with respect to the tire width direction. The outer middle lug groove 41 has a widest groove width at its base end 41a and gradually decreases in width toward its tip end 41b. Multiple outer middle lug grooves 41 are formed side by side in the tire circumferential direction at intervals. The angle θ1 of the centerline of each outer middle lug groove 41 with respect to the tire width direction is in the range of 10°≦θ1≦40°. This angle θ1 is expressed as an absolute value and can be either positive or negative with respect to the tire width direction. In the embodiment, the outer middle lug groove 41 is formed to extend linearly, but it is not limited to a linear shape and may be bent or curved. When the outer middle lug groove 41 is bent or curved, the angle θ1 of the outer middle lug groove 41 is based on the center line of the straight line connecting the base end 41a and the tip end 41b. As shown in Figures 2 and 4, the outer middle lug groove 41 has a maximum groove width W1 of 1.5 mm to 7.0 mm in a cross section perpendicular to the center line, and a groove depth D1 of 7.0 mm to 10.0 mm.

[0035] The outer middle lug groove 41 has a maximum length L1 in the tire width direction and a maximum dimension La in the tire width direction of the outer middle land portion 22A that satisfies the relationship 0.50≦L1 / La≦0.90.

[0036] The outer shoulder circumferential groove 32A, which is connected to the outer middle lug groove 41, has groove walls 32Aa formed between the multiple outer middle lug grooves 41 such that the groove walls 32Aa on the outer middle land portion 22A side are inclined in the same direction relative to the tire circumferential direction. That is, the groove walls 32Aa of the outer shoulder circumferential groove 32A on the outer middle land portion 22A side (inner side in the vehicle width direction) are formed so that they gradually increase and decrease in the tire circumferential direction between the outer middle lug grooves 41, and all are formed in the same inclination direction. Therefore, the groove walls 32Aa of the outer shoulder circumferential groove 32A on the outer middle land portion 22A side are formed in a jagged shape along the tire circumferential direction. Note that the groove walls of the outer shoulder circumferential groove 32A on the outer shoulder land portion side are formed linearly (parallel) along the tire circumferential direction. The other circumferential grooves 31A, 31B, and 32B have groove walls formed linearly (parallel) along the tire circumferential direction.

[0037] The middle communicating sipe 51 extends linearly without bending from the tip 41b of the outer middle lug groove 41 along the extension direction of the outer middle lug groove 41, and communicates with the outer center circumferential groove 31A. The middle communicating sipe 51 has a width of 0.3 mm or more and 1.5 mm or less, and a depth of 2.0 mm or more and 10.0 mm or less.

[0038] The outer middle sipes 61a extend along (in the embodiment, parallel to) the slope of the outer middle lug grooves 41, and a plurality of outer middle sipes 61a are arranged side by side in the tire circumferential direction. The ends of the outer middle sipes 61a may terminate inside the outer middle land portion 22A, or may communicate with the outer center circumferential groove 31A or the outer shoulder circumferential groove 32A.

[0039] The sipes 61, including the outer middle sipes 61a, may have a shape at the tread contact surface 2B that is linear, curved, wavy, or zigzag. The sipes 61 may have a shape inside the tread rubber 2A that is linear or uneven in the depth direction or extension direction. In this embodiment, the sipes 61 are formed in a zigzag shape at the tread contact surface 2B, and are formed in a linear or uneven shape inside the tread rubber 2A. The sipes 61 have a width of 1.0 mm or less and a depth of 2.0 mm or more and 10.0 mm or less.

[0040] Furthermore, the "sipes" referred to in the embodiments are formed in the shape of narrow grooves in the tread contact surface 2B, and when the pneumatic tire 1 is mounted on a specified rim and under specified internal pressure conditions, the wall surfaces constituting the narrow grooves may not come into contact with each other when no load is applied; however, when a load is applied vertically on a flat plate and the narrow groove is located in the contact surface formed on the flat plate, or when the land portion where the narrow groove is formed collapses, the wall surfaces constituting the narrow grooves, or at least a portion of the portion provided on the wall surface, come into contact with each other due to deformation of the land portion.

[0041] As shown in FIG. 2, the pneumatic tire 1 of the embodiment has a center land portion 21 provided with first center lug grooves 42, second center lug grooves 43, center communicating sipes 52, and center sipes 61b (sipes 61).

[0042] The first center lug grooves 42 extend along the tire width direction, with their base ends 42a communicating with the outer center circumferential groove 31A and their tips 42b terminating inside the center land portion 21, so that they do not penetrate the center land portion 21. The first center lug grooves 42 are formed at an angle with respect to the tire width direction. The first center lug grooves 42 are formed so that their groove width is widest at their base ends 42a and gradually decreases toward their tips 42b. Multiple first center lug grooves 42 are formed side by side in the tire circumferential direction at intervals. The angle θ2 of the center line of each of the first center lug grooves 42 with respect to the tire width direction is in the range of 10°≦θ2≦40°. This angle θ2 is expressed as an absolute value and has either a positive or negative angle with respect to the tire width direction. In the embodiment, the first center lug grooves 42 are formed to extend linearly, but they may be bent or curved, not limited to a linear shape. When the first center lug grooves 42 are bent or curved, the angle θ2 of the first center lug grooves 42 is based on the center line of the straight line connecting the base end 42a and the tip end 42b. As shown in Figures 2 and 4, the first center lug grooves 42 have a maximum groove width W2 of 1.5 mm to 7.0 mm in a cross section perpendicular to the center line, and a groove depth D2 of 7.0 mm to 10.0 mm.

[0043] Furthermore, the maximum length L2 of the first center lug groove 42 in the tire width direction and the maximum dimension Lb of the center land portion 21 in the tire width direction satisfy the relationship 0.55≦L2 / Lb≦0.95.

[0044] The second center lug grooves 43 extend along the tire width direction, with their base ends 43a communicating with the inner center circumferential groove 31B and their tips 43b terminating inside the center land portion 21, so that they do not penetrate the center land portion 21. The second center lug grooves 43 are formed at an angle with respect to the tire width direction. The second center lug grooves 43 are formed so that their groove width is narrowest at their base ends 43a and gradually increases toward their tips 43b. Multiple second center lug grooves 43 are formed side by side in the tire circumferential direction at intervals. In the embodiment, the second center lug grooves 43 are formed to extend linearly, but may be formed to be bent or curved, not limited to a linear shape. The second center lug grooves 43 are arranged so that their positions in the tire width direction do not coincide with those of the first center lug grooves 42, and they are alternately arranged in the tire circumferential direction.

[0045] The center communicating sipe 52 extends linearly without bending from the tip 42b of the first center lug groove 42 along the extension direction of the first center lug groove 42, and communicates with the inner center circumferential groove 31B. The center communicating sipe 52 has a width of 0.3 mm or more and 1.5 mm or less, and a depth of 2.0 mm or more and 10.0 mm or less.

[0046] The center sipes 61b extend along (in the embodiment, parallel to) the inclination of the first center lug grooves 42, and a plurality of center sipes 61b are arranged side by side in the tire circumferential direction. The ends of the center sipes 61b may terminate inside the center land portion 21, or may communicate with the outer center circumferential groove 31A or the inner center circumferential groove 31B.

[0047] As shown in FIG. 2, the pneumatic tire 1 of the embodiment has an inner first middle lug groove (also referred to as the other first middle lug groove) 44, an inner second middle lug groove (also referred to as the other second middle lug groove) 45, an inner first middle sipe (also referred to as the other first middle sipe) 61c (sipe 61), and an inner second middle sipe (also referred to as the other second middle sipe) 61d (sipe 61) in the inner middle land portion 22B.

[0048] The inner first middle lug groove 44 extends along the tire width direction, with its base end 44a communicating with the inner center circumferential groove 31B and its tip end 44b terminating inside the inner middle land portion 22B, thereby not penetrating the inner middle land portion 22B. The inner first middle lug groove 44 is formed at an angle with respect to the tire width direction. The inner first middle lug groove 44 has a widest groove width at its base end 44a and gradually decreases in width toward its tip end 44b. Multiple inner first middle lug grooves 44 are arranged side by side in the tire circumferential direction at intervals. The inner first middle lug grooves 44 have a centerline angle θ3 with respect to the tire width direction in the range of 5°≦θ3≦35°. This angle θ3 is expressed as an absolute value and can be either positive or negative with respect to the tire width direction. In the embodiment, the inner first middle lug groove 44 is formed to extend linearly, but it may be bent or curved. When the inner first middle lug groove 44 is bent or curved, the angle θ3 of the inner first middle lug groove 44 is based on the center line of the straight line connecting the base end 44a and the tip end 44b. As shown in Figures 2 and 4, the inner first middle lug groove 44 has a maximum groove width W3 of 1.5 mm to 7.0 mm in a cross section perpendicular to the center line and a groove depth D3 of 4.0 mm to 10.0 mm. The inner first middle lug groove 44 has a raised bottom.

[0049] The maximum length L3 of the inner first middle lug groove 44 in the tire width direction and the maximum dimension Lc of the inner middle land portion 22B in the tire width direction satisfy the relationship 0.30≦L3 / Lc≦0.70.

[0050] The base ends 44a of every other inner first middle lug groove 44 in the tire circumferential direction face the base ends 43a of the second center lug grooves 43 in the tire width direction, with the inner center circumferential groove 31B as the boundary. That is, every other inner first middle lug groove 44 in the tire circumferential direction is arranged contiguous with the second center lug groove 43, with the inner center circumferential groove 31B as the boundary. The second center lug grooves 43 are inclined in the same direction as the inner first middle lug grooves 44, have a centerline angle with respect to the tire width direction of 5° to 35°, have a maximum groove width of 1.5 mm to 7.0 mm, and have a groove depth of 7.0 mm to 10.0 mm.

[0051] The inner second middle lug groove 45 extends along the tire width direction, with its base end 45a communicating with the inner shoulder circumferential groove 32B and its tip end 45b terminating inside the inner middle land portion 22B, thereby not penetrating the inner middle land portion 22B. The inner second middle lug groove 45 is formed at an angle with respect to the tire width direction. The inner second middle lug groove 45 has a widest groove width at its base end 45a and gradually decreases in width toward its tip end 45b. Multiple inner second middle lug grooves 45 are arranged side by side in the tire circumferential direction at intervals. The inner second middle lug grooves 45 have a centerline angle θ4 with respect to the tire width direction in the range of 1°≦θ4≦20°. This angle θ4 is expressed as an absolute value and can be either positive or negative with respect to the tire width direction. In the embodiment, the inner second middle lug groove 45 is formed to extend linearly, but it may be bent or curved. When the inner second middle lug groove 45 is bent or curved, the angle θ4 of the inner second middle lug groove 45 is based on the center line of the straight line connecting the base end 45a and the tip end 45b. As shown in Figures 2 and 4, the inner second middle lug groove 45 has a maximum groove width W4 of 1.5 mm to 7.0 mm in a cross section perpendicular to the center line, and a groove depth D4 of 7.0 mm to 10.0 mm.

[0052] The maximum length L4 of the inner second middle lug groove 45 in the tire width direction and the maximum dimension Lc of the inner middle land portion 22B in the tire width direction satisfy the relationship 0.10≦L4 / Lc≦0.50.

[0053] The inner second middle lug grooves 45 and the inner first middle lug grooves 44 are arranged alternately in the tire circumferential direction.

[0054] The inner first middle sipes 61c extend along (in the embodiment, parallel to) the slope of the inner first middle lug grooves 44, and a plurality of inner first middle sipes 61c are arranged side by side in the tire circumferential direction. An end of each inner first middle sipe 61c may terminate inside the inner middle land portion 22B, or one end may be connected to the inner center circumferential groove 31B.

[0055] The inner second middle sipes 61d extend along (in the embodiment, parallel to) the slope of the inner second middle lug groove 45, and a plurality of them are provided side by side in the tire circumferential direction. An end of the inner second middle sipe 61d may terminate inside the inner middle land portion 22B, or one end may be connected to the inner shoulder circumferential groove 32B.

[0056] The inner second middle sipe 61d may be connected to the inner first middle sipe 61c at the other end, but in this embodiment, they are arranged at an interval in the tire width direction.

[0057] As shown in Figure 2, the pneumatic tire 1 of the embodiment has an outer shoulder lug groove (also referred to as one shoulder lug groove) 46, an outer shoulder sipe (also referred to as one shoulder sipe) 61e (sipe 61), and an outer shoulder circumferential groove 71 provided in the outer shoulder land portion 23A.

[0058] The outer shoulder lug grooves 46 extend along the tire width direction, with their base ends 46a communicating with the outer shoulder circumferential groove 32A and extending outward in the tire width direction, passing through the ground contact edge T. The outer shoulder lug grooves 46 are formed at an angle with respect to the tire width direction. Multiple outer shoulder lug grooves 46 are arranged side by side in the tire circumferential direction at intervals. The base ends 46a of the outer shoulder lug grooves 46 face the base ends 41a of the outer middle lug grooves 41 in the tire width direction, with the outer shoulder circumferential groove 32A as the boundary. In other words, the same number of outer shoulder lug grooves 46 as the outer middle lug grooves 41 are arranged, and they are continuous with the outer middle lug grooves 41, with the outer shoulder circumferential groove 32A as the boundary. The outer shoulder lug grooves 46 are inclined in the opposite direction to the outer middle lug grooves 41, and the angle of the center line relative to the tire width direction is in the range of 1° to 15°, the maximum groove width in the cross section perpendicular to the center line is 1.5 mm to 7.0 mm, and the groove depth is 5.0 mm to 10.0 mm.

[0059] The outer shoulder sipes 61e extend along (in the embodiment, parallel to) the slope of the outer shoulder lug grooves 46, and a plurality of outer shoulder sipes 61e are provided side by side in the tire circumferential direction. The ends of the outer shoulder sipes 61e may terminate inside the outer shoulder land portion 23A, or may communicate with the outer shoulder circumferential groove 32A.

[0060] The outer shoulder circumferential grooves 71 are arranged linearly without any bends along the tire circumferential direction between the outer shoulder circumferential groove 32A and the ground contact edge T. They are arranged between the outer shoulder lug grooves 46 that are aligned in the tire circumferential direction, with one end communicating with one of the outer shoulder lug grooves 46 and the other end terminating inside the outer shoulder land portion 23A. The outer shoulder circumferential grooves 71 are aligned in a row in the tire circumferential direction. The outer shoulder circumferential grooves 71 do not communicate with the outer shoulder sipes 61e but divide the outer shoulder sipes 61e in the tire width direction. The outer shoulder circumferential grooves 71 have a groove width of 0.5 mm or more and 2.5 mm or less and a groove depth of 0.5 mm or more and 3.5 mm or less.

[0061] As shown in FIG. 2, the pneumatic tire 1 of the embodiment has an inner shoulder lug groove (also referred to as the other shoulder lug groove) 47, an inner shoulder sipe (also referred to as the other shoulder sipe) 61f (sipe 61), and an inner shoulder circumferential groove 72 provided in the inner shoulder land portion 23B.

[0062] The inner shoulder lug groove 47 extends along the tire width direction, with its base end 47a communicating with the inner shoulder circumferential groove 32B and extending outward in the tire width direction, passing through the ground contact edge T. The inner shoulder lug groove 47 is formed at an angle with respect to the tire width direction. Multiple inner shoulder lug grooves 47 are arranged side by side in the tire circumferential direction at intervals. The base end 47a of each inner shoulder lug groove 47 faces the base end 45a of the inner second middle lug groove 45 in the tire width direction, with the inner shoulder circumferential groove 32B as the boundary. In other words, the number of inner shoulder lug grooves 47 is the same as the number of inner second middle lug grooves 45, and they are arranged contiguous to the inner second middle lug groove 45, with the inner shoulder circumferential groove 32B as the boundary. The inner shoulder lug groove 47 is inclined in the same direction as the inner second middle lug groove 45, the angle of the center line with respect to the tire width direction is in the range of 1° to 15°, the maximum groove width in the cross section perpendicular to the center line is 1.5 mm to 7.0 mm, and the groove depth is 5.0 mm to 10.0 mm.

[0063] The inner shoulder sipes 61f extend along (in the embodiment, parallel to) the inner shoulder lug grooves 47, and a plurality of inner shoulder sipes 61f are provided side by side in the tire circumferential direction. The ends of the inner shoulder sipes 61f may terminate inside the inner shoulder land portion 23B, or may communicate with the inner shoulder circumferential groove 32B.

[0064] The inner shoulder circumferential groove 72 is arranged linearly without a bend along the tire circumferential direction between the inner shoulder circumferential groove 32B and the ground contact edge T, and is arranged between the inner shoulder lug grooves 47 arranged in the tire circumferential direction, with one end communicating with one of the inner shoulder lug grooves 47 and the other end terminating inside the inner shoulder land portion 23B. The inner shoulder circumferential grooves 72 are arranged in a line in the tire circumferential direction. The inner shoulder circumferential groove 72 does not communicate with the inner shoulder sipe 61f and divides the inner shoulder sipe 61f in the tire width direction. The inner shoulder circumferential groove 72 has a groove width of 0.5 mm or more and 2.5 mm or less and a groove depth of 0.5 mm or more and 3.5 mm or less.

[0065] When mounting the pneumatic tire 1 according to this embodiment on a vehicle, the pneumatic tire 1 is mounted on a rim wheel, filled with air, and mounted on the vehicle in an inflated state. When a vehicle mounted with the pneumatic tire 1 runs, the pneumatic tire 1 rotates while the lower tread contact surface 2B of the tread portion 2 comes into contact with the road surface. When a vehicle mounted with the pneumatic tire 1 runs on a dry road surface, the vehicle runs by transmitting driving force and braking force to the road surface and generating turning force mainly due to friction between the tread contact surface 2B and the road surface.

[0066] Furthermore, when traveling on a wet road surface, water between the tread surface 2B and the road surface enters each of the grooves 31, 32, 41, 42, 43, 44, 45, 46, 47 and the sipes 51, 52, 61, and the water between the tread surface 2B and the road surface is drained while traveling. This makes it easier for the tread surface 2B to make contact with the road surface, and the friction between the tread surface 2B and the road surface provides wet performance, enabling the vehicle to travel.

[0067] Furthermore, when traveling on snowy roads, the pneumatic tire 1 compacts snow on the road surface with the tread contact surface 2B, and snow on the road surface enters each of the grooves 31, 32, 41, 42, 43, 44, 45, 46, and 47, compacting the snow within the grooves. In this state, when driving or braking forces act on the pneumatic tire 1, or when a force acts in the tire width direction due to turning of the vehicle, a shear force acting on the snow in the grooves, known as snow column shear force, is generated between the pneumatic tire 1 and the snow. When traveling on snowy roads, this snow column shear force generates resistance between the pneumatic tire 1 and the road surface, allowing driving and braking forces to be transmitted to the road surface, ensuring snow traction and snow performance. This allows the vehicle to travel on snowy roads.

[0068] Furthermore, when traveling on snowy or icy roads, the tire also utilizes the edge effect of the grooves 31, 32, 41, 42, 43, 44, 45, 46, and 47 and the sipes 51, 52, and 61. That is, when traveling on snowy or icy roads, the tire also utilizes the resistance created by the edges of the grooves 31, 32, 41, 42, 43, 44, 45, 46, and 47 and the sipes 51, 52, and 61 catching on the snow or ice surface. When traveling on icy roads, the sipes 61 absorb water on the surface of the icy road, removing the water film between the icy road surface and the tread contact surface 2B, making it easier for the icy road surface and the tread contact surface 2B to come into contact. This increases the resistance between the tread contact surface 2B and the icy road surface due to frictional force and the edge effect, thereby providing ice performance. This allows the vehicle to travel on icy roads.

[0069] The grooves 31, 32, 41, 42, 43, 44, 45, 46, 47 and sipes 51, 52, 61 formed in the tread portion 2 contribute to ensuring driving performance when traveling on wet, snowy, or icy road surfaces, and therefore, in order to improve wet performance, i.e., driving performance on wet road surfaces, it is effective to increase the groove area of ​​the tread portion 2. In other words, if the groove area of ​​the grooves 31, 32, 41, 42, 43, 44, 45, 46, 47, etc. is increased, water on the road surface can easily enter the grooves when traveling on a wet road surface, thereby improving the drainage of water between the tread contact surface 2B and the road surface and improving wet performance.

[0070] Increasing the groove area also effectively improves snow performance, which is driving performance on snowy roads. In other words, increasing the groove area increases the amount of snow that can enter each groove 31, 32, 41, 42, 43, 44, 45, 46, and 47 when driving on snowy roads, thereby increasing the snow column shear force acting on the snow that has entered the grooves. This improves snow traction when driving on snowy roads, and improves snow performance.

[0071] The pneumatic tire 1 of the embodiment is characterized by having one center circumferential groove (outer center circumferential groove) 31A and the other center circumferential groove (inner center circumferential groove) 31B formed linearly along the tire circumferential direction and adjacent to each other on either side of the tire equatorial plane CL, one shoulder circumferential groove (outer shoulder circumferential groove) 32A and the other shoulder circumferential groove (inner shoulder circumferential groove) 32B formed linearly along the tire circumferential direction and defined on the outer side of each center circumferential groove 31A, 31B in the tire width direction, a center land portion 21 defined between each center circumferential groove 31A, 31B and continuing in the tire circumferential direction, one middle land portion (outer middle land portion) 22A and the other middle land portion (inner middle land portion) 22B defined between the adjacent shoulder circumferential grooves 32A, 32B and the center circumferential grooves 31A, 31B, respectively, and continuing in the tire circumferential direction, and each shoulder circumferential groove 32A,One shoulder land portion (outer shoulder land portion) 23A and the other shoulder land portion (inner shoulder land portion) 23B are defined on the tire width direction outer side of the center circumferential groove 31A and the other shoulder land portion (inner shoulder land portion) 23B, and in the center land portion 21, a base end 42a extending along the tire width direction is connected to one center circumferential groove 31A and a tip end 42b terminates inside the center land portion 21, and the first center lug grooves 42 are arranged side by side in the tire circumferential direction, and in the center land portion 21, a base end 43a extending along the tire width direction is connected to the other center circumferential groove 31B and a tip end 43 ... a plurality of second center lug grooves 43 arranged side by side in the tire circumferential direction; one middle lug groove (outer middle lug groove) 41 arranged side by side in the tire circumferential direction in one middle land portion 22A, with its base end 41a extending along the tire width direction communicating with one shoulder circumferential groove 32A and its tip end 41b terminating inside one middle land portion 22A; and a plurality of other first middle lug grooves arranged side by side in the tire circumferential direction in the other middle land portion 22B, with its base end 44a extending along the tire width direction communicating with the other center circumferential groove 31B and its tip end 44b terminating inside the other middle land portion 22B. The other middle lug groove (inner first middle lug groove) 44, the other second middle lug groove (inner second middle lug groove) 45 extending along the tire width direction in the other middle land portion 22B, with its base end 45a communicating with the other shoulder circumferential groove 32B and its tip end 45b terminating inside the other middle land portion 22B, and being arranged in a row in the tire circumferential direction, the center connecting sipe 52 extending from the tip 42b of the first center lug groove 42 in the center land portion 21 and communicating with the other center circumferential groove 31B, and the one middle land portion 22 extending from the tip 41b of one middle lug groove 41 in the one middle land portion 22 and a middle communicating sipe 51 communicating with one center circumferential groove 31A, and the one middle lug groove 41, the first center lug groove 42, the other first middle lug groove 44, and the other second middle lug groove 45 are arranged in alternating opposite directions with respect to the tire width direction, and the first center lug grooves 42 and second center lug grooves 43 are arranged in fewer numbers in the tire circumferential direction than the other lug grooves 41, 44, 45, and the one shoulder circumferential groove 32A is formed so that each groove wall 32Aa between the multiple one middle lug grooves 41 is inclined in the same direction with respect to the tire circumferential direction.

[0072] In the pneumatic tire 1 of the embodiment, the inclination directions of the lug grooves 41, 42, 44, and 45 of adjacent land portions 22A, 21, and 22B are not aligned in the same direction, preventing bias toward a specific angle and improving snow shear strength. Furthermore, by arranging communicating sipes 51 and 52 at the ends 41b and 42b of the lug grooves 41 and 42 inside the land portions 22A and 21, snow column shear strength is improved while ensuring the rigidity of the land portions 22A and 21, preventing collapse, and improving snow and ice performance and wear resistance. The communicating sipes 51 and 52 are located near the center of the tire width direction. Because this center affects traction performance when starting, having the communicating sipes 51 and 52 penetrate the land portions 22A and 21 improves traction performance on snow and ice. Furthermore, by providing fewer lug grooves 42, 43 in the center land portion 21 aligned in the tire circumferential direction than the other lug grooves 41, 44, 45, the lug grooves 42, 43 provide snow column shear force while ensuring the rigidity of the center land portion 21, thereby improving dry driving performance, i.e., steering stability on dry roads. Furthermore, in the circumferential grooves 32A, the groove walls 32Aa between the multiple lug grooves 41 are formed to be inclined in the same direction relative to the tire circumferential direction, improving drainage performance and snow column shear force, and improving snow and ice performance. As a result, the pneumatic tire 1 can improve dry driving performance while ensuring snow and ice performance.

[0073] Furthermore, in the pneumatic tire 1 of the embodiment, the first center lug grooves 42 and second center lug grooves 43 are arranged in a smaller number in the circumferential direction of the tire than the other lug grooves 41, 44, and 45, at a ratio of 1:2. That is, the first center lug groove 42 and second center lug groove 43 are arranged in a circumferential direction of the tire in a number of one compared to the number of other lug grooves 41, 44, and 45 arranged in the circumferential direction of the tire, two.

[0074] According to the pneumatic tire 1 of the embodiment, the rigidity of the center land zone 21 can be sufficiently ensured, and the effect of improving dry running performance, which is steering stability on dry road surfaces, can be significantly obtained.

[0075] In addition, in the pneumatic tire 1 of the embodiment, the maximum length L1 in the tire width direction of one middle lug groove 41 and the maximum dimension La in the tire width direction of one middle land portion 22A satisfy the relationship 0.50≦L1 / La≦0.90, and the maximum length L2 in the tire width direction of the first center lug groove 42 and the maximum dimension Lb in the tire width direction of the center land portion 21 satisfy the relationship 0.55≦L2 / Lb≦0.95.

[0076] In the pneumatic tire 1 of the embodiment, when L1 / La is less than 0.50, dry driving performance tends to improve but snow performance tends to deteriorate, while when it exceeds 0.90, snow performance tends to improve but dry driving performance tends to deteriorate, so the above range is set. In the pneumatic tire 1 of the embodiment, satisfying the relationship 0.50≦L1 / La≦0.90 is preferable because it significantly improves dry driving performance while maintaining snow and ice performance. In addition, in the pneumatic tire 1 of the embodiment, when L2 / Lb is less than 0.55, dry driving performance similarly improves but snow performance tends to deteriorate, while when it exceeds 0.95, snow performance similarly improves but dry driving performance tends to deteriorate, so the above range is set. In the pneumatic tire 1 of the embodiment, satisfying the relationship 0.55≦L2 / Lb≦0.95 is preferable because it significantly improves dry driving performance while maintaining snow and ice performance.

[0077] In addition, in the pneumatic tire 1 of the embodiment, the maximum length L3 in the tire width direction of the other first middle lug groove 44 and the maximum dimension Lc in the tire width direction of the other middle land portion 22B satisfy the relationship 0.30≦L3 / Lc≦0.70, and the maximum length L4 in the tire width direction of the other second middle lug groove 45 and the maximum dimension Lc in the tire width direction of the other middle land portion 22B satisfy the relationship 0.10≦L4 / Lc≦0.50.

[0078] In the pneumatic tire 1 of the embodiment, when L3 / Lc is less than 0.30, ice performance tends to improve but snow performance tends to deteriorate, and when it exceeds 0.70, snow performance tends to improve but ice performance tends to deteriorate, so the above range is set. In the pneumatic tire 1 of the embodiment, satisfying the relationship 0.30≦L3 / Lc≦0.70 is preferable because it significantly improves snow and ice performance. In addition, in the pneumatic tire 1 of the embodiment, when L4 / Lc is less than 0.10, ice performance tends to improve but snow performance tends to deteriorate, and when it exceeds 0.50, snow performance tends to improve but ice performance tends to deteriorate, so the above range is set. In the pneumatic tire 1 of the embodiment, satisfying the relationship 0.10≦L4 / Lc≦0.50 is preferable because it significantly improves snow and ice performance.

[0079] In addition, in the pneumatic tire 1 of the embodiment, the angle θ1 of one middle lug groove 41 relative to the tire width direction is in the range of 10°≦θ1≦40° in absolute value, the angle θ2 of the first center lug groove 42 relative to the tire width direction is in the range of 10°≦θ2≦40° in absolute value, the angle θ3 of the other first middle lug groove 44 relative to the tire width direction is in the range of 5°≦θ3≦35° in absolute value, and the angle θ4 of the other second middle lug groove 45 relative to the tire width direction is in the range of 1°≦θ4≦20° in absolute value.

[0080] In the pneumatic tire 1 of the embodiment, when the angle θ1 is less than 10°, the snow traction index component in the 0° direction increases, which encourages the collapse of one of the middle land portions 22A during braking, tending to deteriorate ice performance. When the angle θ1 exceeds 40°, the rigidity of one of the middle land portions 22A decreases, tending to deteriorate dry running performance. Therefore, the above range is set. In the pneumatic tire 1 of the embodiment, satisfying the relationship 10°≦θ1≦40° is preferable because it significantly improves dry running performance while maintaining snow and ice performance. Furthermore, in the pneumatic tire 1 of the embodiment, when the angle θ2 is less than 10°, the snow traction index component in the 0° direction increases, which encourages the collapse of the center land portion 21 during braking, tending to deteriorate ice performance. When the angle θ2 exceeds 40°, the rigidity of the center land portion 21 decreases, tending to deteriorate dry running performance. Therefore, the above range is set. In the pneumatic tire 1 of the embodiment, satisfying the relationship 10°≦θ2≦40° is preferable because it significantly improves dry running performance while maintaining snow and ice performance. Furthermore, in the pneumatic tire 1 of the embodiment, when the angle θ3 is less than 5°, the snow traction index component in the 0° direction increases, which encourages the other middle land portion 22B to collapse during braking, tending to deteriorate ice performance. When the angle θ3 exceeds 35°, the rigidity of the other middle land portion 22B decreases, tending to deteriorate dry running performance. Therefore, the above range is set. In the pneumatic tire 1 of the embodiment, satisfying the relationship 5°≦θ3≦35° is preferable because it significantly improves dry running performance while maintaining snow and ice performance. Furthermore, if the angle θ4 is less than 1°, the snow traction index component in the 0° direction increases, which encourages the other middle land portion 22B to collapse during braking, tending to worsen ice performance, while if it exceeds 20°, the rigidity of the other middle land portion 22B decreases, tending to worsen dry running performance. Therefore, the above range is set. In the pneumatic tire 1 of the embodiment, satisfying the relationship 5°≦θ4≦20° is preferable because it significantly improves dry running performance while ensuring snow and ice performance.

[0081] The snow traction index in the 0° direction is an empirical formula proposed by Uniroyal at the SAE (Society of Automotive Engineers) and is defined by the following formula (1): In this formula, ρg is the groove density [1 / mm], and is the ratio [mm] of the groove length of all grooves (all grooves excluding sipes) projected in the circumferential direction of the tire on the tread contact surface to the tread contact area (the product of the tire contact width and tire circumference) [mm 2 ]. ρs is the sipe density [1 / mm], and is calculated as the ratio of the sipe length [mm] of all sipes projected in the circumferential direction of the tire on the tread contact surface to the tread contact area [mm 2 Dg is the average value of the groove depth [mm] of all grooves projected in the circumferential direction of the tire on the tread contact surface.

[0082] STI=-6.8+2202×ρg+672×ρs+7.6×Dg...(1)

[0083] Furthermore, in the pneumatic tire 1 of the embodiment, the groove depth D1 of one middle lug groove 41 and the groove depth D of one shoulder circumferential groove 32A satisfy the relationship 0.6≦D1 / D≦1.0, the groove depth D2 of the first center lug groove 42 and the groove depth D of one center circumferential groove 31A satisfy the relationship 0.6≦D2 / D≦1.0, the groove depth D3 of the other first middle lug groove 44 and the groove depth D of the other center circumferential groove 31B satisfy the relationship 0.6≦D3 / D≦1.0, and the groove depth D4 of the other second middle lug groove 45 and the groove depth D of the other shoulder circumferential groove 32B satisfy the relationship 0.6≦D4 / D≦1.0.

[0084] According to the pneumatic tire 1 of the embodiment, when D1 / D, D2 / D, D3 / D, and D4 / D are less than 0.6, dry running performance improves but snow performance tends to deteriorate, and when they exceed 1.0, snow performance improves but the rigidity of the land portions 22A, 21, and 22B decreases, and dry running performance tends to deteriorate, so they are set within the above ranges.

[0085] In addition, in the pneumatic tire 1 of the embodiment, the groove widths W1 of one middle lug groove 41, the groove width W2 of the first center lug groove 42, the groove width W3 of the other first middle lug groove 44, and the groove width W4 of the other second middle lug groove 45 are in the range of 1.5 [mm] or more and 7.0 [mm] or less. The first center lug groove 42 does not exist on the extension of the tip 41b of one middle lug groove 41, and the other first middle lug groove 44 and the other second middle lug groove 45 do not exist on the extension of the tip 42b of the first center lug groove 42.

[0086] According to the pneumatic tire 1 of the embodiment, when the groove widths W1, W2, W3, and W4 of the lug grooves 41, 42, 43, and 44 are less than 1.5 [mm], the dry running performance improves, but the snow performance tends to deteriorate. When it exceeds 7.0 [mm], the snow performance improves, but the rigidity of the land portions 22A, 21, and 22B decreases and the dry running performance tends to decrease. Therefore, the above range is set. Also, according to the pneumatic tire 1 of the embodiment, the first center lug groove 42 does not exist on the extension of the tip 41b of the middle lug groove 41, and the other first middle lug groove 44 and the other second middle lug groove 45 do not exist on the extension of the tip 42b of the first center lug groove 42. By avoiding the lug grooves 41, 42 and the lug grooves 42, 43 from being too close, the rigidity of the land portions 22A, 21, 22B is ensured and the dry running performance is improved.

[0087] In addition, in the pneumatic tire 1 of the embodiment, the direction with respect to the vehicle width direction when mounted on the vehicle is specified, one is the outside in the vehicle width direction, and the other is the inside in the vehicle width direction.

[0088] According to the pneumatic tire 1 of the embodiment, since the lug grooves 41, 42 have their base ends 41a, 42a on the outside in the vehicle width direction, drainage and snow discharge are directed toward the outer circumferential grooves 32A, 31A during turning, so the performance on ice and snow is improved.

[0089] In addition, in the pneumatic tire 1 of the embodiment, on the tread contact surface 2B, the groove area ratio Go on the outside in the vehicle width direction and the groove area ratio Gi on the inside in the vehicle width direction with the tire equatorial plane CL as the boundary satisfy the relationship Gi < Go and 1.1 ≦ Go / Gi ≦ 1.3.

[0090] Here, the groove area ratio is defined as the percentage of groove area / (groove area + ground contact area). The groove area is the total of the opening areas of the grooves in the tire ground contact surface. The ground contact area is measured between the ground contact ends based on the plane where the pneumatic tire 1 contacts the flat plate when the pneumatic tire 1 with air is mounted on a standard rim, filled with the standard internal pressure, placed vertically against the flat plate in a stationary state, and a load corresponding to the standard load is applied. The groove area does not include the sipe.

[0091] According to the pneumatic tire 1 of the embodiment, by setting the groove area ratio to Gi < Go, the snow performance is improved on the outer side in the vehicle width direction, and the ice performance is improved on the inner side in the vehicle width direction by increasing the ground contact area, making it possible to achieve both ice and snow performance and dry running performance at a high level. And according to the pneumatic tire 1 of the embodiment, when Go / Gi is less than 1.1, the ice performance is improved, but the snow performance tends to deteriorate, and when it exceeds 1.3, the snow performance is improved, but the ice performance tends to deteriorate. Therefore, the above range is set. Also, according to the pneumatic tire 1 of the embodiment, by satisfying the relationship of 1.1 ≦ Go / Gi ≦ 1.3, the effect of ensuring ice and snow performance is significantly obtained, which is preferable.

[0092] In addition, the pneumatic tire 1 of the embodiment is applied to a studless tire that ensures running performance on ice and snow roads, or an all-season tire that ensures running performance in winter, by arranging the sipe 61 on the land portion 20.

[0093] In the pneumatic tire 1 of the embodiment, the sipe 61 is arranged along the extending direction of each of the lug grooves 41, 42, 43, 44, 45 provided in each land portion 20.

[0094] According to the pneumatic tire 1 of the embodiment, since the length of the sipe 61 can be made long, the edge amount is large and the ice and snow performance is improved.

[0095] In addition, the pneumatic tire 1 of the embodiment has a snow traction index in the 0 [°] direction of 100 or more.

[0096] According to this pneumatic tire 1, by making the snow traction index in the 0° direction 100 or more, improved performance on snow can be ensured, and the tire is applicable to a studless tire or an all-season tire.

[0097] In the pneumatic tire 1 of the embodiment, the tread portion 2 has a tread rubber (cap rubber) 2A with a hardness in the range of 40 or more and 70 or less.

[0098] The hardness is rubber hardness indicated by JIS-A hardness in accordance with JIS-K6253 under the condition of 20°C.

[0099] According to this pneumatic tire 1, by setting the hardness of the tread rubber 2A in the range of 40 or more and 70 or less, the rigidity of the land portion 20 can be ensured and performance on snow can be further improved. Note that, in the pneumatic tire 1 of the embodiment, when the hardness of the tread rubber 2A is in the range of 40 or more and 55 or less, it is suitable for a studless tire, and when the hardness of the tread rubber 2A is in the range of 55 or more and 70 or less, it is suitable for an all-season tire.

[0100] [Embodiment 2] A pneumatic tire 101 of embodiment 2 is shown in Figures 5 to 14. The pneumatic tire 101 of embodiment 2 has sipes 62, 63 in the pneumatic tire 1 of embodiment 1, but has the same other configuration. Therefore, the pneumatic tire 101 can be said to be another form of the pneumatic tire 1, and the same parts as those of the pneumatic tire 1 will be assigned the same reference numerals and will not be described again.

[0101] As described above, the land portion 20 has the sipes 61. The pneumatic tire 101 further has sipes 62, 63 in the outer middle land portion 22A and the center land portion 21. Therefore, the pneumatic tire 101 has two or more types of sipes 62, 63 with different widths in the outer middle land portion 22A and the center land portion 21.

[0102] The sipe 62 has the widest width Ws of all the sipes in the outer middle land portion 22A and is also referred to as a wide sipe. The sipe 62 has a width Ws of 0.5 mm to 1.5 mm (see FIG. 6) and a depth Ds of 2.0 mm to 10.0 mm (see FIG. 7). The sipe 62 is disposed adjacent to at least one of the lug grooves 41 adjacent to each other in the tire circumferential direction. "Adjacent" here means immediately adjacent, meaning that no other grooves or sipes exist between them. As shown in FIG. 6, one end 62a of the sipe 62 communicates with the outer shoulder circumferential groove 32A, which communicates with the lug groove 41, and the other end 62b terminates at the outer middle land portion 22A. Alternatively, the sipe 62 may have both ends 62a and 62b terminate at the outer middle land portion 22A (see FIG. 13).

[0103] The sipe 63 has the widest width Ws of all the sipes in the center land portion 21 and is also referred to as a wide sipe. The sipe 63 has a width Ws of 0.5 mm or more and 1.5 mm or less, and a depth Ds of 2.0 mm or more and 10.0 mm or less, as shown in FIG. 7. The sipe 63 is disposed adjacent to at least one of the lug grooves 42 between adjacent lug grooves 42 in the tire circumferential direction. As shown in FIG. 5, one end 63a of the sipe 63 communicates with the outer center circumferential groove 31A to which the lug groove 42 communicates, and the other end 63b terminates at the center land portion 21. Although not shown in the figure, the sipe 63 may have a configuration in which both the one end 63a and the other end 63b terminate at the center land portion 21, similar to the sipe 62.

[0104] The sipes 62, 63 have shapes that include a straight shape, a curved shape, or a zigzag shape on the tread contact surface 2B. The sipes 62, 63 have shapes that include a straight shape or a concave-convex shape in the depth direction or extension direction inside the tread rubber 2A. In this embodiment, the sipes 62, 63 are formed in a straight shape on the tread contact surface 2B and inside the tread rubber 2A.

[0105] Furthermore, as shown in FIG. 14, the pneumatic tire 101 may have narrow grooves 81 in the tread contact surface 2B. The narrow grooves 81 are formed to be narrower and shallower than the circumferential grooves, lug grooves, and sipes, for example, having a width of 0.4 mm or less and a depth of 0.3 mm or less. The narrow grooves 81 are arranged to extend in a direction intersecting the extension directions of the circumferential grooves, lug grooves, and sipes. The narrow grooves 81 may be connected to the circumferential grooves, lug grooves, and sipes, or may terminate at the tread contact surface 2B of the land portion 20 without being connected to the circumferential grooves, lug grooves, and sipes. Although the narrow grooves 81 are shown in a zigzag shape bending partway in FIG. 14, they may be formed to be straight or curved partway. 14 is provided in a form in which one end of the sipe 62 (63) communicates with the circumferential groove and the other end terminates in the land portion 20, but may also be provided in a form in which one end and the other end of the sipe 62 (63) terminate in the land portion 20 as shown in FIG. 13. Although not explicitly shown in the figure, the fine groove 81 may also be provided in the pneumatic tire 1.

[0106] A feature of the pneumatic tire 101 of the embodiment is that the sipes have two or more types of different widths, and include the widest wide sipe 62 (63) that is arranged adjacent to at least one of the lug grooves 41 (42) between adjacent lug grooves 41 (42) in the circumferential direction of the tire.

[0107] In studless tires, the tread rubber 2A is a rubber with a relatively low hardness, so the lug grooves 41 (42) are easily crushed during braking and driving, which reduces the original functions of the lug grooves 41 (42), i.e., shear force in snow and drainage performance, and can result in a decrease in snow performance and wet performance. As shown in Figure 9, if a relatively narrow sipe 61 is placed adjacent to the lug groove 41 (42), the sipe 61 will be crushed first, which can cause the above-mentioned phenomenon.

[0108] In this regard, according to the pneumatic tire 101, by arranging the wide sipes 62(63) adjacent to the lug grooves 41(42), as shown in Fig. 8, the wide sipes 62(63) intentionally become locations that are easily crushed during braking / driving and function to prevent the lug grooves 41(42) from being crushed, thereby improving the shear force in snow and drainage performance of the lug grooves 41(42), and thereby improving performance on snow and wet conditions. In other words, the wide sipes 62(63) are wider than the other sipes 61, and therefore have a large range until they close and crush during braking / driving, and by suppressing deformation around them, they function to prevent the lug grooves 41(42) from being crushed.

[0109] Furthermore, in the pneumatic tire 1 of the embodiment, if all the sipes in the land portion 20 were wide sipes 62 (63), the ground contact area would be reduced, the adhesive friction force would decrease, and performance on ice would be degraded, and the rigidity of the land portion 20 would also be reduced, degrading wear resistance. For this reason, the pneumatic tire 101 of the embodiment has two or more types of sipes with different widths, thereby ensuring performance on ice.

[0110] As a result, the pneumatic tire 101 can improve its performance on snow and wet surfaces without impairing its performance on ice.

[0111] In the embodiment of the pneumatic tire 101, the wide sipes 62 (63) are arranged adjacent to only one side of the lug groove 41 (42) in the tire circumferential direction, but the wide sipes 62 (63) may also be arranged adjacent to the other side of the lug groove 41 (42) in the tire circumferential direction, and the same effect can be obtained.

[0112] In the pneumatic tire 101 of the embodiment, the width Ws of the wide sipe 62 (63) and the width Wsa of the other sipes 61 satisfy the relationship 1.1≦Ws / Wsa≦4.0.

[0113] In this pneumatic tire 101, if Ws / Wsa is less than 1.1, it becomes difficult to obtain the effect of preventing the lug grooves 41 (42) from collapsing. Also, in this pneumatic tire 101, if Ws / Wsa exceeds 4.0, the rigidity of the land portions 20 decreases, making it difficult to obtain performance on ice. Therefore, by setting Ws / Wsa in the above range, this pneumatic tire 101 can significantly obtain the effect of improving performance on snow and wet ground without impairing performance on ice.

[0114] Furthermore, in the pneumatic tire 101 of the embodiment, in the land portion 22A, the distance Bs between adjacent lug grooves 41 and wide sipes 62 and the length B in the tire circumferential direction of the land portion 20 between each lug groove 41 adjacent in the tire circumferential direction satisfy the relationship 0.1≦Bs / B≦0.5. Furthermore, in the pneumatic tire 101 of the embodiment, in the land portion 21, the distance Bs between adjacent lug grooves 42 and wide sipe 62 and the length B in the tire circumferential direction of the land portion 20 between each lug groove 42, 43 adjacent in the tire circumferential direction satisfy the relationship 0.1≦Bs / B≦0.5.

[0115] The distance Bs between the lug groove 41 (42) and the wide sipe 62 (63) is the distance between the center lines of the lug groove 41 (42) and the wide sipe 62 (63). The center line is a straight line connecting the centers of both ends of the lug groove 41 (42) and the wide sipe 62 (63).

[0116] In this pneumatic tire 101, if Bs / B is less than 0.1, the rigidity of the land portions 20 decreases, tending to result in poor on-ice performance. Also, in this pneumatic tire 101, if Bs / B exceeds 0.5, the rigidity of the land portions 20 increases, tending to reduce the ability to crush the wide sipes 62 (63), making it difficult to obtain the effect of improving on-snow performance and wet performance. Therefore, by setting Bs / B in the above range, this pneumatic tire 101 can significantly obtain the effect of improving on-snow performance and wet performance without impairing on-ice performance.

[0117] In order to achieve the above-described effects, it is preferable that the distance Bs between the lug grooves 41 (42) and the wide sipes 62 (63) be in the range of 3.0 mm to 10.0 mm. In the pneumatic tire 101 of the embodiment, if the distance Bs is less than 3.0 mm, the tread rubber 2A therebetween becomes thin and tends to chip easily. In addition, in the pneumatic tire 101 of the embodiment, if the distance Bs exceeds 10.0 mm, the tread rubber 2A therebetween becomes thick, which tends to reduce the function of the wide sipes 62 (63) in preventing the lug grooves 41 (42) from being crushed, making it difficult to achieve the effect of improving snow performance and wet performance. Therefore, by setting the distance Bs between the lug grooves 41 (42) and the wide sipes 62 (63) in the above-described range, the pneumatic tire 101 significantly achieves the effect of improving snow performance and wet performance and can also prevent chipping of the land portion 20.

[0118] In addition, in the pneumatic tire 101 of the embodiment, the distance Bs between adjacent lug grooves 41 (42) and wide sipes 62 (63) and the groove width W1 (W2) of the lug groove 41 (42) satisfy the relationship 1.0≦Bs / W1≦3.0 (1.0≦Bs / W2≦3.0).

[0119] In this pneumatic tire 101, if Bs / W1 (Bs / W2) is less than 1.0, the rigidity of the land portion 20 decreases, and performance on ice tends to deteriorate. Also, in this pneumatic tire 101, if Bs / W1 (Bs / W2) is more than 3.0, the rigidity of the land portion 20 increases, and the ability to crush the sipes 62 (63) tends to decrease, making it difficult to achieve the effect of improving performance on snow and wet surfaces. Therefore, by setting Bs / W1 (Bs / W2) in the above range, this pneumatic tire 101 can significantly improve performance on snow and wet surfaces without impairing performance on ice.

[0120] In addition, in the pneumatic tire 101 of the embodiment, the groove depth D1 (D2) of the adjacent lug grooves 41 (42) and the depth Ds of the wide sipe 62 (63) satisfy the relationship 0.2≦Ds / D1≦1.0 (0.2≦Ds / D2≦1.0).

[0121] In this pneumatic tire 101, if Ds / D1 (Ds / D2) is less than 0.2, the rigidity of the land portions 20 increases, which tends to reduce the ability to crush the wide sipes 62 (63), making it difficult to achieve the effect of improving snow performance and wet performance. Also, in this pneumatic tire 101, if Ds / D1 (Ds / D2) exceeds 1.0, the rigidity of the land portions 20 decreases, which tends to reduce performance on ice. Therefore, by setting Ds / D1 (Ds / D2) in the above range, the pneumatic tire 101 can significantly improve snow performance and wet performance without compromising performance on ice.

[0122] In the pneumatic tire 101 of the embodiment, the length Lr of the lug groove 41 (42) and the length Ls of the wide sipe 62 (63) adjacent to each other satisfy the relationship 0.4≦Ls / Lr≦0.9.

[0123] In this pneumatic tire 101, if Ls / Lr is less than 0.4, the rigidity of the land portion 20 increases, which tends to reduce the ability to crush the wide sipes 62 (63), making it difficult to achieve the effect of improving snow performance and wet performance. Also, in this pneumatic tire 101, if Ls / Lr exceeds 0.9, the rigidity of the land portion 20 decreases, which tends to reduce performance on ice. Therefore, by setting Ls / Lr in the above range, this pneumatic tire 101 can significantly achieve the effect of improving snow performance and wet performance without impairing performance on ice.

[0124] In the pneumatic tire 101 of the embodiment, the wide sipes 62 (63) are arranged to extend along the extending direction of the lug grooves 41 (42) adjacent to each other.

[0125] The adjacent lug grooves 41 (42) and wide sipes 62 (63) are inclined in the same direction relative to the tire width direction in their extension directions, and the difference in inclination angle between the adjacent lug grooves 41 (42) and wide sipes 62 (63) extending in the same direction (θs-θr: absolute value) is within a range of 10°. The adjacent lug grooves 41 (42) and wide sipes 62 (63) are preferably parallel to each other. This pneumatic tire 101 improves the crushing effect of the sipes 62 (63), making it easier to obtain the effect of improving snow performance and wet performance. Note that it is preferable that all of the lug grooves 41 (42) and wide sipes 62 (63) arranged in one land portion 20 are inclined in the same direction relative to the tire width direction.

[0126] In the pneumatic tire 101 of the embodiment, the tread portion 2 has a groove area ratio of the tread pattern in the range of 20% to 40%.

[0127] According to this pneumatic tire 101, by setting the groove area ratio of the tread pattern in the range of 20% to 40%, it is possible to obtain a significant effect of improving the performance on snow and wet conditions.

[0128] In the pneumatic tire 101 of the embodiment, the wide sipe 62 (63) has a depth Ds that is constant or gradually changes in the length direction, or has an upper bottom 62e (63e) on the bottom 62d (63d).

[0129] The depth Ds being constant in the length direction means that the depth Ds from the opening 62c (63c) to the bottom 62d (63d) does not change in the length direction (between one end 62a (63a) and the other end 62b (63b)) as shown in Fig. 10. Furthermore, the depth Ds gradually changing in the length direction means that the bottom 62d (63d) is inclined in the length direction (between one end 62a (63a) and the other end 62b (63b)) with respect to the length direction, so that the depth Ds of the wide sipe 62 (63) gradually changes, as shown in Fig. 11. Furthermore, the phrase "having an upper bottom portion 62e (63e) at the bottom portion 62d (63d) of the wide sipe 62 (63)" means that the bottom portion 62d (63d) has a portion where the depth Ds suddenly becomes shallower as the bottom portion 62d (63d) protrudes outward in the tire radial direction midway in the length direction (between one end 62a (63a) and the other end 62b (63b)), as shown in Fig. 12. The depth Ds of the upper bottom portion 62e (63e) may be constant or gradually change in the length direction.

[0130] According to the pneumatic tire 101, various bottom shapes of the wide sipes 62 (63) do not hinder the above-mentioned effects from being achieved. However, in order to significantly achieve the above-mentioned effects, it is preferable that the depth Ds of the pneumatic tire 101 is constant in the length direction, since this has a significant effect on the lug grooves 41.

[0131] In the present embodiment, as described above, a pneumatic tire 1 has been described as an example of a tire. The pneumatic tire 1 can be filled with air, an inert gas such as nitrogen, or other gases. However, the tread pattern configuration of the pneumatic tire 1 described in the present embodiment can be applied to other tires as desired within the scope of what is obvious to those skilled in the art. Examples of other tires include airless tires and solid tires. [Example]

[0132] 15 to 21 are tables showing the results of performance tests of pneumatic tires according to the embodiment. Performance evaluation tests conducted on a conventional pneumatic tire and an example pneumatic tire according to the embodiment will be described below. The performance evaluation tests were conducted on ice performance, snow performance, dry driving performance, uneven wear resistance, and wet performance.

[0133] The performance evaluation test was carried out by mounting a pneumatic tire 1 having a tire nominal size of 195 / 65R15 91Q as specified by JATMA on a JATMA standard rim wheel having a rim size of 15 x 6.5J, mounting the test tire on a front-wheel drive evaluation vehicle with an engine displacement of 1800cc, adjusting the air pressure to 240 kPa for the front wheels and 240 kPa for the rear wheels, and running the evaluation vehicle.

[0134] To evaluate ice performance, a test vehicle fitted with the test tires is subjected to a braking test on an icy test course, and the braking distance is measured. Based on the results of these tests, the reciprocal of the tire's braking distance is used to evaluate the tire's performance, with the conventional tire being used as the benchmark (100). The higher the evaluation value, the better.

[0135] The evaluation test for snow performance involves braking tests on a test vehicle fitted with test tires on a snowy test course, measuring the braking distance. Based on the results of these tests, the reciprocal of the tire's braking distance is used to evaluate the tire's performance, with the conventional tire being used as the standard (100). The higher the evaluation value, the better.

[0136] For the dry driving performance evaluation test, an evaluation vehicle fitted with the test tires was driven on a dry asphalt test course, and a professional test driver evaluated the feel of lane change performance, cornering performance, etc. This evaluation was based on an index rating, with the conventional example being set as the standard (100), and the higher the number, the better.

[0137] The wear resistance evaluation test involves measuring the amount of wear after a test vehicle fitted with a test tire has driven 10,000 km on a dry asphalt test course. Based on the results of this measurement, the reciprocal of the tire's wear is used to evaluate the tire's performance, with the conventional tire being used as the standard (100). The higher the evaluation value, the better.

[0138] The wet performance evaluation test involves a braking test on a test vehicle fitted with a test tire on a wet road test course with 1mm of water depth, and the braking distance is measured. Based on the measurement results, the reciprocal of the tire is used to evaluate the tire's performance on an index basis, with the conventional tire being used as the standard (100). The higher the evaluation value, the better.

[0139] The conventional pneumatic tire has four straight circumferential grooves: an outer middle lug groove, a first center lug groove, an inner first middle lug groove, and an inner second middle lug groove. None of the lug grooves penetrates a land portion, and all except the inner second middle lug groove are inclined in the same direction relative to the tire width direction. The conventional pneumatic tire also does not have a second center lug groove, and the groove walls of the outer shoulder circumferential groove are not inclined.

[0140] As shown in Figure 2, the pneumatic tire of the example has four straight circumferential grooves: first center lug groove, second center lug groove, outer middle lug groove, inner first middle lug groove, and inner second middle lug groove. None of the lug grooves penetrates the land portion, and the outer middle lug groove, first center lug groove, inner first middle lug groove, and inner second middle lug groove are alternately inclined in opposite directions relative to the tire width direction. Furthermore, the pneumatic tire of the example has fewer first center lug grooves and second center lug grooves in the tire circumferential direction than the other lug grooves, and the groove walls of the outer shoulder circumferential grooves are inclined.

[0141] As shown in the test results, the pneumatic tire of this example has improved ice performance, snow performance, dry running performance, uneven wear resistance, and wet performance compared to the conventional tire.

[0142] The present disclosure includes the following inventions. [Invention 1] one center circumferential groove and the other center circumferential groove are formed linearly along the tire circumferential direction and are adjacent to each other across the tire equatorial plane; one shoulder circumferential groove and the other shoulder circumferential groove are formed linearly along the tire circumferential direction and are defined on the tire width direction outer sides of each of the center circumferential grooves; a center land portion defined between the center circumferential grooves and continuing in the tire circumferential direction; one middle land portion and the other middle land portion that are respectively defined between the shoulder circumferential groove and the center circumferential groove and are continuous in the tire circumferential direction; one shoulder land portion and another shoulder land portion defined on the outer side in the tire width direction of each of the shoulder circumferential grooves; a plurality of first center lug grooves arranged side by side in the tire circumferential direction in the center land portion, the first center lug grooves having base ends extending along the tire width direction in the center land portion and communicating with one of the center circumferential grooves and having tip ends terminating inside the center land portion; a plurality of second center lug grooves arranged side by side in the tire circumferential direction in the center land portion, the base ends of the second center lug grooves extending along the tire width direction in the center land portion communicating with the other center circumferential groove and the tip ends terminating inside the center land portion; one middle lug groove, which is arranged in a row in the tire circumferential direction in the one middle land portion, and whose base ends extending along the tire width direction communicate with the one shoulder circumferential groove and whose tip ends terminate inside the one middle land portion; a plurality of other first middle lug grooves arranged side by side in the tire circumferential direction in the other middle land portion, the base ends of the other first middle lug grooves extending along the tire width direction being connected to the other center circumferential groove and the tip ends being terminated inside the other middle land portion; a second middle lug groove, the second middle lug groove being arranged in a row in the tire circumferential direction in the other middle land portion, the second middle lug groove having a base end extending along the tire width direction in the other middle land portion and communicating with the other shoulder circumferential groove and a tip end terminating inside the other middle land portion; a center connecting sipe extending from a tip of the first center lug groove in the center land portion and communicating with the other center circumferential groove; a middle connecting sipe extending from a tip end of the one middle lug groove in the one middle land portion and communicating with the one center circumferential groove; in the tread portion, the one middle lug groove, the first center lug groove, the other first middle lug groove, and the other second middle lug groove are alternately provided in opposite inclination directions with respect to the tire width direction, the first center lug grooves and the second center lug grooves are arranged in a smaller number in the tire circumferential direction than the other lug grooves, the one shoulder circumferential groove is formed such that groove walls between the plurality of one middle lug grooves are inclined in the same direction with respect to the tire circumferential direction; tire. [Invention 2] a maximum length L1 of the one middle lug groove in the tire width direction and a maximum dimension La of the one middle land portion in the tire width direction satisfy a relationship of 0.50≦L1 / La≦0.90; The maximum length L2 of the first center lug groove in the tire width direction and the maximum dimension Lb of the center land portion in the tire width direction satisfy the relationship 0.55≦L2 / Lb≦0.95. A tire according to claim 1. [Invention 3] a maximum length L3 of the other first middle lug groove in the tire width direction and a maximum dimension Lc of the other middle land portion in the tire width direction satisfy the relationship 0.30≦L3 / Lc≦0.70; a maximum length L4 of the other second middle lug groove in the tire width direction and a maximum dimension Lc of the other middle land portion in the tire width direction satisfy the relationship 0.10≦L4 / Lc≦0.50; The tire according to claim 1 or 2. [Invention 4] The angle θ1 of the one middle lug groove with respect to the tire width direction is in the range of 10 [°] ≦ θ1 ≦ 40 [°] in absolute value, The angle θ2 of the first center lug groove with respect to the tire width direction is in the range of 10 [°] ≦ θ2 ≦ 40 [°] in absolute value, the angle θ3 of the other first middle lug groove with respect to the tire width direction is in the range of 5°≦θ3≦35° in absolute value, The angle θ4 of the other second middle lug groove with respect to the tire width direction is in the range of 1[°]≦θ4≦20[°] in absolute value. The tire according to any one of Inventions 1 to 3. [Invention 5] The groove depth D1 of the one middle lug groove and the groove depth D of the one shoulder circumferential groove satisfy the relationship of 0.6≦D1 / D≦1.0. The groove depth D2 of the first center lug groove and the groove depth D of the one center circumferential groove satisfy the relationship of 0.6≦D2 / D≦1.0. The groove depth D3 of the other first middle lug groove and the groove depth D of the other center circumferential groove satisfy the relationship of 0.6≦D3 / D≦1.0. The groove depth D4 of the other second middle lug groove and the groove depth D of the other shoulder circumferential groove satisfy the relationship of 0.6≦D4 / D≦1.0. The tire according to any one of Inventions 1 to 4. [Invention 6] The groove widths W1 of the one middle lug groove, W2 of the first center lug groove, W3 of the other first middle lug groove, and W4 of the other second middle lug groove are in the range of 1.5[mm] or more and 7.0[mm] or less. The first center lug groove does not exist on the extension of the tip of the one middle lug groove. The other first middle lug groove and the other second middle lug groove do not exist on the extension of the tip of the first center lug groove. The tire according to any one of Inventions 1 to 5. [Invention 7] The orientation with respect to the vehicle width direction when mounted on a vehicle is specified. The one is on the outer side in the vehicle width direction, and the other is on the inner side in the vehicle width direction. The tire according to any one of Inventions 1 to 6. [Invention 8] On the tread contact surface, the groove area ratio Go on the outer side in the vehicle width direction with the tire equatorial plane as the boundary and the groove area ratio Gi on the inner side in the vehicle width direction satisfy Gi < Go and the relationship of 1.1≦Go / Gi≦1.3. The tire according to Invention 7. [Invention 9] Each land portion has a plurality of sipes extending along the tire width direction and arranged side by side in the tire circumferential direction, In the center land portion, the sipes have two or more types of widths different from each other, and include a wide sipe having the widest width and disposed adjacent to at least one of the first center lug grooves between the first center lug grooves, In the one middle land portion, the sipes have two or more types of different widths, and include a wide sipe having the widest width that is arranged adjacent to at least one of the one middle lug grooves between the one middle lug grooves. A tire according to any one of inventions 1 to 8. [Invention 10] The width Ws of the wide sipe and the width Wsa of the other sipes satisfy the relationship 1.1≦Ws / Wsa≦4.0. A tire according to invention 9. [Invention 11] a distance Bs between the lug groove and the wide sipe adjacent to each other and a length B in the tire circumferential direction of the land portion between the lug grooves adjacent in the tire circumferential direction with the wide sipe disposed therebetween satisfy the relationship of 0.1≦Bs / B≦0.5; A tire according to invention 9 or 10. [Invention 12] A groove depth D1 of the lug groove between which the wide sipe is disposed and a depth Ds of the wide sipe adjacent to the lug groove satisfy the relationship of 0.2≦Ds / D1≦1.0. 12. A tire according to any one of claims 9 to 11. [Invention 13] The length Lr of the lug groove between which the wide sipe is disposed and the length Ls of the wide sipe adjacent to the lug groove satisfy the relationship of 0.4≦Ls / Lr≦0.9. A tire according to any one of inventions 9 to 12. [Invention 14] The wide sipes are arranged to extend along the extension direction of the adjacent lug grooves. A tire according to any one of inventions 9 to 13. [Invention 15] The snow traction index in the 0° direction is 100 or higher. 15. A tire according to any one of claims 1 to 14. [Invention 16] The tread portion has a tread rubber hardness in the range of 40 or more and 70 or less. 16. A tire according to any one of claims 1 to 15. [Explanation of symbols]

[0143] 1,101 pneumatic tires (tires) 2A Tread rubber 2B tread contact surface 2 Tread section 20 Land 21 Center Land Division 22A Outer middle land area (one middle land area) 22B Inner middle land part (other middle land part) 23A Outer shoulder land area (one shoulder land area) 23B Inner shoulder land portion (other shoulder land portion) 31A Outer center circumferential groove (one of the center circumferential grooves) 31B Inner center circumferential groove (other center circumferential groove) 32A Outer shoulder circumferential groove (one shoulder circumferential groove) 32Aa Groove wall 32B Inner shoulder circumferential groove (other shoulder circumferential groove) 41 Outer middle lug groove (one middle lug groove) 41a proximal end 41b tip 42 First center lug groove 42a proximal end 42b tip 43 Second center lug groove 43a proximal end 43b tip 44 Inner first middle lug groove (other first middle lug groove) 44a proximal end 44b tip 45 Inner second middle lug groove (other second middle lug groove) 45a proximal end 45b tip 51 Middle connecting sipes 52 Center connecting sipe 61 Sipe 62 Wide sipes 63 Wide sipes

Claims

1. one center circumferential groove and the other center circumferential groove are formed linearly along the tire circumferential direction and are adjacent to each other across the tire equatorial plane; one shoulder circumferential groove and the other shoulder circumferential groove are formed linearly along the tire circumferential direction and are defined on the tire width direction outer sides of each of the center circumferential grooves; a center land portion defined between the center circumferential grooves and continuing in the tire circumferential direction; one middle land portion and another middle land portion that are respectively defined between the shoulder circumferential groove and the center circumferential groove and are continuous in the tire circumferential direction; one shoulder land portion and another shoulder land portion defined on the outer side in the tire width direction of each of the shoulder circumferential grooves; a plurality of first center lug grooves arranged side by side in the tire circumferential direction in the center land portion, the base ends of the first center lug grooves extending along the tire width direction in the center land portion communicating with one of the center circumferential grooves and the tip ends of the first center lug grooves terminating inside the center land portion; a plurality of second center lug grooves arranged side by side in the tire circumferential direction in the center land portion, the base ends of the second center lug grooves extending along the tire width direction in the center land portion communicating with the other center circumferential groove and the tip ends terminating inside the center land portion; one middle lug groove, which is arranged in a row in the tire circumferential direction in the one middle land portion, and whose base ends extending along the tire width direction communicate with the one shoulder circumferential groove and whose tip ends terminate inside the one middle land portion; a plurality of other first middle lug grooves arranged side by side in the tire circumferential direction in the other middle land portion, the base ends of the other first middle lug grooves extending along the tire width direction being connected to the other center circumferential groove and the tip ends being terminated inside the other middle land portion; a second middle lug groove, the second middle lug groove being arranged in a row in the tire circumferential direction in the other middle land portion, the second middle lug groove having a base end extending along the tire width direction in the other middle land portion and communicating with the other shoulder circumferential groove and a tip end terminating inside the other middle land portion; a center connecting sipe extending from a tip of the first center lug groove in the center land portion and communicating with the other center circumferential groove; a middle connecting sipe extending from a tip end of the one middle lug groove in the one middle land portion and communicating with the one center circumferential groove; in the tread portion, the one middle lug groove, the first center lug groove, the other first middle lug groove, and the other second middle lug groove are alternately provided in opposite inclination directions with respect to the tire width direction, the first center lug grooves and the second center lug grooves are arranged in a smaller number in the tire circumferential direction than the other lug grooves, the one shoulder circumferential groove is formed such that groove walls between the plurality of one middle lug grooves are inclined in the same direction with respect to the tire circumferential direction; tire.

2. a maximum length L1 of the one middle lug groove in the tire width direction and a maximum dimension La of the one middle land portion in the tire width direction satisfy the relationship 0.50≦L1 / La≦0.90, a maximum length L2 of the first center lug groove in the tire width direction and a maximum dimension Lb of the center land portion in the tire width direction satisfy the relationship 0.55≦L2 / Lb≦0.95; 2. The tire of claim 1.

3. a maximum length L3 of the other first middle lug groove in the tire width direction and a maximum dimension Lc of the other middle land portion in the tire width direction satisfy a relationship of 0.30≦L3 / Lc≦0.70; a maximum length L4 of the other second middle lug groove in the tire width direction and a maximum dimension Lc of the other middle land portion in the tire width direction satisfy the relationship 0.10≦L4 / Lc≦0.50; 2. The tire of claim 1.

4. the angle θ1 of the one middle lug groove with respect to the tire width direction is in the range of 10°≦θ1≦40° in absolute value, The angle θ2 of the first center lug groove with respect to the tire width direction is in the range of 10°≦θ2≦40° in absolute value, the angle θ3 of the other first middle lug groove with respect to the tire width direction is in the range of 5°≦θ3≦35° in absolute value, the angle θ4 of the other second middle lug groove with respect to the tire width direction is in the range of 1°≦θ4≦20° in absolute value; 2. The tire of claim 1.

5. a groove depth D1 of the one middle lug groove and a groove depth D of the one shoulder circumferential groove satisfy a relationship of 0.6≦D1 / D≦1.0, a groove depth D2 of the first center lug groove and a groove depth D of the one center circumferential groove satisfy the relationship 0.6≦D2 / D≦1.0, a groove depth D3 of the other first middle lug groove and a groove depth D of the other center circumferential groove satisfy a relationship of 0.6≦D3 / D≦1.0, a groove depth D4 of the other second middle lug groove and a groove depth D of the other shoulder circumferential groove satisfy a relationship of 0.6≦D4 / D≦1.0; 2. The tire of claim 1.

6. a groove width W1 of the one middle lug groove, a groove width W2 of the first center lug groove, a groove width W3 of the other first middle lug groove, and a groove width W4 of the other second middle lug groove are in the range of 1.5 mm or more and 7.0 mm or less, The first center lug groove is not located on an extension of a tip end of one of the middle lug grooves, the other first middle lug groove and the other second middle lug groove are not present on an extension of a tip end of the first center lug groove; 2. The tire of claim 1.

7. The direction relative to the vehicle width when installed is specified. The one is on the outer side in the vehicle width direction, and the other is on the inner side in the vehicle width direction.

2. The tire of claim 1.

8. In the tread contact surface, a groove area ratio Go on the outer side in the vehicle width direction and a groove area ratio Gi on the inner side in the vehicle width direction with respect to the tire equatorial plane satisfy the relationship Gi<Go and 1.1≦Go / Gi≦1.

3.

8. The tire of claim 7.

9. Each land portion has a plurality of sipes extending along the tire width direction and arranged side by side in the tire circumferential direction, In the center land portion, the sipes have two or more types of widths different from each other, and include a wide sipe having the widest width and disposed adjacent to at least one of the first center lug grooves between the first center lug grooves, In the one middle land portion, the sipes have two or more types of widths different from each other, and include a wide sipe having the widest width that is arranged adjacent to at least one of the one middle lug grooves between the one middle lug grooves.

2. The tire of claim 1.

10. a width Ws of the wide sipe and a width Wsa of the other sipes satisfy the relationship 1.1≦Ws / Wsa≦4.0; 10. The tire of claim 9.

11. a distance Bs between the lug groove and the wide sipe adjacent to each other and a length B in the tire circumferential direction of the land portion between the lug grooves adjacent in the tire circumferential direction with the wide sipe disposed therebetween satisfy a relationship of 0.1≦Bs / B≦0.5; 10. The tire of claim 9.

12. A groove depth D1 of the lug groove between which the wide sipe is disposed and a depth Ds of the wide sipe adjacent to the lug groove satisfy a relationship of 0.2≦Ds / D1≦1.

0.

10. The tire of claim 9.

13. The length Lr of the lug groove between which the wide sipe is disposed and the length Ls of the wide sipe adjacent to the lug groove satisfy the relationship of 0.4≦Ls / Lr≦0.

9.

10. The tire of claim 9.

14. The wide sipes are arranged to extend along the extension direction of the adjacent lug grooves.

10. The tire of claim 9.

15. The snow traction index in the 0° direction is 100 or more.

2. The tire of claim 1.

16. The tread portion has a tread rubber hardness in the range of 40 or more and 70 or less.

2. The tire of claim 1.

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