Tire

Abstract

The present invention improves wear resistance while ensuring ice / snow performance and wet performance. The present invention comprises center circumferential main grooves 31A, 31B, shoulder circumferential main grooves 32A, 32B, a center land portion 21, middle land portions 22A, 22B, shoulder land portions 23A, 23B, center lug grooves 42, outer middle lug grooves 41, outer shoulder lug grooves 45, inner first middle lug grooves 43, inner second middle lug grooves 44, inner shoulder lug grooves 46, middle straight sipes 51, and center straight sipes 52. The outer middle lug grooves, the center lug grooves, the inner first middle lug grooves, and the inner second middle lug grooves are provided such that the inclination directions thereof with respect to the tire width direction are sequentially opposite. The shoulder circumferential main grooves are provided such that groove walls 32Aa between the outer middle lug grooves are inclined in the same direction with respect to the tire circumferential direction. The center circumferential main grooves are provided such that groove walls 31Aa between the center lug grooves are inclined in the same direction with respect to the tire circumferential direction.

Description

tire

[0001] The present invention relates to tires.

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

[0003] Japanese Patent Application Laid-Open No. 2009-018605

[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 and wet surfaces. In addition, improved wear resistance is also required for studless tires in recent years.

[0005] An object of the present invention is to provide a tire that can improve wear resistance while ensuring snow and ice performance and wet performance by optimizing the pattern configuration.

[0006] In order to achieve the above object, a tire according to one aspect of the present invention includes one center circumferential main groove and the other center circumferential main groove formed linearly along the tire circumferential direction and adjacent to each other on either side of the tire equatorial plane, one shoulder circumferential main groove and the other shoulder circumferential main groove formed linearly along the tire circumferential direction and adjacent to each other on the tire width direction outer side of each center circumferential main groove, a center land portion partitioned between the center circumferential main grooves and continuing in the tire circumferential direction, and a tire land portion partitioned between the shoulder circumferential main groove and the center circumferential main groove, one shoulder land portion and the other shoulder land portion that are continuous in the tire circumferential direction; one shoulder land portion and the other shoulder land portion that are defined on the tire width direction outer side of each shoulder circumferential main groove; center lug grooves that are arranged side by side in the tire width direction in the center land portion, with base ends that extend along the tire width direction in the center land portion communicating with one of the center circumferential main grooves and with tips that terminate inside the center land portion; and one middle land portion that has a base end that extends along the tire width direction in the one middle land portion communicating with one of the shoulder circumferential main grooves and with tips that terminate inside the one middle land portion. one shoulder lug groove in the one shoulder land portion, a base end of which communicates with the one shoulder circumferential main groove, extends along the tire width direction, passes through the ground contact edge, and is arranged in a row in the tire width direction; another first middle lug groove in the other middle land portion, a base end of which communicates with the other center circumferential main groove, extending along the tire width direction, and a tip end of which terminates inside the other middle land portion, and is arranged in a row in the tire width direction; a second middle lug groove arranged in a row in the tire width direction, with a base end extending along the tire width direction communicating with the other shoulder circumferential main groove and a tip end terminating inside the other middle land portion; a second shoulder lug groove arranged in a row in the tire width direction, with a base end communicating with the other shoulder circumferential main groove in the other shoulder land portion, extending along the tire width direction and passing through the ground contact edge; and a straight middle straight sipe extending from a tip end of one middle lug groove in the one middle land portion and communicating with the one center circumferential main groove.and a linear center straight sipe extending from a tip of the center lug groove in the center land portion and communicating with the other center circumferential main groove, wherein the one middle lug groove, the center lug groove, the other first middle lug groove, and the other second middle lug groove are arranged so that their inclination directions with respect to the tire width direction are alternately opposite, the one shoulder circumferential main groove is formed so that groove walls between the plurality of one middle lug grooves are inclined in the same direction with respect to the tire circumferential direction, and the one center circumferential main groove is formed so that groove walls between the plurality of center lug grooves are inclined in the same direction with respect to the tire circumferential direction.

[0007] According to the present invention, it is possible to improve wear resistance while ensuring performance on snow and ice and wet conditions.

[0008] FIG. 1 is a meridian cross-sectional view of a pneumatic tire according to an embodiment. FIG. 2 is a plan view of a tread portion of a pneumatic tire according to an embodiment. FIG. 3 is a cross-sectional view of each circumferential main groove of a pneumatic tire according to an embodiment. FIG. 4 is a cross-sectional view of each middle lug groove and center lug groove of a pneumatic tire according to an embodiment. FIG. 5 is a table showing the results of a performance test of a pneumatic tire according to an embodiment. FIG. 6 is a table showing the results of a performance test of a pneumatic tire according to an embodiment. FIG. 7 is a table showing the results of a performance test of a pneumatic tire according to an embodiment.

[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 a direction perpendicular to the tire rotation axis (not shown), which is the rotation axis of the pneumatic tire 1 of this embodiment. The tire radially inner side refers to the side toward the tire rotation axis in the tire radial direction, and the tire radially outer side refers to the side away from the tire rotation axis in the tire radial direction. The tire circumferential direction refers to the direction around the tire rotation axis as the central axis. The tire width direction refers to a direction parallel to the tire rotation axis. The tire widthwise inner side refers to the side toward the tire equatorial plane (tire equator line) CL in the tire width direction, and the tire widthwise outer side refers to the side away from the tire equatorial plane CL in the tire width direction. The tire equatorial plane CL is a plane that is perpendicular to the tire rotation axis and passes through the center of the tire width of the pneumatic tire 1. The tire equatorial plane CL coincides in position in the tire width direction with the tire widthwise centerline, which is the center position of the pneumatic tire 1 in the tire width direction. The tire 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. Further, a cross section in the tire meridian direction (meridian cross section) refers to a cross section of the tire cut along 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 of the tread portion 2 in the tire width direction and radially inward of the shoulder portions 2C. The sidewall portions 8 are disposed in two locations on both sides of the pneumatic tire 1 in the tire width direction, and form the outermost exposed portions of the pneumatic tire 1 in the tire width direction.

[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. 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.

[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 coating 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 coated 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 (e.g., 20 degrees or more and 55 degrees or less). 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 so as to cross 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 relative to the tire circumferential direction, within a predetermined range (e.g., 0 degrees or more and 10 degrees or less). 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, 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 constituting 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 according to 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. Also, "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. Also, "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 in 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 a configuration in which 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] 1 and 2, the pneumatic tire 1 of the embodiment mainly includes, as a tread pattern, a center circumferential main groove 31 and shoulder circumferential main grooves 32. Each of the circumferential main grooves 31, 32 is defined as a groove that is required to display a wear indicator as defined by JATMA.

[0026] The center circumferential main grooves 31 extend along the tire circumferential direction and have an annular structure that is continuously provided around the entire tire circumference. Two center circumferential main grooves 31 are provided in parallel in the tire width direction with the tire equatorial plane CL sandwiched between them. The center circumferential main grooves 31 are formed in a straight line along the tire circumferential direction without any bends. As shown in FIG. 3 , the center circumferential main grooves 31 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.

[0027] The shoulder circumferential main grooves 32 extend circumferentially along the tire and have a continuous annular structure around the entire tire circumference. The shoulder circumferential main grooves 32 are arranged in parallel in the tire width direction on the tire widthwise outer side of the two center circumferential main grooves 31, with the tire equatorial plane CL sandwiched between them. The shoulder circumferential main grooves 32 are formed linearly along the tire circumferential direction without any bends. As shown in FIG. 3 , the shoulder circumferential main 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 main grooves 31 and two shoulder circumferential main 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 in a single rib-like row along the tire circumferential direction between the two center circumferential main grooves 31, including the tire equatorial plane CL. The middle land portion 22 is defined between one center circumferential main groove 31 and one shoulder circumferential main groove 32, and is formed in a rib-like row along the tire circumferential direction on both outer sides of the center land portion 21 in the tire width direction, for a total of two rows. The shoulder land portions 23 are defined on the tire widthwise outer side of each shoulder circumferential main groove 32, and are formed in a 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 ends 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 orientation of the pneumatic tire 1 of the embodiment relative to the vehicle width direction (tire width direction) when mounted on a vehicle, i.e., the inside and outside in the vehicle width direction, are defined. Specifically, the pneumatic tire 1 includes a mounting direction indicator (not shown) that indicates the tire mounting direction relative to the vehicle. The mounting direction indicator is configured, for example, by a mark or a concavo-convex portion attached to the tire sidewall. For example, ECER 30 (Article 30 of the Economic Commission for Europe Regulation) requires that a vehicle mounting direction indicator be provided on the sidewall portion that will be on the outside in the vehicle width direction when mounted on a vehicle. Note that in the embodiment, the outside in the vehicle width direction may be expressed as "one side" and the inside in the vehicle width direction as "the other side." This does not exclude the use of "one side" and "the other side" interchangeably.

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

[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 portion 23 is 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 this embodiment has outer middle lug grooves (also referred to as one middle lug groove) 41, middle straight sipes 51, and outer middle sipes 61a (also referred to as sipes 61) provided in the outer middle land portion 22A.

[0034] The outer middle lug groove 41 extends linearly in the tire width direction without any bends. Its base end 41a connects to the outer shoulder circumferential main groove 32A, and its tip end 41b terminates inside the outer middle land portion 22A, thereby forming a non-penetrating groove in 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 arranged side by side in the tire circumferential direction at intervals. The angle θ1 of the centerline of each outer middle lug groove 41 relative to the tire width direction is in the range of 15 degrees ≦ θ1 ≦ 35 degrees. This angle θ1 can be either positive or negative with respect to the tire width direction. As shown in Figures 2 and 4, the outer middle lug groove 41 has a maximum groove width W1 of 1.5 mm or more and 5.0 mm or less in a cross section perpendicular to the center line, and a groove depth D1 of 7.0 mm or more and 10.0 mm or less.

[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 0.60≦L1 / La≦0.80.

[0036] The outer shoulder circumferential main grooves 32A, which are connected to the outer middle lug grooves 41, have groove walls 32Aa between the multiple outer middle lug grooves 41 that are inclined in the same direction relative to the tire circumferential direction. That is, the groove walls 32Aa of the outer shoulder circumferential main grooves 32A on the outer middle land portion 22A side (inner side in the vehicle width direction) are gradually increased and decreased in the tire circumferential direction between the outer middle lug grooves 41, and all of them are inclined in the same direction. Therefore, the groove walls 32Aa of the outer shoulder circumferential main grooves 32A on the outer middle land portion 22A side are formed jaggedly along the tire circumferential direction.

[0037] The middle straight 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 main groove 31A.

[0038] Here, the "sipe" referred to in the embodiment is a narrow groove formed in the tread contact surface 2B, and when the pneumatic tire 1 is mounted on a specified rim and under a specified internal pressure condition, the wall surfaces of the narrow groove may not come into contact with each other when no load is applied, but when the narrow groove is located in the contact surface formed on the flat plate when a load is applied vertically on the flat plate, or when the land portion where the narrow groove is formed collapses, the wall surfaces of the narrow groove, 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. The sipe has a groove width of 1.0 mm or less and a groove depth of 4.0 mm to 8.0 mm.

[0039] The outer middle sipes 61a extend parallel to the outer middle lug grooves 41 along the inclination of the outer middle lug grooves 41, and multiple outer middle sipes 61a are arranged side by side in the tire circumferential direction. The outer middle sipes 61a are formed in a zigzag or wavy shape by repeatedly bending and oscillating 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 main groove 31A or the outer shoulder circumferential main groove 32A.

[0040] Furthermore, the sipes 61 of the embodiment including the outer middle sipe 61a may be so-called three-dimensional sipes or two-dimensional sipes. The three-dimensional sipes referred to here have curved wall surfaces with amplitude in the width direction of the sipe 61 in both cross-sectional views with the length direction of the sipe 61 as the normal direction (cross-sectional views including the width direction and depth direction of the sipe 61) and cross-sectional views with the depth direction of the sipe 61 as the normal direction (cross-sectional views including the width direction and length direction of the sipe 61). Furthermore, the two-dimensional sipes have straight wall surfaces in any cross-sectional views with the length direction of the sipe 61 as the normal direction (cross-sectional views including the width direction and depth direction of the sipe 61).

[0041] As shown in FIG. 2 , the pneumatic tire 1 of the embodiment has a center lug groove 42, a center straight sipe 52, and a center sipe 61b (also referred to as a sipe 61) provided in the center land portion 21.

[0042] The center lug grooves 42 extend linearly along the tire width direction without any bends, with their base ends 42a communicating with the outer center circumferential main 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 center lug grooves 42 are formed at an angle with respect to the tire width direction. The center lug grooves 42 are widest at their base ends 42a and gradually decrease in width toward their tips 42b. Multiple center lug grooves 42 are formed side by side in the tire circumferential direction at intervals. The center line of each center lug groove 42 has an angle θ2 with respect to the tire width direction in the range of 15 degrees ≦ θ2 ≦ 35 degrees. This angle θ2 can be either positive or negative with respect to the tire width direction. As shown in FIGS. 2 and 4, the center lug groove 42 has a maximum groove width W2 of 1.5 mm or more and 5.0 mm or less in a cross section perpendicular to the center line, and a groove depth D2 of 7.0 mm or more and 10.0 mm or less.

[0043] Furthermore, the maximum length L2 of the 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 0.65≦L2 / Lb≦0.85.

[0044] The outer center circumferential main grooves 31A, which are connected to the center lug grooves 42, have groove walls 31Aa between the plurality of center lug grooves 42 that are inclined in the same direction relative to the tire circumferential direction. That is, the groove walls 31Aa of the outer center circumferential main grooves 31A on the center land portion 21 side (inner side in the vehicle width direction) are formed so that they gradually increase and decrease in the tire circumferential direction between the center lug grooves 42, and all of them are formed in the same inclination direction. Therefore, the groove walls 31Aa of the outer center circumferential main grooves 31A on the center land portion 21 side are formed jaggedly along the tire circumferential direction.

[0045] The center straight sipe 52 extends linearly without bending from the tip 42b of the center lug groove 42 along the direction in which the center lug groove 42 extends, and communicates with the inner center circumferential main groove 31B.

[0046] The center sipes 61b extend parallel to the center lug grooves 42 along the inclination of the center lug grooves 42, and multiple center sipes 61b are arranged side by side in the tire circumferential direction. The center sipes 61b are formed in a zigzag or wavy shape by repeatedly bending and oscillating 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 main groove 31A or the inner center circumferential main 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) 43, an inner second middle lug groove (also referred to as the other second middle lug groove) 44, an inner first middle sipe 61c (also referred to as sipe 61), and an inner second middle sipe 61d (also referred to as sipe 61) in the inner middle land portion 22B.

[0048] The inner first middle lug groove 43 extends linearly along the tire width direction without any bends. Its base end 43a connects to the inner center circumferential main groove 31B, and its tip end 43b terminates inside the inner middle land portion 22B, thereby forming a non-penetrating groove in the inner middle land portion 22B. The inner first middle lug groove 43 is formed at an angle with respect to the tire width direction. The inner first middle lug groove 43 has the widest groove width at its base end 43a and gradually decreases in width toward its tip end 43b. Multiple inner first middle lug grooves 43 are arranged side by side in the tire circumferential direction at intervals. The angle θ3 of the centerline of each inner first middle lug groove 43 relative to the tire width direction is in the range of 30 degrees ≦ θ3 ≦ 50 degrees. This angle θ3 can be either positive or negative with respect to the tire width direction. As shown in Figures 2 and 4, the inner first middle lug groove 43 has a maximum groove width W3 of 2.0 mm or more and 5.5 mm or less in a cross section perpendicular to the center line, and a groove depth D3 of 5.5 mm or more and 10.0 mm or less.

[0049] The maximum length L3 of the inner first middle lug groove 43 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 0.40≦L3 / Lc≦0.60.

[0050] The inner second middle lug groove 44 extends linearly along the tire width direction without any bends. Its base end 44a connects to the inner shoulder circumferential main groove 32B, and its tip end 44b terminates inside the inner middle land portion 22B, thereby forming a non-penetrating groove in the inner middle land portion 22B. The inner second middle lug groove 44 is formed at an angle with respect to the tire width direction. The inner second 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 second middle lug grooves 44 are arranged side by side in the tire circumferential direction at intervals. The angle θ4 of the centerline of each inner second middle lug groove 44 relative to the tire width direction is in the range of 1°≦θ4≦15°. This angle θ4 can be either positive or negative with respect to the tire width direction. As shown in Figures 2 and 4, the inner second middle lug groove 44 has a maximum groove width W4 of 1.5 mm or more and 4.5 mm or less in a cross section perpendicular to the center line, and a groove depth D4 of 7.0 mm or more and 10.0 mm or less.

[0051] The maximum length L4 of the inner second 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 0.20≦L4 / Lc≦0.40.

[0052] The inner first middle lug grooves 43 and the inner second middle lug grooves 44 are arranged alternately in the tire circumferential direction.

[0053] The inner first middle sipes 61c extend parallel to the inner first middle lug grooves 43 along the inclination of the inner first middle lug grooves 43, and multiple inner first middle sipes 61c are arranged side by side in the tire circumferential direction. The inner first middle sipes 61c are formed in a zigzag or wavy shape by repeatedly bending and oscillating in the tire circumferential direction. The ends of the inner first middle sipes 61c may terminate inside the inner middle land portion 22B or may communicate with the inner center circumferential main groove 31B.

[0054] The inner second middle sipes 61d extend parallel to the inner second middle lug grooves 44 along the inclination of the inner second middle lug grooves 44, and multiple inner second middle sipes 61d are arranged side by side in the tire circumferential direction. The inner second middle sipes 61d are formed in a zigzag or wavy shape by repeatedly bending and oscillating in the tire circumferential direction. The ends of the inner second middle sipes 61d may terminate inside the inner middle land portion 22B or may communicate with the inner shoulder circumferential main groove 32B.

[0055] The inner first middle sipe 61c and the inner second middle sipe 61d may be in communication with each other, but in this embodiment, they are arranged at an interval from each other in the tire width direction.

[0056] As shown in FIG. 2, the pneumatic tire 1 of this embodiment has outer shoulder lug grooves (one shoulder lug groove) 45, outer shoulder sipes 61e (also referred to as sipes 61), and outer shoulder circumferential grooves 71 provided in the outer shoulder land portion 23A.

[0057] The outer shoulder lug grooves 45 extend linearly or curvedly along the tire width direction without any bends, with their base ends 45a communicating with the outer shoulder circumferential main groove 32A and extending outward in the tire width direction, passing through the ground contact edge T. The outer shoulder lug grooves 45 are formed at an angle with respect to the tire width direction. Multiple outer shoulder lug grooves 45 are arranged side by side in the tire circumferential direction at intervals. The base ends 45a of the outer shoulder lug grooves 45 face the base ends 41a of the outer middle lug grooves 41 in the tire width direction, with the outer shoulder circumferential main groove 32A as the boundary. That is, the same number of outer shoulder lug grooves 45 as the outer middle lug grooves 41 are arranged. The outer shoulder lug grooves 45 have a groove width of 3.0 mm or more and 6.0 mm or less and a groove depth of 6.5 mm or more and 10.0 mm or less.

[0058] The outer shoulder sipes 61e extend parallel to and along the outer shoulder lug grooves 45, and multiple outer shoulder sipes 61e are arranged side by side in the tire circumferential direction. The outer shoulder sipes 61e are formed in a zigzag or wavy shape by repeatedly bending and oscillating in the tire circumferential direction. The ends of the outer shoulder sipes 61e may terminate inside the outer middle land portion 22A or may communicate with the outer shoulder circumferential main groove 32A.

[0059] The outer shoulder circumferential grooves 71 are arranged linearly without any bends along the tire circumferential direction between the outer shoulder circumferential main groove 32A and the ground contact edge T, and are arranged between the outer shoulder lug grooves 45 aligned in the tire circumferential direction, with one end connected to one of the outer shoulder lug grooves 45 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.

[0060] As shown in FIG. 2, the pneumatic tire 1 of this embodiment is provided with inner shoulder lug grooves (the other shoulder lug grooves) 46, inner shoulder sipes 61f (also referred to as sipes 61), and inner shoulder circumferential grooves 72 in the inner shoulder land portion 23B.

[0061] The inner shoulder lug groove 46 extends linearly or curvedly along the tire width direction without any bends, with its base end 46a communicating with the inner shoulder circumferential main groove 32B and extending outward in the tire width direction, passing through the ground contact edge T. The inner shoulder lug groove 46 is formed at an angle with respect to the tire width direction. Multiple inner shoulder lug grooves 46 are arranged side by side in the tire circumferential direction at intervals. The base end 46a of each inner shoulder lug groove 46 faces the base end 44a of the inner second middle lug groove 44 in the tire width direction, with the inner shoulder circumferential main groove 32B as the boundary. That is, the same number of inner shoulder lug grooves 46 as the middle lug grooves 44 are arranged on the inner side. The inner shoulder lug groove 46 has a groove width of 3.0 mm or more and 6.0 mm or less and a groove depth of 6.5 mm or more and 10.0 mm or less.

[0062] The inner shoulder sipes 61f extend parallel to and along the inner shoulder lug grooves 46, and multiple inner shoulder sipes 61f are arranged side by side in the tire circumferential direction. The inner shoulder sipes 61f are formed in a zigzag or wavy shape by repeatedly bending and oscillating in the tire circumferential direction. The ends of the inner shoulder sipes 61f may terminate inside the inner middle land portion 22B or may communicate with the inner shoulder circumferential main groove 32B.

[0063] The inner shoulder circumferential groove 72 is arranged linearly without a bend along the tire circumferential direction between the inner shoulder circumferential main groove 32B and the ground contact edge T, and is arranged between the inner shoulder lug grooves 46 aligned in the tire circumferential direction, with one end connected to one of the inner shoulder lug grooves 46 and the other end terminating inside the inner shoulder land portion 23B. The inner shoulder circumferential grooves 72 are aligned in a row in the tire circumferential direction. The inner shoulder circumferential groove 72 does not communicate with the inner shoulder sipe 61f but 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.

[0064] The pneumatic tire 1 of the embodiment does not have any grooves other than the grooves 31, 32, 41, 42, 43, 44, 45, 46, 71, 72, sipes 51, 52, 61, and sipes described above.

[0065] When the pneumatic tire 1 according to this embodiment is mounted on a vehicle, the pneumatic tire 1 is mounted on a rim wheel, and is inflated by filling the interior with air. When a vehicle equipped with the pneumatic tire 1 travels, the pneumatic tire 1 rotates while the lower part of the tread contact surface 2B of the tread portion 2 comes into contact with the road surface. When a vehicle equipped with the pneumatic tire 1 travels on a dry road surface, the vehicle travels by transmitting driving force and braking force to the road surface and generating turning force mainly due to 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 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, and 46, 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 road surfaces, the tire also utilizes the edge effect of the grooves 31, 32, 41, 42, 43, 44, 45, 46 and the sipes 51, 52, 61. That is, when traveling on snowy or icy road surfaces, the tire also utilizes the resistance created by the edges of the grooves 31, 32, 41, 42, 43, 44, 45, 46 and the sipes 51, 52, 61 catching on the snow or ice surface. When traveling on icy road surfaces, the sipes 61 absorb water from the surface of the icy road, removing the water film between the icy road surface and the tread contact surface 2B, thereby facilitating contact between the icy road surface and the tread contact surface 2B. As a result, the resistance between the tread contact surface 2B and the icy road surface increases due to frictional force and the edge effect, thereby providing ice performance. This allows the vehicle to travel on icy road surfaces.

[0069] The grooves 31, 32, 41, 42, 43, 44, 45, 46 and sipes 51, 52, 61 formed in the tread portion 2 contribute to ensuring running performance when running on wet road surfaces, snowy road surfaces, and icy road surfaces, and therefore, in order to improve wet performance, which is running performance on wet road surfaces, for example, 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, etc. is increased, water on the road surface can easily enter the grooves when running 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, and 46 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] Here, when the groove area of ​​the tread portion 2 is increased, the volume of the land portions 20 defined by the grooves 31, 32, 41, 42, 43, 44, 45, and 46 decreases as the groove area increases. When the volume of the land portions 20 decreases, the rigidity of the land portions 20 decreases, and when the rigidity of the land portions 20 decreases, the land portions 20 become more likely to deform and collapse when a load is applied. When the land portions 20 collapse, the contact area of ​​the collapsed land portions 20 decreases, which may make it difficult to ensure driving performance.

[0072] For example, when traveling on an icy road surface, in addition to the edge effect due to the edge components of the grooves, the frictional force caused by the tread contact surface 2B contacting the icy road surface is also important. However, if the rigidity of the land portions 20 is reduced by increasing the groove area of ​​the tread portion 2, the land portions 20 will be more likely to collapse when a load is applied, which will likely reduce the contact area and make it difficult to ensure driving performance due to frictional force. Therefore, if the rigidity of the land portions 20 is reduced by increasing the groove area of ​​the tread portion 2, the land portions 20 will be more likely to collapse during braking when traveling on an icy road surface, which will likely reduce the contact area and make it difficult to ensure braking performance on an icy road surface.

[0073] The pneumatic tire 1 of the embodiment is characterized by having one center circumferential main groove 31A and the other center circumferential main groove 31B, one shoulder circumferential main groove 32A and the other shoulder circumferential main groove 32B, a center land portion 21, one middle land portion 22A and the other middle land portion 22B, one shoulder land portion 23A and the other shoulder land portion 23B, and a plurality of center lug grooves 42 arranged side by side in the tire width direction, with base ends 42a communicating with one center circumferential main groove 31A and tip ends 42b terminating inside the center land portion 21. one middle lug groove 41, a base end 41a of which is connected to one shoulder circumferential main groove 32A and a tip end 41b of which terminates inside one middle land portion 22A, and a plurality of which are arranged side by side in the tire width direction; the other first middle lug groove 43, a base end 43a of which is connected to the other center circumferential main groove 31B, a tip end 43b of which terminates inside the other middle land portion 22B, and a plurality of which are arranged side by side in the tire width direction; one shoulder lug groove 45, a base end 45a of which is connected to one shoulder circumferential main groove 32A, extends along the tire width direction, and passes through the ground contact edge; the other shoulder lug groove 46 having a base end 46a connected to the other shoulder circumferential main groove 32B and extending along the tire width direction and passing through the ground contact edge; a linear middle straight sipe 51 extending from the tip 41b of one middle lug groove 41 to connect to one center circumferential main groove 31A; and a linear middle straight sipe 51 extending from the tip 42b of the center lug groove 42 to connect to the other center circumferential main groove 31B. and a center straight sipe 52, wherein the middle lug grooves 41, center lug grooves 42 on one side, the first middle lug grooves 43 on the other side, and the second middle lug grooves 44 on the other side are arranged with their inclination directions with respect to the tire width direction alternately in opposite directions in the order of the tire width direction, and the shoulder circumferential main grooves 32A on one side are formed so that the groove walls 32Aa between the multiple middle lug grooves 41 on the one side are inclined in the same direction with respect to the tire circumferential direction, and the center circumferential main grooves 31A on one side are formed so that the groove walls 31Aa between the multiple center lug grooves 42 are inclined in the same direction with respect to the tire circumferential direction.

[0074] In the pneumatic tire 1 of the embodiment, the inclination directions of the lug grooves 41, 42, 43, and 44 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 terminating the lug grooves 41, 42 within the land portions 22A, 21 and arranging the straight sipes 51, 52, snow column shear strength is improved while ensuring the rigidity of the land portions 22A, 21 and suppressing collapse, thereby improving snow and ice performance and wear resistance. The straight sipes 51, 52 are located near the center portion in the tire width direction. This center portion is related to traction performance during starting, and penetrating the land portions 22A, 21 with the straight sipes 51, 52 improves traction performance on snow and ice. Furthermore, the shoulder lug grooves 45, 46 communicate with the shoulder circumferential main grooves 32A, 32B, improving drainage. As a result, the pneumatic tire 1 can improve wear resistance while ensuring performance on snow and ice and wet conditions.

[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 0.60≦L1 / La≦0.80, and the maximum length L2 in the tire width direction of the center lug groove 42 and the maximum dimension Lb in the tire width direction of the center land portion 21 satisfy the relationship 0.65≦L2 / Lb≦0.85.

[0076] In the pneumatic tire 1 of the embodiment, when L1 / La is less than 0.60, wear resistance improves but snow performance tends to deteriorate, while when it exceeds 0.80, snow performance improves but wear resistance tends to deteriorate, so the above range is set. Furthermore, in the pneumatic tire 1 of the embodiment, satisfying the relationship 0.65≦L1 / La≦0.75 is preferable because the above effect is significantly achieved. Furthermore, in the pneumatic tire 1 of the embodiment, when L2 / Lb is less than 0.65, wear resistance also improves but snow performance tends to deteriorate, while when it exceeds 0.85, snow performance also improves but wear resistance tends to deteriorate, so the above range is set. Furthermore, in the pneumatic tire 1 of the embodiment, satisfying the relationship 0.70≦L2 / Lb≦0.80 is preferable because the above effect is significantly achieved.

[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 43 and the maximum dimension Lc in the tire width direction of the other middle land portion 22B satisfy the relationship 0.40≦L3 / Lc≦0.60, and the maximum length L4 in the tire width direction of the other second middle lug groove 44 and the maximum dimension Lc in the tire width direction of the other middle land portion 22B satisfy the relationship 0.20≦L4 / Lc≦0.40.

[0078] In the pneumatic tire 1 of the embodiment, when L3 / Lc is less than 0.40, ice performance improves but snow performance tends to deteriorate, while when it exceeds 0.60, snow performance improves but ice performance and wear resistance tend to deteriorate, so the above range is set. Furthermore, in the pneumatic tire 1 of the embodiment, satisfying the relationship 0.45≦L3 / Lc≦0.55 is preferable because the above effect is significantly achieved. Similarly, when L4 / Lc is less than 0.20, ice performance improves but snow performance tends to deteriorate, while when it exceeds 0.40, snow performance improves but ice performance and wear resistance tend to deteriorate, so the above range is set. Furthermore, in the pneumatic tire 1 of the embodiment, satisfying the relationship 0.25≦L4 / Lc≦0.35 is preferable because the above effect is significantly achieved.

[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 ±15 [deg]≦θ1≦±35 [deg], the angle θ2 of the center lug groove 42 relative to the tire width direction is in the range of ±15 [deg]≦θ2≦±35 [deg], the angle θ3 of the other first middle lug groove 43 relative to the tire width direction is in the range of ±30 [deg]≦θ3≦±50 [deg], and the angle θ4 of the other second middle lug groove 44 relative to the tire width direction is in the range of ±1 [deg]≦θ4≦±15 [deg].

[0080] In the pneumatic tire 1 of the embodiment, when the angle θ1 is less than 15 degrees, the snow traction index (0 degrees STI) component increases, which promotes collapse of one middle land portion 22A during braking, tending to deteriorate ice performance. When the angle θ1 exceeds 35 degrees, the rigidity of one middle land portion 22A decreases, tending to deteriorate wear resistance. Therefore, the above range is set. Furthermore, in the pneumatic tire 1 of the embodiment, satisfying the relationship of 20 degrees ≦ θ1 ≦ 30 degrees is preferable because the above effect is significantly achieved. Furthermore, when the angle θ2 is less than 15 degrees, the snow traction index (0 degrees STI) component increases, which promotes collapse of the center land portion 21 during braking, tending to deteriorate ice performance. When the angle θ2 exceeds 35 degrees, the rigidity of the center land portion 21 decreases, tending to deteriorate wear resistance. Therefore, the above range is set. In the pneumatic tire 1 of the embodiment, the above-mentioned effect is preferably achieved by satisfying the relationship 20 degrees ≦ θ2 ≦ 30 degrees. Furthermore, if the angle θ3 is less than 30 degrees, the snow traction index (0 degrees STI) component increases, which promotes the collapse of the other middle land portion 22B during braking and tends to deteriorate ice performance. If the angle θ3 exceeds 50 degrees, the rigidity of the other middle land portion 22B decreases, which tends to deteriorate wear resistance. Therefore, the above-mentioned range is set. Furthermore, in the pneumatic tire 1 of the embodiment, the above-mentioned effect is preferably achieved by satisfying the relationship 35 degrees ≦ θ3 ≦ 45 degrees. Furthermore, if the angle θ4 is less than 1 degree, the snow traction index (0 degree STI) component increases, which encourages the other middle land portion 22B to collapse during braking, tending to deteriorate ice performance, while if the angle θ4 exceeds 15 degrees, the rigidity of the other middle land portion 22B decreases, tending to deteriorate wear resistance. Therefore, the above range is set. Furthermore, in the pneumatic tire 1 of the embodiment, satisfying the relationship 5 degrees≦θ4≦10 degrees is preferable because it significantly achieves the above-mentioned effects.

[0081] 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 all circumferential main grooves 31, 32 satisfy the relationship of 0.70≦D1 / D≦1.00, the groove depth D2 of the center lug groove 42 and the groove depth D of all circumferential main grooves 31, 32 satisfy the relationship of 0.70≦D2 / D≦1.00, the groove depth D3 of the other first middle lug groove 43 and the groove depth D of all circumferential main grooves 31, 32 satisfy the relationship of 0.70≦D3 / D≦1.00, and the groove depth D4 of the other second middle lug groove 44 and the groove depth D of all circumferential main grooves 31, 32 satisfy the relationship of 0.70≦D4 / D≦1.00.

[0082] According to the pneumatic tire 1 of the embodiment, when D1 / D, D2 / D, D3 / D, and D4 / D are less than 0.70, the wear resistance improves but the wet performance tends to deteriorate, and when they exceed 1.00, the wet performance improves but the rigidity of the land portions 22A, 21, and 22B decreases, and the wear resistance tends to deteriorate, so they are set within the above ranges.

[0083] In addition, in the pneumatic tire 1 of the embodiment, the groove width W1 of one middle lug groove 41, the groove width W2 of the center lug groove 42, the groove width W3 of the other first middle lug groove 43, and the groove width W4 of the other second middle lug groove 44 are in the range of 1.5 mm or more and 5.0 mm or less, and the base end 42a of the center lug groove 42 does not exist on the extension of the tip 41b of one middle lug groove 41, and the base end 43a of the other first middle lug groove 43 does not exist on the extension of the tip 42b of the center lug groove 42.

[0084] In 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, wear resistance improves but wet performance tends to deteriorate, while when they exceed 5.0 mm, wet performance improves but the rigidity of the land portions 22A, 21, and 22B decreases, tending to deteriorate wear resistance. Furthermore, the base end 42 a of the center lug groove 42 is not on the extension of the tip 41 b of the middle lug groove 41, and the base end 43 a of the other first middle lug groove 43 is not on the extension of the tip 42 b of the center lug groove 42. This prevents the lug grooves 41, 42 and the lug grooves 42, 43 from being too close to each other, ensuring the rigidity of the land portions 22A, 21, and 22B and improving wear resistance.

[0085] Furthermore, in the pneumatic tire 1 of the embodiment, the orientation with respect to the vehicle width direction when mounted on a vehicle is specified, with one side being the outer side in the vehicle width direction and the other being the inner side in the vehicle width direction.

[0086] According to the embodiment of the pneumatic tire 1, when the lug grooves 41, 42, and 43 have their base ends on the outer side in the vehicle width direction, water is drained into the outer circumferential main grooves 32A, 31, and 32B during cornering, making it easier for water to escape and improving performance on snow and ice and wet surfaces.

[0087] In addition, in the pneumatic tire 1 of the embodiment, at the tread contact surface 2B, the groove area ratio Go on the outer side in the vehicle width direction and the groove area ratio Gi on the inner side in the vehicle width direction, with the tire equatorial plane CL as the boundary, are Gi < Go, and satisfy the relationship 1.1 ≦ Go / Gi ≦ 1.3.

[0088] Here, the groove area ratio is defined as the percentage of groove area / (groove area + contact area). The groove area is the total opening area of ​​the grooves in the tire contact patch. The contact area is measured between the contact edges based on the plane of contact between the pneumatic tire 1 and a flat plate when the pneumatic tire 1 is mounted on a standard rim, inflated to the standard internal pressure, and placed perpendicular to a flat plate in a stationary state and subjected to a load corresponding to the standard load. The groove area does not include sipes.

[0089] According to the pneumatic tire 1 of the embodiment, by setting the groove area ratio Gi<Go, snow performance and wet performance are improved on the outer side in the vehicle width direction, and ice performance is improved by increasing the contact area on the inner side in the vehicle width direction, thereby achieving a high level of snow and ice performance, wear resistance, and wet performance. According to the pneumatic tire 1 of the embodiment, if Go / Gi is less than 1.1, ice performance is improved but snow performance and wet performance tend to deteriorate, and if it exceeds 1.3, snow performance and wet performance are improved but ice performance tends to deteriorate, so the above range is set. Furthermore, according to the pneumatic tire 1 of the embodiment, satisfying the relationship 1.15≦Go / Gi≦1.25 is preferable because the above effects are significantly obtained.

[0090] In addition, the pneumatic tire 1 of the embodiment has sipes 61 arranged in the land portion 20, so that it can be used as a studless tire that ensures driving performance on icy and snowy roads, or an all-season tire that ensures driving performance in winter.

[0091] In the pneumatic tire 1 of the embodiment, the sipes 61 are arranged parallel to the extending direction of the lug grooves 41 , 42 , 43 , 44 , 45 , and 46 provided in each land portion 20 .

[0092] According to the pneumatic tire 1 of the embodiment, the length of the sipes 61 can be increased, resulting in a large edge amount and improved snow and ice performance.

[0093] In the present embodiment, as described above, the 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.

[0094] 5 to 7 are tables showing the results of performance tests of the 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, wet performance, and uneven wear resistance.

[0095] 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 1800 cc, adjusting the air pressure to 240 kPa for the front wheels and 240 kPa for the rear wheels, and running the evaluation vehicle.

[0096] To evaluate ice performance, a vehicle fitted with the test tires is subjected to a braking test on an icy test course, measuring the braking distance. Based on the results of these tests, the reciprocal of the tire is used to evaluate the performance as an index, with the conventional tire being used as the standard (100). The higher the index value, the better.

[0097] The evaluation test for snow performance involves braking tests on a test vehicle fitted with the test tires on a test course on a snowy road surface, and the braking distance is measured. Based on the results of these measurements, the reciprocal of the tire is used to evaluate the performance as an index, with the conventional tire being set as the standard (100). The higher the evaluation value, the better.

[0098] The wet performance evaluation test involves a braking test on a test vehicle fitted with the test tire on a wet road test course with 1 mm of water depth, and the braking distance is measured. Based on the measurement results, the reciprocal is used to evaluate the tire's performance on an index basis, with the conventional tire being set at 100. The higher the evaluation value, the better.

[0099] 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 as an index, with the conventional tire being used as the standard (100). A value of 98 or higher is considered desirable.

[0100] The conventional pneumatic tire has four straight circumferential main grooves, a center lug groove, an outer middle lug groove, and an inner first middle lug groove, but each lug groove penetrates the land portion and is inclined in the same direction relative to the tire width direction. The conventional pneumatic tire does not have an inner second middle lug groove, inner or outer shoulder lug grooves, or straight sipes, and the groove walls of the outer middle circumferential main groove and outer center circumferential main groove are not inclined.

[0101] As shown in Figure 2, the pneumatic tire of the example has four straight circumferential main grooves: a center lug groove, an outer middle lug groove, an inner first middle lug groove, and an inner second middle lug groove, and each lug groove does not penetrate a land portion and is alternately inclined in opposite directions relative to the tire width direction. The pneumatic tire of the example also has inner and outer shoulder lug grooves and straight sipes, and the groove walls of the outer middle circumferential main groove and outer center circumferential main groove are inclined.

[0102] As shown in the test results, the pneumatic tire of this example has improved ice performance, snow performance, wet braking performance, and wear resistance compared to the conventional tire.

[0103] The present disclosure includes the following inventions: [Invention 1] One center circumferential main groove and the other center circumferential main groove are formed linearly along the tire circumferential direction and adjacent to each other on either side of the tire equatorial plane, One shoulder circumferential main groove and the other shoulder circumferential main groove are formed linearly along the tire circumferential direction and adjacent to each other on the tire widthwise outer side of each center circumferential main groove, A center land portion defined between the center circumferential main grooves and continuous in the tire circumferential direction, One middle land portion and the other middle land portion defined between the shoulder circumferential main groove and the center circumferential main groove and continuous in the tire circumferential direction, One shoulder land portion and the other shoulder land portion defined on the tire widthwise outer side of each shoulder circumferential main groove, A plurality of center lug grooves arranged side by side in the tire width direction in the center land portion, each having a base end extending along the tire width direction that communicates with one center circumferential main groove and a tip end that terminates inside the center land portion, one middle lug groove in the one middle land portion, a base end extending along the tire width direction that is connected to one shoulder circumferential main groove and a tip end that terminates inside the one middle land portion, and arranged in a row in the tire width direction; one shoulder lug groove in the one shoulder land portion, a base end communicating with the one shoulder circumferential main groove, extending along the tire width direction, passing the ground contact edge, and arranged in a row in the tire width direction; another first middle lug groove in the other middle land portion, a base end extending along the tire width direction that is connected to the other center circumferential main groove and a tip end that terminates inside the other middle land portion, and arranged in a row in the tire width direction; another second middle lug groove in the other middle land portion, a base end extending along the tire width direction that is connected to the other shoulder circumferential main groove and a tip end that terminates inside the other middle land portion, and arranged in a row in the tire width direction In the other shoulder land portion, a second shoulder lug groove extends in the tire width direction, the second shoulder lug groove having a base end connected to the second shoulder circumferential main groove, the second shoulder lug groove extending along the tire width direction and passing through the ground contact edge, and a straight middle straight sipe extends from a tip end of the first middle lug groove in the one middle land portion and connects to the one center circumferential main groove.a center straight sipe in the center land portion extending from a tip of the center lug groove and communicating with the other center circumferential main groove, wherein the one middle lug groove, the center lug groove, the other first middle lug groove, and the other second middle lug groove are arranged so that their inclination directions with respect to the tire width direction are alternately opposite, the one shoulder circumferential main groove is formed so that groove walls between the plurality of one middle lug grooves are inclined in the same direction with respect to the tire circumferential direction, and the one center circumferential main groove is formed so that groove walls between the plurality of center lug grooves are inclined in the same direction with respect to the tire circumferential direction. [Invention 2] The tire according to Invention 1, wherein the maximum length L1 of the one middle lug groove in the tire width direction and the maximum dimension La of the one middle land portion in the tire width direction satisfy the relationship of 0.60≦L1 / La≦0.80, and the maximum length L2 of the 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 of 0.65≦L2 / Lb≦0.85. [Invention 3] The tire according to Invention 1 or 2, wherein the maximum length L3 of the other first middle lug groove in the tire width direction and the maximum dimension Lc of the other middle land portion in the tire width direction satisfy the relationship of 0.40≦L3 / Lc≦0.60, and the maximum length L4 of the other second middle lug groove in the tire width direction and the maximum dimension Lc of the other middle land portion in the tire width direction satisfy the relationship of 0.20≦L4 / Lc≦0.40. [Invention 4] The tire according to any one of Inventions 1 to 3, wherein the angle θ1 of the one middle lug groove with respect to the tire width direction is in the range of ±15 degrees ≦ θ1 ≦ ±35 degrees, the angle θ2 of the center lug groove with respect to the tire width direction is in the range of ±15 degrees ≦ θ2 ≦ ±35 degrees, the angle θ3 of the other first middle lug groove with respect to the tire width direction is in the range of ±30 degrees ≦ θ3 ≦ ±50 degrees, and the angle θ4 of the other second middle lug groove with respect to the tire width direction is in the range of ±1 degree ≦ θ4 ≦ ±15 degrees. [Invention 5] The groove depth D1 of the one middle lug groove and the groove depths D of all of the circumferential main grooves satisfy the relationship 0.70 ≦ D1 / D ≦ 1.00,5. The tire according to any one of Inventions 1 to 4, wherein a groove depth D2 of the center lug groove and a groove depth D of all of the circumferential main grooves satisfy a relationship of 0.70≦D2 / D≦1.00, a groove depth D3 of the other first middle lug groove and a groove depth D of all of the circumferential main grooves satisfy a relationship of 0.70≦D3 / D≦1.00, and a groove depth D4 of the other second middle lug groove and a groove depth D of all of the circumferential main grooves satisfy a relationship of 0.70≦D4 / D≦1.00. [Invention 6] The tire according to any one of Inventions 1 to 5, wherein the groove width W1 of the one middle lug groove, the groove width W2 of the center lug groove, the groove width W3 of the other first middle lug groove, and the groove width W4 of the other second middle lug groove are in the range of 1.5 mm to 5.0 mm, the base end of the center lug groove does not lie on an extension of the tip end of the one middle lug groove, and the base end of the other first middle lug groove does not lie on an extension of the tip end of the center lug groove. [Invention 7] The tire according to any one of Inventions 1 to 6, wherein the orientation with respect to the vehicle width direction when mounted on a vehicle is specified, the one groove being on the outer side in the vehicle width direction and the other groove being on the inner side in the vehicle width direction. [Invention 8] The tire according to Invention 7, wherein, in the tread contact patch, 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 the tire equatorial plane as the boundary, are such that Gi<Go and satisfy the relationship 1.1≦Go / Gi≦1.3. [Invention 9] The tire according to any one of Inventions 1 to 8, which is a winter tire or an all-season tire having sipes extending in the tire width direction in each of the land portions. [Invention 10] The tire according to Invention 9, wherein the sipes are arranged parallel to the extension direction of each of the lug grooves provided in each of the land portions.

[0104] DESCRIPTION OF SYMBOLS 1 Pneumatic tire (tire) 21 Center land portion 22A Outer middle land portion (one middle land portion) 22B Inner middle land portion (other middle land portion) 23A Outer shoulder land portion (one shoulder land portion) 23B Inner shoulder land portion (other shoulder land portion) 31A Outer center circumferential main groove (one center circumferential main groove) 31Aa Groove wall 31B Inner center circumferential main groove (other center circumferential main groove) 32A Outer shoulder circumferential main groove (one shoulder circumferential main groove) 32Aa Groove wall 32B Inner shoulder circumferential main groove (other shoulder circumferential main groove) 41 Outer middle lug groove (one middle lug groove) 41a Base end 41b Tip end 42 Center lug groove 42a Base end 42b Tip end 43 Inner first middle lug groove (other first middle lug groove) 43a Base end 43b Tip 44 Inner second middle lug groove (other second middle lug groove) 44a Base end 44b Tip 45 Outer shoulder lug groove (one shoulder lug groove) 45a Base end 46 Inner shoulder lug groove (other shoulder lug groove) 46a Base end 51 Middle straight sipe 52 Center straight sipe 61 Sipe

Claims

1. One center circumferential main groove and the other center circumferential main groove are formed linearly along the tire circumferential direction and adjacent to each other on either side of the tire equatorial plane; one shoulder circumferential main groove and the other shoulder circumferential main groove are formed linearly along the tire circumferential direction and adjacent to each other on the tire widthwise outer side of each of the center circumferential main grooves; a center land portion defined between the center circumferential main grooves and continuing in the tire circumferential direction; one middle land portion and the other middle land portion defined between the shoulder circumferential main groove and the center circumferential main groove, respectively, and continuing in the tire circumferential direction; one shoulder land portion and the other shoulder land portion defined on the tire widthwise outer side of each of the shoulder circumferential main grooves; and center lug grooves arranged side by side in the tire width direction in the center land portion, with base ends extending along the tire width direction in the center land portion communicating with one of the center circumferential main grooves and with tips terminating inside the center land portion. one middle lug groove in the one middle land portion, a base end extending along the tire width direction that is connected to one shoulder circumferential main groove and a tip end that terminates inside the one middle land portion, and arranged in a row in the tire width direction; one shoulder lug groove in the one shoulder land portion, a base end communicating with the one shoulder circumferential main groove, extending along the tire width direction, passing the ground contact edge, and arranged in a row in the tire width direction; another first middle lug groove in the other middle land portion, a base end extending along the tire width direction that is connected to the other center circumferential main groove and a tip end that terminates inside the other middle land portion, and arranged in a row in the tire width direction; another second middle lug groove in the other middle land portion, a base end extending along the tire width direction that is connected to the other shoulder circumferential main groove and a tip end that terminates inside the other middle land portion, and arranged in a row in the tire width direction In the other shoulder land portion, a second shoulder lug groove extends in the tire width direction, the second shoulder lug groove having a base end connected to the second shoulder circumferential main groove, the second shoulder lug groove extending along the tire width direction and passing through the ground contact edge, and a straight middle straight sipe extends from a tip end of the first middle lug groove in the one middle land portion and connects to the one center circumferential main groove.a center straight sipe in the center land portion extending from a tip of the center lug groove and communicating with the other center circumferential main groove, wherein the one middle lug groove, the center lug groove, the other first middle lug groove, and the other second middle lug groove are arranged so that their inclination directions with respect to the tire width direction are alternately opposite, the one shoulder circumferential main groove is formed so that groove walls between the plurality of one middle lug grooves are inclined in the same direction with respect to the tire circumferential direction, and the one center circumferential main groove is formed so that groove walls between the plurality of center lug grooves are inclined in the same direction with respect to the tire circumferential direction.

2. The tire according to claim 1, wherein the maximum length L1 of one of the middle lug grooves in the tire width direction and the maximum dimension La of one of the middle land portions in the tire width direction satisfy the relationship 0.60≦L1 / La≦0.80, and the maximum length L2 of the 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 0.65≦L2 / Lb≦0.

85.

3. The tire according to claim 1, wherein the maximum length L3 of the other first middle lug groove in the tire width direction and the maximum dimension Lc of the other middle land portion in the tire width direction satisfy the relationship 0.40≦L3 / Lc≦0.60, and the maximum length L4 of the other second middle lug groove in the tire width direction and the maximum dimension Lc of the other middle land portion in the tire width direction satisfy the relationship 0.20≦L4 / Lc≦0.

40.

4. The tire according to claim 1, wherein the angle θ1 of the one middle lug groove relative to the tire width direction is in the range of ±15 degrees ≦ θ1 ≦ ±35 degrees, the angle θ2 of the center lug groove relative to the tire width direction is in the range of ±15 degrees ≦ θ2 ≦ ±35 degrees, the angle θ3 of the other first middle lug groove relative to the tire width direction is in the range of ±30 degrees ≦ θ3 ≦ ±50 degrees, and the angle θ4 of the other second middle lug groove relative to the tire width direction is in the range of ±1 degree ≦ θ4 ≦ ±15 degrees.

5. The tire according to claim 1, wherein a groove depth D1 of the one middle lug groove and a groove depth D of all of the circumferential main grooves satisfy the relationship 0.70≦D1 / D≦1.00, a groove depth D2 of the center lug groove and a groove depth D of all of the circumferential main grooves satisfy the relationship 0.70≦D2 / D≦1.00, a groove depth D3 of the other first middle lug groove and a groove depth D of all of the circumferential main grooves satisfy the relationship 0.70≦D3 / D≦1.00, and a groove depth D4 of the other second middle lug groove and a groove depth D of all of the circumferential main grooves satisfy the relationship 0.70≦D4 / D≦1.

00.

6. A tire as set forth in claim 1, wherein the groove width W1 of the one middle lug groove, the groove width W2 of the center lug groove, the groove width W3 of the other first middle lug groove, and the groove width W4 of the other second middle lug groove are in the range of 1.5 mm to 5.0 mm, the base end of the center lug groove does not lie on an extension of the tip end of the one middle lug groove, and the base end of the other first middle lug groove does not lie on an extension of the tip end of the center lug groove.

7. A tire as set forth in claim 1, wherein the orientation with respect to the vehicle width direction when mounted on a vehicle is specified, said one being on the outer side in the vehicle width direction and said other being on the inner side in the vehicle width direction.

8. A tire as set forth in claim 7, wherein, in the tread contact patch, the groove area ratio Go on the outer side in the vehicle width direction and the groove area ratio Gi on the inner side in the vehicle width direction, with the tire equatorial plane as the boundary, satisfy the relationship Gi<Go and 1.1≦Go / Gi≦1.

3.

9. The tire according to claim 1, which is a winter tire or an all-season tire, having sipes extending in the tire width direction in each of the land portions.

10. The tire according to claim 9, wherein the sipes are arranged parallel to the extending direction of the lug grooves provided in the respective land portions.

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