tire

Abstract

To improve performance on snow and wet surfaces without impairing performance on ice. [Solution] The tread portion (2) includes a pair of circumferential grooves that extend along the tire circumferential direction and are adjacent in the tire width direction, land portions (20) defined between each of the circumferential grooves, a plurality of lug grooves (41) that extend along the tire width direction in the land portions (20) and that communicate with the circumferential grooves at least one end of which is aligned in the tire circumferential direction, and a plurality of sipes that extend along the tire width direction between each of the lug grooves (41) and that are aligned in the tire circumferential direction in the land portions (20). The sipes have two or more types of widths, and include a wide sipe (43) that is the widest and is positioned adjacent to at least one of the lug grooves (41) between each of the lug grooves (41). In a cross section intersecting the extension direction of the wide sipe (43), an opening (43c) side approaches the adjacent lug groove (41) and a bottom (43d) side moves away from the adjacent lug groove (41), and a straight line (Ss) connecting the opening (43c) and the bottom (43d) is inclined with respect to a normal (S) of the opening (43c) to the tread contact surface (2B).

Description

[Technical Field]

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

[0002] For example, the tire described in Patent Document 1 aims to improve performance on snow and ice by suppressing snow clogging in the sipes. This tire includes central sipes located on the center side of the blocks and outer sipes located outward of the central sipes, and in a cross section perpendicular to the longitudinal direction of the sipes, the angle of the outer sipes relative to the normal to the tread surface is larger than the angle of the central sipe relative to the normal, and the outer sipes are inclined outward from the center side of the blocks toward the outside in the tire radial direction. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-108985 Summary of the Invention [Problem to be solved by the invention]

[0004] While studless tires have traditionally been focused on performance on ice, improved performance on snow is also being sought. Generally, improving performance on ice requires improving adhesion friction. To achieve this, methods such as reducing the groove area ratio are used to increase the actual contact area, but this method has the drawback of worsening performance on snow and wet surfaces. Furthermore, studless tires use tread rubber with a relatively low hardness, which makes the grooves prone to collapse, resulting in reduced shear strength and drainage in snow.

[0005] An object of the present invention is to provide a tire that can improve performance on snow and wet conditions without impairing performance on ice. [Means for solving the problem]

[0006] In order to achieve the above object, a tire according to one embodiment of the present invention includes, in a tread portion, a pair of circumferential grooves formed in a straight line along the tire circumferential direction and adjacent in the tire width direction, land portions partitioned between the circumferential grooves, lug grooves in the land portions, at least one end of which extending along the tire width direction communicates with the circumferential groove and arranged in a row in the tire circumferential direction, and sipes in the land portions, extending along the tire width direction between each of the lug grooves adjacent in the tire circumferential direction and arranged in a row in the tire circumferential direction, the sipes having two or more types of different widths, including a wide sipe that is the widest between each of the lug grooves adjacent in the tire circumferential direction and arranged adjacent to at least one of the lug grooves, and the wide sipes are arranged such that, in a cross section intersecting the extension direction of the wide sipes, the opening side is closer to the adjacent lug groove and the bottom side is farther away from the adjacent lug groove, and the straight line connecting the opening and the bottom is inclined with respect to the normal to the tread surface of the opening. [Effects of the Invention]

[0007] According to the present invention, it is possible to improve performance on snow and wet surfaces without impairing performance on ice. [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 partially enlarged plan view of the tread of the pneumatic tire according to the embodiment. [Figure 3] FIG. 3 is a partial cross-sectional view of a pneumatic tire according to an embodiment. [Figure 4] FIG. 4 is a partial cross-sectional view showing the operation of the pneumatic tire according to the embodiment. [Figure 5] FIG. 5 is a partial cross-sectional view showing the operation of a typical pneumatic tire. [Figure 6] FIG. 6 is a cross-sectional view showing the shape of the bottom of a wide sipe. [Figure 7]FIG. 7 is a cross-sectional view showing another example of the bottom shape of the wide sipe. [Figure 8] FIG. 8 is a cross-sectional view showing another example of the bottom shape of the wide sipe. [Figure 9] FIG. 9 is a partially enlarged plan view of another example of the tread of the pneumatic tire according to the embodiment. [Figure 10] FIG. 10 is a partially enlarged plan view of another example of the tread of the pneumatic tire according to the embodiment. [Figure 11] FIG. 11 is a table showing the results of a performance test of the pneumatic tire according to the embodiment. [Figure 12] FIG. 12 is a table showing the results of a performance test of the pneumatic tire according to the embodiment. [Figure 13] FIG. 13 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 (also called a tread) 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 (cap rubber) where the tread rubber 2A comes into contact with the road surface when a vehicle (not shown) equipped with the pneumatic tire 1 is running, is formed as the tread contact surface (also referred to as the tread surface) 2B. The tread contact surface 2B forms part of the contour of the pneumatic tire 1.

[0013] The sidewall portions 8 are disposed on both sides in the tire width direction of the tread portion 2. 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 (width) is measured as the maximum distance between opposing groove walls at the 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 addition, when the groove opening has a notch or chamfer, the groove width (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 tire radial direction.

[0024] The groove depth (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. In addition, if the groove has partial unevenness or sipes at the groove bottom, the groove depth (depth) is measured excluding these.

[0025] As shown in Fig. 1, the pneumatic tire 1 of the embodiment includes a tread pattern having circumferential grooves 30. The circumferential grooves 30 include a center circumferential groove 31 and shoulder circumferential grooves 32. Each of the circumferential grooves 31, 32 may be a main groove that is required 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. In this embodiment, two center circumferential grooves 31 are provided in parallel in the tire width direction with the tire equatorial plane CL sandwiched therebetween. The center circumferential groove 31 is formed in a straight line without any bends along the tire circumferential direction. The center circumferential groove 31 has a maximum groove width 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 of 7.0 mm or more and 10.0 mm or less.

[0027] The shoulder circumferential grooves 32 extend along the tire circumferential direction and have an annular structure provided continuously around the entire tire circumference. In this embodiment, 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 a straight line along the tire circumferential direction without any bends. The shoulder circumferential grooves 32 have a maximum groove width 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 of 7.0 mm or more and 10.0 mm or less.

[0028] The number of circumferential grooves 31, 32 is not limited to the above.

[0029] In the pneumatic tire 1 of the embodiment, a plurality of land portions 20 are defined in the tread portion 2 by a plurality of circumferential grooves 31, 32. In the embodiment, the land portion 20 includes a center land portion 21, a middle land portion 22, and a shoulder land portion 23. The center land portion 21 is formed between two center circumferential grooves 31 in a 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 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 outer side of each shoulder circumferential groove 32 in the tire width direction, 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.

[0030] Here, the ground contact edges 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.

[0031] 2, in the pneumatic tire 1 of the embodiment, lug grooves 41 and sipes 42, 43, 42 are provided in at least one land portion 20 between adjacent circumferential grooves 30 in the tire width direction. In the embodiment, the spaces between adjacent circumferential grooves 30 in the tire width direction include a shoulder circumferential groove 32 and a center circumferential groove 31, or a space between a pair of center circumferential grooves 31.

[0032] The lug grooves 41 are formed in the land portion 20 to extend along the tire width direction, and a plurality of them are arranged side by side in the tire circumferential direction. At least one end of the lug grooves 41 communicates with the circumferential groove 30. That is, the lug grooves 41 include a configuration in which one end communicates with one circumferential groove 30 and the other end terminates in the land portion 20 in the land portion 20, and a configuration in which each end communicates with a circumferential groove 30. In the embodiment, FIG. 2 shows a configuration in which one end 41a of the lug groove 41 communicates with one circumferential groove 30 in the land portion 20 and the other end 41b terminates in the land portion 20. The lug grooves 41 have a groove width Wr shown in FIG. 2 of 1.5 mm or more and 10.0 mm or less, and a groove depth Dr shown in FIG. 3 of 5.0 mm or more and 10.0 mm or less. 2, the lug grooves 41 are formed to extend linearly, with the groove width Wr being the widest at one end 41a and gradually narrowing toward the other end 41b. Note that the lug grooves 41 are not limited to being linear, and may be bent or curved.

[0033] The circumferential grooves 30, to which one ends of the lug grooves 41 are connected, have groove walls 30a formed between the connecting lug grooves 41 so as to be inclined with respect to the tire circumferential direction. Each groove wall 30a is formed so as to be inclined in the same direction with respect to the tire circumferential direction.

[0034] When the lug grooves 41 are configured to terminate at the land portions 20, the sipes 42 are formed to extend linearly from the other ends 41b of the lug grooves 41 and are also referred to as communicating sipes that are provided to communicate with the other circumferential grooves 30. The sipes 42 have a width of 1.5 mm or less or 0.3 mm to 1.0 mm, and a depth of 2.0 mm to 10.0 mm.

[0035] The sipes 43, 44 are provided in small land portions 20a formed by dividing the land portion 20 by the lug grooves 41 (and the sipes 42) adjacent to each other in the tire circumferential direction. The sipes 43, 44 are of two or more types with different widths.

[0036] The sipe 43 has the widest width Ws of all the sipes and is also referred to as a wide sipe. The sipe 43 has a width Ws of 0.5 mm to 1.5 mm, as shown in FIG. 2, and a depth Ds of 2.0 mm to 10.0 mm, as shown in FIG. 3. The sipe 43 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 to the sipe 43, meaning that no other grooves or sipes exist between them. As shown in FIG. 2, one end 43a of the sipe 43 communicates with the circumferential groove 30 to which the lug groove 41 communicates, and the other end 43b terminates at the land portion 20. Alternatively, the sipe 43 may have both the one end 43a and the other end 43b terminate at the land portion 20, as shown in FIG. 9.

[0037] 3, in a cross section intersecting the extension direction of the sipe 43, a straight line Ss connecting the center of the opening 43c and the center of the bottom 43d is inclined with respect to a normal line (tire radial direction) S to the tread contact surface 2B at the center of the opening 43c. Therefore, the sipe 43 is arranged such that the opening 43c side is closer to the adjacent lug groove 41 and the bottom 43d side is farther away from the adjacent lug groove 41.

[0038] Here, the direction of the groove depth Dr of the lug groove 41 adjacent to the sipe 43 (groove depth direction) is parallel to a normal (tire radial direction) to the tread contact surface 2B that passes through the center of the opening of the lug groove 41. Also, the direction of the depth Ds of the sipe 43 (depth direction) is parallel to a normal (tire radial direction) S to the tread contact surface 2B at the center of the opening 43c.

[0039] The sipe 44 is formed to be narrower than the wide sipe 43. When the sipes 43, 44 have three or more different groove widths, the sipe 44 has two or more different groove widths. The sipe 44 has a width Wsa shown in FIG. 2 of 1.0 mm or less and a depth of 2.0 mm or more and 10.0 mm or less.

[0040] The sipes 43, 44 have shapes that include a straight line, a curved line, or a zigzag line at the tread contact surface 2B. The sipes 43, 44 have shapes that include a straight line or an uneven line in the depth direction or extension direction inside the tread rubber 2A. In this embodiment, the sipe 43 has a straight line shape at the tread contact surface 2B and inside the tread rubber 2A. The sipe 44 has a zigzag line shape at the tread contact surface 2B, and has a straight line or an uneven line shape inside the tread rubber 2A.

[0041] The sipes 42, 43, 44 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.

[0042] Although not shown in the drawings, the pneumatic tire 1 has lug grooves and sipes formed in the shoulder land portions 23 defined on the tire widthwise outer side of each shoulder circumferential groove 32. The lug grooves of the shoulder land portions 23 extend in the tire width direction and are arranged in multiple rows in the tire circumferential direction. For example, one end of the lug grooves of the shoulder land portions 23 communicates with the shoulder circumferential groove 32 and the other end passes through the ground contact edge, and the groove width and groove depth are similar to those of the lug grooves 41. The sipes of the shoulder land portions 23 extend in the tire width direction and are arranged in multiple rows in the tire circumferential direction. For example, the shape of the sipes at the tread contact surface 2B includes a straight, curved, or zigzag shape, and the shape inside the tread rubber 2A includes a straight or uneven shape in the depth direction or extension direction, and the width and depth are similar to those of the sipes 44.

[0043] Furthermore, as shown in FIG. 10 , the pneumatic tire 1 may have a narrow groove 51 in the tread contact surface 2B. The narrow groove 51 is formed to be narrower and shallower than the circumferential groove 30, the lug groove 41, and the sipes 42, 43, and 44, for example, having a width of 0.4 mm or less and a depth of 0.3 mm or less. The narrow groove 51 is disposed extending in a direction intersecting the direction in which the circumferential groove 30, the lug groove 41, and the sipes 42, 43, and 44 extend. The narrow groove 51 may be connected to the circumferential groove 30, the lug groove 41, and the sipes 42, 43, and 44, or may terminate at the tread contact surface 2B of the land portion 20 without being connected to the circumferential groove 30, the lug groove 41, and the sipes 42, 43, and 44. While the narrow groove 51 is shown in FIG. 10 as having a zigzag shape that bends midway, it may also be formed to be straight or curved midway. The narrow groove 51 shown in Figure 10 is arranged in a form in which one end 43a of the sipe 43 is connected to the circumferential groove 30 and the other end 43b terminates at the land portion 20, but it may also be arranged in a form in which one end 43a and the other end 43b of the sipe 43 terminate at the land portion 20 as shown in Figure 9.

[0044] 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.

[0045] Furthermore, when traveling on a wet road surface, water between the tread contact surface 2B and the road surface enters the grooves 30, 41 and the sipes 42, 43, 44, and the water between the tread contact surface 2B and the road surface is drained while traveling. This makes it easier for the tread contact surface 2B to make contact with the road surface, and the friction between the tread contact surface 2B and the road surface provides wet performance, enabling the vehicle to travel.

[0046] Furthermore, when traveling on snowy roads, the pneumatic tire 1 compacts snow on the road surface with the tread contact surface 2B, and the snow on the road surface also compacts within the grooves 30, 41 as it seeps into them. 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, 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.

[0047] Furthermore, when traveling on snowy or icy roads, the tire also utilizes the edge effect of the grooves 30, 41 and sipes 42, 43, 44. That is, when traveling on snowy or icy roads, the tire also utilizes the resistance created by the edges of the grooves 30, 41 and sipes 42, 43, 44 catching on the snow or ice surface. When traveling on icy roads, the sipes 42, 43, 44 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. As a result, the frictional force and edge effect of the tread contact surface 2B increase the resistance between the icy road surface and the icy road surface, thereby providing ice performance. This allows the vehicle to travel on icy roads.

[0048] The grooves 30, 41 and sipes 42, 43, 44 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 30, 41, 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.

[0049] 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 30, 41 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.

[0050] The pneumatic tire 1 of the embodiment is characterized in that it comprises, in a tread portion 2, a pair of circumferential grooves 30 formed linearly along the tire circumferential direction and adjacent to each other in the tire width direction, land portions 20 defined between the circumferential grooves 30, lug grooves 41 provided in a row in the tire circumferential direction in the land portions 20, with at least one end 41a extending along the tire width direction in the land portions 20 communicating with the circumferential grooves 30, and sipes 43, 44 provided in a row in the tire circumferential direction in the land portions 20, extending along the tire width direction between the lug grooves 41 adjacent to each other in the tire circumferential direction. The sipes 43, 44 have two or more types of different widths, and include a wide sipe 43 which is the widest and is arranged adjacent to at least one of the lug grooves 41 between adjacent lug grooves 41 in the tire circumferential direction, and the wide sipe 43 is arranged such that, in a cross section intersecting the direction in which it extends, the opening 43c side is closer to the adjacent lug groove 41 and the bottom 43d side is farther away from the adjacent lug groove 41, and the straight line Ss connecting the opening 43c and the bottom 43d is inclined with respect to the normal S of the opening 43c to the tread contact surface 2B.

[0051] In studless tires, the tread rubber 2A is a rubber with a relatively low hardness, so the lug grooves 41 are easily crushed during braking and driving, which can reduce the original functions of the lug grooves 41, i.e., shear force in snow and drainage performance, resulting in a decrease in snow performance and wet performance. As shown in Figure 5, when a relatively narrow sipe 44 is placed adjacent to the lug groove 41, the sipe 44 will be crushed first, which can cause the above phenomenon.

[0052] In this regard, according to the pneumatic tire 1, by arranging wide sipes 43 adjacent to the lug grooves 41, as shown in Fig. 4, the wide sipes 43 intentionally become locations that are easily crushed during braking and driving, and function to prevent the lug grooves 41 from collapsing, thereby improving the shear force in snow and drainage performance of the lug grooves 41, and improving performance on snow and wet tires. In other words, since the wide sipes 43 are wider than the other sipes 44, they close and collapse over a large area during braking and driving, and by suppressing deformation around them, they function to prevent the lug grooves 41 from collapsing.

[0053] Furthermore, in the pneumatic tire 1 of the embodiment, if all the sipes in the land portion 20 were wide sipes 43, the contact area would be reduced, which would decrease the adhesive friction force and reduce performance on ice, and the rigidity of the land portion 20 would also be reduced, reducing wear resistance. In this regard, in the pneumatic tire 1 of the embodiment, the sipes 43, 44 have two or more types with different widths, thereby ensuring performance on ice.

[0054] In particular, according to the pneumatic tire 1 of the embodiment, the wide sipes 43 are arranged in a cross section intersecting the direction in which they extend such that the opening 43c side is closer to the adjacent lug groove 41 and the bottom 43d side is farther away from the adjacent lug groove 41. Therefore, in the pneumatic tire 1 of the embodiment, the opening 43c side of the wide sipe 43 is intentionally made to be a location where the wide sipe 43 is more likely to collapse during braking and driving, while the volume of rubber between the wide sipe 43 and the lug groove 41 on the bottom 43d side of the wide sipe 43 is increased to ensure rigidity around the lug groove 41, and the shape of the lug groove 41 is maintained, thereby further improving on-snow performance and wet performance.

[0055] As a result, the pneumatic tire 1 can improve its performance on snow and wet surfaces without impairing its performance on ice.

[0056] In the embodiment of the pneumatic tire 1, the wide sipes 43 are arranged adjacent to only one side of the lug groove 41 in the tire circumferential direction, but the wide sipes 43 may also be arranged adjacent to the other side of the lug groove 41 in the tire circumferential direction, and the same effect can be obtained.

[0057] In addition, in the pneumatic tire 1 of the embodiment, the angle θ between the straight line Ss connecting the opening 43c and the bottom 43d and the normal S of the opening 43c to the tread contact surface 2B is in the range of 0[°]<θ≦10[°].

[0058] In this pneumatic tire 1, if the angle θ exceeds 10°, the wide sipes 43 tend to interfere with other sipes 44, making it difficult to maintain the 0° STI (0° STI) required for the number of sipes 44 to ensure snow performance. Furthermore, in this pneumatic tire 1, if the angle θ exceeds 10°, the openings of the wide sipes 43 after wear become farther from the lug grooves 41 as the tread contact surface 2B wears, making it difficult for the wide sipes 43 to become areas prone to intentional crushing during braking and driving. For this reason, the angle θ between the straight line Ss of the wide sipe 43 and the normal line S is set within the above range. The angle θ of the wide sipes 43 is preferably set within the range of 3°≦θ≦6° to maintain the 0° STI and ensure areas prone to crushing even after wear.

[0059] Here, 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 of the groove length [mm] of all grooves (all grooves excluding sipes) projected in the tire circumferential direction 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.

[0060] STI=-6.8+2202×ρg+672×ρs+7.6×Dg (1)

[0061] In the pneumatic tire 1 of the embodiment, it is desirable that the snow traction index in the 0[°] direction (0[°] STI) is 100 or more.

[0062] 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.

[0063] In the pneumatic tire 1 of the embodiment, the width Ws of the wide sipe 43 and the width Wsa of the other sipes 44 satisfy the relationship 1.1≦Ws / Wsa≦4.0.

[0064] In this pneumatic tire 1, if Ws / Wsa is less than 1.1, it becomes difficult to obtain the effect of preventing the lug grooves 41 from being crushed. In addition, in this pneumatic tire 1, 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 1 can significantly obtain the effect of improving performance on snow and wet without impairing performance on ice.

[0065] In the pneumatic tire 1 of the embodiment, the groove depth Dr of the lug grooves 41 and the depth Ds of the wide sipes 43 adjacent to each other satisfy the relationship 0.3≦Ds / Dr≦1.0.

[0066] In this pneumatic tire 1, if Ds / Dr is less than 0.3, the rigidity of the land portions 20 tends to increase and the ability to crush the sipes 43 tends to decrease, making it difficult to achieve the effect of improving snow performance and wet performance. Also, in this pneumatic tire 1, if Ds / Dr is more than 1.0, the rigidity of the land portions 20 tends to decrease and performance on ice tends to decrease. Therefore, by setting Ds / Dr in the above range, this pneumatic tire 1 can significantly achieve the effect of improving snow performance and wet performance without impairing performance on ice.

[0067] In addition, in the pneumatic tire 1 of the embodiment, the distance Bs between adjacent lug grooves 41 and wide sipes 43 and the circumferential length B of the land portion 20 between adjacent lug grooves 41 in the circumferential direction of the tire satisfy the relationship 0.08≦Bs / B≦0.4.

[0068] The distance Bs between the lug groove 41 and the wide sipe 43 is the distance between the center lines of both the lug groove 41 and the wide sipe 43. The center line is a straight line connecting the centers of both ends of the lug groove 41 and the wide sipe 43.

[0069] In this pneumatic tire 1, if Bs / B is less than 0.08, the rigidity of the land portions 20 decreases, tending to degrade on-ice performance. Furthermore, in this pneumatic tire 1, if Bs / B exceeds 0.4, the rigidity of the land portions 20 increases, tending to reduce the ability to crush the wide sipes 43, making it difficult to achieve the effect of improving snow performance and wet performance. Therefore, by setting Bs / B within the above range, this pneumatic tire 1 can achieve a significant effect of improving snow performance and wet performance without compromising on-ice performance. It is desirable that the relationship Bs / B, i.e., the distance Bs between the lug grooves 41 and the wide sipes 43, be in the range of 0.12≦Bs / B≦0.4 in order to achieve a more significant effect of improving snow performance and wet performance without compromising on-ice performance.

[0070] In order to achieve the above-described effect, it is preferable that the distance Bs between the lug grooves 41 and the wide sipes 43 be in the range of 2.5 mm to 10.0 mm. In the pneumatic tire 1 of the embodiment, if the distance Bs is less than 2.5 mm, the tread rubber 2A between them becomes thin and tends to chip easily. In addition, in the pneumatic tire 1 of the embodiment, if the distance Bs exceeds 10.0 mm, the tread rubber 2A between them becomes thick, which tends to reduce the function of the wide sipes 43 in preventing the lug grooves 41 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 and the wide sipes 43 in the above-described range, the pneumatic tire 1 significantly achieves the effect of improving snow performance and wet performance and can also prevent chipping of the land portion 20.

[0071] In the pneumatic tire 1 of the embodiment, the distance Bs between the lug groove 41 and the wide sipe 43 adjacent to each other and the groove width Wr of the lug groove 41 satisfy the relationship 0.8≦Bs / Wr≦3.0.

[0072] In this pneumatic tire 1, if Bs / Wr is less than 0.8, the rigidity of the land portions 20 decreases, tending to result in poor on-ice performance. Also, in this pneumatic tire 1, if Bs / Wr exceeds 3.0, the rigidity of the land portions 20 increases, tending to reduce the ability to crush the sipes 43, making it difficult to achieve the effect of improving on-snow performance and wet performance. Therefore, by setting Bs / Wr in the above range, this pneumatic tire 1 can achieve a significant effect of improving on-snow performance and wet performance without impairing on-ice performance.

[0073] In the pneumatic tire 1 of the embodiment, the length Lr of the lug grooves 41 and the length Ls of the wide sipes 43 adjacent to each other satisfy the relationship 0.5≦Ls / Lr≦0.9.

[0074] In this pneumatic tire 1, if Ls / Lr is less than 0.5, the rigidity of the land portions 20 increases, which tends to reduce the ability to crush the sipes 43, making it difficult to achieve the effect of improving snow performance and wet performance. Also, in this pneumatic tire 1, if Ls / Lr exceeds 0.9, the rigidity of the land portions 20 decreases, which tends to reduce performance on ice. Therefore, by setting Ls / Lr in the above range, this pneumatic tire 1 can significantly achieve the effect of improving snow performance and wet performance without impairing performance on ice.

[0075] 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.

[0076] The hardness is rubber hardness indicated by JIS-A hardness in accordance with JIS-K6253 under the condition of 20°C.

[0077] According to this pneumatic tire 1, by setting the hardness of the tread rubber 2A in the range of 40 to 70, the rigidity of the land portion 20 that can crush the sipes 43 can be ensured, and the snow performance and wet performance can be further improved. In the pneumatic tire 1 of the embodiment, when the hardness of the tread rubber 2A is in the range of 40 to 55, it is suitable for a studless tire, and when the hardness of the tread rubber 2A is in the range of 55 to 70, it is suitable for an all-season tire.

[0078] In the pneumatic tire 1 of the embodiment, the tread portion 2 has a groove area ratio of the tread pattern in the range of 20% to 40%.

[0079] 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 tread contact surface 2B. 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.

[0080] According to this pneumatic tire 1, 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.

[0081] In the pneumatic tire 1 of the embodiment, the wide sipe 43 has a depth Ds that is constant or gradually changes in the length direction, or has a bottom portion 43e on the bottom portion 43d.

[0082] "The depth Ds is constant in the length direction" means that the depth Ds from the opening 43c to the bottom 43d does not change in the length direction (between one end 43a and the other end 43b), as shown in FIG. 6. "The depth Ds gradually changes in the length direction" means that the bottom 43d is inclined in the length direction (between one end 43a and the other end 43b) with respect to the length direction, so that the depth Ds of the wide sipe 43 gradually changes, as shown in FIG. 7. "The bottom 43d of the wide sipe 43 has an upper bottom portion 43e" means that the bottom 43d protrudes outward in the tire radial direction midway in the length direction (between one end 43a and the other end 43b), so that the depth Ds suddenly becomes shallow, as shown in FIG. 8. The depth Ds of the upper bottom portion 43e may be either constant or gradually changing in the length direction.

[0083] According to this pneumatic tire 1, various bottom shapes of the wide sipes 43 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 this pneumatic tire 1 is constant in the length direction, since this has a significant effect on the lug grooves 41.

[0084] In the pneumatic tire 1 of the embodiment, the wide sipes 43 are arranged to extend along the direction in which the lug grooves 41 adjacent to each other extend.

[0085] The adjacent lug grooves 41 and wide sipes 43 are inclined in the same direction relative to the tire width direction, and the difference in inclination angle between the adjacent lug grooves 41 and wide sipes 43 extending in the same direction (θs-θr: absolute value) is within a range of 10°. The adjacent lug grooves 41 and wide sipes 43 are preferably parallel to each other. This pneumatic tire 1 improves the crushing effect of the sipes 43, making it easier to obtain the effect of improving performance on snow and wet surfaces. Note that it is preferable that all of the lug grooves 41 and wide sipes 43 arranged in one land portion 20 are inclined in the same direction relative to the tire width direction.

[0086] 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]

[0087] 11 to 13 are tables showing the results of performance tests of pneumatic tires according to the embodiment. Performance evaluation tests conducted on a conventional pneumatic tire, a comparative example 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, and wet performance.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] 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.

[0092] The conventional pneumatic tire has a pair of circumferential grooves, a lug groove communicating with one of the circumferential grooves, and a sipe in the tread portion, but the sipes are of the same type and have the same width, and these sipes are placed in place of the wide sipes in the embodiment.

[0093] The comparative example pneumatic tire has a tread portion including a pair of circumferential grooves, lug grooves communicating with one of the circumferential grooves, and sipes, the sipes having two or more types of different widths, and including a wide sipe that is the widest between adjacent lug grooves in the tire circumferential direction and is adjacent to one of the lug grooves. However, in the comparative example pneumatic tire, the wide sipe is arranged such that, in a cross section intersecting the extension direction of the sipe, the opening side is away from the adjacent lug groove and the bottom side is close to the adjacent lug groove, and the straight line connecting the opening and bottom is inclined with respect to the normal to the tread surface of the opening.

[0094] As shown in Fig. 2, the pneumatic tire of the example has a pair of circumferential grooves, lug grooves communicating with one of the circumferential grooves, and sipes, the sipes having two or more types of different widths, including a wide sipe that is the widest between adjacent lug grooves in the tire circumferential direction and is arranged adjacent to one of the lug grooves. As shown in Fig. 3, the pneumatic tire of the example has the wide sipes arranged such that, in a cross section intersecting the extension direction of the sipes, the opening side is closer to the adjacent lug groove and the bottom side is farther away from the adjacent lug groove, and the straight line connecting the opening and bottom is inclined with respect to the normal to the tread surface of the opening.

[0095] As shown in the test results, the pneumatic tire of this example has improved ice performance, snow performance, and wet performance compared to the conventional example and comparative example.

[0096] The present disclosure includes the following inventions. [Invention 1] In the tread area, a pair of circumferential grooves formed linearly along the tire circumferential direction and adjacent to each other in the tire width direction; land portions defined between the circumferential grooves; lug grooves arranged side by side in the tire circumferential direction in the land portion, at least one end of which extends along the tire width direction and communicates with the circumferential groove; a plurality of sipes extending along the tire width direction between the lug grooves adjacent to each other in the tire circumferential direction in the land portion and arranged side by side in the tire circumferential direction; Including, The sipes have two or more types of widths different from each other, and include a wide sipe having the widest width and arranged adjacent to at least one of the lug grooves between the lug grooves adjacent to each other in the tire circumferential direction, The wide sipe is arranged such that, in a cross section intersecting the direction in which the sipe extends, an opening side approaches the adjacent lug groove and a bottom side moves away from the adjacent lug groove, and a straight line connecting the opening and the bottom is inclined with respect to a normal line of the opening to the tread surface. tire. [Invention 2] The wide sipe has an angle θ between a straight line connecting the opening and the bottom and a normal line of the opening to the tread surface in the range of 0 [°] < θ ≦ 10 [°]. A tire according to claim 1. [Invention 3] The width Ws of the wide sipe and the width Wsa of the other sipes satisfy the relationship 1.1≦Ws / Wsa≦4.0. The tire according to claim 1 or 2. [Invention 4] a depth Dr of the openings of the lug grooves adjacent to each other along a normal to the tread surface and a depth Ds of the openings of the wide sipes along a normal to the tread surface satisfy the relationship 0.3≦Ds / Dr≦1.0, A tire according to any one of inventions 1 to 3. [Invention 5] 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 each lug groove satisfy the relationship 0.08≦Bs / B≦0.4; A tire according to any one of inventions 1 to 4. [Invention 6] The length Lr of the lug grooves adjacent to each other and the length Ls of the wide sipes satisfy the relationship of 0.5≦Ls / Lr≦0.9. A tire according to any one of inventions 1 to 5. [Invention 7] The tread portion has a tread rubber hardness in the range of 40 or more and 70 or less. A tire according to any one of inventions 1 to 6. [Invention 8] The tread portion has a groove area ratio of a tread pattern in the range of 20% to 40%. A tire according to any one of inventions 1 to 7. [Invention 9] The wide sipe has a constant or gradually varying depth in the length direction, or has a bottom portion at the bottom. A tire according to any one of inventions 1 to 8. [Explanation of symbols]

[0097] 1. Pneumatic tires (tires) 2 Tread section 2A Tread rubber 2B Tread contact surface (tread surface) 20 Land 30 Circumferential groove 41 Lug groove 41a one end 41b other end 43c opening 43d bottom 43e bottom top 43 Wide sipes 44 sipes

Claims

1. In the tread area, a pair of circumferential grooves formed linearly along the tire circumferential direction and adjacent to each other in the tire width direction; land portions defined between the circumferential grooves; lug grooves arranged side by side in the tire circumferential direction in the land portion, at least one end of which extends along the tire width direction and communicates with the circumferential groove; a plurality of sipes extending along the tire width direction between the lug grooves adjacent to each other in the tire circumferential direction in the land portion and arranged side by side in the tire circumferential direction; Including, The sipes have two or more types of widths different from each other, and include a wide sipe having the widest width and arranged adjacent to at least one of the lug grooves between the lug grooves adjacent to each other in the tire circumferential direction, The wide sipe is arranged such that, in a cross section intersecting the direction in which the sipe extends, an opening side approaches the adjacent lug groove and a bottom side moves away from the adjacent lug groove, and a straight line connecting the opening and the bottom is inclined with respect to a normal line of the opening to the tread surface. tire.

2. The wide sipe has an angle θ between a straight line connecting the opening and the bottom and a normal line of the opening to the tread surface in the range of 0 [°] < θ ≦ 10 [°].

2. The tire of claim 1.

3. a width Ws of the wide sipe and a width Wsa of the other sipes satisfy the relationship 1.1≦Ws / Wsa≦4.0; 2. The tire of claim 1.

4. a depth Dr of an opening of the lug grooves adjacent to each other along a normal line to the tread surface and a depth Ds of an opening of the wide sipe along a normal line to the tread surface satisfy a relationship of 0.3≦Ds / Dr≦1.0; 2. The tire of claim 1.

5. a distance Bs between the lug groove and the wide sipe adjacent to each other and a length B of the land portion between each lug groove in the tire circumferential direction satisfy the relationship 0.08≦Bs / B≦0.4; 2. The tire of claim 1.

6. The length Lr of the lug grooves adjacent to each other and the length Ls of the wide sipes satisfy the relationship 0.5≦Ls / Lr≦0.

9.

2. The tire of claim 1.

7. 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.

8. The tread portion has a groove area ratio of a tread pattern in the range of 20% to 40%.

2. The tire of claim 1.

9. The wide sipe has a constant or gradually varying depth in the length direction, or has a bottom portion at the bottom.

2. The tire of claim 1.

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