Tire

Abstract

To provide a tire capable of achieving both wet performance and wear resistance performance of the tire.SOLUTION: The tire 1 includes a plurality of circumferential main grooves 21 to 24 and a plurality of land portions 31 to 35 defined by the plurality of circumferential main grooves 21 to 24. Additionally, the inner middle land portion 32 and the center land portion 33 include the plurality of bent sipes 4A to 4C having a bent shape. Additionally, the bent sipes 4A to 4C are formed by connecting the width-direction portions 41 that extend in the tire lateral direction and connect to the edge portions of the land portions 32, 33, and the circumferential-direction portions 42 that extend in the tire circumferential direction and terminate within the land portions 32, 33. The extending length L41 of the widthwise portion 41 in the tire widthwise direction is in the range of 0.55 ≤ Wb2 / Wb ≤ 0.85 with respect to the ground contact widths Wb (Wb3; L41) of the land portions 32; 33.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a tire, and more particularly to a tire that can achieve both wet performance and wear resistance. [Background technology]

[0002] Recently, there has been a need to improve the wet performance of tires. A conventional tire that addresses this issue is disclosed in Patent Document 1. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-124713 A Summary of the Invention [Problem to be solved by the invention]

[0004] Furthermore, there is also a need to improve the wear resistance of recent tires.

[0005] The present invention has been made in view of the above, and has an object to provide a tire that can achieve both wet performance and wear resistance. [Means for solving the problem]

[0006] In order to achieve the above object, the tire of the present invention is a tire comprising a plurality of circumferential main grooves and a plurality of land portions defined by the plurality of circumferential main grooves, wherein at least one of the plurality of land portions comprises a plurality of bent sipes having a bent shape, the bent sipes connecting a widthwise portion extending in the tire width direction and connecting to an edge portion of the land portion, and a circumferential portion extending in the tire circumferential direction and terminating inside the land portion, and wherein an extension length L41 of the widthwise portion in the tire width direction is in the range of 0.55≦L41 / Wb≦0.85 with respect to a contact patch width Wb of the land portion. [Effects of the Invention]

[0007] In the tire according to the present invention, the land portions include a plurality of bent sipes having a bent shape, and the edge effect and drainage effect of the bent sipes improve the wet performance of the tire. Furthermore, the widthwise portions of the bent sipes are connected to the edge portions of the land portions, thereby ensuring the drainage effect of the bent sipes. Meanwhile, the circumferential portions of the bent sipes terminate inside the land portions, ensuring the rigidity of the land portions, improving the tire's wear resistance and reducing tire pattern noise. Furthermore, the lower limit of the ratio L41 / Wb ensures the extension length L41 of the widthwise portions, ensuring the drainage effect of the bent sipes, while the upper limit ensures the rigidity of the land portions, ensuring the effect of improving the tire's wear resistance. These advantages result in a tire that achieves both good wet performance and good wear resistance. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view in the tire meridian direction showing a tire according to an embodiment of the present invention. [Figure 2] FIG. 2 is a plan view showing the tread surface of the tire shown in FIG. [Figure 3] FIG. 3 is an enlarged view showing the inner middle land portion and the center land portion shown in FIG. [Figure 4] FIG. 4 is an enlarged view showing the bent sipes in the center land portion shown in FIG. [Figure 5] FIG. 5 is a cross-sectional view showing the bent sipe shown in FIG. [Figure 6] FIG. 6 is an enlarged view showing the bent sipe and the notch portion of the inner middle land portion shown in FIG. [Figure 7] FIG. 7 is a table showing the results of performance tests on the tire according to the embodiment of the present invention. [Figure 8] FIG. 8 is a table showing the results of performance tests on the tire according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention will be described in detail below 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] [tire] 1 is a cross-sectional view in the tire meridian direction showing a tire 1 according to an embodiment of the present invention. The figure shows a cross-sectional view of one side region in the tire radial direction. In this embodiment, a pneumatic radial tire for passenger cars will be described as an example of a tire.

[0011] In the figure, the tire meridian cross section is defined as a cross section of the tire cut by a plane including the tire rotation axis (not shown). The tire equatorial plane CL is defined as a plane that passes through the midpoint of the tire section width defined by JATMA and is perpendicular to the tire rotation axis. The tire width direction is defined as the direction parallel to the tire rotation axis, and the tire radial direction is defined as the direction perpendicular to the tire rotation axis.

[0012] Additionally, the vehicle width direction inner side and vehicle width direction outer side are defined as the orientation relative to the vehicle width direction when the tire is mounted on a vehicle. Furthermore, the left and right regions bounded by the tire equatorial plane are defined as the vehicle width direction outer side region and the vehicle width direction inner side region, respectively. Furthermore, the tire is equipped with 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 bump on the tire sidewall. For example, ECER30 (Article 30 of the Economic Commission for Europe Regulation) requires that a vehicle mounting direction indicator be provided on the sidewall that will be on the vehicle width outer side when mounted on the vehicle.

[0013] The tire 1 has an annular structure centered on the tire rotation axis, and includes a pair of bead cores 11, 11, a pair of bead fillers 12, 12, a carcass layer 13, a belt layer 14, a tread rubber 15, a pair of sidewall rubbers 16, 16, and a pair of rim cushion rubbers 17, 17 (see Figure 1).

[0014] The pair of bead cores 11, 11 are formed by winding one or more steel bead wires in an annular and multiple pattern and are embedded in the bead portions to form the cores of the left and right bead portions. The pair of bead fillers 12, 12 are disposed on the outer periphery of the pair of bead cores 11, 11 in the tire radial direction, respectively, to reinforce the bead portions.

[0015] 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, and is toroidally laid between the left and right bead cores 11, 11 to form the tire framework. Both ends of the carcass layer 13 are wrapped around and secured to the outside in the tire width direction so as to enclose the bead cores 11 and the bead fillers 12. The carcass ply of the carcass layer 13 is formed by covering multiple carcass cords made of steel or organic fiber material (e.g., aramid, nylon, polyester, rayon, etc.) with coating rubber and rolling them, and has a cord angle (defined as the inclination angle of the carcass cords in the longitudinal direction relative to the tire circumferential direction) of 80 degrees or more and 100 degrees or less.

[0016] The belt layer 14 is formed by laminating a plurality of belt plies 141 to 143, and is disposed by being wound around the outer periphery of the carcass layer 13. The belt plies 141 to 143 each include a pair of cross belts 141, 142 and a belt cover 143.

[0017] The pair of cross belts 141, 142 are formed by coating a plurality of belt cords made of steel or organic fiber material with coating rubber and rolling them, and have a cord angle (defined as the inclination angle of the belt cords in the longitudinal direction with respect to the tire circumferential direction) of 15 degrees or more and 55 degrees or less in absolute value. The pair of cross belts 141, 142 have cord angles of opposite signs to each other, and are layered with the longitudinal directions of the belt cords crossing each other (so-called cross-ply structure). The pair of cross belts 141, 142 are layered and arranged on the outer side of the carcass layer 13 in the tire radial direction.

[0018] The belt cover 143 is configured by covering a belt cover cord made of steel or organic fiber material with coating rubber, and has a cord angle of 0 degrees or more and 10 degrees or less in absolute value. The belt cover 143 is, for example, a strip material configured by covering one or more belt cover cords with coating rubber, and is configured by winding this strip material spirally around the outer circumferential surfaces of the cross belts 141 and 142 multiple times in the tire circumferential direction. The belt cover 143 is disposed to cover the entire area of ​​the cross belts 141 and 142.

[0019] The tread rubber 15 is disposed on the outer periphery of the carcass layer 13 and the belt layer 14 in the tire radial direction to form the tread portion of the tire 1. Made of a rubber material with excellent ground contact characteristics and weather resistance, it is exposed over the entire outer periphery of the tire to form the tread surface. A pair of sidewall rubbers 16, 16 are disposed on the outer sides of the carcass layer 13 in the tire width direction to form left and right sidewall portions. A pair of rim cushion rubbers 17, 17 extend from the inner side in the tire radial direction of the left and right bead cores 11, 11 and the turned-up portions of the carcass layer 13 to the outer side in the tire width direction to form the rim fitting surface of the bead portion.

[0020] [Tread surface] Fig. 2 is a plan view showing the tread surface of the tire 1 shown in Fig. 1. The figure shows the tread surface of a summer tire. In the figure, the tire circumferential direction refers to the direction around the tire rotation axis. Also, the symbol T indicates the tire contact edge, and the dimension symbol TW indicates the tire contact width.

[0021] As shown in FIG. 2, the tire 1 has four main grooves 21 to 24 extending in the tire circumferential direction, and five rows of land portions 31 to 35 defined by these main grooves on the tread surface.

[0022] The main grooves 21-24 are composed of a pair of shoulder main grooves 21, 24 and two center main grooves 22, 23. These main grooves 21-24 have an annular structure that extends continuously around the entire tire circumferential direction. The shoulder main grooves 21, 24 are the outermost main grooves in the tire width direction and are defined as left and right regions bounded by the tire equatorial plane CL. The shoulder main groove 21, located in the inner region in the vehicle width direction bounded by the tire equatorial plane CL, is defined as the inner shoulder main groove, and the shoulder main groove 24, located in the outer region in the vehicle width direction, is defined as the outer shoulder main groove. The center main grooves 22, 23 are defined as main grooves located closer to the tire equatorial plane CL than the shoulder main grooves 21, 24.

[0023] The main grooves are defined as grooves that are required to display a wear indicator as specified by JATMA. The main grooves 21-24 have a groove width Wg (Wg1-Wg3) of 4.0 mm or more and 15.0 mm or less, and a groove depth Hg of 6.5 mm or more and 8.6 mm or less.

[0024] The groove width is measured as the distance between the opposing groove walls at the groove opening on the tread surface 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 surface and an extension of the groove wall in a cross-sectional view parallel to the groove width direction and the groove depth direction as the endpoint.

[0025] The groove depth is measured as the distance from the tread surface 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.

[0026] A specified rim is a "standard rim" as specified by JATMA, a "design rim" as specified by TRA, or a "measuring rim" as specified by ETRTO. Also, specified internal pressure is the "maximum air pressure" as specified by JATMA, the maximum value of the "tire load limits at various cold inflation pressures" as specified by TRA, or the "inflation pressure" as specified by ETRTO. Also, specified load is the "maximum load capacity" as specified by JATMA, the maximum value of the "tire load limits at various cold inflation pressures" as specified by TRA, or the "load capacity" as specified by ETRTO. However, in JATMA, for passenger car tires, the specified internal pressure is 180 kPa, and the specified load is 88% of the maximum load capacity at the specified internal pressure.

[0027] In addition, in the configuration of FIG. 2, the distance (dimension symbols omitted in the figure) from the tire equatorial plane CL to the groove center lines of the left and right shoulder main grooves 21, 24 is in the range of 26% to 32% of the tire contact width TW.

[0028] The groove centerline is defined as an imaginary line connecting the midpoints of the distance between opposing groove walls.

[0029] The tire contact width TW is measured as the maximum linear distance in the axial direction of the tire at the contact surface between the tire and a flat plate when the tire is mounted on a specified rim, pressurized to a specified internal pressure, and placed perpendicular to a flat plate in a stationary state and subjected to a load corresponding to a specified load.

[0030] The tire ground contact edge T is defined as the widest position in the axial direction of the tire at the contact surface between the tire and a flat plate when the tire is mounted on a specified rim, pressurized to a specified internal pressure, and placed perpendicular to a flat plate in a stationary state and subjected to a load corresponding to a specified load.

[0031] The land portions 31-35 are composed of a pair of shoulder land portions 31, 35, a pair of middle land portions 32, 34, and a single row of center land portion 33. These land portions 31-35 are defined by the main grooves 21-24 and form an annular tread extending around the entire circumference of the tire. The shoulder land portions 31, 35 are defined as land portions defined by the shoulder main grooves 21, 24 on the outer side in the tire width direction. The pair of shoulder land portions 31, 35 are arranged in left and right regions bounded by the tire equatorial plane CL. The shoulder land portion 31 located in the inner region in the vehicle width direction bounded by the tire equatorial plane CL is defined as the inner shoulder main groove, and the shoulder land portion 35 located in the outer region in the vehicle width direction is defined as the outer shoulder main groove. The middle land portions 32, 34 are defined as land portions defined by the shoulder main grooves 21, 24 on the inner side in the tire width direction. A pair of middle land portions 32, 34 are disposed in left and right regions bounded by the tire equatorial plane CL. The center land portion 33 is defined as a land portion located closer to the tire equatorial plane CL than the middle land portions 32, 34.

[0032] 2, the contact width Wb2 of the inner middle land portion 32 is in the range of 8.0% to 25.0% of the tire contact width TW, and the contact width Wb3 of the center land portion 33 is in the range of 9.0% to 20.0% of the tire contact width TW.

[0033] The contact width of the land portion is measured as the maximum linear distance in the axial direction of the tire at the contact surface between the land portion and the flat plate when the tire is mounted on a specified rim, pressurized to a specified internal pressure, and placed perpendicular to a flat plate in a stationary state and subjected to a load corresponding to a specified load.

[0034] In the configuration shown in FIG. 2, the tire 1 has a pair of shoulder main grooves 21, 24 and two center main grooves 22, 23, thereby defining a pair of shoulder land portions 31, 35, a pair of middle land portions 32, 34, and a single center land portion 33. However, this is not limiting, and the tire 1 may have a single center main groove or three or more center main grooves (not shown). In the former configuration, the center land portion is omitted and the middle land portion doubles as the center land portion, while in the latter configuration, two or more rows of center land portions are defined. In addition, the center land portion 33 may be positioned on the tire equatorial plane CL (see FIG. 2), or may be positioned at a position offset from the tire equatorial plane CL (not shown).

[0035] [Flexed sipes] Fig. 3 is an enlarged view showing the inner middle land portion 32 and the center land portion 33 shown in Fig. 2. Fig. 4 is an enlarged view showing the bent sipes 4A and 4B of the center land portion 33 shown in Fig. 3. Fig. 5 is a cross-sectional view showing the bent sipe 4A shown in Fig. 4. This view shows a cross-section taken along the center line of the bent sipe 4A. Fig. 6 is an enlarged view showing the bent sipe 4C and the cutout portion 5 of the inner middle land portion 32 shown in Fig. 3.

[0036] 2 and 3, the inner middle land portion 32 and the center land portion 33 have a plurality of bent sipes 4A to 4C each having a bent shape. One end of each of these bent sipes 4A to 4C is connected to an edge portion of the land portion 32, 33, and the other end is terminated within the land portion 32, 33, forming a semi-closed structure.

[0037] Specifically, as shown in FIGS. 4 and 6, the bent sipes 4A to 4C have a bent shape formed by connecting a width direction portion 41 and a circumferential direction portion .

[0038] The widthwise portion 41 extends in the tire width direction and connects to the edge portions of the land portions 32, 33. The extension length L41 of the widthwise portion 41 in the tire width direction, relative to the contact patch width Wb (Wb2, Wb3) of the land portions 32, 33, is in the range of 0.55≦L41 / Wb≦0.85, and preferably in the range of 0.60≦L41 / Wb≦0.80.

[0039] The extension length L41 of the widthwise portion 41 is measured as the distance in the tire width direction from the connection point between the widthwise portion 41 and the circumferential portion 42, i.e., the bending point of the bent sipes 4A to 4C, to the connection point between the widthwise portion 41 and the edge portion of the land portions 32, 33.

[0040] The circumferential portion 42 extends in the tire circumferential direction and terminates inside the land portions 32, 33. The extension length L42 of the circumferential portion 42 in the tire circumferential direction, relative to the extension length L41 of the widthwise portion 41 in the tire width direction, is in the range of 0.10≦L42 / L41≦0.40, and preferably 0.15≦L42 / L41≦0.35. Therefore, the extension length L42 of the circumferential portion 42 is shorter than the extension length L41 of the widthwise portion 41.

[0041] In the above configuration, the land portions 32, 33 include a plurality of bent sipes 4A-4C having a bent shape, and the edge effect and drainage effect of the bent sipes 4A-4C improve the wet performance of the tire. Furthermore, the widthwise portions 41 of the bent sipes 4A-4C are connected to the edge portions of the land portions 32, 33, thereby ensuring the drainage effect of the bent sipes 4A-4C. Meanwhile, the circumferential portions 42 of the bent sipes 4A-4C terminate inside the land portions 32, 33, ensuring the rigidity of the land portions 32, 33, improving the tire's wear resistance and reducing tire pattern noise. Furthermore, the lower limit of the ratio L41 / Wb ensures the extension length L41 of the widthwise portions 41, ensuring the drainage effect of the bent sipes 4A-4C, while the upper limit ensures the rigidity of the land portions 32, 33, ensuring the improvement of the tire's wear resistance. These factors result in a tire that achieves both wet performance and wear resistance.

[0042] For example, in the configuration shown in Fig. 3, the curved sipes 4A to 4C extend in the tire width direction and intersect with the center lines (not shown) of the land portions 32, 33. Furthermore, as shown in Figs. 4 and 6, one end of the widthwise portion 41 of the curved sipes 4A to 4C is connected to one edge portion of the land portions 32, 33, and the circumferential portion 42 is connected to the other end of the widthwise portion 41, thereby extending the widthwise portion 41. Furthermore, the distance D4 in the tire width direction from the end portion of the curved sipes 4A to 4C in the land portions 32, 33, i.e., the end portion of the circumferential portion 42, to the other edge portion of the land portions 32, 33, is in the range of 0.01 ≦ D4 / Wb ≦ 0.30, and preferably in the range of 0.05 ≦ D4 / Wb ≦ 0.25, relative to the contact width Wb (Wb2, Wb3) of the land portions 32, 33. As a result, the bent sipes 4A to 4C terminate inside the land portions 32, 33, thereby ensuring the rigidity of the land portions 32, 33.

[0043] 4, the inclination angle θ41 of the width direction portion 41 with respect to the tire width direction is in the range of 1 [deg]≦θ41≦30 [deg], and preferably in the range of 5 [deg]≦θ41≦25 [deg]. The lower limit ensures the inclination angle θ41 of the width direction portion 41 and ensures the drainage performance of the bent sipes 4A to 4C, and the upper limit ensures the rigidity of the land portions 32, 33.

[0044] The inclination angle θ41 of the widthwise portion 41 is measured as the angle between the tire width direction and an imaginary line passing through the connection point between the widthwise portion 41 and the circumferential portion 42 and the connection point between the widthwise portion 41 and the edge portion of the land portions 32, 33.

[0045] 4, the inclination angle θ42 of the circumferential portion 42 with respect to the tire width direction is in the range of 20 degrees ≦ θ42 ≦ 70 degrees, and preferably in the range of 30 degrees ≦ θ42 ≦ 65 degrees. The lower limit ensures the inclination angle θ42 of the circumferential portion 42 and ensures the drainage performance of the bent sipes 4A to 4C, while the upper limit ensures the rigidity of the land portions 32, 33.

[0046] The inclination angle θ42 of the circumferential portion 42 is measured as the angle formed between the tire width direction and an imaginary line passing through the connection point between the width direction portion 41 and the circumferential portion 42 and the terminal end of the circumferential portion 42.

[0047] For example, in the configurations shown in FIGS. 4 and 6, the bent sipes 4A to 4C have an L-shape formed by interconnecting a widthwise portion 41 and a circumferential portion 42. The widthwise portion 41 and the circumferential portion 42 are inclined in the same direction relative to the tire width direction. Therefore, the bent sipes 4A to 4C are inclined in one direction in the tire circumferential direction from one edge portion of the land portions 32, 33 to the other edge portion. The inclination angle θ42 of the circumferential portion 42 relative to the inclination angle θ41 of the widthwise portion 41 is in the range of 20 degrees ≦ θ42 - θ41 ≦ 60 degrees, and preferably in the range of 25 degrees ≦ θ42 - θ41 ≦ 55 degrees.

[0048] In addition, in FIG. 4, the width W41 of the width direction portion 41 is in the range of 0.2 mm ≦ W41 ≦ 2.0 mm, preferably 0.5 mm ≦ W41 ≦ 1.5 mm, in the region excluding the widened portion 411 described later. In addition, in FIG. 5, the groove depth H1 of the width direction portion 41 is in the range of 0.60 ≦ H41 / Hg ≦ 0.95, preferably 0.65 ≦ H41 / Hg ≦ 0.80, in the region excluding the widened portion 411 described later, relative to the groove depth Hg of the circumferential main grooves 22, 23. The above lower limit ensures the width W41 and groove depth H1 of the width direction portion 41, thereby ensuring the drainage function of the flexed sipes 4A-4C. The above upper limit prevents a decrease in the rigidity of the land portions 32, 33 caused by the width W41 and groove depth H1 of the width direction portion 41 being excessively large. Furthermore, due to the above upper limit of the width W41 and the above lower limit of the ratio H41 / Hg, the widthwise portion 41 is closed when the tire is in contact with the ground, and the rigidity of the land portions 32, 33 is ensured.

[0049] 4 to 6, for example, the width direction portion 41 has a constant width W41 (see FIG. 4) and groove depth H41 (see FIG. 5) in an area excluding a widened portion 411 described later. The circumferential direction portion 42 has a width W42 (see FIG. 4) and groove depth H42 that are equal to or smaller than those of the width direction portion 41. Furthermore, the width W42 and groove depth H42 of the circumferential direction portion 42 monotonically decrease from the connection point with the width direction portion 41 toward the terminal end.

[0050] The widths W41, 42 of the widthwise portion 41 and the circumferential portion 42 are measured as the distance between the opposing side walls of the opening in the tread surface when the tire is mounted on a specified rim, inflated to a specified internal pressure, and in an unloaded state.

[0051] As shown in FIG. 4, the width direction portion 41 has a widened portion 411 .

[0052] The widened portion 411 is formed at the connection between the widthwise portion 41 and one edge portion of the land portion 33, and widens the width W41 of the widthwise portion 41. This improves the drainage effect of the flexed sipes 4A, 4B. The widened portion 411 may be, for example, a notch formed in the edge portion of the land portion 33, a short narrow groove opening into the edge portion of the land portion 33, or a chamfered portion connecting the widthwise portion 41 and the edge portion of the land portion 33.

[0053] Furthermore, the extension length L411 of the widened portion 411 in the tire width direction is in the range of 0.15≦L411 / L41≦0.50, and preferably 0.20≦L411 / L41≦0.45, relative to the extension length L41 of the widthwise portion 41 in the tire width direction. The lower limit ensures the extension length L411 of the widened portion 411, thereby ensuring the effect of the widened portion 411 in improving drainage. The upper limit prevents a decrease in rigidity of the land portion 33 caused by the widened portion 411 being excessively large.

[0054] The extension length L411 of the widened portion 411 is measured as the distance in the tire width direction from the widening start point of the width direction portion 41 by the widened portion 411 to the edge portion of the land portion 33.

[0055] 4, the maximum width W41_max of the widthwise portion 41 is in the range of 0.20≦W41_max / W411_max≦0.50, and preferably 0.25≦W41_max / W411_max≦0.45, relative to the maximum width W411_max of the widened portion 411. The lower limit ensures that the widened portion 411 improves drainage, while the upper limit prevents a decrease in rigidity of the land portion 33 caused by the widened portion 411 being excessively large. Furthermore, the widened portion 411 has a width of 2.0 mm or more and a depth of 3.0 mm or more, so that it opens and functions as a groove when the tire comes into contact with the ground.

[0056] The width W411 of the widened portion 411 is measured as the distance between the opposing side walls of the opening in the tread surface when the tire is mounted on a specified rim, inflated to a specified internal pressure, and in an unloaded state.

[0057] 5, the maximum depth H411 of the widened portion 411 is in the range of 0.55≦H411 / H41≦0.95, and preferably in the range of 0.60≦H41 / H41≦0.90, relative to the groove depth H41 of the widened portion 411. The lower limit ensures that the widened portion 411 improves drainage, and the upper limit prevents a decrease in the rigidity of the land portion 33 caused by the widened portion 411 being too large.

[0058] 3, for example, each of the flexed sipes 4A, 4B in the center land portion 33 has a widened portion 411 (see FIG. 4), while the flexed sipe 4C in the middle land portion 32 does not have a widened portion. In this manner, some of the flexed sipes 4A to 4C may have the widened portion 411, or all of the flexed sipes 4A to 4C may have the widened portion 411.

[0059] In the configuration shown in FIG. 3, the center land portion 33 includes a plurality of first flexed sipes 4A connected to one edge of the land portion 33 and a plurality of second flexed sipes 4B connected to the other edge of the land portion 33. The first and second flexed sipes 4A, 4B are arranged alternately in the tire circumferential direction, i.e., in a staggered pattern. The second flexed sipes 4B are arranged in the center of adjacent first flexed sipes 4A, 4A, specifically, in a range of 25% to 75% from the end point of the pitch length P4 of the first flexed sipes 4A. The adjacent first and second flexed sipes 4A, 4B are arranged spaced apart without overlapping each other when viewed in the tire width direction. This allows the flexed sipes 4A, 4B to be dispersed in the tire circumferential direction, reducing tire pattern noise.

[0060] 3, the first and second curved sipes 4A, 4B are inclined in opposite directions relative to the tire circumferential direction. Specifically, the first curved sipe 4A is inclined in one direction in the tire circumferential direction (downward in the figure) from its opening at the edge of the land portion 33 toward its terminal end within the land portion 33, and the second curved sipe 4B is inclined in the other direction in the tire circumferential direction (upward in the figure) from its opening at the edge of the land portion 33 toward its terminal end within the land portion 33. Therefore, the first and second curved sipes 4A, 4B are inclined in the same direction in the tire circumferential direction toward one direction in the tire width direction.

[0061] More specifically, as shown in Fig. 4, the width direction portion 41 and the circumferential direction portion 42 of the first curved sipe 4A are inclined in one direction in the tire circumferential direction (downward in the figure) toward the terminal end of the circumferential direction portion 42, and the width direction portion 41 and the circumferential direction portion 42 of the second curved sipe 4B are inclined in the other direction in the tire circumferential direction (upward in the figure) toward the terminal end of the circumferential direction portion 42. For this reason, as shown in Fig. 3, the circumferential direction portions 42, 42 of adjacent curved sipes 4A, 4B are inclined in mutually opposite directions in the tire circumferential direction.

[0062] In the configuration shown in FIG. 3 , the inner middle land portion 32 includes a plurality of third curved sipes 4C connected to an edge of the land portion 32 on the tire equatorial plane CL side, and a plurality of cutouts 5 connected to the other edge of the land portion 32. The third curved sipes 4C and the cutouts 5 are arranged alternately in the tire circumferential direction. The cutouts 5 are arranged in the center portions of adjacent third curved sipes 4C, 4C, specifically, in a range of 25% to 75% from the end points of the pitch length (dimension symbols omitted in the drawing) of the third curved sipes 4C. The third curved sipes 4C and the cutouts 5 are arranged spaced apart without overlapping each other when viewed in the tire width direction. This allows the third curved sipes 4C and the cutouts 5 to be dispersed in the tire circumferential direction, reducing tire pattern noise. In addition, the connection of the cutout portion 5 to the edge portion of the land portion 32 on the inner side in the vehicle width direction improves the drainage performance of the tire, and the connection of the third bent sipe 4C to the edge portion of the land portion 32 on the outer side in the vehicle width direction ensures the rigidity of the land portion 32.

[0063] 3, the third bent sipes 4C and the cutout portions 5 are inclined in opposite directions relative to the tire circumferential direction. Specifically, the third bent sipes 4C are inclined in one direction in the tire circumferential direction (downward in the figure) from their openings at the edge portions of the land portions 32 toward their terminal ends within the land portions 32, and the cutout portions 5 are inclined in the other direction in the tire circumferential direction (upward in the figure) from their openings at the edge portions of the land portions 32 toward their terminal ends within the land portions 32. Therefore, the third bent sipes 4C and the cutout portions 5 are inclined in the same direction in the tire circumferential direction toward one direction in the tire width direction.

[0064] 6, the extension length L5 of the cutout 5 in the tire width direction is in the range of 0.25≦L5 / Wb2≦0.65, and preferably 0.30≦L5 / Wb2≦0.60, relative to the contact width Wb2 of the land portion 32. The lower limit ensures the extension length L5 of the cutout 5, ensuring the effect of the cutout 5 in improving drainage. The upper limit prevents a decrease in rigidity of the land portion 32 caused by the cutout 5 being excessively large.

[0065] Furthermore, the maximum depth H5 (not shown) of the cutouts 5 is in the range of 0.30≦H5 / Hg≦0.80, and preferably 0.35≦H5 / Hg≦0.65, relative to the groove depth Hg of the circumferential main groove 21. The lower limit ensures that the cutouts 5 improve drainage, and the upper limit prevents a decrease in rigidity of the land portions 32 caused by the cutouts 5 being excessively large.

[0066] 2, the inner middle land portion 32 and the center land portion 33 are provided with multiple flexed sipes 4A-4C as described above. This configuration is preferable because the flexed sipes 4A-4C effectively improve wet performance and wear resistance. However, this is not a limitation, and multiple flexed sipes 4A-4C may be arranged in either the inner middle land portion 32 or the center land portion 33. This configuration also achieves both improved wet performance and wear resistance. Furthermore, the other land portions 31, 34, and 35 may be provided with multiple flexed sipes 4A-4C (not shown).

[0067] Furthermore, it is preferable that the land portion 33 closest to the tire equatorial plane CL among the plurality of land portions 31 to 35 has a plurality of curved sipes 4A, 4B each having a widened portion 411. For example, in the configuration of Fig. 2, the center land portion 33 on the tire equatorial plane CL has a plurality of curved sipes 4A, 4B each having a widened portion 411. This effectively improves the wet performance and wear resistance of the tire.

[0068] The land portion closest to the tire equatorial plane CL is defined as the land portion on the tire equatorial plane CL, and if there is a circumferential main groove on the tire equatorial plane CL, it is defined as at least one of the land portions partitioned by the circumferential main groove on the tire equatorial plane CL.

[0069] In the configuration shown in FIG. 2, the inner shoulder land portion 31 includes a plurality of first inner shoulder sipes 311 that penetrate the land portion 31, and a plurality of second inner shoulder sipes 312 that intersect the tire ground-contact edge T and terminate inside the land portion 31. The first and second inner shoulder sipes 311, 312 are arranged alternately in the tire circumferential direction. The cutouts 5 of the inner middle land portion 32 are also arranged on the extension lines of the plurality of first inner shoulder sipes 311. These features ensure the rigidity of the shoulder land portion 31 while improving the wet performance of the tire.

[0070] 2, the outer middle land portion 34 has multiple cutouts 341 at its edge on the tire equatorial plane CL side. The multiple cutouts 341 are located on the extensions of the first bent sipes 4A of the center land portion 33. The outer middle land portion 34 has a plain edge without grooves, sipes, or cutouts that open to the outer edge in the vehicle width direction. These features ensure the rigidity of the outer middle land portion 34.

[0071] 2, the outer shoulder land portion 35 includes multiple first outer shoulder sipes 351 that penetrate the land portion 35 and multiple second outer shoulder sipes 352 that intersect the tire ground contact edge T and terminate inside the land portion 33. The first and second outer shoulder sipes 351, 352 are arranged alternately in the tire circumferential direction. The first outer shoulder sipe 351 has a V-shape that protrudes in one direction in the tire circumferential direction, and includes a widened portion (reference numeral omitted in the figure) that connects to the edge of the land portion 35 on the tire equatorial plane CL side. These features ensure the rigidity of the shoulder land portion 35 while improving the wet performance of the tire.

[0072] [effect] As described above, [1] the tire 1 includes a plurality of circumferential main grooves 21-24 and a plurality of land portions 31-35 defined by the plurality of circumferential main grooves 21-24 (see FIGS. 1 and 2). At least one of the land portions 31-35 (the inner middle land portion 32 and the center land portion 33 in FIG. 2) includes a plurality of bent sipes 4A-4C having a bent shape. Each of the bent sipes 4A-4C connects a widthwise portion 41 extending in the tire width direction and connecting to an edge portion of the land portion 32; 33, and a circumferential portion 42 extending in the tire circumferential direction and terminating inside the land portion 32; 33 (see FIGS. 4 and 6). The extension length L41 of the widthwise portion 41 in the tire width direction, relative to the contact width Wb (Wb2; Wb3) of the land portion 32; 33, is within the range of 0.55≦L41 / Wb≦0.85.

[0073] In this configuration, the land portions 32, 33 include a plurality of bent sipes 4A-4C having a bent shape, and the edge effect and drainage effect of the bent sipes 4A-4C improve the wet performance of the tire. Furthermore, the widthwise portions 41 of the bent sipes 4A-4C are connected to the edge portions of the land portions 32, 33, thereby ensuring the drainage effect of the bent sipes 4A-4C. Meanwhile, the circumferential portions 42 of the bent sipes 4A-4C terminate inside the land portions 32, 33, thereby ensuring the rigidity of the land portions 32, 33, improving the tire's wear resistance and reducing tire pattern noise. Furthermore, the lower limit of the ratio L41 / Wb ensures the extension length L41 of the widthwise portions 41, ensuring the drainage effect of the bent sipes 4A-4C, while the upper limit ensures the rigidity of the land portions 32, 33, ensuring the improvement of the tire's wear resistance. These have the advantage of providing both good wet performance and good wear resistance for the tire.

[0074] [2] In the tire 1 described in [1] above, the extension length L42 of the circumferential portion 42 in the tire circumferential direction is in the range of 0.10≦L42 / L41≦0.40 relative to the extension length L41 of the widthwise portion 41 in the tire width direction (see FIG. 4). This has the advantage of ensuring the rigidity of the land portions 32, 33 while improving the drainage effect of the bent sipes 4A to 4C.

[0075] [3] In the tire 1 according to the above [1] or [2], the width direction portion 41 has an enlarged portion 411 at a connection portion with one edge portion of the land portion 33 (see FIG. 4). This has the advantage of improving the drainage effect of the flexed sipes 4A, 4B.

[0076] [4] In addition, in the tire 1 described in [3] above, the extension length L411 of the widened portion 411 in the tire width direction is in the range of 0.15≦L411 / L41≦0.50 relative to the extension length L41 of the widthwise portion 41 in the tire width direction (see FIG. 4). The lower limit ensures the extension length L411 of the widened portion 411, ensuring the effect of improving drainage by the widened portion 411, while the upper limit has the advantage of suppressing a decrease in rigidity of the land portion 33 caused by the widened portion 411 being excessively large.

[0077] [5] In the tire 1 described in [3] or [4] above, the maximum width W41_max of the widthwise portion 41 is in the range of 0.20≦W41_max / W411_max≦0.50 relative to the maximum width W411_max of the widened portion 411 (see FIG. 4). The lower limit ensures that the widened portion 411 improves drainage, while the upper limit has the advantage of suppressing a decrease in rigidity of the land portion 33 caused by the widened portion 411 being excessively large.

[0078] [6] The tire 1 is the tire 1 according to any one of the above [3] to [5], wherein the land portion (the center land portion 33 in FIG. 2) closest to the tire equatorial plane CL among the plurality of land portions 31 to 35 includes a plurality of bent sipes 4A, 4B (see FIG. 2) each having a widened portion 411 (see FIG. 4). This has the advantage of effectively improving the wet performance and wear resistance of the tire.

[0079] [7] In the tire 1 according to any one of the above [1] to [6], the width direction portion 41 and the circumferential direction portion 42 are inclined in the same direction with respect to the tire width direction (see FIGS. 4 and 6). This has the advantage of effectively improving the wet performance of the tire.

[0080] [8] The tire 1 is the tire 1 according to any one of the above items [1] to [7], wherein the inclination angle θ41 (see FIG. 4) of the width direction portion 41 with respect to the tire width direction is in the range of 1 [deg]≦θ41≦30 [deg]. The lower limit ensures the inclination angle θ41 of the width direction portion 41, thereby ensuring the drainage performance of the bent sipes 4A to 4C, while the upper limit ensures the rigidity of the land portions 32, 33.

[0081] [9] The tire 1 is the tire 1 according to any one of the above items [1] to [8], wherein the inclination angle θ42 (see FIG. 4) of the circumferential portion 42 with respect to the tire width direction is in the range of 20 degrees ≦ θ42 ≦ 70 degrees. The lower limit ensures the inclination angle θ42 of the circumferential portion 42, ensuring the drainage performance of the bent sipes 4A to 4C, while the upper limit ensures the rigidity of the land portions 32, 33.

[0082]

[10] The tire 1 is the tire 1 described in any one of the above [1] to [9], wherein one of the plurality of land portions 31 to 35 (the central land portion 33 in FIG. 2) includes a plurality of flexed sipes 4A, 4B (see FIG. 2). The plurality of flexed sipes 4A, 4B includes a plurality of first flexed sipes 4A connected to one edge portion of the land portion 33 and a plurality of second flexed sipes 4B connected to the other edge portion of the land portion 33 (see FIG. 3). The first flexed sipes 4A and the second flexed sipes 4B are arranged alternately in the tire circumferential direction. This allows the flexed sipes 4A, 4B to be dispersed in the tire circumferential direction, which has the advantage of reducing tire pattern noise.

[0083]

[11] The tire 1 is the tire 1 described in any one of [1] to

[10] above, wherein one of the plurality of land portions 31 to 35 (the inner middle land portion 32 in FIG. 2) includes a plurality of cutouts 5 and a plurality of flexed sipes 4C (see FIG. 2). The plurality of flexed sipes 4C connect to one edge portion of the land portion 32, and the plurality of cutouts 5 connect to the other edge portion of the land portion 32 (see FIG. 3). The flexed sipes 4C and the cutouts 5 are arranged alternately in the tire circumferential direction. This allows the flexed sipes 4C and the cutouts 5 to be dispersed in the tire circumferential direction, which has the advantage of reducing tire pattern noise.

[0084]

[12] The tire 1 is the tire 1 according to any one of [1] to

[11] above, further comprising a mounting direction indicator (not shown) that indicates the mounting direction of the tire on a vehicle. The multiple circumferential main grooves 21-24 are each made up of a pair of shoulder main grooves 21, 24 and two center main grooves 22, 23, and the multiple land portions 31-35 are each made up of a pair of shoulder land portions 31, 35, a pair of middle land portions 32, 34, and a row of center land portion 33 (see FIG. 2). The multiple bent sipes 4A-4C are disposed in at least one of the pair of middle land portions 32, 34, the inner middle land portion 32 located on the inner side in the vehicle width direction, and the center land portion 33. This advantageously improves both wet performance and wear resistance.

[0085] Applies to In this embodiment, as described above, a pneumatic tire has been described as an example of a tire. However, the present invention is not limited to this, and the configuration described in this 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]

[0086] 7 and 8 are tables showing the results of performance tests of the tire according to the embodiment of the present invention.

[0087] In this performance test, several types of test tires were evaluated for (1) wet performance, (2) noise performance, and (3) wear resistance. In addition, test tires with a tire size of 235 / 50R18 97W were mounted on rims with a rim size of 18x7.5J, and the test tires were subjected to the specified JATMA load.

[0088] (1) In the evaluation of wet performance, an internal pressure of 220 kPa is applied to the test tire. The test tire is mounted on a test vehicle for performing a predetermined μ-S evaluation. The test vehicle then travels on a test course on a wet road surface, and the deceleration caused by the ABS (Anti-lock Brake System) activation is measured from a speed of 60 km / h to 20 km / h. This evaluation is performed using an index evaluation with the comparative example as the standard (100), and the higher the value, the better.

[0089] (2) For the evaluation of noise performance, the test tires were mounted on all wheels of a test vehicle, a two-wheel drive (2WD) miniature van, and the test tires were pressurized with an internal pressure of 230 kPa for the front wheels and 240 kPa for the rear wheels. The test vehicle was coasted on a test course with a rough road surface at a speed of 10 to 20 km / h, and the test driver performed a sensory evaluation of the interior noise (road noise). This evaluation was performed using an index rating with the comparative example as the standard (100), with the higher the value, the better.

[0090] (3) For the evaluation of wear resistance, the test tires were mounted on all wheels of a 2WD minivan test vehicle, and the internal pressure of the test tires was set at 230 kPa for the front wheels and 240 kPa for the rear wheels. After the test vehicle had traveled 30,000 km on a designated paved road, the degree of wear was observed and evaluated. This evaluation was performed using an index rating with the comparative example as the standard (100), and the higher the value, the better.

[0091] The test tire of the example has the configuration shown in FIGS. 1 to 3, with the center land portion 33 having first and second flexed sipes 4A and 4B, and the inner middle land portion 32 having a third flexed sipe 4C and a notch 5. The maximum width W41_max of the widthwise portions 41 of the flexed sipes 4A to 4C is 30.0 mm, and the maximum depth H41_max is 6.2 mm. The maximum depth H411_max of the widened portion 411 is 5.0 mm. The ground contact widths Wb2 and Wb3 of the land portions 32 and 33 are Wb2 = 20.0 mm and Wb3 = 28.0 mm, respectively, resulting in a tire ground contact width TW of 192 mm. The maximum groove depth Hg of the circumferential main grooves 21 to 24 is 8.5 mm.

[0092] The test tire of the comparative example is the test tire of Example 1, in which each of the bent sipes 4A to 4C has a straight shape and penetrates each of the land portions 32, 33.

[0093] As the test results show, the test tires of the example equipped with the curved sipes 4A to 4C have improved wet performance, noise performance, and wear resistance compared to the comparative example tires equipped with straight through sipes. [Explanation of symbols]

[0094] 1 tire; 11 bead core; 12 bead filler; 13 carcass layer; 14 belt layer; 141, 142 cross belt; 143 belt cover; 15 tread rubber; 16 sidewall rubber; 17 rim cushion rubber; 21-24 circumferential main groove; 31 inner shoulder land portion; 311, 312 inner shoulder sipe; 32 inner middle land portion; 33 center land portion; 34 outer middle land portion; 341 cutout portion; 35 outer shoulder land portion; 351, 352 outer shoulder sipe; 4A-4C bending sipe; 41 width direction portion; 411 widened portion; 42 circumferential direction portion; 5 cutout portion

Claims

1. A tire having a plurality of circumferential main grooves and a plurality of land portions defined by the plurality of circumferential main grooves, At least one of the plurality of land portions includes a plurality of bent sipes having a bent shape, The bent sipe is formed by connecting a width direction portion that extends in the tire width direction and connects to an edge portion of the land portion, and a circumferential direction portion that extends in the tire circumferential direction and terminates inside the land portion, and A tire characterized in that an extension length L41 of the width direction portion in the tire width direction, relative to a contact width Wb of the land portion, is in the range of 0.55≦L41 / Wb≦0.

85.

2. The tire according to claim 1, wherein an extension length L42 of the circumferential portion in the tire circumferential direction and an extension length L41 of the widthwise portion in the tire width direction are in a range of 0.10≦L42 / L41≦0.

40.

3. The tire according to claim 1 , wherein the width direction portion has a widened portion at a connection portion between the land portion and the one edge portion.

4. The tire according to claim 3, wherein an extension length L411 of the widened portion in the tire width direction is in a range of 0.15≦L411 / L41≦0.50 relative to an extension length L41 of the width direction portion in the tire width direction.

5. The tire according to claim 3, wherein the maximum width W41_max of the width direction portion is in the range of 0.20≦W41_max / W411_max≦0.50 relative to the maximum width W411_max of the widened portion.

6. The tire according to claim 3 , wherein the land portion closest to the tire equatorial plane among the plurality of land portions includes the plurality of bent sipes having the widened portion.

7. The tire according to claim 1 , wherein the width direction portion and the circumferential direction portion are inclined in the same direction with respect to the tire width direction.

8. The tire according to claim 1, wherein an inclination angle θ41 of the width direction portion with respect to the tire width direction is in a range of 1 [deg]≦θ41≦30 [deg].

9. The tire according to claim 1, wherein an inclination angle θ42 of the circumferential portion with respect to the tire width direction is in a range of 20 degrees≦θ42≦70 degrees.

10. 2. The tire according to claim 1, wherein one of the plurality of land portions has the plurality of curved sipes, the plurality of curved sipes including a plurality of first curved sipes connected to one edge portion of the land portion and a plurality of second curved sipes connected to the other edge portion of the land portion, and the first curved sipes and the second curved sipes are arranged alternately in the tire circumferential direction.

11. 2. The tire according to claim 1, wherein one of the plurality of land portions includes a plurality of cutout portions and the plurality of flexed sipes, the plurality of flexed sipes are connected to one edge portion of the land portion, the plurality of cutout portions are connected to the other edge portion of the land portion, and the flexed sipes and the cutout portions are arranged alternately in the tire circumferential direction.

12. 2. The tire according to claim 1, further comprising a mounting direction indicator that indicates the direction in which the tire is mounted on a vehicle, wherein the plurality of circumferential main grooves consist of a pair of shoulder main grooves and two center main grooves, the plurality of land portions consist of a pair of shoulder land portions, a pair of middle land portions, and a row of center land portions, and the plurality of bent sipes are arranged in at least one of the pair of middle land portions located on the inner side in the vehicle width direction and the center land portion.

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