tire

Abstract

To provide tires that offer a balance of dry performance, snow performance, and resistance to uneven wear. [Solution] This tire 1 includes an inclined lug groove 22 that extends while inclined with respect to the circumferential direction of the tire and opens at one end to the tire contact end T, and inclined land portions 32A and 32B that are partitioned by adjacent inclined lug grooves 22. The inclined land portions 32A and 32B also include a plurality of through grooves 321 that penetrate the inclined land portions 32A and 32B and connect to the inclined lug groove 22, and a plurality of blocks 322 that are partitioned by the plurality of through grooves 321. In addition, at least one of the plurality of blocks 322 has a closed lug groove 323 with both ends within the block 322.

Description

Technical Field

[0001] The present invention relates to a tire, and more particularly, to a tire capable of achieving compatible dry performance, snow performance, and uneven wear resistance performance of the tire.

Background Art

[0002] In recent winter tires or all-season tires, in order to achieve both dry performance and snow performance, a so-called V-groove pattern is adopted, which is provided with inclined lug grooves that incline outward in the tire width direction from the leading side to the trailing side in the tire rotation direction. As a conventional tire adopting such a configuration, the technique described in Patent Document 1 is known.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0004] An object of the present invention is to provide a tire capable of achieving compatible dry performance, snow performance, and uneven wear resistance performance of the tire.

Means for Solving the Problem

[0005] To achieve the above object, a tire according to the present invention includes: inclined lug grooves extending while being inclined with respect to the tire circumferential direction and opening at a tire ground contact end at one end portion; and an inclined land portion defined by the adjacent inclined lug grooves, wherein the inclined land portion includes a plurality of through grooves penetrating the inclined land portion and connecting to the inclined lug grooves, and a plurality of blocks defined by the plurality of through grooves, and at least one of the plurality of blocks is provided with a closed lug groove having both end portions inside the block.

Effects of the Invention

[0006] In the tire according to this invention, (1) the inclined land portions 32A and 32B, which are partitioned by the inclined lug grooves 22, are equipped with multiple through grooves 321 and closed lug grooves 323, thereby increasing the edge component of the tread surface and improving the snow performance of the tire. Also, (2) the closed lug grooves 323 have a closed structure with both ends within the block 322, thereby ensuring the rigidity of the block 322 and ensuring the dry performance of the tire. As a result, the tire has the advantage of achieving both snow performance and dry performance. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is a cross-sectional view of a tire in the meridian direction, showing a tire according to an embodiment of this invention. [Figure 2] Figure 2 is a plan view showing the tread surface of the tire described in Figure 1. [Figure 3] Figure 3 is an enlarged view showing one side of the tread surface as described in Figure 2. [Figure 4] Figure 4 is an enlarged view showing the sloping land area described in Figure 3. [Figure 5] Figure 5 is an enlarged view showing the sloping land area block described in Figure 4. [Figure 6] Figure 6 is a cross-sectional view A showing the block described in Figure 5. [Figure 7] Figure 7 is a cross-sectional view B showing the block described in Figure 5. [Figure 8] Figure 8 is a diagram showing the results of a performance test of a tire according to an embodiment of this invention. [Figure 9] Figure 9 is a diagram showing the results of a performance test of a tire according to an embodiment of this invention. [Figure 10] Figure 10 is a diagram showing the results of a performance test of a tire according to an embodiment of this invention. [Modes for carrying out the invention]

[0008] The present invention will be described in detail below with reference to the drawings. However, this embodiment does not limit the present invention. Furthermore, the components of this embodiment include those that are substituted and obvious for substitution while maintaining the identity of the invention. In addition, the various modifications described in this embodiment can be arbitrarily combined within the scope of what is obvious to those skilled in the art.

[0009] [Air-filled tires] Figure 1 is a meridian-direction cross-sectional view of a tire according to an embodiment of this invention. The figure shows a cross-sectional view of one side region in the radial direction of the tire. The figure also shows a pneumatic radial tire for a passenger car as an example of a pneumatic tire.

[0010] In the figure, the tire meridian cross-section is defined as the cross-section obtained when the tire is cut by a plane containing the tire rotation axis (not shown). The tire equatorial plane CL is defined as a plane that passes through the midpoint of the measurement points of the tire cross-sectional width as defined in 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 diameter direction is defined as the direction perpendicular to the tire rotation axis.

[0011] The tire 1 has an annular structure centered on the tire rotation axis and comprises 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).

[0012] Each pair of bead cores 11, 11 is made by winding one or more bead wires made of steel in a ring-like and multi-layered manner, and is embedded in the bead portion to form the core of the left and right bead portions. Each pair of bead fillers 12, 12 is positioned on the outer circumference of the pair of bead cores 11, 11 in the radial direction of the tire to reinforce the bead portion.

[0013] The carcass layer 13 has a single-layer structure composed of one carcass ply or a multi-layer structure formed by laminating a plurality of carcass plies, and is bridged in a toroidal shape between the left and right bead cores 11, 11 to constitute the framework of the tire. Both end portions of the carcass layer 13 are turned back outward in the tire width direction so as to enclose the bead cores 11 and the bead fillers 12, and are locked. Further, the carcass ply of the carcass layer 13 is configured by coating a plurality of carcass cords made of steel or an organic fiber material (for example, aramid, nylon, polyester, rayon, etc.) with coating rubber and subjecting it to rolling processing, and has a cord angle (defined as the inclination angle of the longitudinal direction of the carcass cord with respect to the tire circumferential direction) of not less than 80[deg] and not more than 100[deg].

[0014] The belt layer 14 is formed by laminating a plurality of belt plies 141 to 143, and is arranged so as to be wrapped around the outer periphery of the carcass layer 13. The belt plies 141 to 143 include a pair of crossing belts 141, 142 and a belt cover 143.

[0015] The pair of crossing belts 141, 142 are configured by coating a plurality of belt cords made of steel or an organic fiber material with coating rubber and subjecting it to rolling processing, and have a cord angle of not less than 15[deg] and not more than 55[deg] in absolute value. In addition, the pair of crossing belts 141, 142 have cord angles of mutually opposite signs (defined as the inclination angle of the longitudinal direction of the belt cord with respect to the tire circumferential direction), and are laminated with the longitudinal directions of the belt cords intersecting each other (a so-called cross-ply structure). Further, the pair of crossing belts 141, 142 are arranged so as to be laminated on the outer side of the carcass layer 13 in the tire radial direction.

[0016] The belt cover 143 is configured by coating a belt cover cord made of steel or an organic fiber material with coating rubber, and has a cord angle of not less than 0[deg] and not more than 10[deg] in absolute value. Further, the belt cover 143 is, for example, a strip material formed by coating one or a plurality of belt cover cords with coating rubber, and is configured by spirally winding this strip material a plurality of times in the tire circumferential direction around the outer peripheral surfaces of the crossing belts 141, 142.

[0017] The tread rubber 15 is disposed on the outer side in the tire radial direction of the carcass layer 13 and the belt layer 14 to constitute the tread portion of the tire. The pair of sidewall rubbers 16, 16 are respectively disposed on the outer side in the tire width direction of the carcass layer 13 to constitute the left and right sidewall portions. The pair of rim cushion rubbers 17, 17 extend from the inner side in the tire radial direction of the turn-up portions of the left and right bead cores 11, 11 and the carcass layer 13 to the outer side in the tire width direction, so as to constitute the rim fitting surface of the bead portion.

[0018] [Tread Pattern] Figure 2 is a plan view showing the tread surface of the tire 1 described in Figure 1. This drawing shows the tread surface of a winter tire. Figure 3 is an enlarged view showing one side region of the tread surface described in Figure 2. Figure 4 is an enlarged view showing the inclined land portions 32A, 32B described in Figure 3.

[0019] In Figure 2, the tire rotation direction is defined as the rotation direction with high frequency of use when the tire is in use, more specifically, the rotation direction when the vehicle moves forward. In addition, depending on the tire rotation direction, the leading side (so-called kick-in side or toe side) and the trailing side (so-called kick-out side or heel side) of the block when the tire is in ground contact are defined. Further, the pneumatic tire is provided with a rotation direction indicating portion (not shown) that indicates the tire rotation direction. The rotation direction indicating portion is constituted by, for example, marks or unevenness provided on the sidewall portion of the tire.

[0020] As shown in Figure 2, the tire 1 includes a pair of circumferential grooves 21, 21, a plurality of inclined lug grooves 22, a single row of center land portion 31, and a plurality of inclined land portions 32A, 32B.

[0021] The pair of circumferential grooves 21, 21 extend continuously along the entire circumference of the tire. In the configuration shown in Figure 2, each of the pair of circumferential grooves 21, 21 is a main groove and is required to display a wear indicator as specified by JATMA. The groove width Wg1 (see Figure 3) of each of the pair of circumferential grooves 21, 21 is in the range of 5.6 [mm] ≤ Wg1 ≤ 8.0 [mm], and the groove depth Hg1 (not shown) is in the range of 6.0 [mm] ≤ Hg1 ≤ 9.6 [mm].

[0022] The groove width is measured as the distance between opposing groove walls at the groove opening when the tire is mounted on a specified rim and filled to the specified internal pressure in an unloaded state. In configurations with a notch or chamfer at the groove opening, the groove width is measured at the intersection of the extension line of the tread surface and the extension line of the groove wall in a cross-sectional view parallel to the groove width direction and groove depth direction.

[0023] Groove depth is measured as the distance from the tread surface to the point of maximum groove depth when the tire is mounted on a specified rim and filled to the specified internal pressure in an unloaded state. In configurations with partial irregularities or sipes at the bottom of the groove, these are excluded when measuring the groove depth.

[0024] Furthermore, the specified rim refers to the "applicable rim" specified in JATMA, the "Design Rim" specified in TRA, or the "Measuring Rim" specified in ETRTO. Furthermore, the specified internal pressure refers to the "maximum air pressure" specified in JATMA, the maximum value of "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified in TRA, or the "INFLATION PRESSURES" specified in ETRTO. Furthermore, the specified load refers to the "maximum load capacity" specified in JATMA, the maximum value of "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified in TRA, or the "LOAD CAPACITY" specified in ETRTO. However, in JATMA, for passenger car tires, the specified internal pressure is 180 [kPa] air pressure, and the specified load is 88 [%] of the maximum load capacity.

[0025] Furthermore, in Figure 2, the distance D21 in the tire width direction from the tire contact edge T to the groove centerline (not shown) of the circumferential groove 21 is in the range of 0.35 ≤ D21 / TW ≤ 0.45 with respect to the tire contact width TW, and preferably in the range of 0.37 ≤ D21 / TW ≤ 0.43.

[0026] Furthermore, the tire contact end T is defined as the position of the maximum width in the axial direction of the tire at the contact surface between the tire and the flat plate when the tire is mounted on a specified rim, subjected to a specified internal pressure, and placed perpendicular to the flat plate in a stationary state, with a load corresponding to a specified load applied.

[0027] The tire contact width TW is measured as the maximum straight distance in the axial direction of the tire at the contact surface between the tire and the flat plate when the tire is mounted on a specified rim, subjected to a specified internal pressure, and placed perpendicular to a flat plate in a stationary state while a load corresponding to a specified load is applied.

[0028] As shown in Figure 2, the multiple inclined lug grooves 22 extend while inclined with respect to the tire circumferential direction and open at one end to the tire contact edge T. The multiple inclined lug grooves 22 are arranged at predetermined intervals in the tire circumferential direction. In the configuration shown in Figure 2, each of the multiple inclined lug grooves 22 is a main groove and is required to display a wear indicator as specified by JATMA. The groove width Wg2 (see Figure 3) of each of the multiple inclined lug grooves 22 is in the range of 5.8 [mm] ≤ Wg2 ≤ 8.8 [mm], and the groove depth Hg2 (not shown) is in the range of 6.0 [mm] ≤ Hg2 ≤ 9.6 [mm].

[0029] Furthermore, the extending length Lg2 (see Figure 3) of the inclined lug groove 22 in the tire width direction is in the range of 0.33 ≤ Lg2 / TW ≤ 0.58 with respect to the tire contact width TW, preferably in the range of 0.35 ≤ Lg2 / TW ≤ 0.56. This ensures that the function of the inclined lug groove 22 as a main groove is properly ensured. For example, a configuration in which Lg2 / TW is close to 0.50 is one in which the inclined lug groove 22 intersects the circumferential groove in a configuration on the tire equatorial plane CL (not shown). For example, a configuration in which Lg2 / TW is greater than 0.50 is one in which the inclined lug groove 22 extends beyond the tire equatorial plane in a so-called V-groove pattern (not shown).

[0030] Furthermore, in the configuration shown in Figure 2, each of the multiple inclined lug grooves 22 opens to the tire contact edge T at one end and connects to the circumferential groove 21 at the other end. Each of the multiple inclined lug grooves 22 has a gently curved arc shape or a gently bent L shape, and extends inclined in a direction away from the tire equatorial plane CL from the leading end to the trailing end in the tire rotation direction. This ensures block rigidity during cornering and improves the tire's dry performance.

[0031] Furthermore, in the configuration shown in Figure 2, multiple inclined lug grooves 22 are arranged in the left and right regions bounded by the tire equatorial plane CL. The multiple inclined lug grooves 22 arranged in one region bounded by the tire equatorial plane CL and the multiple inclined lug grooves 22 arranged in the other region are inclined in opposite directions with respect to the tire circumferential direction and are arranged in a staggered pattern toward the tire circumferential direction. This forms a directional V-shaped groove pattern, ensuring block rigidity during cornering.

[0032] Furthermore, as shown in Figure 2, the inclination angle of the inclined lug groove 22 with respect to the circumferential direction of the tire increases monotonically from the tire equatorial plane CL toward the tire contact patch T. Also, in Figure 3, the inclination angle θg2c of the inclined lug groove 22 at the connection point with the circumferential groove 21 is in the range of 20[deg]≦θg2c≦50[deg], and the inclination angle θg2t of the inclined lug groove 22 at the intersection with the tire contact patch T is in the range of 60[deg]≦θg2t≦90[deg].

[0033] The inclination angle θg2c of the inclined lug groove 22 is defined as the angle between the tangent to the groove centerline of the inclined lug groove 22 and the tire circumferential direction. The groove centerline of the inclined lug groove 22 is defined as a smooth curve connecting the midpoints of the left and right groove walls of the inclined lug groove 22.

[0034] Furthermore, as shown in Figure 4, the inclined lug groove 22 has a bottom portion 221 at the connection point with the circumferential groove 21. The bottom portion 221 raises the bottom of the inclined lug groove 22, reinforcing the rigidity of the inclined land portions 32A and 32B at the connection point between the inclined lug groove 22 and the circumferential groove 21. In addition, the height Hg21 (not shown) of the bottom portion 221 is in the range of 0.30 ≤ Hg21 / Hg2 ≤ 0.50 with respect to the maximum groove depth Hg2 of the inclined lug groove 22 at the connection point with the circumferential groove 21.

[0035] The height Hg21 of the bottom portion 221 is measured as the maximum height from the bottom of the inclined lug groove 22 to the top surface of the bottom portion 221.

[0036] As shown in Figure 2, the single row of center ridge sections 31 is divided into a pair of circumferential grooves 21, 21. Furthermore, the center ridge section 31 is not a row of blocks divided by through lug grooves, but a rib with a continuous tread surface in the circumferential direction of the tire. This ensures the rigidity of the center ridge section 31 and improves the dry performance of the tire.

[0037] Furthermore, in Figure 2, the width Wb2 of the center land portion 31 is in the range of 0.10 ≤ Wb2 / TW ≤ 0.20 relative to the tire contact width TW, preferably in the range of 0.13 ≤ Wb2 / TW ≤ 0.17. The lower limit ensures the rigidity of the center land portion 31 and thus the dry performance of the tire, while the upper limit ensures the distance D21 from the circumferential groove 21 to the tire contact edge T, thereby ensuring resistance to uneven wear in the tread shoulder region.

[0038] Furthermore, as shown in Figure 3, the center land portion 31 is provided with first and second center lug grooves 311 and 312. The first and second center lug grooves 311 and 312 connect to the circumferential groove 21 at one end and terminate within the center land portion 31 at the other end. The first center lug groove 311 has a long structure and extends in the tire width direction, intersecting the tire equatorial plane CL. The second center lug groove 312 has a short structure and terminates without intersecting the tire equatorial plane. The first and second center lug grooves 311 and 312 are arranged alternately in the tire circumferential direction along one circumferential groove 21 of the center land portion 31. In addition, multiple first center lug grooves 311 are arranged in a staggered pattern in the tire circumferential direction. This ensures the rigidity of the center land portion 31, thereby ensuring the tire's dry performance, and also ensures the tire's resistance to uneven wear due to the uniform rigidity of the center land portion 31.

[0039] As shown in Figure 2, the inclined land sections 32A and 32B are divided into a single circumferential groove 21 and a pair of adjacent inclined lug grooves 22, 22 in the tire circumferential direction, and have a long structure that extends from the circumferential groove 21 beyond one tire contact edge T to the tread edge. In addition, multiple inclined land sections 32A and 32B are arranged adjacent to each other in the tire circumferential direction. Furthermore, multiple inclined land sections 32A and 32B are arranged in the left and right regions with the tire equatorial plane CL as the boundary. In the configuration of Figure 2, the multiple inclined land sections 32A and 32B arranged in one region with the tire equatorial plane CL as the boundary and the multiple inclined land sections 32A and 32B arranged in the other region are arranged in a staggered pattern toward the tire circumferential direction.

[0040] Figure 5 is an enlarged view showing blocks 322 of the sloping land areas 32A and 32B described in Figure 4. This figure shows individual blocks 322 extracted. Figures 6 and 7 are A-view cross-sections (Figure 6) and B-view cross-sections (Figure 7) of block 322 described in Figure 5.

[0041] As shown in Figure 3, each of the multiple sloping land sections 32A and 32B is provided with multiple through grooves 321 and multiple blocks 322.

[0042] As shown in Figures 3 and 4, the through grooves 321 penetrate the inclined land sections 32A and 32B in the circumferential direction of the tire and connect to adjacent inclined lug grooves 22, 22. Multiple through grooves 321 are arranged at predetermined intervals along the longitudinal direction of the inclined land sections 32A and 32B, i.e., from the circumferential grooves 21 toward the tire contact edge T. The groove width W21 (see Figure 4) of the through grooves 321 is in the range of 2.0 [mm] ≤ W21 ≤ 5.0 [mm]. Furthermore, the through grooves 321 open and function as grooves when the tire makes contact with the ground. This increases the edge component of the tread surface, ensuring the tire's snow performance.

[0043] Furthermore, each of the multiple through grooves 321 is inclined in the opposite direction to the inclined lug grooves 22 in the tire circumferential direction. Specifically, as shown in Figure 3, each of the multiple through grooves 321 is inclined toward the tire equatorial plane CL from the leading side to the trailing side in the tire rotation direction. This ensures block rigidity during cornering and improves the tire's dry performance. In addition, the inclination angle θ21 of the through grooves 321 with respect to the tire circumferential direction (see Figure 4) is in the range of 20 degrees to 50 degrees.

[0044] The inclination angle θ21 of the through groove 321 is defined as the angle between the tangent to the groove centerline of the through groove 321 and the tire circumferential direction. The groove centerline of the through groove 321 is defined as a smooth curve connecting the midpoints of the left and right groove walls of the through groove 321.

[0045] Furthermore, in Figure 4, the inclination angle of the through groove 321 relative to the inclined lug groove 22 (dimensions omitted in the figure) is in the range of 55 degrees to 90 degrees, preferably in the range of 65 degrees to 90 degrees. This ensures that the angle of the corners of the block 322 is maintained, thereby suppressing chipping of the block 322.

[0046] For example, in the configuration shown in Figure 2, the through grooves 321, 321 of adjacent inclined land sections 32A and 32B are arranged in a line with their longitudinal directions aligned. As a result, a long, narrow groove consisting of multiple through grooves 321 extends in the region between the circumferential groove 21 and the tire contact edge T, while being inclined with respect to the tire's circumferential direction. Furthermore, none of the through grooves 321 are connected to the circumferential groove 21 or the tire contact edge T. This results in the formation of a grid-like groove pattern consisting of the inclined land sections 32A, 32B and the through grooves 321, 321 in the region between the circumferential groove 21 and the tire contact edge T.

[0047] Furthermore, in Figure 6, the groove depth H21 of the through groove 321 is in the range of 0.30 ≤ H21 / Hg2 ≤ 0.80 relative to the groove depth Hg2 of the inclined lug groove 22, preferably in the range of 0.40 ≤ H21 / Hg2 ≤ 0.70. The lower limit ensures the groove depth H21 of the through groove 321, thereby ensuring the snow performance of the tire, and the upper limit ensures the rigidity of the inclined land sections 32A and 32B, thereby ensuring the dry performance of the tire.

[0048] Multiple blocks 322 are divided by adjacent inclined lug grooves 22, 22 and multiple through grooves 321, and are arranged along the inclined lug grooves 22 in the longitudinal direction of the inclined land sections 32A, 32B. In addition, each inclined land section 32A;32B has 2 to 4 through grooves 321, thereby dividing 3 to 5 blocks 322. For example, in the configuration of Figure 4, 4 blocks 322 are divided by 3 through grooves 321. The innermost block 322 in the tire width direction faces the circumferential groove 21, and the outermost block 322 in the tire width direction is on the tire contact edge T.

[0049] Furthermore, the ratio of the maximum and minimum contact areas of the multiple blocks 322 constituting one sloping land area 32A;32B is in the range of 1.00 to 1.90, preferably in the range of 1.00 to 1.70. This ensures that the contact area of ​​the blocks 322 is uniform, thereby suppressing uneven wear of the blocks 322.

[0050] The contact area of ​​block 322 is defined as the contact surface between the tire and the flat plate (specifically, the area enclosed by the contour lines of the contact surface) when the tire is mounted on a specified rim, subjected to a specified internal pressure, and placed perpendicular to the flat plate in a stationary state with a load corresponding to a specified load applied.

[0051] For example, in the configuration shown in Figure 2, as shown in Figures 3 and 4, a first inclined land section 32A, which has the largest contact area block 322 at the outermost edge in the tire width direction (tire contact end T side), and a second inclined land section 32B, which has the largest contact area block 322 at the innermost edge in the tire width direction (circumferential groove 21 side), are arranged alternately in the circumferential direction of the tire.

[0052] Furthermore, in the configuration shown in Figure 2, all blocks 322 have square treads. However, this is not limited to this configuration; some blocks may have triangular treads (not shown).

[0053] [Closed drag groove in the block] As shown in Figures 4 and 5, the block 322 is provided with a closed drag groove 323.

[0054] The closed drag groove 323 has a closed structure with both ends located within the block 322, and therefore does not open to the edges of the block 322. This ensures the rigidity of the block 322, guaranteeing the tire's dry performance and suppressing uneven wear of the block 322. Furthermore, the closed drag groove 323 opens and functions as a groove when the tire makes contact with the ground. This increases the tire's edge component, improving the tire's snow performance.

[0055] Furthermore, the groove width W23 of the closed drag groove 323 (see Figure 5) is in the range of 0.8 [mm] ≤ W23 ≤ 2.0 [mm], preferably in the range of 1.0 [mm] ≤ W23 ≤ 1.5 [mm]. Also, the groove width W23 of the closed drag groove 323 (see Figure 5) is in the range of 3.0 ≤ W23 / Wg2 ≤ 9.0 with respect to the groove width Wg2 of the inclined lug groove 22 (see Figure 3), preferably in the range of 5.0 ≤ W23 / Wg2 ≤ 7.0. The above lower limit ensures the rigidity of the block 322, and the above upper limit ensures the effect of the closed drag groove 323 on improving the snow performance of the tire.

[0056] Furthermore, as shown in Figure 4, the closed drag groove 323 extends in the longitudinal direction of the inclined land portions 32A and 32B. Also, in Figure 5, the inclination angle α of the closed drag groove 323 with respect to the inclined lug groove 22 is in the range of -30[deg]≦α≦30[deg], and preferably in the range of -10[deg]≦α≦10[deg]. Therefore, it is preferable that the closed drag groove 323 extends substantially parallel to the inclined lug groove 22. This ensures that the rigidity of the block 322 is properly maintained.

[0057] The inclination angle α of the closed drag groove 323 is measured as the angle between a virtual straight line passing through both ends of the closed drag groove 323 and the groove centerline of the inclined drag groove 22, and is defined as positive when the inclination is in the same direction as the inclination direction of the inclined drag groove 22 with respect to the circumferential direction of the tire.

[0058] Furthermore, in the configuration shown in Figure 4, the closed drag groove 323 has a straight shape. However, it is not limited to this; the closed drag groove 323 may also have an arc shape, a bent shape, or a wave shape (not shown).

[0059] Furthermore, in Figure 5, the extended length L23 of the closed drag groove 323 is in the range of 0.70 ≤ L23 / L22 ≤ 0.90 relative to the length L22 of the block 322, preferably in the range of 0.75 ≤ L23 / L22 ≤ 0.85. The lower limit ensures uniform rigidity within the block 322, suppressing uneven wear of the block 322, while the upper limit ensures the rigidity of the block 322, thus ensuring the dry performance of the tire.

[0060] The extended length L23 of the closed lug groove 323 is defined as the extended length in the direction parallel to the inclined lug groove 22.

[0061] The length L22 of block 322 is defined as the length in the direction parallel to the inclined lug groove 22 at the position where the closed lug groove 323 is located.

[0062] Furthermore, in Figure 5, the distance D23 from the end of the closed drag groove 323 to the edge of the block 322 is in the range of 0.05 ≤ D23 / L22 with respect to the length L22 of the block 322, preferably in the range of 0.10 ≤ D23 / L22. This ensures that the rigidity of the block 322 is adequately maintained. There is no particular upper limit to the ratio D23 / L22, but it is constrained by other conditions.

[0063] Furthermore, in Figure 5, the closed drag groove 323 is positioned in the center of the width direction of the block 322. Specifically, the closed drag groove 323 is positioned in the central region of the distance W22 between the left and right edges of the block 322, which is divided by adjacent inclined drag grooves 22, 22, preferably 40%, of the region. This equalizes the rigidity within the block 322 and suppresses uneven wear of the block 322.

[0064] Further, in Figure 6, the groove depth H23 of the closed lug groove 323 is in the range of 0.50≦H23 / Hg2≦0.80, preferably in the range of 0.60≦H23 / Hg2≦0.70, relative to the groove depth Hg2 of the inclined lug groove 22. The above lower limit ensures the rigidity of the block 322, and the above upper limit ensures the effect of the closed lug groove 323 in improving the snow performance of the tire.

[0065] Further, as shown in Figure 7, the closed lug groove 323 has a groove bottom raised portion 3231 at the longitudinal central portion. This increases the rigidity of the block 322. In addition, the extending length L23' of the top of the groove bottom raised portion 3231 is in the range of 0.20≦L23' / L23≦0.40 relative to the extending length L23 of the closed lug groove 323. Further, the height H23' of the top of the groove bottom raised portion 3231 is in the range of 0.30≦H23' / H23_max≦0.50 relative to the maximum value H23_max of the depth H23 of the closed lug groove 323.

[0066] Note that in the configuration of Figure 4, all blocks 322 are provided with the closed lug groove 323, and one block 322 is provided with a single closed lug groove 323. However, the present invention is not limited to this, and some of the blocks 322 may be provided with the closed lug groove 323, or one block 322 may be provided with a single closed lug groove 323 (not illustrated).

[0067] [Block Sipes] Further, in the configuration of Figure 2, as shown in Figure 4, the block 322 is provided with a plurality of sipes 4. The sipe 4 is a cut formed in the tread surface, and has a width W4 (see Figure 5) of less than 1.5 [mm] and a depth H4 (see Figure 6) of 2.0 [mm] or more, so that it closes when the tire is in contact with the ground. Further, in Figure 5, the sipe width W4 of the sipe 4 is in the range of 0<W4 / W23≦0.80, preferably in the range of 0<W4 / W23≦0.70, relative to the groove width W23 of the closed lug groove 323. This ensures the rigidity of the block 322.

[0068] For example, in the configuration shown in Figure 4, one block 322 has two or four sipes 4. These sipes 4 connect to a circumferential groove 21, a through groove 321, or the tire contact end T at at least one end. Specifically, a short block 322 (in Figure 4, particularly the two rows of blocks in the central part of the inclined land sections 32A and 32B) has two sipes 4, and these sipes 4 penetrate the block 322 in the longitudinal direction of the inclined land sections 32A and 32B and connect to the through groove 321. Furthermore, the long blocks 322 (in Figure 4, in particular the outermost block 322 in the tire width direction of the first inclined land section 32A and the innermost block 322 in the tire width direction of the second inclined land section 32B) are equipped with four sipes, some of which connect to the through groove 321 at one end and terminate inside the block 322 at the other end, while the other sipes 4 connect to the circumferential groove 21 or the tire contact end T at one end and terminate inside the block 322 at the other end.

[0069] Furthermore, as shown in Figure 5, the sipe 4 has a wave shape (or zigzag shape). The period T4 and amplitude A4 of the wave shape of the sipe are in the range of 2.00 ≤ T4 / W23 ≤ 5.00 and 0.60 ≤ A4 / W23 ≤ 2.00 with respect to the groove width W23 of the closed drag groove 323, and preferably in the range of 3.00 ≤ T4 / W23 ≤ 4.00 and 1.00 ≤ A4 / W23 ≤ 1.60. This optimizes the wave shape of the sipe 4, achieving a balance between the dry and snow performance of the tire.

[0070] Furthermore, in Figure 2, the snow traction index STI (so-called 0[deg] snow traction index) in the circumferential direction of the tire around its entire circumference is in the range of 190 ≤ STI ≤ 230. In addition, the sipe component of the snow traction index STI is in the range of 70 to 110, preferably 80 to 100. The lower limit ensures the snow traction performance of the tire, and the upper limit ensures the dry performance of the tire.

[0071] The Snow Traction Index (STI) is an empirical formula proposed by Uniroyal to the SAE (Society of Automotive Engineers) and is defined by the following equation (1). In this equation, Pg is the groove density [1 / mm], calculated as the ratio of the groove length [mm] of all grooves (all grooves except sipes) projected in the circumferential direction on the tire contact surface to the tire contact area (product of tire contact width and tire circumference) [mm^2]. ρs is the sipe density [1 / mm], calculated as the ratio of the sipe length [mm] of all sipes projected in the circumferential direction on the tire contact surface to the tire contact area [mm^2]. Dg is the average value of the groove depth [mm] of all grooves projected in the circumferential direction on the tire contact surface.

[0072] STI=-6.8+2202×Pg+672×ρs+7.6×Dg (1)

[0073] [effect] As described above, [1] the tire 1 includes an inclined lug groove 22 that extends inclined with respect to the circumferential direction of the tire and opens at one end to the tire contact end T, and inclined land portions 32A and 32B that are partitioned by adjacent inclined lug grooves 22 (see Figure 2). The inclined land portions 32A and 32B also include a plurality of through grooves 321 that penetrate the inclined land portions 32A and 32B and connect to the inclined lug groove 22, and a plurality of blocks 322 that are partitioned by the plurality of through grooves 321 (see Figure 3). At least one of the plurality of blocks 322 also includes a closed lug groove 323 having both ends within the block 322 (see Figure 4).

[0074] In this configuration, (1) the inclined land sections 32A and 32B, which are partitioned by the inclined lug grooves 22, are equipped with multiple through grooves 321 and closed lug grooves 323, thereby increasing the edge component of the tread surface and improving the snow performance of the tire. Also, (2) the closed lug grooves 323 have a closed structure with both ends within the block 322, thereby ensuring the rigidity of the block 322 and ensuring the dry performance of the tire. As a result, there is an advantage in that the tire achieves both snow and dry performance.

[0075] Furthermore, [2] in this tire 1, the inclination angle α (see Figure 5) of the closed lug groove 323 with respect to the inclined lug groove 22 is in the range of -30 [deg] ≤ α ≤ 30 [deg]. This configuration has the advantage that the rigidity of the block 322 is properly ensured because the closed lug groove 323 extends substantially parallel to the inclined lug groove 22.

[0076] Furthermore, [3] in this tire 1, the groove width W23 (see Figure 5) of the closed drag groove 323 is in the range of 0.8 [mm] ≤ W23 ≤ 2.0 [mm], and the closed drag groove 323 opens when the tire makes contact with the ground. This ensures that the closed drag groove 323 functions as a groove, which has the advantage of improving the snow performance of the tire.

[0077] Furthermore, [4] in this tire 1, the inclined lug groove 22 is the main groove that has the obligation to display a wear indicator as stipulated by JATMA, as described in any one of [1] to [3] above. Also, the extending length Lg2 (see Figure 3) of the inclined lug groove 22 in the tire width direction is in the range of 0.33 ≤ Lg2 / TW ≤ 0.58 with respect to the tire contact width TW (see Figure 2). This has the advantage of ensuring the proper function of the inclined lug groove 22 as the main groove and ensuring the snow performance of the tire.

[0078] Furthermore, [5] in this tire 1, in the tire 1 described in any one of [1] to [4] above, the extended length L23 of the closed drag groove 323 (see Figure 5) is in the range of 0.70 ≤ L23 / L22 ≤ 0.90 relative to the length L22 of the block 322. The above lower limit equalizes the rigidity within the block 322, suppressing uneven wear of the block 322, and the above upper limit ensures the rigidity of the block 322, thus ensuring the dry performance of the tire.

[0079] Furthermore, [6] in this tire 1, in the tire 1 described in any one of [1] to [5] above, the groove depth H21 of the through groove 321 (see Figure 6) is in the range of 0.30 ≤ H21 / Hg2 ≤ 0.80 relative to the groove depth Hg2 of the inclined lug groove 22. The above lower limit ensures the groove depth H21 of the through groove 321, thereby ensuring the snow performance of the tire, and the above upper limit ensures the rigidity of the inclined land sections 32A and 32B, thereby ensuring the dry performance of the tire.

[0080] Furthermore, [7] in this tire 1, in addition to the tire 1 described in any one of [1] to [6] above, a rotation direction indicator is provided to show the direction of tire rotation, and the inclined lug groove 22 is inclined outward in the tire width direction from the leading side to the trailing side in the tire rotation direction (see Figure 2). This has the advantage of ensuring block rigidity during cornering and improving the dry performance of the tire.

[0081] Furthermore, [8] in this tire 1, in the tire 1 described in any one of [1] to [7] above, the multiple through grooves 321 are inclined in the opposite direction to the inclined lug grooves 22 in the tire circumferential direction (see Figure 3). This ensures the rigidity of the blocks 322 during cornering, which has the advantage of improving the dry performance of the tire.

[0082] Further, in [9] this tire 1, the tire 1 according to any one of the above [1] to [8] is provided with a pair of circumferential grooves 21, 21 extending in the tire circumferential direction, and a center land portion 31 which is a rib defined by the pair of circumferential grooves 21, 21 and having a tread surface continuous in the tire circumferential direction (see FIG. 2). Further, the inclined lug groove 22 is connected at the other end to one of the pair of circumferential grooves 21. This has the advantage that the rigidity of the center land portion 31 is ensured and the dry performance of the tire is improved.

[0083] Further, in

[10] this tire 1, in the tire 1 according to any one of the above [1] to [9], the width Wb2 of the center land portion 31 (see FIG. 2) is in the range of 0.10≦Wb2 / TW≦0.20 with respect to the tire ground contact width TW. The lower limit ensures the rigidity of the center land portion 31 to secure the dry performance of the tire, and the upper limit ensures the distance D21 from the circumferential groove 21 to the tire ground contact end T, which has the advantage of securing the uneven wear resistance performance in the shoulder region of the tread portion.

[0084] Further, in

[11] this tire 1, in the tire 1 according to any one of the above [1] to

[10] , the block 322 is provided with a sipe 4 (see FIG. 4). Further, the sipe width W4 of the sipe 4 is in the range of 0<W4 / W23≦0.80 with respect to the groove width W23 of the closed lug groove 323. This has the advantage that the rigidity of the block 322 is ensured.

[0085] Further, in

[12] this tire 1, in the tire 1 according to any one of the above [1] to

[11] , the block 322 is provided with a sipe 4 (see FIG. 4). Further, the period T4 and amplitude A4 of the wave shape of the sipe 4 are in the ranges of 2.00≦T4 / W23≦5.00 and 0.60≦A4 / W23≦2.00 with respect to the groove width W23 of the closed lug groove 323. Thereby, the wave shape of the sipe 4 is optimized, and both the dry performance and the snow performance of the tire are achieved.

[0086] [Application Target] In this embodiment, as described above, a pneumatic tire was explained as an example of a tire. However, the configuration described in this embodiment is not limited to this and can be arbitrarily applied to other tires within the scope of what is obvious to those skilled in the art. Examples of other tires include airless tires and solid tires. [Examples]

[0087] Figures 8 to 10 are charts showing the results of performance tests of tires according to embodiments of this invention.

[0088] In this performance test, several types of test tires were evaluated for (1) dry performance, (2) snow performance, and (3) resistance to uneven wear. A test tire with size 245 / 45R19 102V was mounted on a rim with size 19×9.0J, and this test tire was subjected to an internal pressure of 250 kPa and the JATMA specified load. The test tire was then mounted on a test vehicle, a passenger car with an engine displacement of 3000 cc and 4WD (Four Wheel Drive).

[0089] (1) In the evaluation of dry performance, the test vehicle will travel at speeds of 60 km / h to 100 km / h on a test course with a flat, dry surface. The test driver will then perform a subjective evaluation of the steering performance during lane changes and cornering, as well as the stability during straight-line driving. This evaluation will be performed using an index rating with the comparative example as the baseline (100), and a higher value is preferable.

[0090] (2) In the evaluation of snow performance, the test vehicle will drive on a designated handling course with snow at a speed of 40 km / h, and a test driver will perform a subjective evaluation of the handling stability. This evaluation will be performed using an index evaluation with the comparative example as the baseline (100), and a higher value is preferable.

[0091] (3) In the evaluation of resistance to uneven wear, after the test vehicle has traveled 30,000 km on a designated paved road, the ratio of the maximum and minimum wear amounts of the center land portion and blocks within the contact surface is obtained, and the evaluation is performed by comparing these ratios with the reference value. This evaluation is performed using an index evaluation with the comparative example as the standard (100), and a higher value is preferable.

[0092] The test tire of the embodiment has the configuration shown in Figures 1 and 2, and comprises a pair of circumferential grooves 21, a plurality of inclined lug grooves 22, and a plurality of inclined land sections 32A and 32B. Each of the plurality of inclined land sections 32A and 32B has a through groove 321, a block 322, a closed lug groove 323, and a sipe 4. The tire contact width TW is 200 [mm]. The width Wg1 of the pair of circumferential grooves 21 is 5.0 [mm], and the groove depth Hg1 is 7.4 [mm]. The average width Wg2 of the plurality of inclined lug grooves 22 is 7.2 [mm] (minimum value 6.0 [mm], maximum value 8.4 [mm]), and the groove depth Hg2 is 7.3 [mm]. The width W4 of the sipe 4 is 0.8 [mm], and the depth H4 is 5.0 [mm].

[0093] In the comparative example, the test tire of Example 1 does not have closed drag grooves 323 on the inclined land sections 32A and 32B.

[0094] As the test results show, the test tire in this example demonstrates a balance between dry performance, snow performance, and resistance to uneven wear. [Explanation of symbols]

[0095] 1 Tire; 11 Bead core; 12 Bead filler; 13 Carcass layer; 14 Belt layer; 141, 142 Cross belts; 143 Belt cover; 15 Tread rubber; 16 Sidewall rubber; 17 Rim cushion rubber; 21 Circumferential grooves; 22 Inclined lug grooves; 221 Bottom upper section; 31 Center land section; 311, 312 Center lug grooves; 32A, 32B Inclined land section; 321 Through grooves; 322 Blocks; 323 Closed lug grooves; 3231 Bottom upper section; 4 Sipes

Claims

1. A tire comprising inclined lug grooves that extend while being inclined with respect to the circumferential direction of the tire and open at one end to the tire contact edge, and inclined land portions that are partitioned by adjacent inclined lug grooves, The inclined land portion comprises a plurality of through grooves that penetrate the inclined land portion and connect to the inclined lug groove, and a plurality of blocks that are partitioned by the plurality of through grooves, A tire characterized in that at least one of the plurality of blocks is provided with a closed drag groove having both ends within the block.

2. The tire according to claim 1, wherein the inclination angle α of the closed lug groove with respect to the inclined lug groove is in the range of -30 [deg] ≤ α ≤ 30 [deg].

3. The tire according to claim 1, wherein the groove width W23 of the closed drag groove is in the range of 0.8 [mm] ≤ W23 ≤ 2.0 [mm], and the closed drag groove opens when the tire makes contact with the ground.

4. The tire according to claim 1, wherein the inclined lug groove is a main groove that has a wear indicator display obligation as defined by JATMA, and the extending length Lg2 of the inclined lug groove in the tire width direction is in the range of 0.33 ≤ Lg2 / TW ≤ 0.58 with respect to the tire contact width TW.

5. The tire according to claim 1, wherein the extended length L23 of the closed drag groove is in the range of 0.70 ≤ L23 / L22 ≤ 0.90 with respect to the length L22 of the block.

6. The tire according to claim 1, wherein the groove depth H21 of the through groove is in the range of 0.30 ≤ H21 / Hg2 ≤ 0.80 with respect to the groove depth Hg2 of the inclined lug groove.

7. The tire according to claim 1, comprising a rotation direction indicator unit that shows the direction of tire rotation, wherein the inclined lug groove is inclined outward in the tire width direction from the leading side to the trailing side in the tire rotation direction.

8. The tire according to claim 1, wherein the plurality of through grooves are inclined in the opposite direction to the inclined lug grooves in the tire circumferential direction.

9. The tire according to claim 1, comprising a pair of circumferential grooves extending in the circumferential direction of the tire, and a center land portion which is a rib that is partitioned by the pair of circumferential grooves and has a continuous tread surface in the circumferential direction of the tire, wherein the inclined lug groove is connected to one of the pair of circumferential grooves at its other end.

10. The tire according to claim 11, wherein the width Wb2 of the center land portion is in the range of 0.10 ≤ Wb2 / TW ≤ 0.20 with respect to the tire contact width TW.

11. The tire according to claim 1, wherein the block is provided with sipes, and the sipe width W4 of the sipes is in the range of 0 < W4 / W23 ≤ 0.80 with respect to the groove width W23 of the closed drag groove.

12. The tire according to claim 1, wherein the block comprises a sipe having a wave shape, and the period T4 and amplitude A4 of the wave shape of the sipe are in the ranges of 2.00 ≤ T4 / W23 ≤ 5.00 and 0.60 ≤ A4 / W23 ≤ 2.00 with respect to the groove width W23 of the closed drag groove.

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