tire

Abstract

To provide a tire capable of improving wet performance of a tire.SOLUTION: A tire 1 includes a pair of peripheral grooves 21 and 22 that are arranged in right and left regions with a tire equator surface Cl as a boundary, and intermittently extend in a tire circumferential direction (see Fig. 2 and Fig. 4). Each of the pair of peripheral grooves 21 and 22 is composed of a plurality of groove parts 211 and 221 that have an amplitude in a tire width direction and are arrayed in a zigzag shape or a wavy shape.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a tire, and more particularly to a tire capable of improving wet performance of the tire. [Background technology]

[0002] Racing tires used on both public roads and circuits are required to have circumferential grooves on the tread surface in order to ensure the wet performance of the tire. A technology described in Patent Document 1 is known as a conventional tire that employs such a structure. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent No. 7,140,410 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 improving wet performance. [Means for solving the problem]

[0005] In order to achieve the above object, the tire according to the present invention has a pair of circumferential grooves disposed in left and right regions bounded by the tire equatorial plane and extending intermittently in the tire circumferential direction, each of the pair of circumferential grooves being composed of a plurality of groove portions arranged in a zigzag or wave shape having amplitude in the tire width direction. and the amplitude of the zigzag or wavy shape of the pair of circumferential grooves is in the range of 1.0% to 4.0% of the tire contact width. It is characterized by: The tire according to the present invention has a pair of circumferential grooves disposed in left and right regions bounded by the tire equatorial plane and extending intermittently in the tire circumferential direction, each of the pair of circumferential grooves being composed of a plurality of groove portions arranged in a zigzag or wave shape having amplitude in the tire width direction. and the pitch length of the groove portions adjacent to each other in the tire circumferential direction is in the range of 3.0% to 6.0% of the tire circumference. It is characterized by: The tire according to the present invention has a pair of circumferential grooves disposed in left and right regions bounded by the tire equatorial plane and extending intermittently in the tire circumferential direction, each of the pair of circumferential grooves being composed of a plurality of groove portions arranged in a zigzag or wave shape having amplitude in the tire width direction. and the groove area ratio of the tire contact area is in the range of 3.0% to 5.0%. It is characterized by:

[0006] The tire according to the present invention includes a pair of circumferential grooves disposed in left and right regions bounded by the tire equatorial plane and extending continuously in the tire circumferential direction, and each of the pair of circumferential grooves has a zigzag or wave shape with amplitude in the tire width direction. Effect of the Invention

[0007] In the tire according to the present invention, the circumferential groove is made up of a plurality of groove portions arranged in a zigzag or wave shape, so that the arrangement area of ​​the groove portions in the tire width direction is expanded compared to a tire having a circumferential groove made up of groove portions arranged in a straight line, which has the advantage of improving the wet performance of the tire.

[0008] In addition, in the tire according to the present invention, the circumferential groove has a zigzag or wavy shape, so that the arrangement area of ​​the circumferential groove in the tire width direction is expanded compared to a configuration in which the circumferential groove has a straight shape, which has the advantage of improving the wet performance of the tire. [Brief description of the drawings]

[0009] [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. [Diagram 2] FIG. 2 is a plan view showing a tread surface of the tire shown in FIG. [Diagram 3] FIG. 3 is a cross-sectional view showing the circumferential groove shown in FIG. [Figure 4] FIG. 4 is an explanatory diagram showing a modified example of the tire shown in FIG. [Diagram 5] FIG. 5 is an explanatory diagram showing a modified example of the tire shown in FIG. [Figure 6] FIG. 6 is an explanatory diagram showing a modified example of the tire shown in FIG. [Figure 7] FIG. 7 is a table showing the results of performance tests of the tire according to the embodiment of the present invention. [Figure 8] FIG. 8 is a table showing the results of performance tests of the tire according to the embodiment of the present invention. [Figure 9] FIG. 9 is an explanatory diagram showing the conventional test tire shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The present invention will be described in detail below with reference to the drawings. Note that the present invention is not limited to the embodiments. The components of the embodiments include those that can be substituted and are obvious substitutes while maintaining the identity of the invention. The multiple modified examples described in the embodiments can be arbitrarily combined within the scope of what is obvious to those skilled in the art.

[0011] [tire] Fig. 1 is a cross-sectional view in the tire meridian direction showing a tire 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 racing used both on public roads and on circuits will be described as an example of a tire.

[0012] 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 measurement points specified by JATMA and is perpendicular to the tire rotation axis. The tire width direction is defined as a direction parallel to the tire rotation axis, and the tire radial direction is defined as a direction perpendicular to the tire rotation axis.

[0013] Additionally, the vehicle width direction inner side and vehicle width direction outer side are defined as the directions relative to the vehicle width direction when the tire is mounted on a vehicle. Additionally, the left and right regions bounded by the tire equatorial plane are defined as the vehicle width direction outer region and the vehicle width direction inner region, respectively. Additionally, the tire is provided with a mounting direction indicator (not shown) that indicates the tire mounting direction on the vehicle. The mounting direction indicator is formed, for example, by a mark or unevenness provided on the sidewall portion of the tire. For example, ECER30 (Article 30 of the Economic Commission for Europe Regulation) requires that a vehicle mounting direction indicator be provided on the sidewall portion that is on the vehicle width direction outer side when mounted on the vehicle.

[0014] 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, a pair of rim cushion rubbers 17, 17, and an inner liner 18 (see Figure 1).

[0015] The pair of bead cores 11, 11 are formed by winding one or more steel bead wires in an annular manner in multiple layers, 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.

[0016] 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 stretched 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 envelop 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 with respect to the tire circumferential direction) of 80 degrees or more and 100 degrees or less.

[0017] 1, the carcass layer 13 has a multi-layer structure formed by laminating two carcass plies 131 and 132. However, the present invention is not limited to this, and the carcass layer 13 may be formed by laminating three or more carcass plies, or may have a single-layer structure formed by one carcass ply (not shown).

[0018] 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 pair of belt covers 143, 143.

[0019] The pair of cross belts 141, 142 are formed by covering a plurality of belt cords made of steel or organic fiber material with coating rubber and rolling them, and have a cord angle of 15 degrees or more and 55 degrees or less in absolute value. The pair of cross belts 141, 142 have cord angles (defined as the inclination angle of the belt cords in the longitudinal direction with respect to the tire circumferential direction) of opposite signs, 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.

[0020] The belt cover 143 is configured by covering a belt cover cord made of steel or organic fiber material with a 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 a coating rubber, and is configured by winding this strip material spirally around the outer circumferential surface of the cross belts 141 and 142 several times in the tire circumferential direction. In the configuration of FIG. 1, a pair of belt covers 143, 143 are arranged to cover the left and right edge portions of the cross belts 141 and 142 from the outside in the tire radial direction. However, this is not limited to this, and a single belt cover 143 may be arranged to cover the entire area of ​​the cross belts 141 and 142 (not shown).

[0021] The tread rubber 15 is disposed on the tire radial outer periphery of the carcass layer 13 and the belt layer 14 to form the tire tread portion. A pair of sidewall rubbers 16, 16 are disposed on the tire widthwise outer sides of the carcass layer 13 to form the left and right sidewall portions. A pair of rim cushion rubbers 17, 17 extend from the tire radial inner sides of the left and right bead cores 11, 11 and the turn-up portions of the carcass layer 13 to the tire widthwise outer sides to form the rim fitting surfaces of the bead portions. The inner liner 18 is an air permeation prevention layer disposed on the tire cavity surface and covers the carcass layer 13, suppressing oxidation due to exposure of the carcass layer 13 and preventing leakage of air filled in the tire.

[0022] 1, the tire section height SH and the tire total width SW have a relationship of 0.20≦SH / SW≦0.70, and preferably a relationship of 0.30≦SH / SW≦0.60. The tire ground contact width TW and the tire total width SW have a relationship of 0.90≦TW / SW≦0.98, and preferably a relationship of 0.94≦TW / SW≦0.96. The width Wb of the wide cross belt 141 and the tire ground contact width TW have a relationship of 0.98≦Wb / TW≦1.10, and preferably a relationship of 1.00≦Wb / TW≦1.05.

[0023] The tire section height SH is half the distance between the tire outer diameter and the rim diameter, and is measured with the tire mounted on a specified rim, with a specified internal pressure applied, and in an unloaded state.

[0024] The total tire width SW is measured as the straight-line distance between the sidewalls (including all parts such as patterns and lettering on the side of the tire) when the tire is mounted on a specified rim, pressurized to the specified internal pressure, and unloaded.

[0025] 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.

[0026] 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.

[0027] The width of the belt ply is the distance between the left and right ends of each belt ply in the tire rotational axis direction, and is measured with the tire mounted on a specified rim, with a specified internal pressure applied, and in an unloaded state.

[0028] The specified rim refers to the "applicable rim" specified by JATMA, the "design rim" specified by TRA, or the "measuring rim" specified by ETRTO. The specified internal pressure refers to the "maximum air pressure" specified by JATMA, the maximum value of the "tire load limits at various cold inflation pressures" specified by TRA, or the "inflation pressures" specified by ETRTO. The specified load refers to the "maximum load capacity" specified by JATMA, the maximum value of the "tire load limits at various cold inflation pressures" specified by TRA, or the "load capacity" specified by ETRTO. 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.

[0029] [Tread surface] Fig. 2 is a plan view showing the tread surface of the tire shown in Fig. 1. Fig. 3 is a cross-sectional view showing the circumferential groove 21 (22) shown in Fig. 2. In these drawings, the tire circumferential direction refers to the direction around the tire rotation axis. Also, the symbol T is the tire ground contact edge, and the dimension symbol TW is the tire ground contact width.

[0030] 2, the tire 1 has on its tread surface first and second circumferential grooves 21, 22. In addition, as will be described later, the tire 1 does not have on its tread surface any other circumferential grooves or dimples.

[0031] The circumferential grooves 21, 22 are required to extend intermittently or continuously in the tire circumferential direction. In the configuration of Fig. 2, the first and second circumferential grooves 21, 22 each include a plurality of groove portions 211, 221 that are discontinuously arranged in a line in the tire circumferential direction, and thus extend intermittently in the tire circumferential direction.

[0032] Specifically, the multiple grooves 211 constituting the first circumferential groove 21 are discontinuously arranged in a row in the tire circumferential direction along a predetermined imaginary line X1 parallel to the tire equatorial plane CL. The distance of the center of gravity of all the grooves 211 to the imaginary line X1 (dimension symbols omitted in the drawing) is within a range of 2.0% or less of the tire ground contact width TW. In other words, a group of grooves 211 that satisfy the above distance condition to the predetermined imaginary line X1 constitutes one row of the first circumferential groove 21. The imaginary line X1 is defined as the groove center line of the first circumferential groove 21.

[0033] Similarly, the multiple grooves 221 constituting the second circumferential groove 22 are discontinuously arranged in a row in the tire circumferential direction along a predetermined imaginary line X2 parallel to the tire equatorial plane CL. The distance of the center of gravity of all the grooves 221 to the imaginary line X2 (dimension symbols omitted in the figure) is within a range of 2.0% or less of the tire ground contact width TW. In other words, a group of grooves 221 that satisfy the above distance condition to the predetermined imaginary line X2 constitutes one row of the second circumferential groove 22. The imaginary line X2 is defined as the groove center line of the second circumferential groove 22.

[0034] The distance of the center of gravity of groove portion 211 and the distance of the center of gravity of groove portion 221 are measured with the tire mounted on a specified rim, a specified internal pressure applied, and in an unloaded state.

[0035] In addition, each of the multiple grooves 211;221 constituting the circumferential groove 21;22 is arranged in a zigzag or wave shape having an amplitude Ac1;Ac2 in the tire width direction. Specifically, the multiple grooves 211;221 are arranged offset from each other in the tire width direction, so that the entire circumferential groove 21;22 extends in the tire circumferential direction while meandering in a zigzag or wave shape. For example, in the configuration of FIG. 2, adjacent grooves 211, 211;221, 221 are arranged in a staggered manner in the tire circumferential direction, so that a virtual line (not shown) connecting the centers of gravity of adjacent grooves 211;221 has a zigzag shape throughout the entire circumferential groove 21;22.

[0036] Furthermore, the amplitudes Ac1, Ac2 of the zigzag or wavy shape of the first and second circumferential grooves 21, 22 satisfy the relationships 0.010≦Ac1 / TW≦0.040 and 0.010≦Ac2 / TW≦0.040 with respect to the tire ground contact width TW.

[0037] The amplitudes Ac1 and Ac2 of the circumferential grooves 21 and 22 are measured using the maximum amplitude positions of the centers of gravity of the groove portions 211 and 221 as measurement points.

[0038] The wavelength (dimension symbols omitted in the figure) of the zigzag or wavy shape of the circumferential grooves 21, 22 is not particularly limited. However, for example, in the configuration of Figure 2, it is preferable that the wavelength of the zigzag or wavy shape is in the range of 5.0% to 8.0% of the tire circumference.

[0039] In the above configuration, (1) the circumferential grooves 21, 22 are composed of a plurality of groove portions 211, 221 arranged in a zigzag or wave shape, so that the arrangement area of ​​the groove portions in the tire width direction is expanded compared to a configuration (not shown) in which the circumferential grooves are composed of groove portions arranged in a straight line. This improves the wet performance of the tire. Also, (2) the circumferential grooves 21, 22 extend intermittently in the tire circumferential direction, so that the tire's ground contact area is increased and traction performance on dry roads is improved compared to a configuration in which the circumferential grooves 21, 22 extend continuously in the tire circumferential direction (see FIG. 5 described later). This allows the tire to achieve both dry and wet performance.

[0040] The maximum groove width W1 of the first circumferential groove 21 and the maximum groove width W2 of the second circumferential groove 22 have the relationship of 0.020≦W1 / TW≦0.080 and 0.020≦W2 / TW≦0.080 with respect to the tire ground contact width TW. The maximum groove widths W1 and W2 of the first and second circumferential grooves 21 and 22 are in the range of 4.0 mm to 16 mm, preferably 6.0 mm to 10 mm. The maximum groove widths W1 and W2 of the first and second circumferential grooves 21 and 22 have the relationship of 0.90≦W2 / W1≦1.10, preferably 0.95≦W2 / W1≦1.05.

[0041] The maximum groove width W1;W2 of the circumferential grooves 21;22 is measured as the distance between the opposing groove walls at the groove opening when the tire is mounted on a specified rim and inflated to a specified internal pressure and in an unloaded state. When the circumferential grooves 21;22 extend discontinuously in the tire circumferential direction as shown in Figure 2, the maximum groove width W1;W2 is measured as the maximum groove width of all groove portions 211;221 constituting one circumferential groove 21;22.

[0042] 3, the maximum groove depth H1 of the first circumferential groove 21 and the maximum groove depth H2 of the second circumferential groove 22 are in the range of 2.5 mm to 5.0 mm, preferably in the range of 2.8 mm to 4.0 mm. The maximum groove depths H1 and H2 of the first and second circumferential grooves 21 and 22 have a relationship of 0.90≦H2 / H1≦1.10, preferably 0.95≦H2 / H1≦1.05.

[0043] The maximum groove depth H21;H22 of the circumferential grooves 21;22 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 in a no-load state. In the case of a structure having partial unevenness or sipes at the groove bottom, the groove depth is measured excluding these.

[0044] 3, the maximum groove depths H1 and H2 of the first and second circumferential grooves 21 and 22 are in the range of 60% to 85% and preferably 63% to 70% of the gauge Gr of the tread rubber 15 on the groove centerlines of the circumferential grooves 21 and 22. The gauge Gr of the tread rubber 15 is in the range of 30% to 60% and preferably 35% to 55% of the total gauge Gt of the tread portion on the groove centerlines of the circumferential grooves 21 and 22.

[0045] The gauge Gr of the tread rubber 15 is measured as the distance from the tread profile to the outer circumferential surface of the outermost belt layer 142, and does not include the gauge of the coat rubber (not shown) of the outermost belt layer 142.

[0046] The total gauge Gt of the tread portion is measured as the distance from the tread profile to the inner surface of the tire, and does not include the gauge of partial unevenness formed on the tread surface or the inner surface of the tire.

[0047] 2, the groove area A1 of the first circumferential groove 21 and the groove area A2 of the second circumferential groove 22 (not shown) have the relationship of 0.015≦A1 / Sa≦0.100 and 0.015≦A2 / Sa≦0.100 with respect to the area Sa of the tire ground contact patch, and preferably have the relationship of 0.015≦A1 / Sa≦0.020 and 0.015≦A2 / Sa≦0.020. The groove area A1 of the first circumferential groove 21 and the groove area A2 of the second circumferential groove 22 have the relationship of 0.90≦A1 / A2≦1.10, and preferably have the relationship of 0.95≦A1 / A2≦1.05.

[0048] The groove area is the opening area of ​​the groove on the tread surface, and is measured at the contact surface between the tire and a flat plate when the tire is mounted on a specified rim, a specified internal pressure is applied, the tire is placed perpendicular to a flat plate in a stationary state, and a load corresponding to a specified load is applied. In addition, when the circumferential grooves 21;22 extend discontinuously in the tire circumferential direction as shown in Figure 2, the groove areas A1;A2 of the circumferential grooves 21;22 are calculated as the sum of the opening areas of the multiple groove portions 211;221 that constitute the circumferential grooves 21;22.

[0049] The area Sa of the tire contact area is the area of ​​the entire tread surface defined by the left and right tire contact edges T, and is defined as an area including both grooves and land portions.

[0050] 2, as described above, each of the first and second circumferential grooves 21, 22 is composed of a plurality of groove portions 211, 221 that are discontinuously arranged in a line in the tire circumferential direction. The opening areas of the groove portions 211, 221 that constitute the first and second circumferential grooves 21, 22 are each in the range of 200 mm^2 to 340 mm^2, and preferably in the range of 240 mm^2 to 300 mm^2.

[0051] It is also preferable that the tire 1 does not have any other grooves or recesses having an opening area exceeding 40 [mm^2], preferably exceeding 20 [mm^2], i.e., grooves or recesses other than the circumferential grooves 21, 22, in the tire ground contact area. In other words, the tire ground contact area may have recesses or grooves having an opening area smaller than the above condition, such as wear indicators (not shown) consisting of small holes, in the areas other than the areas where the circumferential grooves 21, 22 are arranged. The groove area ratio of the tire ground contact area is in the range of 3.0 [%] to 5.0 [%], preferably in the range of 3.2 [%] to 3.8 [%].

[0052] For example, in the configuration of FIG. 2, the tire ground contact area includes only the first and second circumferential grooves 21, 22, and a wear indicator (not shown) is formed at the bottom of the predetermined circumferential grooves 21, 22. Moreover, the area other than the area where the circumferential grooves 21, 22 are arranged has a plain tread surface without grooves or sipes. Therefore, in the configuration of FIG. 2, the groove area in the entire tire ground contact area is equal to the sum of the groove area A1 of the first circumferential groove 21 and the groove area A2 of the second circumferential groove 22. Moreover, the groove area ratio of the tire ground contact area is in the range of 0.030≦(A1+A2) / Sa≦0.200.

[0053] The groove area ratio is defined as the ratio of the total area of ​​grooves arranged in a given region to the area of ​​that region.

[0054] 2, the pitch lengths P1, P2 of the groove portions 211, 211; 221, 221 adjacent in the tire circumferential direction have the relationships of 0.030≦P1 / TL≦0.060 and 0.030≦P2 / TL≦0.060 with respect to the tire circumferential length TL (not shown). The pitch length P1 of the groove portion 211 of the first circumferential groove 21 and the pitch length P2 of the groove portion 221 of the second circumferential groove 22 have the relationship of 0.90≦P1 / P2≦1.10, and preferably have the relationship of 0.95≦P1 / P2≦1.05.

[0055] The tire circumference TL is measured as the maximum circumference of the tread surface when the tire is mounted on a specified rim, pressurized to a specified internal pressure, and under no load.

[0056] 2, the maximum circumferential length L1 of the groove portion 211 of the first circumferential groove 21 and the maximum circumferential length L2 of the groove portion 221 of the second circumferential groove 22 have a relationship of 0.30≦L1 / P1≦0.60 and 0.30≦L2 / P2≦0.60 with respect to the pitch length P1 of the groove portion 211 of the first circumferential groove 21 and the pitch length P2 of the groove portion 221 of the second circumferential groove 22, and preferably have a relationship of 0.45≦L1 / P1≦0.55 and 0.45≦L2 / P2≦0.55. The maximum circumferential length L1 of the groove portion 211 of the first circumferential groove 21 and the maximum circumferential length L2 of the groove portion 221 of the second circumferential groove 22 have a relationship of 0.90≦L2 / L1≦1.10 and preferably have a relationship of 0.95≦L2 / L1≦1.05.

[0057] The maximum circumferential lengths L1; L2 of the groove portions 211; 221 of the circumferential grooves 21; 22 are measured as the circumferential distance at the groove opening when the tire is mounted on a specified rim and inflated to a specified internal pressure in an unloaded state.

[0058] In addition, in FIG. 2 , the maximum circumferential length L1 of groove portion 211 of first circumferential groove 21 and the maximum circumferential length L2 of groove portion 221 of second circumferential groove 22 have a relationship of 2.00≦L1 / W1≦8.00 and 2.00≦L2 / W2≦8.00 with respect to the maximum groove width W1 of first circumferential groove 21 and the maximum groove width W2 of second circumferential groove 22, respectively, and preferably have a relationship of 4.00≦L1 / W1≦6.00 and 4.00≦L2 / W2≦6.00.

[0059] In addition, in Figure 2, the phase difference φ between the groove portion 211 of the first circumferential groove 21 and the groove portion 221 of the second circumferential groove 22 has a relationship of 0.25≦φ / P1≦0.75 with respect to the pitch length P1 of the groove portion 211 of the first circumferential groove 21, and preferably has a relationship of 0.40≦φ / P1≦0.50.

[0060] For example, in the configuration of FIG. 2, the grooves 211 and 221 have a rectangular or elliptical shape that is elongated in the tire circumferential direction. The grooves 211 of the first circumferential groove 21 and the grooves 221 of the second circumferential groove 22 are arranged in a staggered manner in the tire circumferential direction. Specifically, the pitch number of the grooves 211 of the first circumferential groove 21 and the pitch number of the grooves 221 of the second circumferential groove 22 are set to be the same, and the maximum circumferential length L1 of the grooves 211 of the first circumferential groove 21 and the maximum circumferential length L2 of the grooves 221 of the second circumferential groove 22 are set to 50[%] of the pitch length P1 of the grooves 211 of the first circumferential groove 21 and the pitch length P2 of the grooves 221 of the second circumferential groove 22. The phase difference φ between the grooves 211 of the first circumferential groove 21 and the grooves 221 of the second circumferential groove 22 is set to about 50[%] of the pitch length P1 of the grooves 211 of the first circumferential groove 21.

[0061] 2, the first circumferential groove 21 is disposed in an area on the outer side in the vehicle width direction, with the tire equatorial plane CL as the boundary, and the second circumferential groove 22 is disposed in an area on the inner side in the vehicle width direction. Also, the distance D1 from the tire equatorial plane CL to the groove center line X1 of the first circumferential groove 21 and the distance D2 from the tire equatorial plane CL to the groove center line X2 of the second circumferential groove 22 are approximately equal. Therefore, the first and second circumferential grooves 21 and 22 are disposed at approximately the same position with respect to the tire equatorial plane CL. Also, the distance D1 of the first circumferential groove 21 and the distance D2 of the second circumferential groove 22 have a relationship of 0.90≦D2 / D1≦1.10, and preferably have a relationship of 0.95≦D2 / D1≦1.05.

[0062] 2, the distances D1 and D2 from the tire equatorial plane CL to the groove centerlines X1 and X2 of the first and second circumferential grooves 21 and 22 have the relationship of 0.05≦D1 / TW≦0.45 and 0.05≦D2 / TW≦0.45 with respect to the tire ground contact width TW, and preferably have the relationship of 0.10≦D1 / TW≦0.25 and 0.10≦D2 / TW≦0.25. The distance Dg in the tire width direction between the groove centerline X1 of the first circumferential groove 21 and the groove centerline X2 of the second circumferential groove 22 has the relationship of 0.10≦Dg / TW with respect to the tire ground contact width TW, and preferably has the relationship of 0.20≦Dg / TW. The upper limit of the ratio Dg / TW is not particularly limited, but is restricted by other conditions.

[0063] The distances D1, D2 and Dg are measured with the tire mounted on a specified rim, with a specified internal pressure applied, and under no load.

[0064] [Variation 1] Fig. 4 is an explanatory diagram showing a modified example of the tire shown in Fig. 2. In this figure, the same components as those in Fig. 2 are given the same reference numerals, and the description thereof will be omitted.

[0065] In the configuration of FIG. 2, the multiple groove portions 211 constituting the first circumferential groove 21 are arranged at a predetermined pitch length P1 (defined as the pitch length between adjacent groove portions 211, 211 in the tire circumferential direction, as described above) around the entire circumference of the tire, and the multiple groove portions 221 constituting the second circumferential groove 22 are arranged at a predetermined pitch length P2 around the entire circumference of the tire. Also, the first and second groove portions 211, 221 are arranged in a staggered manner in the tire circumferential direction with a predetermined phase difference φ. This configuration is preferable in that it can improve wet performance while maintaining the tire's traction performance.

[0066] In contrast, in the configuration of FIG. 4, the first circumferential groove 21 has a first groove unit U1 consisting of three or more groove portions 211 arranged at a predetermined pitch length P1 in the tire circumferential direction, and the first groove units U1 are arranged at a predetermined pitch length P1' in the tire circumferential direction. Similarly, the second circumferential groove 22 has a second groove unit U2 consisting of three or more groove portions 221 arranged at a predetermined pitch length P2 in the tire circumferential direction, and the second groove units U2 are arranged at a predetermined pitch length P2' in the tire circumferential direction. The first and second groove units U1 and U2 are arranged in a staggered pattern in the tire circumferential direction with a predetermined phase difference φ'. This configuration is preferable in that it can improve the traction performance while maintaining the wet performance of the tire.

[0067] 4, the pitch length P1' of the first groove unit U1 and the pitch length P2' of the second groove unit U2 have the relationship of 0.10≦P1' / TL≦0.30 and 0.10≦P2' / TL≦0.30 with respect to the tire circumference TL (not shown). The pitch length P1' of the first groove unit U1 and the pitch length P2' of the second groove unit U2 have the relationship of 0.90≦P1' / P2'≦1.10, and preferably have the relationship of 0.95≦P1' / P2'≦1.05.

[0068] 4, the maximum circumferential length L1' of the first groove unit U1 and the maximum circumferential length L2' of the second groove unit U2 have the relationship of 0.050≦L1' / TL≦0.100 and 0.050≦L2' / TL≦0.100 relative to the tire circumference TL (not shown). The maximum circumferential length L1' of the first groove unit U1 and the maximum circumferential length L2' of the second groove unit U2 have the relationship of 0.90≦L2' / L1'≦1.10, and preferably have the relationship of 0.95≦L2' / L1'≦1.05.

[0069] In addition, in FIG. 4, the maximum circumferential length L1' of the first groove unit U1 and the maximum circumferential length L2' of the second groove unit U2 have the relationships of 0.30≦L1' / P1'≦0.60 and 0.30≦L2' / P2'≦0.60 with respect to the pitch length P1' of the first groove unit U1 and the pitch length P2' of the second groove unit U2, and preferably have the relationships of 0.45≦L1' / P1'≦0.55 and 0.45≦L2' / P2'≦0.55.

[0070] In FIG. 4, the phase difference φ' between the first groove unit U1 and the second groove unit U2 and the pitch length P1' of the first groove unit U1 satisfies the relationship 0.25≦φ' / P1'≦0.75, and preferably 0.40≦φ' / P1'≦0.50.

[0071] The wavelength (dimension symbols omitted in the figure) of the zigzag or wavy shape of the circumferential grooves 21, 22 in the groove units U1, U2 is not particularly limited. However, for example, in the configuration of Figure 5, it is preferable that the wavelength of the zigzag or wavy shape is in the range of 5.0% or more and 8.0% or less of the tire circumference.

[0072] [Variation 2] Fig. 5 is an explanatory diagram showing a modified example of the tire shown in Fig. 2. In this figure, the same components as those in Fig. 2 are given the same reference numerals, and the description thereof will be omitted.

[0073] 2, as described above, the first and second circumferential grooves 21, 22 are each composed of a plurality of groove portions 211, 221 that are discontinuously arranged in a line in the tire circumferential direction. This configuration is preferable in that the tire's ground contact area is increased, thereby improving the traction performance while maintaining the tire's wet performance.

[0074] In contrast, in the configuration of Fig. 5, the first and second circumferential grooves 21, 22 each extend continuously in the tire circumferential direction. This configuration is preferable in that the groove area of ​​the tire is increased compared to the configuration of Fig. 2, and wet performance can be improved while maintaining the traction performance of the tire.

[0075] In the configuration of FIG. 5, the amplitudes Ac1; Ac2 of the circumferential grooves 21; 22 are measured at maximum amplitude positions on imaginary lines X1'; X2' connecting the midpoints of opposing wall surfaces at the groove openings of the circumferential grooves 21; 22.

[0076] In addition, the wavelength (dimension symbols omitted in the figure) of the zigzag or wavy shape of the circumferential grooves 21, 22 is not particularly limited, but for example, in the configuration of Figure 5, it is preferable that the wavelength of the zigzag or wavy shape is in the range of 5.0% or more and 8.0% or less of the tire circumference.

[0077] Fig. 6 is an explanatory diagram showing a modified example of the tire shown in Fig. 2. In this figure, the same components as those in Fig. 2 are given the same reference numerals, and the description thereof will be omitted.

[0078] 2, as described above, the amplitudes Ac1, Ac2 of the first and second circumferential grooves 21, 22 are set to be substantially the same. Specifically, the amplitudes Ac1, Ac2 of the circumferential grooves 21, 22 have a relationship of 0.90≦Ac2 / Ac1<1.10, and preferably have a relationship of 0.95≦Ac2 / Ac1≦1.05.

[0079] In contrast, in the configuration of FIG. 6, the amplitude Ac2 of the second circumferential groove 22 on the inner side in the vehicle width direction has a relationship of Ac1 < Ac2 with respect to the amplitude Ac1 of the first circumferential groove 21 on the outer side in the vehicle width direction. Also, the amplitudes Ac1 and Ac2 of the first and second circumferential grooves 21 and 22 preferably have a relationship of 1.10 ≦ Ac2 / Ac1 and a relationship of 1.20 ≦ Ac2 / Ac1. In such a configuration, since the amplitude Ac2 of the second circumferential groove 22 in the inner region in the vehicle width direction is large, the arrangement region of the groove portion 221 in the inner region in the vehicle width direction is expanded. Thereby, the wet performance of the tire is improved. Alternatively, since the amplitude Ac1 of the first circumferential groove 21 in the outer region in the vehicle width direction is small, the arrangement region of the groove portion 211 in the outer region in the vehicle width direction is reduced. Thereby, the traction performance of the tire is improved.

[0080] [Effect] As described above, this tire 1 includes a pair of circumferential grooves 21 and 22 that are arranged in the left and right regions with the tire equatorial plane CL as a boundary and extend intermittently in the tire circumferential direction (see FIGS. 2 and 4). Further, each of the pair of circumferential grooves 21 and 22 is composed of a plurality of groove portions 211 and 221 arranged in a zigzag shape or a wavy shape having an amplitude in the tire width direction.

[0081] In such a configuration, (1) since the circumferential grooves 21 and 22 are composed of a plurality of groove portions 211 and 221 arranged in a zigzag shape or a wavy shape, the arrangement region of the groove portions in the tire width direction is expanded as compared with a configuration in which the circumferential grooves are composed of groove portions arranged linearly (not shown). Thereby, the wet performance of the tire is improved. Also, (2) since the circumferential grooves 21 and 22 extend intermittently in the tire circumferential direction, the contact area of the tire increases as compared with a configuration in which the circumferential grooves 21 and 22 extend continuously in the tire circumferential direction (see FIG. 5), and the traction performance on a dry road surface is improved and the dry performance of the tire is improved. Thereby, there is an advantage that the dry performance and the wet performance of the tire are compatible.

[0082] In addition, in the tire 1, the amplitudes Ac1, Ac2 of the zigzag or wavy shape of the pair of circumferential grooves 21, 22 are in the range of 1.0% to 4.0% of the tire ground contact width. The lower limit has the advantage of properly ensuring the improvement of the wet performance of the tire due to the circumferential grooves 21, 22 having the amplitudes Ac1, Ac2. The upper limit has the advantage of suppressing the deterioration of the traction performance of the tire caused by the amplitudes Ac1, Ac2 of the circumferential grooves 21, 22 being too large.

[0083] In addition, in the tire 1, the pitch lengths P1, P2 of the groove portions 211, 221 adjacent to each other in the tire circumferential direction are in the range of 3.0% to 6.0% of the tire circumference TL (dimension symbols omitted in the drawing). This has the advantage that the pitch lengths P1, P2 of the groove portions 211, 221 are optimized (see FIG. 2).

[0084] In addition, in this tire 1, the maximum circumferential lengths L1, L2 of the groove portions 211, 221 of the pair of circumferential grooves 21, 22 are in the range of 30% to 60% of the pitch lengths P1, P2 of the groove portions 211, 221 of the circumferential grooves 21, 22 (see FIG. 2). The lower limit has the advantage of properly ensuring the improvement of the wet performance of the tire by the circumferential grooves 21, 22. The upper limit has the advantage of ensuring the improvement of the traction performance of the tire by the circumferential grooves 21, 22 extending intermittently in the tire circumferential direction.

[0085] In addition, in the tire 1, the maximum groove widths W1, W2 of the circumferential grooves 21, 22 are in the range of 2% to 8% of the tire ground contact width TW (see FIG. 2). The lower limit has the advantage of ensuring the drainage of the circumferential grooves 21, 22. The upper limit has the advantage of suppressing deterioration of traction performance caused by the circumferential grooves 21, 22 becoming excessively wide.

[0086] In addition, in the tire 1, the maximum groove depths H1, H2 of the pair of circumferential grooves 21, 22 are in the range of 2.5 mm or more and 5.0 mm or less. This has the advantage that the maximum groove depths H1, H2 of the circumferential grooves 21, 22 are optimized.

[0087] Further, in this tire 1, the groove areas A1 and A2 of the pair of circumferential grooves 21 and 22 are in the range of 2.0% or more and 10% or less with respect to the area Sa of the tire contact region. Thereby, there is an advantage that the groove areas A1 and A2 of the circumferential grooves 21 and 22 are optimized.

[0088] Further, in this tire 1, there are no other grooves or recesses having an opening area exceeding 40 [mm^2] in the tire contact region (see FIG. 2). Thereby, there is an advantage that the contact area of the tire is ensured and the above-described effect of improving the traction performance of the tire is properly ensured.

[0089] Further, in this tire 1, the groove area ratio of the tire contact region is in the range of 3.0% or more and 5.0% or less. Thereby, there is an advantage that the traction performance of the tire, particularly for a racing tire, is ensured.

[0090] Further, in this tire 1, the ratio Ac2 / Ac1 of the amplitudes Ac1 and Ac2 of the pair of circumferential grooves 21 and 22 is in the range of 90% or more and 110% or less. Thereby, there is an advantage that the amplitudes Ac1 and Ac2 of the circumferential grooves 21 and 22 are set substantially the same, and uneven wear of the tire is suppressed.

[0091] Further, this tire 1 is provided with a mounting direction display portion (not shown) indicating the tire mounting direction with respect to the vehicle. Further, the amplitude Ac2 of the circumferential groove 22 on the inner side in the vehicle width direction among the pair of circumferential grooves 21 and 22 has a relationship of Ac1 < Ac2 with respect to the amplitude Ac1 of the circumferential groove 21 on the outer side in the vehicle width direction (see FIG. 6). In such a configuration, since the amplitude Ac2 of the circumferential groove 22 in the inner region in the vehicle width direction is large, the arrangement region of the groove portion 221 in the inner region in the vehicle width direction is expanded. Thereby, there is an advantage that the wet performance of the tire is improved. Alternatively, since the amplitude Ac1 of the circumferential groove 21 in the outer region in the vehicle width direction is small, the arrangement region of the groove portion 211 in the outer region in the vehicle width direction is reduced. Thereby, there is an advantage that the traction performance of the tire is improved.

[0092] The tire 1 also includes a pair of circumferential grooves 21, 22 that are disposed in left and right regions bounded by the tire equatorial plane CL and extend continuously in the tire circumferential direction (see FIG. 5). Each of the pair of circumferential grooves 21, 22 has a zigzag or wave shape with amplitude in the tire width direction.

[0093] In this configuration, (1) the circumferential grooves 21, 22 have a zigzag or wavy shape, so that the arrangement area of ​​the circumferential grooves 21, 22 in the tire width direction is expanded compared to a configuration in which the circumferential grooves are linear (see FIG. 9), which has the advantage of improving the wet performance of the tire. Also, (2) the circumferential grooves 21, 22 extend continuously in the tire circumferential direction, so that the wet performance of the tire is further improved compared to a configuration in which the circumferential grooves 21, 22 extend intermittently in the tire circumferential direction (see FIG. 2).

[0094] In addition, in this tire 1, the tire section height SH and the tire total width SW have a relationship of 0.20≦SH / SW≦0.70, and the tire contact width TW and the tire total width SW have a relationship of 0.90≦TW / SW≦0.98 (see FIG. 1). This has the advantage that the aspect ratio SH / SW and tire contact width TW of the tire are optimized.

[0095] The tire 1 includes a pair of bead cores 11, 11, a carcass layer 13 stretched across the pair of bead cores 11, 11, a pair of cross belts 141, 142 arranged on the outer periphery of the carcass layer 13, and a tread rubber 15 arranged radially outside the cross belts 141, 142 (see FIG. 1). The width Wb of the wider cross belt of the pair of cross belts 141, 142 (the cross belt 141 on the inner diameter side in FIG. 1) has a relationship of 0.98≦Wb / TW≦1.10 with the tire contact width TW. This has the advantage of ensuring the durability of the tire appropriately.

[0096] The tire 1 includes a pair of bead cores 11, 11, a carcass layer 13 stretched across the pair of bead cores 11, 11, a pair of cross belts 141, 142 arranged on the outer periphery of the carcass layer 13, and a tread rubber 15 arranged radially outward of the cross belts 141, 142 (see FIG. 1). The gauge Gr of the tread rubber 15 is in the range of 30% to 60% of the total gauge Gt of the tread portion on the groove center lines of the first and second circumferential grooves 21, 22 (see FIG. 3). This has the advantage of optimizing the gauge Gr of the tread rubber 15. EXAMPLES

[0097] 7 and 8 are tables showing the results of performance tests of the tires according to the embodiment of the present invention, and FIG 9 is an explanatory view showing the conventional test tire shown in FIG 7.

[0098] In this performance test, several types of test tires were evaluated for (1) dry performance and (2) wet performance. Test tires with tire size P205 / 50R15 84W were mounted on JATMA-specified rims and installed on all wheels of a test vehicle, a four-wheeled passenger car weighing 990 kg. The test tires were pressurized to 160 kPa in cold conditions and 220 kPa in warm conditions.

[0099] (1) In the evaluation of dry performance, the test vehicle completes four laps of a specified circuit of 3.7 km in clear skies with a road surface temperature of 18°C ​​and an air temperature of 28°C, and the lap time is measured. The best lap time is then used to perform an index evaluation with the conventional example as the standard (100). The higher the value, the better.

[0100] (2) In the evaluation of wet performance, the test vehicle makes four laps of a specified circuit with 1mm of water sprayed on it, and the lap time is measured. The best lap time is then used to perform an index evaluation with the conventional example as the standard (100). The higher the evaluation value, the better. Also, an evaluation of 99 or higher can be said to indicate that the performance is adequately maintained.

[0101] The test tire of the embodiment has the configuration of Figs. 1 to 3, the first circumferential groove 21 is arranged in an area on the outer side in the vehicle width direction with the tire equatorial plane CL as a boundary, and the second circumferential groove 22 is arranged in an area on the inner side in the vehicle width direction. The first and second circumferential grooves 21, 22 each consist of a plurality of groove portions 211, 221 arranged discontinuously in a line in the tire circumferential direction. The tire outer diameter is 586 [mm], the tire cross-sectional height SH is 103 [mm], the tire total width SW is 216 [mm], the tire ground contact width TW is 202 [mm], and the belt width Wb of the wide cross belt 142 is 203 [mm]. The gauge Gr of the tread rubber 15 on the groove center lines X1, X2 of the circumferential grooves 21, 22 is in the range of 4.0 [mm] to 4.7 [mm], and the total gauge Gt of the tread portion is in the range of 10 [mm] to 11 [mm]. The groove widths W1 and W2 of the first and second circumferential grooves 21 and 22 are in the relationship of W1=W2, and the groove depths H1 and H2 are in the relationship of H1=H2=3.3 mm. The distances D1 and D2 of the circumferential grooves 21 and 22 and the tire contact width TW are in the relationship of D1 / TW=D2 / TW=0.25.

[0102] The conventional test tire has the configuration shown in FIG. 9, and differs from the test tire of Example 1 in that the first and second circumferential grooves have a straight shape that extends continuously in the tire circumferential direction.

[0103] As the test results show, the test tires of the examples have both good dry performance and good wet performance. [Explanation of symbols]

[0104] 1 tire; 11 bead core; 12 bead filler; 13 carcass layer; 131, 132 carcass ply; 14 belt layer; 141, 142 cross belt; 143 belt cover; 15 tread rubber; 16 sidewall rubber; 17 rim cushion rubber; 18 inner liner; 21 first circumferential groove; 211 groove portion; 22 second circumferential groove; 221 groove portion

Claims

1. A pair of circumferential grooves are disposed in left and right regions bounded by a tire equatorial plane and extend intermittently in a tire circumferential direction, Each of the pair of circumferential grooves is composed of a plurality of groove portions arranged in a zigzag shape or a wave shape having amplitude in the tire width direction, and A tire characterized in that the amplitude of the zigzag shape or the wavy shape of the pair of circumferential grooves is in the range of 1.0% to 4.0% of the tire ground contact width.

2. The tire according to claim 1 , wherein a pitch length of the groove portions adjacent to each other in the tire circumferential direction is in a range of 3.0% to 6.0% of the tire circumference.

3. 3. The tire according to claim 1, wherein a circumferential length of the groove portions of the pair of circumferential grooves is in a range of 30% to 60% of a pitch length of the groove portions.

4. The tire according to any one of claims 1 to 3, wherein a maximum groove width of the pair of circumferential grooves is in a range of 2% to 8% of the tire ground contact width TW.

5. The tire according to any one of claims 1 to 4, wherein the pair of circumferential grooves have a maximum groove depth in the range of 2.5 mm or more and 5.0 mm or less.

6. 6. The tire according to claim 1, wherein the groove area of ​​the pair of circumferential grooves is in the range of 2.0% to 10% of the area of ​​the tire ground contact area.

7. The tire according to any one of claims 1 to 6, wherein the tire contact area does not include any other groove or recess having an opening area exceeding 40 [mm^2].

8. 8. The tire according to claim 1, wherein a groove area ratio of the tire ground contact region is in the range of 3.0% or more and 5.0% or less.

9. The tire according to any one of claims 1 to 8, wherein a ratio of the amplitudes of the pair of circumferential grooves is in a range of 90% or more and 110% or less.

10. A mounting direction indicator is provided to indicate the direction in which the tire is mounted on the vehicle, and The tire according to any one of claims 1 to 9, wherein an amplitude Ac2 of the circumferential groove located on an inner side in the vehicle width direction of the pair of circumferential grooves has a relationship of Ac1<Ac2 with respect to an amplitude Ac1 of the circumferential groove located on an outer side in the vehicle width direction.

11. The tire according to any one of claims 1 to 10, wherein the tire section height SH and the tire total width SW have a relationship of 0.20≦SH / SW≦0.70, and the tire ground contact width TW and the tire total width SW have a relationship of 0.90≦TW / SW≦0.

98.

12. A tire comprising: a pair of bead cores; a carcass layer disposed around the pair of bead cores; a pair of cross belts disposed on an outer periphery of the carcass layer; and a tread rubber disposed radially outward of the cross belts; The tire according to any one of claims 1 to 11, wherein a width Wb of the wider cross belt of the pair of cross belts satisfies a relationship of 0.98≦Wb / TW≦1.10 with respect to a tire ground contact width TW.

13. A tire comprising: a pair of bead cores; a carcass layer disposed around the pair of bead cores; a pair of cross belts disposed on an outer periphery of the carcass layer; and a tread rubber disposed radially outward of the cross belts; The tire according to any one of claims 1 to 12, wherein the gauge of the tread rubber is in the range of 30% to 60% of the total gauge of the tread portion on the groove center lines of the first and second circumferential grooves.

14. A pair of circumferential grooves are disposed in left and right regions bounded by a tire equatorial plane and extend intermittently in a tire circumferential direction, Each of the pair of circumferential grooves is composed of a plurality of groove portions arranged in a zigzag shape or a wave shape having amplitude in the tire width direction, and A tire characterized in that the pitch length of the groove portions adjacent to each other in the tire circumferential direction is in the range of 3.0% to 6.0% of the tire circumference.

15. A pair of circumferential grooves are disposed in left and right regions bounded by a tire equatorial plane and extend intermittently in a tire circumferential direction, Each of the pair of circumferential grooves is composed of a plurality of groove portions arranged in a zigzag shape or a wave shape having amplitude in the tire width direction, and A tire characterized in that a groove area ratio of the tire ground contact region is in the range of 3.0% or more and 5.0% or less.

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