tire

Abstract

To provide a tire that has noise performance upgraded while maintaining on-snow performance.SOLUTION: A tire has a tread 2. The tread 2 includes plural circumferential grooves 3 and plural land parts. The plural land parts include a crown land part 10 and a first middle land part 11. The crown land part 10 has plural crown lateral grooves 15. The first middle land part 11 has plural first middle lateral grooves 20. In a plan view of the tread, an angle between a first straight line 21 linking both ends of the crown lateral groove 15 and a second straight line 22 linking both ends of the first middle lateral groove 20 falls in between 90 to 150°. The crown lateral groove 15 includes a first end 16, a second end 17, and a center part 18. A groove width in the center part 18 is smaller than those of the first end 16 and second end 17.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a tire. [Background technology]

[0002] Patent Document 1 below proposes a tire with multiple lug grooves in the center land portion and the middle land portion, which is expected to improve driving stability while suppressing deterioration of snowy and icy road performance. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-056814 A Summary of the Invention [Problem to be solved by the invention]

[0004] In general, the tread of a tire designed for running on snow tends to have circumferential grooves that extend continuously around the tire and lateral grooves that are inclined with respect to the tire axial direction. When running on snow, the tire packs and shears the snow inside the circumferential grooves and lateral grooves, generating snow column shear force and ensuring on-snow performance.

[0005] In order to increase the shear force on snow, it is possible to increase the number of connecting parts between the circumferential grooves and the lateral grooves, or to increase the volume of these grooves. However, such methods may lead to a deterioration in noise performance. Meanwhile, in recent years, the level of requirements for various tire performances has been increasing, and even tires designed for driving on snow are required to have improved noise performance.

[0006] The present invention has been devised in view of the above circumstances, and has as its main object to provide a tire which maintains its performance on snow while improving its noise performance. [Means for solving the problem]

[0007] The present invention relates to a tire having a tread portion, the tread portion including a plurality of circumferential grooves extending continuously in a tire circumferential direction between a first tread edge and a second tread edge, and a plurality of land portions divided by the circumferential grooves, the plurality of land portions including a crown land portion and a first middle land portion adjacent to the crown land portion on the first tread end side via the circumferential groove, the crown land portion being provided with a plurality of crown lateral grooves inclined in a first direction with respect to the tire axial direction and completely crossing the crown land portion in the tire axial direction, and the first middle land portion being provided with a plurality of crown lateral grooves inclined in a first direction with respect to the tire axial direction and completely crossing the crown land portion in the tire axial direction, the first middle land portion is provided with a plurality of first middle lateral grooves that are inclined in a second direction opposite to the first direction with respect to the tire axial direction and completely cross the first middle land portion in the tire axial direction, and in a plan view of the tread, an angle between a first straight line connecting both ends of the crown lateral grooves and a second straight line connecting both ends of the first middle lateral grooves is 90 to 150°, the crown lateral grooves include first and second end ends in the tire axial direction and a central portion disposed between the first end and the second end, and a groove width of the central portion is smaller than the groove width of the first end and the groove width of the second end.

[0008] In the tire of the present invention, it is desirable that the maximum groove width in the central portion is 15% or less of the maximum groove width in the first end portion and the second end portion.

[0009] In the tire of the present invention, it is preferable that a mounting direction on a vehicle is specified, and the first tread edge is located on the inner side of the vehicle when mounted on the vehicle.

[0010] In the tire of the present invention, it is preferable that an angle of the second straight line with respect to the tire axial direction is smaller than an angle of the first straight line with respect to the tire axial direction.

[0011] In the tire of the present invention, it is desirable that the crown lateral groove and the first middle lateral groove are adjacent to each other in the tire axial direction, so that, in a plan view of the tread, the first straight line and the second straight line intersect within the circumferential groove between the crown land portion and the first middle land portion.

[0012] In the tire of the present invention, in a meridian cross section including the tire rotation axis in a normal state in which the tire is mounted on a normal rim with normal internal pressure and no load, the tread surface of the crown land portion and the tread surface of the first middle land portion each preferably have a profile that is curved convexly outward in the radial direction of the tire.

[0013] In the tire of the present invention, the land ratio of the crown land portion is desirably 65% ​​to 75%.

[0014] In the tire of the present invention, it is preferable that the tread portion includes a first shoulder land portion including the first tread edge, and the land ratio of the first shoulder land portion is larger than the land ratio of the crown land portion.

[0015] In the tire of the present invention, it is preferable that the tread portion includes a first shoulder land portion including the first tread edge, and that a land ratio of the first shoulder land portion is 75% to 85%.

[0016] In the tire of the present invention, it is desirable that the tread portion includes a second shoulder land portion including the second tread end, and that the second shoulder land portion is provided with a plurality of second shoulder lateral grooves extending at least from the second tread end toward the axially inner side of the tire and terminated within the second shoulder land portion.

[0017] In the tire of the present invention, it is preferable that the second shoulder lateral groove includes a main body portion on the second tread end side, and an inner end portion that is continuous with the main body portion on the axially inner side of the tire and has a groove width smaller than that of the main body portion.

[0018] In the tire of the present invention, the groove width of the inner end portion is desirably 3% to 15% of the groove width of the main body portion. Effect of the Invention

[0019] By adopting the above-mentioned configuration, the tire of the present invention can improve noise performance while maintaining performance on snow. [Brief description of the drawings]

[0020] [Figure 1] 1 is a development view of a tread portion of a tire according to one embodiment of the present invention. [Diagram 2] 2 is an enlarged view of a crown land portion and a first middle land portion of FIG. [Diagram 3] 3 is an enlarged view of a crown lateral groove and a first middle lateral groove shown in FIG. 2. [Figure 4] FIG. [Diagram 5] FIG. 2 is an enlarged view of the second middle land portion of FIG. [Figure 6] FIG. 2 is an enlarged view of a first shoulder land portion of FIG. [Figure 7] FIG. 2 is an enlarged view of the second shoulder land portion of FIG. [Figure 8] FIG. 4 is an enlarged view of a crown land portion and a first middle land portion of a comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a development view of a tread portion 2 of a tire 1 of this embodiment. As shown in Fig. 1, the tire 1 of this embodiment is used, for example, as a pneumatic tire for passenger cars intended for use in winter. However, the tire 1 of the present invention is not limited to this embodiment.

[0022] The tire 1 of this embodiment has a tread portion 2 in which the mounting direction on a vehicle is specified, for example. The mounting direction on a vehicle is indicated, for example, by characters or marks on the sidewall portion (not shown). In addition, the tread portion 2 is configured, for example, in an asymmetric pattern (meaning that the tread pattern is not line-symmetric with respect to the tire equator C).

[0023] The tread portion 2 includes a first tread edge T1 that is located on the inside of the vehicle when mounted on the vehicle, and a second tread edge T2 that is located on the outside of the vehicle when mounted on the vehicle. The first tread edge T1 and the second tread edge T2 each correspond to the axially outermost contact positions when the tire 1 in a normal state is loaded with a normal load and contacts a flat surface with a camber angle of 0°.

[0024] "Normal condition" means, in the case of a pneumatic tire for which various standards are established, that the tire is mounted on a normal rim, inflated to the normal internal pressure, and no load is applied. In the case of a tire for which various standards are not established or a non-pneumatic tire, the normal condition means a standard use condition according to the intended use of the tire, and a state in which no load is applied. In this specification, unless otherwise specified, the dimensions of each part of the tire are values ​​measured in the normal condition.

[0025] A "genuine rim" is a rim that is defined for each tire by the standard system that includes the standard on which the tire is based. For example, in the case of JATMA, it is called a "standard rim," in the case of TRA, it is called a "Design Rim," and in the case of ETRTO, it is called a "Measuring Rim."

[0026] "Normal internal pressure" is the air pressure set for each tire by each standard in the standard system on which the tire is based. In the case of JATMA, it is the "maximum air pressure." In the case of TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES." In the case of ETRTO, it is the "INFLATION PRESSURE."

[0027] In the case of a pneumatic tire for which various standards are established, the "normal load" is the load that each standard specifies for each tire in the standard system including the standard on which the tire is based. For JATMA, it is the "maximum load capacity", for TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and for ETRTO, it is the "LOAD CAPACITY". In addition, in the case of a tire for which various standards are not established or a non-pneumatic tire, the "normal load" refers to the load acting on one tire in the standard mounting state of the tire. The "standard mounting state" refers to a state in which the tire is mounted on a standard vehicle according to the intended use of the tire, and the vehicle is stationary on a flat road surface in a drivable state.

[0028] The tread portion 2 includes a plurality of circumferential grooves 3 extending continuously in the tire circumferential direction between the first tread edge T1 and the second tread edge T2, and a plurality of land portions divided by the circumferential grooves 3. The tire 1 of this embodiment is configured as a so-called five-rib tire in which the tread portion 2 includes five land portions divided by four circumferential grooves 3. However, the present invention is not limited to this embodiment, and for example, the tire may be a so-called four-rib tire in which the tread portion 2 is configured by three circumferential grooves 3 and four land portions.

[0029] The circumferential grooves 3 include, for example, a first crown circumferential groove 4, a second crown circumferential groove 5, a first shoulder circumferential groove 6, and a second shoulder circumferential groove 7. The first crown circumferential groove 4 is provided between the tire equator C and the first tread edge T1. The second crown circumferential groove 5 is provided between the tire equator C and the second tread edge T2. The first shoulder circumferential groove 6 is provided between the first crown circumferential groove 4 and the first tread edge T1. The second shoulder circumferential groove 7 is provided between the second crown circumferential groove 5 and the second tread edge T2.

[0030] The circumferential grooves 3 may have various configurations, such as extending linearly in the tire circumferential direction or extending in a zigzag pattern.

[0031] The axial distance L1 from the groove centerline of the first crown circumferential groove 4 or the second crown circumferential groove 5 to the tire equator C is, for example, 5% to 15% of the tread width TW. The axial distance L2 from the groove centerline of the first shoulder circumferential groove 6 or the second shoulder circumferential groove 7 to the tire equator C is, for example, 25% to 35% of the tread width TW. The tread width TW is the axial distance from the first tread edge T1 to the second tread edge T2 in the normal state.

[0032] The groove width W1 of the circumferential groove 3 is desirably at least 3 mm or more. In a desirable embodiment, the groove width W1 of the circumferential groove 3 is 3.0% to 7.0% of the tread width TW.

[0033] The land portion includes at least a crown land portion 10 and a first middle land portion 11. The crown land portion 10 is divided between the first crown circumferential groove 4 and the second crown circumferential groove 5. The first middle land portion 11 is divided between the first crown circumferential groove 4 and the first shoulder circumferential groove 6, and is adjacent to the crown land portion 10 via the first crown circumferential groove 4.

[0034] In addition to these, the land portion of this embodiment includes a second middle land portion 12, a first shoulder land portion 13, and a second shoulder land portion 14. The second middle land portion 12 is located between the second crown circumferential groove 5 and the second shoulder circumferential groove 7, and is adjacent to the crown land portion 10 via the second crown circumferential groove 5. The first shoulder land portion 13 is located axially outward of the first shoulder circumferential groove 6, and includes the first tread edge T1. The second shoulder land portion 14 is located axially outward of the second shoulder circumferential groove 7, and includes the second tread edge T2.

[0035] FIG. 2 shows an enlarged view of the crown land portion 10 and the first middle land portion 11. As shown in FIG. 2, the crown land portion 10 is provided with a plurality of crown lateral grooves 15. The crown lateral grooves 15 are inclined in a first direction (downward to the right in each figure in this specification) with respect to the tire axial direction, and completely cross the crown land portion 10 in the tire axial direction. The first middle land portion 11 is provided with a plurality of first middle lateral grooves 20. The first middle lateral grooves 20 are inclined in a second direction (upward to the right in each figure in this specification) opposite to the first direction with respect to the tire axial direction, and completely cross the first middle land portion 11 in the tire axial direction.

[0036] Fig. 3 shows an enlarged view of the crown lateral grooves 15 and the first middle lateral grooves 20. As shown in Fig. 3, in a plan view of the tread, an angle θ1 between a first straight line 21 connecting both ends of the crown lateral grooves 15 and a second straight line 22 connecting both ends of the first middle lateral grooves 20 is 90 to 150°.

[0037] Moreover, the crown lateral groove 15 includes a first end portion 16 and a second end portion 17 in the tire axial direction, and a central portion 18 disposed between the first end portion 16 and the second end portion 17. The groove width of the central portion 18 of the crown lateral groove 15 is smaller than the groove width of the first end portion 16 and the groove width of the second end portion 17. By adopting the above-mentioned configuration, the tire 1 of the present invention can improve noise performance while maintaining on-snow performance. The following mechanism is presumed to be the reason for this.

[0038] The crown lateral grooves 15 and the first middle lateral grooves 20 of the present invention are inclined in opposite directions to each other, so that they generate large snow column shear forces in multiple directions during running on snow, improving performance on snow. In addition, in the present invention, the angle θ1 between the first straight line 21 and the second straight line 22 is specified, so that the performance on snow is improved while the resonance of the noise generated by the crown lateral grooves 15 and the first middle lateral grooves 20 can be suppressed. In other words, the above-mentioned configuration can disperse the frequency band of the noise generated by the crown lateral grooves 15 and the first middle lateral grooves 20 to make it into white noise.

[0039] Furthermore, by including the central portion 18 with a narrow groove width in the crown lateral groove 15, the amount of air passing through the crown lateral groove 15 can be reduced, and the noise of the crown lateral groove 15 can be reduced. This also makes it possible to more effectively suppress the above-mentioned resonance. It is presumed that this mechanism enables the present invention to improve noise performance while maintaining on-snow performance.

[0040] A more detailed configuration of this embodiment will be described below. Each configuration described below shows a specific aspect of this embodiment. Therefore, it goes without saying that the present invention can achieve the above-mentioned effects even if it does not have the configuration described below. In addition, even if any one of the configurations described below is applied alone to the tire of the present invention having the above-mentioned characteristics, an improvement in performance according to each configuration can be expected. Furthermore, when some of the configurations described below are applied in combination, a composite improvement in performance according to each configuration can be expected.

[0041] As shown in FIG. 2, the maximum groove width of the center portion 18 of the crown lateral groove 15 is, for example, 15% or less of the maximum groove width of the first end portion 16 and the second end portion 17, and is preferably 3% to 15%. As a more preferable embodiment, the center portion 18 of the crown lateral groove 15 of this embodiment is configured as a narrow groove portion having a groove width of 1.5 mm or less. This allows the rigidity of the crown land portion 10 to be maintained, and improves the steering stability on dry road surfaces (hereinafter, sometimes simply referred to as "steering stability"). Hereinafter, in this specification, unless otherwise specified, the "narrow groove portion" refers to a portion of the groove having a groove width of 1.5 mm or less. Also, the "narrow groove" refers to a groove having a groove width of 1.5 mm or less throughout its entirety. Also, grooves not described as narrow grooves have a groove width greater than 1.5 mm. In each lateral groove of this embodiment, the portion not described as narrow groove portion has a groove width of, for example, about 2.0 to 4.0 mm.

[0042] For example, the central portion 18 crosses the axial center position of the crown land portion 10. For example, the axial length L3 of the central portion 18 is 40% to 60% of the axial width W2 of the crown land portion 10. Such a central portion 18 improves on-snow performance and noise performance in a well-balanced manner.

[0043] The central portion 18 is inclined in the first direction with respect to the tire axial direction. The angle θ2 of the central portion 18 with respect to the tire axial direction is, for example, 45° or less, and desirably 35 to 45°.

[0044] The axial length of the first end portion 16 and the axial length of the second end portion 17 are each shorter than the axial length L3 of the central portion 18 and are 20% to 30% of the axial width W2 of the crown land portion 10.

[0045] The first end 16 and the second end 17 are inclined in the first direction with respect to the tire axial direction. The angle of the first end 16 and the second end 17 with respect to the tire axial direction is smaller than the angle θ2 of the central portion 18 with respect to the tire axial direction, and is, for example, 10 to 25°. As a result, it is desirable that the crown lateral groove 15 includes a portion that is formed by the first end 16 and the central portion 18 and is slightly convex on one side in the tire circumferential direction, and a portion that is formed by the second end 17 and the central portion 18 and is slightly convex on the other side in the tire circumferential direction. In such a crown lateral groove 15, the first end 16 and the second end 17 form a solid snow pillar together with the circumferential groove, and the traction performance on snow can be improved.

[0046] As shown in FIG. 3, when the crown lateral groove 15 has the above-mentioned configuration, the angle of the first straight line 21 connecting both ends of the crown lateral groove 15 with respect to the tire axial direction is, for example, 45° or less, and preferably 20 to 40°.

[0047] A one-pitch length P1 of the multiple crown lateral grooves 15 in the tire circumferential direction is, for example, 60% to 90% of the axial width W2 of the crown land portion 10. This improves on-snow performance and noise performance in a well-balanced manner.

[0048] A first crown narrow groove 23 and a second crown narrow groove 24 are provided between two crown lateral grooves 15 adjacent to each other in the tire circumferential direction. The first crown narrow groove 23 extends from the first crown circumferential groove 4 and terminates in the crown land portion 10. The second crown narrow groove 24 extends from the second crown circumferential groove 5 and terminates in the crown land portion 10.

[0049] The axial length of the first crown narrow groove 23 is, for example, 80% to 120% of the axial length of the first end 16 of the crown lateral groove 15. The second crown narrow groove 24 is terminated, for example, closer to the first crown circumferential groove 4 than the second end 17 of the crown lateral groove 15. Such first crown narrow groove 23 and second crown narrow groove 24 disperse the frequency of noise generated when the crown land portion 10 contacts the ground, improving noise performance.

[0050] The first crown narrow groove 23 and the second crown narrow groove 24 are inclined in a first direction with respect to the tire axial direction. The angle of the first crown narrow groove 23 with respect to the tire axial direction and the angle of the second crown narrow groove 24 with respect to the tire axial direction are smaller than the angle of the center portion 18 of the crown lateral groove 15 with respect to the tire axial direction. On the other hand, the angle difference between the first crown narrow groove 23 and the second crown narrow groove 24 and the center portion 18 is, for example, 15° or less, and preferably 10° or less. Specifically, the first crown narrow groove 23 and the second crown narrow groove 24 are inclined at an angle of 30 to 40° with respect to the tire axial direction.

[0051] The land ratio of the crown land portion 10 is preferably 65% ​​to 75%. This provides a good balance between on-snow performance and steering stability. In this specification, the land ratio of the land portion refers to the ratio of the area of ​​the actual ground contact surface of the land portion to the area of ​​the virtual ground contact surface in which all the grooves in the land portion are filled. Ratio of Refers to...

[0052] FIG. 4 shows a cross-sectional view of the crown land portion 10. As shown in FIG. 4, in a meridian section including the axis of rotation of the tire in a normal state where the tire is mounted on a normal rim with normal internal pressure and no load, the tread surface of the crown land portion 10 has a profile that is curved convexly outward in the tire radial direction. The radius of curvature R1 of the profile of the tread surface of the crown land portion 10 is, for example, 350 to 500 mm. Such a crown land portion 10 can reduce the ground pressure acting on the vertical edge extending in the tire circumferential direction at the end of the land portion, and can improve noise performance while maintaining performance on snow. It goes without saying that the curvature of the profile is drawn larger than the actual one in FIG. 4 to make the above-mentioned features easier to understand.

[0053] As shown in Fig. 3, the first middle lateral groove 20 is curved in a convex direction toward one side in the tire circumferential direction. However, the curvature of the first middle lateral groove 20 is slight, and the distance between the groove centerline of the first middle lateral groove 20 and the second straight line 22 connecting both ends of the first middle lateral groove 20 is smaller than the groove width of the first middle lateral groove 20. In addition, the groove width of the first middle lateral groove 20 in the longitudinal direction is smaller than the groove width of both ends. Since the shape of the first middle lateral groove 20 is easily deformed by changes in ground pressure acting on the groove, snow can be strongly compacted inside and snow can be prevented from clogging inside.

[0054] The first middle lateral grooves 20 are arranged at a different angle to the tire axial direction from the crown lateral grooves 15. This can reliably prevent the noise generated by each lateral groove from resonating. In this embodiment, the angle of the second straight line 22 to the tire axial direction is smaller than the angle of the first straight line 21 to the tire axial direction. The angle of the second straight line 22 to the tire axial direction is, for example, 5 to 25 degrees. Such first middle lateral grooves 20 are useful for further improving noise performance.

[0055] In this embodiment, the crown lateral groove 15 and the first middle lateral groove 20 are adjacent to each other in the tire axial direction, so that the first straight line 21 and the second straight line 22 intersect in the first crown circumferential groove 4 between the crown land portion 10 and the first middle land portion 11 in the tread plan view. In a more preferable embodiment, the region of the connecting portion between the crown lateral groove 15 and the first crown circumferential groove 4 projected parallel to the tire axial direction overlaps with the connecting portion between the first middle lateral groove 20 and the first crown circumferential groove 4. As shown in FIG. 2, in a more preferable embodiment, the crown lateral grooves 15 and the first middle lateral grooves 20 arranged in the tire circumferential direction are arranged in the above-mentioned relationship. As a result, the crown lateral grooves 15 and the first middle lateral grooves 20 can form solid snow columns at the connecting portions with the first crown circumferential groove 4, and excellent on-snow performance can be exhibited.

[0056] In this embodiment, the first middle land portion 11 is provided with a plurality of first middle narrow grooves 26. The first middle narrow grooves 26 completely cross the first middle land portion 11 in the tire axial direction, and are provided alternately with the first middle lateral grooves 20 in the tire circumferential direction.

[0057] The first middle narrow groove 26 is, for example, inclined in the second direction with respect to the tire axial direction. 1st Middle Narrow Groove 26 extend along the first middle lateral groove 20, and the angle difference therebetween is 5° or less. The first middle narrow groove 26 is also arranged at a smaller angle with respect to the tire axial direction than the first crown narrow groove 23 and the second crown narrow groove 24. Specifically, the angle of the first middle narrow groove 26 with respect to the tire axial direction is 5 to 25°.

[0058] The land ratio of the first middle land portion 11 is, for example, 65% to 75%. In a preferred embodiment, the land ratio of the first middle land portion 11 is larger than the land ratio of the crown land portion 10. This improves the driving stability while maintaining the performance on snow.

[0059] The tread surface of the first middle land portion 11 has a profile that is curved convexly outward in the tire radial direction, similar to the tread surface of the crown land portion 10 shown in Fig. 4. The radius of curvature of the tread surface of the first middle land portion 11 is preferably smaller than that of the crown land portion 10, for example, 250 to 300 mm. Such a first middle land portion 11 can reduce the ground pressure acting on its vertical edges and improve noise performance while maintaining on-snow performance.

[0060] Fig. 5 shows an enlarged view of the second middle land portion 12. As shown in Fig. 5, the second middle land portion 12 has a plurality of second middle lateral grooves 30 and second middle narrow grooves 31 alternately provided in the tire circumferential direction.

[0061] The second middle lateral grooves 30 are, for example, inclined in a second direction with respect to the tire axial direction, and completely cross the second middle land portion 12 in the tire axial direction. The second middle lateral grooves 30 are preferably arranged at an angle with respect to the tire axial direction smaller than the central portion 18 (shown in FIG. 2) of the crown lateral grooves 15. The angle of the second middle lateral grooves 30 with respect to the tire axial direction is, for example, 15 to 25 degrees. This makes it possible to suppress resonance of noise generated by the second middle lateral grooves 30 and the crown lateral grooves 15.

[0062] The second middle lateral groove 30 includes, for example, an inner groove portion 30a extending from the second crown circumferential groove 5 and an outer narrow groove portion 30b extending from the outer end of the inner groove portion 30a to the second shoulder circumferential groove 7.

[0063] For example, the inner groove portion 30a crosses the axial center position of the second middle land portion 12. The axial length L4 of the inner groove portion 30a is, for example, 60% to 90% of the axial width W3 of the second middle land portion 12. Such an inner groove portion 30a improves on-snow performance and driving stability in a well-balanced manner.

[0064] In this embodiment, it is preferable that the projected area of ​​the inner groove portion 30a extended along its length overlaps the connecting portion between the second crown circumferential groove 5 and the crown lateral groove 15 (shown in FIG. 2), thereby further improving the on-snow performance.

[0065] The outer narrow groove portion 30b extends, for example, linearly from the inner groove portion 30a to the second shoulder circumferential groove 7 while being inclined in the second direction.

[0066] The second middle narrow groove 31 is, for example, inclined in a second direction with respect to the tire axial direction and completely crosses the second middle land portion 12 in the tire axial direction. In this embodiment, the second middle narrow groove 31 extends, for example, along the second middle lateral groove 30, and the angle difference therebetween is 5° or less. Such a second middle narrow groove 31 can improve on-snow performance while suppressing uneven wear of the second middle land portion 12.

[0067] The land ratio of the second middle lateral grooves 30 is, for example, 65% to 75%. In a preferred embodiment, the land ratio of the first middle land portion 11 is greater than that of the crown land portion 10. The tread surface of the second middle land portion 12 has a profile that is convexly curved outward in the tire radial direction, similar to the tread surface of the crown land portion 10 shown in Fig. 4. The radius of curvature of the tread surface of the second middle land portion 12 is, for example, 250 to 300 mm, similar to the tread surface of the first middle land portion 11.

[0068] Fig. 6 shows an enlarged view of the first shoulder land portion 13. As shown in Fig. 6, in the first shoulder land portion 13, first shoulder lateral grooves 35 and first shoulder narrow grooves 36 are provided alternately in the tire circumferential direction.

[0069] For example, the first shoulder lateral groove 35 extends at least from the first tread edge T1 to the first shoulder circumferential groove 6. For example, the first shoulder lateral groove 35 is curved convexly toward one side in the tire circumferential direction.

[0070] The first shoulder lateral groove 35 includes, for example, a main body portion 35a on the first tread edge T1 side, and an inner end portion 35b extending from the axially inner end of the main body portion 35a to the first shoulder circumferential groove 6.

[0071] For example, the main body portion 35a of the first shoulder lateral groove 35 crosses the axial center position of the first shoulder land portion 13. The axial length L5 of the main body portion 35a is, for example, 60% to 80% of the axial width W4 of the first shoulder land portion 13. This improves on-snow performance and noise performance in a well-balanced manner.

[0072] The inner end 35b of the first shoulder lateral groove 35 has a groove width smaller than that of the main body portion 35a. The groove width of the inner end 35b is preferably 3% to 15% of the groove width of the main body portion 35a. In this embodiment, the inner end 35b of the first shoulder lateral groove 35 is configured as a narrow groove portion with a groove width of 1.5 mm or less. This reduces the amount of air passing through the first shoulder lateral groove 35, improving noise performance.

[0073] It is desirable that the axial length L6 of the inner end 35b of the first shoulder lateral groove 35 is smaller than the axial length L3 (shown in FIG. 2) of the central portion 18 of the crown lateral groove 15. Specifically, the length L6 of the inner end 35b is 40% to 60% of the length L3 of the central portion 18. This makes it possible to suppress resonance of noise generated by the crown lateral grooves 15 and the first shoulder lateral grooves 35.

[0074] For example, the first shoulder narrow groove 36 completely crosses the first shoulder land portion 13 in the tire axial direction. In this embodiment, the first shoulder narrow groove 36 is curved so as to be convex toward one side in the tire circumferential direction. In a more preferable embodiment, the first shoulder narrow groove 36 and the first shoulder lateral groove 35 extend parallel to each other, and the angle difference between them is 5° or less. Such a first shoulder narrow groove 36 can improve on-snow performance while suppressing uneven wear of the first shoulder land portion 13.

[0075] The land ratio of the first shoulder land portion 13 is preferably larger than that of the crown land portion 10. Specifically, the land ratio of the first shoulder land portion is 75% to 85%. Such a first shoulder land portion 13 is useful for improving steering stability on dry road surfaces.

[0076] Fig. 7 shows an enlarged view of the second shoulder land portion 14. As shown in Fig. 7, in the second shoulder land portion 14, second shoulder lateral grooves 40 and second shoulder narrow grooves 41 are provided alternately in the tire circumferential direction.

[0077] The second shoulder lateral grooves 40, for example, extend at least from the second tread edge T2 axially inward and terminate within the second shoulder land portion 14. The axial length L7 of the second shoulder lateral grooves 40 is, for example, 75% to 90% of the axial width W5 of the second shoulder land portion 14. This makes it possible to suppress deterioration of noise performance due to air leaking from the second shoulder circumferential groove 7 toward the second tread edge T2.

[0078] The second shoulder lateral groove 40 includes, for example, a main body portion 40a on the second tread edge T2 side, and an inner end portion 40b that is continuous with the main body portion 40a on the axially inner side of the tire and has a groove width smaller than that of the main body portion 40a.

[0079] The main body portion 40a of the second shoulder lateral groove 40 crosses, for example, the axial center position of the second shoulder land portion 14. The axial length L8 of the main body portion 40a is, for example, 60% to 70% of the axial width W5 of the second shoulder land portion 14. This improves on-snow performance and noise performance in a well-balanced manner.

[0080] The inner end 40b of the second shoulder lateral groove 40 extends from the main body portion 40a and terminates within the second shoulder land portion 14. The axial length L9 of the inner end 40b is, for example, 15% to 25% of the axial width W5 of the second shoulder land portion 14. In a more preferable embodiment, the length L9 of the inner end 40b is shorter than the axial length L3 of the center portion 18 of the crown lateral groove 15. This makes it possible to suppress resonance of noise generated by each lateral groove.

[0081] The groove width of the inner end 40b of the second shoulder lateral groove 40 is preferably 3% to 15% of the groove width of the main body 40a of the second shoulder lateral groove 40. In this embodiment, the inner end 40b of the second shoulder lateral groove 40 is configured as a narrow groove portion with a groove width of 1.5 mm or less. This provides excellent steering stability.

[0082] For example, the second shoulder narrow groove 41 completely crosses the second shoulder land portion 14 in the tire axial direction. In this embodiment, the second shoulder narrow groove 41 and the second shoulder lateral groove 40 extend parallel to each other, and the angle difference between them is set to 5° or less.

[0083] The land ratio of the second shoulder land portion 14 is preferably larger than that of the crown land portion 10. Specifically, the land ratio of the first shoulder land portion is 75% to 85%. Such a second shoulder land portion 14 is useful for improving on-snow performance and noise performance in a well-balanced manner.

[0084] Although the tire according to one embodiment of the present invention has been described in detail above, the present invention is not limited to the above specific embodiment and can be modified and carried out in various aspects. EXAMPLES

[0085] A tire having a size of 225 / 65R17 and having the pattern shown in FIG. 1 was prototyped based on the specifications in Table 1. As a comparative example, a tire having a crown land portion shown in FIG. 8 was prototyped. As shown in FIG. 8, in the comparative tire, the crown lateral groove a extends along the tire axial direction, and the angle θ1 between the first straight line c connecting both ends of the crown lateral groove a and the second straight line d connecting both ends of the first middle lateral groove b is set to 175°. The comparative tire has substantially the same pattern as that shown in FIG. 1, except for the above-mentioned configuration. Each test tire was tested for on-snow performance and noise performance. The common specifications and test methods of each test tire are as follows. Rim: 17×7.0JJ Tire pressure: front wheel 230kPa, rear wheel 210kPa Test vehicle: 2000cc displacement, four-wheel drive Tire mounting position: All wheels

[0086] <Snow performance> The test tire was run on an inside drum testing machine filled with snow, and the friction coefficient was measured when accelerating from 8km / h to 35km / h. The results were scored using the coefficient of friction of the comparative example as an index, with a higher value indicating better performance on snow.

[0087] <Noise performance> The noise performance when the above test vehicle was driven on a dry road surface was evaluated by the driver. The results are given as a score based on the comparative example being 100, with a higher score indicating better noise performance. The test results are shown in Table 1.

[0088] [Table 1]

[0089] As shown in Table 1, it was confirmed that the tires of the examples had improved noise performance while maintaining performance on snow. [Explanation of symbols]

[0090] 2 Tread section 3 Circumferential groove 10 Crown Land Division 11 First Middle Track Division 15 Crown lateral groove 16 First end 17 Second end 18 Central part 20 First Middle Yokomizo 21 1st straight line 22 Second straight line T1 First tread edge T2 Second tread edge

Claims

1. A tire having a tread portion, The tread portion includes a plurality of circumferential grooves extending continuously in a tire circumferential direction between a first tread edge and a second tread edge, and a plurality of land portions divided by the circumferential grooves, the plurality of land portions include a crown land portion and a first middle land portion adjacent to the crown land portion on the first tread end side with the circumferential groove interposed therebetween, The crown land portion is provided with a plurality of crown lateral grooves inclined in a first direction with respect to a tire axial direction and completely crossing the crown land portion in the tire axial direction, a plurality of first middle lateral grooves are provided in the first middle land portion, the first middle lateral grooves being inclined in a second direction opposite to the first direction with respect to the tire axial direction and completely crossing the first middle land portion in the tire axial direction; In a tread plan view, an angle between a first straight line connecting both ends of the crown lateral groove and a second straight line connecting both ends of the first middle lateral groove is 90 to 150 degrees, The crown lateral groove includes a first end portion and a second end portion in an axial direction of the tire, and a central portion disposed between the first end portion and the second end portion, a groove width at the central portion is smaller than a groove width at the first end portion and a groove width at the second end portion; The length of the central portion in the tire axial direction is 40% to 60% of the width of the crown land portion in the tire axial direction, The vehicle mounting direction is specified, The first tread edge is located on an inner side of the vehicle when the tire is mounted on the vehicle. tire.

2. A tire having a tread portion, The tread portion includes a plurality of circumferential grooves extending continuously in a tire circumferential direction between a first tread edge and a second tread edge, and a plurality of land portions divided by the circumferential grooves, the plurality of land portions include a crown land portion and a first middle land portion adjacent to the crown land portion on the first tread end side with the circumferential groove interposed therebetween, The crown land portion is provided with a plurality of crown lateral grooves inclined in a first direction with respect to a tire axial direction and completely crossing the crown land portion in the tire axial direction, a plurality of first middle lateral grooves are provided in the first middle land portion, the first middle lateral grooves being inclined in a second direction opposite to the first direction with respect to the tire axial direction and completely crossing the first middle land portion in the tire axial direction; In a tread plan view, an angle between a first straight line connecting both ends of the crown lateral groove and a second straight line connecting both ends of the first middle lateral groove is 90 to 150 degrees, The crown lateral groove includes a first end portion and a second end portion in an axial direction of the tire, and a central portion disposed between the first end portion and the second end portion, a groove width at the central portion is smaller than a groove width at the first end portion and a groove width at the second end portion; the first end portion and the second end portion are each inclined in the first direction with respect to the tire axial direction, an angle of the first end portion and the second end portion with respect to the tire axial direction is smaller than an angle of the center portion with respect to the tire axial direction, The vehicle mounting direction is specified, The first tread edge is located on an inner side of the vehicle when the tire is mounted on the vehicle. tire.

3. The tire according to claim 1 or 2, wherein a maximum groove width in the central portion is 15% or less of a maximum groove width in the first end portion and the second end portion.

4. A tire as described in any one of claims 1 to 3, wherein the angle of the second straight line relative to the tire axial direction is smaller than the angle of the first straight line relative to the tire axial direction.

5. A tire as described in any one of claims 1 to 4, wherein the crown lateral groove and the first middle lateral groove are adjacent to each other in the tire axial direction, so that in a tread plan view, the first straight line and the second straight line intersect within the circumferential groove between the crown land portion and the first middle land portion.

6. A tire as described in any one of claims 1 to 5, wherein in a meridian section including the tire rotation axis in a normal state in which the tire is mounted on a normal rim with normal internal pressure and is unloaded, the tread surface of the crown land portion and the tread surface of the first middle land portion each have a profile that is convexly curved outward in the radial direction of the tire.

7. A tire as described in any one of claims 1 to 6, wherein the land ratio of the crown land portion is 65% to 75%.

8. The tread portion includes a first shoulder land portion including the first tread edge, The tire according to claim 1 , wherein a land ratio of the first shoulder land portion is greater than a land ratio of the crown land portion.

9. The tread portion includes a first shoulder land portion including the first tread edge, The tire according to any one of claims 1 to 8, wherein a land ratio of the first shoulder land portion is 75% to 85%.

10. The tread portion includes a second shoulder land portion including the second tread edge, The tire according to claim 1 , wherein the second shoulder land portion is provided with a plurality of second shoulder lateral grooves extending axially inward from at least the second tread end and terminated within the second shoulder land portion.

11. A tire as described in claim 10, wherein the second shoulder lateral groove includes a main body portion on the second tread end side, and an inner end portion that is connected to the main body portion on the axially inner side of the tire and has a groove width smaller than that of the main body portion.

12. A tire as described in claim 11, wherein the groove width of the inner end portion is 3% to 15% of the groove width of the main body portion.

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