tire

Abstract

To provide a tire which is suppressed in uneven wear and furthermore improved in wet performance.SOLUTION: A tread portion 2 includes a first shoulder circumferential groove 5, a first crown circumferential groove 7, and a first middle land portion 13. A plurality of first middle lateral grooves 41 are provided in the first middle land portion 13, and at least one of the first middle lateral grooves 41 includes a shallow groove portion 16. The first middle land portion 13 includes an acute-angle-side corner portion 17 sectioned off between the first crown circumferential groove 7 and the shallow groove portion 16. A chamfered portion 18 is formed at a leading end portion 17a in a tire circumferential direction, of the acute-angle-side corner portion 17. The chamfered portion 18 includes an inclined surface 18a extending from a grounding surface of the first middle land portion 13 toward the leading end of the arcuate-angle-side corner portion 17 and inclined with respect to a tire radial direction.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] The following Patent Document 1 proposes a tire having an outer middle land portion and an inner middle land portion. The outer middle land portion is provided with a plurality of outer middle lug grooves extending from a main groove and terminated within the outer middle land portion. The inner middle land portion is provided with a plurality of inner middle lateral grooves crossing the land portion. The tire is expected to improve wet performance by the outer middle lug grooves and the inner middle lateral grooves. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-012437 A Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, there has been a demand for tires to have even greater improvements in wet performance, while there is also a demand for tires to have uneven wear suppressed.

[0005] The present invention has been devised in view of the above circumstances, and has as its main object to provide a tire which suppresses uneven wear while improving wet performance. [Means for solving the problem]

[0006] 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 into the plurality of circumferential grooves, the plurality of circumferential grooves including a first shoulder circumferential groove disposed between a tire equator and the first tread edge, and a first crown circumferential groove disposed between the first shoulder circumferential groove and the tire equator, the plurality of land portions including a first middle land portion divided between the first shoulder circumferential groove and the first crown circumferential groove, The dollar land portion has a plurality of first middle lateral grooves, at least one of which includes a shallow groove portion extending from the first crown circumferential groove at an angle with respect to the tire axial direction, and the first middle land portion includes an acute-angle corner portion separated between the first crown circumferential groove and the shallow groove portion in a plan view of the tread, and a chamfered portion is formed at the circumferential tip portion of the acute-angle corner portion, and the chamfered portion extends from the contact surface of the first middle land portion toward the tip of the acute-angle corner portion and includes an inclined surface inclined with respect to the radial direction of the tire.

[0007] In the tire of the present invention, it is preferable that the shallow groove portion includes an inner portion on the side of the first crown circumferential groove, and the inner portion includes a first groove edge extending approximately parallel to the tire axial direction and connected to the first crown circumferential groove, and a second groove edge inclined with respect to the tire axial direction and connected to the first crown circumferential groove.

[0008] In the tire of the present invention, it is preferable that the first groove edge constitutes a boundary between the ground contact surface of the first middle land portion and the inclined surface of the chamfered portion.

[0009] In the tire of the present invention, it is preferable that the first groove edge extends linearly.

[0010] In the tire of the present invention, it is preferable that the shallow groove portion includes an inner portion on the first crown circumferential groove side, a variable depth portion connected to the inner portion, and a constant depth portion connected to the variable depth portion, the variable depth portion decreasing in depth toward the constant depth portion, and the constant depth portion extending at a constant depth.

[0011] In the tire of the present invention, it is preferable that the variable depth portion has a groove width that decreases toward the constant depth portion.

[0012] In the tire of the present invention, it is preferable that one groove edge of the shallow groove portion extends linearly from the inner portion to the constant depth portion.

[0013] In the tire of the present invention, the angle between the first crown circumferential groove and the shallow groove portion is preferably 20 to 45°.

[0014] In the tire of the present invention, it is preferable that the first middle lateral groove includes a main portion extending from the shallow groove portion to the first shoulder circumferential groove.

[0015] In the tire of the present invention, it is preferable that the main body portion is disposed at a smaller angle with respect to the tire axial direction than the shallow groove portion.

[0016] In the tire of the present invention, it is preferable that the maximum depth of the main body portion is greater than the maximum depth of the shallow groove portion. Effect of the Invention

[0017] By adopting the above-mentioned configuration, the tire of the present invention can improve wet performance while suppressing uneven wear. [Brief description of the drawings]

[0018] [Figure 1] 1 is a development view of a tread portion showing one embodiment of the present invention. [Diagram 2] FIG. 2 is an enlarged view of the first middle land portion of FIG. [Diagram 3]FIG. 3 is an enlarged view of a first middle lateral groove of FIG. 2. [Figure 4] FIG. 4 is a partial side view of a tip end portion of the first middle land portion of FIG. 3. [Diagram 5] FIG. 4 is a cross-sectional view taken along line BB in FIG. [Figure 6] 4 is a cross-sectional view taken along line CC in FIG. [Figure 7] 2 is an enlarged view of a first middle land portion, a second middle land portion, and a crown land portion in FIG. 1. [Figure 8] FIG. 2 is an enlarged view of a first shoulder land portion of FIG. [Figure 9] FIG. 2 is an enlarged view of the second shoulder land portion of FIG. [Figure 10] FIG. 2 is a development view of a tread portion of a tire of a comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] 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 showing one embodiment of the present invention. The tire 1 of this embodiment is suitably used, for example, as a pneumatic tire for passenger cars. However, the present invention is not limited to such an embodiment, and may be applied to a pneumatic tire for heavy loads and a non-pneumatic tire in which pressurized air is not filled inside the tire.

[0020] As shown in Fig. 1, a tread portion 2 of the present invention includes a plurality of circumferential grooves 3 extending continuously in the tire circumferential direction between a first tread edge T1 and a second tread edge T2, and a plurality of land portions 4 divided by the plurality of circumferential grooves 3. The tire 1 of the present embodiment is configured as a so-called five-rib tire in which the tread portion 2 is divided into five land portions 4 by four circumferential grooves 3. However, the present invention is not limited to this embodiment.

[0021] For example, the mounting orientation of the tread portion 2 of this embodiment on a vehicle is specified. As a result, the first tread edge T1 is located on the outer side of the vehicle when mounted on the vehicle. The second tread edge T2 is located on the inner side of the vehicle when mounted on the vehicle. The mounting orientation on the vehicle is indicated, for example, by letters or symbols on the sidewall portion (not shown). However, the tire 1 of the present invention is not limited to this embodiment, and the mounting orientation on the vehicle may not be specified.

[0022] The first tread edge T1 and the second tread edge T2 each correspond to the axially outermost contact position 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°.

[0023] "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 unloaded. 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, in which the tire is not mounted on a vehicle and is unloaded. In this specification, unless otherwise specified, the dimensions of each part of the tire are values ​​measured in the normal condition.

[0024] 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."

[0025] "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."

[0026] 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.

[0027] The plurality of circumferential grooves 3 include a first shoulder circumferential groove 5 and a first crown circumferential groove 7. The first shoulder circumferential groove 5 is aligned with a tire equator C. First tread edge T1 and is disposed closest to the first tread edge T1 side among the plurality of circumferential grooves 3. The first crown circumferential groove 7 is disposed between the first shoulder circumferential groove 5 and the tire equator C.

[0028] Furthermore, the multiple circumferential grooves 3 in this embodiment include a second shoulder circumferential groove 6 and a second crown circumferential groove 8. The second shoulder circumferential groove 6 is disposed closest to the second tread edge T2 side among the multiple circumferential grooves 3. The second crown circumferential groove 8 is disposed between the second shoulder circumferential groove 6 and the tire equator C.

[0029] The axial distance L1 from the tire equator C to the groove centerline of the first shoulder circumferential groove 5 or the second shoulder circumferential groove 6 is preferably, for example, 25% to 35% of the tread width TW. The axial distance L2 from the tire equator C to the groove centerline of the first crown circumferential groove 7 or the second crown circumferential groove 8 is preferably, for example, 5% to 15% 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.

[0030] Each of the circumferential grooves 3 in this embodiment extends, for example, linearly in parallel to the tire circumferential direction. Each of the circumferential grooves 3 may extend, for example, in a wavy manner.

[0031] The groove width W1 of each circumferential groove 3 is preferably at least 3 mm. The groove width W1 of each circumferential groove 3 is preferably, for example, 4.0% to 8.5% of the tread width TW. In this embodiment, the first shoulder circumferential groove 5 has the smallest groove width among the multiple circumferential grooves 3. However, the present invention is not limited to this embodiment. The depth of each circumferential groove 3 is preferably, for example, 5 to 10 mm in the case of a pneumatic tire for a passenger car.

[0032] The plurality of land portions 4 of the present invention include a first middle land portion 13. The first middle land portion 13 is partitioned between the first shoulder circumferential groove 5 and the first crown circumferential groove 7.

[0033] Furthermore, the land portion 4 of this embodiment includes a first shoulder land portion 11, a second shoulder land portion 12, a second middle land portion 14, and a crown land portion 15. The first shoulder land portion 11 includes the first tread edge T1 and is located axially outward of the first shoulder circumferential groove 5. The second shoulder land portion 12 includes the second tread edge T2 and is located axially outward of the second shoulder circumferential groove 6. The second middle land portion 14 is located between the second shoulder circumferential groove 6 and the second crown circumferential groove 8. The crown land portion 15 is located between the first crown circumferential groove 7 and the second crown circumferential groove 8.

[0034] Fig. 2 shows an enlarged view of the first middle land portion 13. As shown in Fig. 2, the first middle land portion 13 is provided with a plurality of first middle lateral grooves 41.

[0035] FIG. 3 shows an enlarged view of the first middle lateral groove 41 in FIG. 2. As shown in FIG. 3, at least one of the first middle lateral grooves 41 includes a shallow groove portion 16 extending from the first crown circumferential groove 7 at an angle with respect to the tire axial direction. As a result, the first middle land portion 13 includes an acute-angle corner portion 17 partitioned between the first crown circumferential groove 7 and the shallow groove portion 16 in a tread plan view. A chamfered portion 18 is formed at a tip portion 17a in the tire circumferential direction of the acute-angle corner portion 17. In FIG. 3, dots are applied to the opening region of the first middle lateral groove 41, and dots are applied to the chamfered portion 18 that are darker than other portions of the opening region.

[0036] Fig. 4 shows a partial side view of the tip portion 17a as seen from the direction of the arrow A in Fig. 3. In Fig. 4, dots are applied to the opening area of ​​the shallow groove portion 16 on the side surface of the first middle land portion 13. As shown in Fig. 4, the chamfered portion 18 extends from the ground contact surface of the first middle land portion 13 toward the tip of the corner portion 17 on the acute angle side, and includes an inclined surface 18a inclined with respect to the tire radial direction. By adopting the above-mentioned configuration, the present invention can improve wet performance while suppressing uneven wear. The following mechanism is presumed to be the reason for this.

[0037] The shallow groove portion 16 included in the first middle lateral groove 41 provides frictional force in the axial direction of the tire by its edge during wet driving, improving wet performance. Meanwhile, the chamfered portion 18 is formed at the circumferential tip portion 17a of the acute-angle corner portion 17, thereby suppressing uneven wear of the corner portion 17. In addition, such chamfered portion 18 can assist the water inside the first crown circumferential groove 7 to be pushed away to the rear of the tire by the rotation of the tire during wet driving. Therefore, the drainage of the first crown circumferential groove 7 can be improved. It is presumed that the tire of the present invention can improve wet performance while maintaining steering stability on dry road surfaces due to the above mechanism.

[0038] 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.

[0039] As shown in FIG. 2, in this embodiment, the angle θ1 between the first crown circumferential groove 7 and the shallow groove portion 16 is set to 20 to 30° C. 45° The maximum depth of the shallow groove portion 16 is, for example, 1.0 to 4.0 mm, and preferably 1.0 to 3.0 mm.

[0040] As shown in FIG. 3, the shallow groove portion 16 of this embodiment includes an inner portion 32 on the first crown circumferential groove 7 side. In this embodiment, the maximum depth of the inner portion 32 constitutes the maximum depth of the shallow groove portion 16. This inner portion 32 includes a first groove edge 33 and a second groove edge 34. The first groove edge 33 extends approximately parallel to the tire axial direction and is connected to the first crown circumferential groove 7. The first groove edge 33 constitutes the boundary between the ground contact surface of the first middle land portion 13 and the inclined surface 18a of the chamfered portion 18. The second groove edge 34 is inclined with respect to the tire axial direction and is connected to the first crown circumferential groove 7. A groove wall extending along the depth direction of the shallow groove portion 16 is continuous with the second groove edge 34.

[0041] The angle of the first groove edge 33 with respect to the tire axial direction is 5° or less, and the first groove edge 33 extends in a straight line. As shown in Fig. 2, the length L3 of the first groove edge 33 in the tire axial direction is, for example, 5% to 15% of the width W9 of the ground contact surface of the first middle land portion 13 in the tire axial direction, specifically, 2.0 to 5.0 mm. The angle of the second groove edge 34 with respect to the tire axial direction is, for example, 45 to 70°, and the second groove edge 34 extends in a straight line. The inner portion 32 including the first groove edge 33 and the second groove edge 34 improves uneven wear resistance and wet performance in a well-balanced manner.

[0042] From the same viewpoint, the opening width W6 of the inner portion 32 on the first crown circumferential groove 7 side is, for example, 30% to 70% of the groove width W1 (shown in FIG. 1) of the first crown circumferential groove 7.

[0043] As shown in Fig. 3, the inclined surface 18a of the chamfered portion 18 has a width in the tire axial direction that decreases, for example, from the first groove edge 33 toward the tip of the corner portion 17 on the acute angle side. Also, as shown in Fig. 4, the angle θ2 of the inclined surface 18a with respect to the tire radial direction is, for example, 30 to 70°, and preferably 50 to 70°. Such a chamfered portion 18 can suppress uneven wear and cooperate with the first crown circumferential groove 7 to effectively push water away to the rear of the tire.

[0044] 5 shows a cross-sectional view of the shallow groove portion 16 of FIG. 3 taken along line BB. As shown in FIG. 5, the shallow groove portion 16 includes a variable depth portion 47 and a constant depth portion 48. The variable depth portion 47 is connected to the axially outer side of the inner portion 32, and the constant depth portion 48 is connected to the axially outer side of the variable depth portion 47. The variable depth portion 47 is smaller in depth from the inner portion 32 toward the constant depth portion 48. The constant depth portion 48 extends at a constant depth. The shallow groove portion 16 including the variable depth portion 47 and the constant depth portion 48 is useful for improving uneven wear resistance and wet performance in a well-balanced manner.

[0045] The maximum depth of the variable depth portion 47 is, for example, 1.0 to 3.0 mm. The depth of the variable depth portion 47 decreases continuously from the inner portion 32 toward the constant depth portion 48. The depth of the constant depth portion 48 is, for example, 0.5 to 0.9 mm.

[0046] 3, the variable depth portion 47 has a groove width that decreases from the inner portion 32 toward the constant depth portion 48. The maximum groove width of the variable depth portion 47 is, for example, 0.8 to 3.0 mm. The groove width of the constant depth portion 48 is, for example, 0.5 to 0.7 mm.

[0047] In this embodiment, one groove edge of the shallow groove portion 16 extends linearly from the inner portion 32 through the variable depth portion 47 to the constant depth portion 48. The other groove edge of the shallow groove portion 16 is curved at the boundary between the inner portion 32 and the variable depth portion 47 and at the boundary between the variable depth portion 47 and the constant depth portion 48. However, the shallow groove portion 16 of the present invention is not limited to this embodiment.

[0048] The first middle lateral groove 41 includes a main body portion 43 extending from the shallow groove portion 16 to the first shoulder circumferential groove 5. The main body portion 43 is disposed, for example, at a smaller angle with respect to the tire axial direction than the shallow groove portion 16. The angle of the main body portion 43 with respect to the tire axial direction is, for example, 10° or less. Such a main body portion 43 provides friction in the tire circumferential direction and improves traction when driving on wet surfaces.

[0049] 2, the axial length L11 of the main body portion 43 is, for example, 40% to 60% of the axial width W9 of the contact surface of the first middle land portion 13. The first middle lateral groove 41 having such a main body portion 43 is useful for improving driving stability and wet performance in a well-balanced manner.

[0050] The maximum groove width of the main body portion 43 is, for example, 40% to 70% of the groove width of the first shoulder circumferential groove 5. The main body portion 43 includes, for example, a wide portion 43a that is continuous with the first shoulder circumferential groove 5 and that constitutes the maximum groove width of the main body portion 43, and a narrow portion 43b that has a groove width smaller than that of the wide portion 43a. The groove width of the narrow portion 43b is 60% to 90% of the groove width of the wide portion 43a.

[0051] FIG. 6 shows a cross section of line CC in FIG. 3. As shown in FIG. 6, the edge of the main body portion 43 of the first middle lateral groove 41 is preferably configured with a chamfered portion 45. A narrow groove portion 46 having a width of 0.5 to 1.5 mm is connected to the inner side of the chamfered portion 45 in the tire radial direction. The maximum depth of the main body portion 43 including the chamfered portion 45 and the narrow groove portion 46 is, for example, larger than the maximum depth of the shallow groove portion 16. Specifically, the maximum depth of the main body portion 43 is 40% to 60% of the maximum depth of the first shoulder circumferential groove 5. The first middle lateral groove 41 having such a main body portion 43 can maintain the rigidity of the first middle land portion 13 and improve the driving stability.

[0052] 2, the first middle land portion 13 of this embodiment is provided with first middle interrupted grooves 42 in addition to the above-mentioned first middle lateral grooves 41. It is preferable that the first middle lateral grooves 41 and the first middle interrupted grooves 42 are provided alternately in the tire circumferential direction.

[0053] The first middle interrupted groove 42 extends from the first shoulder circumferential groove 5 and terminates within the first middle land portion 13. The axial length L12 of the first middle interrupted groove 42 is, for example, smaller than the axial length of the main body portion 43 of the first middle lateral groove 41. Specifically, the length L12 of the first middle interrupted groove 42 is 20% to 30% of the axial width W9 of the contact surface of the first middle land portion 13. Such a first middle interrupted groove 42 can improve wet performance while maintaining the rigidity of the first middle land portion 13.

[0054] The cross section of the first middle interrupted groove 42 is substantially the same as the cross section of the main body 43 of the first middle lateral groove 41 shown in Fig. 6. Therefore, the cross section of the first middle interrupted groove 42 can have the same configuration as the cross section of the first middle lateral groove 41.

[0055] 7 shows an enlarged view of the first middle land portion 13, the second middle land portion 14, and the crown land portion 15 in FIG. 1. As shown in FIG. 7, the second middle land portion 14 is provided with a plurality of second middle lateral grooves 50. The second middle lateral grooves 50 include a body portion 51 extending from the second shoulder circumferential groove 6 and a shallow groove portion 52 extending from the body portion 51 to the second crown circumferential groove 8. The body portion 51 and the shallow groove portion 52 of the second middle lateral groove 50 may have the same configuration as the body portion 43 and the shallow groove portion 16 of the first middle lateral groove 41 described above, except for the matters described below.

[0056] The main body portion 51 of the second middle lateral groove 50 is terminated without crossing, for example, the axial center position of the ground contact surface of the second middle land portion 14. The axial length L13 of the main body portion 51 of the second middle lateral groove 50 is 30% to 50% of the axial width W10 of the ground contact surface of the second middle land portion 14. In a more preferable embodiment, the axial length L13 of the main body portion 51 of the second middle lateral groove 50 is smaller than the axial length L11 of the main body portion 43 of the first middle lateral groove 41. The second middle lateral groove 50 having such a main body portion 51 can improve wet performance while maintaining the rigidity of the second middle land portion 14 at an appropriate level.

[0057] The crown land portion 15 is provided with a plurality of first crown lateral grooves 56 and a plurality of second crown lateral grooves 57 .

[0058] The first crown lateral grooves 56 extend from the first crown circumferential grooves 7 and terminate within the crown land portion 15 without reaching the second crown circumferential grooves 8. The axial length L14 of the first crown lateral grooves 56 is, for example, 10% to 30% of the axial width W11 of the ground contact surface of the crown land portion 15. In a preferred embodiment, the length L14 of the first crown lateral grooves 56 is smaller than the axial length L11 of the main body portion 43 of the first middle lateral grooves 41, the axial length L12 of the first middle discontinuous grooves 42, and the axial length L13 of the main body portion 51 of the second middle lateral grooves 50. Such first crown lateral grooves 56 can reliably maintain the rigidity of the crown land portion 15 while compensating for wet performance, and can improve driving stability.

[0059] The second crown lateral groove 57 includes, for example, a main body portion 58 extending in the tire axial direction from the second crown circumferential groove 8, and a shallow groove portion 59 extending from the main body portion 58 and ending without reaching the first crown circumferential groove 7.

[0060] The main body portion 58 of the second crown lateral groove 57 extends from the second crown circumferential groove 8 and terminates in the crown land portion 15 without reaching the first crown circumferential groove 7. The axial length L15 of the main body portion 58 of the second crown lateral groove 57 is, for example, 45% to 60% of the axial width W11 of the ground contact surface of the crown land portion 15. In a preferred embodiment, the length L15 of the main body portion 58 of the second crown lateral groove 57 is preferably smaller than the axial length L11 of the main body portion 43 of the first middle lateral groove 41 and is larger than the axial length L13 of the main body portion 51 of the second middle lateral groove 50. The second crown lateral groove 57 including such a main body portion 58 is useful for improving the driving stability and the wet performance in a well-balanced manner.

[0061] The shallow groove portion 59 of the second crown lateral groove 57 has a groove width and depth of, for example, 0.3 to 1.5 mm, and preferably 0.5 to 1.0 mm. The shallow groove portion 59 of the second crown lateral groove 57 extends at a larger angle with respect to the tire axial direction than the main body portion 58. The shallow groove portion 59 of the second crown lateral groove 57 is also formed at a larger angle with respect to the first middle lateral groove 41. Shallow groove 16 The angle of the shallow groove portion 59 of the second crown lateral groove 57 with respect to the tire axial direction is, for example, 50 to 70°. The second crown lateral groove 57 including such shallow groove portion 59 is useful for improving cornering performance during wet driving.

[0062] Fig. 8 shows an enlarged view of the first shoulder land portion 11. As shown in Fig. 8, the first shoulder land portion 11 is provided with a plurality of first shoulder lateral grooves 20. The first shoulder lateral grooves 20 extend from the first shoulder circumferential groove 5 to a position beyond the first tread edge T1.

[0063] At least one of the first shoulder lateral grooves 20 includes an inner end 20i communicating with the first shoulder circumferential groove 5, a maximum groove width portion 21 that defines the maximum groove width W2 of the first shoulder lateral groove 20, and an outer portion 22 that is axially outer than the first tread edge T1. The maximum groove width portion 21 includes not only the portion that defines the maximum groove width W2, but also a portion that defines a groove width that is 95% or more of the maximum groove width W2.

[0064] In this embodiment, the maximum groove width portion 21 is located approximately at the center in the tire axial direction of the ground contact surface of the first shoulder land portion 11. This configuration includes at least an embodiment in which the maximum groove width portion 21 crosses the center position in the tire axial direction of the ground contact surface of the first shoulder land portion 11. The configuration also includes an embodiment in which the distance between the maximum groove width portion 21 and the center position is 5% or less of the axial width W5 of the ground contact surface of the first shoulder land portion 11 even if the maximum groove width portion 21 does not cross the center position. The first shoulder lateral groove having such a maximum groove width portion 21 can exhibit excellent drainage while maintaining steering stability.

[0065] The groove width W3 at the inner end 20i of the first shoulder lateral groove 20 and the groove width W4 at the first tread edge T1 of the first shoulder lateral groove 20 are each smaller than the maximum groove width W2. The groove width of the outer portion 22 of the first shoulder lateral groove 20 decreases toward the axially outer side of the tire. This maintains the rigidity of the first shoulder land portion 11 and provides excellent driving stability.

[0066] The groove width W3 of the inner end 20i of the first shoulder lateral groove 20 is, for example, 50% to 90%, and preferably 70% to 80%, of the maximum groove width W2. The first shoulder lateral groove 20 having such inner ends 20i is useful for improving the driving stability and wet performance in a well-balanced manner.

[0067] The maximum groove width W2 is, for example, 20% to 35% of one circumferential pitch length P1 of the first shoulder lateral grooves 20. The axial length L5 of the maximum groove width portion 21 is, for example, 25% to 45%, and preferably 30% to 40%, of the axial width W5 of the contact surface of the first shoulder land portion 11. The first shoulder lateral grooves 20 having such maximum groove width portion 21 can exhibit excellent wet performance while maintaining driving stability.

[0068] In the present embodiment, it is desirable that the groove width of the outer portion 22 continuously decreases from the first tread edge T1 toward the axially outer side of the tire. This suppresses uneven wear around the outer portion 22. However, the present invention is not limited to this embodiment, and the outer portion 22 may include, for example, a portion extending with a constant groove width.

[0069] The outer portion 22 includes, for example, a first portion 27 on the first tread edge T1 side and a second portion 28 on the axially outer side of the first portion 27. The angle between the two edges of the first portion 27 is, for example, 10 to 25°. The angle between the two edges of the second portion 28 is smaller than the angle of the first portion 27, for example, less than 10°.

[0070] The axial length L6 of the outer portion 22 is, for example, equal to or less than the axial width W5 of the ground contact surface of the first shoulder land portion 11. Specifically, the length L6 is 70% to 90% of the width W5, and preferably 75% to 85%. The axial length L7 of the first portion 27 is 20% to 50% of the axial length L6 of the outer portion 22. The axial length L8 of the second portion 28 is 1 / 2 the axial length L6 of the outer portion 22. Length L6 This outer portion 22 improves the driving stability and the wet performance in a well-balanced manner.

[0071] The first shoulder lateral groove 20 has, for example, a maximum depth in the main body portion 25. The maximum depth of the first shoulder lateral groove 20 is, for example, 60% to 90% of the maximum depth of the first shoulder circumferential groove 5, and desirably 70% to 80%.

[0072] The inner portion 23 has a depth smaller than that of the main body portion 25. The maximum depth of the inner portion 23 is, for example, 45% to 65% of the maximum depth of the first shoulder lateral groove 20, and preferably 50% to 60%.

[0073] The depth of the outer portion 22 decreases toward the axially outer side of the tire. The depth at the outer end of the first shoulder lateral groove 20 is, for example, 5% to 25%, and preferably 10% to 20%, of the maximum depth of the first shoulder lateral groove 20. Such an outer portion 22 is useful for improving the driving stability and the wet performance in a well-balanced manner.

[0074] FIG. 9 shows an enlarged view of the second shoulder land portion 12. As shown in FIG. 9, the second shoulder land portion 12 is provided with a plurality of second shoulder lateral grooves 35. The second shoulder lateral groove 35 of this embodiment includes, for example, a main body portion 36 extending from a position away from the second shoulder circumferential groove 6 to the second tread edge T2, and an outer portion 37 axially outer than the second tread edge T2. The outer portion 37 of the second shoulder lateral groove 35 may have the configuration of the outer portion 22 (shown in FIG. 8) of the first shoulder lateral groove 20 described above. The main body portion 36 of the second shoulder lateral groove 35 may have the configuration of the main body portion 25 of the first shoulder lateral groove 20, except for the configuration described below.

[0075] The distance L10 in the tire axial direction from the main body portion 36 of the second shoulder lateral groove 35 to the second shoulder circumferential groove 6 is, for example, 5% to 15% of the axial width W8 of the contact surface of the second shoulder land portion 12. The second shoulder lateral groove 35 including such a main body portion 36 can improve the wet performance while maintaining the rigidity of the second shoulder land portion 12.

[0076] The main body 36 of the second shoulder lateral groove 35 includes an inclined edge 35a at the axially inner end thereof, which extends at an angle in the tire circumferential direction. The angle of the inclined edge 35a with respect to the tire circumferential direction is, for example, 20 to 40°. Such an inclined edge 35a provides frictional force in the tire axial direction as well, improving turning performance on wet road surfaces.

[0077] The second shoulder lateral grooves 35 of this embodiment include standard type second shoulder lateral grooves 35A and shallow grooved second shoulder lateral grooves 35B. In this embodiment, the standard type second shoulder lateral grooves 35A and the shallow grooved second shoulder lateral grooves 35B are alternately provided in the tire circumferential direction.

[0078] The standard type second shoulder lateral groove 35A has no groove between its main body 36 and the second shoulder circumferential groove 6. The shallow grooved second shoulder lateral groove 35B includes a shallow groove portion 38 extending from its main body 36 to the second shoulder circumferential groove 6. The shallow groove portion 38 has a groove width and depth of, for example, 0.3 to 1.5 mm, and preferably 0.5 to 1.0 mm. Such a shallow groove portion 38 can compensate for the friction force in the axial direction of the tire on wet road surfaces.

[0079] 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

[0080] A tire having a size of 225 / 50R17 and the basic pattern of FIG. 1 was prototyped based on the specifications of Tables 1-2. In addition, a tire having a tread portion shown in FIG. 10 was prototyped as a comparative example. In the comparative tire, a chamfered portion is not provided at the acute-angle corner portion d partitioned between the crown circumferential groove a and the shallow groove portion c of the middle lateral groove b. The comparative tire is substantially the same as the tire shown in FIG. 1 except for the above-mentioned points. The uneven wear resistance and wet performance of each test tire were tested. The common specifications and test methods of each test tire are as follows. Rim: 17×7.5J Tire pressure: front wheel 220kPa, rear wheel 240kPa Test vehicle: 2000cc, rear-wheel drive Tire mounting position: All wheels

[0081] <Resistant to uneven wear> After driving a certain distance with the above test vehicle, the degree of uneven wear of the first middle land portion was visually evaluated. The results were evaluated as a score based on the degree of uneven wear of the comparative example being 100, with a higher value indicating better uneven wear resistance.

[0082] <Wet performance> The wet performance of the test vehicle when it was driven on a wet road surface was evaluated by the driver. The results are rated based on the wet performance of the comparative example being 100, with the higher the value, the better the wet performance. The test results are shown in Tables 1-2.

[0083] [Table 1]

[0084] [Table 2]

[0085] As shown in Tables 1 and 2, it was confirmed that the tires of the examples had improved wet performance while suppressing uneven wear. [Explanation of symbols]

[0086] 2 Tread section 3 Circumferential groove 4 Land 5 First shoulder circumferential groove 7 First crown circumferential groove 13 1st Middle Track Division 16 Shallow groove 17 Corner 17a Tip 18 Chamfer 18a Slope 41 First Middle Yokomizo 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 plurality of circumferential grooves, the plurality of circumferential grooves include a first shoulder circumferential groove arranged between a tire equator and the first tread edge, and a first crown circumferential groove arranged between the first shoulder circumferential groove and the tire equator, the plurality of land portions include a first middle land portion partitioned between the first shoulder circumferential groove and the first crown circumferential groove, The first middle land portion is provided with a plurality of first middle lateral grooves, At least one of the first middle lateral grooves includes a shallow groove portion extending from the first crown circumferential groove at an angle with respect to the tire axial direction, the first middle land portion includes an acute-angle corner portion partitioned between the first crown circumferential groove and the shallow groove portion in a tread plan view, A chamfer is formed at a tip end portion of the acute-angle corner portion in the tire circumferential direction, the chamfered portion extends from the ground contact surface of the first middle land portion toward a tip of the acute-angle side corner portion and includes an inclined surface inclined with respect to a radial direction of the tire, the shallow groove portion includes an inner portion on the first crown circumferential groove side, a variable depth portion connected to the inner portion, and a constant depth portion connected to the variable depth portion, The variable depth portion has a depth decreasing toward the constant depth portion, The constant depth portion extends at a constant depth; The variable depth portion has a groove width that decreases toward the constant depth portion. 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 plurality of circumferential grooves, the plurality of circumferential grooves include a first shoulder circumferential groove arranged between a tire equator and the first tread edge, and a first crown circumferential groove arranged between the first shoulder circumferential groove and the tire equator, the plurality of land portions include a first middle land portion partitioned between the first shoulder circumferential groove and the first crown circumferential groove, The first middle land portion is provided with a plurality of first middle lateral grooves, At least one of the first middle lateral grooves includes a shallow groove portion extending from the first crown circumferential groove at an angle with respect to the tire axial direction, the first middle land portion includes an acute-angle corner portion partitioned between the first crown circumferential groove and the shallow groove portion in a tread plan view, A chamfer is formed at a tip end portion of the acute-angle corner portion in the tire circumferential direction, the chamfered portion extends from the ground contact surface of the first middle land portion toward a tip of the acute-angle side corner portion and includes an inclined surface inclined with respect to a radial direction of the tire, the first middle lateral groove includes a main body portion extending from the shallow groove portion to the first shoulder circumferential groove, the shallow groove portion includes an inner portion on the first crown circumferential groove side, a variable depth portion connected to the inner portion, and a constant depth portion connected to the variable depth portion, The variable depth portion has a depth decreasing toward the constant depth portion, The constant depth portion extends at a constant depth; The main body portion is disposed at a smaller angle with respect to the tire axial direction than the constant depth portion. tire.

3. 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 plurality of circumferential grooves, the plurality of circumferential grooves include a first shoulder circumferential groove arranged between a tire equator and the first tread edge, and a first crown circumferential groove arranged between the first shoulder circumferential groove and the tire equator, the plurality of land portions include a first middle land portion partitioned between the first shoulder circumferential groove and the first crown circumferential groove, The first middle land portion is provided with a plurality of first middle lateral grooves, At least one of the first middle lateral grooves includes a shallow groove portion extending from the first crown circumferential groove at an angle with respect to the tire axial direction, the first middle land portion includes an acute-angle corner portion partitioned between the first crown circumferential groove and the shallow groove portion in a tread plan view, A chamfer is formed at a tip end portion of the acute-angle corner portion in the tire circumferential direction, the chamfered portion extends from the ground contact surface of the first middle land portion toward a tip of the acute-angle side corner portion and includes an inclined surface inclined with respect to a radial direction of the tire, the first middle lateral groove includes a main body portion extending from the shallow groove portion to the first shoulder circumferential groove, The maximum depth of the body portion is greater than the maximum depth of the shallow groove portion. tire.

4. The shallow groove portion includes an inner portion on the first crown circumferential groove side, 4. The tire according to claim 1, wherein the inner portion includes a first groove edge extending substantially parallel to a tire axial direction and connected to the first crown circumferential groove, and a second groove edge inclined with respect to the tire axial direction and connected to the first crown circumferential groove.

5. A tire as described in claim 4, wherein the first groove edge forms a boundary between the contact surface of the first middle land portion and the inclined surface of the chamfered portion.

6. A tire as described in claim 4 or 5, wherein the first groove edge extends in a straight line.

7. The tire according to claim 1 or 2, wherein one groove edge of the shallow groove portion extends in a straight line from the inner portion to the constant depth portion.

8. The tire according to any one of claims 1 to 7, wherein an angle between the first crown circumferential groove and the shallow groove portion is 20 to 45 degrees.

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