tire

Abstract

To provide a tire capable of improving turning performance on ice and snow.SOLUTION: A tread part 2 of a tire 1 includes a first circumferential groove 3 continuously extending in a tire peripheral direction on a tread ground contact end Te side; and a second circumferential groove 4 continuously extending in the tire peripheral direction in adjacent to the first circumferential groove 3. The first circumferential groove 3 includes a first groove wall 11 positioned inside in a tire axial direction and a second groove wall 12 positioned outside in the tire axial direction. The second circumferential groove includes a third groove wall 13 positioned inside in the tire axial direction; and a fourth groove wall 14 positioned outside in the tire axial direction. A first angle θ1 of the first groove wall 11, a second angle θ2 of the second groove wall 12, a third angle θ3 of the third groove wall 13, and a fourth angle θ4 of the fourth groove wall satisfy the following formulae: θ1>θ2...(1), θ3>θ4...(2), (θ3-θ4)>(θ1-θ2)...(3).SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to tires. [Background technology]

[0002] Patent Document 1 below describes a pneumatic tire having a tread portion. The tread portion is provided with main grooves that extend continuously in the tire circumferential direction between the tire equator and the tread edge. In a meridian cross section including the tire rotation axis, the main grooves include an inner groove wall on the tire equator side and an outer groove wall on the tread edge side that has a larger inclination angle than the inner groove wall. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2016-022800 Summary of the Invention [Problem to be solved by the invention]

[0004] Although the above-mentioned pneumatic tires have been designed to improve straight-line driving performance on snow, there is still room for improvement in cornering performance on ice and snow.

[0005] The present disclosure has been devised in view of the above circumstances, and has as its main object to provide a tire that can improve cornering performance on ice and snow. [Means for solving the problem]

[0006] The present disclosure relates to a tire having a tread portion, the tread portion including a first circumferential groove extending continuously in the tire circumferential direction on a tread ground contact edge side, and a second circumferential groove adjacent to the first circumferential groove and extending continuously in the tire circumferential direction, the first circumferential groove including a first groove wall located on an axially inner side of the tire and a second groove wall located on an axially outer side of the tire, the second circumferential groove including a third groove wall located on an axially inner side of the tire and a fourth groove wall located on an axially outer side of the tire, the first groove wall including a portion inclined radially inward and axially outward with respect to a tread normal line erected at the groove edge, and a first angle θ1 with respect to the tread normal line the second groove wall includes a portion inclined radially inward and axially inward with respect to a tread normal line established at the groove edge, and has a second angle θ2 with respect to the tread normal line; the third groove wall includes a portion inclined radially inward and axially outward with respect to a tread normal line established at the groove edge, and has a third angle θ3 with respect to the tread normal line; and the fourth groove wall includes a portion inclined radially inward and axially inward with respect to a tread normal line established at the groove edge, and has a fourth angle θ4 with respect to the tread normal line, and the first to fourth angles θ1 to θ4 satisfy the following formula: θ1>θ2 …(1) θ3>θ4 …(2) (θ3-θ4)>(θ1-θ2) …(3) [Effects of the Invention]

[0007] By employing the above configuration, the tire of the present disclosure can improve cornering performance on ice and snow. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 2 is a cross-sectional view of the tread portion of the tire. [Figure 2] FIG. [Figure 3] 2 is an enlarged view of the first circumferential groove and the second circumferential groove of FIG. 1. [Figure 4]FIG. 10 is a cross-sectional view of a first circumferential groove and a second circumferential groove according to another embodiment of the present disclosure. [Figure 5] FIG. 2 is a cross-sectional view of a tread portion of a tire 1 according to another embodiment of the present disclosure. [Figure 6] 1(a) is a cross-sectional view showing the first and second circumferential grooves of Comparative Example 1. FIG. 1(b) is a cross-sectional view showing the first and second circumferential grooves of Comparative Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. It should be understood that the drawings include exaggerated representations and representations that differ from the dimensional ratios of actual structures in order to facilitate understanding of the contents of the disclosure. Furthermore, identical or common elements are designated by the same reference numerals throughout the embodiments, and redundant explanations will be omitted. Furthermore, the specific configurations shown in the embodiments and drawings are intended to facilitate understanding of the contents of the present disclosure, and the present disclosure is not limited to the specific configurations shown in the drawings.

[0010] [Tire (first embodiment)] Fig. 1 is a cross-sectional view of a tread portion 2 of a tire 1 according to this embodiment. Fig. 2 is a development view of the tread portion 2. In Fig. 1, a dashed dotted line indicates the tire equator (equatorial plane) C. The tread pattern according to this embodiment is formed in a shape that is line-symmetrical with respect to the tire equator C, but is not particularly limited thereto.

[0011] The tire 1 of this embodiment is preferably used as a pneumatic tire for passenger cars, for example. However, the present disclosure is not limited to such an embodiment, and may be used, for example, as a pneumatic tire for heavy loads or a non-pneumatic tire (airless tire) that is not filled with pressurized air inside the tire. The tire 1 of this embodiment is also preferably used as a winter tire. Note that a winter tire refers to a tire 1 suitable for driving on snow, including studless tires, snow tires, all-season tires, etc.

[0012] The tread portion 2 of the tire 1 of this embodiment is configured to include a first circumferential groove 3 and a second circumferential groove 4. The first circumferential groove 3 and the second circumferential groove 4 divide the tread portion 2 of this embodiment into a plurality of land portions 5.

[0013] As shown in Figure 2, the land portion 5 of this embodiment is provided with lateral grooves 6 extending in a direction intersecting the first circumferential groove 3 and the second circumferential groove 4. This divides the land portion 5 into a plurality of blocks 7. The tread portion 2 (each block 7) of this embodiment is provided with a plurality of sipes 8. This increases the edge component of the tread portion 2, improving ice performance and wet performance. A "sipe" is defined as having a width of less than 1.5 mm.

[0014] 1 and 2, the tread edge Te of the tread portion 2 is the axially outermost end of the contact patch when the tire 1 in a normal state is placed on a flat surface with a normal load and a camber angle of 0 degrees. The distance in the tire axial direction between these tread edges Te is defined as the tread width TW.

[0015] "Normal state" refers to a state in which the tire 1 is mounted on a normal rim (hereinafter sometimes simply referred to as "rim"), adjusted to a normal internal pressure, and no load is applied. Unless otherwise specified, the dimensions of each part of the tire 1 are values ​​measured in this normal state. Furthermore, unless otherwise specified, the groove width of each groove is measured in a direction perpendicular to its longitudinal direction.

[0016] A "genuine rim" is a rim that is defined for each tire by a standard system that includes the standard on which tire 1 is based. Therefore, a genuine rim is, for example, a "standard rim" for JATMA, a "design rim" for TRA, or a "measuring rim" for ETRTO.

[0017] "Normal internal pressure" is the air pressure specified for each tire by each standard in the standard system including the standard on which tire 1 is based. Therefore, the normal internal pressure is the "maximum air pressure" for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS SAT VARIOUSCOLD INFLATION PRESSURES" for TRA, and the "INFLATION PRESSURE" for ETRTO.

[0018] "Normal load" is the load specified for each tire in the standard system that includes the standard on which the tire is based. Therefore, normal load is "Maximum Load Capacity" for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and "LOAD CAPACITY" for ETRTO.

[0019] [First circumferential groove] The first circumferential grooves 3 of this embodiment extend continuously in the tire circumferential direction on the tread ground contact edge Te side. Such first circumferential grooves 3 allow a water film on the road surface to be discharged in the tire circumferential direction, improving wet performance. Furthermore, the first circumferential grooves 3 form strong snow pillars when cornering on snowy roads, for example, and provide a large snow pillar shear force, improving cornering performance on snow. As shown in FIG. 2, the first circumferential grooves 3 of this embodiment extend linearly in the tire circumferential direction, but may also extend in a zigzag pattern.

[0020] As shown in Fig. 1, the groove width W1 and groove depth D1 of the first circumferential groove 3 are set appropriately according to convention. The groove width W1 is set to, for example, 2.0% to 6.0% of the tread contact width TW. The groove depth D1 is set to, for example, 5.0 to 15.0 mm.

[0021] Fig. 3 is an enlarged view of the first circumferential groove 3 and the second circumferential groove 4 in Fig. 1. The first circumferential groove 3 of this embodiment includes a first groove wall 11 located axially inside the tire and a second groove wall 12 located axially outside the tire. The first groove wall 11 and the second groove wall 12 face each other in the tire axial direction with the groove bottom 3b interposed therebetween.

[0022] The first groove wall 11 of this embodiment includes a portion 11A (hereinafter simply referred to as a "first inclined portion") that is inclined radially inward and axially outward with respect to a tread normal N1 that is set at the groove edge 11e. The first inclined portion 11A is inclined at a first angle θ1 with respect to the tread normal N1.

[0023] The first inclined portion 11A of this embodiment allows the axial width of the land portion 5 (in this example, the land portion axially inside the first circumferential groove 3) divided by the first circumferential groove 3 to gradually increase toward the radially inner side of the tire. This causes the rigidity of the tread portion 2 (land portion 5) to gradually increase from the radially outer side to the radially inner side of the tire, improving cornering performance on ice. Furthermore, since the rigidity of the tread portion 2 is maintained, steering stability on dry roads is maintained.

[0024] The first inclined portion 11A of this embodiment extends linearly from the groove edge 11e to the groove bottom 3b while maintaining the inclination at the first angle θ1.

[0025] The second groove wall 12 of this embodiment includes a portion 12A (hereinafter simply referred to as a "second inclined portion") that is inclined radially inward and axially outward with respect to the tread normal N2 that is erected at the groove edge 12e. This second inclined portion 12A is inclined at a second angle θ2 with respect to the tread normal N2.

[0026] The second inclined portion 12A of this embodiment can gradually increase the axial width of the land portion 5 (in this example, the land portion axially outer of the first circumferential groove 3) divided by the first circumferential groove 3 toward the radially inner side of the tire. This causes the rigidity of the tread portion 2 (land portion 5) to gradually increase from the radially outer side to the radially inner side of the tire, improving cornering performance on ice while maintaining steering stability on dry roads.

[0027] The second inclined portion 12A of this embodiment extends linearly from the groove edge 12e to the groove bottom 3b while maintaining the inclination at the second angle θ2.

[0028] [Second circumferential groove] 1 and 2, the second circumferential grooves 4 of this embodiment extend continuously in the tire circumferential direction adjacent to the first circumferential grooves 3. In the second circumferential grooves 4, similar to the first circumferential grooves 3, wet performance and cornering performance on snow are improved.

[0029] The second circumferential grooves 4 of this embodiment are arranged between the first circumferential grooves 3 and the tire equator C. As shown in FIG. 2, the second circumferential grooves 4 of this embodiment extend linearly in the tire circumferential direction, but may extend in a zigzag pattern. As shown in FIG. 1, the groove width W2 and groove depth D2 of the second circumferential grooves 4 are set appropriately. The groove width W2 and groove depth D2 of this embodiment can be set to the same range as the groove width W1 and groove depth D1 of the first circumferential grooves 3.

[0030] 3, the second circumferential groove 4 of this embodiment includes a third groove wall 13 located axially inside the tire and a fourth groove wall 14 located axially outside the tire. The third groove wall 13 and the fourth groove wall 14 face each other in the tire axial direction via the groove bottom 4b.

[0031] The third groove wall 13 of this embodiment includes a portion 13A (hereinafter simply referred to as a "third inclined portion") that is inclined radially inward and axially outward with respect to the tread normal N3 that is erected at the groove edge 13e. The third inclined portion 13A is inclined at a third angle θ3 with respect to the tread normal N3.

[0032] The third inclined portion 13A of this embodiment can gradually increase the axial width of the land portion 5 (in this example, the land portion axially inside the second circumferential groove 4) divided by the second circumferential groove 4 toward the radially inner side of the tire. This causes the rigidity of the tread portion 2 (land portion 5) to gradually increase from the radially outer side to the radially inner side of the tire, improving cornering performance on ice while maintaining steering stability on dry roads.

[0033] The third inclined portion 13A of the present embodiment extends linearly from the groove edge 13e to the groove bottom 4b while maintaining the inclination of the third angle θ3, thereby increasing the rigidity of the tread portion 2 (land portion 5) and further improving cornering performance on ice.

[0034] The fourth groove wall 14 of this embodiment includes a portion 14A (hereinafter simply referred to as a "fourth inclined portion") that is inclined radially and axially inward with respect to a tread normal N4 that is erected at the groove edge 14e. The fourth inclined portion 14A is inclined at a fourth angle θ4 with respect to the tread normal N4.

[0035] The fourth inclined portion 14A of the present embodiment can gradually increase the axial width of the land portion 5 (in this example, the land portion on the axial outer side of the second circumferential groove 4) divided by the second circumferential groove 4 toward the radially inner side of the tire. This causes the rigidity of the tread portion 2 (land portion 5) to gradually increase from the radially outer side to the radially inner side of the tire, improving cornering performance on ice while maintaining steering stability on dry roads.

[0036] The fourth inclined portion 14A of the present embodiment extends linearly from the groove edge 14e to the groove bottom 4b while maintaining the inclination of the fourth angle θ4, thereby increasing the rigidity of the tread portion 2 (land portion 5) and further improving cornering performance on ice.

[0037] [1st angle θ1~4th angle θ4] In the tire 1 of the present embodiment, the first to fourth angles θ1 to θ4 satisfy the following formulas. θ1>θ2 …(1) θ3>θ4 …(2) (θ3-θ4)>(θ1-θ2) …(3)

[0038] In the first circumferential groove 3 of this embodiment, the first groove wall 11 located axially inner side is deformed more than the second groove wall 12 located axially outer side due to the resultant force of the lateral force acting during cornering (lateral force directed axially outward) and the load acting on the tire 1. In Fig. 3, the deformed state of the first groove wall 11 is shown by the two-dot chain line.

[0039] In this embodiment, by satisfying the above formula (1), the first angle θ1 of the first inclined portion 11A is set larger than the second angle θ2 of the second inclined portion 12A. As a result, when the first groove wall 11 deforms during cornering, the first inclined portion 11A can bring the first angle θ1 closer to 0 degrees (parallel to the tread normal N1), thereby compacting snow in a direction intersecting the first inclined portion 11A (vertical direction). Therefore, strong snow columns are formed in the first circumferential groove 3, and large snow column shear forces are generated, improving cornering performance on snow.

[0040] On the other hand, the second angle θ2 of the second inclined portion 12A is set smaller than the first angle θ1 of the first inclined portion 11A, thereby ensuring the groove volume of the first circumferential groove 3. This maintains wet performance and cornering performance on snow.

[0041] In the second circumferential groove 4 of this embodiment, the third groove wall 13 located axially inside the tire is deformed more than the fourth groove wall 14 located axially outside the tire due to the resultant force of the lateral force acting during cornering (lateral force directed axially outward) and the load acting on the tire 1. In Fig. 3, the deformed state of the third groove wall 13 is shown by the two-dot chain line.

[0042] In this embodiment, by satisfying the above formula (2), the third angle θ3 of the third inclined portion 13A is set larger than the fourth angle θ4 of the fourth inclined portion 14A. As a result, when the third groove wall 13 deforms during cornering, the third inclined portion 13A can bring the third angle θ3 closer to 0 degrees (parallel to the tread normal N3), and can compact snow in a direction intersecting with the third inclined portion 13A (vertical direction). Therefore, strong snow columns are formed in the second circumferential groove 4, and large snow column shear forces are generated, improving cornering performance on snow.

[0043] On the other hand, the fourth angle θ4 of the fourth inclined portion 14A is set smaller than the third angle θ3 of the third inclined portion 13A, thereby ensuring the groove volume of the second circumferential groove 4. This maintains wet performance and cornering performance on snow.

[0044] Furthermore, the lateral force (lateral force directed axially outward) and load acting during cornering tend to act more strongly on the tire equator C side than on the tread contact edge Te side. Therefore, the third groove wall 13 of the second circumferential groove 4 tends to deform more during cornering than the first groove wall 11 of the first circumferential groove 3.

[0045] In this embodiment, by satisfying the above formula (3), the third angle θ3 of the third inclined portion 13A is set relatively large, and therefore, when the third groove wall 13 deforms during cornering, the third angle θ3 can be made close to 0 degrees (parallel to the tread normal N3). As a result, the second circumferential groove 4 can pack snow in a direction intersecting with the third inclined portion 13A (vertical direction), effectively improving cornering performance on snow. To effectively enhance this effect, it is desirable to set the third angle θ3 of the third inclined portion 13A larger than the first angle θ1 of the first inclined portion 11A.

[0046] The first angle θ1 and the third angle θ3 are preferably set to less than 25°. By setting the first angle θ1 and the third angle θ3 to less than 25°, the first inclined portion 11A and the third inclined portion 13A firmly pack snow while ensuring the groove volumes of the first circumferential groove 3 and the second circumferential groove 4. This improves cornering performance on snow and wet performance. On the other hand, by setting the first angle θ1 and the third angle θ3 to 5° or more, snow can be firmly packed. From this perspective, the first angle θ1 and the third angle θ3 are more preferably set to 20° or less, and more preferably set to 10° or more.

[0047] The difference (θ1-θ2) between the first angle θ1 and the second angle θ2 is preferably set to less than 15°. Setting the difference (θ1-θ2) to less than 15° prevents the inclination of the first inclined portion 11A of the first groove wall 11 relative to the second inclined portion 12A of the second groove wall 12 from becoming too large, improving cornering performance on snow and wet performance. On the other hand, setting the difference (θ1-θ2) to 3° or more allows the first inclined portion 11A to compact the snow, improving performance on snow. From this perspective, the difference (θ1-θ2) is preferably 12° or less, and preferably 5° or more.

[0048] From the same perspective as the difference between the first angle θ1 and the second angle θ2 (θ1-θ2), the difference between the third angle θ3 and the fourth angle θ4 (θ3-θ4) is preferably less than 15°, more preferably 12° or less, and is preferably 3° or more, more preferably 5° or more.

[0049] It is preferable that the first to fourth angles θ1 to θ4 further satisfy the following formula. 5°<(θ3-θ4)-(θ1-θ2)<10° …(4)

[0050] By setting (θ3-θ4)-(θ1-θ2) to 5° or more, the inclination (third angle θ3) of the third inclined portion 13A of the third groove wall 13 is set relatively large, improving cornering performance on snow and ice. On the other hand, by setting (θ3-θ4)-(θ1-θ2) to 10° or less, the inclination (third angle θ3) of the third groove wall 13 of the third groove wall 13 is prevented from becoming larger than necessary, ensuring the groove volume of the second circumferential groove 4. This improves cornering performance on snow and wet performance.

[0051] [Tire (Second Embodiment)] 4 is a cross-sectional view of the first circumferential groove 3 and the second circumferential groove 4 according to another embodiment of the present disclosure. The first groove wall 11 of this embodiment includes a portion 11B extending parallel to the tread normal N1 (hereinafter, simply referred to as the "first parallel portion"). Such first parallel portion 11B ensures a groove volume of the first circumferential groove 3, improving cornering performance on snow and wet performance.

[0052] In this embodiment, the first parallel portion 11B extends continuously from the radially upper end of the first inclined portion 11A to the groove edge 11e. The radial length L1 of the first parallel portion 11B is preferably set to 40% to 60% of the groove depth D1 (shown in FIG. 1) of the first circumferential groove 3. By setting the length L1 to 40% or more of the groove depth D1, the groove volume of the first circumferential groove 3 is ensured, and cornering performance on snow and wet performance are improved. On the other hand, by setting the length L1 to 60% or less of the groove depth D1 (shown in FIG. 1), the first inclined portion 11A is prevented from becoming small, and cornering performance on snow is maintained.

[0053] The third groove wall 13 in this embodiment includes a portion 13B extending parallel to the tread normal N3 (hereinafter, simply referred to as the "third parallel portion"). Such third parallel portion 13B ensures the groove volume of the second circumferential groove 4, improving cornering performance on snow and wet performance.

[0054] The third parallel portion 13B of this embodiment extends continuously from the radially upper end of the third inclined portion 13A to the groove edge 13e. From the same viewpoint as the length L1 of the first parallel portion 11B, the radially length L3 of the third parallel portion 13B is preferably set to 30% to 60% of the groove depth D2 (shown in FIG. 1) of the second circumferential groove 4.

[0055] [Tire (third embodiment)] 5 is a cross-sectional view of the tread portion 2 of a tire 1 according to another embodiment of the present disclosure. The tread portion 2 of this embodiment has a specified orientation for mounting on a vehicle. The orientation for mounting on a vehicle is indicated, for example, by letters or symbols on the sidewall portion (not shown).

[0056] The first circumferential groove 3 is the circumferential groove located furthest outward from the vehicle when the tire is mounted on the vehicle. As a result, in this embodiment, for example, during cornering when a lateral force acting toward the outside of the vehicle acts (when the tire 1 is the inner wheel during cornering), snow is firmly compacted by the first inclined portion 11A of the first groove wall 11 of the first circumferential groove 3 and the third inclined portion 13A of the third groove wall 13 of the second circumferential groove 4. Therefore, strong snow columns are formed in the first circumferential groove 3 and the second circumferential groove 4, and a large snow column shear force is generated, improving cornering performance on snow.

[0057] [3rd circumferential groove] The tread portion 2 of this embodiment has an asymmetric pattern. The tread portion 2 of this embodiment is provided with third circumferential grooves 10 provided adjacent to the second circumferential grooves 4.

[0058] The third circumferential groove 10 in this embodiment is disposed closer to the vehicle inner side than the tire equator C. The groove width W3 and groove depth D3 of the third circumferential groove 10 are set appropriately. The groove width W3 and groove depth D3 in this embodiment can be set in the same range as the groove width W1 and groove depth D1 of the first circumferential groove 3 shown in FIG.

[0059] The third circumferential groove 10 of this embodiment includes a fifth groove wall 15 located on the vehicle inner side and a sixth groove wall 16 located on the vehicle outer side. The fifth groove wall 15 and the sixth groove wall 16 face each other in the tire axial direction via the groove bottom 10b.

[0060] The fifth groove wall 15 of this embodiment includes a portion 15A (hereinafter simply referred to as the "fifth inclined portion") that is inclined radially inward and outward from the vehicle with respect to the tread normal N5 that is erected at the groove edge 15e. The fifth inclined portion 15A is inclined at a fifth angle θ5 with respect to the tread normal N5.

[0061] The fifth inclined portion 15A of this embodiment can gradually increase the axial width of the land portion 5 (in this example, the land portion on the vehicle inner side of the third circumferential groove 10) divided by the third circumferential groove 10 toward the radially inner side of the tire. This causes the rigidity of the tread portion 2 (land portion 5) to gradually increase from the radially outer side to the radially inner side of the tire, improving cornering performance on ice while maintaining steering stability on dry roads.

[0062] The fifth inclined portion 15A of this embodiment extends linearly from the groove edge 15e to the groove bottom 10b while maintaining the inclination at the fifth angle θ5.

[0063] The sixth groove wall 16 in this embodiment includes a portion 16A (hereinafter simply referred to as the "sixth inclined portion") that is inclined radially inward in the tire and toward the vehicle with respect to the tread normal N6 that is erected at the groove edge 16e. The sixth inclined portion 16A is inclined at a sixth angle θ6 with respect to the tread normal N6.

[0064] The sixth inclined portion 16A of this embodiment can gradually increase the axial width of the land portion 5 (in this example, the land portion on the vehicle outer side of the third circumferential groove 10) divided by the third circumferential groove 10 toward the radially inner side of the tire. This causes the rigidity of the tread portion 2 (land portion 5) to gradually increase from the radially outer side to the radially inner side of the tire, improving cornering performance on ice.

[0065] The sixth inclined portion 16A in this embodiment extends linearly from the groove edge 16e to the groove bottom 10b while maintaining the inclination at the sixth angle θ6, thereby increasing the rigidity of the tread portion 2 (land portion 5) and further improving cornering performance on ice.

[0066] [First angle θ1, second angle θ2, fifth angle θ5, and sixth angle θ6] In the tire 1 of this embodiment, the first angle θ1, the second angle θ2, the fifth angle θ5, and the sixth angle θ6 satisfy the following formula. θ5>θ6 … (5) (θ5-θ6)>(θ1-θ2) …(6)

[0067] In the third circumferential groove 10 of this embodiment, the fifth groove wall 15 located on the vehicle inner side is deformed more than the sixth groove wall 16 located on the vehicle outer side due to the resultant force of the lateral force toward the vehicle outer side and the load acting on the tire 1. In Figure 5, the deformed state of the fifth groove wall 15 is shown by the two-dot chain line.

[0068] In this embodiment, by satisfying the above formula (5), the fifth angle θ5 of the fifth inclined portion 15A is set larger than the sixth angle θ6 of the sixth inclined portion 16A. As a result, when the fifth groove wall 15 deforms during turning, the fifth inclined portion 15A can bring the fifth angle θ5 closer to 0 degrees, and can compact snow in the direction intersecting with the fifth inclined portion 15A (the vertical direction). Therefore, a strong snow column is formed in the third circumferential groove 10, and a large snow column shear force is generated, improving turning performance on snow.

[0069] On the other hand, the sixth angle θ6 of the sixth inclined portion 16A is set smaller than the fifth angle θ5 of the fifth inclined portion 15A, thereby ensuring the groove volume of the third circumferential groove 10. This maintains wet performance and cornering performance on snow.

[0070] Furthermore, the lateral force (lateral force toward the outside of the vehicle) and load acting during cornering tend to act more strongly on the tire equator C side than on the tread ground contact edge Te (shown in FIG. 1 ). Therefore, the fifth groove wall 15 of the third circumferential groove 10 tends to deform more during cornering than the first groove wall 11 of the first circumferential groove 3.

[0071] In this embodiment, by satisfying the above formula (6), the fifth angle θ5 of the fifth inclined portion 15A is set relatively large, and therefore, when the fifth groove wall 15 deforms during cornering, the fifth angle θ5 can be made close to 0 degrees. This allows the third circumferential groove 10 to compact snow in a direction intersecting with the fifth inclined portion 15A (vertical direction), effectively improving cornering performance on snow. To effectively enhance this effect, it is desirable to set the fifth angle θ5 of the fifth inclined portion 15A larger than the first angle θ1 of the first inclined portion 11A.

[0072] To effectively exert the above-mentioned effect, the fifth angle θ5 is preferably set to be in the same range as the first angle θ1 and the third angle θ3. The difference between the fifth angle θ5 and the sixth angle θ6 (θ5-θ6) is preferably set to be in the same range as the difference between the third angle θ3 and the fourth angle θ4 (θ3-θ4).

[0073] Although particularly preferred embodiments of the present disclosure have been described in detail above, the present disclosure is not limited to the illustrated embodiments and can be modified and implemented in various forms. [Example]

[0074] [Example A] Tires having the tread pattern of FIG. 2 and the first to fourth groove walls of Table 1 were produced (Examples 1 and 2, and Comparative Examples 1 to 5). Each of the produced tires was evaluated for cornering performance on ice and snow. The specifications of each tire were the same except for the configuration shown in Table 1, and the tire sizes and other specifications were as follows. The test method was also as follows. The test results are shown in Table 1. Tire size: 215 / 55R16 Rim size: 16 x 6.5J Internal pressure: 230kPa Vehicle: Passenger car (front-wheel drive: 2000cc displacement) Tire mounting position: All wheels First circumferential groove: Groove width W1: 5.0mm Groove depth D1: 9.1 mm Second circumferential groove: Groove width: W2: 5.0mm Groove depth D2: 9.1 mm

[0075] <Turning performance on ice> The handling stability and cornering grip of the above vehicle when it was turned on an icy road were evaluated by the driver. The results are expressed as a score based on Comparative Example 1 being 100, with a higher score indicating better cornering performance on ice.

[0076] <Turning performance on snow> The handling stability and cornering grip of the above vehicle when it was turned on a snowy road were evaluated by the driver. The results are expressed as a score with Comparative Example 1 being 100, with a higher score indicating better cornering performance on snow.

[0077] [Table 1]

[0078] As a result of the test, the Examples showed improved cornering performance on snow compared to the Comparative Examples. Furthermore, the Examples had increased rigidity in the tread portion (land portion) compared to the Comparative Examples, improving cornering performance on ice. Furthermore, Example 2, in which the first groove wall and the third groove wall included portions extending parallel to the tread normal, was able to increase the groove volume compared to Example 1, which did not include parallel portions, improving cornering performance on snow.

[0079] [Example B] Tires were prototyped (Example 1, Examples 3 to 8) having the tread pattern of Fig. 2, the cross-sectional view of the circumferential groove of Fig. 3, and the first to fourth groove walls of Table 1. The cornering performance on ice and snow was evaluated for each prototype tire. The specifications of each tire were the same except for the configuration shown in Table 2, and the common specifications such as tire size and test method were the same as those of Example A.

[0080] [Table 2]

[0081] As a result of the test, the Examples had improved turning performance on ice and snow compared to the Comparative Examples shown in Table 1. Furthermore, Examples 1, 3, and 4, in which the first angle and the third angle were set within the preferred ranges, had improved turning performance on snow compared to Example 5, in which the first angle and the third angle were set outside the preferred ranges.

[0082] Examples 1 and 2, in which the difference (θ1-θ2) between the first angle θ1 and the second angle θ2 and the difference (θ3-θ4) between the third angle θ3 and the fourth angle θ4 were set within the preferred ranges, showed improved turning performance on snow compared to Examples 4 and 5, in which the difference was set outside the preferred ranges. Also, Examples 6 and 7, in which (θ3-θ4)-(θ1-θ2) was set within the preferred range, showed improved turning performance on snow compared to Examples 1 and 8, in which the difference was set outside the preferred ranges.

[0083] [Note] The present disclosure includes the following aspects.

[0084] [Disclosure 1] A tire having a tread portion, the tread portion includes a first circumferential groove extending continuously in the tire circumferential direction on a tread ground contact edge side, and a second circumferential groove adjacent to the first circumferential groove and extending continuously in the tire circumferential direction, The first circumferential groove includes a first groove wall located axially inside the tire and a second groove wall located axially outside the tire, the second circumferential groove includes a third groove wall located axially inside the tire and a fourth groove wall located axially outside the tire, the first groove wall includes a portion inclined radially inward and axially outward with respect to a tread normal line set at the groove edge, and has a first angle θ1 with respect to the tread normal line, the second groove wall includes a portion inclined radially inward and axially inward with respect to a tread normal line erected at the groove edge, and has a second angle θ2 with respect to the tread normal line, the third groove wall includes a portion inclined radially inward and axially outward with respect to a tread normal line erected at the groove edge, and has a third angle θ3 with respect to the tread normal line, the fourth groove wall includes a portion inclined radially inward and axially inward with respect to a tread normal line erected at the groove edge, and has a fourth angle θ4 with respect to the tread normal line, A tire, wherein the first to fourth angles θ1 to θ4 satisfy the following formulas: θ1>θ2 …(1) θ3>θ4 …(2) (θ3-θ4)>(θ1-θ2) …(3) [Disclosure 2] The tire described in Disclosure 1, wherein the first groove wall includes a portion extending parallel to the tread normal. [Disclosure 3] The tire according to Disclosure 1 or 2, wherein the third groove wall includes a portion extending parallel to the tread normal. [Disclosure 4] The tire according to any one of Disclosures 1 to 3, wherein the first angle θ1 and the third angle θ3 are less than 25°. [Disclosure 5] The tire according to any one of Disclosures 1 to 4, wherein the difference (θ1−θ2) between the first angle θ1 and the second angle θ2 is less than 15°. [Disclosure 6] The tire according to any one of Disclosures 1 to 5, wherein the difference (θ3−θ4) between the third angle θ3 and the fourth angle θ4 is less than 15°. [Disclosure 7] The tire according to any one of Disclosures 1 to 6, wherein the first to fourth angles θ1 to θ4 further satisfy the following formula: 5°<(θ3-θ4)-(θ1-θ2)<10° …(4) [Disclosure 8] The tire according to any one of the first to seventh disclosures, wherein the tread portion is provided with a plurality of sipes. [Disclosure 9] The tread portion has a specified orientation for installation on a vehicle, The tire according to any one of Present Disclosures 1 to 8, wherein the first circumferential groove is a circumferential groove located outermost on the vehicle when mounted on the vehicle. [Disclosure 10] The tread portion further includes a third circumferential groove provided adjacent to the second circumferential groove, the third circumferential groove includes a fifth groove wall located on the vehicle inner side and a sixth groove wall located on the vehicle outer side, the fifth groove wall includes a portion inclined radially inward and outward from the vehicle with respect to a tread normal line set at the groove edge, and has a fifth angle θ5 with respect to the tread normal line, the sixth groove wall includes a portion inclined radially inward and toward the vehicle inner side with respect to a tread normal line established at the groove edge, and has a sixth angle θ6 with respect to the tread normal line, The tire according to the present disclosure 9, wherein the first angle θ1, the second angle θ2, the fifth angle θ5, and the sixth angle θ6 satisfy the following formulas. θ5>θ6 … (5) (θ5-θ6)>(θ1-θ2) …(6) [Explanation of symbols]

[0085] 1 tire 2 Tread section 3 First circumferential groove 4 Second circumferential groove 11 First trench wall 12 Second groove wall 13 Third trench wall 14 Fourth Groove Wall

Claims

1. A tire having a tread portion, the tread portion includes a first circumferential groove extending continuously in the tire circumferential direction on a tread ground contact edge side, and a second circumferential groove adjacent to the first circumferential groove and extending continuously in the tire circumferential direction, the first circumferential groove includes a first groove wall located axially inside the tire and a second groove wall located axially outside the tire, the second circumferential groove includes a third groove wall located axially inside the tire and a fourth groove wall located axially outside the tire, the first groove wall includes a portion inclined radially inward and axially outward with respect to a tread normal line established at the groove edge, and has a first angle θ1 with respect to the tread normal line; the second groove wall includes a portion inclined radially inward and axially inward with respect to a tread normal line erected at the groove edge, and has a second angle θ2 with respect to the tread normal line, the third groove wall includes a portion inclined radially inward and axially outward with respect to a tread normal line erected at the groove edge, and has a third angle θ3 with respect to the tread normal line, the fourth groove wall includes a portion inclined radially inward and axially inward with respect to a tread normal line erected at the groove edge, and has a fourth angle θ4 with respect to the tread normal line, The first to fourth angles θ1 to θ4 satisfy the following formulas: θ1>θ2 ... (1) θ3>θ4 ... (2) (θ3-θ4)>(θ1-θ2)...(3)

2. The tire of claim 1 , wherein the first groove wall includes a portion extending parallel to the tread normal.

3. The tire according to claim 1 or 2, wherein the third groove wall includes a portion extending parallel to the tread normal.

4. The tire according to claim 1 , wherein the first angle θ1 and the third angle θ3 are less than 25°.

5. The tire according to any one of claims 1 to 4, wherein a difference (θ1-θ2) between the first angle θ1 and the second angle θ2 is less than 15°.

6. The tire according to any one of claims 1 to 5, wherein a difference (θ3-θ4) between the third angle θ3 and the fourth angle θ4 is less than 15°.

7. The tire according to any one of claims 1 to 6, wherein the first to fourth angles θ1 to θ4 further satisfy the following formula: 5°<(θ3-θ4)-(θ1-θ2)<10°…(4)

8. The tire according to claim 1 , wherein the tread portion is provided with a plurality of sipes.

9. The tread portion has a specified orientation for installation on a vehicle, The tire according to claim 1 , wherein the first circumferential groove is a circumferential groove located outermost on a vehicle when the tire is mounted on the vehicle.

10. The tread portion further includes a third circumferential groove provided adjacent to the second circumferential groove, the third circumferential groove includes a fifth groove wall located on a vehicle inner side and a sixth groove wall located on a vehicle outer side, the fifth groove wall includes a portion inclined radially inward and outward from the vehicle with respect to a tread normal line that is set at the groove edge, and has a fifth angle θ5 with respect to the tread normal line, the sixth groove wall includes a portion inclined radially inward and toward the vehicle inner side with respect to a tread normal line that is set at the groove edge, and has a sixth angle θ6 with respect to the tread normal line, The tire according to claim 9 , wherein the first angle θ1, the second angle θ2, the fifth angle θ5, and the sixth angle θ6 satisfy the following formula: θ5>θ6 … (5) (θ5-θ6)>(θ1-θ2)...(6)

Images