tire

Abstract

To provide a tire capable of improving maneuverability during cornering while ensuring drainage performance. [Solution] The tire has a specified mounting direction relative to a vehicle and is provided with a tread portion 3 including main grooves 10 extending continuously along the tire circumferential direction and land portions 20 partitioned by the main grooves 10. A belt including belt cords is embedded in the tread portion 3. The ratio (WGi / WLi) of the sum of the widths of the main grooves 10 WGi to the sum of the widths of the land portions 20 WLi in an inner region IN is greater than the ratio (WGo / WLo) of the sum of the widths of the main grooves 10 WGo to the sum of the widths of the land portions 20 WLo in an outer region OUT, and the outer region OUT is provided with the widest main groove of all the main grooves 10 included in the tread portion 3. The inclination angle θs of the belt cords in the shoulder regions with respect to the tire circumferential direction is greater than the inclination angle θc of the belt cords in the center region with respect to the tire circumferential direction.

Description

[Technical Field]

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

[0002] A tread pattern is provided on the tread portion of a tire to improve drainage performance and maneuverability. Generally, increasing the groove area is effective for improving drainage performance, while increasing the land area is effective for improving maneuverability during cornering, and in this respect, drainage performance and maneuverability tend to be mutually exclusive. The tire described in Patent Document 1 has different contact patch shapes between the region of the tread portion facing the inside of the vehicle and the region facing the outside of the vehicle, but does not suggest a means for solving the above-mentioned trade-off. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2024-73881 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present disclosure is to provide a tire that can improve maneuverability during cornering while ensuring drainage performance. [Means for solving the problem]

[0005] The tire of the present disclosure has a specified mounting direction on a vehicle, and includes a tread portion including main grooves extending continuously along the tire circumferential direction and land portions partitioned by the main grooves, and a belt including belt cords is embedded in the tread portion. When the region from the vehicle-inside ground-contact edge of the tread portion to the tire equator is referred to as an inner region, and the region from the vehicle-outside ground-contact edge of the tread portion to the tire equator is referred to as an outer region, a ratio (WGi / WLi) of a sum of main groove widths WGi to a sum of land portion widths WLi in the inner region is greater than a ratio (WGo / WLo) of a sum of main groove widths WGo to a sum of land portion widths WLo in the outer region, and the outer region is provided with the widest main groove of the main grooves included in the tread portion. When the area outside the groove width center of the shoulder main groove located at the outermost position in the tire width direction among the main grooves is called the shoulder region, and the area inside the groove width center of the shoulder main groove is called the center region, the inclination angle θs of the belt cord with respect to the tire circumferential direction in the shoulder region is larger than the inclination angle θc of the belt cord with respect to the tire circumferential direction in the center region. [Brief explanation of the drawings]

[0006] [Figure 1] 1 is a tire meridian cross-sectional view schematically showing a tire according to an embodiment of the present invention; [Figure 2] Development diagram showing the belt and belt reinforcement [Figure 3] A development view showing an example of a tread pattern [Figure 4] (A) An enlarged view showing a main part of the shoulder land portion, (B) a cross-sectional view of the lug groove taken along the arrow XX in FIG. 4(A), and (C) a cross-sectional view of the lug groove taken along the arrow YY in FIG. 4(A). [Figure 5] Cross-sectional view of the land area seen from the circumferential direction of the tire during cornering DETAILED DESCRIPTION OF THE INVENTION

[0007] An embodiment of the present disclosure will be described with reference to the drawings.

[0008] [Tire Overview] The tire T shown in FIG. 1 is a pneumatic tire for automobiles that includes a pair of bead portions 1, sidewall portions 2 extending radially outward from each of the bead portions 1, and a tread portion 3 that continues to the radially outer ends of each of the sidewall portions 2. An annular bead core 1a is embedded in the bead portion 1. The bead core 1a is formed by rubber-coating a bundle of steel wire or the like. A bead filler 1b is disposed radially outward from the bead core 1a. The bead filler 1b is formed of rubber with a triangular cross section that extends radially outward from the bead core 1a.

[0009] Here, the tire radial direction is the direction along the diameter of the tire T. The side closer to the central axis (axis of rotation) of the tire T is the inner side in the tire radial direction, and the side away from the central axis of the tire T is the outer side in the tire radial direction. The tire circumferential direction is the direction around the central axis of the tire T. The tire width direction is the direction parallel to the central axis of the tire T. The side closer to the tire equator TE is the inner side in the tire width direction, and the side away from the tire equator TE is the outer side in the tire width direction. The tire equator TE is located at the center of the tire T in the tire width direction, and is an imaginary line that is perpendicular to the central axis of the tire T when viewed from the outer side in the tire radial direction.

[0010] The tire T includes a carcass 4 extending in a toroidal shape across a pair of bead portions 1. The carcass 4 is wound up from the inner side to the outer side in the tire width direction so as to sandwich the bead core 1a and the bead filler 1b. The carcass 4 is formed of a carcass ply formed by rubber-coating carcass cords. The carcass cords are aligned in a direction intersecting the tire circumferential direction. The inclination angle of the carcass cords with respect to the tire circumferential direction is, for example, 75 to 90 degrees. Metals such as steel and organic fibers such as polyester, rayon, nylon, and aramid are preferably used as materials for the carcass cords.

[0011] The tire T includes a belt 5 embedded in the tread portion 3. The belt 5 is layered on the outer side of the carcass 4 in the tire radial direction. The belt 5 is formed of a plurality of belt plies layered on top of each other, and in this embodiment, is formed of two belt plies 5a, 5b. As shown in FIG. 2, the belt plies 5a, 5b are each formed by rubber-coating belt cords 5C. The belt cords 5C are aligned in a direction inclined with respect to the tire circumferential direction. The belt plies 5a, 5b are layered such that the belt cords 5C cross each other in opposite directions between them. A metal such as steel is preferably used as the material for the belt cords 5C.

[0012] The tire T includes a belt reinforcing material 6 laminated on the tire radially outer side of the belt 5. As shown in FIG. 2, the belt reinforcing material 6 is formed of a belt reinforcing ply formed by rubber-coating belt reinforcing cords 6C. The belt reinforcing cords 6C are aligned substantially parallel to the tire circumferential direction. The belt reinforcing ply is formed, for example, by spirally winding one or more rubber-coated belt reinforcing cords 6C along the tire circumferential direction. The belt reinforcing cords 6C are preferably made of the organic fiber described above. In this embodiment, the belt reinforcing material 6 covers the entire belt 5, but it may also have a structure in which it covers only both ends of the belt 5. Note that FIG. 2 is a schematic drawing, and the actual cords 5C, 6C are arranged more densely.

[0013] The tire T includes an inner liner 7 provided on the inner surface of the tire T. The inner liner 7 is formed of rubber with excellent air blocking properties, such as butyl rubber. The inner liner 7 has a function of maintaining the internal pressure of the tire T.

[0014] The tire T is a mounting direction specified tire in which the mounting direction relative to the vehicle is specified. An indication specifying the mounting direction relative to the vehicle is provided on the outer surface of the tire T. The mounting direction is specified, for example, by providing an indication indicating that the tire faces the inside of the vehicle (e.g., "INSIDE") on the outer surface of the sidewall portion 2 that is disposed on the inside of the vehicle when mounted on the vehicle, and / or by providing an indication indicating that the tire faces the outside of the vehicle (e.g., "OUTSIDE") on the outer surface of the sidewall portion 2 that is disposed on the outside of the vehicle when mounted on the vehicle.

[0015] [Tread pattern overview] The tire T has a tread pattern on the outer peripheral surface of a tread portion 3 as shown in FIG. 3. The tread pattern is formed by repeating substantially the same pattern in the tire circumferential direction, and the symbol L indicates the length of the minimum unit of repetition (pattern pitch). As shown in FIG. 3, the tire T has a tread pattern that is formed asymmetrically with respect to the tire equator TE. The tread portion 3 includes main grooves 10 that extend continuously along the tire circumferential direction and land portions 20 defined by the main grooves 10. A wear indicator may be provided in the main groove 10.

[0016] The main groove 10 has a width W10 that is 3% or more of the contact width CW. The width W10 is, for example, 10% or less of the contact width CW. As an example, the main groove 10 has a width W10 of 4.0 mm or more and a depth D10 of 5.0 mm or more. The groove width is determined as the distance between the intersections of the surface of the land portion 20 and the groove wall, along a direction perpendicular to the extension direction (length direction) of the groove. When the width varies along the extension direction, as in the shoulder main groove 13 described below, the minimum value is adopted as the width W10. In this embodiment, the main groove 10 is formed as a straight groove that extends linearly. The shoulder main groove 13 is also a straight groove, but has a chamfered portion 13c (see FIG. 4(A)) whose width varies along the tire circumferential direction, so that the groove edge is inclined with respect to the tire circumferential direction.

[0017] Unless otherwise specified, all dimensions of tire T are measured with tire T mounted on a standard rim, inflated to standard internal pressure, and no load. A standard rim is the rim specified for each tire in the standard system, including the standard on which the tire is based. JATMA calls it the "standard rim," and TRA and ETRTO call it the "measuring rim." Standard internal pressure is the air pressure specified for each tire in the standard system, including the standard on which the tire is based. For truck and bus tires and light truck tires, JATMA calls it the "maximum air pressure," TRA calls it the maximum value listed in the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" table, and ETRTO calls it the "INFLATION PRESSURE." For passenger car tires, the standard pressure is usually 180 kPa, but for tires labeled "Extra Load" or "Reinforced," it is 220 kPa.

[0018] The contact width CW is the distance in the tire width direction between a pair of contact edges CE. The contact edges CE are the outermost positions in the tire width direction of the contact patch when a tire T mounted on a standard rim, inflated to the standard internal pressure, placed vertically on a flat road surface, and subjected to a standard load. The standard load is the load determined for each tire by each standard in the standard system including the standard on which the tire is based. In JATMA, it is called the "maximum load capacity," in TRA, it is called the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES," and in ETRTO, it is called the "LOAD CAPACITY." For passenger car tires, it is called a load equivalent to 88% of the above loads.

[0019] In this embodiment, the tread portion 3 includes three main grooves 10 and four land portions 20 defined by the three main grooves 10. The three main grooves 10 include a pair of shoulder main grooves 11, 13 located on the outermost sides in the tire width direction, and a center main groove 12 located between the pair of shoulder main grooves 11, 13. The four land portions 20 include a pair of shoulder land portions 21, 24 located on the outer sides of the shoulder main grooves 11, 13 in the tire width direction, and a pair of center land portions 22, 23 located between the shoulder main grooves 11, 13 and the center main groove 12. The shoulder land portions 21, 24 each include a ground contact edge CE. The shoulder land portion 24 has the largest width of the four land portions 20.

[0020] In this embodiment, the tread portion 3 includes lug grooves 30 (lug grooves 31 to 33) extending in a direction intersecting the tire circumferential direction. The lug grooves 30 have a width exceeding 1.5 mm, and preferably have a width of 1.8 mm or more. The lug grooves 30 preferably have a maximum depth of 3.0 mm or more, and more preferably 4.0 mm or more. The maximum depth of the lug grooves 30 is preferably equal to or less than the depth D10 of the main grooves 10. The tread portion 3 may have a structure that does not include the lug grooves 30.

[0021] In this embodiment, the tread portion 3 includes cut-like sipes 40 (sipes 41 to 44). The sipes 41 to 44 each extend in a direction intersecting the tire circumferential direction. The sipes 40 have a width of 1.5 mm or less. The sipes 40 preferably have a maximum depth of 3.0 mm or more, more preferably 4.0 mm or more. The maximum depth of the sipes 40 is preferably equal to or less than the depth D10 of the main groove 10. The sipes 40 may be either two-dimensional sipes or three-dimensional sipes. The tread portion 3 may have a structure that does not include the sipes 40.

[0022] In this embodiment, the tread portion 3 includes shallow grooves 50 recessed to a depth of less than 3 mm. The depth of the shallow grooves 50 is, for example, 1 mm or more. The tread portion 3 may have a structure that does not include the shallow grooves 50.

[0023] In this embodiment, the tread portion 3 includes narrow grooves 60 that extend continuously along the tire circumferential direction and have a width smaller than that of the main grooves 10. The width W60 of the narrow grooves 60 is, for example, less than 4.0 mm, and preferably 3.0 mm or less. The width W60 is, for example, 1 mm or more. The narrow grooves 60 preferably have a maximum depth of 3.0 mm or more, more preferably more than 4.0 mm. The maximum depth of the narrow grooves 60 is preferably equal to or smaller than the depth D10 of the main grooves 10. The tread portion 3 may have a structure that does not include the narrow grooves 60.

[0024] The section from the ground contact edge CE on the vehicle inner side of the tread portion 3 to the tire equator TE is called the inner region IN, and the section from the ground contact edge CE on the vehicle outer side of the tread portion 3 to the tire equator TE is called the outer region OUT. The inner region IN and the outer region OUT each have a width that is half the ground contact width CW (CW / 2). Each of the inner region IN and the outer region OUT includes at least one main groove 10. The inner region IN is provided with a shoulder land portion 21, a shoulder main groove 11, a center land portion 22, and a center main groove 12. The outer region OUT is provided with a center land portion 23, a shoulder main groove 13, and a shoulder land portion 24. However, part of the center land portion 23 extends into the inner region IN, and the tire equator TE is set on the center land portion 23.

[0025] The shoulder region Sh is the region outside the groove width centers 11c, 13c of the shoulder main grooves 11, 13 that are located at the outermost positions in the tire width direction among the main grooves 10, and the center region Ce is the region inside the groove width centers 11c, 13c of the shoulder main grooves 11, 13. Of the four land portions 20, the shoulder land portions 21, 24 are provided in the shoulder region Sh, and the center land portions 22, 23 are provided in the center region Ce.

[0026] In the tire T of the present embodiment, the ratio (WGi / WLi) of the total width WGi of the main grooves 10 to the total width WLi of the land portions 20 in the inner region IN is larger than the ratio (WGo / WLo) of the total width WGo of the main grooves 10 to the total width WLo of the land portions 20 in the outer region OUT. Moreover, in the outer region OUT, the widest main groove (shoulder main groove 13) among the main grooves 10 included in the tread portion 3 is provided. Nevertheless, as shown in FIG. 2, the inclination angle θs of the belt cord 5C with respect to the tire circumferential direction in the shoulder region Sh is larger than the inclination angle θc of the belt cord 5C with respect to the tire circumferential direction in the center region Ce (θs > θc).

[0027] In the present embodiment, the total width WGi of the main grooves 10 in the inner region IN is the sum of the width W11 of the shoulder main groove 11 and the width W12 of the center main groove 12. The total width WLi of the land portions 20 in the inner region IN is obtained by subtracting the total width WGi of the main grooves 10 from the width (CW / 2) of the inner region IN. Further, the total width WGo of the main grooves 10 in the outer region OUT is the width W13 of the shoulder main groove 13. The total width WLo of the land portions 20 in the outer region OUT is obtained by subtracting the total width WGo of the main grooves 10 from the width (CW / 2) of the outer region OUT. The shoulder main groove 13 is the widest among the three main grooves 10. That is, the relationship W11 < W13 is satisfied, and the relationship W12 < W13 is satisfied.

[0028] The tire T of this embodiment satisfies the relationship (WGi / WLi) > (WGo / WLo), and has an inner region IN where the total width of the main grooves 10 is relatively large, and an outer region OUT where the total width of the land portions 20 is relatively large. Therefore, in the inner region IN, where the contact length tends to be large due to the negative camber when mounted on a vehicle, drainage by the main grooves 10 is promoted, ensuring drainage performance. Furthermore, in the outer region OUT, which contributes greatly to cornering, collapse of the land portions 20 when a lateral force is applied is suppressed, thereby improving cornering dynamics. Furthermore, the outer region OUT is provided with the widest shoulder main grooves 13, and this configuration helps to suppress a decrease in drainage performance in the outer region OUT, where the total width of the main grooves 10 is relatively small. Furthermore, in this tire T, by satisfying the relationship θs > θc, the circumferential restraining force of the belt 5 in the tire circumferential direction is relatively small in the shoulder region Sh, which facilitates contact between the shoulder land portions 21, 24 and the ground, thereby increasing the contact area during cornering and improving dynamics. Therefore, according to the tire T of this embodiment, it is possible to improve the maneuverability during cornering while ensuring the drainage performance.

[0029] From the viewpoint of ensuring an improved effect on maneuverability during cornering, the difference (θs-θc) between the inclination angle θs and the inclination angle θc is preferably 1 degree or more. The difference (θs-θc) is, for example, 5 degrees or less, preferably 3 degrees or less, and more preferably 2 degrees or less. The inclination angle θc is, for example, 20 to 30 degrees, and preferably 22 to 27 degrees. The inclination angles θs and θc are each determined as the acute angle with respect to the tire circumferential direction. The inclination angle of the belt cord 5C preferably varies within the range of widths W11 and W13, and in this embodiment, it varies with groove width centers 11c and 13c as boundaries. The inclination angles θs and θc are preferably determined as the angle of the belt cord 5C arranged in the portion overlapping with the land portion 20.

[0030] In this embodiment, the inclination angle θs is set to be larger than the inclination angle θc in both of the pair of shoulder regions Sh. This configuration improves the left-right balance of the belt 5, contributing to improved steering stability. However, the present invention is not limited to this configuration, and the inclination angle θs may be set to be larger than the inclination angle θc in only one of the pair of shoulder regions Sh. However, because the outer region OUT contributes more to cornering, it is preferable to set the inclination angle θs to be larger than the inclination angle θc in at least the shoulder region Sh included in the outer region OUT.

[0031] In this embodiment, the ratio (AVi / ASi) of the sum of the void areas AVi to the sum of the see-through void areas ASi in the inner region IN is smaller than the ratio (AVo / ASo) of the sum of the void areas AVo to the sum of the see-through void areas ASo in the outer region OUT. That is, the relationship (WGi / WLi)>(WGo / WLo) is satisfied, while the relationship (AVi / ASi)<(AVo / ASo) is satisfied.

[0032] A void is a depression formed on the surface of the land portion 20. In this embodiment, the main groove 10, lug grooves 30, sipes 40, shallow grooves 50, and narrow grooves 60 correspond to voids. A see-through void is a void that has a width of 1 mm or more and a depth of 3 mm or more, and can be seen through when viewed circumferentially of the tire without being obstructed by groove walls. In this embodiment, the main groove 10 and narrow groove 60 correspond to see-through voids. However, in the shoulder main groove 13, the portion that corresponds to a see-through void is the portion from the groove edge on the inner side in the tire width direction to a width W13, excluding the portion obstructed by groove walls when viewed circumferentially of the tire.

[0033] The ratio of the area of ​​the see-through void (opening area) to the area of ​​the contact surface is called the "see-through void ratio." The see-through void ratio in the inner area (IN) is calculated as a fraction with "L(CW / 2)" as the denominator and "L(W11+W12)" as the numerator. The see-through void ratio in the outer area (OUT) is calculated as a fraction with "L(CW / 2)" as the denominator and "L(W13+W60)" as the numerator.

[0034] The ratio of the area of ​​the voids (open area) to the area of ​​the contact patch is called the "void ratio." The void ratio in the inner region (IN) is calculated as a fraction with "L(CW / 2)" as the denominator and the sum of the areas of the voids (i.e., the main grooves 11 and 12, the lug grooves 31 and 32, and the sipes 41 and 42) within the length L of the inner region (IN) as the numerator. The above ratio (AVi / ASi) corresponds to the ratio of the void ratio to the see-through void ratio in the inner region (IN). The void ratio in the outer region (OUT) is calculated as a fraction with "L(CW / 2)" as the denominator and the sum of the areas of the voids (i.e., the main grooves 13, the lug grooves 33, the sipes 43 and 44, the shallow grooves 50, and the thin grooves 60) within the length L of the outer region (OUT) as the numerator. The above ratio (AVo / ASo) corresponds to the ratio of the void ratio to the see-through void ratio in the outer region (OUT).

[0035] As described above, the tire T of this embodiment satisfies the relationship (AVi / ASi)<(AVo / ASo), and has, so to speak, an inner region IN with relatively few voids other than see-through voids and an outer region OUT with relatively many voids other than see-through voids. Therefore, in the inner region IN, which contributes greatly to straight-line running, the rigidity of the land portion 20 in the tire circumferential direction is ensured, increasing the driving force and improving the maneuverability during straight-line running. Furthermore, in the outer region OUT, although the total width of the main grooves 10 is relatively small, the voids other than see-through voids promote drainage in the tire width direction, ensuring drainage performance.

[0036] The sum of the widths of the main grooves 10 in the inner region IN, WGi, may be smaller than the sum of the widths of the land portions 20, WLi, for example, satisfying the relationship WGi:WLi = 1:2.5 to 4. The sum of the widths of the main grooves 10 in the outer region OUT, WGo, may be smaller than the sum of the widths of the land portions 20, WLo, for example, satisfying the relationship WGo:WLo = 1:4.5 to 7. The sum of the areas of the see-through voids in the inner region IN, ASi, may be smaller than the sum of the areas of the voids, AVi, for example, satisfying the relationship ASi:AVi = 1:1.05 to 1.35. The sum of the areas of the see-through voids in the outer region OUT, ASo, may be smaller than the sum of the areas of the voids, AVo, for example, satisfying the relationship ASo:AVo = 1:1.4 to 1.75.

[0037] [Inner area] The shoulder land portion 21 includes lug grooves 31 and sipes 41 extending in a direction intersecting the tire circumferential direction. The lug grooves 31 extend outward in the tire width direction from the shoulder main grooves 11 serving as the main grooves 10 and are closed within the land portion 20. The shoulder land portion 21 is not divided by the lug grooves 31 and is provided as a rib extending continuously in the tire circumferential direction. In the shoulder land portion 21, sipes 41 extending outward in the tire width direction from the closed ends of the lug grooves 31 and sipes 41 extending outward in the tire width direction from the shoulder main grooves 11 are arranged alternately in the tire circumferential direction, and all reach the contact edge CE. The sipes 41 are curved in a direction that convexly curves in the tire circumferential direction.

[0038] The center land portion 22 includes lug grooves 32 and sipes 42 extending in a direction intersecting the tire circumferential direction. The lug grooves 32 extend inward in the tire width direction from the shoulder main grooves 11 and are closed within the land portion 20. The center land portion 22 is not divided by lug grooves 33 and is provided as a rib extending continuously in the tire circumferential direction. In the center land portion 22, relatively short lug grooves 32 and relatively long lug grooves 32 are alternately arranged in the tire circumferential direction. The lug grooves 32 are smoothly connected to the lug grooves 31 via the shoulder main grooves 11. "Two lug grooves 30 are smoothly connected via the main grooves 10" refers to a state in which an imaginary line extending from the center of one groove width in the length direction and an imaginary line extending from the center of the other groove width in the length direction overlap within the main groove 10 or are close enough to each other that the distance between them in the tire circumferential direction is 2.0 mm or less. The sipes 42 extend inward in the tire width direction from the closed ends of the lug grooves 32 and are closed within the land portions 20 .

[0039] In this embodiment, the groove width center 12c of the center main groove 12, which is the main groove closest to the tire equator TE among the main grooves 10 included in the tread portion 3, is located in the inner region IN. As described above, the contact length during straight running tends to be longer in the inner region IN, so by moving the center main groove 12 closer to the inner region IN, better drainage performance can be ensured. In the case of such a configuration, it is preferable that the number of main grooves 10 provided in the tread portion 3 is an odd number (e.g., three or five). In this example, each of a pair of groove edges in the center main groove 12 is located in the inner region IN, and no main groove 10 is provided on the tire equator TE.

[0040] [Outer area] The center land portion 23 includes sipes 43 and shallow grooves 50. The center land portion 23 does not include lug grooves and is provided as a rib extending continuously in the tire circumferential direction. The sipes 43 extend inward in the tire width direction from the shoulder main grooves 13 serving as the main grooves 10 and are closed within the land portion 20. The closed ends of the sipes 43 are not connected to the shallow grooves 50. The shallow grooves 50 have a first portion 51 extending along the tire circumferential direction and a second portion 52 extending inward in the tire width direction from the first portion 51. The second portion 52 extends in a direction inclined with respect to the tire width direction and is closed within the land portion 20.

[0041] The shoulder land portion 24 includes lug grooves 33, sipes 44, and narrow grooves 60. The lug grooves 33 are tapered from the shoulder main grooves 13 outward in the tire width direction. The lug grooves 33 are closed within the land portion 20, and their depth decreases toward the closed ends (see FIG. 4). This suppresses a decrease in rigidity near the ground contact edge CE, thereby improving cornering performance. The shoulder land portion 24 is not divided by the lug grooves 33, but is provided as a rib extending continuously in the tire circumferential direction. In the shoulder land portion 24, sipes 44 extending outward in the tire width direction from near the lug grooves 33 and sipes 44 extending outward in the tire width direction from near the narrow grooves 60 are alternately arranged in the tire circumferential direction, and all of them reach the ground contact edge CE. The inner ends of the sipes 44 in the tire width direction are closed within the land portion 20 and are not connected to the lug grooves 33 or narrow grooves 60. The narrow grooves 60 intersect with the lug grooves 33.

[0042] During high-load cornering, the land portions 20 in the outer region OUT tend to deform significantly. In a tire T in which the width of the land portions 20 in the outer region OUT is relatively large, the deformation of the land portions 20 tends to cause localized concentration of ground contact pressure, which may result in a decrease in maneuverability. Therefore, in this embodiment, narrow grooves 60 that extend continuously along the tire circumferential direction and are narrower than the main grooves 10 are provided in the outer region OUT. By dividing the land portions 20 (shoulder land portions 24) with the narrow grooves 60 and narrowing their width, the local concentration of ground contact pressure that accompanies deformation during high-load cornering is suppressed (ground contact pressure is dispersed), which may contribute to improved maneuverability during cornering.

[0043] In this embodiment, the narrow grooves 60 are provided in the shoulder land portions 24, but not in the inner region IN. In the center land portion 23, which is narrower than the shoulder land portions 24, the first portions 51 of the shallow grooves 50 are provided instead of the narrow grooves 60. By dividing the land portion 20 (shoulder land portions 23) with (the first portions 51 of) the shallow grooves 50 and narrowing the width, it is possible to suppress a decrease in the rigidity of the land portion 20 (shoulder land portions 23), while suppressing local concentration of ground pressure due to deformation during high-load cornering (the ground pressure is dispersed), which can contribute to improved maneuverability during cornering.

[0044] In this embodiment, the sipes 44 provided in the shoulder land portion 24 in the outer region OUT are two-dimensional sipes. This eliminates the cavities and depth-direction bending of the sipe wall that are common in three-dimensional sipes, and prevents the formation of starting points for the land portion to collapse when the tire comes into contact with the road. This prevents a decrease in the rigidity of the sipe edge. Meanwhile, the sipes 41 provided in the shoulder land portion 21 in the inner region IN are three-dimensional sipes. This reduces the tire's circumferential collapse of the shoulder land portion 21 in the inner region IN, which contributes significantly to straight-line driving, thereby contributing to improved driving performance when driving straight. Here, a two-dimensional sipe is a sipe whose inner wall surface has a linear shape in a cross section perpendicular to the sipe's length. A three-dimensional sipe is a sipe whose inner wall surface includes a non-linear shape (e.g., a bent or curved shape) in a cross section perpendicular to the sipe's length.

[0045] In the outer region OUT, lug grooves 33 extending in a direction intersecting both the tire circumferential direction and the tire width direction are provided in the shoulder land portion 24, which is a land portion including the ground contact edge CE. Fig. 4(A) is an enlarged view showing the periphery of the lug groove 33. Figs. 4(B) and 4(C) are cross-sectional views of the lug groove 33 taken along the arrows XX and YY, respectively. The lug groove 33 has a groove bottom 33a and a pair of groove walls 33b and 33c. The angle of the groove wall 33b relative to the normal direction ND to the surface of the land portion 20 (shoulder land portion 24) is smaller than the angle of the groove wall 33c relative to the normal direction ND, and the lug groove 33 has an asymmetric cross-sectional shape with respect to its groove width center.

[0046] In this embodiment, the lug groove 33 has a groove wall 33b extending along the normal direction ND. As described above, the groove wall 33b has a smaller angle with respect to the normal direction ND than the groove wall 33c, which reduces the reduction in the groove width of the lug groove 33 that occurs with the progression of wear. Therefore, the effect of improving cornering performance by the lug groove 33, which will be described later, is prevented from decreasing with the progression of wear.

[0047] In this embodiment, the lug groove 33 has a groove wall 33c inclined with respect to the normal direction ND. This configuration suppresses localized lift deformation of the surface of the shoulder land portion 24 when a lateral force is applied, which can contribute to improving cornering performance. In contrast, if each of the pair of groove walls of the lug groove 33 extends along the normal direction ND, the surface 20s connected to the groove edge may locally lift off the road surface RS when a lateral force LF is applied, as shown in FIG. 5, which may reduce the effect of improving cornering performance. In this embodiment, the groove wall 33c is set to a portion extending a predetermined distance d (e.g., 0.5 mm or less) from the groove edge along the normal direction ND, but the shape may not include this portion.

[0048] 1, in this embodiment, the end 5e of the belt 5 is located further outward in the tire width direction than the lug grooves 33. The area where the belt 5 is located has higher rigidity than the area where the belt 5 is not located, and deformation of the land portion 20 is suppressed. Therefore, this configuration can promote uniformity of the ground contact pressure in the tire width direction of the shoulder land portion 24 where the lug grooves 33 are provided, and contribute to improving maneuverability during cornering.

[0049] Although not shown, the second portion 52 of the shallow groove 50 has a shape in which one of a pair of groove walls extends along the normal direction ND and the other is inclined with respect to the normal direction ND, similar to the lug groove 33. However, while the groove wall inclined with respect to the normal direction ND is located on one side in the tire circumferential direction in the lug groove 33, it is located on the other side in the tire circumferential direction in the second portion 52. The second portion 52 extends at an angle with respect to the tire width direction, and the direction of the inclination is the same as that of the lug groove 33. With this configuration, regardless of the rotation direction of the tire T, the effect of suppressing lift-up deformation is exerted by at least one of the lug groove 33 and the second portion 52, which can contribute to improving driving performance during cornering.

[0050] The tire of this embodiment is equivalent to a normal pneumatic tire, except that the widest main groove is provided in the outer region while satisfying the relationship (WGi / WLi) > (WGo / WLo) and the relationship θs > θc, and any of the conventionally known materials, shapes, structures, etc. can be employed. In the above-described embodiment, an example was shown in which the tread portion 3 includes three main grooves 10, but the number of main grooves 10 is not particularly limited and may be, for example, 3 to 6. The tread pattern is not limited to the shape shown in the above-described embodiment.

[0051] It will be understood by those skilled in the art that the above-described embodiments are examples of the following aspects.

[0052] [1] The tire of the present disclosure has a specified mounting direction on a vehicle, and includes a tread portion including main grooves extending continuously along the tire circumferential direction and land portions partitioned by the main grooves, and a belt including belt cords is embedded in the tread portion. When the region from the vehicle-inside ground-contact edge of the tread portion to the tire equator is referred to as an inner region, and the region from the vehicle-outside ground-contact edge of the tread portion to the tire equator is referred to as an outer region, a ratio (WGi / WLi) of a sum of main groove widths WGi to a sum of land portion widths WLi in the inner region is greater than a ratio (WGo / WLo) of a sum of main groove widths WGo to a sum of land portion widths WLo in the outer region, and the outer region is provided with the widest main groove of the main grooves included in the tread portion. When the area outside the groove width center of the shoulder main groove located at the outermost position in the tire width direction among the main grooves is called the shoulder region, and the area inside the groove width center of the shoulder main groove is called the center region, the inclination angle θs of the belt cord with respect to the tire circumferential direction in the shoulder region is larger than the inclination angle θc of the belt cord with respect to the tire circumferential direction in the center region.

[0053] By making the ratio (WGi / WLi) greater than the ratio (WGo / WLo), drainage by the main grooves is promoted in the inner region where the contact length tends to be large, ensuring drainage performance. Furthermore, in the outer region, which contributes more to cornering, collapse of the land portion when a lateral force is applied is suppressed, improving cornering maneuverability. Moreover, since the widest main groove is located in the outer region, a decrease in drainage performance is suppressed in the outer region where the total width of the main grooves is relatively small. Furthermore, since the inclination angle θs is greater than the inclination angle θc, the shoulder land portion is more likely to contact the ground, improving cornering maneuverability. Therefore, this tire can improve cornering maneuverability while ensuring drainage performance.

[0054] [2] In the tire of the above [1], from the viewpoint of ensuring an effect of improving maneuverability during cornering, the difference (θs−θc) between the inclination angle θs and the inclination angle θc may be 1 degree or more.

[0055] [3] In the tire of the above [1] or [2], the inclination angle θc may be 22 to 27 degrees.

[0056] [4] In the tire of any one of the above [1] to [3], the groove width center of the main groove closest to the tire equator among the main grooves included in the tread portion may be located in an inner region. With this configuration, better drainage performance can be ensured in the inner region where the contact length during straight running tends to be longer.

[0057] [5] In any one of the tires [1] to [4] above, the outer region may be provided with narrow grooves that extend continuously in the tire circumferential direction and have a width smaller than that of the main grooves. By dividing the land portions with narrow grooves and narrowing their widths, localized concentration of ground pressure due to deformation during high-load cornering is suppressed (ground pressure is dispersed), which can contribute to improved maneuverability during cornering.

[0058] [6] In any one of the tire [1] to [5] above, in the outer region, the land portion including the ground contact edge may be provided with lug grooves extending in a direction intersecting both the tire circumferential direction and the tire width direction, and the lug grooves may have groove walls inclined with respect to a normal direction to the surface of the land portion. With this configuration, local lift-up deformation of the surface of the land portion when a lateral force is applied can be suppressed, which can contribute to improving maneuverability during cornering.

[0059] [7] The tire T of [6] above may be configured to include a belt embedded in the tread portion, with the end of the belt positioned outward in the tire width direction from the lug grooves. This configuration can promote uniformity of ground contact pressure in the tire width direction in the land portions where the lug grooves are provided, and contribute to improving maneuverability during cornering.

[0060] Although the embodiments of the present disclosure have been described based on the drawings, it should be understood that the specific configuration is not limited to this embodiment. The scope of the present disclosure is indicated not only by the description of the above embodiments but also by the claims, and further includes all modifications within the meaning and scope equivalent to the claims.

[0061] The tire of the present disclosure is not limited to the above-described embodiment, and is not limited to the above-described effects. The tire of the present disclosure can be improved or modified in various ways without departing from the spirit of the tire. Furthermore, the configurations employed in the above-described embodiment can be combined in any desired manner. [Explanation of symbols]

[0062] 3 tread portion, 5 belt, 5C belt cord, 5e belt edge, 10 main groove, 20 land portion, 30 lug groove, 40 sipe, 50 shallow groove, 60 fine groove, Ce center region, IN inner region, OUT outer region, Sh shoulder region, T tire, TE tire equator

Claims

1. The mounting direction relative to the vehicle is specified, The tire has a tread portion including main grooves extending continuously along the tire circumferential direction and land portions defined by the main grooves, and a belt including belt cords is embedded in the tread portion, When the region from the ground contact edge on the vehicle inner side of the tread portion to the tire equator is referred to as an inner region, and the region from the ground contact edge on the vehicle outer side of the tread portion to the tire equator is referred to as an outer region, a ratio (WGi / WLi) of a sum of widths of the main grooves WGi to a sum of widths of the land portions WLi in the inner region is larger than a ratio (WGo / WLo) of a sum of widths of the main grooves WGo to a sum of widths of the land portions WLo in the outer region, and a main groove having the largest width among the main grooves included in the tread portion is provided in the outer region, When the shoulder region is defined as a region outside the groove width center of the shoulder main groove located at the outermost position in the tire width direction among the main grooves, and the center region is defined as a region inside the groove width center of the shoulder main groove in the tire width direction, a tilt angle θs of the belt cord in the shoulder region with respect to the tire circumferential direction is larger than a tilt angle θc of the belt cord in the center region with respect to the tire circumferential direction.

2. 2. The tire according to claim 1, wherein the difference (θs−θc) between the inclination angle θs and the inclination angle θc is 1 degree or more.

3. 2. The tire according to claim 1, wherein the inclination angle θc is 22 to 27 degrees.

4. The tire according to claim 1, wherein the groove width center of the main groove closest to the tire equator among the main grooves included in the tread portion is located in an inner region.

5. The tire according to claim 1 , wherein the outer region is provided with a narrow groove that extends continuously in the tire circumferential direction and has a width smaller than that of the main groove.

6. In the outer region, lug grooves extending in a direction intersecting both the tire circumferential direction and the tire width direction are provided in the land portion including the ground contact edge, The tire according to any one of claims 1 to 5, wherein the lug groove has a groove wall inclined with respect to a normal direction of the surface of the land portion.

7. A belt is embedded in the tread portion, The tire according to claim 6 , wherein an end of the belt is positioned outward in the tire width direction from the lug groove.

Images