tire

Abstract

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

Description

Technical Field

[0001] The present disclosure relates to a tire.

Background Art

[0002] A tread pattern is provided on the tread portion of a tire to enhance drainage performance and handling performance. Generally, increasing the groove area is effective for improving drainage performance, while increasing the land area is effective for improving handling performance during turning. In this regard, drainage performance and handling performance tend to be mutually contradictory. In the tire described in Patent Document 1, the shape of the ground contact surface is made different between the region on the inner side of the vehicle of the tread portion and the region on the outer side of the vehicle, but it does not suggest a solution to the above-mentioned contradictory relationship.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] [[ID=3�]] An object of the present disclosure is to provide a tire that can improve handling performance during turning while ensuring drainage performance.

Means for Solving the Problems

[0005] The tire of this disclosure has a specified mounting direction for a vehicle and comprises a tread portion including a main groove extending continuously along the circumferential direction of the tire and a land portion partitioned by the main groove, with a belt including a belt cord embedded in the tread portion. The area from the contact end on the vehicle side of the tread portion to the tire equator is called the inner region, and the area from the contact end on the vehicle side of the tread portion to the tire equator is called the outer region. The ratio of the sum of the widths of the main grooves WGi to the sum of the widths of the land portion WLi in the inner region (WGi / WLi) is greater than the ratio of the sum of the widths of the main grooves WGo to the sum of the widths of the land portion WLo in the outer region (WGo / WLo), and the outer region is provided with the main groove with the largest width among the main grooves included in the tread portion. When the area outside the center of the groove width of the shoulder main groove, which is the outermost of the main grooves in the tire width direction, is called the shoulder region, and the area inside the center of the groove width 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 greater than the inclination angle θc of the belt cord with respect to the tire circumferential direction in the center region. [Brief explanation of the drawing]

[0006] [Figure 1] A schematic cross-sectional view of the tire according to this embodiment. [Figure 2] Developed view showing the belt and belt reinforcement. [Figure 3] Developed diagram showing an example of a tread pattern. [Figure 4] (A) Enlarged view showing the main part of the shoulder land section, (B) Cross-sectional view of the lug groove along the direction of arrow XX in Figure 4(A), and (C) Cross-sectional view of the lug groove along the direction of arrow YY in Figure 4(A). [Figure 5] Cross-sectional view of the land area during a turn, seen from the tire circumferential direction. [Modes for carrying out the invention]

[0007] One embodiment of this disclosure will be described with reference to the drawings.

[0008] [Tire Overview] The tire T shown in Figure 1 is a pneumatic tire for automobiles, comprising a pair of bead portions 1, sidewall portions 2 extending radially outward from each of the bead portions 1, and tread portions 3 connected to the radially outward 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 covering a converging body such as steel wire with rubber. A bead filler 1b is positioned radially outward from the bead core 1a. The bead filler 1b is formed of triangular-shaped rubber extending radially outward from the bead core 1a.

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

[0010] The tire T comprises a carcass 4 that extends in a toroidal shape across a pair of bead portions 1. The carcass 4 is wound from the inside to the outside in the tire width direction, sandwiching the bead core 1a and bead filler 1b. The carcass 4 is formed from carcass plies formed by covering carcass cords with rubber. 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. Preferably, the material used for the carcass cords is metal such as steel, or organic fibers such as polyester, rayon, nylon, or aramid.

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

[0012] The tire T includes a belt reinforcement material 6 laminated on the radially outer side of the belt 5. As shown in Figure 2, the belt reinforcement material 6 is formed of belt reinforcement plies formed by rubber-coating belt reinforcement cords 6C. The belt reinforcement cords 6C are aligned substantially parallel to the circumferential direction of the tire. The belt reinforcement plies are formed, for example, by spirally winding one or more rubber-coated belt reinforcement cords 6C along the circumferential direction of the tire. The material for the belt reinforcement cords 6C is preferably the organic fibers described above. In this embodiment, the belt reinforcement material 6 completely covers the belt 5, but a structure that covers only both ends of the belt 5 is also possible. Note that Figure 2 is a schematic representation, and the actual cords 5C and 6C are arranged more densely.

[0013] The tire T is equipped with an inner liner 7 located on its inner surface. The inner liner 7 is made of a rubber with excellent air-shielding properties, such as butyl rubber. The inner liner 7 has the function of maintaining the internal pressure of the tire T.

[0014] Tire T is a directional tire whose mounting direction relative to the vehicle is specified. The outer surface of Tire T is provided with an indication that specifies the mounting direction relative to the vehicle. The mounting direction is specified, for example, by providing an indication (e.g., "INSIDE") on the outer surface of the sidewall portion 2 that is positioned on the inside of the vehicle when mounted, and / or by providing an indication (e.g., "OUTSIDE") on the outer surface of the sidewall portion 2 that is positioned on the outside of the vehicle when mounted, indicating that it is on the outside of the vehicle.

[0015] [Overview of Tread Pattern] The outer circumferential surface of the tread portion 3 of the tire T is provided with a tread pattern as illustrated in Figure 3. The tread pattern is formed by repeating substantially the same pattern in the circumferential direction of the tire, and the symbol L indicates the length of the smallest unit of repetition (pattern pitch). As shown in Figure 3, the tire T has a tread pattern formed asymmetrically with respect to the tire equator TE. The tread portion 3 includes a main groove 10 that extends continuously along the circumferential direction of the tire, and a land portion 20 partitioned by the main groove 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 width of the groove 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. In cases where the width changes along the extension direction, such as the shoulder main groove 13 described later, the minimum value is adopted as the width W10. In this embodiment, the main groove 10 is formed as a straight groove extending in a straight line. The shoulder main groove 13 is also a straight groove, but since it is provided with a chamfered portion 13c (see Figure 4(A)) whose width changes along the tire circumferential direction, its groove edge is inclined with respect to the tire circumferential direction.

[0017] Unless otherwise specified, the dimensions of the tire T are measured in an unloaded state with the tire T mounted on a standard rim and filled to the standard internal pressure. A standard rim is the rim specified for each tire in the standards system, including the standard on which the tire is based. In JATMA, this is called the "standard rim," and in TRA and ETRTO, it is called the "Measuring Rim." Standard internal pressure is the air pressure specified for each tire in the standards system, including the standard on which the tire is based. For truck and bus tires and light truck tires, this is the "maximum air pressure" in JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in TRA, and "INFLATION PRESSURE" in ETRTO. For passenger car tires, this is usually 180kPa, but for tires marked "Extra Load" or "Reinforced," it is 220kPa.

[0018] The contact patch width CW is the distance in the tire width direction between a pair of contact edges CE. The contact edge CE is the outermost position in the tire width direction of the contact surface when a tire T mounted on a standard rim is filled with standard internal pressure, placed perpendicular to a flat road surface, and a standard load is applied. Standard load refers to the load specified for each tire in the standards system, including the standard on which the tire is based. In JATMA it is the "maximum load capacity," in TRA it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES," and in ETRTO it is the "LOAD CAPACITY." However, in the case of passenger car tires, it is the load equivalent to 88% of the above load.

[0019] In this embodiment, the tread portion 3 includes three main grooves 10 and four land portions 20 partitioned by the three main grooves 10. The three main grooves 10 include a pair of shoulder main grooves 11 and 13 located on the outermost side in the tire width direction among them, and a center main groove 12 located between the pair of shoulder main grooves 11 and 13. The four land portions 20 include a pair of shoulder land portions 21 and 24 located on the outer side in the tire width direction of the shoulder main grooves 11 and 13, and a pair of center land portions 22 and 23 located between the shoulder main grooves 11 and 13 and the center main groove 12. The shoulder land portions 21 and 24 each include a grounding end CE. The shoulder land portion 24 has the largest width among 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, preferably a width of 1.8 mm or more. The lug grooves 30 preferably have a maximum depth of 3.0 mm or more, 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 groove 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 with 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 a narrow groove 60 that extends continuously along the circumferential direction of the tire and has a width smaller than the main groove 10. The width W60 of the narrow groove 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 groove 60 has a maximum depth of preferably 3.0 mm or more, more preferably more than 4.0 mm. The maximum depth of the narrow groove 60 is preferably equal to or less than the depth D10 of the main groove 10. The tread portion 3 may also have a structure that does not include the narrow groove 60.

[0024] The area from the contact edge CE on the vehicle side of the tread portion 3 to the tire equator TE is called the inner region IN, and the area from the contact edge CE on the vehicle side of the tread portion 3 to the tire equator TE is called the outer region OUT. Both the inner region IN and the outer region OUT have a width of half the 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, a 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 area outside the groove width centers 11c and 13c of the shoulder main grooves 11 and 13, which are the outermost shoulder main grooves in the tire width direction, is called the shoulder region Sh, and the area inside the groove width centers 11c and 13c of those shoulder main grooves 11 and 13 is called the center region Ce. Of the four land sections 20, the shoulder land sections 21 and 24 are located in the shoulder region Sh, and the center land sections 22 and 23 are located 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 in other words, it has an inner region IN where the sum of the widths of the main grooves 10 is relatively large, and an outer region OUT where the sum of the widths of the land portion 20 is relatively large. Therefore, in the inner region IN, where the contact length tends to be large due to negative camber when mounted on a vehicle, drainage by the main grooves 10 is promoted and drainage performance can be ensured. Furthermore, in the outer region OUT, where the contribution during turning is large, the collapse of the land portion 20 when lateral force is applied is suppressed, thereby improving the maneuverability during turning. Moreover, the outer region OUT is provided with the widest shoulder main groove 13, and this configuration helps to suppress the decrease in drainage performance in the outer region OUT, where the sum of the widths of the main grooves 10 is relatively small. In addition, in this tire T, by satisfying the relationship θs>θc, the restraining force in the circumferential direction of the tire by the belt 5 is relatively small in the shoulder region Sh, and as a result the shoulder land portions 21 and 24 make contact with the ground more easily, thereby increasing the ground area during turning and improving maneuverability. Therefore, according to the tire T of this embodiment, it is possible to improve the maneuverability during cornering while ensuring drainage performance.

[0029] From the viewpoint of ensuring improved maneuverability during turns, the difference between the inclination angle θs and the inclination angle θc (θs-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, preferably 22 to 27 degrees. The inclination angles θs and θc are determined as angles on the acute side with respect to the tire circumferential direction. The inclination angle of the belt cord 5C preferably changes within the range of widths W11 and W13, and in this embodiment, it changes with the groove width centers 11c and 13c as boundaries. The inclination angles θs and θc are preferably determined as angles of the belt cord 5C that is positioned in the part overlapping with the land portion 20.

[0030] In this embodiment, the inclination angle θs is greater than the inclination angle θc in both of the pair of shoulder regions Sh. With this configuration, the left-right balance of the belt 5 is improved, contributing to improved steering stability. However, it is not limited to this, and a configuration in which the inclination angle θs is greater than the inclination angle θc in only one of the pair of shoulder regions Sh is also acceptable. However, since the outer region OUT makes a large contribution during turning, it is preferable that the inclination angle θs is greater than the inclination angle θc in at least the shoulder region Sh included in the outer region OUT.

[0031] In this embodiment, the ratio of the total void area AVi to the total see-through void area ASi in the inner region IN (AVi / ASi) is smaller than the ratio of the total void area AVO to the total see-through void area ASo in the outer region OUT (AVo / ASo). 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 groove 30, sipe 40, shallow groove 50, and narrow groove 60 are 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 is visible in the circumferential direction of the tire without being obstructed by the groove wall. In this embodiment, the main groove 10 and narrow groove 60 are see-through voids. However, in the shoulder main groove 13, the see-through void is the portion with a width W13 from the groove edge on the inside in the tire width direction, excluding the portion that is obstructed by the groove wall when viewed in the circumferential direction 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 region IN is calculated by a fraction with "L(W11+W12)" as the numerator and "L(CW / 2)" as the denominator. The see-through void ratio in the outer region OUT is calculated by a fraction with "L(W13+W60)" as the numerator and "L(CW / 2)" as the denominator.

[0034] The ratio of the void area (opening area) to the area of ​​the contact surface is called the "void ratio". The void ratio in the inner region IN is calculated by a fraction with "L(CW / 2)" as the denominator and the sum of the areas of the voids (i.e., main grooves 11, 12, lug grooves 31, 32, and sipes 41, 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 by a fraction with "L(CW / 2)" as the denominator and the sum of the areas of the voids (i.e., main grooves 13, lug grooves 33, sipes 43, 44, shallow grooves 50, and narrow 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 so to speak, it has an inner region IN where there are relatively few voids other than see-through voids, and an outer region OUT where there are relatively many voids other than see-through voids. For this reason, in the inner region IN, which has a large contribution when driving straight, the rigidity of the land portion 20 in the circumferential direction of the tire is ensured, and the driving force can be increased to improve the motion performance when driving straight. In addition, although the sum of the widths of the main grooves 10 is relatively small in the outer region OUT, drainage performance can be ensured by promoting drainage in the tire width direction due to voids other than see-through voids.

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

[0037] [Inner area] The shoulder ridge 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 groove 11, which serves as the main groove 10, and are closed within the ridge 20. The shoulder ridge 21 is not divided by the lug grooves 31 and is provided as a rib that extends continuously in the tire circumferential direction. Sipes 41 extending outward in the tire width direction from the closed end of the lug groove 31 and sipes 41 extending outward in the tire width direction from the shoulder main groove 11 are alternately arranged in the tire circumferential direction, and all reach the contact edge CE. The sipes 41 are curved in a direction that is convex 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 groove 11 and are closed within the land portion 20. The center land portion 22 is not divided by the lug grooves 33 and is provided as a rib that extends continuously in the tire circumferential direction. Relatively short lug grooves 32 and relatively long lug grooves 32 are alternately arranged in the tire circumferential direction within the center land portion 22. The lug grooves 32 are smoothly continuous with the lug grooves 31 via the shoulder main groove 11. Smooth continuity of two lug grooves 30 via the main groove 10 refers to a configuration in which an imaginary line extending the length direction of the center width of one groove and an imaginary line extending the length direction of the center width of the other groove overlap within the main groove 10, or are close enough that the distance between them in the tire circumferential direction is 2.0 mm or less. The sipe 42 extends inward in the tire width direction from the closed end of the lug groove 32 and is closed within the land portion 20.

[0039] In this embodiment, the center groove 12c of the groove width 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 previously described, the contact length during straight-line driving tends to be larger 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 such a configuration, it is preferable that the number of main grooves 10 provided in the tread portion 3 be an odd number (for example, 3 or 5). In this example, each of the pair of groove edges in the center main groove 12 is located in the inner region IN, and no main grooves 10 are provided on the tire equator TE.

[0040] [Outer area] The center ridge 23 includes sipes 43 and shallow grooves 50. The center ridge 23 does not include lug grooves and is provided as a rib that extends continuously in the circumferential direction of the tire. The sipes 43 extend inward in the tire width direction from the shoulder main groove 13, which is the main groove 10, and are closed within the ridge 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 that extends along the circumferential direction of the tire and a second portion 52 that extends 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 ridge 20.

[0041] The shoulder land portion 24 includes lug grooves 33, sipes 44, and narrow grooves 60. The lug grooves 33 are formed to taper outward in the tire width direction from the main shoulder groove 13. The lug grooves 33 are closed within the land portion 20, and their depth decreases towards the closed end (see Figure 4). This suppresses the decrease in rigidity near the contact end CE, thereby improving the handling performance during cornering. The shoulder land portion 24 is not divided by the lug grooves 33, but is provided as a rib that extends continuously in the tire circumferential direction. Sipes 44 extending outward in the tire width direction from the vicinity of the lug grooves 33 and sipes 44 extending outward in the tire width direction from the vicinity of the narrow grooves 60 are alternately arranged in the tire circumferential direction, and both reach the contact end 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 turns, the outer region OUT of the tire tends to deform significantly. In tires T with a relatively large width in the outer region OUT of the tire, the deformation of the tire OUT can easily lead to localized concentration of ground pressure, raising concerns about a decrease in handling performance. Therefore, in this embodiment, a narrow groove 60 is provided in the outer region OUT that extends continuously along the circumferential direction of the tire and is narrower in width than the main groove 10. By dividing the tire OUT (shoulder OUT) with the narrow groove 60 and narrowing its width, localized concentration of ground pressure due to deformation during high-load turns is suppressed (ground pressure is distributed), which can contribute to improving handling performance during turns.

[0043] In this embodiment, the narrow groove 60 is provided in the shoulder land portion 24, but not in the inner region IN. In the center land portion 23, which is narrower than the shoulder land portion 24, the first portion 51 of the shallow groove 50 is provided instead of the narrow groove 60. By dividing the area with such a shallow groove 50 (first portion 51) and narrowing the width, it is possible to suppress the reduction in rigidity of the land portion 20 (shoulder land portion 23) while suppressing the localized concentration of ground pressure due to deformation during high-load turning (ground pressure is dispersed), thereby contributing to improved maneuverability during turning.

[0044] In this embodiment, the sipe 44 provided on the shoulder land portion 24 of the outer region OUT is a two-dimensional sipe. As a result, it does not include cavities in the sipe wall surface or bending in the depth direction as in a three-dimensional sipe, and no starting point is formed for the land portion to collapse when it comes into contact with the road surface, thus suppressing a decrease in the rigidity of the sipe edge. On the other hand, the sipe 41 provided on the shoulder land portion 21 of the inner region IN is a three-dimensional sipe, and as a result, the collapse of the shoulder land portion 21 in the tire circumferential direction in the inner region IN, which has a large contribution when driving straight, is suppressed, which can contribute to improving the motion performance when driving straight. Here, a two-dimensional sipe is a sipe in which the inner wall surface has a linear shape in a cross section perpendicular to the length direction of the sipe. A three-dimensional sipe is a sipe in which the inner wall surface has a non-linear shape (for example, a bent shape or a curved shape) in a cross section perpendicular to the length direction of the sipe.

[0045] In the outer region OUT, a lug groove 33 is provided in the shoulder land portion 24, which is the land portion including the contact end CE, extending in a direction intersecting both the tire circumferential direction and the tire width direction. Figure 4(A) is an enlarged view showing the periphery of the lug groove 33. Figures 4(B) and (C) are cross-sectional views of the lug groove 33 along the directions of 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 with respect to the normal direction ND of the surface of the land portion 20 (shoulder land portion 24) is smaller than the angle of the groove wall 33c with respect to the normal direction ND, and the lug groove 33 has an asymmetrical cross-sectional shape with respect to the center of its groove width.

[0046] In this embodiment, the lug groove 33 has a groove wall 33b that extends along the normal direction ND. As described above, the angle of the groove wall 33b with respect to the normal direction ND is smaller than that of the groove wall 33c, which reduces the decrease in the groove width of the lug groove 33 as wear progresses. Therefore, the improvement effect of the lug groove 33 on turning performance, which will be described later, is suppressed as wear progresses.

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

[0048] As shown in Figure 1, in this embodiment, the end 5e of the belt 5 is located outside the lug groove 33 in the tire width direction. In the area where the belt 5 is located, the rigidity is higher than in the area where it is not located, and deformation of the ground portion 20 is suppressed. Therefore, this configuration promotes the uniformity of the contact pressure in the tire width direction of the shoulder ground portion 24 provided with the lug groove 33, which can contribute to improving the maneuverability during cornering.

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

[0050] The tire of this embodiment is equivalent to a normal pneumatic tire, except that it satisfies the relationship (WGi / WLi)>(WGo / WLo), has the widest main groove located in the outer region, and satisfies the relationship θs>θc. Conventional known materials, shapes, and structures can all be used. In the above 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 embodiment.

[0051] Those skilled in the art will understand that the embodiments described above are specific examples of the following embodiments.

[0052] [1] The tire of this disclosure has a specified mounting direction for a vehicle and comprises a tread portion including a main groove extending continuously along the circumferential direction of the tire and a land portion partitioned by the main groove, with a belt including a belt cord embedded in the tread portion. The area from the contact end on the vehicle side of the tread portion to the tire equator is called the inner region, and the area from the contact end on the vehicle side of the tread portion to the tire equator is called the outer region. The ratio of the sum of the widths of the main grooves WGi to the sum of the widths of the land portion WLi in the inner region (WGi / WLi) is greater than the ratio of the sum of the widths of the main grooves WGo to the sum of the widths of the land portion WLo in the outer region (WGo / WLo), and the outer region is provided with the main groove with the largest width among the main grooves included in the tread portion. When the area outside the center of the groove width of the shoulder main groove, which is the outermost of the main grooves in the tire width direction, is called the shoulder region, and the area inside the center of the groove width 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 greater than the inclination angle θc of the belt cord with respect to the tire circumferential direction in the center region.

[0053] Because the ratio (WGi / WLi) is greater than the ratio (WGo / WLo), drainage performance can be ensured by promoting drainage through the main grooves in the inner region where the contact length tends to be larger. Furthermore, in the outer region, where the contribution during turning is greater, the collapse of the ground portion when lateral forces are applied is suppressed, thereby improving turning performance. Moreover, since the widest main groove is located in the outer region, the decrease in drainage performance is suppressed in the outer region where the sum of the widths of the main grooves is relatively small. In addition, because the inclination angle θs is greater than the inclination angle θc, the ground portion of the shoulder is more likely to make contact, improving turning performance. Therefore, this tire can improve turning performance while ensuring drainage performance.

[0054] [2] In the tire described in [1] above, the difference between the inclination angle θs and the inclination angle θc (θs-θc) may be 1 degree or more, from the viewpoint of ensuring an improvement in the motion performance during cornering.

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

[0056] [4] In any one of the above [1] to [3] tires, 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 the inner region. With this configuration, better drainage performance can be ensured in the inner region, where the contact length during straight-line driving tends to be larger.

[0057] [5] In any one of the above [1] to [4] tires, the outer region may be provided with a narrow groove that extends continuously along the circumferential direction of the tire and is narrower in width than the main groove. By dividing the land area with the narrow groove and narrowing its width, localized concentration of ground pressure due to deformation during high-load turning is suppressed (ground pressure is distributed), which can contribute to improving turning performance.

[0058] [6] In any one of the above [1] to [5] tires, the outer region may have a lug groove extending in a direction intersecting both the tire circumferential direction and the tire width direction on the land portion including the contact end, and the lug groove may have a groove wall inclined with respect to the direction normal to the surface of the land portion. With such a configuration, localized lift deformation of the land portion surface when a lateral force is applied can be suppressed, which can contribute to improving the maneuverability during cornering.

[0059] [7] In the tire T described in [6] above, a belt embedded in the tread portion may be provided, wherein the end of the belt is located outside the lug groove in the tire width direction. With such a configuration, the uniformity of the contact pressure in the tire width direction on the land portion where the lug groove is provided can be promoted, which can contribute to improving the handling performance during cornering.

[0060] While embodiments of this disclosure have been described with reference to the drawings, it should be understood that the specific configurations are not limited to these embodiments. The scope of this disclosure is defined not only by the above-described embodiments but also by the claims, and further includes all modifications within the meaning and scope equivalent to the claims.

[0061] The tire of this disclosure is not limited in any way to the embodiments described above, nor is it limited to the effects and advantages described above. The tire of this disclosure can be modified in various ways without departing from its gist. Furthermore, the various components adopted in the embodiments described above can be arbitrarily combined and adopted. [Explanation of Symbols]

[0062] 3 Tread section, 5 Belt, 5C Belt cord, 5e Belt end, 10 Main groove, 20 Land section, 30 Lug groove, 40 Sipe, 50 Shallow groove, 60 Narrow groove, Ce Center area, IN Inner area, OUT Outer area, Sh Shoulder area, T Tire, TE Tire equator

Claims

1. The mounting direction on the vehicle is specified. The tire comprises a tread section including a main groove that extends continuously along the circumferential direction of the tire and a land section partitioned by the main groove, and a belt including a belt cord is embedded in the tread section. When the area from the contact edge on the vehicle side of the tread portion to the tire equator is called the inner region, and the area from the contact edge on the vehicle side of the tread portion to the tire equator is called the outer region, The ratio of the sum of the widths of the main grooves WGi to the sum of the widths of the land portion WLi in the inner region (WGi / WLi) is greater than the ratio of the sum of the widths of the main grooves WGo to the sum of the widths of the land portion WLo in the outer region (WGo / WLo), and the outer region is provided with the main groove that has the widest width among the main grooves included in the tread portion. When the area outside the center of the groove width of the shoulder main groove, which is the outermost of the main grooves in the tire width direction, is called the shoulder region, and the area inside the center of the shoulder main groove in the tire width direction is called the center region, A tire in which the angle of inclination θs of the belt cord in the shoulder region with respect to the tire circumferential direction is greater than the angle of inclination θc of the belt cord in the center region with respect to the tire circumferential direction.

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

3. 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 the inner region.

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

6. In the outer region, the land portion including the contact end is provided with lug grooves extending in directions that intersect both the tire circumferential direction and the tire width direction. The tire according to any one of claims 1 to 5, wherein the lug groove has groove walls inclined with respect to the direction normal to the surface of the land portion.

7. The tread portion is equipped with a belt embedded in it, The tire according to claim 6, wherein the end of the belt is located outward in the tire width direction from the lug groove.

Images