Tire

Abstract

To provide a tire for improving on-snow braking performance, on-snow driving performance, on-snow straight advancing performance and on-snow stability performance in a well-balanced manner.SOLUTION: In a buttress portion (B) from a ground contact end (E1, E2) to an outermost end of a tread rubber in a tire lateral direction for each of shoulder land portions defined and formed on an outermost side in the tire lateral direction by a plurality of inclined grooves (14, 16), a first recessed portion (C1) extending from a stepping-in side to a kick-out side from an inner side toward an outer side in the tire lateral direction is provided, and a second recessed portion (C2) extending from the kick-out side to the stepping-in side from the inner side toward the outer side in the tire lateral direction and divided by the first recessed portion is provided.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a tire with improved on-snow performance. [Background technology]

[0002] Conventionally, a tire has been known in which a convex portion is formed at the outer end of the shoulder block in the tire width direction, with the aim of increasing the rigidity of the auxiliary rib, achieving snow removal performance in the lateral grooves, and ensuring the amount of vertical deflection of the side portion, and this convex portion is composed of a sawtooth-shaped first convex portion and two parallelogram-shaped second convex portions formed along each tooth portion (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-043310 Summary of the Invention [Problem to be solved by the invention]

[0004] In the tire disclosed in Patent Document 1, multiple narrow grooves are formed, with the edges of the convex portions as boundaries, extending in the tire width direction and bending at acute angles to one side in the tire circumferential direction at the outermost positions in the tire width direction. However, the rigidity of the land portion near the bending points of the narrow grooves is insufficient, and there is a risk that excellent braking performance and driving performance on snow will not be achieved.

[0005] Furthermore, in recent years, in addition to braking performance and traction performance on snow, high levels of straight-line running performance and stability on snow are also required. However, the tire disclosed in Patent Document 1 has concerns about the rigidity of the land portions as described above, and therefore there is room for improvement in straight-line running performance and stability on snow.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a tire that has improved at least braking performance and traction performance on snow. [Means for solving the problem]

[0007] The tire of the present invention is characterized in that, for each shoulder land portion defined and formed at the outermost side in the tire width direction by a plurality of inclined grooves, a first recess is provided in the buttress portion from the ground contact edge to the outermost end of the tread rubber in the tire width direction, extending from the inner side to the outer side in the tire width direction from the leading edge to the trailing edge, and a second recess is provided that extends from the inner side to the outer side in the tire width direction from the trailing edge to the leading edge and is separated by the first recess. [Effects of the Invention]

[0008] In the tire according to the present invention, the buttress portion is provided with a first recessed portion extending from the leading edge to the trailing edge from the inner side to the outer side in the tire width direction, and a second recessed portion extending from the leading edge to the trailing edge from the inner side to the outer side in the tire width direction and separated by the first recessed portion. As a result, the first recessed portion and the second recessed portion, which extend in different directions, are not connected, and sufficient rigidity is ensured in the land portion even in the vicinity where these recessed portions approach each other, thereby achieving excellent braking performance on snow, driving performance on snow, etc. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a plan view showing the tread surface of a tire according to this embodiment. [Figure 2] FIG. 2 is a plan view showing a part of the tread surface shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] In the following description, the tire radial direction refers to the direction perpendicular to the tire's rotational axis, the tire radially inner side refers to the side toward the rotational axis in the tire radial direction, and the tire radially outer side refers to the side away from the rotational axis in the tire radial direction. The tire circumferential direction refers to the direction around the rotational axis as the central axis. The tire width direction refers to the direction parallel to the rotational axis, the tire widthwise inner side refers to the side toward the tire equatorial plane (tire equator line) in the tire width direction, and the tire widthwise outer side refers to the side away from the tire equatorial plane in the tire width direction. The tire equatorial plane is a plane that is perpendicular to the tire's rotational axis and passes through the center of the tire width.

[0011] Similarly, in the following description, a regular rim refers to an "applicable rim" as defined by JATMA, a "design rim" as defined by TRA, or a "measuring rim" as defined by ETRTO.

[0012] Similarly, in the following explanation, "normal internal pressure" refers to the "maximum air pressure" specified by JATMA, the maximum value specified in "Tire Load Limits at Various Cold Inflation Pressures" specified by TRA, or the "Inflation Pressures" specified by ETRTO. Also, "normal load" refers to the "maximum load capacity" specified by JATMA, the maximum value specified in "Tire Load Limits at Various Cold Inflation Pressures" specified by TRA, or the "Load Capacity" specified by ETRTO.

[0013] FIG. 1 is a plan view showing the tread surface of a tire of this embodiment, showing the tire mounted on a regular rim and in a no-load state (non-contact state) with regular internal pressure applied. The tread portion of the tire 10 shown in the figure is made of rubber (tread rubber). The surface of the tread portion (tread surface 12) located at the outermost part in the tire radial direction comes into contact with the road surface when the vehicle is running. As shown in FIG. 1, a predetermined tread pattern is formed on part of the tread surface. Note that the upper side of the tire surface 12 shown in FIG. 1 is the trailing edge in the tire rotation direction, and this tread pattern is formed continuously around the entire circumference of the tire.

[0014] In the example shown in Figure 1, inclined grooves 14a to 14e and 16a to 16f (lug grooves) are formed on the tread surface 12, extending from the outside to the inside in the tire width direction from the trailing side to the leading side in the tire circumferential direction (from the top to the bottom in the figure), and convex upward in the figure.

[0015] On one side mounted on a vehicle (the right side in FIG. 1), first inclined grooves 14a, 14c, 14e extending from the tire widthwise outer end beyond the tire equatorial plane CP and second inclined grooves 14b, 14d extending from the tire widthwise outer end to approximately the tire equatorial plane CP are alternately formed in the tire circumferential direction. Similarly, on the other side mounted on a vehicle (the left side in FIG. 1), third inclined grooves 16a, 16c, 16e extending from the tire widthwise outer end to approximately the tire equatorial plane CP and fourth inclined grooves 16b, 16d, 16f extending from the tire widthwise outer end beyond the tire equatorial plane CP are alternately formed in the tire circumferential direction.

[0016] A first inclined groove (e.g., inclined groove 14c) formed on one vehicle mounting side (right side in FIG. 1) communicates with four inclined grooves 16a to 16d formed on the other vehicle mounting side (left side in FIG. 1) and crosses three of these inclined grooves: 16a, 16b, and 16d. On the other hand, a second inclined groove (e.g., inclined groove 14b) formed on one vehicle mounting side (right side in FIG. 1) communicates with two inclined grooves 16b and 16d formed on the other vehicle mounting side (left side in FIG. 1) and crosses one of these inclined grooves: 16d.

[0017] Similarly, a third inclined groove (e.g., inclined groove 16c) formed on the other vehicle mounting side (left side in FIG. 1) communicates with two inclined grooves 14c, 14e formed on one vehicle mounting side (right side in FIG. 1) and crosses one of these inclined grooves, 14e. On the other hand, a fourth inclined groove (e.g., inclined groove 16d) formed on the other vehicle mounting side (left side in FIG. 1) communicates with four inclined grooves 14b, 14c, 14d, and 14e formed on one vehicle mounting side (right side in FIG. 1) and crosses three of these inclined grooves, 14b, 14c, and 14e.

[0018] On one side mounted on the vehicle (the right side in FIG. 1), a plurality of small inclined grooves 18 are formed at a constant pitch in the tire circumferential direction. The small inclined grooves 18 communicate with the three adjacent inclined grooves 14b, 14c, and 14d in the tire circumferential direction and cross the first inclined groove 14c. Similarly, on the other side mounted on the vehicle (the left side in FIG. 1), a plurality of small inclined grooves 20 are formed at a constant pitch in the tire circumferential direction. The small inclined grooves 18 communicate with the three adjacent inclined grooves 16a, 16b, and 16c in the tire circumferential direction and cross the fourth inclined groove 16b.

[0019] A plurality of sipes 22 are formed in the plurality of blocks defined by the inclined grooves 14a to 14e, the inclined grooves 16a to 16f, and the inclined small grooves 18, 20, and are arranged substantially parallel to the inclined grooves 14, 16 that define the blocks. At least one end of the sipes 22 communicates with the inclined grooves 14, 16 or the inclined small grooves 18, 20. The other end of the sipes 22 includes sipes 22a that communicate with the inclined grooves 14, 16 or the inclined small grooves 18, 20, and sipes 22b that terminate within the blocks, and a plurality of these two types of sipes 22a, 22b are formed at a constant pitch in the circumferential direction of the tire.

[0020] At the outermost end in the width direction of the tire on each side where the tire is mounted on the vehicle, a plurality of decorative grooves 24 are formed at a constant pitch in the tire circumferential direction, and are divided into inclined grooves 14 (16).

[0021] Under these assumptions, in the example shown in Figure 1, for each shoulder land portion defined and formed at the outermost side in the tire width direction by a plurality of inclined grooves 14, 16 and inclined small grooves 18, 20, a first recess C1 is provided in the buttress portion B from the ground contact edge E (E1, E2) to the outermost end of the tread rubber in the tire width direction, extending from the inside to the outside in the tire width direction from the leading edge to the trailing edge, and a second recess C2 is provided that extends from the inside to the outside in the tire width direction from the trailing edge to the leading edge and is separated by the first recess C1.

[0022] FIG. 2 is a plan view showing a part of the tread surface shown in FIG. 1, more specifically, a plan view showing the area surrounded by a dotted line in the shoulder land portion on one side of the tire mounted on the vehicle (the right side of FIG. 1).

[0023] 2, in the outer portion (buttress portion B) of the contact edge E1 in the tire width direction, the first recessed portion C1 is composed of a single portion extending from the leading edge to the trailing edge from the inner side toward the outer side in the tire width direction. In contrast, the second recessed portion C2 is composed of two portions divided by the first recessed portion C1, namely, an inner portion C21 in the tire width direction (first portion C21) and an outer portion C22 in the tire width direction (second portion C22), and both of these portions C21 and C22 extend from the inner side toward the outer side in the tire width direction from the trailing edge to the leading edge.

[0024] Normally, when two recesses extending in different directions intersect (or simply communicate with) each other, the rigidity of the land portion sandwiched between the two grooves tends to be low, particularly near the intersection (or communication point), and particularly when the angle between these two recesses is small, the rigidity is likely to be low. However, in this embodiment, as shown in Figure 2, the first recess C1 and the second recess C2 extending in different directions do not intersect (or communicate with each other), and a decrease in the rigidity of the land portion is suppressed even near the point where these recesses C1 and C2 approach each other (effect 1).

[0025] In general, the tire width direction component of the land edge that forms the boundary with the recessed portion contributes to braking and driving action due to the edge effect, and also contributes to snow plowing. In contrast, the tire circumferential direction component of the land edge that forms the boundary with the recessed portion coincides with the tire rotation direction, and therefore contributes to snow removal. In this embodiment, as shown in FIG. 1, both of the two recessed portions C1 and C2 are provided inclined with respect to both the tire width direction and the tire circumferential direction. Therefore, the land edge that forms the boundary with the first recessed portion C1 and the land edge that forms the boundary with the second recessed portion C2 both have both a tire width direction component and a tire circumferential component, and thus contribute to braking action, driving action, snow plowing, and snow removal (Action 2).

[0026] As a result, with the tire of this embodiment, the above-mentioned actions 1 and 2 are combined to achieve at least excellent braking performance on snow (based on the braking action) and excellent driving performance on snow (based on the driving action, the snow shoveling action, and the snow removal action).

[0027] The tire of the present embodiment described above has a meridian cross-sectional shape similar to that of a conventional tire, although not shown. Here, the meridian cross-sectional shape of the tire refers to the cross-sectional shape of the tire that appears on a plane perpendicular to the tire equatorial plane. The tire of the present embodiment has, from the inner side to the outer side in the tire radial direction, a bead portion, a sidewall portion, and a tread portion in the tire meridian cross-sectional view. The tire further includes, for example, a carcass that extends from the tread portion to both bead portions and is wound around a pair of bead cores in the tire meridian cross-sectional view, and a belt layer and a belt reinforcing layer that are sequentially formed on the outer side in the tire radial direction of the carcass.

[0028] The tire of this embodiment is obtained through each of the usual manufacturing steps, i.e., a tire material mixing step, a tire material processing step, a green tire molding step, a vulcanization step, and a post-vulcanization inspection step, etc. When manufacturing the tire of this embodiment, in particular, recesses and protrusions corresponding to the desired tread pattern are formed on the inner wall of a vulcanization mold, and vulcanization is carried out using this mold.

[0029] In the example shown in Figures 1 and 2, it is preferable that the center line of the extension direction of the first recess C1 forms an angle of 25° or more and 60° or less with respect to the tire circumferential direction, and that the center line of the extension direction of the second recess C2 forms an angle of 60° or more and 90° or less with respect to the center line of the extension direction of the first recess C1.

[0030] Here, the extension direction center line of the first recessed portion C1 refers to a straight line connecting the innermost point (first point) of the first recessed portion C1 in the tire width direction and the outermost point (second point) of the first recessed portion C1 in the tire width direction. If there are multiple candidates for the first point, the midpoint of the line connecting the two most distant candidates among the candidates for the first point is taken as the first point. The same applies when there are multiple second points. For example, in the example shown in FIG. 2, there are multiple candidates for the first point and multiple candidates for the second point in the tire circumferential direction. Therefore, in the example shown in FIG. 2, the first point P1 is located at the innermost point of the first recessed portion C1 in the tire width direction and is taken as the midpoint of a line segment extending in the tire circumferential direction, and the second point P2 is located at the outermost point of the first recessed portion C1 in the tire width direction and is taken as the midpoint of a line segment extending in the tire circumferential direction.

[0031] In contrast, the extension direction center line of the second recessed portion C2 refers to a straight line connecting the innermost point (third point) of the second recessed portion C2 in the tire width direction and the outermost point (fourth point) of the second recessed portion C2 in the tire width direction. Because the second recessed portion C2 is made up of two portions C21 and C22, the third point is the innermost point of the first portion C21 in the tire width direction, and the fourth point is the outermost point of the second portion C22 in the tire width direction. Note that if there are multiple candidates for the third point, the midpoint of the line connecting the two candidates that are farthest apart among the candidates for the third point is determined as the third point. The same applies when there are multiple fourth points. For example, in the example shown in FIG. 2, there are multiple candidates for the third point and multiple candidates for the fourth point in the tire circumferential direction. Therefore, in the example shown in Figure 2, the third point P3 is located at the innermost side in the tire width direction of the first part C21 of the second recess C2 and is the midpoint of a line segment extending in the tire circumferential direction, and the fourth point P4 is located at the outermost side in the tire width direction of the second part C22 of the second recess C2 and is the midpoint of a line segment extending in the tire circumferential direction.

[0032] By making the center line of the first recessed portion C1 in the extension direction form an angle of 25° to 60° with respect to the tire circumferential direction, the land edge portion forming the boundary with the first recessed portion C1 can have a balanced tire width direction component and tire circumferential direction component as a whole. As a result, the first recessed portion C1 can achieve an even higher level of compatibility between the driving action, braking action, and snow plowing action resulting from the edge effect based on the tire width direction component of the land edge portion and the snow removal action based on the tire circumferential direction component of the land edge portion.

[0033] On the other hand, by making the center line of the extension direction of the second recess C2 form an angle of 60° to 90° with respect to the center line of the extension direction of the first recess C1, the rigidity of the land portion sandwiched between the first recess C1 and the second recess C2 can be further increased, particularly at the location where the recesses C1 and C2 are close to each other, without excessively reducing the rigidity of the land portion. Note that the angle formed by the center line of the extension direction of the first recess C1 and the center line of the extension direction of the second recess C2 is measured at a location within a range of 90° or less, and is not measured at a location where the angle exceeds 90°.

[0034] In this way, by suitably specifying the extension direction of the center line of the extension direction of the first recess C1 and the extension direction of the center line of the extension direction of the second recess C2, it is possible to achieve even higher levels of driving action, braking action, snow plowing action, and snow removal action, and further increase the rigidity of the land portion sandwiched between the recesses C1 and C2, thereby more efficiently improving braking performance and driving performance on snow.

[0035] Furthermore, to achieve excellent straight-line driving performance of a vehicle on snowy roads, snow plowing and snow removal are important, and higher rigidity of the land portions is also necessary. As described above, by suitably defining the center lines of the extension directions of the recesses C1 and C2, it is possible to achieve both snow plowing and snow removal at an even higher level, and further increase the rigidity of the land portions sandwiched between the recesses C1 and C2. Therefore, by suitably defining the center lines of the extension directions of the recesses C1 and C2, it is possible to achieve excellent straight-line driving performance on snow, etc.

[0036] It is more preferable that the center line of the first recessed portion C1 forms an angle of 27° to 58° with respect to the tire circumferential direction, and it is extremely preferable that the center line of the second recessed portion C2 forms an angle of 62° to 88° with respect to the center line of the first recessed portion C1, and it is extremely preferable that the center line of the second recessed portion C2 forms an angle of 65° to 85° with respect to the center line of the first recessed portion C1.

[0037] In the example shown in FIG. 1 or 2, the maximum depth of the first recess C1 is preferably greater than the maximum depth of the second recess C2 by 0.5 mm or more and 3.0 mm or less.

[0038] Considering the tire shape, when snow (water) moves from the leading edge to the trailing edge near the tire surface during normal tire rolling, it is preferable for the snow (water) to move from the inner side to the outer side in the tire width direction in order to achieve efficient snow removal (drainage). Based on this perspective, more efficient snow removal (drainage) can be achieved by making the maximum depth of the first recessed portion C1 formed from the inner side to the outer side in the tire width direction from the leading edge to the trailing edge 0.5 mm or more deeper than the maximum depth of the second recessed portion C2 (C21, C22) formed from the outer side to the inner side in the tire width direction from the leading edge to the trailing edge. Here, the depth of the recessed portion refers to the recessed portion dimension (maximum value) measured in the tire radial direction from the profile line in the case where the recessed portion does not exist.

[0039] However, if the maximum depth of the first recessed portion C1 is made deeper than the maximum depth of the second recessed portion C2 (C21, C22) by more than 3.0 mm, the rigidity of the land portion around the first recessed portion C1 will be excessively reduced, making it impossible to obtain excellent land portion rigidity. For this reason, the difference between the maximum depth of the first recessed portion C1 and the maximum depth of the second recessed portion C2 (C21, C22) is set to 3.0 mm or less.

[0040] The maximum depth of the first recess C1 is more preferably 0.7 mm to 2.8 mm deeper than the maximum depth of the second recess C2, and most preferably 1.0 mm to 2.5 mm deeper.

[0041] 1 or 2, the first recessed portion C1 and the second recessed portion C2 both gradually narrow toward the tire radially inward, and the groove width of each of the first recessed portion C1 and the second recessed portion C2 is preferably 2 mm or more and 4 mm or less. Here, the groove width means the groove (recessed portion) dimension (maximum value) measured in a direction perpendicular to the direction in which the groove (recessed portion) extends (the same applies to other grooves hereinafter).

[0042] Since both the first recess C1 and the second recess C2 gradually become narrower toward the inside in the tire radial direction, snow that has entered the recesses C1 and C2 can be more reliably discharged to the outside, thereby further improving driving performance on snow.

[0043] Furthermore, since the groove widths of the first recess C1 and the second recess C2 are both 2 mm or more, a larger amount of snow can be secured to enter each of the first recess C1 and the second recess C2, thereby further improving driving performance on snow based on the snow-clearing action.

[0044] On the other hand, since the groove widths of the first recess C1 and the second recess C2 are both 4 mm or less, the rigidity of the land portion sandwiched between the first recess C1 and the second recess C2 (particularly the land portion where the recesses C1 and C2 are close to each other) can be further increased, thereby further improving braking performance and driving performance on snow.

[0045] In this way, by gradually reducing the groove width of the recesses C1 and C2 as they move radially inward of the tire, and by suitably defining the groove widths of the recesses C1 and C2 themselves, it is possible to achieve even higher levels of driving action, braking action, snow plowing action, and snow removal action, and further increase the rigidity of the land portion sandwiched between the recesses C1 and C2, thereby more efficiently improving braking performance and driving performance on snow.

[0046] The groove width of each of the first recess C1 and the second recess C2 is more preferably 2.2 mm or more and 3.8 mm or less, and most preferably 2.5 mm or more and 3.5 mm or less.

[0047] In this embodiment, the first recessed portion C1 and the second recessed portion C2 are provided on at least either side of the vehicle mounting, and the areas of the first recessed portion C1 and the second recessed portion C2 are preferably 10% to 20% of the total area of ​​the buttress portion B. Here, the ratio of the areas of the recessed portions C1 and C2 to the total area of ​​the buttress portion B is calculated for each side of the vehicle mounting.

[0048] 1, the first recessed portion C1 and the second recessed portion C2 are formed on both vehicle mounting sides, but this embodiment is not limited to this configuration and also includes a configuration in which these recessed portions C1, C2 are provided only in the buttress portion B on one vehicle mounting side. However, when considering the tire 10 as a whole, the effects described below are greater when the recessed portions C1, C2 are provided in the buttress portion B on both vehicle mounting sides than when they are provided in the buttress portion B on one vehicle mounting side.

[0049] By making the area of ​​the first recess C1 and the second recess C2 10% or more of the total area of ​​the buttress portion B (on the vehicle mounting side or sides where these recesses C1, C2 are provided), the driving action, braking action, snow plowing action and snow removal action can be further improved, and ultimately the braking performance and driving performance on snow can be further improved.

[0050] In contrast to this, by making the area of ​​the first recess C1 and the second recess C2 20% or less of the total area of ​​the buttress portion B (on the vehicle mounting side or sides on which these recesses C1, C2 are provided), it is possible to achieve better ride comfort performance without excessively reducing the rigidity of the buttress portion B.

[0051] The area of ​​the first recess C1 and the second recess C2 is more preferably 11% to 19% of the total area of ​​the buttress portion B (on the vehicle mounting side or side on which these recesses C1, C2 are provided), and is extremely preferably 12% to 18%.

[0052] In the example shown in FIGS. 1 and 2, the first recess C1 preferably has a tapered tip on the stepping side.

[0053] 1 and 2, the leading edge is the bottom side of the paper, and the leading edge of the first recess C1 is the part that first comes into contact with snow (or water) when the tire rolls. By tapering this part, the snow-digging effect when the tire rolls can be increased, and as a result, straight-line running on snow can be further improved.

[0054] As long as the leading edge of the first recess C1 is tapered, any shape can achieve the above effect. For example, the leading edge of the first recess C1 can be semicircular or semi-elliptical, but a pointed shape as shown in Figure 2 is advantageous in that it can achieve a high level of snow digging ability.

[0055] In the example shown in FIGS. 1 and 2, the second recess C2 preferably has a tapered shape at the leading end on the trailing edge side.

[0056] 2, the leading edge of the first portion C21 is the upper end of the paper, and the leading edge of the first portion C21 is the portion that last discharges snow (or water) when the tire rolls. By tapering this portion, it is possible to increase the snow release effect when the tire rolls, and ultimately to further improve stability on snow.

[0057] As long as the tip of the trailing edge of the second recess C2 is tapered, any shape can achieve the above effect. For example, the tip of the trailing edge of the first portion C22 of the second recess C2 can be semicircular or semi-elliptical, but a pointed shape as shown in Figure 2 is advantageous in that it can achieve a high level of snow-releasing action. [Example]

[0058] Test tires (comparative tire and invention examples 1 to 7) were manufactured with a tire size of 205 / 55R16 (specified by JATMA), a common tread pattern shown in Fig. 1 except for the first recessed portion C1 and the second recessed portion C2, and satisfying the conditions shown in Table 1. Note that the terms in Table 1 all correspond to the terms explained in this embodiment.

[0059] Next, each test tire was mounted on a 16x6.5J rim, and both the front and rear tires were inflated to 250kPa. The tires were then mounted on a 1500cc 2WD vehicle. All test tires were evaluated for braking performance on snow, traction performance on snow, straight-line running performance on snow, and stability on snow according to the following procedures.

[0060] (Method for evaluating braking performance on snow) Using a vehicle equipped with each test tire, ABS braking was performed on a test course consisting of a snowy road at a speed of 20 km / h under load conditions equivalent to two occupants, and the braking distance was measured and the reciprocal of the measured value was calculated. Based on the calculation results, an index evaluation was performed with the comparative example as the standard (100). The evaluation results are also shown in Table 1. In this evaluation, the higher the index, the better the braking performance on snow.

[0061] (Method for evaluating snow driving performance) Using a vehicle equipped with each test tire, the vehicle was driven on a snowy test course under a load equivalent to two occupants at a speed of 5 km / h, and the time required to increase the speed from 5 km / h to 20 km / h was measured five times, and the reciprocal of the average value was calculated. Based on these calculation results, an index was then evaluated, with the comparative example being assigned a standard value of 100. The evaluation results are also shown in Table 1. The higher the index, the better the snow driving performance.

[0062] (Method for evaluating straight-line performance on snow) A test driver conducted a sensory evaluation of each test tire mounted on a vehicle, driving it at a speed of 40 km / h on a snow-covered test course with a load equivalent to two occupants. Based on the results, the tires were then rated on an index, with the conventional tire being set as the standard (100). The evaluation results are also shown in Table 1. The higher the index, the better the straight-line performance on snow.

[0063] (Method for evaluating stability on snow) A test driver conducted a sensory evaluation of each test tire mounted on a vehicle, driving at a speed of 40 km / h on a snow-covered test course with a load equivalent to two occupants. Based on the results, the tires were then rated on an index, with the conventional tire being set as the standard (100). The evaluation results are also shown in Table 1. The higher the index, the better the stability on snow.

[0064] [Table 1]

[0065] According to Table 1, it can be seen that the tires of Invention Examples 1 to 7, which fall within the technical scope of the present invention (i.e., which have the first recess C1 and the second recess C2 shown in Figure 1), all have improved at least snow braking performance and snow driving performance compared to the comparative example tires which do not fall within the technical scope of the present invention. [Explanation of symbols]

[0066] 10 Tires 12 Tread surface 14, 14a, 14b, 14c, 14d, 14e, 16, 16a, 16b, 16c, 16d, 16e, 16f Inclined groove (lug groove) 18, 20 Slanted small groove 22, 22a, 22b sipes 24 Decorative groove B Buttress section C1 First recess C2 Second recess C21: inner portion of second recess in tire width direction C22 Outer portion of the second recess in the tire width direction CP tire equatorial plane E, E1, E2 ground end P1 First point P2 Second point P3 Third Point P4 Fourth point

Claims

1. A tire characterized in that, for each shoulder land portion defined and formed at the outermost side in the tire width direction by a plurality of inclined grooves, a buttress portion from the ground contact edge to the outermost end of the tread rubber in the tire width direction is provided with a first recess extending from the inner side to the outer side in the tire width direction, from the leading edge to the trailing edge, and a second recess extending from the inner side to the outer side in the tire width direction, from the trailing edge to the leading edge, and separated by the first recess.

2. 2. The tire according to claim 1, wherein a center line in an extension direction of the first recessed portion forms an angle of 25° or more and 60° or less with respect to the tire circumferential direction, and a center line in an extension direction of the second recessed portion forms an angle of 60° or more and 90° or less with respect to the center line in the extension direction of the first recessed portion.

3. The tire according to claim 1 or 2, wherein a maximum depth of the first recess is greater than a maximum depth of the second recess by a range of 0.5 mm to 3.0 mm.

4. 3. The tire according to claim 1, wherein the first recess and the second recess both gradually become narrower toward the inside in the tire radial direction, and the first recess and the second recess both have groove widths of 2 mm or more and 4 mm or less.

5. 3. The tire according to claim 1, wherein the first recess and the second recess are provided on at least either side of a vehicle mounting surface, and the areas of the first recess and the second recess are 10% to 20% of a total area of ​​the buttress portion.

6. The tire according to claim 1 or 2, wherein the first recessed portion has a tapered tip on a leading edge side.

7. The tire according to claim 1 or 2, wherein the second recessed portion has a tapered tip on a trailing edge side.

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