Tire

Abstract

The present invention provides a tire capable of improving nail pull-out resistance without deteriorating road surface damage. In a tire in which a tread portion (1) has a hole (13) into which a stud (20) is inserted, a flat portion (14) that coincides with the contour line (L) of the tread portion (1) and is connected in an annular shape is present around the hole (13), and an annular region (A) that is 4-8 mm away from the center (O) of the hole (13) is defined around the flat portion (14). A convex portion (15) which is more convex than the flat portion (14) and a concave portion (16) which is more concave than the flat portion (14) are mixed in the annular region (A).

Description

Technical Field

[0001] The present invention relates to a tire having holes in a tread portion for inserting anti-skid nails, and more particularly to a tire capable of improving nail pull-out resistance without deteriorating road surface damage resistance. Background Art

[0002] The studded tire has a plurality of holes in the tread portion for inserting studs, and is used with studs inserted into the respective holes (see, for example, Patent Documents 1 to 4).

[0003] Studded tires constructed in this way are among the best in terms of performance on ice, and naturally, their excellent performance on ice is brought about by the studs. On the other hand, in order to improve the road damage resistance required by law, the studs are becoming smaller every year, and there is a risk that the resistance to nail pullout will deteriorate compared to the past. The resistance to nail pullout is related to the product life and can be said to be one of the most important issues for studded tires at present.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent No. 5406921

[0007] Patent Document 2: Japanese Patent No. 6099668

[0008] Patent Document 3: Japanese Patent No. 6565574

[0009] Patent Document 4: Japanese Patent No. 4488099 Summary of the invention

[0010] Problems to be solved by the invention

[0011] An object of the present invention is to provide a tire capable of improving nail pullout resistance without deteriorating road surface damage resistance.

[0012] Technical means of solving problems

[0013] The tire of the present invention for achieving the above-mentioned purpose has a hole for inserting anti-skid nails in the tread portion, and is characterized in that there is a flat portion around the hole that is consistent with the contour line of the tread portion and connected in a ring shape, and when an annular area with a distance of 4mm to 8mm from the center of the hole is specified around the flat portion, a convex portion that is more raised than the flat portion and a concave portion that is more recessed than the flat portion are mixed in the annular area.

[0014] Effects of the Invention

[0015] In the present invention, in a tire having a hole for inserting a stud in the tread portion, the stud can be stably held because a flat portion that is consistent with the contour line of the tread portion and connected in an annular shape exists around the hole. On this basis, when an annular region with a distance of 4 mm to 8 mm from the center of the hole is defined around the flat portion, a convex portion that is more raised than the flat portion and a concave portion that is more depressed than the flat portion are mixed in the annular region. Therefore, when the stud is tilted, the force applied in the tilting direction is dispersed based on the presence of the concave portion, thereby preventing the stud from falling off. At this time, if the rigidity is extremely reduced due to the presence of the concave portion, the stud will become easy to tilt, which may deteriorate the resistance to nail pullout, but by having the convex portion and the concave portion exist together in the annular region, the rigidity can be compensated. Therefore, by having the convex portion and the concave portion exist simultaneously in the annular region, the resistance to nail pullout can be effectively improved. In addition, the structure that disperses the force when the anti-skid nail is tilted in the above manner can reduce the force of the anti-skid nail attacking the road surface when running on a dry road, thereby also having the effect of improving the road surface damage. Therefore, according to the present invention, the nail pull-out resistance can be improved without deteriorating the road surface damage.

[0016] In the present invention, the recessed portion is arranged on a concentric circle with the hole as the center, and the recessed portion preferably has a discontinuous shape in a part of the circumferential direction of the concentric circle. If the recessed portion is continuous in the circumferential direction of the concentric circle with the hole as the center, the anti-slip nail will be easily tilted due to insufficient rigidity, which is disadvantageous from the viewpoint of nail pull-out resistance. However, by making the recessed portion have a discontinuous shape in a part of the circumferential direction of the concentric circle, the rigidity around the anti-slip nail can be ensured, and the anti-slip nail can be prevented from falling off.

[0017] The recessed portion is preferably arranged at a position that does not overlap with a circumferential line that passes through the center of the hole and is parallel to the tire circumferential direction. Thus, excessive tilting of the anti-skid studs is suppressed during rapid acceleration and rapid deceleration, thereby effectively preventing the anti-skid studs from falling off.

[0018] The recessed portion is preferably arranged at a position that does not overlap with a width direction line that passes through the center of the hole and is orthogonal to the tire circumferential direction. Thus, excessive tilting of the anti-skid stud is suppressed during sharp turns, thereby effectively preventing the anti-skid stud from falling off.

[0019] When the inner annular region having a distance of 4 mm to 6 mm from the center of the hole and the outer annular region having a distance of 6 mm to 8 mm from the center of the hole are defined in the annular region, the area of ​​the recessed portion included in the inner annular region is preferably larger than the area of ​​the recessed portion included in the outer annular region. Thus, the force generated when a strong force acts on the anti-slip nail is effectively dispersed, thereby enhancing the effect of improving the nail pull-out resistance.

[0020] The recesses are preferably arranged on a plurality of concentric circles centered on the hole. Thus, when the anti-skid nail is tilted, the force applied in the tilted direction can be effectively dispersed to prevent the anti-skid nail from falling off. In this case, the recesses on the plurality of concentric circles can be arranged so as to overlap with each other in the radial direction of the concentric circles. Thus, when the anti-skid nail is tilted, the force applied in the tilted direction can be effectively dispersed to prevent the anti-skid nail from falling off, and on the other hand, the improvement effect of road surface damage is increased. Alternatively, the recesses on the plurality of concentric circles can be arranged so as not to overlap with each other in the radial direction of the concentric circles. Thus, when the anti-skid nail is tilted, the force applied in the tilted direction can be effectively dispersed, and the rigidity can be ensured to prevent the anti-skid nail from tilting excessively, thereby increasing the improvement effect of nail pull-out resistance.

[0021] In a plan view of the tread portion, when the main body of the anti-skid nail inserted into the hole has a length direction, when an inner annular region having a distance of 4 mm to 6 mm from the center of the hole and an outer annular region having a distance of 6 mm to 8 mm from the center of the hole are defined in the annular region, the recessed portion is preferably arranged at a position in the inner annular region that does not overlap with a virtual line passing through the center of the hole and parallel to the length direction of the main body. If the distance between the main body of the anti-skid nail and the recessed portion is too close, the nail pullout resistance may be deteriorated due to insufficient rigidity, but by arranging the recessed portion in the inner annular region that does not overlap with a virtual line passing through the center of the hole and parallel to the length direction of the main body, the nail pullout resistance can be effectively improved.

[0022] Preferably, the depth Hy of the recessed portion satisfies the relationship of 0.05Hs≤Hy≤0.25Hs relative to the height Hs of the stud, and the height Hx of the protrusion satisfies the relationship of 0.10Hy≤Hx≤0.80Hy relative to the depth Hy of the recessed portion. This can effectively improve the nail pull-out resistance.

[0023] The tire of the present invention is preferably a pneumatic tire, but may also be a non-pneumatic tire. When it is a pneumatic tire, its interior may be filled with inert gas such as air, nitrogen or other gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a meridian cross-sectional view showing a pneumatic tire according to an embodiment of the present invention.

[0025] Figure 2 Yes means Figure 1 A cross-sectional view of a stud mounting portion in a tread portion of a pneumatic tire.

[0026] Figure 3 Yes means Figure 1 A top view of a stud mounting portion in a tread portion of a pneumatic tire.

[0027] Figure 4 It is a perspective view showing an example of a cleat.

[0028] Figure 5 Yes means Figure 4 A top view of the cleats.

[0029] Figure 6 Yes means Figure 4 Side view of a cleat.

[0030] Figure 7 Yes means Figure 4 A cross-sectional view showing a state where a skid nail is inserted into a hole of a tread portion.

[0031] Figure 8 (a) to (c) are plan views respectively showing improved examples of the stud mounting portion.

[0032] Fig. 9 (a) to (d) are plan views respectively showing other improved examples of the stud mounting portion.

[0033] Fig.10 It is a top view showing still another improved example of the stud mounting portion.

[0034] Fig.11 (a) to (e) are top views respectively showing still another improved example of the stud mounting portion.

[0035] Fig.12 It is a top view showing still another improved example of the stud mounting portion. DETAILED DESCRIPTION

[0036] Hereinafter, the configuration of the present invention will be described in detail with reference to the drawings. Figure 1 A pneumatic tire according to an embodiment of the present invention is shown. Figure 2 and Figure 3 Indicates the part of the tread where the cleats are installed. Figures 4 to 6 represents an example of a cleat, Figure 7 Indicates a state where the studs are inserted into the holes in the tread portion.

[0037] like Figure 1 As shown, the pneumatic tire of this embodiment includes a tread portion 1 extending in the tire circumferential direction and formed in an annular shape, a pair of sidewall portions 2, 2 arranged on both sides of the tread portion 1, and a pair of bead portions 3, 3 arranged on the inner side of these sidewall portions 2 in the tire radial direction.

[0038] A carcass layer 4 is provided between a pair of bead portions 3, 3. The carcass layer 4 includes a plurality of reinforcing cords extending in the radial direction of the tire and is folded back from the inner side to the outer side of the tire around a bead core 5 disposed at each bead portion 3. A bead core 6 made of a rubber composition and having a triangular cross section is disposed on the outer periphery of the bead core 5.

[0039] On the other hand, a plurality of belt layers 7 are buried on the outer peripheral side of the carcass layer 4 in the tread portion 1. These belt layers 7 include a plurality of reinforcing cords inclined relative to the circumferential direction of the tire, and the reinforcing cords are arranged in a mutually crossed manner between the layers. In the belt layer 7, the inclination angle of the reinforcing cords relative to the circumferential direction of the tire is set, for example, in the range of 10° to 40°. As the reinforcing cords of the belt layer 7, steel cords are preferably used. In order to improve high-speed durability, at least one belt cover layer 8 is arranged on the outer peripheral side of the belt layer 7, in which the reinforcing cords are arranged at an angle of, for example, less than 5° relative to the circumferential direction of the tire. As the reinforcing cords of the belt cover layer 8, organic fiber cords such as nylon and aramid are preferably used.

[0040] It should be noted that the above tire internal structure shows a representative example of a pneumatic tire, but is not limited thereto. In addition, the tread pattern formed on the tread portion 1 is also not particularly limited.

[0041] In the pneumatic tire, a circumferential groove 11 extending in the tire circumferential direction is formed in the tread portion 1, and a plurality of rows of land portions 12 are divided by the circumferential grooves 11. The land portions 12 are divided into a plurality of pattern blocks by, for example, transverse grooves (not shown) extending in the tire width direction. A plurality of holes 13 for inserting anti-skid studs 20 are formed in the land portions 12 of the tread portion 1. Figures 4 to 6 As shown, the anti-skid spike 20 is composed of a columnar main body 21, a tip portion 22 provided at the front end side of the main body 21, and a flange portion 23 provided at the base end side of the main body 21. The tip portion 22 is made of a material with a higher hardness than the main body 21. The outer diameter of the flange portion 23 is larger than the outer diameter of the main body 21. The anti-skid spike 20 is provided on the tread portion 1 in such a manner that the main body 21 and the flange portion 23 are inserted into the hole 13 and the tip portion 21 protrudes from the outline L of the tread portion 1 (see Figure 7 Since the inner diameter of the hole 13 is slightly smaller than the outer diameter of the main body 21 of the anti-skid stud 20, the anti-skid stud 20 inserted into the hole 13 is firmly held on the tread portion 1.

[0042] As such, in a tire having a tread portion 1 with holes 13 for inserting anti-skid studs 20, Figure 2 and Figure 3 As shown, there is a flat portion 14 around the hole 13, which has a height consistent with the contour line L of the tread portion 1 and is connected in an annular shape. The contour line L of the tread portion 1 refers to the arc that forms the contour of the tread portion 1 in the tire meridian section. Figure 2 and Figure 3In the figure, for design reasons, there is a portion slightly shallower than the outline L around the hole 13, but this portion is not essential.

[0043] exist Figure 3 In the figure, a virtual circle C1 whose distance X1 from the center O of the hole 13 is 4 mm, a virtual circle C2 whose distance X2 from the center O of the hole 13 is 6 mm, and a virtual circle C3 whose distance X3 from the center O of the hole 13 is 8 mm are depicted. Among them, an annular area A whose distance from the center O of the hole 13 is 4 to 8 mm is defined around the flat portion 14. The annular area A is an area sandwiched by the virtual circle C1 and the virtual circle C3. The annular area A is composed of an inner annular area Ai whose distance from the center O of the hole 13 is 4 to 6 mm, and an outer annular area Ao whose distance from the center O of the hole 13 is 6 to 8 mm. At this time, a plurality of convex portions 15 which are more raised toward the outer side in the radial direction of the tire than the flat portion 14 and a plurality of concave portions 16 which are more depressed toward the inner side in the radial direction of the tire than the flat portion 14 are formed in the annular area A, and these convex portions 15 and concave portions 16 are mixed in the annular area A. Figure 3 In the following drawings, the recessed portion 16 is indicated with oblique lines for easier understanding.

[0044] As described above, in a tire in which the tread portion 1 has the hole 13 for inserting the anti-skid stud 20, since there is a flat portion 14 around the hole 13 that is consistent with the contour line L of the tread portion 1 and connected in an annular shape, Figure 7 As shown in FIG. 1 , the stud 20 can be stably held in a state where the stud 20 is inserted into the hole 13 of the tread portion 1. Furthermore, when an annular region A is defined around the flat portion 14 at a distance of 4 to 8 mm from the center O of the hole 13, the convex portion 15 that is more raised than the flat portion 14 and the concave portion 16 that is more depressed than the flat portion 14 coexist in the annular region A. Therefore, when the stud 20 is tilted, the force applied in the tilting direction is dispersed due to the presence of the concave portion 16, thereby preventing the stud 20 from falling off. At this time, if the rigidity is extremely reduced due to the presence of the concave portion 16, the stud 20 will become easy to tilt, and the nail pull-out resistance may be deteriorated. However, by having the convex portion 15 and the concave portion 16 in the annular region A, the rigidity can be compensated. Therefore, by having the convex portion 15 and the concave portion 16 in the annular region A, the nail pull-out resistance can be effectively improved. In addition, the structure that disperses the force when the anti-skid stud 20 is tilted in this way can reduce the force of the anti-skid stud 20 attacking the road surface when driving on a dry road, thereby also having the effect of improving the road surface damage.

[0045] In order to optimize the buffering effect of the recess 16, the maximum width of the recess 16 measured in the radial direction from the center O of the hole 13 is 0.5 mm or more and less than 2 mm. In addition, in order to optimize the nail pull-out resistance, it is preferred that the area ratio of the recess 16 to the annular region A is 10% to 50%, the area ratio of the convex portion 15 to the annular region A is 10% to 90%, and the area ratio of the convex portion 15 and the recess 16 to the annular region A is less than 90%.

[0046] In the pneumatic tire, Figure 3 As shown, the recess 16 is arranged on a concentric circle P1 centered on the hole 13, and the recess 16 has a discontinuous shape in a part of the circumference of the concentric circle P1. Figure 3 In the embodiment, a plurality of convex portions 15 and a plurality of concave portions 16 are alternately arranged at intervals on the concentric circle P1. In addition, a plurality of convex portions 15 are arranged at intervals on the concentric circle P2 set outside the concentric circle P1 with the hole 13 as the center. If the concave portions 16 are continuous in the circumferential direction of the concentric circle P1 with the hole 13 as the center, the stud 20 will be easily tilted due to insufficient rigidity, which is disadvantageous from the viewpoint of resistance to nail pull-out. However, by making the concave portions 16 have a discontinuous shape in a part of the circumferential direction of the concentric circle P1, the rigidity around the stud 20 can be ensured, and the stud 20 can be prevented from falling off.

[0047] Figure 8 (a) to (c) of FIG. 1 respectively represent examples of improvements in the anti-slip stud installation portion. Figure 8 In (a), the convex portion 15 is arranged on the concentric circle P2 and has a shape that is continuous in the circumferential direction of the concentric circle P2, and the concave portion 16 is arranged on the concentric circle P1 and has a shape that is continuous in the circumferential direction of the concentric circle P1. Figure 8 In (b), the convex portion 15 is arranged on the concentric circle P2 and has a shape that is continuous in the circumferential direction of the concentric circle P2, and the concave portion 16 is arranged on the concentric circle P1 and has a shape that is discontinuous in a part of the circumferential direction of the concentric circle P1. Figure 8 In (c), the convex portion 15 is arranged on the concentric circle P2 and has a shape that is continuous in the circumferential direction of the concentric circle P2, and the concave portion 16 is arranged on the concentric circle P1 and has a circular shape in a top view. As described above, the shapes and arrangements of the convex portion 15 and the concave portion 16 can be changed according to the required performance and design.

[0048] Fig. 9 (a) to (d) respectively represent other improved examples of the anti-slip stud installation part. Figure 1 In the embodiment of the present invention, the convex portion 15 and the concave portion 16 are symmetrically arranged on the concentric circles P1 and P2. Fig. 9In (a) to (c), the convex portion 15 and the concave portion 16 are asymmetrically arranged on the concentric circle P1. Fig. 9 In (d), a part of the convex portion 15 is in a linear shape.

[0049] Fig.10 2 shows another improved example of the anti-slip stud installation part. Fig.10 In the embodiment, the recess 16 is arranged at a position that does not overlap with a circumferential line Lc that passes through the center O of the hole 13 and is parallel to the tire circumferential direction. In this case, the anti-skid stud 20 is suppressed from being excessively tilted during rapid acceleration and deceleration, thereby effectively preventing the anti-skid stud 20 from falling off.

[0050] In addition, Fig.10 In the embodiment, the recess 16 is arranged at a position that does not overlap with a width direction line Lw that passes through the center O of the hole 13 and is orthogonal to the tire circumferential direction. In this case, the stud 20 is restrained from tilting excessively during sharp turns, thereby effectively preventing the stud 20 from falling off.

[0051] exist Figure 3 In the annular region A, an inner annular region Ai whose distance from the center O of the hole 13 is 4 mm to 6 mm and an outer annular region Ao whose distance from the center O of the hole 13 is 6 mm to 8 mm are defined. The inner annular region Ai is a region sandwiched by the virtual circle C1 and the virtual circle C2, and the outer annular region Ao is a region sandwiched by the virtual circle C2 and the virtual circle C3. At this time, the area of ​​the recess 16 included in the inner annular region Ai is set larger than the area of ​​the recess 16 included in the outer annular region Ao. In this way, by arranging a relatively large number of recesses 16 in the inner annular region Ai, the force generated when a strong force acts on the anti-slip nail 20 can be effectively dispersed, thereby improving the effect of improving the nail pull-out resistance.

[0052] Fig.11 (a) to (e) of FIG. 1 respectively represent another improved example of the anti-slip stud installation portion. Fig.11 In (a) to (e), the recess 16 is arranged on two of the plurality of concentric circles P1 to P3 centered on the hole 13. Fig.11 In (a), the concave portion 16 continuous along the concentric circles P1 and P2 is arranged on the concentric circles P1 and P2, the convex portion 15 continuous along the concentric circle P3 is arranged on the concentric circle P3, and the portion between the concave portions 16 and 16 arranged on the concentric circles P1 and P2 becomes the height of the contour line L. Fig.11 In (b), the concave portion 16 that is continuous along the concentric circles P1 and P3 is arranged on the concentric circles P1 and P3, and the convex portion 15 that is continuous along the concentric circle P2 is arranged on the concentric circle P2. Fig.11In (c) and (d), the concave portion 16 having a discontinuous shape on a part of the circumference of the concentric circles P1 and P2 is arranged on the concentric circles P1 and P2, and the convex portion 15 continuous along the concentric circle P3 is arranged on the concentric circle P3. Fig.11 In (e), the convex parts 15 and the concave parts 16 having a discontinuous shape on a part of the circumferential direction of the concentric circles P1 and P2 are alternately arranged on the concentric circles P1 and P2, respectively, and the convex parts 15 continuous along the concentric circle P3 are arranged on the concentric circle P3. In this way, by arranging the concave parts 16 on a plurality of concentric circles P1 to P3 centered on the hole 13, when the anti-skid stud 20 is tilted, the force applied in the tilting direction can be effectively dispersed, and the anti-skid stud 20 can be prevented from falling off.

[0053] Especially if Fig.11 As shown in (a) and (b) of FIG. 1 , when the recesses 16 located on the plurality of concentric circles P1 to P3 are arranged to overlap each other in the radial direction of the concentric circles P1 to P3, when the anti-skid stud 20 is tilted, the force applied in the tilting direction can be effectively dispersed, and the anti-skid stud 20 can be prevented from falling off, while the effect of improving the road surface damage can be increased. Fig.11 As shown in (c) to (e), when the recesses 16 located on the plurality of concentric circles P1 to P3 are arranged so as not to overlap with each other in the radial direction of the concentric circles P1 to P3, when the anti-slip nail 20 is tilted, the force applied in the tilting direction can be effectively dispersed, and the rigidity can be ensured to prevent the anti-slip nail 20 from being excessively tilted, thereby increasing the improvement effect of the nail pull-out resistance.

[0054] Fig.12 2 shows another improved example of the anti-slip stud installation part. Figure 5 As shown, in the top view of the tread portion 1 (i.e., the top view of the anti-skid stud 20), the main body 21 of the anti-skid stud 20 has a dimension D1 in a first direction and a dimension D2 in a second direction orthogonal to the first direction, the dimension D1 is larger than the dimension D2, and the first direction is the length direction T. As shown in FIG. 1 , in the top view of the tread portion 1, when the main body 21 of the anti-skid stud 20 has the length direction T, as shown in FIG. Fig.12As shown in FIG. 1 , when the inner annular region Ai having a distance of 4 mm to 6 mm from the center O of the hole 13 and the outer annular region Ao having a distance of 6 mm to 8 mm from the center O of the hole 13 are defined in the annular region A, the recess 16 may be arranged at a position in the inner annular region Ai that does not overlap with a virtual line Tx that passes through the center O of the hole 13 and is parallel to the longitudinal direction T of the main body 21. That is, if the distance between the main body 21 of the anti-slip spike 20 and the recess 16 is too close, the nail pull-out resistance may be deteriorated due to insufficient rigidity, but by arranging the recess 16 at a position in the inner annular region Ai that does not overlap with a virtual line Tx that passes through the center O of the hole 13 and is parallel to the longitudinal direction T of the main body 21, the nail pull-out resistance can be effectively improved.

[0055] In the pneumatic tire, the depth Hy of the recessed portion 16 (see Figure 2 ) relative to the height Hs of the anti-slip stud 20 (see Figure 6 ) satisfies the relationship of 0.05Hs≤Hy≤0.25Hs, and the height Hx of the convex portion 15 (see Figure 2 ) The depth Hy of the concave portion 16 satisfies the relationship of 0.10Hy≤Hx≤0.80Hy. In this way, the nail pull-out resistance can be effectively improved. If the depth Hy of the concave portion 16 and the height Hx of the convex portion 15 deviate from the above range, the effect of improving the nail pull-out resistance will be reduced. For example, when the height Hs of the anti-slip stud 20 is 9 mm to 10 mm, the depth Hy of the concave portion 16 can be set to the range of 0.5 mm to 2.0 mm, and the height Hx of the convex portion 15 can be set to the range of 0.2 mm to 1.0 mm.

[0056] Example

[0057] Pneumatic tires of the prior art, comparative examples 1 to 4, and embodiments 1 to 9 were produced. The pneumatic tires had a tire size of 205 / 55R16 and had a hole for inserting a stud in the tread portion, wherein the following items were set as shown in Tables 1 and 2: the presence or absence of a flat portion formed around the hole, the presence or absence of a recess in the annular region, the presence or absence of a convex portion in the annular region, the presence or absence of a discontinuity in the recess, the presence or absence of a recess overlapping a circumferential line passing through the center of the hole, the presence or absence of a recess overlapping a width direction line passing through the center of the hole, the area of ​​the recess included in the inner annular region, the area of ​​the recess included in the outer annular region, the area ratio of the recess to the annular region, the area ratio of the convex portion to the annular region, the number of arrangements of recesses overlapping in the radial direction of the concentric circle, and the presence or absence of a recess overlapping a virtual line passing through the center of the hole and parallel to the length direction of the main body of the stud in the inner annular region. The stud was inserted into the hole in such a manner that the length direction of the main body was oriented in the tire width direction.

[0058] The nail pull-out resistance and road surface damage resistance of these test tires were evaluated by the following test methods. The results are shown in Tables 1 and 2.

[0059] Nail Pullout Resistance:

[0060] Each test tire was assembled on a wheel with a rim size of 16×6.5J and installed on a front-wheel drive vehicle with a displacement of 1.4L. A specified air pressure was applied to the vehicle as air pressure. After driving 20,000 km in a specified urban driving mode on an outdoor test track consisting of an asphalt road surface, the number of nail pullouts was measured. The evaluation results were expressed as an index using the reciprocal of the measured value, with the previous example set to 100. The larger the index value, the better the nail pullout resistance.

[0061] Road damage:

[0062] Each test tire was assembled on a wheel with a rim size of 16×6.5J and installed on a front-wheel drive vehicle with a displacement of 1.4L. The air pressure was set to 250kPa. After driving 200 times at a speed of 100km / h on a granite plate set on the road surface, the road wear amount was measured based on the weight difference of the plate before and after the test. The evaluation results were expressed as an index with the previous example set to 100 using the reciprocal of the measured value. The larger the index value, the smaller the road wear amount, which means that the road damage is better.

[0063] [Table 1]

[0064]

[0065] [Table 2]

[0066]

[0067]

[0068] As can be seen from Tables 1 and 2, the tires of Examples 1 to 9 have improved road surface damage resistance and nail pullout resistance compared to the previous examples. On the other hand, in the tires of Comparative Examples 1 and 2, although there are recesses in the annular region, there are no protrusions in the annular region, so the nail pullout resistance is deteriorated due to insufficient rigidity. In the tire of Comparative Example 3, although there are protrusions in the annular region, there are no recesses in the annular region, so the improvement effect of nail pullout resistance is not obtained. In the tire of Comparative Example 4, since there is no flat portion around the hole, the nail pullout resistance is deteriorated.

[0069] Description of Reference Numerals

[0070] 1: Tread

[0071] 2: Side wall

[0072] 3: Bead

[0073] 4: Carcass layer

[0074] 5: Bead core

[0075] 6: Bead core

[0076] 7: Belt

[0077] 8: With cover layer

[0078] 11 Circumferential groove

[0079] 12: Shoreline

[0080] 13: Hole

[0081] 14: Flat part

[0082] 15: convex part

[0083] 16: concave part

[0084] 20: Anti-slip spikes

[0085] 21: Main body

[0086] 22: Tip

[0087] 23: Flange

Claims

1. A tire having holes in the tread for inserting anti-skid nails, characterized in that: There is a flat portion around the hole that is consistent with the contour line of the tread portion and connected in a ring shape, and an annular area with a distance of 4mm to 8mm from the center of the hole is specified around the flat portion, and in the annular area, there are a mixture of convex portions that are more raised than the flat portion and concave portions that are more recessed than the flat portion.

2. The tire according to claim 1, characterized in that The recessed portion is arranged on a concentric circle centered on the hole, and the recessed portion has a discontinuous shape in a portion of the circumference of the concentric circle.

3. The tire according to claim 2, characterized in that The recessed portion is arranged at a position that does not overlap with a circumferential line that passes through the center of the hole and is parallel to the tire circumferential direction.

4. The tire according to claim 2, characterized in that The recessed portion is arranged at a position that does not overlap with a width direction line that passes through the center of the hole and is orthogonal to the tire circumferential direction.

5. The tire according to any one of claims 1 to 4, characterized in that When an inner annular region whose distance from the center of the hole is 4 mm to 6 mm and an outer annular region whose distance from the center of the hole is 6 mm to 8 mm are defined in the annular region, the area of ​​the recess contained in the inner annular region is larger than the area of ​​the recess contained in the outer annular region.

6. The tire according to any one of claims 1 to 5, characterized in that The recessed portions are respectively arranged on a plurality of concentric circles centered on the hole.

7. The tire according to claim 6, characterized in that The recessed portions located on the plurality of concentric circles are arranged so as to overlap with each other in radial directions of the concentric circles.

8. The tire according to claim 6, characterized in that The recessed portions located on the plurality of concentric circles are arranged so as not to overlap with each other in radial directions of the concentric circles.

9. The tire according to any one of claims 1 to 8, characterized in that In the top view of the tread portion, the main body of the anti-slip nail inserted into the hole has a length direction, and when an inner annular area with a distance of 4mm to 6mm from the center of the hole and an outer annular area with a distance of 6mm to 8mm from the center of the hole are specified in the annular area, the recess is arranged in a position within the inner annular area that does not overlap with a virtual line passing through the center of the hole and parallel to the length direction of the main body.

10. The tire according to any one of claims 1 to 9, characterized in that The depth Hy of the concave portion satisfies the relationship of 0.05Hs≤Hy≤0.25Hs with respect to the height Hs of the stud, and the height Hx of the convex portion satisfies the relationship of 0.10Hy≤Hx≤0.80Hy with respect to the depth Hy of the concave portion.

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