阅读说明：本技术 充气轮胎 (Pneumatic tire ) 是由 高桥菜摘 于 2020-04-07 设计创作，主要内容包括：为了在抑制驾驶稳定性的降低的同时确保潮湿性能,充气轮胎(1)包括：多个倒角刀槽花纹(41),形成于环岸部(20),且是具有倒角部(42)的刀槽花纹(40)；多个无倒角刀槽花纹(46),形成于环岸部(20),且是不具有倒角部(42)的刀槽花纹(40),倒角刀槽花纹(41)的一端与用于划分环岸部(20)的主槽(30)相连通,另一端终止于环岸部(20)内,倒角刀槽花纹(41)和无倒角刀槽花纹(46)在轮胎周向上交替设置,在位于倒角刀槽花纹(41)的轮胎周向两侧的无倒角刀槽花纹(46)中,作为距倒角刀槽花纹(41)的距离较近的一侧的无倒角刀槽花纹(46)的邻近刀槽花纹(47)与倒角刀槽花纹(41)之间的距离a和在轮胎周向上距倒角刀槽花纹(41)的距离较远的一侧的无倒角刀槽花纹(46)与倒角刀槽花纹(41)的距离b之间的关系在1.5≦(b/a)≦12范围之内。(In order to ensure wet performance while suppressing a decrease in driving stability, a pneumatic tire (1) includes: a plurality of chamfered sipes (41) which are formed in the land portion (20) and are sipes (40) having chamfered portions (42); a plurality of non-chamfered sipes (46) formed in the land portion (20) and being sipes (40) having no chamfered portion (42), one end of the chamfered sipe (41) communicating with the main groove (30) for partitioning the land portion (20) and the other end terminating in the land portion (20), the chamfered sipe (41) and the non-chamfered sipes (46) being alternately arranged in the tire circumferential direction, in the non-chamfered sipes (46) located on both sides of the chamfered sipe (41) in the tire circumferential direction, the relationship between the distance a between the neighboring sipe (47) of the non-chamfered sipe (46) on the side closer to the chamfered sipe (41) and the chamfered sipe (41), and the distance b between the non-chamfered sipe (46) on the side farther from the chamfered sipe (41) in the tire circumferential direction and the chamfered sipe (41) is in the range of 1.5 ≦ (b/a) ≦ 12.)

1. A pneumatic tire, comprising:

a plurality of main grooves extending in the tire circumferential direction;

a land portion whose end in the tire width direction is divided by the main groove;

a plurality of chamfered sipes formed in the land portion and having chamfered portions; and

a plurality of non-chamfered sipes formed in the land portion and having no chamfered portion,

one end of the chamfer sipe is communicated with the main groove for dividing the ring land part, and the other end is terminated in the ring land part,

the chamfered sipes and the non-chamfered sipes are alternately arranged in the tire circumferential direction,

in the chamfer-free sipes located on both sides of the chamfered sipe in the tire circumferential direction, a relationship between a distance a in the tire circumferential direction between a neighboring sipe of the chamfer-free sipe located on a side closer to the chamfered sipe in the tire circumferential direction and the chamfered sipe and a distance b in the tire circumferential direction between the chamfer-free sipe located on a side farther from the chamfered sipe in the tire circumferential direction and the chamfered sipe is in a range of 1.5 ≦ (b/a) ≦ 12.

2. A pneumatic tire according to claim 1,

in the chamfered sipe and the adjacent sipe, a relationship between a length Lm of the chamfered sipe and a length Lp of the adjacent sipe is in a range of 0.2 ≦ (Lm/Lp) ≦ 0.95.

3. A pneumatic tire according to claim 1 or 2,

the chamfered sipe has the chamfered portion on the wall surface on the side closer to the adjacent sipe among the facing wall surfaces the chamfered sipe has.

4. A pneumatic tire according to any one of claims 1 to 3,

in the chamfered sipe and the adjacent sipe, a relationship between an opening width Wm of the chamfered sipe and an opening width Wp of the adjacent sipe is in a range of 1.2 ≦ (Wm/Wp) ≦ 6.0.

5. A pneumatic tire according to any one of claims 1 to 4,

the relationship between the opening width Wm of the chamfered sipe and the groove bottom width Wm1 is in the range of 0.1 ≦ (Wm1/Wm) ≦ 0.85.

6. A pneumatic tire according to any one of claims 1 to 5,

the land portion is divided by the main grooves on both sides in the tire width direction, and the adjacent sipes communicate with the two main grooves for dividing the land portion.

7. The pneumatic tire according to any one of claims 1 to 6, wherein in the chamfered sipe and the adjacent sipe, a relationship between a groove depth Dm of the chamfered sipe and a groove depth Dp of the adjacent sipe is within a range of 1.2 ≦ (Dp/Dm) ≦ 8.0.

8. A pneumatic tire according to any one of claims 1 to 7,

the relationship between the groove depth Dm of the chamfered sipe and the chamfer depth Dm1 is in the range of 0.1 ≦ (Dm1/Dm) ≦ 0.85. A pneumatic tire according to any one of claims 1 to 7,

for the circumferential sipes, the maximum depth D of the circumferential sipes_SCWith respect to the maximum groove depth D of the circumferential main grooveIs tied at a ratio of 0.50 to less than or equal to (D)_SCThe ratio of/D) is less than or equal to 0.80.

9. A pneumatic tire according to any one of claims 1 to 8,

the land portion is divided by the main groove on both sides in the tire width direction, and in the chamfer sipes, a plurality of the chamfer sipes formed on the same land portion communicate with the same main groove.

10. A pneumatic tire according to any one of claims 1 to 9,

of the chamfered sipe and the adjacent sipe, one side of the tire which first contacts the ground in the tire rotation direction is provided with the adjacent sipe.

11. A pneumatic tire according to any one of claims 1 to 10,

in a tire meridian cross-sectional view, the land portion in which the chamfered sipe is formed has a tread surface that protrudes outward in the tire radial direction from a reference profile line of the tread profile.

Technical Field

The present invention relates to a pneumatic tire.

Background

In a pneumatic tire, a plurality of grooves are formed in the surface of a tread portion for the purpose of, for example, drainage between the tread surface and the road surface when the tire is running on a wet road surface. In addition, in the conventional pneumatic tire, a so-called sipe form is designed as a concave portion formed in a tread surface, and thereby, the drainage performance is improved. For example, in the pneumatic tires described in patent documents 1 and 2, the provision of chamfered sipes, which are sipes having chamfered portions, is designed to improve the running performance on wet road surfaces, that is, the wet performance. That is, in patent documents 1 and 2, in two main grooves for partitioning the rim on both sides in the tire width direction, in which the chamfered sipe communicates with one of the main grooves and the chamfered sipe communicates with the other main groove are alternately provided in the tire circumferential direction, so that the wet performance is improved.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2018-111453

Patent document 2: japanese patent No. 6364781

Disclosure of Invention

Problems to be solved by the invention

However, when the chamfered sipes communicating with different main grooves are alternately provided in the tire circumferential direction, there is a possibility that the rigidity of a part of the rim between the chamfered sipes at the initial stage of use of the pneumatic tire is lowered, and the driving stability on a dry road surface at the initial stage of use of the pneumatic tire is easily lowered.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a pneumatic tire capable of ensuring wet performance while suppressing a decrease in driving stability.

Technical scheme

In order to solve the above-described technical problems and achieve the object, a pneumatic tire of the present invention includes: a plurality of main grooves extending in the tire circumferential direction; a land portion whose end in the tire width direction is divided by the main groove; a plurality of chamfered sipes formed in the land portion and having chamfered portions; a plurality of non-chamfered sipes formed in the land portion and having no chamfered portion, one end of the chamfer sipes is communicated with the main groove for dividing the land portion, and the other end is terminated in the land portion, the chamfer sipes and the chamfer-free sipes are alternately arranged in the circumferential direction of the tire, in the chamfer-free sipes located on both sides of the chamfered sipe in the tire circumferential direction, a relationship between a distance a in the tire circumferential direction between a neighboring sipe of the chamfer-free sipe located on a side closer to the chamfered sipe in the tire circumferential direction and the chamfered sipe and a distance b in the tire circumferential direction between the chamfer-free sipe located on a side farther from the chamfered sipe in the tire circumferential direction and the chamfered sipe is in a range of 1.5 ≦ (b/a) ≦ 12.

Further, in the above pneumatic tire, it is preferable that, in the chamfered sipe and the adjacent sipe, a relationship between a length Lm of the chamfered sipe and a length Lp of the adjacent sipe is in a range of 0.2 ≦ (Lm/Lp) ≦ 0.95.

Also, in the pneumatic tire described above, it is preferable that the chamfered sipe has the chamfered portion on the wall surface on the side closer to the adjacent sipe among the facing wall surfaces that the chamfered sipe has.

Also, in the above pneumatic tire, it is preferable that, of the chamfered sipe and the adjacent sipe, a relationship between an opening width Wm of the chamfered sipe and an opening width Wp of the adjacent sipe is in a range of 1.2 ≦ (Wm/Wp) ≦ 6.0.

Further, in the above pneumatic tire, it is preferable that the relationship between the opening width Wm of the chamfered sipe and the groove bottom width Wm1 is in a range of 0.1 ≦ (Wm1/Wm) ≦ 0.85.

Also, in the pneumatic tire described above, it is preferable that the land portion is divided by the main grooves on both sides in the tire width direction, and the adjacent sipes communicate with the two main grooves for dividing the land portion.

Also, in the above pneumatic tire, it is preferable that, in the chamfered sipe and the adjacent sipe, a relationship between a groove depth Dm of the chamfered sipe and a groove depth Dp of the adjacent sipe is in a range of 1.2 ≦ 8.0 (Dp/Dm).

In the pneumatic tire described above, it is preferable that the relationship between the groove depth Dm of the chamfered sipe and the chamfer portion depth Dm1 is in a range of 0.1 ≦ (Dm1/Dm) ≦ 0.85.

Further, in the above pneumatic tire, it is preferable that the land portion is divided by the main grooves on both sides in the tire width direction, and in the chamfer sipes, a plurality of the chamfer sipes formed on the same land portion communicate with the same main groove.

Also, in the pneumatic tire described above, it is preferable that, of the chamfered sipe and the adjacent sipe, the adjacent sipe is provided on the side which first contacts the ground in the tire rotational direction.

In the pneumatic tire described above, it is preferable that the land portion in which the chamfered sipe is formed has a tread surface protruding outward in the tire radial direction from a reference profile line of a tread profile in a tire meridian cross-sectional view.

Effects of the invention

The pneumatic tire according to the present invention has an effect of ensuring wet performance while suppressing a decrease in driving stability.

Drawings

Fig. 1 is a meridian cross-sectional view showing a main portion of a pneumatic tire according to an embodiment.

Fig. 2 is an a-a arrow view of fig. 1.

Fig. 3 is a perspective view of the land portion shown in fig. 2.

Fig. 4 is a sectional view B-B of fig. 2.

Fig. 5 is a detailed view of the portion C of fig. 4.

Fig. 6 is an explanatory view of a modification of the pneumatic tire according to the embodiment, in which a chamfer-free sipe communicates with only one main groove.

Fig. 7 is an explanatory view of a modification of the pneumatic tire according to the embodiment, in which chamfered sipes communicate with different main grooves.

Fig. 8 is an explanatory view of a modification of the pneumatic tire according to the embodiment, in which the land portion is in a block shape.

Fig. 9 is a schematic view of a modification of the pneumatic tire according to the embodiment, and the arrangement of sipes with respect to the rotational direction of the pneumatic tire.

Fig. 10 is a schematic view of a modification of the pneumatic tire according to the embodiment, and is directed to a main portion of the protruding land portion.

Fig. 11A is a graph showing the results of a performance evaluation test of a pneumatic tire.

Fig. 11B is a graph showing the results of a performance evaluation test of a pneumatic tire.

Fig. 11C is a graph showing the results of the performance evaluation test of the pneumatic tire.

Fig. 11D is a graph showing the results of the performance evaluation test of the pneumatic tire.

Detailed Description

Hereinafter, embodiments of the pneumatic tire according to the present invention will be described in detail with reference to the drawings. The present invention is not limited to the embodiment. The components in the embodiments described below include those that can be easily replaced by a person skilled in the art or those that are substantially the same.

[ embodiment ]

In the following description, the tire radial direction refers to a direction orthogonal to a tire rotation axis (not shown) as a rotation axis of the pneumatic tire 1, the tire radial direction inner side refers to a side in the tire radial direction toward the tire rotation axis, and the tire radial direction outer side refers to a side in the tire radial direction away from the tire rotation axis. The tire circumferential direction is a circumferential direction having the tire rotation axis as a central axis. The tire width direction refers to a direction parallel to the tire rotation axis, the tire width direction inner side refers to a side toward the tire equatorial plane (tire equatorial line) CL in the tire width direction, and the tire width direction outer side refers to a side away from the tire equatorial plane CL in the tire width direction. The tire equatorial plane CL refers to a plane that is orthogonal to the tire rotation axis and passes through the center of the tire width of the pneumatic tire 1, and the tire equatorial plane CL has a tire width direction center line that is the center position of the pneumatic tire 1 in the tire width direction and a position in the tire width direction. The tire width is a width in the tire width direction of the portions located outermost in the tire width direction from each other, that is, a distance between the portions farthest from the tire equatorial plane CL in the tire width direction. The tire equator line refers to a line on the tire equatorial plane CL along the tire circumferential direction of the pneumatic tire 1.

Fig. 1 is a meridian cross-sectional view showing a main portion of a pneumatic tire 1 according to the embodiment. In the pneumatic tire 1 according to the present embodiment, the tread portion 2 is disposed at the outermost portion in the tire radial direction when viewed in a cross section of a meridian plane, and the tread portion 2 has the tread rubber layer 4 made of a rubber composition. The surface of the tread portion 2, that is, the portion that comes into contact with the road surface during traveling of a vehicle (not shown) to which the pneumatic tire 1 is attached, is formed as a tread surface 3, and the tread surface 3 forms a part of the contour of the pneumatic tire 1.

The tread portion 2 has a plurality of main grooves 30 formed in the tread surface 3 and extending in the tire circumferential direction, and the plurality of main grooves 30 are aligned in the tire width direction. Further, a plurality of land portions 20 whose tire width direction upper end portions are divided by the main grooves 30 are formed in the tread portion 2. In the present embodiment, 3 main grooves 30 are arranged in the tire width direction, and accordingly, 4 rows of land portions 20 among the land portions 20 are arranged in the tire width direction by the main grooves 30. The land portions 20 of the 4 rows are formed in a rim shape extending in the tire circumferential direction.

The main groove 30 is a vertical groove at least a part of which extends in the tire circumferential direction. The main groove 30 has a groove width of 3.0mm or more, a groove depth of 5.5mm or more, and a tread indicator (non-skid mark) indicating the end stage of wear. The main groove 30 may extend linearly in the tire circumferential direction, or may be formed in a wavy or zigzag shape by extending in the tire circumferential direction and repeatedly swinging in the tire width direction.

The shoulder portion 5 is located at both outer ends of the tread portion 2 in the tire width direction, and a sidewall portion 8 is disposed on the tire radial direction inner side of the shoulder portion 5. That is, the side wall portions 8 are disposed on both sides of the tread portion 2 in the tire width direction. In other words, the side wall portions 8 are disposed at two positions on both sides of the pneumatic tire 1 in the tire width direction, and form portions exposed to the outermost side in the tire width direction on the pneumatic tire 1.

There is a bead portion 10 on the tire radial direction inner side of each sidewall portion 8 located on both sides in the tire width direction. Like the sidewall portion 8, the bead portions 10 are disposed at two positions on both sides of the tire equatorial plane CL, that is, a pair of bead portions 10 are disposed on both sides of the tire equatorial plane CL in the tire width direction. Each bead portion 10 is provided with a bead core 11, and the outer side of the bead core 11 in the tire radial direction is provided with a bead filler 12. The bead core 11 is an annular member formed into an annular shape by binding bead wires as steel wires, and the bead filler 12 is a rubber member provided outside the bead core 11 in the tire radial direction.

Further, a belt layer 14 is disposed in the tread portion 2. The belt layer 14 has a multilayer structure in which a plurality of belts 141 and 142 are stacked, and in the present embodiment, two belts 141 and 142 are stacked. The belts 141 and 142 constituting the belt layer 14 are formed by rolling a plurality of belt cords made of steel or an organic fiber material such as polyester, rayon, or nylon, and the belt angle is defined as an inclination angle of the belt cords in the tire width direction with respect to the tire circumferential direction and falls within a predetermined range (for example, 20 ° or more and 55 ° or less). The belt angles of the two belts 141, 142 are different from each other. Therefore, in the belt layer 14, the two belts 141 and 142 are constructed in a bias structure in which the belt cords are stacked so that the oblique directions thereof intersect with each other. That is, the two belts 141 and 142 are provided as a cross belt in which belt cords included in the respective belts 141 and 142 are arranged in a direction crossing each other. The tread rubber layer 4 having the tread portion 2 is disposed on the outer side in the tire radial direction of the belt layer 14 on the tread portion 2.

A carcass layer 13 including cords of the radial layer is continuously provided on the inner side of the belt layer 14 in the tire radial direction and on the tire equatorial plane CL side of the sidewall 8. Therefore, the pneumatic tire 1 according to the present embodiment is configured as a radial tire. The carcass layer 13 has a single-layer structure formed of 1 carcass ply or a multilayer structure formed by laminating a plurality of carcass plies, and is annularly stretched between a pair of bead portions 10 disposed on both sides in the tire width direction to form a framework of the tire.

Specifically, in the carcass layer 13, one bead portion 10 of the pair of bead portions 10 located on both sides in the tire width direction is arranged through the other bead portion 10, and the bead portion 10 is turned back along the bead core 11 to the outside in the tire width direction to wrap the bead core 11 and the bead filler 12. The bead filler 12 is folded back in the bead portion 10 by the carcass layer 13 in this manner, and constitutes a rubber material disposed in a space formed on the outer side of the bead core 11 in the tire radial direction. Further, the belt layer 14 is provided on the outer side in the tire radial direction of the portion of the carcass layer 13 located in the tread portion 2, which is thus bridged between the pair of bead portions 10. The carcass ply of the carcass layer 13 is formed by covering a plurality of carcass cords made of an organic fiber material such as steel, aramid, nylon, polyester, or rayon with a coating rubber and subjecting the resultant to a rolling process. A plurality of carcass cords constituting the ply are arranged side by side in such a manner that an angle with respect to the tire circumferential direction is along the tire radial direction and has an angle in the tire circumferential direction.

A rim cushion rubber 17 constituting a contact surface of the bead portion 10 with respect to a rim flange is disposed on the inner side in the tire radial direction or the outer side in the tire width direction of the bead core 11 and the turnback portion of the carcass layer 13 in the bead portion 10. Further, an inner liner 16 is formed along the carcass layer 13 on the inner side of the carcass layer 13 or on the inner side of the pneumatic tire 1 of the carcass layer 13. The inner liner 16 forms a tire inner surface 18 as an inner side surface of the pneumatic tire 1.

Fig. 2 is an a-a arrow view of fig. 1. Fig. 3 is a perspective view of the land portion 20 shown in fig. 2. Fig. 2 and 3 show the land portions 20 divided by the main groove 30 on both sides in the tire width direction among the plurality of land portions 20. As shown in fig. 2 and 3, a plurality of sipes 40 are formed in the land portion 20. The sipe 40 described here is a sipe formed in a narrow groove shape in the tread surface 3, and means a sipe in which the width between wall surfaces constituting the narrow groove is less than 2mm and the depth of the narrow groove from the tread surface 3 is 2mm or more in a state before the pneumatic tire 1 is rim-assembled on a rim.

The plurality of sipes 40 include a plurality of chamfered sipes 41 as the sipes 40 having the chamfered portions 42 and a plurality of non-chamfered sipes 46 as the sipes 40 not having the chamfered portions 42. In this case, the chamfered portion 42 is a cut-out portion lacking a part of an edge where the wall surface of the sipe 40 intersects with the tread surface 3, and the chamfered portion 42 may have a rectangular shape, an inclined shape, or the like.

The chamfered sipes 41 and the non-chamfered sipes 46 are provided in plural in one land portion 20, respectively, and the plural chamfered sipes 41 and the non-chamfered sipes 46 are alternately provided in the tire circumferential direction. At this time, the pitch における in the tire circumferential direction of the chamfered sipe 41 is the same as the pitch in the tire circumferential direction of the non-chamfered sipe 46, and the phases of the chamfered sipe 41 and the non-chamfered sipe 46 are arranged to be shifted in the tire circumferential direction.

Wherein one end of the chamfered sipe 41 communicates with the main groove 30 for partitioning the land portion 20, and the other end terminates in the land portion 20. Also, the plurality of chamfered sipes 41 formed on the same land portion 20 communicate with the same main groove 30 of the two main grooves 30 that divide both sides of the land portion 20 in the tire width direction, in the chamfered sipes 41. That is, all of the plurality of chamfered sipes 41 formed in one land portion 20 communicate with the same main groove 30.

On the other hand, both ends in the longitudinal direction of the chamfer-free sipe 46 communicate with both of the two main grooves 30 for defining the land portion 20. In other words, the chamfer-free sipe 46 penetrates the land portion 20 in which the chamfer-free sipe 46 is formed in the tire width direction.

Therefore, in the chamfered sipe 41 and the chamfer-free sipe 46, the relationship between the length Lm of the chamfered sipe 41 and the length Lp of the chamfer-free sipe 46 is Lm < Lp, and specifically, in the range of 0.2 ≦ (Lm/Lp) ≦ 0.95. Further, the lengths Lm, Lp in this case are lengths in the extending direction of the chamfered sipe 41 or the non-chamfered sipe 46, that is, lengths in the direction along the shape of the chamfered sipe 41 or the non-chamfered sipe 46. Also, the relationship between the length Lm of the chamfered sipe 41 and the length Lp of the non-chamfered sipe 46 is preferably in the range of 0.3 ≦ (Lm/Lp) ≦ 0.8, and the length Lm of the chamfered sipe 41 is preferably in the range of 2mm or more and 30mm or less.

The chamfered sipes 41 and the non-chamfered sipes 46 are alternately arranged in the tire circumferential direction, and therefore the non-chamfered sipes 46 are located on both sides of the chamfered sipe 41 in the tire circumferential direction. The chamfered sipes 41 and the non-chamfered sipes 46 are arranged in the tire circumferential direction so as to be offset from each other, and therefore, the distances in the tire circumferential direction between the two non-chamfered sipes 46 and the chamfered sipes 41 located on both sides of the chamfered sipe 41 in the tire circumferential direction are different from each other.

Among the non-chamfered sipes 46 located on both sides of the chamfered sipe 41 in the tire circumferential direction, the non-chamfered sipe 46 on the side closer to the chamfered sipe 41 in the tire circumferential direction becomes the adjacent sipe 47, and the non-chamfered sipe 46 on the side farther from the chamfered sipe 41 in the tire circumferential direction becomes the distal sipe 48, at distances different from each other. The adjacent sipe 47 and the distal sipe 48 are each in communication with two main grooves 30 for dividing the land portion 20 forming the adjacent sipe 47 or the distal sipe 48. Further, since the adjacent sipe 47 is the chamfer-free sipe 46, when the lengths of the chamfered sipe 41 and the adjacent sipe 47 are compared, the relationship between the length Lm of the chamfered sipe 41 and the length Lp of the adjacent sipe 47 is in the range of 0.2 ≦ (Lm/Lp) ≦ 0.95.

Further, for two non-chamfered sipes 46 adjacent by a chamfered sipe 41, the adjacent sipe 47 and the distal sipe 48 are determined based on the distance from the chamfered sipe 41 located therebetween. Therefore, with respect to the chamfered sipe 41 adjacent to the chamfered sipe 41 through the adjacent sipe 47, the adjacent sipe 47 with respect to a certain chamfered sipe 41 is regarded as a distal sipe 48. Similarly, for a chamfered sipe 41 adjacent to the chamfered sipe 41 through the distal sipe 48, the distal sipe 48 with respect to a certain chamfered sipe 41 is considered to be the adjacent sipe 47.

In the chamfered sipe 41, the adjacent sipe 47, and the distal sipe 48 defined as described above, the relationship between the distance a in the tire circumferential direction between the chamfered sipe 41 and the adjacent sipe 47, and the distance b in the tire circumferential direction between the chamfered sipe 41 and the distal sipe 48 is in the range of 1.5 ≦ (b/a) ≦ 12.

Fig. 4 is a sectional view B-B of fig. 2. The distance a between the chamfered sipe 41 and the adjacent sipe 47 becomes the distance a in the tire circumferential direction at a position in the chamfered sipe 41 including the chamfered portion 42 and closest to the adjacent sipe 47. Similarly, the distance b between the chamfered sipe 41 and the distal end sipe 48 becomes the distance b in the tire circumferential direction at the position in the chamfered sipe 41 that includes the chamfered portion 42 and is the closest to the distal end sipe 48.

Among them, in the present embodiment, the chamfered sipe 41 has the chamfered portion 42 in the wall surface 41a on the side closer to the adjacent sipe 47 among the facing wall surfaces 41a having the chamfered sipe 41. Therefore, in the present embodiment, the distance a between the chamfered sipe 41 and the adjacent sipe 47 becomes the shortest distance in the tire circumferential direction between the portion closest to the adjacent sipe 47 in the chamfered portion 42 having the chamfered sipe 41 and the wall surface 47a on the chamfered sipe 41 side in the adjacent sipe 47. Further, the distance b between the chamfered sipe 41 and the distal end sipe 48 becomes the shortest distance in the tire circumferential direction between the wall surface 41a on the distal end sipe 48 side in the chamfered sipe 41 and the wall surface 48a on the chamfered sipe 41 side in the distal end sipe 48.

Preferably, the relationship between the distance a between the chamfered sipe 41 and the adjacent sipe 47, and the distance b between the chamfered sipe 41 and the distal sipe 48, which are defined as described above, is in the range of 1.5 ≦ (b/a) ≦ 5, and more preferably, in the range of 3 ≦ (b/a) ≦ 5. Also, it is preferable that the distance a between the chamfered sipe 41 and the adjacent sipe 47 is within a range of 3mm or more and 6mm or less.

Fig. 5 is a detailed view of the portion C of fig. 4. In the chamfered sipe 41 and the adjacent sipe 47, the relationship between the opening width Wm of the chamfered sipe 41 and the opening width Wp of the adjacent sipe 47 is in the range of 1.2 ≦ (Wm/Wp) ≦ 6.0. The opening width Wm of the chamfered sipe 41 in this case is the width of the opening portion of the chamfered sipe 41 including the chamfered portion 42 with respect to the tread surface 3, and when the width of the opening portion is changed, the opening width Wm is the width at the position of the maximum width. Similarly, the opening width Wp of the adjacent sipe 47 is also the width at the position of the maximum width when the width of the opening portion changes with respect to the width of the opening portion of the adjacent sipe 47 of the tread surface 3.

Further, it is preferable that the relationship between the opening width Wm of the chamfered sipe 41 and the opening width Wp of the adjacent sipe 47 is in the range of 2.0 ≦ (Wm/Wp) ≦ 4.0. Also, it is preferable that the opening width Wm of the chamfered sipe 41 is in the range of 1.0mm or more and 8.0mm or less, and it is preferable that the opening width Wp of the adjacent sipe 47 is in the range of 0.8mm or more and 1.8mm or less.

In the chamfered sipe 41, the relationship between the opening width Wm and the groove bottom width Wm1 is in the range of 0.1 ≦ (Wm1/Wm) ≦ 0.85. The groove bottom width Wm1 of the chamfered sipe 41 in this case is the width at the position where the groove width becomes the maximum at the position of the groove bottom 41b of the chamfered sipe 41. Further, it is preferable that the relationship between the opening width Wm of the chamfered sipe 41 and the groove bottom width Wm1 is in the range of 0.3 ≦ (Wm1/Wm) ≦ 0.6, and the groove bottom width Wm1 of the chamfered sipe 41 is in the range of 0.8mm or more and 1.8mm or less.

Also, in the chamfered sipe 41 and the adjacent sipe 47, the relationship between the groove bottom width Wm1 of the chamfered sipe 41 and the groove bottom width Wp1 of the adjacent sipe 47 is in the range of 0.3 ≦ (Wm1/Wp1) ≦ 3.0. The groove bottom width Wp1 in this case is the width at the position where the groove width is the largest at the position adjacent to the groove bottom 47b of the sipe 47. Further, it is preferable that the relationship between the groove bottom width Wm1 of the chamfered sipe 41 and the groove bottom width Wp1 of the adjacent sipe 47 is in the range of 0.5 ≦ (Wm1/Wp1) ≦ 2.0.

Also, in the chamfered sipe 41 and the adjacent sipe 47, the relationship between the groove depth Dm of the chamfered sipe 41 and the groove depth Dp of the adjacent sipe 47 is in the range of 1.2 ≦ (Dp/Dm) ≦ 8.0. The groove depth Dm of the chamfered sipe 41 or the groove depth Dp of the adjacent sipe 47 in this case is the depth of each sipe 40 from the position where the depth from the opening portion to the groove bottom with respect to the tread surface 3 is the largest.

Further, it is preferable that the relationship between the groove depth Dm of the chamfered sipe 41 and the groove depth Dp of the adjacent sipe 47 is in the range of 1.4 ≦ (Dp/Dm) ≦ 2.0. Also, it is preferable that the groove depth Dm of the chamfered sipe 41 is in the range of 2.0mm or more and 5.0mm or less, and the groove depth Dp of the adjacent sipe 47 is in the range of 2.4mm or more and 6.0mm or less.

In the chamfered sipe 41, the relationship between the groove depth Dm and the chamfered portion depth Dm1 of the chamfered portion 42 is in a range of 0.1 ≦ (Dm1/Dm) ≦ 0.85. The chamfered portion depth Dm1 in this case is the depth at the position where the depth in the depth direction of the chamfered sipe 41 is the largest from the opening portion of the chamfered portion 42 with respect to the tread surface 3 to the end portion on the groove bottom 41b side of the chamfered sipe 41.

Further, in the chamfered sipe 41, the relationship between the groove depth Dm and the chamfer portion depth Dm1 is preferably within a range of 0.3 ≦ (Dm1/Dm) ≦ 0.6, and the chamfer portion depth Dm1 is preferably within a range of 0.6mm or more and 3.0mm or less.

When the pneumatic tire 1 of the present embodiment is mounted on a vehicle, the pneumatic tire 1 is rim-assembled on a rim wheel, filled with air, and mounted on the vehicle in an inflated state. When a vehicle on which the pneumatic tire 1 is mounted travels, the pneumatic tire 1 rotates while the tread surface 3 positioned below the tread surface 3 of the tread portion 2 is in contact with a road surface. When a vehicle using the pneumatic tire 1 is running on a dry road surface, driving force or braking force is transmitted to the road surface mainly by the frictional force between the tread surface 3 and the road surface, or running is performed by generating steering force. When the vehicle travels on a wet road surface, water between the tread surface 3 and the road surface flows into grooves such as the main grooves 30 or the sipes 40, and the vehicle travels while water between the tread surface 3 and the road surface is drained from the main grooves 30 or the sipes 40. This makes it easy for the tread surface 3 to contact the road surface, and the vehicle can travel by the frictional force between the tread surface 3 and the road surface.

At this time, some of the plurality of sipes 40 become chamfered sipes 41, and the chamfered sipes 41 have chamfered portions 42, so that drainage can be ensured by the chamfered portions 42. That is, in the chamfered sipe 41, even in the case where the portion of the tread surface 3 of the land portion 20 where the chamfered sipe 41 is formed, which is located around the chamfered sipe 41, is brought into contact to deform in the direction in which the groove width narrows, the volume of the chamfered sipe 41 is ensured by the chamfered portion 42. Thereby, drainage in the chamfered sipe 41 can be improved. On the other hand, the chamfered sipe 41 has an end portion terminating inside the land portion 20, and therefore, a decrease in rigidity of the land portion 20 in which the chamfered sipe 41 is formed can be suppressed, whereby driving stability during traveling of the vehicle can be ensured.

Further, in the sipe 40, the chamfered sipe 41 and the non-chamfered sipe 46 are alternately provided in the tire circumferential direction, and the sipe 40 on one side of the chamfered sipe 41 in the tire circumferential direction becomes the adjacent sipe 47 relatively close to the chamfered sipe 41. Therefore, when the portion of the tread surface 3 of the land portion 20 located around the chamfered sipe 41 contacts the ground, the land portion 20 around the chamfered sipe 41 can be deformed in the direction in which the groove width of the adjacent sipe 47 becomes narrow, whereby the case in which the chamfered sipe 41 becomes large in the direction in which the groove width of the chamfered sipe 41 becomes narrow can be suppressed. That is, when the portion of the tread surface 3 of the land portion 20 located around the chamfered sipe 41 comes into contact with the ground, the deformation of the land portion 20 on the adjacent sipe 47 can be borne by pressing the adjacent sipe 47, and the pressing of the chamfered sipe 41 can be suppressed. Therefore, even when the portion located around the chamfered sipe 41 comes into contact with the ground, the volume of the chamfered sipe 41 having the chamfered portion 42 can be more reliably ensured, and the drainage property on the chamfered sipe 41 can be ensured.

Further, in the chamfered sipe 41 and the non-chamfered sipe 46, the relationship between the distance a between the chamfered sipe 41 and the adjacent sipe 47 and the distance b between the chamfered sipe 41 and the distal sipe 48 is in the range of 1.5 ≦ (b/a) ≦ 12, and therefore, it is possible to suppress a decrease in rigidity of a part of the land portion 20, and at the same time, suppress squeezing of the chamfered sipe 41 by squeezing the adjacent sipe 47.

That is, when the relationship between the distance a and the distance b is (b/a) <1.5, the distance a between the chamfered sipe 41 and the adjacent sipe 47 is excessively large, and therefore, when the portion of the land portion 20 located around the chamfered sipe 41 comes into contact with the ground, the adjacent sipe 47 is difficult to be pressed, or even if the adjacent sipe 47 is pressed, it is difficult to suppress the pressing of the chamfered sipe 41. That is, the distance a between the chamfered sipe 41 and the adjacent sipe 47 is excessively large, and therefore, it is difficult to make the deformation of the adjacent sipe 47 and the deformation of the chamfered sipe 41 mutually affect each other, and when the portion of the land portion 20 located around the chamfered sipe 41 contacts the ground, it is difficult to suppress the squeezing of the chamfered sipe 41. In this case, when the portion of the land portion 20 located around the chamfered sipe 41 comes into contact with the ground surface, it may be difficult to secure the volume of the chamfered sipe 41, and it may be difficult to secure the wet performance as the running performance on a wet road surface. When the relationship between the distance a and the distance b is (b/a) >12, the distance a between the chamfered sipe 41 and the adjacent sipe 47 is excessively small, and therefore, there is a possibility that the rigidity of a portion between the chamfered sipe 41 and the adjacent sipe 47 in the land portion 20 becomes excessively small. In this case, the rigidity of the land portion 20 is lowered, and thus, it may be difficult to ensure driving stability on a dry road surface mainly when the vehicle is traveling.

In contrast, when the relationship between the distance a and the distance b is in the range of 1.5 ≦ (b/a) ≦ 12, it is possible to suppress the case where the rigidity of the portion between the chamfered sipe 41 and the adjacent sipe 47 in the land portion 20 becomes excessively small, and the deformation of the adjacent sipe 47 and the deformation of the chamfered sipe 41 can be made to affect each other. Thereby, the reduction of the rigid portion of the land portion 20 can be suppressed, and at the same time, the pressing of the chamfered sipe 41 can be suppressed by pressing the adjacent sipe 47 when the portion of the land portion 20 located around the chamfered sipe 41 comes into contact with the ground. As a result, the wet performance can be ensured while suppressing a decrease in driving stability.

Further, in the chamfered sipe 41 and the adjacent sipe 47, the relationship between the length Lm of the chamfered sipe 41 and the length Lp of the adjacent sipe 47 is in the range of 0.2 ≦ (Lm/Lp) ≦ 0.95, and therefore, it is possible to suppress the pressing of the chamfered sipe 41 by pressing the adjacent sipe 47 with an appropriate length while suppressing the vicinity of the adjacent sipe 47 in the land portion 20 from becoming too small in rigidity.

That is, when the relationship between the length Lm of the chamfered sipe 41 and the length Lp of the adjacent sipe 47 is (Lm/Lp) <0.2, the length Lp of the adjacent sipe 47 becomes excessively long, and therefore, the rigidity in the vicinity of the adjacent sipe 47 in the land portion 20 may become excessively small. In this case, since the rigidity of a part of the land portion 20 is reduced, it may be difficult to ensure the driving stability during the vehicle running. Further, when the relationship between the length Lm of the chamfered sipe 41 and the length Lp of the adjacent sipe 47 is (Lm/Lp) >0.95, the length Lp of the adjacent sipe 47 may become excessively short. In this case, when the portion of the land portion 20 located around the chamfered sipe 41 contacts the ground, even if the adjacent sipe 47 is pressed, since the length by which the adjacent sipe 47 is pressed is short, it is difficult to suppress the pressing of the chamfered sipe 41 due to the pressing of the adjacent sipe 47, and therefore, it may be difficult to secure drainage in the chamfered sipe 41.

On the other hand, when the relationship between the length Lm of the chamfered sipe 41 and the length Lp of the adjacent sipe 47 is in the range of 0.2 ≦ (Lm/Lp) ≦ 0.95, the adjacent sipe 47 in the land portion 20 is suppressed from being excessively rigid, and when the portion of the land portion 20 around the chamfered sipe 41 comes into contact with the ground, the adjacent sipe 47 can be pressed by an appropriate length, thereby suppressing the pressing of the chamfered sipe 41. As a result, the wet performance can be ensured more reliably while suppressing a decrease in driving stability.

Further, in the chamfered sipe 41, the chamfered portion 42 is provided in the wall surface 41a on the side closer to the adjacent sipe 47 among the facing wall surfaces 41a having the chamfered sipe 41, and therefore, when the portion of the land portion 20 located around the chamfered sipe 41 comes into contact with the ground surface, the adjacent sipe 47 is pressed, whereby the pressing of the vicinity of the chamfered portion 42 in the chamfered sipe 41 can be further reliably suppressed. Thereby, the volume of the chamfered sipe 41 can be further reliably ensured by the chamfered portion 42, and the drainage property in the chamfered sipe 41 can be improved. As a result, the moisture performance can be further reliably improved.

Further, in the chamfered sipe 41 and the adjacent sipe 47, the relationship between the opening width Wm of the chamfered sipe 41 and the opening width Wp of the adjacent sipe 47 is in the range of 1.2 ≦ (Wm/Wp) ≦ 6.0, and therefore, while the volume of the chamfered sipe 41 is secured, it is possible to suppress the case where the rigidity around the chamfered sipe 41 in the land portion 20 becomes excessively small. That is, in the case where the relationship between the opening width Wm of the chamfered sipe 41 and the opening width Wp of the adjacent sipe 47 is (Wm/Wp) <1.2, the opening width Wm of the chamfered sipe 41 is excessively small, and therefore, it may be difficult to secure the volume of the chamfered sipe 41. In this case, it is difficult to secure drainage in the chamfered sipe 41, and it may be difficult to secure moisture performance due to the chamfered sipe 41. Further, in the case where the relationship between the opening width Wm of the chamfered sipe 41 and the opening width Wp of the adjacent sipe 47 is (Wm/Wp) >6.0, the opening width Wm of the chamfered sipe 41 is excessively large, and therefore, the peripheral rigidity of the chamfered sipe 41 in the land portion 20 may become excessively small. In this case, since the rigidity of a part of the land portion 20 is reduced, it may be difficult to ensure the driving stability during the vehicle running.

On the other hand, if the relationship between the opening width Wm of the chamfered sipe 41 and the opening width Wp of the adjacent sipe 47 is within the range of 1.2 ≦ (Wm/Wp) ≦ 6.0, it is possible to suppress the rigidity of the portion of the land portion 20 located around the chamfered sipe 41 from becoming excessively small while ensuring the volume of the chamfered sipe 41. As a result, the wet performance can be more reliably ensured while suppressing a decrease in driving stability.

Further, since the relationship between the opening width Wm of the chamfered sipe 41 and the groove bottom width Wm1 is in the range of 0.1 ≦ (Wm1/Wm) ≦ 0.85, the volume of the chamfered sipe 41 can be secured, and the rigidity around the chamfered sipe 41 in the land portion 20 can be suppressed from becoming excessively small. That is, when the relationship between the opening width Wm of the chamfered sipe 41 and the groove bottom width Wm1 is (Wm1/Wm) <0.1, the groove bottom width Wm1 of the chamfered sipe 41 is excessively small, and therefore, it may be difficult to secure the volume of the chamfered sipe 41. In this case, it is difficult to secure drainage in the chamfered sipe 41, and it may be difficult to secure moisture performance due to the chamfered sipe 41. Further, when the relationship between the opening width Wm of the chamfered sipe 41 and the groove bottom width Wm1 is (Wm1/Wm) >0.85, the groove bottom width Wm1 of the chamfered sipe 41 is excessively large, and therefore, there is a possibility that the rigidity around the chamfered sipe 41 in the land portion 20 becomes excessively small. In this case, since the rigidity of a part of the land portion 20 is reduced, it may be difficult to ensure the driving stability during the vehicle running.

On the other hand, when the relationship between the opening width Wm of the chamfered sipe 41 and the groove bottom width Wm1 is in the range of 0.1 ≦ (Wm1/Wm) ≦ 0.85, the rigidity of the portion of the land portion 20 located around the chamfered sipe 41 can be suppressed from becoming too small while ensuring the volume of the chamfered sipe 41. As a result, the wet performance can be ensured while suppressing a decrease in driving stability more reliably.

Also, the adjacent sipe 47 communicates with the two main grooves 30 for partitioning the land portion 20, that is, penetrates the land portion 20 in which the adjacent sipe 47 is formed in the tire width direction, and therefore, the rigidity of the periphery of the portion of the land portion 20 in which the adjacent sipe 47 is formed can be further reliably reduced. Thereby, when the portion of the land portion 20 located around the chamfered sipe 41 comes into contact with the ground, it is possible to further reliably and easily press the adjacent sipe 47, and to load the deformation of the land portion 20 on the adjacent sipe 47 by pressing the adjacent sipe 47. Therefore, squeezing of the chamfered sipe 41 can be further reliably suppressed, so that the volume of the chamfered sipe 41 can be ensured, and drainage in the chamfered sipe 41 can be improved. As a result, the moisture performance can be further reliably improved.

Further, in the chamfered sipe 41 and the adjacent sipe 47, the relationship between the groove depth Dm of the chamfered sipe 41 and the groove depth Dp of the adjacent sipe 47 is in the range of 1.2 ≦ (Dp/Dm) ≦ 8.0, and therefore, it is possible to suppress the squeezing of the chamfered sipe 41 by the squeezing of the adjacent sipe 47 while suppressing the rigidity of the vicinity of the adjacent sipe 47 in the land portion 20 from becoming excessively small. That is, when the relationship between the groove depth Dm of the chamfered sipe 41 and the groove depth Dp of the adjacent sipe 47 is (Dp/Dm) <1.2, the groove depth Dp of the adjacent sipe 47 is too shallow, and therefore, there is a possibility that it is difficult to load the deformation of the land portion 20 by the pressing of the adjacent sipe 47. In this case, when the portion of the land portion 20 located around the chamfered sipe 41 comes into contact with the ground, there is a possibility that it is difficult to suppress the squeezing of the chamfered sipe 41 and to ensure drainage in the chamfered sipe 41. Further, when the relationship between the groove depth Dm of the chamfered sipe 41 and the groove depth Dp of the adjacent sipe 47 is (Dp/Dm) >8.0, the groove depth Dp of the adjacent sipe 47 is excessively deep, and therefore, the rigidity in the vicinity of the adjacent sipe 47 in the land portion 20 may become excessively small. In this case, since the rigidity of the land portion 20 is lowered, it may be difficult to ensure driving stability during vehicle traveling.

In contrast, when the relationship between the groove depth Dm of the chamfered sipe 41 and the groove depth Dp of the adjacent sipe 47 is in the range of 1.2 ≦ (Dp/Dm) ≦ 8.0, it is possible to suppress the pressing of the chamfered sipe 41 when the portion of the land portion 20 located around the chamfered sipe 41 comes into contact with the ground while suppressing the rigidity of the vicinity of the adjacent sipe 47 in the land portion 20 from becoming too small. As a result, the wet performance can be further ensured while suppressing a decrease in driving stability.

Further, since the relationship between the groove depth Dm of the chamfered sipe 41 and the chamfer portion depth Dm1 is in the range of 0.1 ≦ (Dm1/Dm) ≦ 0.85, it is possible to improve the drainage in the chamfered sipe 41 by the chamfer portion 42 while suppressing a decrease in the rigidity of the land portion 20. That is, when the relationship between the groove depth Dm of the chamfered sipe 41 and the chamfer portion depth Dm1 is (Dm1/Dm) <0.1, since the chamfer portion depth Dm1 of the chamfered sipe 41 is excessively shallow, even if the chamfer portion 42 is provided in the chamfered sipe 41, it may be difficult to improve the drainage property in the chamfered sipe 41 by the chamfer portion 42. When the relationship between the groove depth Dm of the chamfered sipe 41 and the chamfered portion depth Dm1 is (Dm1/Dm) >0.85, the chamfered portion depth Dm1 of the chamfered sipe 41 is too deep, and therefore, the volume of the portion of the land portion 20 located around the chamfered sipe 41 is reduced, and the rigidity of the land portion 20 forming the chamfered sipe 41 may be easily reduced.

On the other hand, when the relationship between the groove depth Dm of the chamfered sipe 41 and the chamfer portion depth Dm1 is in the range of 0.1 ≦ (Dm1/Dm) ≦ 0.85, the chamfered portion 42 can effectively improve drainage in the chamfered sipe 41 while suppressing a decrease in rigidity of the land portion 20 in which the chamfered sipe 41 is formed. As a result, the wet performance can be more reliably ensured while suppressing a decrease in driving stability.

Further, since the plurality of chamfered sipes 41 formed in the same land portion 20 communicate with the same main groove 30, a difference in rigidity can be generated between one side edge of the land portion 20 divided by the main groove 30 communicating with the chamfered sipe 41 and one side edge of the land portion divided by the main groove 30 on the opposite side. Thus, in the one-side edge end of the land portion 20 divided by the main groove 30 communicated by the chamfered sipe 41, the pressing of the adjacent sipe 47 can be facilitated by reducing the rigidity of the land portion 20, and the pressing of the chamfered sipe 41 can be suppressed by the pressing of the adjacent sipe 47. Further, in the edge end on the side divided by the main groove 30 on the opposite side of the main groove 30 where the chamfered sipe 41 in the land portion 20 communicates, the number of sipes 40 communicating with the main groove 30 is reduced, and the rigidity of the land portion 20 is secured, whereby the rigidity feeling in the initial driving period when the vehicle is running can be improved. As a result, the wet performance can be more reliably ensured while suppressing a decrease in driving stability.

[ modified examples ]

Further, in the above-described embodiment, the non-chamfered sipe 46 communicates with both the main grooves 30 for partitioning the land portion 20, but the non-chamfered sipe 46 may not communicate with both the main grooves 30. Fig. 6 is an explanatory view of a modification of the pneumatic tire 1 according to the embodiment, in which the non-chamfered sipe 46 communicates with only one side of the main groove 30. For example, as shown in fig. 6, among the two main grooves 30 that divide both sides in the tire width direction of the land portion 20, the chamfer-free sipe 46 communicates with only one main groove 30, and an end portion on the opposite side of an end portion on the side communicating with the main groove 30 may terminate within the land portion 20. That is, one end of the adjacent sipe 47 and the distal sipe 48 may communicate with the main groove 30, and the other end may terminate within the land portion 20. At this time, it is preferable that, as shown in fig. 6, of the two main grooves 30 for partitioning the land portion 20, a plurality of non-chamfered sipes 46 communicate with the main grooves 30 identical to the main grooves 30 communicating with the chamfered sipe 41. In this case, it is preferable that the relationship between the length Lm of the chamfered sipe 41 and the length Lp of the adjacent sipe 47 is within the range of 0.2 ≦ (Lm/Lp) ≦ 0.95 in the chamfered sipe 41 and the adjacent sipe 47 even if the non-chamfered sipe 46 is connected to only one side of the main groove 30.

Also, in the above-described embodiment, the plurality of chamfered sipes 41 formed on the same land portion 20 communicate with the same main groove 30, but the plurality of chamfered sipes 41 may not communicate with the same main groove 30. Fig. 7 is an explanatory view of a modification of the pneumatic tire 1 according to the embodiment, in which the chamfered sipe 41 communicates with different main grooves 30. As shown in fig. 7, the chamfered sipes 41 may communicate with different main grooves 30 between the chamfered sipes 41 formed on the same land portion 20. In this case, the non-chamfered sipe 46 and the chamfered sipe 41 adjacent in the tire circumferential direction may communicate with different main grooves 30, or a case where the non-chamfered sipe 46 and the chamfered sipe 41 adjacent in the tire circumferential direction communicate with different main grooves 30 and a case where the non-chamfered sipe 41 and the chamfered sipe 41 adjacent in the tire circumferential direction communicate with the same main groove 30 may coexist among a plurality of chamfered sipes 41 formed on the same land portion 20.

Further, in the above-described embodiment, the land portion 20 forming the sipe 40 has a rim shape, but the land portion 20 may have a shape other than the rim shape. Fig. 8 is an explanatory view of a modification of the pneumatic tire 1 according to the embodiment, in which the land portion 20 is in a block shape. For example, as shown in fig. 8, the land portion 20 may be divided into two sides in the tire width direction by the main groove 30 and two sides in the tire circumferential direction by the lug groove 35, that is, may have a so-called block shape. That is, in the tread surface 3 of the tread portion 2, a plurality of lateral grooves 35 extending in the tire width direction are formed in addition to the main grooves 30 extending in the tire circumferential direction, and the land portion 20 forming the sipe 40 may be divided by the main grooves 30 and the lateral grooves 35. In this case, it is preferable that in one block land portion 20, the sipe 40 is a sipe in which a plurality of chamfered sipes 41 and non-chamfered sipes 46 are alternately provided in the tire circumferential direction. In the sipe 40, when the chamfered sipe 41 and the non-chamfered sipe 46 are alternately provided in the tire circumferential direction, the shape of the land portion 20 forming the sipe 40 is not limited.

In the above-described embodiment, the rotational direction of the pneumatic tire 1 is not particularly limited, but the pneumatic tire 1 may be a pneumatic tire 1 in which the rotational direction when mounted on a vehicle is specified. That is, the pneumatic tire 1 in which the sipe 40 is formed may be a pneumatic tire 1 mounted on a vehicle so as to rotate in a rotation direction in which a rotation axis is designated as a center when the vehicle advances. In this case, the pneumatic tire 1 includes a rotation direction indicating section (not shown) indicating a rotation direction. The rotation direction indicating portion is constituted by, for example, a mark or a concave-convex portion attached to the sidewall portion 8 of the tire.

Fig. 9 is a modification of the pneumatic tire 1 according to the embodiment, and is a schematic view regarding the configuration of the sipe 40 with respect to the rotational direction of the pneumatic tire 1. The pneumatic tire 1 in which the chamfered sipes 41 and the non-chamfered sipes 46 are alternately provided on the tread surface 3 in the tire circumferential direction may be a pneumatic tire 1 designated with a rotation direction when mounted on a vehicle. In this case, it is preferable that, as shown in fig. 9, among the chamfered sipe 41 and the adjacent sipe 47, the adjacent sipe 47 is provided on the side which contacts the ground first in the tire rotation direction, and the chamfered sipe 41 is provided on the side which contacts the ground later in the tire rotation direction.

The side that first contacts the ground surface in the tire rotation direction in this case is the rotation direction side when the pneumatic tire 1 is rotated in a predetermined direction, and when the pneumatic tire 1 is mounted on a vehicle and rotated in a predetermined direction for running, the side first contacts the road surface 100 or first separates from the road surface 100. The side of the pneumatic tire 1 that contacts the ground at the rear in the tire rotation direction is the opposite side of the rotation direction when the pneumatic tire 1 is rotated in a predetermined direction, and when the pneumatic tire 1 is mounted on a vehicle and rotated in a predetermined direction to travel, the side comes into contact with the road surface 100 after the portion that contacts the ground at the front, or the side comes away from the road surface 100 after the portion that contacts the ground at the front.

Among the chamfered sipes 41 and the adjacent sipes 47 arranged in the tire circumferential direction, the adjacent sipe 47 is provided on the side which first contacts the ground in the tire rotational direction, and since the adjacent sipe 47 contacts the road surface 100 earlier than the chamfered sipe 41, the adjacent sipe 47 may further load the deformation of the land portion 20. This can further reliably suppress the squeezing of the chamfered sipe 41, and can further reliably improve the wetting performance.

The land portion 20 forming the sipe 40 may have a shape in which the tread surface 3 protrudes outward in the tire radial direction. Fig. 10 is a schematic view of a modification of the pneumatic tire 1 according to the embodiment, and is a main portion of the protruding land portion 20. As shown in fig. 10, in a tire meridian cross-sectional view, the land portion 20 forming the chamfered sipe 41 may have the tread surface 3 protruding outward in the tire radial direction from the reference contour line Pf of the tread contour. The reference contour line Pf of the tread contour in this case is a contour line of the reference of the tread surface 3 shape of the land portion 20 in the state of not being filled with the internal pressure. In detail, in a tire meridian plane cross-sectional view in a state of not being filled with an internal pressure, the reference contour line Pf of the tread contour means an arc drawn with a maximum radius of curvature with its center located on the tire radial direction inner side of the tread surface 3 through at least 3 of the 4 open ends E of the two main grooves 30 on the adjacent both sides in the tire width direction of the land portion 20.

In the land portion 20 where the chamfered sipe 41 is formed, the radius of curvature of the tread surface 3 in the tire meridian cross-sectional view is smaller than the radius of curvature of the reference contour line Pf of the tread contour specified as described above. Therefore, the shape of the tread surface 3 in the tire meridian cross-sectional view of the land portion 20 is a shape protruding outward in the tire radial direction from the reference contour line Pf of the tread contour. Therefore, the land portion 20 is thicker at the center in the tire width direction than at the opposite ends in the tire width direction.

Since the tread surface 3 of the land portion 20 has such a shape that protrudes outward in the tire radial direction than the reference contour line Pf of the tread contour, water located between the tread surface 3 and the road surface can be distributed to the main grooves 30 of the land portion 20 at the end portions that define the tire width direction during running on a wet road surface. This can further reliably improve the drainage property and the moisture performance.

Also, in the above-described embodiment, the chamfered sipe 41 or the non-chamfered sipe 46 is illustrated as extending in a straight line shape in the tire width direction, but each sipe 40 may have other shapes. The sipe 40 may extend in the tire width direction while being inclined toward the tire circumferential direction, or may extend in the tire width direction while being repeatedly flexed or bent toward the tire circumferential direction.

In the above embodiment, the number of the main grooves 30 is 3, but the number of the main grooves 30 may be other than 3. Preferably, the number of the main grooves 30 formed in the tread portion 2 is in the range of 3 or more and 5 or less. Further, when extending in the tire circumferential direction, the main groove 30 may have a shape other than a straight line, for example, extending in the tire circumferential direction while repeatedly bending or curving in the tire width direction.

Examples

Fig. 11A to 11D are graphs showing the results of performance evaluation tests of pneumatic tires. Hereinafter, a performance evaluation test performed on a conventional pneumatic tire, the pneumatic tire 1 of the present invention, and a pneumatic tire of a comparative example to which the pneumatic tire 1 of the present invention is compared will be described with respect to the pneumatic tire 1 described above. Performance evaluation test wet braking performance and driving stability as braking performance on a wet road surface were tested.

The performance evaluation test was performed as follows: a pneumatic tire 1 having a tire name of 195/65R 1591H specified in JATMA was rim-assembled on a rim wheel of JATMA standard having a rim size of 15 × 6.5J, the air pressure was adjusted to 250kPa, and the wheel was mounted on an evaluation vehicle to run the evaluation vehicle.

In the evaluation method of each test item, with respect to wet braking performance, on a test route, an evaluation vehicle mounted with a test tire is driven on a road surface where water is scattered at an initial speed of 100km/h, a braking distance at the time of braking is measured, and the reciprocal of the measured distance is expressed using an index whose conventional example described below is set to 100. The larger the value, the shorter the distance required for braking, indicating excellent wet braking performance.

Also, the driving stability when the evaluation vehicle mounted with the test tire was run on a test route on a dry road surface was compared by sensory evaluation of the test driver for the driving stability. The driving stability is represented by an index in which the sensory evaluation of the test driver is set to 100 in the conventional example described below, and the larger the index is, the more excellent the driving stability is represented. When the index of the driving stability is 98 or more, it is considered that the reduction of the driving stability is suppressed.

The performance evaluation test was performed on 32 kinds of conventional pneumatic tires as an example of conventional pneumatic tires, examples 1 to 29 as the pneumatic tire 1 of the present invention, and comparative examples 1 and 2 as pneumatic tires to be compared with the pneumatic tire 1 of the present invention. Among them, the conventional example has no neighboring sipe 47 near the chamfered sipe 41. Also, comparative example 1 has the neighboring sipe 47 close to the chamfered sipe 41, but the ratio of the distance b between the chamfered sipe 41 and the distal sipe 48 to the distance a between the chamfered sipe 41 and the neighboring sipe 47 is less than 1.5. Also, comparative example 2 has the same adjacent sipe 47 as comparative example 1, but the ratio of the distance b between the chamfered sipe 41 and the distal sipe 48 to the distance a between the chamfered sipe 41 and the adjacent sipe 47 is greater than 12.

In contrast, in examples 1 to 29 as examples of the pneumatic tire 1 of the present invention, the ratio of the distance a between the chamfered sipe 41 and the adjacent sipe 47 with respect to the distance b between the chamfered sipe 41 and the distal sipe 48 is within the range of 1.5 ≦ (b/a) ≦ 12. In the pneumatic tires 1 of examples 1 to 29, the following elements are different: the ratio of the length Lm of the chamfered sipe 41 to the length Lp of the adjacent sipe 47 (Lm/Lp), the direction in which the chamfered portion 42 is provided in the chamfered sipe 41, the ratio of the opening width Wm of the chamfered sipe 41 to the opening width Wp of the adjacent sipe 47 (Wm/Wp), the ratio of the opening width Wm of the chamfered sipe 41 to the groove bottom width Wm1 (Wm1/Wm), whether or not the adjacent sipe 47 communicates with the two main grooves 30 for partitioning the land portion 20, the ratio of the groove depth Dm of the chamfered sipe 41 to the groove depth Dp of the adjacent sipe 47 (Dp/Dm), the ratio of the groove depth Dm 39dm of the chamfered sipe 41 to the chamfer portion Dm1 (Dm1/Dm), the main grooves 30 in which the plurality of chamfered sipes 41 formed on the same land portion 20 communicate, the sipe 40 located on the side which contacts the ground first in the tire rotation direction, and the main grooves 30 in which the adjacent sipes 47 communicate with each other, The tire has a land portion 20 having a tread surface 3 projecting outward in the tire radial direction.

As shown in fig. 11A to 11D, the pneumatic tires 1 of examples 1 to 29 can improve the wet braking performance while suppressing the reduction of the steering stability as much as possible, as compared with the conventional example or comparative examples 1 and 2, as seen from the results of the performance evaluation test using such pneumatic tires 1. That is, the pneumatic tires 1 of examples 1 to 29 can ensure the wet performance while suppressing the reduction of the driving stability.

Description of the reference numerals

1 pneumatic tire

2 tread portion

3 Tread surface

4 Tread rubber layer

5 shoulder part

8 side wall part

10 bead part

11 bead core

12 bead filler

13 carcass ply

14 Belt layer

16 inner liner

17 rim cushion rubber

18 inner surface of tyre

20 ring bank part

30 main groove

35 horizontal groove

40 sipe

41 chamfer sipe

41a, 47a, 48a wall surface

41b, 47b groove bottom

42 chamfered part

46 chamfer sipe

47 adjacent sipes

48 distal sipes