tire

Abstract

To provide a tire improved in on-ice gripping performance.SOLUTION: A tire 10 is equipped with at least one sipe unit 60 on at least one land part to configure a pair of sipes. One sipe 6a and the other sipe 6b respectively have both ends terminating in the land part. The one sipe 6a and the other sipe 6b are disposed oppositely to each other in a tire circumferential direction, and respectively have long sides extending in a tire width direction. The one sipe 6a has a short side 62a extending from an end e1 on either one side in the tire width direction of the long side 61a so as to approach the other sipe 6b side, and the other sipe 6b has a short side 62b extending from an end e2 on the other side in the tire width direction of the long side 61b so as to approach the one sipe 6a side.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a tire.

Background Art

[0002] Conventionally, there has been known a tire that improves ice grip performance by arranging sipes at high density while suppressing a decrease in rigidity (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the above Patent Document 1, the compatibility between suppressing a decrease in rigidity and arranging sipes at high density is not sufficient, and there is still room for improvement in ice grip performance.

[0005] Therefore, an object of the present invention is to provide a tire with improved ice grip performance.

Means for Solving the Problems

[0006] The gist of the present invention is as follows. A tire having at least one land portion on a tread surface of the tire, where at least one of the land portions includes at least one sipes unit composed of a pair of sipes, where one of the pair of sipes and the other of the pair of sipes that constitute the pair of sipes each have both ends terminated within the land portion, where the one of the pair of sipes and the other of the pair of sipes are arranged to face each other in the tire circumferential direction and each have a long side extending in the tire width direction, The aforementioned sipe has a short side that extends from either end of the long side in the tire width direction toward the other sipe, The other sipe is characterized in that it has a short side that extends from the other end of the long side in the tire width direction toward the side of the first sipe. According to the tire of the present invention, ice grip performance can be improved.

[0007] In the tire of the present invention, Preferably, the long sides and short sides of one sipe and the other sipe extend parallel to each other, and the one sipe and the other sipe are offset from each other in the tire width direction. This allows the braking and driving forces from the edge components to be fully utilized, and also helps to equalize the ground pressure distribution on the land area.

[0008] In the tire of the present invention, Preferably, the angle between the long side and the short side of one sipe and the other sipe, where they face each other, is 90° or more. This improves tire productivity, prevents large differences in contact pressure, and allows for more effective braking and driving force in the circumferential direction of the tire.

[0009] In the tire of the present invention, Preferably, the shorter side of each of the two sipes extends along the circumferential direction of the tire. This prevents large differences in contact pressure and allows for more effective braking and driving force in the circumferential direction of the tire.

[0010] In the tire of the present invention, It is preferable that one sipe and the other sipe are congruent to each other. This makes it easier to arrange sipe units uniformly and at a high density on land.

[0011] In the tire of the present invention, Preferably, the ratio of the length of the long side to the length of the short side to the length of the other sipe is 1 to 15. This makes it possible to suppress an excessive decrease in sipe density or an excessive decrease in land area rigidity, and also improve the durability of the blades that form the sipes during tire manufacturing.

[0012] In the tire of the present invention, Preferably, the ratio of the circumferential length of the sipe unit to the length in the tire width direction is 0.1 to 2.6. This allows for greater block rigidity and provides a more effective braking and driving force.

[0013] In the tire of the present invention, Multiple sipe units are arranged adjacent to each other in the circumferential direction of the tire to form a row of sipe units. In the row of sipe units, it is preferable that in the plurality of sipe units, the short sides of one of the plurality of sipes in the plurality of sipes extend along the same straight line along the tire circumferential direction, and the short sides of the other of the plurality of sipes extend along the same straight line along the tire circumferential direction. This makes it easy to arrange a plurality of sipe units uniformly and at a high density without forming unnecessary voids in the land area. [Effects of the Invention]

[0014] The present invention makes it possible to provide a tire with improved grip performance on ice. [Brief explanation of the drawing]

[0015] [Figure 1] This figure schematically shows an unfolded view of the tread surface of a tire according to one embodiment of the present invention. [Figure 2] It is a view showing an enlarged view of the sipe unit in FIG. 1. [Figure 3A] It is a view for explaining the arrangement of the sipe units in FIG. 1. [Figure 3B] It is a view for explaining another example of the arrangement of the sipe units. [Figure 4] It is a view showing an enlarged view of one of the block land portions in FIG. 1. [Figure 5] FIG. 5(a) is a view showing a comparative example of the block land portion, FIG. 5(b) is a view showing a comparative example of the block land portion, FIG. 5(c) is a view showing a comparative example of the block land portion, FIG. 5(d) is a view showing an example of the block land portion, FIG. 5(e) is a view showing an example of the block land portion, and FIG. 5(f) is a view showing an example of the block land portion. [Figure 6] It is a graph showing the block rigidity and the actual contact area in the comparative examples and examples shown in FIG. 5.

Mode for Carrying Out the Invention

[0016] Hereinafter, embodiments of the tire according to the present invention will be exemplarily described with reference to the drawings. The same reference numerals are assigned to the common components in each figure.

[0017] FIG. 1 is a plan view schematically showing a state in which the tread surface of a tire according to an embodiment of the present invention is developed.

[0018] In this specification, the "tread surface (1)" means the outer peripheral surface extending over the entire circumference of the tire that comes into contact with the road surface when a tire assembled to a rim and filled with a predetermined internal pressure is rolled under a state of being loaded with the maximum load. In this specification, the "tread edge (TE)" means the edge in the tire width direction of the tread surface (1). Here, "rim" refers to the standard rim for applicable sizes (Measuring Rim in ETRTO's STANDARDS MANUAL, Design Rim in TRA's YEAR BOOK) which is an industrial standard valid in the region where the tire is produced and used, and is listed or will be listed in the future in publications such as the JATMA YEAR BOOK of JATMA (Japan Automobile Tire Manufacturers Association) in Japan, the STANDARDS MANUAL of ETRTO (The European Tyre and Rim Technical Organization) in Europe, and the YEAR BOOK of TRA (The Tire and Rim Association, Inc.) in the United States. (That is, the above "rim" includes not only current sizes but also sizes that may be included in the above industrial standards in the future. An example of "sizes that will be listed in the future" is the size listed as "FUTURE DEVELOPMENTS" in the 2013 edition of ETRTO's STANDARDS MANUAL.) However, in the case of sizes not listed in the above industrial standards, it refers to a rim with a width corresponding to the tire bead width. Furthermore, "specified internal pressure" refers to the air pressure (maximum air pressure) corresponding to the maximum load capacity of a single wheel in the applicable size and ply rating as described in the JATMA YEAR BOOK, etc., and in the case of sizes not listed in the above industrial standards, it refers to the air pressure (maximum air pressure) corresponding to the maximum load capacity specified for each vehicle on which the tire is mounted. "Maximum load capacity" refers to the load corresponding to the maximum load capacity mentioned above. Note that the air referred to here can be replaced with an inert gas such as nitrogen gas or other alternatives.

[0019] In this specification, unless otherwise specified, the dimensions of each element such as grooves, sipes, and block surfaces shall be measured in the "standard condition" described below. The "standard condition" refers to the state in which the tire is mounted on the rim, filled to the specified internal pressure, and unloaded. Here, the dimensions of each element such as grooves, sipes, and block surfaces on the tread surface shall be measured in a flat view of the tread surface. Here, in this specification, "flat view of the tread surface" refers to a plan view of the tread surface when the tread surface is laid out on a plane.

[0020] In this specification, "groove width" means measured in a cross section perpendicular to the direction of extension of the grooves on the tread surface, in the standard condition described above, and in a direction parallel to the tread surface. The groove width may be constant or vary in the direction perpendicular to the tread surface. However, unless otherwise specified in this specification, "groove width" refers to the groove width on the tread surface. Furthermore, in this specification, "groove depth" means measured in a direction perpendicular to the tread surface, in the standard condition described above.

[0021] In this specification, "sipe" means a sipe with a width of 1 mm or less over an area of ​​50% or more of the sipe depth in the above-mentioned standard condition. Preferably, the sipe width is 0.6 mm or less. Here, "sipe depth" is measured in the direction perpendicular to the tread surface in the above-mentioned standard condition, and "sipe width" is measured in the direction parallel to the tread surface in a cross section perpendicular to the direction in which the sipe extends on the tread surface in the above-mentioned standard condition. The sipe width may be constant or vary in the direction perpendicular to the tread surface.

[0022] Furthermore, in this specification, the "length along the direction of extension of the short side" and the "length along the direction of extension of the long side" of a sipe refer to the length of the center line formed by connecting the center points in the width direction of the sipe, and unless otherwise specified, the distances of each component of each sipe shall be measured with respect to the above center line in an unfolded view of the tread surface.

[0023] For convenience, in this specification, one side of the tire circumferentially (the upper side in Figure 1) will be referred to as the "tire circumferential CD1 side," and the other side of the tire circumferentially (the lower side in Figure 1) will be referred to as the "tire circumferential CD2 side." Furthermore, for convenience, in this specification, one side in the tire width direction (right side in Figure 1) will be referred to as the "WD1 side in the tire width direction," and the other side in the tire width direction (left side in Figure 1) will be referred to as the "WD2 side in the tire width direction."

[0024] A tire 10 according to one embodiment of the present invention has at least one land portion on the tread surface 1. In the example shown in Figure 1, the tire 10 of this embodiment has a plurality of (four in the illustrated example) circumferential main grooves 2 (2a, 2b, 2c, and 2d) on the tread surface 1 that extend in the circumferential direction of the tire. Each circumferential main groove 2 may extend substantially in a straight line along the circumferential direction of the tire, as shown in Figure 1, or it may extend in a zigzag or wavy shape in the circumferential direction.

[0025] The groove width of each circumferential main groove 2 is not particularly limited, but can be, for example, 4 to 15 mm. Similarly, the groove depth of each circumferential main groove 2 is not particularly limited, but can be, for example, 6 to 20 mm.

[0026] Furthermore, in this embodiment, the tire 10 has a tread surface 1 that is divided into multiple (five in the illustrated example) land areas 3 (3a, 3b, 3c, 3d, and 3e) which are demarcated by circumferential main grooves 2a, 2b, 2c, and 2d and the tread edge TE.

[0027] In this embodiment, each land area 3 is divided into multiple block land areas 5 by multiple transverse grooves 4 extending in a direction intersecting the tire circumferential direction. In the example shown in Figure 1, land area 3a is divided by transverse grooves 41 and has multiple block land areas 51 arranged along the tire circumferential direction. Land area 3b is divided by transverse grooves 42 and has multiple block land areas 52 arranged along the tire circumferential direction. Land area 3c is divided by transverse grooves 43 and has multiple block land areas 53 arranged along the tire circumferential direction. Land area 3d is divided by transverse grooves 44 and has multiple block land areas 54 arranged along the tire circumferential direction. Land area 3e is divided by transverse grooves 45 and has multiple block land areas 55 arranged along the tire circumferential direction. Furthermore, each land area 3 can also be a ribbed land area that is not demarcated by a transverse trench.

[0028] The width of each lateral groove 4 is not particularly limited, but can be, for example, 2 to 10 mm. Similarly, the depth of each lateral groove 4 is not particularly limited, but can be, for example, 5 to 20 mm.

[0029] In this embodiment, at least one sipe unit 60 consisting of a pair of sipes 6a and 6b (hereinafter also referred to as one sipe 6a and the other sipe 6b, or simply sipes 6a and 6b) is provided on at least one of the land sections, in the illustrated example, on each block land section 5. In the example shown in Figure 1, 12 sipe units 60 are provided on each of the block land sections 52, 53, and 54, and 6 sipe units 60 are provided on each of the block land sections 51 and 55.

[0030] The tread surface 1 of the tire 10 in this embodiment is not limited to the example shown in Figure 1, and may have any tread pattern as long as it has a sipe unit 60 consisting of a pair of sipes 6a and 6b.

[0031] The sipe unit 60 in the tire 10 of this embodiment will be described in detail with reference to Figure 2. Figure 2 is an enlarged view of the sipe unit 60 in Figure 1. As shown in Figure 2, one sipe 6a and the other sipe 6b, which constitute the sipe unit 60 consisting of a pair of sipes, each have their ends terminated within the land area (within the block land area 5 in this embodiment).

[0032] In this embodiment, one sipe 6a and the other sipe 6b are arranged facing each other in the tire circumferential direction and each has a long side extending in the tire width direction. In this embodiment, one sipe 6a and the other sipe 6b each have a long side that extends inclined with respect to the tire width direction so that as you move toward one side in the tire width direction, you move toward one side in the tire circumferential direction. More specifically, as shown in Figure 2, one sipe 6a and the other sipe 6b are spaced apart from each other, and at least a portion of each (in this example, a portion) is arranged facing each other in the tire circumferential direction. Also, as shown in Figure 2, one sipe 6a has a long side 61a that extends inclined with respect to the tire width direction so that as you move from the tire width direction WD2 side toward the tire width direction WD1 side toward the tire circumferential direction CD1 side. The other sipe 6b has a long side 61b that extends inclined with respect to the tire width direction so that as you move from the tire width direction WD2 side toward the tire width direction WD1 side toward the tire circumferential direction CD1 side. Thus, both the longer sides 61a and 61b inclin in the direction of the tire circumference CD1 as they move toward the tire width direction WD1, and thus extend in an upward sloping manner on the right side of the paper. Herein, in this specification, "extending in the tire width direction" means extending with at least a component in the tire width direction. That is, "extending in the tire width direction" means that it may extend in a direction along the tire width direction (i.e., at an angle of 0° with respect to the tire width direction and without inclination with respect to the tire width direction), or it may extend at an angle of inclination with respect to the tire width direction (i.e., at an angle of inclination greater than 0° with respect to the tire width direction and inclined with respect to the tire width direction). In the illustrated example, the longer sides 61a and 61b have the same inclination angles θ1 and θ2 with respect to the tire width direction, and are inclined at the same angle, but they may be inclined at different angles.

[0033] One sipe 6a has a short side 62a that extends from one end e1 of the long side 61a in the tire width direction (WD2 side in the illustrated example) toward the other sipe 6b. As shown in Figure 2, the short side 62a extends toward the side where one sipe 6a and the other sipe 6b face each other, forming a bending angle θ3 with the long side 61a. The other sipe 6b has a short side 62b that extends from the end e2 of the long side 61b on the other side (in the illustrated example, the WD1 side in the tire width direction) relative to either of the above sides in the tire width direction, approaching the side of the one sipe 6a. As shown in Figure 2, the short side 62b extends toward the side where the one sipe 6a and the other sipe 6b face each other, forming a bending angle θ4 with the long side 61b. Furthermore, in one sipe 6a and the other sipe 6b, the short side does not extend from the end of either the long side 61a and 61b in the tire width direction that is not provided with the aforementioned short sides 62a and 62b.

[0034] The following describes the effects and benefits of the tire configuration of the first embodiment. Since both ends of one sipe 6a and the other sipe 6b are terminated within the land portion (within the block land portion 5 in this embodiment), it is prevented that an open end of the sipe is formed at the edge of the block land portion 5. As a result, the land portion remains connected around the ends of sipes 6a and 6b, which increases the rigidity of the block land portion compared to when the sipes open up to the edge of the block land portion. Consequently, deformation of the block land portion 5 is suppressed, lifting at the contact surface is prevented, and the actual contact area with the road surface can be increased, thereby improving ice grip performance. Furthermore, in this embodiment, the sipes 6a and 6b are arranged facing each other in the circumferential direction of the tire, and have long sides 61a and 61b that extend inclined with respect to the tire width direction so as they move toward one side in the tire width direction, so that the edge component of the long side not only allows for sufficient braking and driving force in the circumferential direction (front-rear direction) of the tire, but also contributes to improving lateral grip performance in the tire width direction. In particular, by setting the inclination angles θ1 and θ2 to 45° or less, the tire width direction component of the long side of the sipe becomes equal to or greater than the tire circumferential component, which contributes to improving the braking and driving force, which is of the most important importance for safety.

[0035] Furthermore, in this embodiment, the sipes 6a and 6b have short sides 62a and 62b extending from the long sides 61a and 61b to opposite sides. In the manufacturing process of the tire 10, when sipes are formed in a mold using a thin metal plate (blade), the short sides act as support against bending deformation that causes the long side of the blade to collapse. This significantly increases the bending rigidity of the blade, improves durability, and enhances tire productivity.

[0036] As described above, according to this embodiment, it is possible to increase the rigidity of the land portion (and consequently the actual contact area) while maintaining the sipe density, that is, to achieve both land portion rigidity and high-density sipe arrangement, thereby improving ice grip performance.

[0037] The following describes preferred configurations and modified examples of the tire 10 of this embodiment.

[0038] In the tire 10 of this embodiment, the sipe depth of one sipe 6a and the other sipe 6b is not particularly limited, but from the viewpoint of more effectively improving grip performance on ice, it is preferable to set it to 3 mm or more, and for example, it may be 10 mm or less.

[0039] In the tire 10 of this embodiment, it is preferable that the long sides and short sides of one sipe 6a and the other sipe 6b extend parallel to each other. As shown in Figure 2, the long sides 61a and 61b extend parallel to each other, and the short sides 62a and 62b extend parallel to each other. In addition, in the tire 10 of this embodiment, it is preferable that one sipe 6a and the other sipe 6b are offset in the tire width direction. In Figure 2, when viewed along the tire circumferential direction in an unfolded view of the tread surface 1, the sipes 6a and 6b are arranged such that a portion of them overlap in the tire width direction, and their phases are shifted in the tire width direction (i.e., a portion of them do not overlap in the tire width direction). By arranging the long sides and short sides of sipes 6a and 6b parallel to each other, the distances between the long sides and short sides can be kept constant in the tire circumferential direction and tire width direction, respectively. This makes it easier to arrange multiple sipe units 60 on the block land area 5 uniformly and at a high density without creating unnecessary gaps. In addition, by offsetting one sipe 6a from the other sipe 6b in the tire width direction, when the sipe unit 60 is viewed along the tire circumferential direction in an unfolded view of the tread surface 1, the sipes will be present over a wider area in the tire width direction compared to when the sipes 6a and 6b are not offset. This allows the braking and driving forces from the edge components to be fully exerted over a wider area in the tire width direction, and also helps to equalize the contact pressure distribution on the block land area 5.

[0040] In the tire 10 of this embodiment, the long sides 61a and 61b of sipes 6a and 6b preferably extend with inclination angles θ1 and θ2 of sipes 6a and 6b, respectively, of 0° or more and 45° or less with respect to the tire width direction, and more preferably extend with an angle greater than 0° and less than 45°. By setting the inclination angles θ1 and θ2 to 0° or more and 45° or less, the braking force and driving force in the tire circumferential direction (front-rear direction) due to the edge component of the long side are sufficiently exerted. By setting the inclination angles θ1 and θ2 to greater than 0°, an edge effect can be obtained in the tire width direction as well, and by setting the inclination angles θ1 and θ2 to less than 45°, the braking force and driving force in the tire circumferential direction (front-rear direction) due to the edge component of the long side are more sufficiently exerted.

[0041] In the tire 10 of this embodiment, it is preferable that the angle θ3, which is the angle between the long side 61a and the short side 62a of one sipe 6a and the other sipe 6b facing each other, and the angle θ4, which is the angle between the long side 61b and the short side 62b facing each other, are 90° or more. With this configuration, when forming sipes in a mold using a blade during the manufacturing process of the tire 10, the short side of the blade provides more effective support against bending deformation that causes the long side of the blade to collapse, thereby increasing the bending rigidity of the blade, more effectively improving durability, and improving the productivity of the tire. Furthermore, by setting angles θ3 and θ4 to 90° or greater, it is possible to prevent the formation of acute corners in the land portion near the vertices of the long and short sides, that is, to prevent the formation of localized low-rigidity areas. This suppresses deformation around these areas, prevents large differences in ground pressure, and allows braking and driving forces in the circumferential direction of the tire to be exerted more effectively. Furthermore, angles θ3 and θ4 are preferably 150° or less. By setting angles θ3 and θ4 to 150° or less, a moderate bend is formed between the short and long sides compared to when the angles exceed 150°, which improves the durability of the blade that forms the sipes during tire manufacturing.

[0042] Furthermore, in the tire 10 of this embodiment, it is preferable that the short sides 62a and 62b of one sipe 6a and the other sipe 6b extend along the tire circumferential direction. Note that "extending along the tire circumferential direction" includes cases where the sides are parallel to the tire circumferential direction or inclined at a very low angle with respect to the tire circumferential direction (for example, an inclination angle of 5° or less with respect to the tire circumferential direction). With such a configuration, sipes that can exert braking and driving forces in response to inputs in the tire circumferential direction can be arranged more efficiently, and since the direction of the short side substantially coincides with the input direction of the braking and driving forces, the block land portion is not divided with respect to the input direction, and the reduction in rigidity of the land portion around the short side can be suppressed more effectively. In addition, with such a configuration, the water accumulated on the long side of the sipe by removing the water film on the ice surface can be efficiently guided in the tire circumferential direction, which is the sliding direction during braking, by the short side of the sipe that extends along the tire circumferential direction and is provided at the end of the long side, thereby promoting drainage. Furthermore, when the short sides 62a and 62b extend along the tire circumferential direction, it is preferable that angles θ3 and θ4 be between 90° and 135°, in order to form an appropriate bend between the short and long sides, thereby more effectively improving the durability of the blades that form the sipes during tire manufacturing, and to ensure that braking and driving forces in the tire circumferential direction (front-rear direction) are fully exerted by the edge component of the long side. As mentioned above, by setting the inclination angle of the long side with respect to the tire width direction to 0 to 45°, the effect on the braking and driving performance, which is the most important for safety, can be maximized. In order to keep the short side roughly along the circumferential direction while maintaining this angle, the bend angle between the long and short sides needs to be between 90 and 135°. In the tire 10 of this embodiment, for example, the inclination angles θ1 and θ2 of the long sides 61a and 61b are 30°, and angles θ3 and θ4 are 120°.

[0043] In the tire 10 of this embodiment, it is preferable that one sipe 6a and the other sipe 6b are contiguous. With this configuration, it is easy to arrange the sipe units 60 uniformly and at a high density in the block land portion 5. Here, "congruent" refers to congruence including mirror images, meaning that in a view of the tread surface, they completely overlap each other through translation, rotation, and / or symmetry.

[0044] In the tire 10 of this embodiment, it is preferable that the ratio of the lengths of the long sides 61a and 61b along the extending direction to the lengths of the short sides 62a and 62b, respectively, is between 1 and 15. In Figure 2, it is preferable that the ratio of the length L2 of the long side 61a along the extending direction to the length L1 of the short side 62a along the extending direction is between 1 and 15, and the ratio of the length L4 of the long side 61b along the extending direction to the length L3 of the short side 62b along the extending direction is between 1 and 15. With such a configuration, by having a ratio of the length of the long side to the length of the short side of 1 or more, it is possible to suppress an excessive decrease in sipe density or an excessive decrease in the rigidity of the land portion, and by having a ratio of the length of the long side to the length of the short side of 15 or less, it is possible to improve the durability of the blades that form the sipes during tire manufacturing.

[0045] In the tire 10 of this embodiment, the lengths L2 and L4 along the extending direction of the long sides 61a and 61b are not particularly limited, but from the viewpoint of maintaining the rigidity of the block land portion 5 while fully demonstrating the ice grip performance of the tire, and from the viewpoint of enabling application to a variety of tires, it is preferable that they be 3 to 15 mm.

[0046] Furthermore, in the tire 10 of this embodiment, the lengths L1 and L3 along the extending direction of the short sides 62a and 62b are not particularly limited, but from the viewpoint of more effectively improving the durability of the blades that form the sipes during tire manufacturing, it is preferable that they be 1 mm or more and less than the same value as the lengths L2 and L4 along the extending direction of the long sides 61a and 61b.

[0047] Furthermore, in the tire 10 of this embodiment, it is preferable that the ratio of the tire circumferential length L6 along the tire circumferential direction to the tire width direction length L5 along the tire width direction of the sipe unit 60 is 0.1 to 2.6. Here, "tire width direction length along the tire width direction" refers to the tire width direction length along a straight line parallel to the tire width direction, and in Figure 2, it refers to the distance between the end of sipe 6a on the WD2 side in the tire width direction at the center line C1 and the end of sipe 6b on the WD1 side in the tire width direction at the center line C2. "Tire circumferential length along the tire circumferential direction" refers to the tire circumferential length along a straight line parallel to the tire circumferential direction, and in Figure 2, it refers to the distance between the end of sipe 6a on the CD1 side in the tire circumferential direction at the center line C1 and the end of sipe 6b on the CD2 side in the tire circumferential direction at the center line C2. By having a ratio of 0.1 or more, the circumferential distance between sipes does not become too narrow, and block rigidity can be more sufficiently secured. Furthermore, by keeping the ratio value at 2.6 or less, the inclination angles θ1 and θ2 of the long sides 61a and 61b do not become excessive, nor do the tire width lengths of the long sides 61a and 61b become too short, thereby achieving a more sufficient effect on braking and driving force.

[0048] Figure 3A is a diagram illustrating the arrangement of the sipe units 60 in Figure 1. In the tire 10 of this embodiment, as shown in Figure 3A, when multiple sipe units 60 are arranged adjacent to each other in the circumferential direction of the tire to form a sipe unit row 7, it is preferable that in the multiple (three in the illustrated example) sipe units 60 arranged in the sipe unit row 7, the multiple (all in this example) short sides 62a arranged adjacent to each other in the circumferential direction of the tire extend along the same straight line along the circumferential direction of the tire (on the imaginary line Y1 along the circumferential direction of the tire in Figure 3A), and the multiple (all in this example) short sides 62b arranged adjacent to each other in the circumferential direction of the tire extend along the same straight line along the circumferential direction of the tire (on the imaginary line Y2 along the circumferential direction of the tire in Figure 3A). Note that, as shown in Figure 3A, adjacent sipe units 60 are spaced apart from each other and arranged facing each other in the circumferential direction of the tire. Furthermore, the "multiple short sides 62a" and "multiple short sides 62b" mentioned above refer to all "short sides 62a" and "short sides 62b" contained within the sipe unit row 7 (in the illustrated example, there are three short sides 62a and three short sides 62b). With this configuration, the phases in the tire width direction of the multiple sipe units 60 arranged adjacent to each other in the tire circumferential direction are aligned, making it easy to arrange multiple sipe units 60 uniformly and at a high density in the block land portion 5 without forming unnecessary gaps.

[0049] Figure 3B is a diagram illustrating another example of the arrangement of the sipe unit 60. As shown in Figure 3B, when multiple sipe units 60' are arranged adjacent to each other in the circumferential direction of the tire, the multiple short sides 62a' of the sipe units 60' arranged adjacent to each other in the circumferential direction of the tire may each extend parallel to the imaginary line Y3 extending along the circumferential direction of the tire and be offset in the tire width direction. In addition, the multiple short sides 62b' of the sipe units 60' arranged adjacent to each other in the circumferential direction of the tire may each extend parallel to the imaginary line Y3 extending along the circumferential direction of the tire and be offset in the tire width direction.

[0050] In the tire 10 of this embodiment, the number and density of sipe units 60 arranged on each block land portion 5 are not particularly limited. As described above, in the example shown in Figure 1, 12 sipe units 60 are arranged on each block land portion 52, 53, and 54, and 6 sipe units 60 are arranged on each block land portion 51 and 55.

[0051] The total number of sipes in one sipe and the other that constitute the sipe unit 60 located in the block land section 5 may be determined, for example, based on the sipe density SD described below.

[0052] The method for calculating sipe density SD is described below. Figure 4 is an enlarged view of one of the block land sections 53 in Figure 1. As shown in Figure 4, when block land section 53 in Figure 1 is considered a typical example of block land section 5, let n be the total number of sipes 6a (one sipe), 6b (the other sipe), 6c (one sipe), and 6d (the other sipe) within block land section 5, let d (mm) be the length of each sipe 6a, 6b, 6c, and 6d in the tire width direction (in Figure 4, the length of sipe 6a in the tire width direction is shown as d), and let h (mm) be the sipe depth of sipes 6a, 6b, 6c, and 6d. Then d × h is, for example, 150 (mm) 2 ) can be less than or equal to. Also, if the maximum length of the block land portion 5 in the tire width direction is BW (mm), the equivalent number of sipes N is expressed as d × n / BW. Here, the equivalent number of sipes N is the number obtained when the sipes 6a, 6b, 6c and 6d of this embodiment are converted to transverse sipes (equivalent sipes) that are provided so as to completely cross the block land portion 5. Furthermore, the outer contour area of ​​the block land portion 5 (mm 2 If the equivalent circumferential length of the land portion of the tire obtained by dividing ) by the aforementioned BW (mm) is denoted as BL (mm), then the average sipe spacing is expressed as BL / (N+1). Here, the average sipe spacing is the spacing of the equivalent sipes in the circumferential direction of the tire on the land portion 5 of the block when the sipes 6a, 6b, 6c, and 6d of this embodiment are converted to equivalent sipes. The sipe density SD is expressed as the reciprocal of the average sipe spacing by the following formula. SD=(N+1) / BL=((d×n / BW)+1) / BL···(Formula 1) The total number of sipes n within the block, the length d of each sipe in the tire width direction, the maximum length BW of the block in the tire width direction, and the outer contour area of ​​the block are all values ​​measured from a flat view of the tread surface. The "outer contour area" of the block refers to the area enclosed by the outer contour of the block when viewed from a flat view of the tread surface. Therefore, even if non-contact areas such as sipes, small holes, or narrow grooves are located within the block, this refers to the area that does not exclude the area of ​​such sipes, small holes, or narrow grooves.

[0053] For example, the block's land portion 5 may have multiple sipes 6a, 6b, 6c, and 6d arranged such that the sipe density SD is 0.15 or higher. This makes it possible to increase the sipe density while suppressing a decrease in the rigidity of the land portion, thereby more effectively improving the tire's grip performance on ice. [Examples]

[0054] The following describes embodiments of the present invention, but the present invention is not limited thereto.

[0055] For the test tires (Comparative Examples 1-3 and Examples 1-3) 1-6, the effect of suppressing lift at the contact surface was calculated using the finite element method (FEM). Each test tire has block sections on the tread surface as shown in Table 1 and Figures 5(a)-(f). The results for the comparative examples and examples shown in Table 1 and Figure 5 are shown in Figure 6 as a graph. As shown in Figure 6, the horizontal axis of the graph is block stiffness (N / mm), and the vertical axis of the graph is the actual contact area (mm²) under shear. 2 ) The FEM prediction calculations were performed under conditions where a vertical load was applied, calculated by multiplying the outer contour area of ​​the block's land portion by the standard contact pressure of a passenger car tire (230 kPa), to evaluate the block stiffness and contact area. For block stiffness, the shear input value in the same direction was determined when the lateral displacement in the tire circumferential direction was 1 mm. For actual contact area, it was determined by the remaining contact area when partial lift occurred, with the shear input in the tire circumferential direction being 0.3 times the vertical load mentioned above. As shown in the results in Figure 6, even with the same number of sipes and thus sipe density (between Comparative Example 1 and Example 1, Comparative Example 2 and Example 2, and Comparative Example 3 and Example 3), the Examples have greater block rigidity and actual contact area, and consequently, a greater effect in suppressing lift at the contact surface of the block's land portion, thereby improving ice grip performance.

[0056] [Table 1] [Industrial applicability]

[0057] The pneumatic tire according to the present invention can be used for any type of pneumatic tire. However, it can be used preferably for passenger car tires or truck / bus tires, and more preferably for winter passenger car tires or winter truck / bus tires. [Explanation of Symbols]

[0058] 1: Tread surface, 2, 2a, 2b, 2c, 2d: Circumferential main grooves, 3, 3a, 3b, 3c, 3d, 3e: Land area, 4, 41, 42, 43, 44, 45: Transverse grooves, 5, 51, 52, 53, 54, 55: Block land area, 6a: Sipe (one sipe), 6b: Sipe (the other sipe), 6c: Sipe (one sipe), 6d: Sipe (the other sipe), 7: Sipe row, 10: Tire, 60, 60': Sipe unit, 61a, 61b: Long side, 62a, 62a', 62b, 62b': Short side, C1, C2: Centerline, WD1, WD2: Tire width direction, CD1, CD2: Tire circumferential direction TE: Tread edge, Y1, Y2, Y3: Imaginary lines, d: Length of the sipe in the tire width direction

Claims

1. A tire having at least one land area on the tread surface of the tire, At least one of the land sections is provided with at least one sipe unit consisting of a pair of sipes, The pair of sipes, one sipe and the other sipe, each have both ends terminated within the land area. The aforementioned sipe and the aforementioned sipe are arranged facing each other in the circumferential direction of the tire, and each has a longer side extending in the width direction of the tire. The aforementioned sipe has only one short side that extends from either end of the long side in the tire width direction toward the other sipe, The other sipe has a short side that extends from the other end of the long side in the tire width direction toward the one sipe side, The one sipe and the other sipe have their long sides and short sides extending parallel to each other, and the one sipe and the other sipe are offset from each other in the tire width direction. The first sipe and the second sipe each have their short sides extending along the circumferential direction of the tire. Multiple sipe units are arranged adjacent to each other in the circumferential direction of the tire to form a row of sipe units, and the tire has multiple rows of such sipe units. Each of the aforementioned land areas is divided into multiple block land areas by multiple transverse grooves extending in a direction intersecting the tire circumferential direction. The total number of sipes within each block land area is n (pieces), the widthwise length of each sipe is d (mm), and the maximum length of each block land area in the tire width direction is BW (mm). The equivalent number of sipes N is expressed as d × n / BW, and the outer contour area of ​​the block land area (mm²) is defined as follows: ２ The equivalent block land portion tire circumferential length obtained by dividing ) by the above BW (mm) is defined as BL (mm), the average sipe spacing is expressed as BL / (N+1), and the sipe density SD is the reciprocal of the above average sipe spacing, as shown in the following formula: SD=(N+1) / BL=((d×n / BW)+1) / BL When expressed as, A tire characterized in that the sipe density SD is 0.15 or greater.

2. The tire according to claim 1, wherein the angle between the long side and the short side of the one sipe and the other sipe, where the two sipes face each other, is 90° or more.

3. The tire according to claim 1 or 2, wherein one sipe and the other sipe are congruent to each other.

4. The tire according to any one of claims 1 to 3, wherein the ratio of the length of the long side to the length of the short side to the length of the other sipe is 1 to 15.

5. The tire according to any one of claims 1 to 4, wherein the ratio of the circumferential length of the tire along the tire's circumferential direction to the length along the tire's width direction is 0.1 to 2.

6.

6. The tire according to any one of claims 1 to 5, wherein in a plurality of sipe units within the row of sipe units, the short sides of one of the plurality of sipes in a plurality of pairs of sipes extend in the same straight line along the tire circumferential direction, and the short sides of the other of the plurality of sipes extend in the same straight line along the tire circumferential direction.

Images