JP7724680B2 - tire - Google Patents

Description

The present invention relates to a tire.

Conventionally, tires have been known that improve grip performance on ice by arranging sipes at a high density while minimizing a decrease in rigidity (for example, Patent Document 1).

JP 2005-186827 A

However, the technology in Patent Document 1 mentioned above was not able to sufficiently suppress a decrease in rigidity while also achieving a high density of sipes, and there was still room for improvement in grip performance on ice.

The object of this invention is to provide a tire with improved grip performance on ice.

The gist of the present invention is as follows.
A tire having at least one land portion on a tread surface of the tire,
a first sipe unit consisting of a pair of first sipes and a second sipe unit consisting of a pair of second sipes are arranged in at least one of the land portions,
Both ends of each of the first sipes and the second sipes terminate within the land portion,
one first sipe and the other first sipe constituting the pair of first sipes in the first sipe unit are arranged opposite to each other in the tire circumferential direction, and each has a long side extending at an angle with respect to the tire width direction so as to extend toward one side in the tire circumferential direction as it approaches that side in the tire width direction,
the one first sipe has a short side extending from an end of the long side on either side in the tire width direction so as to approach the other first sipe side,
the other first sipe has a short side extending from the other end of the long side in the tire width direction so as to approach the one first sipe side,
one second sipe and the other second sipe constituting the pair of second sipes in the second sipe unit are arranged opposite to each other in the tire circumferential direction and each have a long side extending in the tire width direction,
the one second sipe has a short side extending from an end of the long side on either side in the tire width direction so as to approach the other second sipe side,
the other second sipe has a short side extending from the other end of the long side in the tire width direction so as to approach the one second sipe side,
The tire, wherein the first sipe unit and the second sipe unit are disposed offset from each other in the tire width direction.
According to the tire of the present invention, grip performance on ice can be improved.

In the tire of the present invention,
It is preferable that the first sipe units and the second sipe units are arranged adjacent to each other in the tire circumferential direction to form a first sipe unit row and a second sipe unit row, respectively, and that the first sipe unit row and the second sipe unit row are arranged offset from each other in the tire width direction.
This makes it possible to more sufficiently increase the rigidity of the land portion.

In the tire of the present invention,
In the first sipe unit row, in the first sipe units, the short sides of the first sipes of the first sipes extend on the same straight line along the tire circumferential direction, and the short sides of the other first sipes extend on the same straight line along the tire circumferential direction,
It is preferable that, in the plurality of second sipe units within the second sipe unit row, the short sides of one of the plurality of second sipes extend on the same straight line along the tire circumferential direction, and the short sides of the other of the plurality of second sipes extend on the same straight line along the tire circumferential direction.
This makes it easy to arrange multiple sipe units uniformly and at high density in the land portion without forming unnecessary voids.

In the tire of the present invention,
In the first sipe unit row and the second sipe unit row adjacent to each other in the tire width direction,
Of the short sides of the one first sipe or the short sides of the other first sipe of the plurality of first sipe units in the first sipe unit row, the short side arranged on the second sipe unit row side;
It is preferable that, of the short sides of one of the second sipes or the short sides of the other of the second sipes of the plurality of second sipe units within the second sipe unit row, the short side arranged on the first sipe unit row side extends on the same straight line along the tire circumferential direction.
This allows the braking force and driving force from the edge components to be fully exerted across the entire width of the tire width direction region in which the first sipe unit row and the second sipe unit row are arranged, and also makes it possible to uniformize the ground contact pressure distribution in the block land portion.

In the tire of the present invention,
In the first sipe unit, the short sides of the one first sipe and the other first sipe extend along the tire circumferential direction,
In the second sipe unit, it is preferable that the short sides of the one second sipe and the other second sipe each extend along the tire circumferential direction.
This means:
Sipes that can exert braking force and driving force in response to input in the circumferential direction of the tire can be arranged more efficiently, and a decrease in rigidity of the land portions around the short sides can be more effectively suppressed.

In the tire of the present invention,
In the first sipe unit, the long sides of the one first sipe and the short sides of the other first sipe extend parallel to each other, and the one first sipe and the other second sipe are offset in the tire width direction,
In the second sipe unit, it is preferable that the long sides and short sides of the one second sipe and the other second sipe extend parallel to each other, and that the one second sipe and the other second sipe are offset in the tire width direction.
This allows the braking force and driving force to be fully exerted by the edge components, and also makes it possible to achieve a uniform ground contact pressure distribution on the land portions.

In the tire of the present invention,
In the first sipe unit, the one first sipe and the other first sipe each have an angle formed by the long side and the short side on a side where the one first sipe and the other first sipe face each other of 90° or more,
In the second sipe unit, it is preferable that the angle between the long side and the short side of the one second sipe and the other second sipe on the side where the one second sipe and the other second sipe face each other is 90° or more.
This makes it possible to improve tire productivity, prevent contact pressure differences from becoming large, and more effectively exert braking force and driving force in the tire circumferential direction.

In the tire of the present invention,
In the first sipe unit, the one first sipe and the other first sipe are congruent with each other,
In the second sipe unit, the one second sipe and the other second sipe are preferably congruent with each other.
This makes it easier to arrange the sipe units uniformly and with high density in the land portion.

In the tire of the present invention,
In the first sipe unit, the one first sipe and the other first sipe each have a ratio of a length along the extension direction of the long side to a length along the extension direction of the short side of the one first sipe and the other first sipe being 1 to 15,
In the second sipe unit, it is preferable that the ratio of the length along the extension direction of the long side to the length along the extension direction of the short side of each of the one second sipe and the other second sipe is 1 to 15.
This makes it possible to prevent an excessive decrease in sipe density or an excessive decrease in land portion rigidity, and also improve the durability of the blades that form the sipes during tire manufacturing.

In the tire of the present invention,
the first sipe unit has a ratio of a tire circumferential length along the tire circumferential direction to a tire widthwise length along the tire width direction of 0.1 to 2.6;
The second sipe unit preferably has a ratio of a circumferential length along the circumferential direction of the tire to a widthwise length along the width direction of the tire of 0.1 to 2.6.
This makes it possible to ensure sufficient block rigidity and obtain a sufficient effect on braking and driving forces.

This invention makes it possible to provide tires with improved grip performance on ice.

1 is a diagram schematically illustrating a developed view of a tread surface of a tire according to one embodiment of the present invention. FIG. 2 is a diagram for explaining a first sipe unit in FIG. 1 . 2 is a diagram for explaining a second sipe unit in FIG. 1 . FIG. 2 is an enlarged view of a portion of FIG. 1 for explaining the arrangement of a first sipe unit and a second sipe unit, etc. FIG. 10A and 10B are diagrams for explaining other arrangements of the first sipe units and the second sipe units, etc. FIG. FIG. 2 is an enlarged view of one of the block land portions in FIG. 1 . Figure 6(a) is a diagram showing a comparative example of a block land portion, Figure 6(b) is a diagram showing a comparative example of a block land portion, Figure 6(c) is a diagram showing a comparative example of a block land portion, Figure 6(d) is a diagram showing an example of a block land portion, Figure 6(e) is a diagram showing an example of an block land portion, and Figure 6(f) is a diagram showing an example of an block land portion. 7 is a graph showing block rigidity and actual ground contact area in the comparative example and the example shown in FIG. 6 .

Embodiments of a tire according to the present invention will now be described with reference to the drawings. Common components in each drawing are designated by the same reference numerals.

Figure 1 is a plan view showing a schematic exploded view of the tread surface of a tire according to one embodiment of the present invention.

In this specification, the term "tread surface (1)" refers to the outer peripheral surface of the tire that comes into contact with the road surface when the tire is mounted on a rim and inflated to a predetermined internal pressure and rolls under a maximum load.
In this specification, the term "tread edge (TE)" means the edge of the tread surface (1) in the tire width direction.
Here, "rim" refers to the standard rim (Measuring Rim in the ETRTO Standards Manual, Design Rim in the TRA Year Book) for the applicable size that is described or will be described in the future, as an industrial standard in effect in the region where the tire is produced and used, such as the JATMA Year Book of the Japan Automobile Tire Manufacturers Association (JATMA) in Japan, the Standards Manual of the European Tyre and Rim Technical Organization (ETRTO) in Europe, or the Year Book of the Tire and Rim Association, Inc. (TRA) in the United States. (In other words, 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 a "size to be described in the future" is the size listed under "FUTURE DEVELOPMENTS" in the 2013 edition of the ETRTO Standards Manual.) However, in the case of a size not described in the above industrial standards, it refers to a rim with a width that corresponds to the bead width of the tire.
Furthermore, the term "prescribed internal pressure" refers to the air pressure (maximum air pressure) corresponding to the maximum load capacity of a single wheel for the applicable size and ply rating as described in the above-mentioned JATMA YEAR BOOK, etc., and in the case of sizes not described in the above-mentioned industry standards, refers to the air pressure (maximum air pressure) corresponding to the maximum load capacity specified for each vehicle on which the tire is to be fitted.
"Maximum load" refers to the load corresponding to the maximum load capacity.
The air referred to here can be replaced with an inert gas such as nitrogen gas or the like.

In this specification, unless otherwise specified, the dimensions of each element, such as grooves, sipes, and block land portions, are measured in the "reference state" described below. "Reference state" refers to a state in which the tire is mounted on a rim, inflated to the specified internal pressure, and no load is applied. Here, the dimensions of each element, such as grooves, sipes, and block land portions, on the tread surface are measured in a developed view of the tread surface. Here, in this specification, "developed view of the tread surface" refers to a planar view of the tread surface with the tread surface developed on a plane.

In this specification, "groove width" is defined as the width measured in a direction parallel to the tread surface in a cross section perpendicular to the extension direction of the groove on the tread surface under the above-mentioned reference condition. The groove width may be constant or may vary in a direction perpendicular to the tread surface. However, in this specification, unless otherwise specified, "groove width" refers to the groove width on the tread surface. Furthermore, in this specification, "groove depth" is defined as the width measured in a direction perpendicular to the tread surface under the above-mentioned reference condition.

In this specification, "sipe" refers to 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. The sipe width is preferably 0.6 mm or less. Here, "sipe depth" is measured in a direction perpendicular to the tread surface in the above-mentioned standard condition, and "sipe width" is measured in a direction parallel to the tread surface in a cross section perpendicular to the extension direction of the sipe on the tread surface in the above-mentioned standard condition. The sipe width may be constant or may vary in the direction perpendicular to the tread surface.

In addition, in this specification, the "length along the extension direction of the short side" and "length along the extension direction of the long side" of a sipe refer to the length of the center line connecting the center points of the sipe in the width direction, and unless otherwise specified, the distance between each component of each sipe is measured in a developed view of the tread surface, using the center line as the reference.

For convenience, in this specification, one side in the tire circumferential direction (upper side in FIG. 1) is referred to as the "tire circumferential CD1 side," and the other side in the tire circumferential direction (lower side in FIG. 1) is referred to as the "tire circumferential CD2 side."
Also, for convenience, in this specification, one side in the tire width direction (the right side in FIG. 1 ) will be referred to as the "tire width direction WD1 side," and the other side in the tire width direction (the left side in FIG. 1 ) will be referred to as the "tire width direction WD2 side." Furthermore, in this specification, of the two types of sipes, sipe units, and sipe unit rows, for convenience, one will be referred to as the first sipes, the first sipe unit, and the first sipe unit row, and the other will be referred to as the second sipes, the second sipe unit, and the second sipe unit row, but these terms can be interpreted interchangeably. In other words, if one type of sipe, sipe unit, and sipe unit row is provisionally referred to as the first sipe, the first sipe unit, and the first sipe unit row, the other will simply be referred to as the second sipe, the second sipe unit, and the second sipe unit row.

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 FIG. 1, the tire 10 of this embodiment has multiple (four in the illustrated example) circumferential main grooves 2 (2a, 2b, 2c, and 2d) extending in the tire circumferential direction on the tread surface 1. As shown in FIG. 1, each circumferential main groove 2 may extend substantially linearly along the tire circumferential direction, or may extend circumferentially in a zigzag or wavy pattern, etc.

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 the circumferential main groove 2 is not particularly limited, but can be, for example, 6 to 20 mm.

Furthermore, the tire 10 of this embodiment has a tread surface 1 defined by circumferential main grooves 2a, 2b, 2c, and 2d and a tread edge TE, and defines multiple (five in the illustrated example) land portions 3 (3a, 3b, 3c, 3d, and 3e).

In this embodiment, each land portion 3 is divided into a plurality of block land portions 5 by a plurality of lateral grooves 4 extending in a direction intersecting the tire circumferential direction. In the example shown in FIG. 1 , land portion 3a is divided by lateral grooves 41 and has a plurality of block land portions 51 arranged along the tire circumferential direction. Land portion 3b is divided by lateral grooves 42 and has a plurality of block land portions 52 arranged along the tire circumferential direction. Land portion 3c is divided by lateral grooves 43 and has a plurality of block land portions 53 arranged along the tire circumferential direction. Land portion 3d is divided by lateral grooves 44 and has a plurality of block land portions 54 arranged along the tire circumferential direction. Land portion 3e is divided by lateral grooves 45 and has a plurality of block land portions 55 arranged along the tire circumferential direction.
Each land portion 3 may be a rib-like land portion that is not partitioned by lateral grooves.

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

In this embodiment, at least one of the land portions, each block land portion 5 in the illustrated example, is provided with a plurality of first sipe units 60A each consisting of a pair of first sipes 6a and 6b (hereinafter referred to as one first sipe 6a and the other first sipe 6b, or simply referred to as the first sipes 6a and 6b) and a plurality of second sipe units 60B each consisting of a pair of second sipes 6c and 6d (hereinafter referred to as one second sipe 6c and the other second sipe 6d, or simply referred to as the second sipes 6c and 6d). In the example shown in FIG. 1, block land portions 52, 53, and 54 each have six first sipe units 60A and six second sipe units 60B, while block land portions 51 and 55 each have three first sipe units 60A and three second sipe units 60B.

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

The first sipe unit 60A and second sipe unit 60B in the tire 10 of this embodiment will be described in detail with reference to Figures 1, 2A, 2B, and 3. Figure 2A is a diagram for explaining the first sipe unit 60A, Figure 2B is a diagram for explaining the second sipe unit 60B, and Figure 3 is an enlarged view of a portion of Figure 1 for explaining the arrangement of the first sipe unit 60A and second sipe unit 60B, etc.

In the tire 10 of this embodiment, both ends of the first sipes 6a and 6b and the second sipes 6c and 6d all terminate within the block land portion 5. As shown in FIG. 1, both ends of the first sipe 6a and the other first sipe 6b that make up the first sipe unit 60A, and both ends of the second sipe 6c and the other second sipe 6d that make up the second sipe unit 60B all terminate within the block land portion 5.

2A , in the tire 10 of this embodiment, the first sipe 6a and the other first sipe 6b in the first sipe unit 60A are arranged opposite each other in the tire circumferential direction and each have a long side extending in the tire width direction. In this embodiment, the first sipe 6a and the other first sipe 6b in the first sipe unit 60A each have a long side extending at an angle with respect to the tire width direction so as to extend toward one side in the tire circumferential direction as they move toward one side in the tire width direction. More specifically, as shown in FIG. 2A , the first sipe 6a and the other first sipe 6b are spaced apart from each other and at least a portion (in this example, a portion) of each sipe is arranged opposite each other in the tire circumferential direction. Also, as shown in FIG. 2A , the first sipe 6a has a long side 61a extending at an angle with respect to the tire width direction so as to extend toward the tire circumferential direction CD1 as it moves from the tire width direction WD2 side toward the tire width direction WD1 side. The other first sipe 6b has a long side 61b that extends at an incline with respect to the tire width direction so as to move from the tire width direction WD2 side toward the tire width direction WD1 side toward the tire circumferential direction CD1 side. In this way, both the long sides 61a and 61b extend at an incline upward to the right on the page by inclining toward the tire circumferential direction CD1 side toward the tire width direction WD1 side.
Here, in this specification, "extending in the tire width direction" means extending with at least a tire width direction component. 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 inclined with respect to the tire width direction (i.e., at an inclination angle of more than 0° with respect to the tire width direction and inclined with respect to the tire width direction).
In the illustrated example, the long sides 61a and 61b have the same inclination angles θ1 and θ2 relative to the tire width direction, but may be inclined at different inclination angles.

One of the first sipes 6 a has a short side 62 a that extends from an end e1 on either side in the tire width direction of the long side 61 a (the tire width direction WD2 side in the illustrated example) toward the other first sipe 6 b. As shown in Fig. 2A , the short side 62 a extends toward the side where the one first sipe 6 a and the other first sipe 6 b face each other, and forms a bending angle θ3 with the long side 61 a.
The other first sipe 6b has a short side 62b that extends from an end e2 on the other side of the long side 61b in the tire width direction (the tire width direction WD1 side in the illustrated example) so as to approach the one first sipe 6a. As shown in Figure 2A, the short side 62b extends toward the side where the one first sipe 6a and the other first sipe 6b face each other, and forms a bending angle θ4 with the long side 61b.
In addition, in one first sipe 6a and the other first sipe 6b, of the ends on either side of the long sides 61a and 61b in the tire width direction, no short sides extend from the ends on the side where the above-mentioned short sides 62a and 62b are not provided.

As shown in FIG. 2B , in the tire 10 of this embodiment, one second sipe 6c and the other second sipe 6d in the second sipe unit 60B are arranged opposite each other in the tire circumferential direction and each have a long side extending in the tire width direction. In this embodiment, the one second sipe 6c and the other second sipe 6d in the second sipe unit 60B each have a long side extending at an angle with respect to the tire width direction so as to move toward one side in the tire width direction and toward the other side in the tire circumferential direction. More specifically, as shown in FIG. 2B , the one second sipe 6c and the other second sipe 6d are spaced apart from each other and at least a portion (in this example, a portion) of each second sipe 6c is arranged opposite each other in the tire circumferential direction. As shown in FIG. 2B , one second sipe 6c has a long side 61c extending at an angle with respect to the tire width direction so as to move from the tire width direction WD2 side toward the tire width direction WD1 side toward the tire circumferential direction CD2 side. The other second sipe 6d has a long side 61d that extends at an incline with respect to the tire width direction so as to move from the tire width direction WD2 side toward the tire width direction WD1 side toward the tire circumferential direction CD2 side. In this way, both the long sides 61c and 61d extend at an incline downward to the right on the page by inclining toward the tire circumferential direction CD2 side toward the tire width direction WD1 side.
In the illustrated example, the long sides 61c and 61d have the same inclination angles θ5 and θ6 relative to the tire width direction, but may be inclined at different inclination angles.

One of the second sipes 6c has a short side 62c that extends from an end e3 on either side of the long side 61c in the tire width direction (the tire width direction WD1 side in the illustrated example) so as to approach the other second sipe 6d. As shown in Fig. 2B , the short side 62c extends toward the side where the one second sipe 6c and the other second sipe 6d face each other, and forms a bending angle θ7 with the long side 61c.
The other second sipe 6d has a short side 62d that extends from an end e4 on the other side of the long side 61d in the tire width direction (the tire width direction WD2 side in the illustrated example) so as to approach one of the second sipes 6c. As shown in Figure 2B, the short side 62d extends toward the side where the one second sipe 6c and the other second sipe 6d face each other, and forms a bending angle θ8 with the long side 61d.
In addition, in one second sipe 6c and the other second sipe 6d, no short sides extend from the ends of either of the long sides 61c and 61d in the tire width direction on the side where the above-mentioned short sides 62c and 62d are not provided.

In the tire 10 of this embodiment, as shown in Figures 1 and 3, the first sipe unit 60A and the second sipe unit 60B are arranged offset from each other in the tire width direction. When viewed along the tire circumferential direction in a developed view of the tread surface 1, the first sipe unit 60A and the second sipe unit 60B are arranged with a phase difference in the tire width direction (i.e., they do not overlap at least partially in the tire width direction).

The following describes the effects of the tire configuration of this embodiment.
Both ends of one first sipe 6a, the other first sipe 6b, one second sipe 6c, and the other second sipe 6d each terminate within the land portion (in the block land portion 5 in this embodiment), preventing open ends of the sipes from being formed at the edge of the block land portion 5, and the land portions remain connected around the respective ends of the first sipe 6a, the first sipe 6b, the second sipe 6c, and the second sipe 6d, thereby increasing the rigidity of the block land portion compared to when the sipes are open to the edge of the block land portion. This suppresses deformation of the block land portion 5, preventing lift-up on the contact surface and increasing the actual contact area with the road surface, thereby improving grip performance on ice.
In this embodiment, the first sipes 6 a and 6 b, and the second sipes 6 c and 6 d are arranged opposite each other in the tire circumferential direction, and have long sides 61 a, 61 b, 61 c, and 61 d that extend at an angle relative to the tire width direction so as to extend toward one tire circumferential side or the other tire circumferential side as they approach one tire width direction. This allows the edge components of the long sides to not only fully exert braking force and driving force in the tire circumferential direction (front-to-rear direction), but also contribute to improving lateral grip performance in the tire width direction. In particular, by setting the inclination angles θ1, θ2, θ5, and θ6 to 45° or less, the tire width direction components of the long sides of the sipes become equal to or greater than the tire circumferential component, contributing to improving braking/driving force, which is the most important factor for safety.

Furthermore, in this embodiment, the first sipes 6a and 6b have short sides 62a and 62b extending from the long sides 61a and 61b, respectively, on opposite sides, and the second sipes 6c and 6d have short sides 62c and 62d extending from the long sides 61c and 61d, respectively, on opposite sides. As a result, when sipes are formed in a mold using thin metal plates (blades) during the tire 10 manufacturing process, the short sides support the blades against bending deformation that would cause the long sides to collapse, significantly increasing the bending rigidity of the blades, improving durability and tire productivity.

Additionally, in this embodiment, the first sipe unit 60A and the second sipe unit 60B are disposed offset from each other in the tire width direction. At this time, in the first sipe unit 60A and the second sipe unit 60B adjacent in the tire width direction, the long sides of the first sipe unit 60A and the second sipe unit 60B are inclined in opposite directions (as described above, both of the long sides 61a and 61b are inclined upward to the right on the paper surface in each drawing so as to move toward the tire width direction WD1 toward the tire circumferential direction CD1, and both of the long sides 61c and 61d are inclined downward to the right on the paper surface in each drawing so as to move toward the tire circumferential direction CD2 toward the tire width direction WD1). In this case, when an input is applied to the block land portion in the circumferential direction of the tire, a force that causes the first sipe unit 60A and the second sipe unit 60B to deform by collapsing (hereinafter also referred to as collapsing deformation) is generated in each of them according to the direction in which they extend, but the first sipe unit 60A and the second sipe unit 60B support each other's collapsing deformation and, as a whole, can increase the rigidity of the block land portion and improve grip performance on ice.
3, for example, when a tire circumferential input is applied to the block land portion 5 from the tire circumferential direction CD1 toward CD2, a force that causes the land portion adjacent to the first sipe unit 60A to deform so as to collapse toward the arrow X1 side is generated, and a force that causes the land portion adjacent to the second sipe unit 60B to deform so as to collapse toward the arrow X2 side is generated. At this time, the land portion near the first sipe unit 60A and the land portion near the second sipe unit 60B have long sides that are inclined in opposite directions, and therefore they mutually support the collapse deformation, thereby enabling the rigidity of the block land portion 5 to be increased.
In addition, if the long sides of the first sipe unit 60A and the second sipe unit 60B are all inclined in the same direction rather than in opposite directions, a force of collapse deformation in the same direction will be generated in the land portion near the first sipe unit 60A and the land portion near the second sipe unit 60B, and as the entire land portion deforms in the same direction, there is a risk that an unexpected force in the tire width direction will be generated as a reaction force; however, with the configuration of this embodiment, such a reaction force can be offset.

As described above, this embodiment increases land area rigidity (and thus actual contact area) while maintaining sipe density, i.e., it is possible to achieve both high land area rigidity and high-density sipe placement, thereby improving grip performance on ice.

In the tire 10 of this embodiment, as shown in Figures 1 and 3, the first sipe units 60A and the second sipe units 60B are each arranged adjacent to each other in the circumferential direction of the tire to form a first sipe unit row 7A and a second sipe unit row 7B, respectively, and it is preferable that the first sipe unit row 7A and the second sipe unit row 7B are arranged offset from each other in the width direction of the tire.
1 and 3, in the tire 10 of this embodiment, a plurality of first sipe units 60A and a plurality of second sipe units 60B are arranged adjacent to each other in the tire circumferential direction to form a first sipe unit row 7A and a second sipe unit row 7B. In Fig. 1, the row of a plurality of first sipe units 60A (three units in the illustrated example) arranged adjacent to each other in the tire circumferential direction and the row of a plurality of second sipe units 60B (three units in the illustrated example) arranged adjacent to each other in the tire circumferential direction are shown as the first sipe unit row 7A and the second sipe unit row 7B, respectively, as typical examples. In the first sipe unit row 7A, adjacent first sipe units 60A are spaced apart from each other and arranged so that at least a portion (in this example, all) of the first sipe units 60A face each other in the tire circumferential direction, while in the second sipe unit row 7B, adjacent second sipe units 60B are spaced apart from each other and arranged so that at least a portion (in this example, all) of the second sipe units 60B face each other in the tire circumferential direction. The first sipe unit row 7A and the second sipe unit row 7B are offset from each other in the tire width direction. As shown in FIGS. 1 and 3 , the first sipe unit row 7A and the second sipe unit row 7B are arranged so that they are out of phase with each other in the tire width direction (i.e., they do not overlap at least partially in the tire width direction) when viewed along the tire circumferential direction in a developed view of the tread surface 1.
According to this configuration, the land portion near the first sipe units 60A constituting the first sipe unit row 7A and the land portion near the second sipe units 60B constituting the second sipe unit row 7B have long sides that slope in opposite directions, which allow them to mutually support the collapse deformation and more sufficiently increase the rigidity of the block land portion 5. In addition, if the long sides of the first sipe units 60A constituting the first sipe unit row 7A and the long sides of the second sipe units 60B constituting the second sipe unit row 7B were all sloped in the same direction, the entire land portion would deform in the same direction, which could result in an unexpected force in the tire width direction as a reaction force, but according to the configuration of this embodiment, such a reaction force can be more effectively offset.

The following describes preferred configurations and modifications of the tire 10 of this embodiment.

In the tire 10 of this embodiment, the sipe depth of each of the first sipes 6a, the first sipes 6b, the second sipes 6c, and the second sipes 6d is not particularly limited, but from the perspective of more effectively improving grip performance on ice, it is preferably 3 mm or more, and may be, for example, 10 mm or less.

In the tire 10 of this embodiment, in the first sipe unit 60A, the long sides and short sides of one first sipe 6a and the other first sipe 6b preferably extend parallel to each other. As shown in Fig. 2A, 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, the one first sipe 6a and the other first sipe 6b are preferably offset from each other in the tire width direction.
In the tire 10 of this embodiment, it is preferable that the long sides and short sides of the second sipe unit 60B of one second sipe 6c and the other second sipe 6d extend parallel to each other. As shown in Fig. 2B , the long sides 61c and 61d extend parallel to each other, and the short sides 62c and 62d extend parallel to each other. In addition, in the tire 10 of this embodiment, it is preferable that the one second sipe 6c and the other second sipe 6d are offset in the tire width direction.
In Fig. 2A, the first sipes 6a and 6b are arranged so that portions of the first sipes 6a and 6b overlap with each other in the tire width direction and are out of phase with each other in the tire width direction (i.e., they do not overlap with each other in the tire width direction) when viewed along the tire circumferential direction in a developed view of the tread surface 1. In Fig. 2B, the second sipes 6c and 6d are arranged so that portions of the sipes 6c and 6d overlap with each other in the tire width direction and are out of phase with each other in the tire width direction (i.e., they do not overlap with each other in the tire width direction) when viewed along the tire circumferential direction in a developed view of the tread surface 1.
By arranging the long sides and short sides of the first sipes 6a and the first sipes 6b parallel to each other, and by arranging the long sides and short sides of the second sipes 6c and the second sipes 6d parallel to each other, the distances between the long sides and short sides of each of the first sipe units 60A and the second sipe units 60B in the tire circumferential direction and the tire width direction can be made constant.Therefore, when arranging multiple first sipe units 60A and multiple second sipe units 60B adjacent to each other in the tire circumferential direction in the block land portion 5, it is easy to arrange the first sipe units 60A and the second sipe units 60B uniformly and with high density without forming unnecessary gaps.
In addition, by offsetting one first sipe 6a from the other first sipe 6b, and one second sipe 6c from the other second sipe 6d in the tire width direction, when each of the first sipe unit 60A and the second sipe unit 60B is viewed along the tire circumferential direction in a developed view of the tread surface 1, the sipes are present over a wider range in the tire width direction than when one sipe in each of the first sipe unit 60A and the second sipe unit 60B is not offset from the other sipe. This makes it possible to fully exert braking force and driving force due to the edge components over a wider range in the tire width direction, and to uniformize the ground contact pressure distribution of the block land portion 5.

In the tire 10 of this embodiment, the long sides 61a and 61b of the first sipes 6a and 6b respectively extend at inclination angles θ1 and θ2 with respect to the tire width direction, preferably from 0° to 45°, and more preferably from more than 0° to less than 45°. The long sides 61c and 61d of the second sipes 6c and 6d respectively extend at inclination angles θ5 and θ6 with respect to the tire width direction, preferably from 0° to 45°, and more preferably from more than 0° to less than 45°.
By setting the inclination angles θ1, θ2, θ5, and θ6 to be between 0° and 45°, respectively, the braking force and driving force in the circumferential direction (front-to-rear direction) of the tire due to the edge components of the long sides are sufficiently exerted. By setting the inclination angles θ1, θ2, θ5, and θ6 to be greater than 0°, an edge effect is also obtained in the tire width direction, and by setting the inclination angles θ1, θ2, θ5, and θ6 to be less than 45°, the braking force and driving force in the circumferential direction (front-to-rear direction) of the tire due to the edge components of the long sides are more sufficiently exerted.

In the tire 10 of this embodiment, in the first sipe unit 60A, it is preferable that the angle θ3, which is the angle between the long side 61a and the short side 62a on the side where one first sipe 6a and the other first sipe 6b face each other, and the angle θ4, which is the angle between the long side 61b and the short side 62b on the side where one first sipe 6a and the other first sipe 6b face each other, are 90° or greater. In addition, in the second sipe unit 60B, it is preferable that the angle θ7, which is the angle between the long side 61c and the short side 62c on the side where one second sipe 6c and the other second sipe 6d face each other, and the angle θ8, which is the angle between the long side 61d and the short side 62d on the side where one second sipe 6c and the other second sipe 6d face each other, are 90° or greater.
According to this configuration, when sipes are formed in a mold using a blade during the manufacturing process of the tire 10, the short sides provide more effective support against bending deformation that would cause the long sides of the blade to collapse, further increasing the bending rigidity of the blade, more effectively improving durability and improving tire productivity. Also, by setting the angles θ3, θ4, θ7, and θ8 to 90° or greater, it is possible to prevent the land portions near the vertices of the long and short sides from forming acute corners, i.e., preventing the formation of localized low rigidity portions, thereby suppressing deformation around those portions, preventing an increase in contact pressure step, and more effectively exerting braking force and driving force in the circumferential direction of the tire.
Furthermore, the angles θ3, θ4, θ7, and θ8 are more preferably 150° or less. By setting the angles θ3, θ4, θ7, and θ8 to 150° or less, a more appropriate bend is formed between the short sides and the long sides than when the angles exceed 150°, and the durability of the blades that form the sipes during tire manufacturing can be improved.

1 , 2A, and 2B , in the tire 10 of this embodiment, it is preferable that in the first sipe unit 60A, the short sides 62a and 62b of one first sipe 6a and the other first sipe 6b extend along the tire circumferential direction, respectively, and that in the second sipe unit 60B, the short sides 62c and 62d of one second sipe 6c and the other second sipe 6d extend along the tire circumferential direction, respectively. Note that "extending along the tire circumferential direction" includes cases where the sipes are parallel to the tire circumferential direction and cases where the sipes are inclined at an extremely small angle relative to the tire circumferential direction (e.g., an inclination angle of 5° or less relative to the tire circumferential direction). This configuration allows for more efficient arrangement of sipes that can exert braking and driving forces in response to inputs in the tire circumferential direction. Furthermore, because the direction of the short sides is substantially aligned with the input direction of the braking/driving forces, the block land portions are not divided in the input direction, and a decrease in rigidity of the land portions around the short sides can be more effectively suppressed. Furthermore, with this configuration, by removing the water film on the ice surface, the water that has accumulated on the long sides of the sipes can be efficiently guided by the short sides of the sipes, which extend along the circumferential direction of the tire and are located at the ends of the long sides, in the circumferential direction of the tire, which is the sliding direction during braking, and this promotes drainage.
In addition, when the short sides 62a and 62b extend along the tire circumferential direction, from the viewpoints of forming a moderate bend between the short sides and the long sides, more effectively improving the durability of the blades that form the sipes during tire manufacturing, and ensuring that the edge components of the long sides fully exert the braking and driving forces in the tire circumferential direction (front-to-rear direction), the angles θ3 and θ4 are preferably greater than 90° and less than 135°. Similarly, when the short sides 62c and 62d extend along the tire circumferential direction, from the viewpoints of forming a moderate bend between the short sides and the long sides, more effectively improving the durability of the blades that form the sipes during tire manufacturing, and ensuring that the edge components of the long sides fully exert the braking and driving forces in the tire circumferential direction (front-to-rear direction), the angles θ7 and θ8 are preferably greater than 90° and less than 135°. As described above, by setting the inclination angle of the long sides relative to the tire width direction to 0 to 45°, the braking and driving performance, which is the most important factor for safety, can be maximized. To align the short sides generally in the circumferential direction while maintaining this angle, the bending angle between the long sides and the short sides needs to be 90 to 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 the angles θ3 and θ4 are 120°.

1, 2A, and 2B, in the tire 10 of this embodiment, it is preferable that in the first sipe unit 60A, one first sipe 6a and the other first sipe 6b are congruent with each other, and in the second sipe unit 60B, one second sipe 6c and the other second sipe 6d are congruent with each other. With this configuration, when arranging a plurality of first sipe units 60A and a plurality of second sipe units 60B adjacent to each other in the tire circumferential direction in the block land portion 5, they can be arranged uniformly and with high density.
Also, for the same reason, in the tire 10 of this embodiment, as shown in FIG. 1, it is preferable that one first sipe 6a, the other first sipe 6b, one second sipe 6c, and the other second sipe 6b are all congruent with one another.
As shown in Figures 1 and 3, all sipes included in the first sipe unit row 7A may be congruent, and all sipes included in the second sipe unit row 7B may be congruent, or all sipes included in the first sipe unit row 7A and the second sipe unit row 7B may be congruent.
Here, "congruent" includes mirror image congruence, and refers to complete overlapping with each other through translation, rotation and/or line symmetric movement when viewed from the tread surface.

In the tire 10 of this embodiment, in the first sipe unit 60A, it is preferable that the ratio of the length along the extension direction of the long sides 61a and 61b to the length along the extension direction of the short sides 62a and 62b of one first sipe 6a and the other first sipe 6b is 1 to 15, and in the second sipe unit 60B, it is preferable that the ratio of the length along the extension direction of the long sides 61c and 61d to the length along the extension direction of the short sides 62c and 62d of one second sipe 6c and the other second sipe 6d is 1 to 15. In Figure 2A, it is preferable that the ratio of the length L2 along the extension direction of the long side 61a to the length L1 along the extension direction of the short side 62a is 1 to 15, and the ratio of the length L4 along the extension direction of the long side 61b to the length L3 along the extension direction of the short side 62b is 1 to 15.In Figure 2B, it is preferable that the ratio of the length L8 along the extension direction of the long side 61c to the length L7 along the extension direction of the short side 62c is 1 to 15, and the ratio of the length L10 along the extension direction of the long side 61d to the length L9 along the extension direction of the short side 62d is 1 to 15.
With this configuration, since the ratio of the length of the long side to the short side is 1 or more, an excessive decrease in sipe density or an excessive decrease in land portion rigidity can be suppressed, and since the ratio of the length of the long side to the short side is 15 or less, the durability of the blades that form the sipes during tire manufacturing can be improved.

In the tire 10 of this embodiment, the lengths L2 and L4 of the first sipe unit 60A along the direction of extension of the long sides 61a and 61b, and the lengths L8 and L10 of the second sipe unit 60B along the direction of extension of the long sides 61c and 61d are not particularly limited, but from the perspective of maintaining the rigidity of the block land portion 5 while fully demonstrating the tire's grip performance on ice and from the perspective of enabling application to a variety of tires, it is preferable that they each be between 3 and 15 mm.

In addition, in the tire 10 of this embodiment, the values of lengths L1 and L3 along the extension direction of the short sides 62a and 62b in the first sipe unit 60A and lengths L7 and L9 along the extension direction of the short sides 62c and 62d in the second sipe unit 60B are not particularly limited, but from the perspective 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 values as lengths L2 and L4 along the extension direction of the long sides 61a and 61b and lengths L8 and L10 along the extension direction of the long sides 61c and 61d, respectively.

In addition, in the tire 10 of this embodiment, it is preferable that the ratio of the tire circumferential length L6 of the first sipe unit 60A along the tire circumferential direction to the tire width direction length L5 along the tire width direction is 0.1 to 2.6, and the ratio of the tire circumferential length L12 of the second sipe unit 60B along the tire circumferential direction to the tire width direction length L11 along the tire width direction is 0.1 to 2.6.
Here, the "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 FIG. 2A refers to the distance between the end of the center line C1 of the first sipe 6a on the tire width direction WD2 side and the end of the center line C2 of the first sipe 6b on the tire width direction WD1 side, and in FIG. 2B refers to the distance between the end of the center line C3 of the second sipe 6c on the tire width direction WD1 side and the end of the center line C4 of the second sipe 6d on the tire width direction WD2 side. The "tire circumferential length along the tire circumferential direction" refers to the tire circumferential length along a straight line parallel to the tire circumferential direction. In FIG. 2A , this refers to the distance between the end of the first sipe 6a on the tire circumferential CD1 side of the center line C1 and the end of the first sipe 6b on the tire circumferential CD2 side of the center line C2. In FIG. 2B , this refers to the distance between the end of the second sipe 6c on the tire circumferential CD1 side of the center line C3 and the end of the second sipe 6d on the tire circumferential CD2 side of the center line C4. When the ratio is 0.1 or greater, the circumferential distance between the sipes is not too narrow, thereby ensuring sufficient block rigidity. Furthermore, when the ratio is 2.6 or less, the inclination angles θ1 and θ2 of the long sides 61a and 61b are not excessively large, and the tire widthwise lengths of the long sides 61a and 61b are not too short, thereby achieving a more sufficient effect on braking/driving force.

In the tire 10 of this embodiment, as shown in FIG. 3 , in a plurality of (three in the illustrated example) first sipe units 60A in the first sipe unit row 7A, the short sides 62a of a plurality of (all in the present example) one first sipes 6a extend on the same straight line along the tire circumferential direction (on a virtual line Y1 extending along the tire circumferential direction in FIG. 3 ), and the short sides 62b of a plurality of (all in the present example) other first sipes 6b extend on the same straight line along the tire circumferential direction (on a virtual line Y1 extending along the tire circumferential direction in FIG. 3 ). It is preferable that, in a plurality (three in this example) of second sipe units 60B in the second sipe unit row 7B, the short sides 62d of a plurality (all in this example) of the other second sipes 6d extend on the same straight line along the tire circumferential direction (on the imaginary line Y2 extending along the tire circumferential direction in FIG. 3), and the short sides 62c of a plurality (all in this example) of the one second sipes 6c extend on the same straight line along the tire circumferential direction (on the imaginary line Y3 extending along the tire circumferential direction in FIG. 3).
With this configuration, the phase in the tire width direction of each of the first sipe units 60A and second sipe units 60B, which are arranged adjacent to each other in the tire circumferential direction, is aligned, making it easy to arrange multiple first sipe units 60A and second sipe units 60B uniformly and with high density in the block land portion 5 without forming unnecessary gaps.

In the tire 10 of this embodiment, it is preferable that a plurality of first sipe units 60A and a plurality of second sipe units 60B are arranged adjacent to each other at regular intervals in the tire circumferential direction in each of the first sipe unit row 7A and the second sipe unit row 7B. Regarding the spacing between the first sipe units 60A and the spacing between the second sipe units 60B, the configurations of the first sipe unit row 7A and the second sipe unit row 7B will be described below using the first sipe unit row 7A as a typical example.
3, all of the long sides included in the first sipe unit row 7A extend parallel to each other. The other first sipe 6b of the first sipe unit 60A is disposed at a position shifted in phase with respect to the one first sipe 6a by an offset s in the tire width direction and an offset q in the tire circumferential direction.
In the first sipe unit row 7A, the first sipe units 60A are repeatedly arranged at a pitch p in the tire circumferential direction. Here, if the distance in the tire circumferential direction between adjacent first sipe units 60A in the tire circumferential direction is defined as the inter-unit distance r, the inter-unit distance r is expressed as r = p - q. In particular, when the pitch p between adjacent first sipe units 60A in the tire circumferential direction and the tire circumferential offset q between the first sipes 6a and 6b constituting the first sipe unit 60A are q = p/2, then r = q (inter-unit distance r = tire circumferential offset q), and all sipes are arranged at equal intervals in the tire circumferential direction within the first sipe unit 60A and between the first sipe units 60A. Therefore, preferably, q is set in the range of (p/2) × 0.8 to (p/2) × 1.2, and more preferably, q is set to p/2, thereby making the sipe density in the tire circumferential direction in the block land portion 5 uniform. This allows the contact surface of the block land portion 5 to come into more uniform contact with the road surface, making the distribution of contact pressure applied to the contact surface of the block land portion 5 more uniform, and increasing the contact area of the tire 10.

In addition, in the tire 10 of this embodiment, it is preferable that the first sipe units 60A and the second sipe units 60B are arranged in plurality at regular intervals in the tire circumferential direction in the first sipe unit row 7A and the second sipe unit row 7B. As shown in Figure 3, the first sipe unit row 7A (more specifically, the first sipe units 60A in the first sipe unit 7A) and the second sipe unit row 7B (more specifically, the second sipe units 60B in the second sipe unit row 7B) are arranged at positions that are shifted in phase from each other by an offset u in the tire circumferential direction. When the offset u and the pitch p between circumferentially adjacent first sipe units 60A (the pitch between circumferentially adjacent second sipe units 60B is also referred to as pitch p) are u = p/2, the first sipe units 60A and the second sipe units 60B are aligned at equal intervals in the tire circumferential direction in the first sipe unit row 7A and the second sipe unit row 7B. Therefore, the offset u is preferably set in the range of (p/2) × 0.8 to (p/2) × 1.2, and more preferably, u is set to p/2, thereby achieving a uniform sipe density in the tire circumferential direction in the block land portion 5. This allows the contact surface of the block land portion 5 to contact the road surface more uniformly, uniforming the distribution of ground pressure applied to the contact surface of the block land portion 5 and increasing the contact area of the tire 10.

3 and 4, the distance in the tire width direction between the first sipe unit row 7A and the second sipe unit row 7B that are adjacent in the tire width direction is indicated by v.
The offset u in the tire circumferential direction and the interval v in the tire width direction may each be set to an arbitrary value.

Here, as described above, when the offset in the tire width direction between a pair of first sipes and a pair of second sipes in each sipe unit is s (s > 0), the interval v is preferably −s to s. Note that when the interval v is a negative value (for example, −s), this means that the first sipe unit row 7A and the second sipe unit row 7B overlap in the tire width direction by an amount equal to the absolute value of v when viewed along the tire circumferential direction.
When v is equal to or greater than -s, the sipes arranged in the land portion do not become too dense, and sufficient rigidity of the land portion can be ensured. When v is a positive value, the circumferentially continuous region of the land portion and therefore more sufficient rigidity of the land portion can be ensured. When v is equal to or less than s, sufficient sipe density can be ensured in the land portion.
In particular, when v = 0, adjacent sipe unit rows are arranged continuously in the tire width direction, preventing the occurrence of blank areas where no sipes exist between the sipe unit rows. Furthermore, when v = 0, the short sides of adjacent sipe unit rows can be aligned in a single straight line along the tire circumferential direction, thereby synergistically enhancing the effect of promoting drainage. Therefore, it is particularly preferable to set v = 0.

FIG. 4 is a diagram for explaining an arrangement of the first sipe unit 60A and the second sipe unit 60B that is different from that shown in FIG.
It is preferable that the circumferential end of the short side of one (or the other) sipe in each sipe unit does not protrude in the tire circumferential input direction beyond the circumferential end of the long side of the other (or one) sipe. More specifically, for example, in Fig. 4, the end E1 on the circumferential CD1 side of the short side 62d of the second sipe 6d protrudes toward the tire circumferential CD1 side beyond the end E2 on the circumferential CD1 side of the long side 61c of the second sipe 6c. However, from the viewpoint of ensuring a wide area surrounded by the dotted line in Fig. 4 and further improving land portion rigidity in the event of an input from the circumferential CD1 side toward the circumferential CD2 side of the tire, it is preferable that the end E1 does not protrude toward the tire circumferential CD1 side beyond the end E2.

More preferably, in the tire 10 of this embodiment, as shown in FIG. 3, in the first sipe unit row 7A and the second sipe unit row 7B adjacent in the tire width direction, the short side 62a of one first sipe 6a or the short side 62b of the other first sipe 6b of the multiple first sipe units 60A in the first sipe unit row 7A that is offset in the tire width direction and that faces the second sipe unit row 7B, and the short side 62c of one second sipe 6c or the short side 62d of the other second sipe 6d of the multiple second sipe units 60B in the second sipe unit row 7B that is offset in the tire width direction and that faces the first sipe unit row 7A extend on the same straight line along the tire circumferential direction. 3, of the short sides included in the first sipe unit 60A, a short side 62b on the second sipe unit row 7B side and a short side 62d of the short sides included in the second sipe unit 60B on the first sipe unit row 7A side extend on the same straight line along the tire circumferential direction (in FIG. 3, on an imaginary line Y2 extending along the tire circumferential direction). With this configuration, the distance v in the tire width direction between the first sipe unit row 7A and the second sipe unit row 7B is v=0, and when the first sipe unit 60A and the second sipe unit 60B are viewed along the tire circumferential direction in a developed view of the tread surface 1, sipes are present across the entire width in the tire width direction from the end of the first sipe unit row 7A on the tire width direction WD2 side to the end of the second sipe unit row 7B on the tire width direction WD1 side. This allows the first sipe unit 60A and the second sipe unit 60B to function as a single unit, and the braking and driving forces from the edge components can be fully exerted across the entire width of the tire width direction region where the first sipe unit row 7A and the second sipe unit row 7B are arranged, while also achieving a more uniform contact pressure distribution in the block land portion 5. In addition, the region where the land portions are continuous around the short sides can be more fully secured.

In the tire 10 of this embodiment, there are no particular limitations on the number and density of the first sipe units 60A and second sipe units 60B arranged in each block land portion 5. As described above, in the example shown in FIG. 1, six first sipe units 60A and six second sipe units 60B are arranged in each of the block land portions 52, 53, and 54, and three first sipe units 60A and three second sipe units 60B are arranged in each of the block land portions 51 and 55.

The total number of first sipes 6a and 6b constituting the first sipe unit 60A and second sipes 6c and 6d constituting the second sipe unit 60B arranged in the block land portion 5 may be determined, for example, based on the sipe density SD described below.

A method for calculating the sipe density SD will be described below. Figure 5 is an enlarged view of one of the block land portions 53 in Figure 1. As shown in Figure 5, when the block land portion 53 in Figure 1 is taken as a typical example of the block land portion 5, the total number of first sipes 6a, first sipes 6b, second sipes 6c, and second sipes 6d in the block land portion 5 is n (pieces), the tire width direction length of each of the first sipes 6a, first sipes 6b, second sipes 6c, and second sipes 6d is d (mm) (in Figure 5, the tire width direction length of sipe 6a is shown as d), and the sipe depth of the sipes 6a, 6b, 6c, and 6d is h (mm), where d x h can be, for example, 150 (mm ² ) or less. Furthermore, when the maximum tire width direction length of the block land portion 5 is BW (mm), the equivalent number of sipes N is expressed as d x n/BW. Here, the number N of equivalent sipes is the number of transverse sipes (equivalent sipes) that completely cross the block land portion 5 when the first sipes 6a, 6b, 6c, and 6d of this embodiment are converted into transverse sipes (equivalent sipes) that are arranged so as to completely cross the block land portion 5. Furthermore, if the tire circumferential length of the equivalent land portion obtained by dividing the outer contour area ( ^mm2 ) of the block land portion 5 by the BW (mm) is BL (mm), the average sipe spacing is expressed as BL/(N+1). Here, the average sipe spacing is the spacing of the equivalent sipes in the tire circumferential direction in the block land portion 5 when the first sipes 6a, 6b, 6c, and 6d of this embodiment are converted into 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 n of sipes in a block land portion, the length d of each sipe in the tire width direction, the maximum length BW of the block land portion in the tire width direction, and the outer contour area of the block land portion are values measured in a developed view of the tread surface. The "outer contour area" of a block land portion refers to the area surrounded by the outer contour of the block land portion in a developed view of the tread surface, and therefore, even if non-contacting parts such as sipes, small holes, narrow grooves, etc. are located within the block land portion, this area does not exclude the areas of the sipes, small holes, narrow grooves, etc.

For example, the block land portion 5 may have multiple first sipes 6a, first sipes 6b, second sipes 6c, and second sipes 6d arranged so that the sipe density SD is 0.15 or greater. This increases the sipe density while minimizing a decrease in the rigidity of the land portion, thereby more effectively improving the tire's grip performance on ice.

The following describes examples of the present invention, but the present invention is not limited to these examples.

The effect of suppressing lift-up in the contact patch of test tires 1 to 6 (Comparative Examples 1 to 3 and Examples 1 to 3) was calculated using the finite element method (FEM). Each test tire had block land portions shown in Table 1 and Figures 6(a) to 6(f) on the tread surface. The results for the comparative examples and examples shown in Table 1 and Figure 6 are shown in a graph in Figure 7. As shown in Figure 7, the horizontal axis of the graph represents block rigidity (N/mm), and the vertical axis of the graph represents actual contact patch area ( ^mm2 ) under shear.
The FEM prediction calculation was performed under the condition that a vertical load was applied which was the outer contour area of the land portion of the block multiplied by the standard ground contact pressure of 230 kPa for passenger car tires, and the block rigidity and ground contact area were evaluated.
For block rigidity, the shear input value in the circumferential direction of the tire was determined when the lateral displacement in the same direction was 1 mm, and for actual contact area, the remaining contact area in a state where partial lift-up occurred when the shear input in the circumferential direction of the tire was 0.3 times the above-mentioned vertical load was determined.
According to the results in Figure 7, even if the number of sipes and therefore the sipe density are the same (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 as a result, the effect of suppressing lift-up on the contact surface of the block land portion is greater, thereby improving grip performance on ice.

The pneumatic tire according to the present invention can be used for any type of pneumatic tire, but is preferably used for passenger car tires or truck/bus tires, and more preferably used for winter passenger car tires or winter truck/bus tires.

1: Tread surface, 2, 2a, 2b, 2c, 2d: Circumferential main grooves, 3, 3a, 3b, 3c, 3d, 3e: Land portions, 4, 41, 42, 43, 44, 45: Lateral grooves, 5, 51, 52, 53, 54, 55: Block land portions, 6a: First sipe (one of the first sipes), 6b: First sipe (the other of the first sipes), 6c: Second sipe (one of the second sipes), 6d: Second sipe (the other of the second sipes), 7A: First sipe unit row, 7B: Second sipe unit row, 10: Tire, 60A: First sipe unit, 60B: Second sipe unit, 61a, 61b, 61c, 61d: Long sides, 62a, 62b, 62c, 62d: Short sides, e1, e2, e3, e4: Edges; E1, E2: Edges; C1, C2: Centerline; WD1, WD2: Tire Width Direction; CD1, CD2: Tire Circumferential Direction; TE: Tread Edge; Y1, Y2, Y3: Virtual Line; d: Sipe Width Length; s: Tire Width Offset; p: Tire Circumferential Pitch of Sipe Units; q: Tire Circumferential Offset; u: Tire Circumferential Offset of Adjacent Sipe Unit Rows in the Tire Width Direction; v: Tire Width Distance Between Adjacent Sipe Unit Rows in the Tire Width Direction; r: Distance Between Adjacent Sipe Unit Rows in the Tire Width Direction

Claims (10)

A tire having at least one land portion on a tread surface of the tire,
a first sipe unit consisting of a pair of first sipes and a second sipe unit consisting of a pair of second sipes are arranged in at least one of the land portions,
Both ends of each of the first sipes and the second sipes terminate within the land portion,
one first sipe and the other first sipe constituting the pair of first sipes in the first sipe unit are arranged opposite to each other in the tire circumferential direction, and each has a long side extending at an angle with respect to the tire width direction so as to extend toward one side in the tire circumferential direction as it approaches that side in the tire width direction,
the one first sipe has a short side extending from an end of the long side on either side in the tire width direction so as to approach the other first sipe side,
the other first sipe has a short side extending from the other end of the long side in the tire width direction so as to approach the one first sipe side,
one second sipe and the other second sipe constituting the pair of second sipes in the second sipe unit are arranged opposite to each other in the tire circumferential direction, and each has a long side extending at an angle with respect to the tire width direction so as to extend toward one side in the tire width direction and toward the other side in the tire circumferential direction,
the one second sipe has a short side extending from an end of the long side on either side in the tire width direction so as to approach the other second sipe side,
the other second sipe has a short side extending from the other end of the long side in the tire width direction so as to approach the one second sipe side,
The tire, wherein the first sipe unit and the second sipe unit are disposed offset from each other in the tire width direction. The tire described in claim 1, wherein the first sipe units and the second sipe units are arranged adjacently in the tire circumferential direction to form a first sipe unit row and a second sipe unit row, respectively, and the first sipe unit row and the second sipe unit row are offset from each other in the tire width direction. In the first sipe unit row, in the first sipe units, the short sides of the first sipes of the first sipes extend on the same straight line along the tire circumferential direction, and the short sides of the other first sipes extend on the same straight line along the tire circumferential direction,
3. The tire according to claim 2, wherein, in the plurality of second sipe units within the second sipe unit row, the short sides of the plurality of one second sipes extend on the same straight line along the tire circumferential direction, and the short sides of the plurality of other second sipes extend on the same straight line along the tire circumferential direction. In the first sipe unit row and the second sipe unit row adjacent to each other in the tire width direction,
Of the short sides of the one first sipe or the short sides of the other first sipe of the plurality of first sipe units in the first sipe unit row, the short side arranged on the second sipe unit row side;
4. The tire according to claim 2, wherein, of the short sides of the one second sipe or the short sides of the other second sipe of the plurality of second sipe units in the second sipe unit row, the short side arranged on the first sipe unit row side extends on the same straight line along the tire circumferential direction. In the first sipe unit, the short sides of the one first sipe and the other first sipe extend along the tire circumferential direction,
The tire according to claim 1 , wherein in the second sipe unit, the short sides of the one second sipe and the other second sipe each extend along the tire circumferential direction. In the first sipe unit, the long sides of the one first sipe and the short sides of the other first sipe extend parallel to each other, and the one first sipe and the other first sipe are offset in the tire width direction,
The tire according to any one of claims 1 to 5, wherein in the second sipe unit, the long sides of the one second sipe and the short sides of the other second sipe extend parallel to each other, and the one second sipe and the other second sipe are arranged offset in the tire width direction. In the first sipe unit, the one first sipe and the other first sipe each have an angle formed by the long side and the short side on a side where the one first sipe and the other first sipe face each other of 90° or more,
The tire according to any one of claims 1 to 6, wherein in the second sipe unit, an angle formed by the long side and the short side of each of the one second sipe and the other second sipe on the side where the one second sipe and the other second sipe face each other is 90° or more. In the first sipe unit, the one first sipe and the other first sipe are congruent with each other,
The tire according to any one of claims 1 to 7, wherein in the second sipe unit, the one second sipe and the other second sipe are congruent with each other. In the first sipe unit, the one first sipe and the other first sipe each have a ratio of a length along the extension direction of the long side to a length along the extension direction of the short side of the one first sipe and the other first sipe being 1 to 15,
9. The tire according to claim 1, wherein in the second sipe unit, the ratio of the length along the extension direction of the long side to the length along the extension direction of the short side of each of the one second sipe and the other second sipe is 1 to 15. the first sipe unit has a ratio of a tire circumferential length along the tire circumferential direction to a tire widthwise length along the tire width direction of 0.1 to 2.6;
The tire according to any one of claims 1 to 9, wherein the second sipe unit has a ratio of a tire circumferential length along the tire circumferential direction to a tire widthwise length along the tire width direction of 0.1 to 2.6.