WO2011125293A1

WO2011125293A1 - Pneumatic tire

Info

Publication number: WO2011125293A1
Application number: PCT/JP2011/001624
Authority: WO
Inventors: 加地　与志男
Original assignee: 株式会社ブリヂストン
Priority date: 2010-04-02
Filing date: 2011-03-18
Publication date: 2011-10-13
Also published as: JP2011218830A; JP5519378B2

Abstract

Disclosed is a pneumatic tire in which a block is divided into a block piece that increases the ground contact area and a block piece that increases the edge pressure. In addition, at least one sipe in the block is a curved three-dimensional sipe.

Description

Pneumatic tire

The present invention relates to a pneumatic tire having a plurality of sipes on the tread surface of the tire and particularly improving the braking performance on ice.

Conventionally, in winter pneumatic tires, sipes extending in the tread width direction have been added to the tread pattern blocks and ribs (hereinafter collectively referred to as blocks) in order to improve acceleration and braking performance when starting on ice. It has been done.

In particular, as a prior art for improving the braking performance on ice, Patent Document 1 describes a pneumatic tire characterized by a twisted shape of small blocks at both ends of the block.
In this pneumatic tire, the small blocks at both ends of the block generate rotational forces in opposite directions when compressed by the pressure from the road surface. For this reason, even when the number of sipes is increased, it is possible to suppress the collapse of the small blocks during the braking drive. Thereby, the reduction | decrease in a contact area can be suppressed.

Japanese Patent Laid-Open No. 11-208222

When considering improvement of the friction characteristics on the ice of the tire, it is necessary to increase both the “contact area between the block and ice” and the “force for digging ice by the edge of the block”.
However, in the pneumatic tire described above, it is possible to suppress the contact area decrease by suppressing the collapse of the block, but the edge pressure for each small block divided by the sipe is decreased.
For this reason, the effect of improving the performance on ice due to the addition of sipe cannot be sufficiently obtained, so there is room for improvement on the performance on ice.

Accordingly, an object of the present invention is to provide a pneumatic tire that solves the above-described problems and has the contradictory characteristics of “increase in contact area” and “increase in edge pressure” to further improve the performance on ice. There is.

The inventor conducted extensive research on a tire that can achieve both “increase in contact area” and “increase in edge pressure”.
As a result, the block is divided into a block piece responsible for increasing the contact area and a block piece responsible for increasing the edge pressure, and by sharing the role, the above problem can be solved and the on-ice performance of the tire can be improved. I got new knowledge of what I can do.
Furthermore, the inventor uses a bent three-dimensional sipe for at least one of the sipe of the block, thereby preventing the block piece from collapsing against any direction of input from the road surface and suppressing a reduction in the contact area. As a result, the inventors have obtained a new finding that the on-ice performance of the tire can be further improved.

The present invention is based on the above findings, and the gist thereof is as follows.
(1) A plurality of blocks are defined on the tread surface of the tire by a plurality of circumferential grooves extending in the tread circumferential direction and a plurality of width grooves extending in the tread width direction, and a plurality of blocks extending in the tread width direction are formed on the blocks. A pneumatic tire with sipe,
The block is divided into a plurality of block pieces by the sipe, and a first block piece whose width in the tread circumferential direction of the block piece gradually decreases toward the tread surface, and a second block that gradually increases toward the tread surface. Having at least one set in which the pieces are arranged next to each other,
The width in the tread circumferential direction at least on the tread surface of the first block piece gradually decreases from the end of the block in the tread width direction toward the center, and the at least the tread surface of the second block piece. The width in the tread circumferential direction gradually increases from the end of the block in the tread width direction toward the center,
At least one of the sipe is a three-dimensional sipe that extends while being bent in the tire width direction and is bent in the tire radial direction.

(2) The width in the tread circumferential direction of the first block piece gradually decreases from the radially inner side to the outer side of the tire, and then gradually decreases.
The pneumatic tire according to (1), wherein the width of the second block piece in the circumferential direction of the tread gradually increases after gradually decreasing from the radially inner side to the outer side of the tire.

(3) The pneumatic tire according to (1) or (2), wherein at least one of the sipes at both ends in the tire circumferential direction of the block is the bent three-dimensional sipe.

(4) The pneumatic tire according to any one of (1) to (3), wherein sipes at both ends of the block in the tire circumferential direction are the bent three-dimensional sipes.

(5) The pneumatic tire according to any one of (1) to (4), wherein the bent three-dimensional sipe is provided at both ends in the tire circumferential direction and at a center portion in the tire circumferential direction.

(6) A ratio s1 between a tire circumferential direction width s1 of the second block piece and a tire circumferential direction width s2 of the third block piece at a tire width direction central portion of the tire tread surface. / s2
1.0 ≦ s1 / s2 ≦ 1.6
And in the tire width direction end of the block on the tread surface of the tire, a tire circumferential direction width t1 of the second block piece, and a tire circumferential direction width t2 of the third block piece, The ratio t1 / t2 is
0.8 ≦ t1 / t2 ≦ 1.4
The pneumatic tire according to any one of (1) to (5), wherein the pneumatic tire is in a range of

(7) The ratio p1 / p2 of the width p1 in the tire circumferential direction of the first block piece and the width p2 in the tire circumferential direction of the second block piece at the tire width direction central portion of the block on the tread surface But,
0.2 ≦ p1 / p2 ≦ 0.3
The ratio of the width q1 in the tire circumferential direction of the first block piece to the width q2 in the tire circumferential direction of the second block piece at the tire width direction end of the block on the tread surface. q1 / q2 is
0.4 ≦ q1 / q2 ≦ 0.6
The pneumatic tire according to any one of (1) to (6), wherein the pneumatic tire is in a range of

(8) A width in the tread circumferential direction at least at the sipe bottom of the first block piece gradually increases from an end portion of the block in the tread width direction toward a center portion, and at least the sipe bottom of the second block piece. The pneumatic pressure according to any one of (1) to (7), wherein a width in a circumferential direction of the tread gradually decreases from an end portion of the block in the tread width direction toward a central portion. tire.

(9) The air according to any one of (1) to (8), wherein an opening width of the sipe sandwiched between the first block piece and the second block piece is constant. tire.

(10) The at least one bottom raised portion for connecting the first block piece and the second block piece is provided between the first block piece and the second block piece, The pneumatic tire according to any one of 1) to (9).

(11) The protrusion having a height of half or more of the sipe width is formed in at least one place on the wall surface of the sipe between the first block piece and the second block piece. The pneumatic tire according to any one of 1) to (10).

(12) A fine structure having a height in the range of 1/50 to less than 1/10 of the sipe width is formed on at least a part of the wall surface of the sipe between the first block piece and the second block piece. The pneumatic tire according to any one of (1) to (11) above, wherein

(13) The projection is not formed in a central region in the width direction of the block, or a projection having a height lower than an end region is formed in the central region in the width direction of the block. The pneumatic tire according to (11).

(14) When the number of sipes in the block is an even number, bottom raising portions are provided at both ends in the width direction of the sipes located at both ends in the tire circumferential direction, and sipes other than the sipes located at both ends in the tire circumferential direction include: A staggered bottom is provided on one side in the width direction,
When the number of sipes in the block is an odd number, bottom-up portions are provided at both ends in the tire circumferential direction and at both ends in the width direction of the sipes located at the center in the tire circumferential direction, and are located at both ends in the tire circumferential direction and at the center in the tire circumferential direction. The pneumatic tire according to (10) above, wherein the sipe other than the sipe is provided with a staggered bottom-up portion on one side in the width direction.

(15) The pneumatic tire according to any one of (1) to (14), wherein the block is located on an outermost side in a tire width direction.

According to the present invention, the role can be shared by the first block piece and the second block piece, and both an increase in the contact area and an increase in the edge pressure can be achieved. Furthermore, by making at least one of the sipes that divide the block into a bent three-dimensional sipe, it is possible to suppress the collapse of the sipe for any direction from the road surface and increase the contact area. Thereby, a pneumatic tire with improved performance on ice can be provided.

It is a development view of a tread pattern showing an embodiment of a pneumatic tire of the present invention. It is a figure which illustrates various aspects of the block of the pneumatic tire of the present invention. 1 is a perspective view of a block according to a first embodiment of a pneumatic tire of the present invention. (a) is a cross-sectional view of the block taken along line AA in FIG. 3, and (b) is an end view of the block taken along line BB in FIG. FIG. 3 is a perspective view of a block according to a second embodiment of the pneumatic tire of the present invention. (a) is a cross-sectional view of the block taken along line C1-C1 in FIG. 5, and (b) is an end view of the block taken along line DD in FIG. It is a figure for demonstrating the effect of the pneumatic tire of this invention. It is a figure for demonstrating the definition of the dimension of a 1st block piece and a 2nd block piece. An example of the block surface of the pneumatic tire of this invention is shown. (a) It is a figure which shows the block which provided the bottom raising part in the sipe. (b) It is a figure for demonstrating arrangement | positioning in the block of the sipe raised up. It is a figure for demonstrating a mode that protrusion is provided in the wall of a sipe. It is a figure for demonstrating the position which provides a bottom raising part. It is a figure for demonstrating arrangement | positioning of a block. It is a schematic diagram of the sipe shape of each sample tire. It is a schematic diagram of the sipe shape of each sample tire. It is explanatory drawing of the tire of a prior art example. It is a figure for demonstrating the result of an abrasion test.

Hereinafter, embodiments of the pneumatic tire of the present invention will be described in detail with reference to the drawings.
In addition, since the internal reinforcement structure of a tire is the same as that of a general radial tire, illustration is abbreviate | omitted.

FIG. 1 is a development view of a tread pattern showing an embodiment of a pneumatic tire of the present invention.
In the illustrated tread pattern, a plurality of blocks 20 are formed on a tread surface 1 of a tire by a plurality of circumferential grooves 3 extending in the tread circumferential direction parallel to the tire equator CL and a plurality of widthwise grooves 4 extending in the tread width direction. Compartment. In the illustrated example, the block 20 extends in the tread width direction and has a sipe 21a that does not have a bent portion in the tire radial direction, and extends while bending in a zigzag manner in the tire width direction, and extends while also bending in the tire radial direction. A plurality of sipes 21 including three-dimensional sipes 21b are provided.
These sipes 21 penetrate the block 20 so as to connect the adjacent circumferential grooves 3 and divide the block 20 into a plurality of, in the illustrated example, seven block pieces.
In this illustrated example, the block rows in which the blocks 20 are arranged in the tread circumferential direction are arranged in two rows in the tread width direction across the tire equator CL, but the number of blocks 20 arranged is limited to this illustrated example. It is not something. For example, an asymmetric arrangement such that two rows on one side in the tread width direction and three rows on the other side across the tire equator CL is possible.
Further, it is sufficient that at least one sipe 21a and bent three-dimensional sipe 21b in the block 20 exist, and for example, various modes shown in FIGS. 2 (a) to (g) are applicable.

FIG. 3 is a perspective view of the block 20 according to the first embodiment of the pneumatic tire of the present invention.
In the figure, arrows indicate a tread circumferential direction C, a tread width direction W, and a tire radial direction R (the arrow direction is the inner side in the tire radial direction).
Each block 20 has at least one set in which the first block piece 22T and the second block piece 22R are arranged adjacent to each other.
The first block piece 22T has a width in the tread circumferential direction that gradually decreases toward the tread surface, and the second block piece 22R has a width in the tread circumferential direction that gradually increases toward the tread surface. That is, as shown in FIG. 3, the sipe 21a is not perpendicular to the tread surface, but inclined.
The third block piece 22S has a width in the tread circumferential direction that does not increase or decrease toward the tread surface. In the illustrated example, the third block piece 22S is partitioned by both ends in the tire circumferential direction and a bent three-dimensional sipe 21b. In the illustrated example, the bent three-dimensional sipe 21b is bent in a zigzag shape.

In the illustrated example, when attention is paid to the tread surface, the circumferential width of the first block piece 22T gradually decreases from the ends S ₁ and S ₂ of the block 20 in the tread width direction toward the center portion Ce. On the other hand, the circumferential width of the second block piece 22R gradually increases from the ends S ₁ and S ₂ of the block 20 in the tread width direction toward the center portion Ce.
Further, in the illustrated example, the circumferential width of the tread surface of the third block piece 22S at the circumferential end of the block is not gradually increased or decreased in the tread width direction.
Incidentally, a central portion Ce of the block 20 in the tread width direction, comprises a tread width direction center line of the block 20, and to refer to 50% or less of the area of the width of the width W _B of the block 20 around the center line To do. The end portions S ₁ and S ₂ of the block 20 in the tread width direction indicate regions on both sides of the central portion Ce.

Next, the first block piece 22T and the second block piece 22R according to the first embodiment will be described with reference to FIG.
4 (a) is a cross-sectional view of the block 20 at the center in the tread width direction of the block 20 along the line AA in FIG. 3, and FIG. 4 (b) is a cross-sectional view along the line BB of FIG. FIG. 4 is an end view of the block 20 at the end of the block 20 in the tread width direction.
Figure 4 (a), the width W _TC tread circumferential direction of the first block piece 22T at the center of the tread width direction of the block 20, shown in FIG. 4 (b), the ends of the tread width direction of the block 20 shorter than the width W _TS of the tread circumferential direction of the first block piece 22T in. That is, the circumferential width of the first block piece 22T gradually decreases from the end of the block 20 toward the center in the tread width direction. For this reason, the ground contact area of the first block piece 22T is smaller in the tread width direction center portion of the block 20 than in the tread width direction end portion.
Further, the widths W _RC1 and W _{RC2 in} the tread circumferential direction of the second block piece 22R in the center portion of the block 20 in the tread width direction shown in FIG. 4 (a) are shown in FIG. 4 (b) in the tread width direction. The widths W _RS1 and W _{RS2 in} the tread circumferential direction of the second block piece 22R at the end of the block 20 are longer than each other. That is, the circumferential width of the second block piece 22R gradually increases from the end of the block 20 toward the center in the tread width direction. For this reason, the ground contact area of the second block piece 22R is larger at the center portion of the block 20 in the tread width direction than at the end portion in the tread width direction.

FIG. 5 shows a perspective view of a block 20 according to the second embodiment of the pneumatic tire of the present invention.
The difference from the configuration in FIG. 3 is that the inclination direction of the sipe 21a is changed near the center in the tire radial direction of the block 20, as shown in FIG. That is, the width of the tread circumferential direction of the first block piece 22T gradually increases from the radially inner side to the outer side of the tire and then gradually decreases at the center of the radial length of the sipe 21a. The tread circumferential width of the second block piece 22R gradually decreases from the radially inner side to the outer side of the tire, and then gradually increases at the center of the radial length of the sipe 21a.

Next, the first block piece 22T and the second block piece 22R according to the second embodiment will be described with reference to FIG. FIG. 6 (a) is a cross-sectional view of the block 20 taken along line C1-C1 of FIG. 5, that is, the central portion of the block 20 in the tread width direction. FIG. 6B is an end view of the block 20 at the end of the block 20 in the tread width direction, that is, the line DD in FIG.
The width in the tread circumferential direction of the first block piece 22T gradually decreases after gradually increasing from the radially inner side to the outer side of the tire. On the other hand, the second block piece 22R gradually increases from the radially inner side to the outer side of the tire. In the example shown in FIG. 6, in the sectional view in the tire circumferential direction, the first block piece 22T has a maximum width in the tread circumferential direction at the center of the depth of the sipe 21a. The groove wall of the sipe 21a seen in the cross-sectional view draws a gentle arc, and the center of curvature exists in the inner direction of the first block piece 22T with respect to the groove wall. On the other hand, the second block piece 22R has a minimum width in the tread circumferential direction at the center of the depth of the sipe 21a. The groove wall of the sipe 21a seen in the cross-sectional view draws a gentle arc, and the center of curvature exists in the outer direction of the second block piece 22R with respect to the groove wall.
In the case of such a block piece, shown in FIG. 6 (a), the width W _TC of the tread circumferential direction of the first block piece 22T at the center of the tread width direction of the block 20, shown in FIG. 6 (b), shorter than the width W _TS of the tread circumferential direction of the first block piece 22T at the ends of the tread width direction of the block 20. That is, the circumferential width of the first block piece 22T gradually decreases from the end of the block 20 toward the center in the tread width direction. For this reason, the ground contact area of the first block piece 22T is smaller in the tread width direction center portion of the block 20 than in the tread width direction end portion.
Further, the widths W _RC1 and W _{RC2 in} the tread circumferential direction of the second block piece 22R at the center portion of the block 20 in the tread width direction shown in FIG. 6 (a) are shown in FIG. 6 (b) in the tread width direction. The widths W _RS1 and W _{RS2 in} the tread circumferential direction of the second block piece 22R at the end of the block 20 are longer than each other. That is, the circumferential width of the second block piece 22R gradually increases from the end of the block 20 toward the center in the tread width direction. For this reason, the ground contact area of the second block piece 22R is larger at the center portion of the block 20 in the tread width direction than at the end portion in the tread width direction.

As shown in the first and second embodiments, in the tire of the present invention, first, the width of the block piece in the tread circumferential direction gradually decreases toward the tread surface, and toward the tread surface. It is important to have at least one set in which the gradually increasing second block pieces are arranged next to each other.
With reference to FIG. 7, the operational effects of the first block piece 22T and the second block piece 22R will be described.

As shown in FIG. 7, when the braking force is applied when the tire rolls in the arrow direction, for example, on the icy road surface 15, the first block piece 22T and the second block piece 22R are opposite to the traveling direction. The force to fall in the direction works. By adopting a shape that gradually decreases with respect to the road surface of the first block piece, the edge portion of the first block piece becomes an obtuse angle. Therefore, the bulge direction of the rubber at the edge portion when the load is applied is not parallel to the road surface, but is a direction toward the road surface. As a result, the edge end is easily restrained with respect to the road surface. Therefore, the first block piece 22T easily collapses, and the local deformation of the edge portion indicated by a dotted circle in the figure increases, so that the edge pressure at the edge portion is improved.
On the other hand, the second block piece 22R has a shape that expands toward the surface of the block piece, so that it does not fall down, the edge part does not leave the ground contact surface, and it expands against the icy road surface under load. Deform. For this reason, the second block piece 22R has a larger ground contact area than when there is no load, and the floating of the block piece 22R is suppressed. Thus, by separating the functions of increasing the edge pressure and increasing the contact area for each block piece, it is possible to improve on-ice friction characteristics, particularly on-ice brake performance, when viewed as a block.

In the tire of the present invention, the width of the first block piece 22T in the tread circumferential direction at least on the tread surface is gradually decreased from the end of the block 20 in the tread width direction toward the center, and the second block piece. It is important to gradually increase the width of 22R in the tread circumferential direction from the end of the block 20 toward the center in the tread width direction.
The obtuse angle shape of the edge portion of the first block piece is more emphasized in the center portion in the tire width direction where the edge pressure tends to be small. Thereby, the effect that the edge ends are easily restrained with respect to the road surface is increased, and as a result, a high edge pressure can be obtained.
Further, the second block piece has a large circumferential width on the side in contact with the road surface of the block piece and a small circumferential width on the sipe bottom side at the center in the tire width direction. Therefore, the shape becomes more stable with respect to the input from the road surface, and the ground contact area increases.
As a result, each of the edge effect and the effect of increasing the contact area is emphasized, and the friction performance on ice can be greatly improved.

Furthermore, in the tire of the present invention, it is important that at least one of the sipes that divide the block into block pieces is a three-dimensional sipe that extends while bending in the tire width direction and also extends in the tire radial direction. .
Thereby, even with respect to input in any direction from the road surface, the high contact force between the wall surfaces of the bent three-dimensional sipe can suppress the collapse of the block pieces and suppress the reduction of the contact area.
Moreover, it is preferable to arrange the bent three-dimensional sipe on at least one of both ends in the tire circumferential direction of the block, and more preferably on both ends.
This is because by arranging a bent three-dimensional sipe at the stepping-in and kicking-out ends of the block, it is possible to more effectively suppress the collapse of the block pieces and suppress the reduction of the contact area.
In addition, bending 3D sipes are added to both ends of the tire in the circumferential direction, and are also provided in the center of the tire circumferential direction to further prevent the block pieces from collapsing and reducing the contact area against input from various directions. Can be suppressed.
In FIGS. 3 and 5, the bent three-dimensional sipe 21b exemplifies a zigzag bent shape, but it only needs to have a bent portion, for example, along the tire radial direction while repeating unevenness. It may be a sipe that extends.

Also, as shown in the second embodiment, it is preferable that the first block piece 22T has a narrow shape with a narrow groove bottom portion of the sipe 21a. This is because the rigidity of the first block piece 22T can be reduced, the first block piece 22T can be more easily collapsed, and the performance on ice can be further improved.

Here, when placing the bent three-dimensional sipe at the stepping-in and kicking-out ends of the block, as shown in FIG. 8, the tire of the second block piece 22R at the tread tread surface at the center in the tire width direction of the block The ratio s1 / s2 between the circumferential width s1 and the tire circumferential width s2 of the third block piece 22S is
1.0 ≦ s1 / s2 ≦ 1.6
In the tread surface, at the tire width direction end of the block, the ratio t1 / the tire circumferential direction width t1 of the second block piece 22R and the tire circumferential direction width t2 of the third block piece 22S t2 is
0.8 ≦ t1 / t2 ≦ 1.4
It is preferable that it exists in the range.
This is because if the ratio s1 / s2 is less than 1.0, the second block piece collapses and the ground contact area decreases. Further, if the ratio s1 / s2 is larger than 1.6, the deformation that the ground contact portion of the second block piece spreads becomes insufficient, and the ground contact area is reduced.
Similarly, if the ratio t1 / t2 is less than 0.8, the second block piece collapses and the ground contact area decreases. Further, if the ratio t1 / t2 is larger than 1.4, the deformation that the ground contact portion of the second block piece spreads is not sufficient, and the ground contact area is reduced.
Here, as shown in FIG. 8, the “circumferential width” of the block piece defined by the bent three-dimensional sipe is defined by the distance from the center of the amplitude of the bent three-dimensional sipe.

Furthermore, in the present invention, as shown in FIG. 3, the tire circumferential direction width p1 of the first block piece and the tire circumferential direction width p2 of the second block piece in the tire width direction central portion of the tread surface, as shown in FIG. Ratio p1 / p2 is in the range of 0.2 to 0.3, and the tire circumferential direction width q1 of the first block piece at the tire width direction end of the tread surface and the tire circumference of the second block piece The ratio q1 / q2 to the direction width q2 is preferably in the range of 0.4 to 0.6.
This is because if the ratio p1 / p2 is less than 0.2, the first block piece collapses extremely at the time of grounding, and sufficient edge effect cannot be obtained, while if the ratio p1 / p2 is greater than 0.3, the first block This is because the collapse of the piece is small, and in this case also, a sufficient edge effect cannot be obtained.
Similarly, when the ratio q1 / q2 is less than 0.4, the first block piece collapses extremely at the time of grounding, and a sufficient edge effect cannot be obtained, while when the ratio q1 / q2 is greater than 0.6, the first This is because the collapse of the block piece is small and a sufficient edge effect cannot be obtained.

Further, the width of the first block piece in the tread circumferential direction at least at the sipe bottom gradually increases from the end of the block in the tread width direction toward the center, and the second block piece at least in the tread circumferential direction at the sipe bottom. Is preferably gradually reduced from the end of the block in the tread width direction toward the center.
As a result, the first block piece has a larger circumferential width on the sipe bottom side at the center in the width direction of the block, so that the first block piece is more likely to fall down and the edge pressure is further increased. On the other hand, since the second block piece has a smaller circumferential width on the sipe bottom side, the second block piece becomes more stable against the falling force and can further suppress the reduction of the contact area. It is.

Incidentally, if the opening width of the sipe 21a is too wide, the ratio of the block pieces in the block 20 is reduced, and the block rigidity is lowered, which is not preferable. Therefore, it is preferable that the groove walls facing each other across the sipe 21a have the same shape and the opening width of the sipe 21a is constant.

Further, it is preferable that the circumferential width of the first block piece 22T is smaller than the circumferential width of the second block piece 22R. It is preferable to reduce the rigidity of the first block piece 22T so that the collapse of the first block piece 22T is more likely to occur.

Furthermore, it is preferable that the first block pieces 22T and the second block pieces 22R are alternately arranged over the entire block 20 in the tread circumferential direction. For this reason, in the above-described example, such an arrangement is obtained except for the block pieces 22S at both ends.
However, in one block 20, there may be at least one set in which the first block piece 22T and the second block piece 22R are arranged adjacent to each other. For example, as illustrated in the block surface in FIG. 9, the first block pieces 22T and the second block pieces 22R may be arranged adjacent to each other.

10 (a) and 10 (b) are perspective views of a block 20 according to a third embodiment of the pneumatic tire of the present invention. The difference from the configuration in FIG. 5 is that the sipe is provided with a bottom raising that changes the depth of the sipe and raises a part or all of the sipe bottom to the outside in the tire radial direction compared to other sipe. .
In the example shown in FIG. 10A, at the bottom of the sipe 21a, at least one, in the illustrated example, three bottom raised portions 24 that connect the first block piece 22T and the second block piece 22R are provided. By providing the bottom raised portion 24, the fall of the second block piece 22R is further suppressed, so that a ground contact area can be ensured reliably.
In the illustrated example, the bottom raised portion 24 is provided only on the sipe 21a in front of the drawing, but the bottom raised portion 24 may be provided on all the sipes 21.
FIG. 10B shows an example of the arrangement of the sipe with the bottom raised in the block 20. In the illustrated example, first, the bent three-dimensional sipe 21b at both ends in the circumferential direction is raised at both ends in the width direction, and the other sipe is provided with a raised bottom in a staggered pattern. That is, the sipe 21c in FIG. 9 (b) is raised in the positive direction in the tire width direction (the direction of the arrow in the tire width direction W in FIG. 9 (b)), and the sipe 21d is negative in the tire width direction. The direction of is raised. These

sipes

21c and 21d are alternately arranged. By providing bottom-ups at both ends in the width direction of the sipe at both ends in the circumferential direction of the block 20, it is possible to suppress collapse of the block pieces at the stepping-in end and kicking-out end of the block, and it is possible to suppress a decrease in the contact area. In addition, by providing a raised staggered bottom, the edge effect due to the fall of the first block piece 22T is not hindered, and the fall of the second block piece can be suppressed and the ground contact area can be increased. This is because the rigidity of the block 20 can be appropriately increased.

Further, as shown in a schematic perspective view of FIG. 11 (a), at least a part of the wall surface of the sipe between the first block piece and the second block piece has a half or more of the sipe width (opening width). It is preferable to provide a protrusion 25 having a height.
This is because the protrusions can further suppress the collapse of the block pieces and suppress the reduction of the ground contact area.
Furthermore, the protrusion provided on the wall surface of the sipe between the first block piece and the second block piece is not provided in the central region in the width direction of the block as shown in FIG. A protrusion having a height lower than that of the end region is formed in the central region in the width direction.
In the central portion in the width direction of the block, the length in the circumferential direction of the first block piece is short, and the shearing force and slip at the edge end are small, and wear is smaller than in other positions. For this reason, if a protrusion is provided in the center portion in the width direction, sliding is suppressed due to the support between sipes, the amount of further wear is reduced, and uneven wear in the block width direction may occur.
Furthermore, it is preferable to form a fine structure having a height in the range of 1/50 to less than 1/10 of the sipe width (opening width).
This is because the fine structure portion strengthens the restraint between the wall surfaces sandwiching the sipe 21a, further suppresses the collapse of the block pieces, and suppresses the reduction of the ground contact area.
In addition, as shown in FIGS. 12 (a) to (g) in correspondence with FIGS. 2 (a) to 2 (g), when the number of sipes in the block is an even number, they are located at both ends in the tire circumferential direction. It is preferable to provide bottom raised portions at both ends in the width direction of the sipe, and to provide sipe other than the sipes located at both ends in the tire circumferential direction in a staggered manner on one side in the width direction. In FIGS. 12 (a) to 12 (g), the position where the bottom raised portion is provided is indicated by a portion surrounded by a dotted line.
In addition, when the number of sipes in the block is an odd number, bottom-up portions are provided at both ends in the tire circumferential direction and at both ends in the width direction of the sipes located at the tire circumferential center, and are positioned at both ends in the tire circumferential direction and at the center in the tire circumferential direction. It is preferable to provide bottom-up portions in a staggered manner on one side in the width direction for sipe other than the sipe.
Furthermore, as shown in FIG. 13, the block having the sipe described above is preferably provided only on the outermost side in the tire width direction.
This is because the shoulder side bears the breaking force during braking.

The pneumatic tire (invention example tire) of the present invention, the conventional pneumatic tire (conventional example tire), and the pneumatic tire of the comparative example (comparative example tire) were prototyped based on the specifications described later, and the braking performance on ice was improved. A test to be evaluated was performed and will be described below.
Each test tire has the tread pattern shown in FIG. 1, and has the same internal structure as a general pneumatic tire. The schematic top view of each test tire block is shown in FIG. 2, the sipe shape is schematically shown in FIGS. 14 and 15, and FIG. 16 shows a conventional tire tread (upper view) and block schematic view (lower view). ).
Here, in FIGS. 14 and 15, the upper side in the drawing shows the sipe bottom side, and the lower side in the drawing shows the tread tread side. In FIG. 14 and FIG. 15, the dotted line shows the case where the sipe is flat.
Table 1 below summarizes the composition of the block of each sample tire, the shape of the sipe, and the arrangement of the bent three-dimensional sipe. The other tires have the same specifications.
The ratio s1 / s2 between the width s1 in the tire circumferential direction of the second block piece and the width s2 in the tire circumferential direction of the third block piece at the center part in the tire width direction of the block, and the end part in the tire width direction of the block The ratio t1 / t2 of the tire circumferential direction width t1 of the second block piece and the tire circumferential direction width t2 of the third block piece is s1 / s2 = 1.3, t1 / t2 = 1.15 unless otherwise specified. Is common.

Each test tire has a tire size of 195 / 65R15. These tires were assembled into standard rims to form tire wheels, and the tire internal pressure was adjusted to 200 kPa. The tire was mounted on a passenger car and a braking test was conducted on an icy road.
In the braking test, the braking distance was measured from the initial speed of 40km / h until full braking was applied, and the average deceleration was calculated from the initial speed and braking distance.
The braking test results are expressed as an average deceleration index and are shown in Table 2.
The index is expressed as an index when the average deceleration of the conventional tire is 100, and the larger the value, the better the result.

Next, for the tire according to Inventive Example 7, the braking test described above was carried out using the tire circumferential direction width s1 of the second block piece and the tire circumferential direction width s2 of the third block piece at the center in the tire width direction of the block. And the ratio t1 / t2 between the tire circumferential direction width t1 of the second block piece and the tire circumferential direction width t2 of the third block piece at the tire width direction end of the block. went.
The results are shown in Table 3 below.
The index is expressed as an index when the average deceleration of the conventional tire is 100, and the larger the value, the better the result.

Further, for the tire according to Invention Example 7, the braking test described above was carried out using the ratio p1 / p2 between the tire block circumferential width p1 of the first block piece and the tire circumferential width p2 of the second block piece and the first Tires with various ratios q1 / q2 between the width q1 of the block piece in the tire circumferential direction and the width q2 of the second block piece in the tire circumferential direction were prototyped, and the performance on ice of the tire was evaluated.
The results are shown in Table 4 below.
The index is expressed as an index when the average deceleration of the conventional tire is 100, and the larger the value, the better the result.

First, it can be seen from Table 2 that the tires according to Invention Examples 1 to 20 are superior in braking test results to the tires according to Conventional Example and Comparative Example 1. In addition, the tires according to Invention Examples 1 to 10 have better braking test results than the tires according to Comparative Example 2, and the tires according to Invention Examples 11 to 20 have a braking test better than the tires according to Comparative Example 3. The result is excellent.
Inventive Examples 1 to 10 correspond to Inventive Examples 11 to 20, respectively, by changing the shape of the sipe only to "the first block piece, the narrow width of the groove bottom portion of the sipe and the constricted shape". .
Comparison between Invention Examples 1 to 10 and Invention Examples 11 to 20 reveals that Invention Examples 1 to 10 are superior in braking test results to those corresponding to Invention Examples 11 to 20.
From the comparison of Invention Examples 1 to 4 and Comparison of Invention Examples 11 to 14, it can be seen that high performance on ice can be obtained by optimizing the arrangement of the bent three-dimensional sipe as described above.
Invention Examples 6 and 16 in which the sipe shape at the sipe bottom position is optimized by comparison between Invention Examples 5 and 6 and Invention Examples 15 and 16 are compared with Invention Examples 5 and 15, respectively. It turns out that the cornering test result on ice is excellent.
Inventive Examples 7 and 8 in which the shape and structure of the sipe are optimized by comparison between Inventive Example 6 and Inventive Examples 7, 8, 9, and 10, and Inventive Example 16 and Inventive Examples 17, 18, 19, and 20. , 9, 10, 17, 18, 19, and 20 show that the braking test results are improved.
Further, Comparison between Invention Example 8 and Invention Example 8-2, Comparison between Invention Example 10 and Invention Example 10-2, Comparison between Invention Example 18 and Invention Example 18-2 Invention Example 20 and Invention Example 20-2 From these comparisons, it can be seen that Invention Examples 8, 10, 18, and 20 having no protrusion at the central portion in the width direction of the block have the same braking test results as those having the protrusion.

Table 3 also shows that the braking test results are improved over the conventional tire when s1 / s2 is 1.0 or more and 1.6 or less and t1 / t2 is 0.8 or more and 1.4 or less.
Further, Table 4 shows that the performance on ice is improved over the conventional example when p1 / p2 is 0.2 or more and 0.3 or less and q1 / q2 is 0.4 or more and 0.6 or less.

Inventive Example 10 and Inventive Example 10-2 were subjected to an actual vehicle wear test. The test compared the mode of wear at the center of the block width after running for 1000 km.
In the tire according to Invention Example 10-2, a step of 0.6 mm occurred as shown in FIG. 17 (a). On the other hand, in the tire according to Invention Example 10, as shown in FIG. 17 (b), the level difference was 0.2 mm, and uneven wear in the width direction of the block was suppressed.

CL tire equator
1 Tread
3 Circumferential groove
4 Width direction groove
15 Ice surface
20 blocks
21 Sipe
21a Sipe
21b Bending type 3D sipe
21c Raised sipe
21d Raised sipe
22T 1st block piece
22R 2nd block piece
22S 3rd block piece
24 Bottom raised part
25 Protrusions

Claims

A plurality of blocks are defined on the tread surface of the tire by a plurality of circumferential grooves extending in the tread circumferential direction and a plurality of width grooves extending in the tread width direction, and a plurality of sipes extending in the tread width direction are provided on the block. A pneumatic tire,
The block is divided into a plurality of block pieces by the sipe, and a first block piece whose width in the tread circumferential direction of the block piece gradually decreases toward the tread surface, and a second block that gradually increases toward the tread surface. Having at least one set in which the pieces are arranged next to each other,
The width in the tread circumferential direction at least on the tread surface of the first block piece gradually decreases from the end of the block in the tread width direction toward the center, and the at least the tread surface of the second block piece. The width in the tread circumferential direction gradually increases from the end of the block in the tread width direction toward the center,
At least one of the sipe is a three-dimensional sipe that extends while being bent in the tire width direction and is bent in the tire radial direction.
The width in the tread circumferential direction of the first block piece gradually decreases after gradually increasing from the radially inner side to the outer side of the tire,
2. The pneumatic tire according to claim 1, wherein the width in the tread circumferential direction of the second block piece gradually increases after gradually decreasing from the radially inner side to the outer side of the tire.
3. The pneumatic tire according to claim 1, wherein at least one of the sipes at both ends in the tire circumferential direction of the block is the bent three-dimensional sipe.
The pneumatic tire according to any one of claims 1 to 3, wherein sipes at both ends of the block in the tire circumferential direction are the bent three-dimensional sipes.
The pneumatic tire according to any one of claims 1 to 4, wherein the bent three-dimensional sipe is provided at both ends in the tire circumferential direction and at a central portion in the tire circumferential direction.
A ratio s1 / s2 between a tire circumferential direction width s1 of the second block piece and a tire circumferential direction width s2 of the third block piece at a tire width direction central portion of the tire tread surface is ,
1.0 ≦ s1 / s2 ≦ 1.6
And in the tire width direction end of the block on the tread surface of the tire, a tire circumferential direction width t1 of the second block piece, and a tire circumferential direction width t2 of the third block piece, The ratio t1 / t2 is
0.8 ≦ t1 / t2 ≦ 1.4
The pneumatic tire according to any one of claims 1 to 5, wherein the pneumatic tire is in a range of.
A ratio p1 / p2 of a tire circumferential direction width p1 of the first block piece and a tire circumferential direction width p2 of the second block piece in the tire width direction central portion of the tread surface,
0.2 ≦ p1 / p2 ≦ 0.3
The ratio of the width q1 in the tire circumferential direction of the first block piece to the width q2 in the tire circumferential direction of the second block piece at the tire width direction end of the block on the tread surface. q1 / q2 is
0.4 ≦ q1 / q2 ≦ 0.6
The pneumatic tire according to any one of claims 1 to 6, wherein the pneumatic tire is in a range of.
The tread circumferential width at least at the sipe bottom of the first block piece gradually increases from the end of the block toward the center in the tread width direction, and at least the tread at the sipe bottom of the second block piece. The pneumatic tire according to any one of claims 1 to 7, wherein a circumferential width gradually decreases from an end portion of the block in a tread width direction toward a central portion.
The pneumatic tire according to any one of claims 1 to 8, wherein an opening width of the sipe sandwiched between the first block piece and the second block piece is constant.
10. The at least one bottom raising portion for connecting the first block piece and the second block piece is provided between the first block piece and the second block piece. The pneumatic tire according to any one of the above.
11. A protrusion having a height equal to or more than half of the sipe width is formed at least at one location on the wall surface of the sipe between the first block piece and the second block piece. The pneumatic tire according to any one of the above.
A fine structure having a height in the range of 1/50 to less than 1/10 of the sipe width is formed on at least a part of the wall surface of the sipe between the first block piece and the second block piece. The pneumatic tire according to any one of claims 1 to 11, characterized in that.
12. The protrusion according to claim 11, wherein the protrusion is not formed in the central region in the width direction of the block, or a protrusion having a height lower than that of the end region is formed in the central region in the width direction of the block. The described pneumatic tire.
When the number of sipes in the block is an even number, bottom-up portions are provided at both ends in the width direction of the sipes located at both ends in the tire circumferential direction, and one side in the width direction is provided for sipes other than the sipes located at both ends in the tire circumferential direction. In the zigzag pattern,
When the number of sipes in the block is an odd number, bottom-up portions are provided at both ends in the tire circumferential direction and at both ends in the width direction of the sipes located at the center in the tire circumferential direction, and are located at both ends in the tire circumferential direction and at the center in the tire circumferential direction. 11. The pneumatic tire according to claim 10, wherein the sipe other than the sipe is provided with a raised portion in a zigzag manner on one side in the width direction.
The pneumatic tire according to any one of Claims 1 to 14, wherein the block is located on the outermost side in the tire width direction.