JPH1178430A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of restraining a performance change after wearing. SOLUTION: Sipes 20-30 are formed on a central part in the tire peripheral direction of a block 18. The sipes 20-30 are furnished with rectilinear parts 20A-30A respectively extending in the tire radial direction on the sipe bottom sides and are furnished with inclined parts 20B-30B inclined in the tire radial direction on the tire tread part sides. Additionally, the rectilinear parts 20A-30A are connected to each other in a straight line in the tire cross direction. The inclined parts 20B, 24B, 28B and the inclined parts 22B, 26B, 30B are inclined in the opposite directions with each other. The sipes 20-30 gradually approach each other adjacent fellows in accordance with advancement of wearing, and it is possible to restrain increase of rigidity of the block 18. Consequently, it is possible to restrain a change of performance such as the lowering of a braking distance on a wet road surface after wearing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire having a plurality of land portions on a tread tread portion and at least one of the land portions having a plurality of sipes.

[0002]

2. Description of the Related Art Conventionally, in a tread portion of a pneumatic tire, a plurality of sipes have been arranged on a land portion (for example, a block) of the tread portion in order to secure a ground contact property.

[0003]

By the way, the land portion of the tread portion of a tire tread originally increases in rigidity as wear progresses, and a change in performance such as a reduction in braking distance on a wet road surface appears. There's a problem.

[0004] However, the conventional sipes have not been arranged to suppress a change in rigidity before and after wear.

The present invention has been made in consideration of the above-described circumstances, and has as its object to provide a pneumatic tire capable of suppressing a change in performance after wear by controlling a change in rigidity of a land portion of a tire tread before and after wear. .

[0006]

The invention according to claim 1 is a pneumatic tire having a plurality of land portions on a tread tread portion, and a plurality of sipes formed on at least one of the land portions. The plurality of sipes are separated from each other on the side of the tread portion, and are close to or connected to each other on the side of the bottom of the groove.

Next, the operation of the pneumatic tire according to the first aspect will be described. In the pneumatic tire according to the first aspect, in the initial stage of wear, the plurality of sipes are separated from each other on the tread side and do not divide the land, so that the rigidity is equivalent to that of the land where no sipe is formed. Can be kept.

When the wear of the land part progresses, the rigidity of the land part where no sipe is formed increases as the wear progresses.
In the land portion of the present invention, a plurality of sipes approach each other and the land portion is substantially divided (when the plurality of sipes are connected at the groove bottom side, they are completely divided), and the wear progresses. The accompanying increase in rigidity of the land can be suppressed.

That is, according to the present invention, a change in rigidity of a land portion before and after wear can be suppressed, so that a change in performance such as a decrease in a braking distance on a wet road surface can be suppressed.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION

[First Embodiment] A first embodiment of a pneumatic tire according to the present invention will be described with reference to FIGS.

As shown in FIG. 1, a plurality of circumferential grooves 14 are formed in a tread 12 of a pneumatic tire 10 of the present embodiment.
The plurality of blocks 18 are partitioned by the plurality of lateral grooves 16.

As shown in FIG. 2, sipe 20, 22, 24, 26, 28, 30 is provided at the center of the block 18 in the tire circumferential direction (direction of arrow A and arrow B) in the tire width direction (arrow L). Direction and arrow R direction).

The sipe 20 is connected to one side 18A of the block 18, and the sipe 30 is connected to the other side 18B.

Sipe 20, 22, 24, 26, 28, 3
0 is provided on the sipe bottom side with straight portions 20A, 22A, 24A, 26A, 28A, 30A extending in the tire radial direction (the direction of arrow r), and the inclined portions 20B, 22B, 24B, 26B, 28B, 30B
Is provided on the tire tread side.

The straight sections 20A, 22A, 24A, 26A,
28A and 30A are connected linearly in the tire width direction.

The inclined portions 20A, 24A, 28A and the inclined portions 22A, 26A, 30A are inclined in opposite directions to each other, and the tire tread before wear (when new) is shown in FIG. 2 and FIG. Sipe 20, 22, 24, 26, 2
8, 30 are spaced apart from each other.

A blade (metal plate) for forming a sipe is provided on the inner surface of a mold (not shown) for vulcanizing and molding the pneumatic tire 10. 20, 22, 24, 26, 2
In order to form 8,30, an independent one is provided for each sipe.

These blades have spring properties and can be elastically deformed. Therefore, when the pneumatic tire 10 is removed from the mold after vulcanization, these blades are elastically deformed and pulled out from the sipe portion.

Next, the operation of the pneumatic tire 10 of the present embodiment will be described. As shown in FIG. 4, the change amount ΔS of the tire tread portion when a force F is applied in the tire circumferential direction to one end side of the tire tread portion of the fixed block 18 is represented by the height (amount of wear) of the block 18. As a result, the results shown in the graph of FIG. 5 were obtained.

FIG. 5 shows the result (indicated by a dotted line) of the block 18 of the present embodiment, and shows the linear sipe 3 shown in FIG.
The result of the block 34 in which 2 is formed (indicated by a dashed line) and the result of the block 36 without a sipe as shown in FIG. 7 (indicated by a solid line) are shown. .).

In the block 36 without sipe, as shown by the solid line in FIG. 5, the amount of change ΔS of the block 36 when the force F is applied becomes smaller with the progress of wear, that is, the rigidity of the block 36 increases. You can see that it goes.

The block 3 on which the sipe 32 is formed
4 also shows that the rigidity of the block 34 increases as the wear progresses. It is apparent that the block 34 in which the sipe 32 is formed has a larger change amount ΔS when the force F is applied than the block 36 without the sipe and has a lower rigidity.

On the other hand, when the block 18 of the present embodiment is new (before abrasion), as shown in FIGS.
Since the tires 22, 24, 26, 28, 30 are separated from each other on the tire tread side and are not divided, the same rigidity as that of the block 36 without sipe can be obtained (see FIG. 5; Initially, it overlaps with the result of block 36 (solid line).)

Next, when the wear of the block 18 progresses, the variation ΔS decreases to some extent, that is, the rigidity of the block 18 increases, but thereafter, the variation ΔS increases, that is, the rigidity of the block 18 increases. Decrease.

Further, as the wear of the block 18 progresses, the variation ΔS gradually decreases, that is, the block 1
8 gradually increases in rigidity.

At the end of wear, as shown in FIG. 8, the sipes 20, 22, 24, 26, 28, and 30 are connected in a straight line, and the block 18 is divided. It has the same rigidity.

As shown in the graph of FIG. 5, the difference between the amount of change before and after wear of the block 36 without sipe, the difference between the amount of change before and after wear of the block 18 of the present embodiment, and the formation of the linear sipe 32 are shown. Comparing the difference in the amount of change of the block 34 before and after the wear, the difference is much smaller than the difference, and the block 18 of the present embodiment is different from the block 3 in FIG.
It can be seen that the amount of change in rigidity is smaller than that of the block 4 and the block 36.

Therefore, in the pneumatic tire 10 according to the present embodiment, in which the amount of change in rigidity due to wear is small, it is possible to suppress a change in performance such as a decrease in a braking distance on a wet road surface after wear. Second Embodiment A pneumatic tire according to a second embodiment of the present invention will be described with reference to FIGS.

As shown in FIG. 9, the block 40 has a tire width direction (arrow L direction and arrow R direction) on both sides in the tire circumferential direction (arrow A direction and arrow B direction) across the center.
Direction)). The sipe 42 and the sipe 44 have a fixed length toward the bottom of the sipe groove and are formed in parallel with each other. Further, the depth of the sipe 42 and the depth of the sipe 44 are the same.

The side of the sipe 42 in the direction of arrow R is connected to one side surface 40A. On the other hand, a sipe 48 extending in the tire circumferential direction and formed at the same depth as the sipe 42 is connected to an end of the sipe 42 on the arrow L side. Sipe 4
8, a base portion 48A having a constant length is provided on the sipe bottom side, and a tapered portion 48B whose length becomes shorter toward the tire tread portion side is provided on the tire tread portion side. I have. The base 48A and the sipe 44 are separated by a predetermined distance.

The arrow L side of the sipe 44 is connected to the other side surface 40B. On the other hand, a sipe 52 extending in the tire circumferential direction and formed at the same depth as the sipe 44 is connected to an end of the sipe 44 on the arrow R direction side. Sipe 5
2 is provided in the tire radial direction, a base 52A having a fixed length is provided on the sipe bottom side, and a tapered portion 52B whose length is reduced toward the tire tread side is provided on the tire tread side. I have. The base 52A and the sipe 42 are separated by a predetermined dimension.

Next, the operation of the present embodiment will be described. In the block 40 according to the present embodiment, in the initial stage of wear, the distance between the sipe 44 and the sipe 48 and the distance between the sipe 42 and the sipe 52 are large on the tread surface as shown in FIGS.
As the wear of the block 40 progresses, as shown in FIG. 11, the distance between the sipe 44 and the sipe 48 and the distance between the sipe 42 and the sipe 52 are reduced, and the rigidity of the block 40 is reduced. A change in rigidity of the block 40 can be suppressed.

The present invention is not limited to the shapes, numbers, arrangements, and the like of the sipes shown in the first and second embodiments, and various modifications may be made without departing from the gist of the present invention. Is possible.

[0034]

As described above, the pneumatic tire according to the first aspect has the above-described configuration, so that a change in rigidity of a land portion of a tire tread tread portion before and after wear can be suppressed, for example,
It has an excellent effect that a performance change such as a decrease in a braking distance on a wet road surface after wear can be suppressed.

[Brief description of the drawings]

FIG. 1 is a plan view of a tread of a pneumatic tire according to a first embodiment of the present invention.

FIG. 2 is a perspective view of a block (when new) shown in FIG. 1;

FIG. 3 is an enlarged plan view of the block shown in FIG. 1;

FIG. 4 is a perspective view showing a block when a force F is applied.

FIG. 5 is a graph showing a relationship between block height and displacement amount.

FIG. 6 is a perspective view of a block formed in a conventional sipe.

FIG. 7 is a perspective view of a block where no sipe is formed.

FIG. 8 is a perspective view of the block after wear.

FIG. 9 is a perspective view of a block of a pneumatic tire according to a second embodiment of the present invention.

FIG. 10 is a plan view of the block shown in FIG. 9;

FIG. 11 is a perspective view of the block shown in FIG. 9 after being worn.

[Description of Code] 10 Pneumatic Tire 12 Tread 18 Block (Land) 20 Sipe 22 Sipe 24 Sipe 26 Sipe 28 Sipe 30 Sipe 42 Sipe 44 Sipe 48 Sipe 52 Sipe

Claims (1)

[Claims] 1. A pneumatic tire having a plurality of land portions on a tread tread portion, and a plurality of sipes formed on at least one of the land portions, wherein the plurality of sipes are mutually separated on a tread side. Separated
A pneumatic tire which is close to or connected to a groove bottom side.