JP4070513B2 - Pneumatic tire - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic tire in which a sipe is provided in a land portion, and relates to prevention of cracks and uneven wear at a sipe end portion.
[0002]
[Prior art]
In pneumatic tires, sipes may be provided on land portions such as blocks and ribs for performance improvement. The end of the sipe is either an end (opening end) that opens and terminates in a groove that forms the land at the edge of the land, or an end (blocking end) that closes and ends inside the land It is. If there are many sipes whose both ends are open ends, the rigidity of the land will be reduced more than necessary. For this reason, all or part of the sipe is often a sipe having at least one closed end.
[0003]
At the closed end of the sipe, there is a risk that cracks may occur due to a force acting to widen the closed end due to stress caused by friction between the road surface and the land. Therefore, a structure has been adopted in which an enormous portion such as a roundness exceeding the thickness of the sipe is connected to the sipe closed end. Such enormous parts relieve stress concentration and prevent cracks.
[0004]
[Problems to be solved by the invention]
However, if the enormous part is small, the crack prevention effect is low, so the enormous part needs to be enlarged. Along with this, the proportion of the huge part in the land part increases. As a result, the area between the sipes becomes narrow, the strength of the area decreases, and the area may be lost or broken.
[0005]
Even if an enormous portion is provided, followability to external force is deteriorated due to stress concentration on the closed end. As a result, the friction energy increases, so the amount of wear increases and uneven wear may occur.
[0006]
An object of the present invention is to alleviate the stress applied to the sipe closed end, prevent the occurrence of cracks, facilitate the movement in the vicinity of the sipe end, improve the followability to external force, and prevent uneven wear.
[0007]
[Means for Solving the Problems]
As a result of intensive studies to solve the above-mentioned problems, the present invention has a land portion formed by a groove carved in the tread surface, and a sipe having at least one end terminating in the land portion is formed in the land portion. In the provided pneumatic tire,
A pneumatic tire was employed in which a small hole was provided apart from an end portion terminating in the land portion of the sipe, and the size of the small hole was 1 to 5 times the width of the sipe.
[0008]
The small holes provided apart from the sipe closed end relieve the stress applied to the sipe closed end and prolong the fatigue life of repeated stress. This is presumably because the small hole is also deformed by an external force and is separated from the sipe closed end, so that the stress distribution around the sipe closed end changes, and as a result, the stress applied to the sipe closed end is reduced.
[0009]
The shape of the small holes may be a circle or a polygon such as an ellipse or a rectangle, but a circle or an ellipse is preferable from the viewpoint of preventing cracks. The size of the small holes is preferably 1 to 5 times the width of the sipe. If the small hole is small, it is difficult to manufacture the small hole, the effect of stress relaxation is low, and if the small hole is large, the proportion of the small hole is increased, and the rigidity of the land portion may be lowered. . The size of the small hole is a diameter if it is a circle, and the widest interval if it is another shape.
[0010]
The shortest separation distance from the sipe closed end to the small hole is preferably 1 to 5 mm. If it is less than 1 mm, the gap is narrow, and there is a risk of missing or tearing. If it exceeds 5 mm, the change in the stress distribution at the sipe closed end is small, and the proportion occupied by the small holes is high, which may reduce the rigidity of the land portion. In addition, it is preferable to provide a small hole on the extension line of a sipe.
[0011]
Further, the size of the small hole can be set to 1 to 4 mm. If the size of the small hole is less than 1 mm, it is difficult to produce the small hole, and the effect of stress relaxation is low. This is because if the size of the small holes exceeds 4 mm, the proportion of the small holes increases, and the rigidity of the land portion may be lowered. The size of the small holes is more preferably around 2 mm.
[0012]
The sipe may be a pneumatic tire having one end opened at a land edge and the other end terminated inside the land, and the small hole is provided on an extension line of the sipe. .
[0013]
In a sipe where one end opens at a land edge and the other end terminates inside the land, uneven wear called river wear becomes a problem. The small hole facilitates deformation in the tire circumferential direction at the sipe closed end, so that followability to external force is improved. As a result, the friction energy is reduced, so the amount of wear is reduced and uneven wear can be suppressed.
[0014]
A pneumatic tire in which the depth of the small hole is 0.5 times or more of the depth of the sipe may be used.
[0015]
Since stress is also generated in the depth direction, the effect of stress relaxation is reduced if the depth of the small hole is shallow. Therefore, the depth of the small hole is preferably 0.5 times or more the sipe depth.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of a pneumatic tire according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic development view of a pattern. The circumferential groove 1 is a groove continuous in the tire rotation direction R. The lateral groove 2 is a groove that substantially communicates with the circumferential groove 1 in the tire width direction. A rib 3 and a block 4 that are land portions are formed by the circumferential groove 1 and the lateral groove 2.
[0017]
The sipe 5 is a sipe that has one end opened at the edge of the rib 3 or the block 4 and the other end closed and terminated inside the rib 3 or the block 4. The sipe 6 is a sipe whose both ends are terminated inside the block 4. A small hole 7 having a circular shape is provided on an extension line of the sipes 5 and 6, spaced from the closed ends 5 a and 6 a of the sipes 5 and 6.
[0018]
2A is a cross-sectional view taken along line AA ′ shown in FIG. In the figure, a small hole 7 is arranged on the extended line of the sipe 5 at a distance of Ds from the closed end 5 a of the sipe 5. Similarly, FIG. 2B is a cross-sectional view taken along line BB ′ shown in FIG. 1, and a small hole 7 is disposed on the extension line of the sipe 6, separated from the closed end 6 a of the sipe 6 by Ds. ing. In any case, the separation distance Ds is preferably 1 to 5 mm, and the size Dh of the small hole 7 is preferably 1 to 4 mm, and more preferably around 2 mm.
[0019]
In the sipe closed end 5a, it is considered that a stress is generated because deformation is not easy with respect to an external force, and a crack is generated when the stress is repeated. However, in the present invention, the small hole 7 in the vicinity of the sipe closed end 5a is also deformed by an external force. Since the deformation of the sipe closed end 5a is facilitated by the deformation of the small hole 7, the stress applied to the sipe closed end 5a is relieved or the stress distribution is changed. As a result, it is possible to prevent cracks at the sipe closed end 5a. A similar effect is also produced at the sipe closed end 6a.
[0020]
The present invention has an effect of preventing uneven wear (river wear) as well as preventing cracks. In general, in a sipe where one end is an open end and the other end is a closed end, the vicinity of the open end is highly deformable with a high follow-up force to the external force. Does not deform. For this reason, the friction energy near the closed end is larger than that in other portions, so that the amount of wear increases and uneven wear occurs.
[0021]
In the present invention, the small hole 7 provided apart from the sipe closed ends 5a and 6a is deformed by an external force, and deformation near the sipe closed ends 5a and 6a is facilitated. In particular, when the sipe direction is the tire rotation axis direction as in the sipe 5, even if a circumferential external force due to the rolling of the tire is constantly applied, the followability to the external force of the sipe closed end 5a is improved. And uneven wear can be prevented.
[0022]
Stress is generated not only in the tread surface but also in the depth direction. Therefore, if the depth of the small hole is shallow, the effect of stress relaxation becomes low, and the above-described effect may not be sufficiently obtained. Therefore, as shown in FIG. 2, the small hole depth dh is preferably 0.5 times or more of the sipe depth ds.
[0023]
In addition, although the small hole 7 was demonstrated as an example as circular, it may be other shapes, for example, polygons, such as an ellipse, a square, and a hexagon.
[0024]
【The invention's effect】
As described above, in the pneumatic tire according to the present invention, the stress concentration in the vicinity of the sipe closed end can be alleviated by providing the small holes apart from the sipe closed end. As a result, cracks at the sipe closed end can be prevented, and uneven wear can be suppressed.
[Brief description of the drawings]
FIG. 1 is a schematic development view of a pattern of a pneumatic tire according to the present invention.
2A and 2B are cross-sectional views of a sipe and a small hole of a pneumatic tire according to the present invention, in which FIG. 2A is a cross-sectional view along AA ′, and FIG. 2B is a cross-sectional view along BB ′;
[Explanation of symbols]
1 Circumferential groove 2 Horizontal groove 3 Rib 4 Block 5, 6 Sipe 7 Small hole

Claims (4)

In a pneumatic tire having a land portion formed by a groove carved in a tread surface, the land portion including a sipe that ends at least one end inside the land portion,
The sipes spaced from the end terminating within the land portion is small hole provided in said I 1-5 Baidea width of the small holes of the size of the sipe, the sipe, one end of the land portion A pneumatic tire having a sipe that opens at an edge and ends at the other end inside a land portion, and the small hole is provided on an extension line of the sipe .   2. The pneumatic tire according to claim 1, wherein a separation distance from an end portion terminating in the land portion of the sipe to the small hole is 1 to 5 mm.   The pneumatic tire according to claim 1 or 2, wherein the size of the small hole is 1 to 4 mm. The pneumatic tire according to any one of claims 1 to 3 , wherein a depth of the small hole is 0.5 times or more of a depth of the sipe .

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