JP2005001593A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire which suppresses generation and growth of cracks from an expansion part of a sipe even when the space of the sipes is reduced, and enhances durability of the pneumatic tire. <P>SOLUTION: In the pneumatic tire in which a land part divided in a main groove 3 in the tire circumferential direction is formed on a tread surface 1, and a large number of sipes 4 are formed in at least an edge part of the land part, at least one expansion part 4a is formed in the depth direction of the main groove 3 of the sipes 4, and the expansion part 4a is offset in the depth direction of the main groove 3 between the adjacent sipes 4 and 4. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

表１の結果より、本発明タイヤは従来タイヤに比べて、耐偏摩耗を低下させることなくクラックの発生及び成長を抑制していることがわかる。
【００２１】
【発明の効果】
以上説明したように、本発明の空気入りタイヤは、多数のサイプに設けた拡大部の位置を隣り合うサイプ間で互いに主溝の深さ方向にオフセットさせるようにしたので、拡大部同士の間隔が広がり拡大部間でのクラックの発生及び成長を抑制することができる。
【図面の簡単な説明】
【図１】本発明の実施例による重荷重用タイヤのトレッド面を示す一部展開平面図である。
【図２】図１の空気入りタイヤのショルダーリブに形成されたサイプの形状の一例を示す斜視図である。
【図３】図２のサイプの形状を説明するための斜視図である。
【図４】（ａ）及び（ｂ）はそれぞれ本発明のサイプの形状を例示する説明図である。
【図５】（ａ）及び（ｂ）はそれぞれ従来のサイプの形状を示す説明図である。
【符号の説明】
１ トレッド面
２ ショルダーリブ
３ 主溝
４ サイプ
４ａ 拡大部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic tire. More specifically, the present invention relates to a pneumatic tire that can suppress generation of cracks and tears caused by a sipe even when sipe is provided at a high density on a land portion of the tire.
[0002]
[Prior art]
In a pneumatic tire, in order to ensure the occurrence of uneven wear and exercise performance, a thin cut groove called a sipe is formed in a land portion formed on a tread surface. In particular, in heavy-duty tires in which the land portion is composed of circumferential ribs, so-called rail wear occurs along the main groove at the edge portion on the main groove side of the rib. A large number of sipes having a narrow width and the same depth as the main groove are formed, and the occurrence of uneven wear is prevented by reducing the rigidity of the edge portion on the main groove side of the rib. In addition, in an icy and snowy road tire in which the land portion is a block, drainage performance and braking performance on the icy and snowy road surface are secured by forming sipes in the tire width direction on the block.
[0003]
In the tire having the sipe formed in the land portion as described above, there is a problem that cracks are generated due to concentration of stress at the bottom portion in the depth direction of the sipe, and this leads to a rib tear. Conventionally, as a countermeasure against such a problem, an enlarged portion is provided at the bottom of the sipe to disperse the stress (see, for example, Patent Document 1).
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 8-104111
[Problems to be solved by the invention]
However, when a large shearing force is applied to the land portion by constant steering, such as a tire attached to the front wheel of a heavy-duty vehicle, the enlarged portions of adjacent sipe are formed by forming the sipe intervals closely. Since they are in close proximity, there is a problem that cracks are likely to occur in the rubber between the enlarged portions.
[0006]
An object of the present invention is to solve such a conventional problem, and even when the sipe interval is narrowed, the generation and growth of cracks generated from the enlarged portion of the sipe are suppressed, and the durability is further improved. An object of the present invention is to provide a pneumatic tire.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, a pneumatic tire according to the present invention is a pneumatic tire in which a land portion divided into main grooves in the tire circumferential direction is formed on a tread surface, and a plurality of sipes are formed at least at an edge portion of the land portion. In the contained tire, at least one enlarged portion is formed in the depth direction of the main groove of the sipe, and the enlarged portion is offset between adjacent sipes in the depth direction of the main groove. To do.
[0008]
As described above, since the positions of the enlarged portions provided in a large number of sipes are offset from each other in the depth direction of the main groove between adjacent sipes, the gap between the enlarged portions is widened, and cracks are generated between the enlarged portions. And growth can be suppressed.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In each drawing, the same constituent elements are given the same reference numerals, and redundant description is omitted.
[0010]
FIG. 1 shows a part of a tread surface of a heavy duty tire as an example of the pneumatic tire of the present invention. A plurality of main grooves 3 are provided on the tread surface 1, and a plurality of ribs are formed in the main grooves 3. Among these ribs, a large number of one-side opening sipes 4, 4,... Are intermittently arranged in the circumferential direction at the edge portion of the shoulder rib 2 located on the left and right sides on the main groove 3 side. Since the rigidity of the edge portion on the main groove 3 side of the shoulder rib 2 is reduced by the arrangement of the sipe 4, rail wear occurring in this portion can be suppressed.
[0011]
As shown in FIG. 2, the sipe 4 forms enlarged portions 4 a having a diameter larger than the sipe width in the depth direction of the main groove 3, and these enlarged portions 4 a have a depth between the adjacent sipes 4 and 4. The arrangement is offset in the direction. As described above, when the enlarged portion 4a is offset in the depth direction of the main groove 3 with respect to the enlarged portion 4a of the adjacent sipe 4, the number of enlarged portions provided per sipe is plural. There may be. The shape of the enlarged portion 4a in a front view is preferably a circle, an ellipse close to a circle, or a water droplet shape due to a stress dispersing action.
[0012]
Moreover, as shown in FIG. 3, it is preferable that the enlarged part 4a is formed to taper toward the center side of the shoulder rib 2. The depth of the sipe 4 is preferably equal to each other in order to make the rigidity of the edge portion on the main groove 3 side of the shoulder rib 2 uniform in the tire circumferential direction, but the mutual depth is changed as necessary. Also good. Further, it is preferable that the bottom portion of the sipe 4 in the depth direction of the main groove is formed in a curved shape in order to reduce stress concentration.
[0013]
In the example shown in FIG. 4A, the length of the sipe 4 in the depth direction of the main groove is varied, and the enlarged portion 4a formed at the bottom thereof is offset in the depth direction. FIG. 4B shows the sipe 4 having the same depth, and the enlarged portion 4a is offset between the adjacent sipes 4 and 4 in the depth direction. The interval t with respect to the main groove depth direction of the enlarged portion 4a between the adjacent sipes 4 and 4 is not particularly limited, but is preferably 2 to 10 mm.
[0014]
As described above, in the present invention, since the enlarged portion 4a for stress distribution provided in the sipe 4 is offset in the depth direction between the adjacent sipe 4 and 4, the enlarged portion while ensuring a certain distance between the enlarged portions 4a. Since the size of 4a can be increased as much as possible, this can further improve the crack prevention effect.
[0015]
Conventionally, in order to suppress the rail wear of heavy-duty tires, it is usually necessary to arrange the sipe intervals adjacent to each other in a dense arrangement of about 5 mm. Therefore, even if the enlarged portion 4a is formed in the sipe 4, the enlarged portion Since it was necessary to suppress the diameter of 4a to about 2 mm or less, there was a limit to the crack prevention effect. However, since the diameter of the enlarged portion 4a can be increased to some extent by the present invention, the generation and growth of cracks are further increased. It can be suppressed efficiently.
[0016]
The arrangement structure of the enlarged portion 4a with respect to the sipe 4 of the present invention can also be applied to an icy and snowy road tire in which the land portion is a block, and the durability can be further improved. The arrangement of the sipe 4 in the icy and snowy road tire is not particularly limited, and may be a sipe that opens both ends in a main groove that divides the block, and is a sipe that stops one end in the block. Also good.
[0017]
【Example】
The tire size is 295 / 80R22.5, the depth of the main groove 3 is 15 mm, and the shape and arrangement of the sipes are shown in Table 1 on the edge near the center of the heavy-duty pneumatic tire shoulder rib 2 having the tread pattern of FIG. Conventional tires (conventional examples 1 and 2), tires of the present invention (examples 1 and 2) and comparative tires (comparative examples) were produced.
[0018]
The following method with the above 5 types of tires assembled in a rim of size 22.5 × 8.25, filled with 850 kPa of internal pressure and mounted on the front wheel of a 6 × 4 truck, with a load of 34.82 kN applied. A field test was conducted to evaluate crack resistance, crack growth resistance and uneven wear resistance. The results are also shown in Table 1 using an index with Conventional Example 1 being 100. The larger the value, the better.
[0019]
In addition, the space | interval of the tire circumferential direction of the sipe in each tire was 5 mm, and the depth of the sipe was 12 mm. Moreover, the depth of the bottom face of the enlarged portion on the rib surface side in the tire of the present invention was 6 mm.
[Crack resistance test]
The number of cracks generated from the bottom of the sipe after traveling 20,000 km was examined.
[Crack growth resistance test]
Further, after traveling 20,000 km, the number of locations where five or more cracks were connected was examined.
[Uneven wear resistance test]
The vehicle was further traveled, and the distance traveled until the vehicle was hindered by vibration due to the occurrence of uneven wear was measured.
[0020]
[Table 1]

From the results of Table 1, it can be seen that the tire of the present invention suppresses the generation and growth of cracks without reducing the uneven wear resistance as compared with the conventional tire.
[0021]
【The invention's effect】
As described above, in the pneumatic tire of the present invention, the positions of the enlarged portions provided in a large number of sipes are offset from each other in the depth direction of the main groove between adjacent sipes. Can spread and suppress the generation and growth of cracks between the enlarged portions.
[Brief description of the drawings]
FIG. 1 is a partially developed plan view showing a tread surface of a heavy duty tire according to an embodiment of the present invention.
2 is a perspective view showing an example of the shape of a sipe formed on a shoulder rib of the pneumatic tire of FIG. 1. FIG.
3 is a perspective view for explaining the shape of the sipe shown in FIG. 2; FIG.
FIGS. 4A and 4B are explanatory views illustrating the shape of a sipe according to the present invention. FIG.
FIGS. 5A and 5B are explanatory views showing the shape of a conventional sipe, respectively.
[Explanation of symbols]
1 Tread surface 2 Shoulder rib 3 Main groove 4 Sipe 4a Enlarged part

Claims (5)

In a pneumatic tire in which a land portion divided into main grooves in the tire circumferential direction is formed on a tread surface, and a large number of sipes are formed at least at an edge portion of the land portion,
A pneumatic tire in which at least one enlarged portion is formed in the depth direction of the main groove of the sipe, and the enlarged portion is offset between adjacent sipe in the depth direction of the main groove. The pneumatic tire according to claim 1, wherein the land portion is a rib or a block. The pneumatic tire according to claim 2, wherein the enlarged portion is tapered toward the center side of the land portion. The pneumatic tire according to claim 1, 2, or 3, wherein lengths in the depth direction of the main grooves of the sipe are equal to each other. The pneumatic tire according to any one of 1 to 4, wherein the pneumatic tire is a heavy duty radial tire.

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