JP3998574B2 - Pneumatic tire - Google Patents

Description

【００２７】
【発明の効果】
上述したように本発明によれば、ラグ溝の壁面に設けた凹凸部の密度をラグ溝の長手方向中間域で両端部の出入口領域よりも密にし、及び／又は凹凸部の密度をラグ溝の底部域で上部域よりも密にしたことにより、水流の剥離防止を効率的に行って一層排水性を向上することができる。
【図面の簡単な説明】
【図１】本発明の実施形態からなる空気入りタイヤのトレッド面の要部を示す平面図である。
【図２】図１の空気入りタイヤにおけるラグ溝部分を示す斜視図である。
【図３】図２に対応する他の実施形態を示すラグ溝部分を示す斜視図である。
【図４】図２に対応する更に他の実施形態を示すラグ溝部分を示す斜視図である。
【図５】本発明の空気入りタイヤに設けられるディンプルを例示し、（Ａ）は要部の平面図、（Ｂ）は（Ａ）のＸ−Ｘ矢視断面図である。
【図６】本発明の空気入りタイヤに設けられるリブレットを例示し、（Ａ）は要部の平面図、（Ｂ）は（Ａ）のＹ−Ｙ矢視断面図である。
【図７】本発明の空気入りタイヤに設けられる点状突起を例示し、（Ａ）は要部の平面図、（Ｂ）は（Ａ）のＺ−Ｚ矢視断面図である。
【符号の説明】
１ 主溝
２ ラグ溝
３ ブロック
４ ディンプル
５ リブレット
５ｒ 細リブ
６ 点状突起[0001]
[Technical field to which the invention belongs]
The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire in which drainage performance is further improved.
[0002]
[Prior art]
The drainage performance of the pneumatic tire is greatly contributed by the main groove in the tire circumferential direction among the main groove in the tire circumferential direction and the lug groove in the tire width direction provided on the tread surface. However, if the drainage of the lug groove can be improved, the drainage of the entire tire can be further improved. However, when the water flow in the lug groove is observed with a high-speed video camera or the like, it can be seen that a large amount of bubbles are generated on the wall surface of the lug groove and the water flow is separated. The separation of the water flow becomes a great resistance to the water flow, and is an obstacle to further improving the drainage.
[0003]
Conventionally, as a measure for improving the drainage performance of a pneumatic tire, there has been a proposal of forming minute irregularities such as dimples, riblets or dot-like projections on a wall surface such as a main groove (see Patent Document 1). However, there is a limit in achieving a higher drainage effect even if a slight improvement effect can be obtained by simply providing such minute uneven portions on the groove wall surface.
[0004]
[Patent Document 1]
JP 2001-287509 A (claims 11, 14, 15)
[0005]
[Problems to be solved by the invention]
An object of the present invention is to provide a pneumatic tire having further improved drainage performance by improving drainage performance of lug grooves.
[0006]
[Means for Solving the Problems]
The present invention that achieves the above object is a pneumatic tire having a tread surface provided with a main groove extending in the tire circumferential direction and a lug groove communicating with the main groove and extending in the tire width direction. An uneven portion made of dimples, riblets or point-like protrusions is provided, the density of the uneven portion is made dense in the intermediate region in the longitudinal direction of the lug groove, and the entrance / exit regions at both ends are made rougher than the intermediate region. It is what.
[0007]
Another aspect of the present invention for achieving the above object is the pneumatic tire, wherein the tread surface is provided with a main groove extending in the tire circumferential direction and a lug groove communicating with the main groove and extending in the tire width direction. An uneven portion made up of a large number of dimples, riblets, or point-like projections is provided on the wall surface of the wall, the density of the uneven portion is made dense at the bottom region in the depth direction of the lug groove, and the upper region is made rougher than the bottom region. It is characterized by this.
[0008]
According to the present inventors observing the tread surface with a high speed video camera while running the pneumatic tire on the test wet road surface, the water flow flowing into the lug groove from the main groove is more than the entrances at both ends of the lug groove. A large amount of foam is generated mainly in the intermediate region in the longitudinal direction, and more in the bottom region than in the upper region near the tread surface in the groove depth direction of the lug groove. Therefore, it has been found that in the region where a large amount of bubbles are generated, the water flow is separated and resistance is given to the water flow.
[0009]
Based on such knowledge, in the first invention described above, the density of the uneven portions provided on the wall surface of the lug groove is not made uniform, but in the intermediate region in the longitudinal direction of the lug groove than the entrance / exit regions at both ends. By making it dense, it is possible to efficiently prevent separation of the water flow and further improve drainage. Similarly, in the second invention, the density of the concavo-convex portions is made denser in the bottom region of the lug groove than in the upper region, so that the drainage can be further improved.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a tread surface of a pneumatic tire according to an embodiment of the present invention.
[0011]
In the pneumatic tire having the tread surface shown in FIG. 1, the rotation direction is designated in the direction of the arrow R. On the tread surface, a total of four straight main grooves 1 are provided in the tire circumferential direction, with two on the left and right sides across the tire center. From the two main grooves 1 and 1 on the center side, the lug grooves 2 branch to the left and right shoulders, respectively, and are inclined obliquely in the direction opposite to the tire rotation direction. Crossed. A large number of blocks 3 are formed by the main grooves 1 and the lug grooves 2.
[0012]
As shown in FIG. 2, in the lug groove 2 that crosses each block row of the left and right rows, minute uneven portions due to a large number of dimples 4 are formed on the inner wall. For example, as shown in FIG. 5, the dimples 4 are formed from hemispherical concave portions having a depth d, and are distributed with a pitch p therebetween. Thus, the density at which the large number of dimples 4 are unevenly distributed is not uniform over the entire longitudinal direction of the lug groove 2, is the densest in the intermediate region C, and is the entrance / exit areas S at both ends communicating with the main groove 1. S is coarser than the intermediate zone C.
[0013]
As described above, since the water flow separation phenomenon in the lug groove 2 occurs most frequently in the intermediate region C, it is possible to efficiently prevent the water flow separation by increasing the dimple density in the intermediate region C. .
[0014]
In the present invention, the minute uneven portions provided on the wall surface of the lug groove 2 are not limited to dimples, and even the riblet 5 illustrated in FIG. 6 or the dot shape illustrated in FIG. The protrusion 6 may be used. Among these, as shown in FIG. 6, the riblet 5 is formed with a large number of thin ribs 5r arranged in parallel. Further, as shown in FIG. 7, the dot-like projection 6 is formed from a hemispherical convex portion.
[0015]
FIG. 3 shows a case where the riblet 5 is formed on the wall surface of the lug groove 2. As in the case of the dimple of FIG. 1, the density of the riblets 5 (that is, the arrangement density of the thin ribs 5 r) is the most dense in the intermediate region C in the longitudinal direction of the lug groove 2. The areas S and S are rougher than the intermediate area C. The density distribution of such minute uneven portions may be the same when the point-like protrusions 6 are formed in the lug grooves 2.
[0016]
FIG. 4 shows another embodiment of the present invention.
[0017]
In this embodiment, a large number of dimples 4 provided on the wall surface of the lug groove 2 are most dense in the bottom area B of the lug groove 2 and are rougher than the bottom area B in the upper area A near the tread surface. Yes. As described above, the separation phenomenon of the water flow occurs in the bottom region B more than the upper region A of the lug groove 2 in the groove depth direction of the lug groove 2, so that the dimple density in the bottom region B is higher than that of the upper region A. By making it dense, it is possible to prevent separation of a large amount of water flow in the bottom region B.
[0018]
In the embodiment of FIG. 4, the minute uneven portion is not limited to dimples, and even if it is a riblet shown in FIG. 6 or a dot-like projection shown in FIG. Obtainable.
[0019]
Further, if the distribution form of the minute uneven portions in the depth direction of the lug groove in FIG. 4 and the distribution form of the minute uneven portions in the longitudinal direction of the lug groove in FIG. Obtainable.
[0020]
In the present invention, the size of the fine irregularities such as the above-mentioned dimples, riblets and dot-like projections is as follows: the dimple 4 has a depth d, and the riblets and dot-like projections have a height h of 0.05 to 0.5 mm, respectively. It should be a range. Further, the pitch p, which is the distance between the concave and convex portions, is preferably in the range of 0.05 to 0.5 mm for both dimples, riblets, and dot-like projections.
[0021]
When the depth d or the height h is smaller than 0.05 mm or the pitch p is larger than 0.5 mm, the effect of preventing the water flow from peeling off is reduced. Further, if the depth d or the height h is larger than 0.5 mm or the pitch p is smaller than 0.05 mm, the water flow becomes more turbulent and the resistance to the water flow is increased. The improvement effect is reduced.
[0022]
【Example】
The tire size is 195 / 65R15, the toledo pattern is the same as in FIG. 1, and the dimple depth d and the pitch p (density) provided on the wall surface of the lug groove are varied as shown in Table 1. Pneumatic tires of examples and comparative examples were manufactured.
[0023]
For these two types of tires, the hydroplaning generation speed of the method described below was measured, and the results are shown in Table 1.
[0024]
[Hydroplaning test]
When the test tire was mounted on the test vehicle and the hydropool having a water depth of 8 mm was run at a constant speed, the vehicle speed was increased from low to stepwise, and the speed when the hydroplaning phenomenon first occurred was measured.
[0025]
The evaluation of the hydroplaning generation rate was indicated by an index with the hydroplaning generation rate of the comparative example tire being 100. The larger the index value, the higher the hydroplaning generation rate and the better the drainage.
[0026]
[Table 1]

[0027]
【The invention's effect】
As described above, according to the present invention, the density of the uneven portion provided on the wall surface of the lug groove is made denser than the entrance / exit regions at both ends in the longitudinal intermediate region of the lug groove, and / or the density of the uneven portion is set to the lug groove. By making it denser in the bottom area than in the upper area, it is possible to efficiently prevent the separation of the water flow and further improve drainage.
[Brief description of the drawings]
FIG. 1 is a plan view showing a main part of a tread surface of a pneumatic tire according to an embodiment of the present invention.
2 is a perspective view showing a lug groove portion in the pneumatic tire of FIG. 1. FIG.
FIG. 3 is a perspective view showing a lug groove portion showing another embodiment corresponding to FIG. 2;
FIG. 4 is a perspective view showing a lug groove portion showing still another embodiment corresponding to FIG. 2;
5A and 5B illustrate dimples provided in the pneumatic tire of the present invention, in which FIG. 5A is a plan view of a main part, and FIG. 5B is a cross-sectional view taken along line XX in FIG.
6A and 6B illustrate a riblet provided in the pneumatic tire of the present invention, in which FIG. 6A is a plan view of the main part, and FIG. 6B is a cross-sectional view taken along line YY in FIG.
7A and 7B exemplify point-like protrusions provided on the pneumatic tire of the present invention, in which FIG. 7A is a plan view of the main part, and FIG. 7B is a cross-sectional view taken along the line ZZ in FIG.
[Explanation of symbols]
1 Main groove 2 Lug groove 3 Block 4 Dimple 5 Riblet 5r Fine rib 6 Point-like projection

Claims (4)

In a pneumatic tire having a tread surface provided with a main groove extending in the tire circumferential direction and a lug groove communicating with the main groove and extending in the tire width direction, a plurality of dimples, riblets, or point-like projections are formed on the wall surface of the lug groove. The pneumatic tire which provided the uneven | corrugated | grooving part which becomes, and made the density of this uneven | corrugated | grooved part dense in the intermediate area of the longitudinal direction of the said lug groove, and made the entrance / exit area | region of both ends rougher than this intermediate area. 2. The pneumatic tire according to claim 1, wherein the density of the uneven portions is further increased in a bottom region in a depth direction of the lug groove, and an upper region is made rougher than the bottom region. A pneumatic tire having a tread surface provided with a main groove extending in the tire circumferential direction and a lug groove communicating with the main groove and extending in the tire width direction. The pneumatic tire which provided the uneven part which becomes, and made the density of this uneven part dense in the bottom part area | region of the depth direction of the said lug groove, and made the upper area rougher than this bottom part area. The pneumatic tire according to any one of claims 1 to 3, wherein a depth or height of the dimples, riblets, or point-like protrusions is 0.05 to 0.5 mm, and a pitch is 0.05 to 0.5 mm.

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