JP2004196145A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire with a drain property further improved by improving a drain property of a lug groove. <P>SOLUTION: This pneumatic tire has a main groove 1 extending in a tire peripheral direction and a lug groove 2 communicated with the main groove and extending in a tire width direction on a tread face. Projection and indentation parts comprising a large number of dimples 4, riblets 5 or dot-like protrusions 6 are provided on a wall face of the lug groove 2. Density of the projection and indentation parts is made dense in an intermediate area C in a longitudinal direction of the lug groove 2, and is made at inlet and outlet areas S, S on both ends rougher than the intermediate area C. Projection and indentation parts comprising a large number of the dimples 4, the riblets 5 or the dot-like protrusions 6 are provided on the wall face of the lug groove 2. Density of the projection and indentation parts is made dense at a bottom area B in a depth direction of the lug groove 2, and is made at an upper area A rougher than at the bottom area B. <P>COPYRIGHT: (C)2004,JPO&NCIPI

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 OF THE INVENTION
The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire with further improved drainage performance.
[0002]
[Prior art]
Of the main groove in the tire circumferential direction and the lug groove in the tire width direction provided on the tread surface, the main groove particularly in the tire circumferential direction greatly contributes to drainage of the pneumatic tire. However, if the drainage of the lug grooves 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, a large amount of bubbles are generated on the wall surface of the lug groove, and it can be seen that the water flow has separated. Since the separation of the water flow causes a large resistance to the water flow, it is an obstacle to further improving drainage.
[0003]
2. Description of the Related Art Conventionally, as a measure for improving drainage of a pneumatic tire, there has been a proposal to form minute uneven portions such as dimples, riblets or point-like projections on a wall surface such as a main groove (see Patent Document 1). However, merely providing such a small uneven portion on the groove wall surface can provide a slight improvement effect, but there is a limit in achieving a higher drainage effect.
[0004]
[Patent Document 1]
JP 2001-287509 A (Claims 11, 14, and 15)
[0005]
[Problems to be solved by the invention]
An object of the present invention is to provide a pneumatic tire with further improved drainage by improving drainage of lug grooves.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a pneumatic tire provided with a main groove extending in a tire circumferential direction on a tread surface and a lug groove communicating with the main groove and extending in a tire width direction. Of the dimples, riblets or point-like projections, the density of the irregularities is made dense in the middle region in the longitudinal direction of the lug groove, and the entrance and exit regions at both ends are made coarser than the middle region. It is assumed that.
[0007]
Another aspect of the present invention that achieves the above object is a pneumatic tire provided with a main groove extending in a tire circumferential direction on a tread surface and a lug groove communicating with the main groove and extending in a tire width direction. A number of dimples, riblets or irregularities formed of point-like projections were provided on the wall surface, the density of the irregularities was increased in the bottom region in the depth direction of the lug groove, and the upper region was roughened than the bottom region. It is characterized by the following.
[0008]
While the present inventors observed 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 was larger than the entrance at both ends of the lug groove. A large amount of bubbles is generated mainly in the middle region in the longitudinal direction, and more in the bottom region than in the upper region near the tread surface in the 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 separates to give resistance to the water flow.
[0009]
Based on such knowledge, the first aspect of the present invention does not make the density of the uneven portion provided on the wall surface of the lug groove uniform, but rather makes the lug groove in the longitudinal middle area more than the entrance and exit areas at both ends. By increasing the density, the separation of the water flow can be efficiently prevented, and the drainage can be further improved. Similarly, in the second aspect of the present invention, drainage can be further improved by making the density of the concavo-convex portions denser in the bottom region of the lug groove than in the upper region.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 shows a tread surface of a pneumatic tire according to an embodiment of the present invention.
[0011]
The rotation direction of the pneumatic tire having the tread surface shown in FIG. On the tread surface, a total of four straight main grooves 1 are provided in the tire circumferential direction, two on the left and the other on the right and left sides of the tire center. From the two main grooves 1 and 1 on the center side, a lug groove 2 branches to the left and right shoulder sides, and is inclined obliquely in the anti-rotation direction of the tire. Intersect. A large number of blocks 3 are formed by these main grooves 1 and lug grooves 2.
[0012]
As shown in FIG. 2, minute dimples formed by a large number of dimples 4 are formed on the inner wall of the lug groove 2 which crosses each block row of two right and left rows. The dimples 4 are formed, for example, from hemispherical concave portions having a depth d, as shown in FIG. 5, and are distributed at a pitch p between each other. The density at which the large number of dimples 4 are unevenly distributed is not uniform throughout the longitudinal direction of the lug groove 2, but is the densest in the intermediate region C, and the entrance and exit regions S, at both ends communicating with the main groove 1. S is coarser than the middle area C.
[0013]
As described above, the separation of the water flow in the lug groove 2 occurs most frequently in the intermediate region C. Therefore, by increasing the dimple density in the intermediate region C, the separation of the water flow can be efficiently prevented. .
[0014]
In the present invention, the minute uneven portion provided on the wall surface of the lug groove 2 is not limited to a dimple, and may be a riblet 5 as illustrated in FIG. 6 or a dot-like as illustrated in FIG. The protrusion 6 may be used. As shown in FIG. 6, the riblet 5 has a large number of narrow ribs 5r arranged in parallel. Further, the point-like projection 6 is formed of a hemispherical convex portion as shown in FIG.
[0015]
FIG. 3 shows a case where the riblets 5 are formed on the wall surfaces of the lug grooves 2. As in the case of the dimple of FIG. 1, the density of the riblets 5 (that is, the arrangement density of the fine ribs 5r) is the highest in the longitudinal middle area C of the lug groove 2, and the entrances at both ends communicating with the main groove 1. The areas S, S are coarser than the intermediate area C. The density distribution of such minute uneven portions may be the same when the dot-like projections 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 become densest in the bottom region B of the lug groove 2 and coarser in the upper region A close to the tread surface than in the bottom region B. I have. As described above, the separation phenomenon of the water flow occurs more in the bottom region B than in the upper region A of the lug groove 2 in the groove depth direction of the lug groove 2, so that the dimple density of 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 fine unevenness is not limited to the dimple, and the same effect of improving drainage can be obtained even if it is a riblet shown in FIG. 6 or a dot-like projection shown in FIG. Obtainable.
[0019]
Further, by combining the distribution form of the fine unevenness in the lug groove depth direction in FIG. 4 with the distribution form of the fine unevenness in the lug groove longitudinal direction in FIG. Obtainable.
[0020]
In the present invention, as for the size of the minute irregularities such as the dimples, riblets, and point-like projections described above, the depth d of the dimple 4 and the height h of the riblets and the point-like projections are each 0.05 to 0.5 mm. It is good to set it in the range. Further, the pitch p, which is the interval between the concave and convex portions, is preferably in the range of 0.05 to 0.5 mm for all the dimples, riblets, and point-like projections.
[0021]
When the depth d or the height h is smaller than 0.05 mm, or when the pitch p is larger than 0.5 mm, the effect of preventing the separation of the water flow is reduced. When the depth d or the height h is larger than 0.5 mm or the pitch p is smaller than 0.05 mm, the turbulence of the water flow increases, and the resistance to the water flow increases. The effect of the improvement is reduced.
[0022]
【Example】
The tire size is 195 / 65R15, the toledo pattern is the same as that of FIG. 1, and the depth d and the pitch p (density) of the dimples provided on the wall surfaces of the lug grooves are different 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 was measured by the method described below, and the results are shown in Table 1.
[0024]
[Hydroplaning test]
When the test tire was mounted on a test vehicle and the vehicle traveled at a constant speed in a hydropool having a depth of 8 mm, the vehicle speed was increased stepwise from a low speed, and the speed at which the hydroplaning phenomenon first occurred was measured.
[0025]
The evaluation of the hydroplaning occurrence speed was indicated by an index with the hydroplaning occurrence speed of the tire of the comparative example being 100. The larger the index value, the higher the hydroplaning generation speed and the better the drainage property.
[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 region at both ends in the longitudinal middle region of the lug groove, and / or the density of the uneven portion is reduced. By making the bottom region more dense than the upper region, the separation of the water flow can be efficiently prevented, and the drainage can be further improved.
[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.
FIG. 2 is a perspective view showing a lug groove portion in the pneumatic tire of 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 a dimple provided in the pneumatic tire of the present invention, wherein FIG. 5A is a plan view of a main part, and FIG. 5B is a cross-sectional view of FIG.
6A and 6B illustrate a riblet provided in the pneumatic tire of the present invention, wherein FIG. 6A is a plan view of a main part, and FIG. 6B is a cross-sectional view of FIG.
7A and 7B illustrate a point-like projection provided on the pneumatic tire of the present invention, wherein FIG. 7A is a plan view of a main part, and FIG. 7B is a cross-sectional view of FIG.
[Explanation of symbols]
Reference Signs List 1 main groove 2 lug groove 3 block 4 dimple 5 riblet 5r thin rib 6 point-like projection

Claims (4)

In a pneumatic tire provided with a main groove extending in the tire circumferential direction on the tread surface and a lug groove communicating with the main groove and extending in the tire width direction, a large number of dimples, riblets or point-like projections are formed on the wall surface of the lug groove. A pneumatic tire in which uneven portions are provided, the density of the uneven portions is made dense in an intermediate region in the longitudinal direction of the lug groove, and entrance and exit regions at both ends are made coarser than the intermediate region. 2. The pneumatic tire according to claim 1, wherein the density of the uneven portion is further increased in a bottom region in a depth direction of the lug groove, and an upper region is coarser than the bottom region. In a pneumatic tire provided with a main groove extending in the tire circumferential direction on the tread surface and a lug groove communicating with the main groove and extending in the tire width direction, a large number of dimples, riblets or point-like projections are formed on the wall surface of the lug groove. A pneumatic tire in which uneven portions are provided, the density of the uneven portions is made dense in a bottom region in the depth direction of the lug groove, and an upper region is made coarser than the bottom region. The pneumatic tire according to any one of claims 1 to 3, wherein the dimples, riblets or point-like projections have a depth or height of 0.05 to 0.5 mm and a pitch of 0.05 to 0.5 mm.

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