JP3569081B2 - Pneumatic radial tire - Google Patents

Description

【００２３】
実施例１及び比較例１、２のタイヤにつき、トレッドゴム８に適用したゴム種類、主溝１１、１２の壁面１１ｗ、１２ｗの傾斜角度α（度）、傾斜角度α（度）×３００％モジュラスＭ（ｋｇｆ／ｃｍ^２）それぞれを表２に示す。なお比較例１、２にはトレッドゴム８を除き、他は全て実施例に合せた。これらの実施例１及び比較例１、２のタイヤをそれぞれスポーツカーの４輪に装着し、プロドライバの操縦によりドライ路面及びウエット路面をもつサーキットを５周させる実車テストを実施した。
【００２４】
走行の間のコーナリング中に作用する横Ｇ（横方向加速度）をドライ路面走行時、ウエット路面走行時に分けてハンドリングの手応え（フィーリング）により評価した。評点は１０点を満点としてプロドライバが採点した。テストの間のトレッドゴム欠け発生の有無も合せて観察により記録した。ウエット及びドライ操縦性の評点とトレッドゴム欠け発生の有無とを合せて表２の下段に示す。
【００２５】
【表２】

【００２６】
表２のテスト評点結果より、実施例１のタイヤはウエット路面走行で従来から満足すべき耐ハイドロプレーニング性により優れた操縦性を発揮している比較例１、２タイヤと同等の性能を示す一方、従来はドライ路面のコーナリング走行で不十分なコントロール性を示すに過ぎなかった比較例１、２に対し、実施例１のタイヤはドライ路面走行でも顕著に優れたコントロール性（操縦性）を発揮することが分かる。また切断時伸びを４２０％以上としたトレッドゴムの欠けに対する抵抗力の向上も顕著にあらわれている。
【００２７】
【発明の効果】
この発明の請求項１に記載した発明によれば、ウエット路面の高速走行時に発生し勝ちなハイドロプレーニングを十分に抑制した操縦性と、ドライ路面の急激なコーナリングに際し発生し勝ちなトレッドゴム欠けのなどの故障を伴わずに、急激なコーナリング操作に高度に対応可能な優れたコントロール性とを両立させ得る空気入りラジアルタイヤを提供することができる。
【図面の簡単な説明】
【図１】この発明による空気入りラジアルタイヤの一実施例の左半断面図である。
【図２】図１に示すタイヤの一部正面図である。
【図３】図２に示すＩＩＩ − ＩＩＩ線に沿う主溝の断面図である。
【符号の説明】
１ 空気入りラジアルタイヤ
２ ビード部
３ サイドウォール部
４ トレッド部
４ｔ 踏面
５ ビードコア
６ カーカスプライ
７ ベルト
８ トレッドゴム
１０ 踏面中央区域
１１、１２ 急傾斜主溝
１１ｗ、１２ｗ 主溝壁面
１３、１４ 直状溝
１５、１６ 横溝
θ_１ 、θ_２ 傾斜主溝の赤道面に対する傾斜角度
α 主溝の壁面傾斜角度
ＶＬ 主溝縁を通る踏面への法線
Ｗ 踏面幅
Ｅ 赤道面[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a flat pneumatic radial tire having a flatness of 60% or less, which exhibits excellent maneuverability on both wet road running and dry road running, and particularly, on a circuit running in rainy weather. The present invention relates to a high-performance pneumatic radial tire for sports driving, which achieves a high level of balance between control and dry control.
[0002]
[Prior art]
In recent years, instead of the circumferential main straight groove along the circumference of the tread, which has been considered advantageous in terms of hydroplaning resistance when traveling on wet road surfaces, in recent years it has extended from both sides of the tread center area and has a small angle with respect to the tire equatorial plane. There is a tendency to adopt a tread pattern in which inclined main grooves cross each other to form an arrowhead shape, since the tip (the tire depression side, the same applies hereinafter) formed by the arrowhead main groove has an acute angle. Water splashing in the vehicle traveling direction (forward) is greatly suppressed by the stepping action of the land part from the straight main groove, and as a result, water entering under the rolling tire tread is efficiently drained to the rear and side. This is because it exhibits more excellent hydroplaning resistance.
[0003]
However, among the tires that have this arrow-shaped main groove on the tread surface, the high-performance pneumatic radial tire for sports driving, such as used for circuit driving, is superior in all respects to the tire with the circumferential straight main groove. It was clarified that it did not have any disadvantages but also had disadvantages. The disadvantage is that the land portion with the sharp tip formed by the arrow-shaped cross-shaped main groove is located between the main grooves adjacent to each other in the circumferential direction for each of the main grooves constituting the arrow-shaped main groove in consideration of the improvement of drainage. It is derived from a diamond-shaped or similar block formed by communicating sub-grooves.
[0004]
In this block, it is necessary to make the inclination angle of the arrow-shaped intersection main groove with respect to the tire equatorial plane as small as possible in order to ensure high hydroplaning resistance. The smaller the inclination angle, the wider the block width Becomes narrower. As a result, it is natural that extremely large lateral forces frequently act on the tire treads during circuit running that requires turning close to the limit, and narrow blocks will undergo large deformation with respect to the large lateral force input at that time. A disadvantage was found that forced cornering forces could not be generated, and therefore maneuverability was insufficient and controllability was lacking.
[0005]
[Problems to be solved by the invention]
Therefore, the invention described in claim 1 of the present invention provides a tread portion with tread-shaped cross main grooves to ensure sufficient hydroplaning resistance when running on a wet road surface, and then when running on a general dry road surface. It is another object of the present invention to provide a pneumatic radial tire that has sufficient controllability and can exhibit excellent controllability particularly when traveling on a circuit on a dry road surface.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the invention described in claim 1 of the present invention comprises a pair of bead portions, a pair of sidewall portions, and a tread portion, and these portions are reinforced between bead cores embedded in the bead portions. A carcass ply that becomes a rubber coating of at least one ply of radially arranged cords, and a belt that strengthens the tread portion at the outer periphery of the carcass ply. A pneumatic radial tire having an organic fiber code layer,
Extend toward the tire equatorial plane respectively from both ends of the central region of the tread surface, a large number to such a steep angle of 30 ° or less, respectively with respect to the equator plane has a main groove of the, these main grooves Each intersects with the other two main grooves in an arrow-like manner, and the portions of each main groove located at both ends of the central section have the steep slope in the same direction with respect to the equatorial plane. It is bent at an inclination angle larger than the angle to be a horizontal groove-shaped main groove portion, and this horizontal groove-shaped main groove portion communicates with one of the straight grooves provided on both sides of the tread surface,
The product (α × M) of the wall surface inclination angle (α (degree)) appearing in the tire section of the steeply inclined main groove and the 300% modulus (M (kgf / cm ² )) of the tread rubber in the tread portion is α A pneumatic radial tire having a flatness of 60% or less, characterized by satisfying xM> 900 and having an elongation at break of tread rubber of 420% or more.
[0007]
Here, the central area of the tread tread refers to two areas in total, one area on both sides sandwiching the tire equatorial plane among the four areas divided into four equal tread widths. The main grooves extending at a steep inclination angle toward the tire equatorial plane from the positions near the outer ends of these areas, respectively, are inclined in the same direction on one side and the other side of the tire equatorial plane, and the main groove on one side is inclined. The groove and the inclined main groove on the other side intersect in an arrow shape in the central area, and the direction of the arrow is the same over the entire circumference of the tread surface. As is clear from the above, the arrow-shaped cross main groove has directionality, and therefore, the pneumatic radial tire according to the present invention specifies the direction of rotation. In addition, the number of intersections of the main groove is not limited to one, but may be two or more as necessary.
[0008]
The inclination angle α (degree) of the wall surface of the arrow-shaped cross main groove is defined as the angle formed by the normal of the tread surface passing through the groove edge and the line of the wall surface in a cross section of a plane including the rotation axis of the tire. This is different from the inclination angle of the groove cross section that appears on a plane orthogonal to the groove, which has been conventionally used. This wall surface inclination angle α (degree) is applied to both wall surfaces.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of a pneumatic radial tire according to the present invention will be described in detail below with reference to FIGS.
1 is a left half sectional view of the tire, FIG. 2 is a plan view of a tread pattern formed on a tire tread, and FIG. 3 is a steeply inclined main line along a line III-III orthogonal to the tire equatorial plane E of FIG. It is sectional drawing of a groove part.
[0010]
In FIG. 1, a pneumatic radial tire 1 includes a pair of bead portions 2 (only one side is shown), a pair of sidewall portions 3 (only one side is shown), and a tread portion 4, and these portions are embedded in the bead portion. The carcass ply 6 includes one or more plies (two plies in the illustrated example) that reinforce the bead cores 5 and a belt 7 that reinforces a tread portion on the outer periphery of the carcass plies 6. The belt 7 has two or more layers (two layers in the illustrated example) on the carcass ply 6 side and one or more layers (one layer in the illustrated example) spirally wound around the outer periphery of the layer 7a. Layer 7b. The cord crossing layer 7a is formed by rubber coating of steel cord or polyamide fiber cord, and the spirally wound layer 7b is formed by rubber coating of 6-nylon cord or 6,6-nylon cord. Further, a tread rubber 8 is arranged on the outer periphery of the belt 7 according to a customary practice.
[0011]
In FIGS. 1 and 2, the width W of the tread surface 4t of the tread portion 4 forms a curve forming both end sides of the tread surface in the case of the round shoulder shown in FIG. The distance between the intersection points P with the extension lines of the arcs. Here, one section on both sides of the tire equatorial plane (hereinafter, abbreviated as equatorial plane) E of the four sections divided into four equal sections of the tread width W is referred to as a central section 10 in total. FIG. 1 is a sectional view taken along the line II of FIG.
[0012]
The main grooves 11, 12 extend across the equatorial plane E in this example from both ends of the central section 10 toward the equatorial plane E, respectively. At this time, the main grooves 11 and 12 are arranged in an arrow-shaped arrangement with steep inclination angles θ ₁ and θ ₂ within 30 ° or less, preferably 10 to 30 ° with respect to the equatorial plane E, respectively. That is, the main grooves 11, 12 are arranged so as to extend from both sides of the equatorial plane E toward the equatorial plane E so as to draw a V-shape.
[0013]
Here, the inclination angles θ ₁ and θ ₂ of the main grooves 11 and 12 with respect to the equatorial plane E are measured at the groove edges when the main grooves 11 and 12 have the same groove width near the equatorial plane E, and when the groove width changes. Is measured with a line connecting the center of the groove width. In FIG. 2, the inclination angles θ ₁ and θ ₂ are indicated by lines L ₁ and L ₂ connecting the center of the groove width. Here, the inclination angles θ ₁ and θ ₂ can be set to satisfy θ ₁ = θ ₂ , θ ₁ > θ ₂ , and θ ₁ <θ ₂ . Although the illustrated main grooves 11 and 12 are straight, they may be arcuate or curved having a large radius of curvature.
[0014]
The illustrated main grooves 11 and 12 intersect each other in an arrowhead shape at two places, and each intersection position is near the equatorial plane E. For the sake of convenience, the main grooves 11 and 12 are divided into main grooves 11a and 11b and main grooves 12a and 12b, respectively, so that the main grooves 11a and 11b and the main groove 12b and the main groove 11b are formed. And the main groove 12a form a land portion having a sharp tip.
[0015]
In order to maintain good drainage, the tread pattern shown in FIG. 2 first has straight grooves 13 and 14 on both sides of the tread 4t, and then the main grooves 11 and 12 located on both sides of the central section 10 are inclined at an angle. It is bent at an inclination angle larger than θ ₁ and θ ₂ to form the horizontal groove-shaped main groove portions 11c and 12c. The horizontal groove-shaped main groove portions 11c and 12c communicate with the straight grooves 13 and 14, respectively. The end portions of the grooves 11 and 12 similarly connect the lateral grooves 15 and 16 to the straight grooves 13 and 14 as shown in the figure.
[0016]
When the tire 1 rotates in the rotation direction indicated by the arrow in FIG. 2, the land portions having the sharp tips formed by the main grooves 11 and 12 among the various grooves described above move through the water film, as if a bow of a navigating ship. A draining operation similar to that described above is performed, and the separated water flows inside the main grooves 11 and 12 and is efficiently drained to both sides of the tire and to the rear of the rotation. Hydroplaning resistance is remarkably improved as compared with the main groove.
[0017]
However, the sharp land part and the narrow land part block that follows are likely to undergo large deformation due to sharp cornering on dry road surface, and as a result it is difficult to generate the expected cornering force as mentioned earlier. It is. Therefore, referring to FIG. 3, the angle α between the groove wall surfaces 11w, 12w of the main grooves 11, 12 appearing in a cross section by a plane orthogonal to the equatorial plane E and the normal VL of the tread surface 4t passing through the groove edge, that is, the groove The product α × M of the inclination angle α (degree) of the wall surfaces 11 w and 12 w and the 300% modulus M (kgf / cm ² ) of the tread rubber 8 needs to exceed 900. At this time, the inclination angle α (degree) of the groove wall surfaces 11w and 12w is not always the same in the same main groove and between the main grooves, and an appropriate value may be selected within a range satisfying α × M> 900. it can.
[0018]
However, the 300% modulus M (kgf / cm ² ) is desirably as high as possible in terms of generation of cornering force, but it is necessary to keep the value within a range that does not practically impair productivity and workability during production. And, from the viewpoint of maintaining good riding comfort, 140 kgf / cm ² or less is preferable. For this reason, it is desirable that the wall inclination angle α of the main grooves 11 and 12 be about 6.43 degrees or more. Further, in order to prevent the chipping of the block at the time of sharp cornering, the elongation at the time of cutting of the tread rubber 8 needs to be 420% or more.
[0019]
In time the above elongation at break 420% or more, the inclination angle α of the value of (degree) and the 300% modulus M (kgf / cm ²⁾ greater than 900 when the was multiplied by 300% modulus M (kgf / cm ²⁾ The sharply land portion formed by the tread rubber 8 and the main grooves 11 and 12 having the wall surface inclination angle α (degree) has a sharp edge even when the vehicle corners sharply, even if the land portion width is narrow. Demonstrates sufficient rigidity against the lateral force acting on the land, and consequently suppresses the amount of deformation of the land, and withstands even under a large deformation input and has sufficient side force without exhibiting the "settling phenomenon". In addition, a cornering force can be generated. Needless to say, the steering response is also greatly improved.
[0020]
The tread that satisfies the wall surface inclination angle α and the physical properties of the tread rubber 8 irrespective of whether the sharp land portion is a block as shown in FIG. 2 or a block having another diamond shape or a shape similar thereto. The pneumatic radial tire with the pattern can exhibit the same excellent maneuverability based on the excellent hydroplaning resistance as the conventional tire on wet road surface without trouble such as chipping of tread rubber, and at the same time on dry road surface It is possible to exhibit a high degree of controllability based on the cornering force characteristic which is remarkably superior to conventional tires, and it is possible to provide a so-called all-weather type high-performance tire that is suitable for circuit running. When α × M ≦ 900, the dry road surface performance becomes insufficient, which is not suitable for the purpose of the present invention.
[0021]
【Example】
A pneumatic radial tire for a passenger car, having a size of 205 / 55R16. The structure is in accordance with FIGS. 1 to 3, and the carcass ply 6 is a rubber coating of a two-ply radially arranged polyester cord, and the belt 7 is a two-layer steel cord. It comprises a cross layer 7a and a single layer of spirally wound 6,6-nylon cord 7b. The tread width W is 180 mm, and thus the width of the central section 10 is 45 mm × 2, that is, 90 mm. Two types of tread rubber 8, rubber A and rubber B, were prepared. Table 1 shows these 300% modulus M (kgf / cm ² ) and elongation at break (%).
[0022]
[Table 1]

[0023]
For the tires of Example 1 and Comparative Examples 1 and 2, the rubber type applied to the tread rubber 8, the inclination angles α (degree) of the wall surfaces 11w and 12w of the main grooves 11, 12 and the inclination angle α (degree) × 300% modulus M (kgf / cm ² ) is shown in Table 2. In Comparative Examples 1 and 2, except for the tread rubber 8, all the other components were the same as those in Examples. An actual vehicle test was conducted in which the tires of Example 1 and Comparative Examples 1 and 2 were mounted on four wheels of a sports car, respectively, and five tracks of a circuit having a dry road surface and a wet road surface were driven by a professional driver.
[0024]
Lateral G (lateral acceleration) acting during cornering during running was evaluated by feeling of handling separately for running on a dry road surface and running on a wet road surface. The professional driver scored a maximum of 10 points. The presence or absence of tread rubber chipping during the test was also recorded by observation. The lower part of Table 2 shows the evaluation results of wet and dry maneuverability and presence / absence of occurrence of tread rubber chipping.
[0025]
[Table 2]

[0026]
From the test scores shown in Table 2, the tire of Example 1 shows the same performance as the tires of Comparative Examples 1 and 2, which exhibit excellent maneuverability due to hydroplaning resistance which has been conventionally satisfied on a wet road surface. On the other hand, the tire of Example 1 shows remarkably excellent controllability (maneuverability) even on a dry road surface, as compared with Comparative Examples 1 and 2, which conventionally showed only insufficient controllability on cornering on a dry road surface. You can see that In addition, the improvement in resistance to chipping of the tread rubber having an elongation at break of 420% or more is also remarkably exhibited.
[0027]
【The invention's effect】
According to the invention described in claim 1 of the present invention, the maneuverability which sufficiently suppresses the hydroplaning which is likely to occur during high-speed running on a wet road surface, and the tread rubber chip which is likely to occur when sharp cornering on a dry road surface is used. Thus, it is possible to provide a pneumatic radial tire that can achieve both excellent controllability and high controllability to abrupt cornering operation without failure such as failure.
[Brief description of the drawings]
FIG. 1 is a left half sectional view of an embodiment of a pneumatic radial tire according to the present invention.
FIG. 2 is a partial front view of the tire shown in FIG.
FIG. 3 is a cross-sectional view of the main groove taken along line III-III shown in FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Pneumatic radial tire 2 Bead part 3 Side wall part 4 Tread part 4t Tread surface 5 Bead core 6 Carcass ply 7 Belt 8 Tread rubber 10 Center surface of tread 11, 12 Steeply inclined main grooves 11w, 12w Main groove wall surfaces 13, 14 Straight grooves 15, 16 Lateral grooves θ ₁ , θ ₂ Inclination angle of the inclined main groove with respect to the equatorial plane α Wall inclination angle of the main groove VL Normal line W to the tread passing through the edge of the main groove Tread width E Equatorial plane

Claims (1)

A carcass ply comprising a pair of beads, a pair of sidewalls, and a tread portion, and a rubber cascade of one or more ply radially arranged cords for reinforcing the respective portions between bead cores embedded in the bead portion, and an outer periphery thereof A belt that strengthens the tread portion with a tread portion of a tread portion of a pneumatic radial tire having two or more cord cross layers and an organic fiber code layer spirally wound around the outer periphery of the belt. of extending toward the tire equatorial plane respectively from both ends of the central region, it has a main groove of the number to a rapid slope angle of 30 ° or less, respectively with respect to the equator plane present, each of these main grooves, The other two main grooves intersect each other in an arrow shape, and the portions of the respective main grooves located at both ends of the central area are oriented in the same direction with respect to the equatorial plane. Is a folded and the transverse groove-shaped main groove portion with greater inclination angle than the inclination angle, the lateral groove-shaped main groove portion communicates with one of the straight grooves provided in the tread surface sides,
The product (α × M) of the wall surface inclination angle (α (degree)) appearing in the tire section of the steeply inclined main groove and the 300% modulus (M (kgf / cm ² )) of the tread rubber in the tread portion is α A pneumatic radial tire having a flatness of 60% or less, characterized by satisfying × M> 900 and having an elongation at break of tread rubber of 420% or more.

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