JP3569387B2 - Flat radial tire with asymmetric tread pattern on asymmetric profile - Google Patents

Description

【００１２】
実施例タイヤは、左右対称プロフィルに対称トレッドパターンを具えた比較例１よりアクァプレーニング性能が若干劣るが、コーナーリングパワー、最大コーナリングフォース、乾燥路旋回性能、ワンダリング性能が優れており、対称プロフィルに非対称トレッドパターンを具えた比較例２よりコーナーリングパワー、最大コーナリングフォース、乾燥路旋回性能、ワンダリング性能が優れ、他の特性は同等であり、プロフィルを非対称にすることにより乾燥路旋回性能及びワンダリング性能が、他の特性を低下することなく、改良されることが認められる。しかし、内側ショルダー部の曲率半径を外側ショルダー部の曲率半径より大きくした比較例３は全ての特性が比較例１より劣る。対称プロフィルにトレッド外半面ボイド比とトレッド内半面ボイド比が同じである非対称トレッドパターンを具えた比較例４及び５はコーナリングパワーとワンダリング性能が比較例１より劣る。比較例タイヤはいずれも、本発明が改良しょうとした性能が、コントロールタイヤより低下した。
【００１３】
【発明の効果】
自動車に装着する際に表にされる側の接地面の端から赤道までのトレッド外半面が幅を２等分して外側ショルダー部と外側メディエイト部に分け、接地面の他方の端から赤道からまでのトレッド内半面が幅を２等分して内側ショルダー部と内側メディエイト部に分けて、内側ショルダー部の曲率半径を外側ショルダー部の６０〜９０％にし、メディエイト部ボイド比＞ショルダー部ボイド比、トレッド外半面ボイド比＜トレッド内半面ボイド比の関係を満たすことにより、ワイピングが横力の反力を大きくして限界走行性能を維持しながら、コーナリングパワーを大きくし、常用走行時の性能及び一般的な湿潤路面における旋回性能並びにワンダリング性能が向上する。
【図面の簡単な説明】
【図１】本発明のラジアルタイヤの断面図
【図２】本発明のラジアルタイヤの接地面の部分展開図
【符号の説明】
１ カーカス
３ トレッドゴム
６ 縦溝
６ａ 隣り合った縦溝
６ｂ 隣り合った縦溝
６ｃ 隣り合った縦溝
７ トレッド外半面
８ トレッド内半面
９ 外側ショルダー部
１０ 外側メディエイト部
１１ 内側ショルダー部
１２ 内側メディエイト部
１３ 横溝
１４ 横溝
１５ 横溝
１６ ブロック
１７ ブロック
Ｅｏ 表にされる側の接地面の端
Ｅｉ 反対側の接地面の端
Ｃ 赤道
Ｒｏ 外側ショルダー部の曲率半径
Ｒｉ 内側ショルダー部の曲率半径[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a flat radial tire, and more particularly, to make the crown radius of curvature and tread pattern of the tread different on the left and right of the equator to increase cornering power and cornering force while maintaining excellent road grip performance, and to improve wandering performance. The present invention relates to a flat radial tire having improved flatness, particularly a radial tire having a flatness of 60% or less.
[0002]
[Prior art]
Generally, radial tires used in high-speed passenger cars have a low flatness, and have straight or zigzag longitudinal grooves extending in the tire circumferential direction on the tread and extend at right angles or inclines with respect to the tire circumferential direction. A tread pattern in which blocks partitioned by horizontal grooves connecting the grooves are arranged, that is, a so-called block tread pattern is provided. Among these flat radial tires, to improve the steering stability, when mounting on a car, change the tread pattern design on the left and right of the equator of the tire by pre-determining the side to be attached to the front of the side, In some cases, the void ratio, which represents the ratio of the area of the opening of the groove to the area where the tread surface was developed as a percentage, was different between the left and right of the equator. Most of them have a relatively small void ratio on the outer half of the tread from the equator to the end of the tread contact surface on the side that is exposed when mounted on the car to increase grip performance on dry road surfaces, The void ratio of the inner half surface of the tread was made larger than that of the outer half surface of the tread to improve drainage, thereby improving grip performance on wet road surfaces.
[0003]
Tires with an asymmetrical tread pattern with a large void ratio on the inner half of the tread have better turning performance than tires with a symmetrical tread pattern when turning sharply on a dry road surface at the limit where skidding occurs. However, running on a dry road with a gentle curve, so-called normal running, and turning performance when reaching a limit running on a lightly moist road were inferior to those of a tire having a symmetric tread pattern. This is because, when turning, if the slip angle given to the tire is small, the inside of the tread equator (hereinafter, when mounted on a car, the front side is visible outside and the back side is inside This is due to the fact that the rigidity of the portion is reduced due to the increase in the void ratio, and the cornering power generated as a reaction force of the lateral force in the inner portion is reduced.
[0004]
[Problems to be solved by the invention]
While maintaining the excellent marginal driving performance of conventional tires with an asymmetrical tread pattern, the cornering power is increased to improve steering stability during normal driving and turning performance on general wet road surfaces that do not reach the limit driving. An object of the present invention is to provide a tire having a tread pattern.
[0005]
[Means for Solving the Problems]
The present invention reduces the crown radius of curvature on the inner side of the equator of the tread when mounted on an automobile, and causes the tread surface of the grounded portion of the rotating tire to instantaneously rotate due to friction due to friction. Then, the road surface is wiped off and then quickly returned to a predetermined position, so-called wiping is increased, thereby increasing the initial value of the cornering force and improving the turning performance on a wet road surface.
That is, in the present invention, the carcass is reinforced with at least one layer of a carcass ply having a large number of cords arranged at right angles to the tire circumferential direction and rubberized on both sides, and a crown portion of the carcass is arranged in the tire circumferential direction. It is covered with a tread rubber provided with a block pattern formed by a plurality of extending vertical grooves and a number of horizontal grooves connecting the vertical grooves, the side portion is covered with a sidewall rubber, and a tire circumference is provided between the tread rubber and the carcass. A belt in which at least two layers of a belt ply rubberized on both sides are arranged by arranging a large number of cords obliquely with respect to the direction is arranged, and the surface to be turned to the front side when mounted on an automobile is defined. In a flat radial tire, the outer half surface of the tread from the end of the ground contact surface on the front side to the equator when the normal internal pressure is filled and the design load is applied has a width of 2 or more. The inner half of the tread from the other end of the tread to the equator is divided into two equal halves, the inner half of the tread from the other end of the tread to the equator is divided into an inner shoulder and an inner mediate. The radius of curvature of the portion is set to 60 to 90% of the radius of curvature of the outer shoulder portion, and the outer mediate portion and the inner mediate portion are defined by a number of lateral grooves connecting longitudinal grooves extending in the circumferential direction of the tire and adjacent longitudinal grooves. The outer shoulder part has a rib with one end opening at the tread end, the other end provided with a number of lateral grooves closed in the shoulder part, and the inner shoulder part has one end at the tread. It has a row of blocks that are open at one end and are partitioned by a number of horizontal grooves, the other end of which is open to a vertical groove. Both the inner half surface of the tread and the outer half surface of the tread have a shoulder portion void ratio. Ieito section smaller than the void ratio of and is flat radial tire comprising an asymmetric tread pattern asymmetric profile, wherein the void ratio of the inner tread half is greater than the void ratio of the tread outer half.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
In the radial tire of the present invention, the carcass is symmetrical with respect to the center line, but the profile and the tread pattern are asymmetrical. The details of the radial tire of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view showing a section of the radial tire of the present invention, and FIG. 2 is a partially developed view of a ground contact surface. In FIG. 1, a carcass 1 is reinforced with at least one layer of a carcass ply 2 having a large number of cords arranged at right angles to a tire circumferential direction and rubberized on both sides, and a crown portion is covered with a tread rubber 3. A side portion is covered with a side wall rubber 4, and a number of cords arranged at an angle of 15 to 30 ° with respect to the tire circumferential direction are arranged between the carcass 1 and the tread rubber 3. The superposed belt 5 is arranged so that at least two layers have the cords inclined in opposite directions. The tread rubber 3 is provided with a straight or zigzag vertical groove 6 extending in the tire circumferential direction and a horizontal groove (not shown) extending at a right angle or inclined to the circumferential direction. When a design load is applied by filling the internal pressure specified by public standards such as JIS, JATMA Yearbook, TRA, etc., the tread from the end Eo of the ground surface on the side shown when mounting on a car to the equator C The outer half surface 7 is divided into an outer shoulder portion 9 and an outer mediate portion 10 by dividing the width into two equal parts, and the tread inner half surface 8 from the end Ei of the contact surface on the opposite side to the equator C is divided into two equal parts. It is divided into an inner shoulder portion 11 and an inner mediate portion 12. The radius of curvature Ri of the inner shoulder portion 11 is set to 60 to 90% of the radius of curvature Ro of the outer shoulder portion 9. As shown in FIG. 2, the outer shoulder portion 9 has a rib in which one end is open at the tread end and the other end is provided with a large number of transverse grooves 13 closed at a predetermined pitch in the outer shoulder portion 9. The outer mediate part 10 and the inner mediate part 12 extend obliquely in the circumferential direction connecting the adjacent vertical grooves 6a, 6b, 6c, and form a row of blocks 16 defined by a large number of horizontal grooves 14 arranged at a predetermined pitch. Equipped. If necessary, an auxiliary groove 18 for connecting the lateral grooves 14 adjacent in the circumferential direction can be provided. The inner shoulder portion 11 has a vertical groove 6c and a row of blocks 17 defined by a horizontal groove 15 having one end opening at the end of the tread and the other end opening at the vertical groove 6c. The pitch of the lateral grooves 15 arranged on the inner shoulder portion 11 may be the same as or different from the lateral groove 13 of the outer shoulder portion 9. The width and number of the groove openings are determined so that the void ratio, which represents the ratio of the area of the groove opening to the area where the ground contact surface is developed, expressed as a percentage, satisfies the following relationship.
Outer mediate void ratio> Outer shoulder void ratio Inner mediate void ratio> Inner shoulder void ratio Tread outer half void ratio <Tread inner half void ratio
By setting the radius of curvature Ri of the inner shoulder portion 11 to 60% to 90% of the radius of curvature Ro of the outer shoulder portion 9, the inner shoulder portion is more easily deformed in shape than the outer shoulder portion at the time of contact with the ground, and the wiping action is increased. The reaction force generated with respect to the lateral force is also increased, the cornering power is increased, and the turning performance is improved. Also, the canvas rust generated outside the mounting is reduced by the lateral force due to the wiping on the inside, so that it is difficult to wander when traveling on a rutted road surface. When the radius of curvature Ri of the inner shoulder portion 11 is smaller than 60% of the radius of curvature Ro of the outer shoulder portion 9, the conicity becomes too large and is not practical, and when it is larger than 90%, the lateral force is increased by wiping. The effect is small.
[0008]
Since the median part is related to the aquaplaning performance, it is preferable to increase the void ratio of the mediate part and set the void ratio in the range of 40 to 50%. When the slip angle during turning is large, the outside lateral force greatly contributes to turning performance.Therefore, the void ratio of the outer shoulder portion is made smaller than the void ratio of the outer mediate portion, and at the same time, the outer peripheral portion is not divided by the lateral groove. Direction, the in-plane bending stiffness increases, the in-plane bending stiffness increases, the reaction force generated by the action of the lateral force increases, the maximum cornering force increases, and the high slip angle increases. The turning performance at is improved. When the slip angle during turning is small, the contribution of the inner lateral force to the turning performance is large. Therefore, in order to enhance the turning performance, it is preferable to reduce the void ratio of the inner shoulder portion and increase the in-plane rigidity. Since the effect of the groove of the inner shoulder portion on drainage is great, it is preferable to increase the void ratio. To balance the two, the void ratio of the inner shoulder portion is made smaller than the void ratio of the inner mediate portion.
[0009]
【Example】
The radius of curvature of the outer shoulder portion and the inner shoulder portion is set to the size shown in Table 1, and the void ratio of the outer half surface of the tread, the inner half surface of the tread, the outer shoulder portion, the outer mediate portion, the inner shoulder portion, and the inner mediate portion is expressed. A radial tire having a tire size of 205 / 55R16 and a size shown in FIG. On the other hand, the control tire provided with the tread pattern in which the shape on the right side of the equator of the tread pattern shown in FIG. 2 is symmetrical and the arrangement of the grooves with the tread pattern shown in FIG. Comparative tires having different similar tread patterns were prototyped. The cornering power, the maximum cornering force, the aquaplaning resistance, the dry road turning lateral force acceleration, the wet road turning lateral force acceleration, and the wandering test were performed on the above example tires, control tires and comparative tires according to the following methods. The results are shown in Table 1 by index, with Comparative Example 1 being a control tire being 100. The larger the value, the better.
[0010]
Cornering power (CP) and maximum cornering force (CFmax):
Using a flat belt type tire cornering tester, measure the lateral force while gradually increasing the slip angle from 0 degree to 13 degrees with the tire rolling, and measure the lateral force when the slip angle is 1 degree. (CP), and the maximum lateral force in the process of gradually increasing the slip angle from 0 to 13 degrees was expressed as the maximum cornering force (CFmax).
Aquaplaning resistance:
The vehicle equipped with the prototype tires enters a road with a puddle with a depth of 5 mm at a speed of 80 km / h, and further accelerates to measure the speed when the aquaplaning phenomenon occurs. did.
Dry road turning lateral force acceleration:
The prototype tire was mounted on an automobile, and the vehicle traveled while accelerating a dry circular circuit having a radius of curvature of 40 m, and the lateral acceleration generated at the maximum speed at which the vehicle could turn was measured.
Wet road turning lateral force acceleration:
The prototype tire was mounted on an automobile, the vehicle traveled while accelerating a wet circular circuit having a radius of curvature of 40 m, and the lateral acceleration generated at the maximum speed at which the vehicle could turn was measured.
Wandering:
The prototype tire was mounted on a car and the vehicle was driven on a straight road with a rut. The wobble was evaluated using a score based on feeling.
[0011]
[Table 1]

[0012]
Although the tires of the example had slightly worse aquaplaning performance than Comparative Example 1 having a symmetric tread pattern in the left-right symmetric profile, they had excellent cornering power, maximum cornering force, dry road turning performance, and wandering performance, and the symmetric profile was excellent. Cornering power, maximum cornering force, dry road turning performance and wandering performance are superior to Comparative Example 2 having an asymmetric tread pattern, and other characteristics are equal. Dry road turning performance and wander are obtained by making the profile asymmetric. It is noted that ring performance is improved without degrading other properties. However, Comparative Example 3 in which the radius of curvature of the inner shoulder portion was larger than the radius of curvature of the outer shoulder portion was inferior in all characteristics to Comparative Example 1. Comparative Examples 4 and 5 having an asymmetric tread pattern in which the tread outer half plane void ratio and the tread inner half plane void ratio are the same in the symmetrical profile have inferior cornering power and wandering performance to Comparative Example 1. In all the comparative tires, the performance sought by the present invention was lower than that of the control tire.
[0013]
【The invention's effect】
When mounted on a car, the outer half of the tread from the end of the tread surface on the front side to the equator divides the width into two equal parts and divides it into an outer shoulder part and an outer mediate part. The inner half surface of the tread from to divides the width into two equal parts and divides it into an inner shoulder part and an inner mediate part. The radius of curvature of the inner shoulder part is 60 to 90% of that of the outer shoulder part, and the void ratio of the mediate part> shoulder By satisfying the relationship of the partial void ratio, the outer tread half void ratio <the inner tread void ratio, wiping increases the reaction force of the lateral force and maintains the cornering performance, while increasing the cornering power for normal driving. And whirling performance on a general wet road surface and wandering performance are improved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a radial tire of the present invention. FIG. 2 is a partially developed view of a contact surface of the radial tire of the present invention.
Reference Signs List 1 carcass 3 tread rubber 6 vertical groove 6a adjacent vertical groove 6b adjacent vertical groove 6c adjacent vertical groove 7 tread outer half surface 8 tread inner half surface 9 outer shoulder portion 10 outer mediate portion 11 inner shoulder portion 12 inner media Eight part 13 Lateral groove 14 Lateral groove 15 Lateral groove 16 Block 17 Block Eo Edge of the ground surface on the side shown Ei Edge of the ground surface on the opposite side E Equator Ro Curvature radius of the outer shoulder Ri Radius of curvature of the inner shoulder

Claims (1)

The carcass is reinforced with at least one layer of a carcass ply having a large number of cords arranged at right angles to the tire circumferential direction and rubberized on both sides, and a crown portion of the carcass has a plurality of longitudinal grooves extending in the tire circumferential direction. Covered with tread rubber provided with a block pattern formed by a large number of horizontal grooves connecting the vertical grooves, side portions covered with sidewall rubber, and a large number of cords between the tread rubber and the carcass diagonally to the tire circumferential direction In a flat radial tire in which at least two layers of a rubber ply belt ply are superposed and arranged on both sides, and the surface to be turned to the front side of the side is set when mounted on an automobile, the normal internal pressure is When the design load is applied by filling, the outer half of the tread from the end of the tread surface on the side to be exposed to the equator divides the width by 2 and the outer shoulder The inner half of the tread from the other end of the ground contact surface to the equator is divided into two equal parts, the inner shoulder part and the inner mediate part, and the radius of curvature of the inner shoulder part is The radius of curvature of the outer shoulder portion is set to 60 to 90%, and the outer mediate portion and the inner mediate portion form a row of blocks partitioned by a number of lateral grooves connecting longitudinal grooves extending in the tire circumferential direction and longitudinal grooves adjacent to each other. The outer shoulder has one end open at the tread end and the other end has a rib provided with a number of lateral grooves closed in the shoulder, the inner shoulder has one end open at the tread end, It has a row of blocks partitioned by a number of horizontal grooves, the other end of which is open to a vertical groove, and the void ratio of the shoulder portion of both the inner half surface of the tread and the outer half surface of the tread has the void ratio of the mediate portion. Smaller and flat radial tire void ratio of the inner tread half is equipped with asymmetrical tread pattern asymmetric profile being greater than the void ratio of the tread outer half.

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