JPH09300906A - Flat radial tire with asymmetric tread pattern provided in asymmetric profile - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radial tire improved in traveling performance during normal travel and turning performance on the general wet road surface by increasing cornering power while maintaining excellent critical traveling performance. SOLUTION: A tread outer half face 7 is bisected into an outer shoulder part 9 and an outer mediate part 10. A tread inner half face 8 is bisected into an inner shoulder part 11 and an inner mediate part 12, and the radius of curvature R1 of the inner shoulder part is made 60-90% of the radius of curvature R0 of the outer shoulder part 9. The outer mediate part 10 and the inner mediate part 12 are provided with a block row partitioned by lateral grooves tar connecting a longitudinal groove 6 to an adjacent groove. The outer shoulder part 9 is provided with a rib provided with a lateral groove with one end opened to a tread end and with the other end closed in the shoulder part so as to provide an asymmetric tread pattern in asymmetric profile with the void ratio of the tread outer half face 8 made smaller than that of the tread inner half face 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat radial tire. More specifically, the crown curvature radius of the tread and the tread pattern are made different on the left and right sides of the equator, and while maintaining excellent road surface grip performance, cornering power,
The present invention relates to a flat radial tire having an increased cornering force and improved wandering performance, and particularly to a radial tire having an aspect ratio of 60% or less.

[0002]

2. Description of the Related Art Generally, a radial tire used for a passenger car traveling at a high speed has a small flatness and has a straight or zigzag vertical groove extending in the tire circumferential direction on a tread and extends at a right angle or an inclination with respect to the tire circumferential direction. A tread pattern in which blocks divided by lateral grooves connecting adjacent vertical grooves are arranged, that is, a so-called block tread pattern is provided. Among these flat radial tires, in order to improve steering stability, when mounting on a car, the side of the tire is set in advance and the tread pattern design is changed between the left and right sides of the tire equator, In some cases, the void ratio, which represents the ratio of the area of the groove opening to the area of the developed tread surface in 100%, was different between the left and right sides of the equator. Most of them increase the grip performance on dry road surface by making the void ratio of the outer half of the tread from the equator to the end of the grounding surface of the tread exposed to the car relatively small to improve grip performance on the dry road surface. The void ratio of the inner half of the tread was made larger than that of the outer half of the tread to improve drainage and enhance grip performance on wet road surfaces.

A tire having an asymmetrical tread pattern in which the void ratio of the inner half surface of the tread is increased, when turning sharply on a dry road surface in a limit state where skidding occurs, that is, at the time of so-called limit running, turning with a tire having a symmetrical tread pattern Although the performance was excellent, the running performance on a dry road with a gentle curve, the so-called normal running performance and the turning performance when the limit running on a lightly moist road surface was not reached was inferior to the tire having the symmetrical tread pattern. This means that when turning, if the slip angle applied to the tire is small,
Since the void ratio inside the tread's equator (hereinafter, when it is mounted on a car, the side where the side is visible is the outside and the side that is the back is called the inside) is increased, the rigidity of that part is reduced, This is because the cornering power generated as a reaction force of the lateral force in the inner portion becomes small.

[0004]

While maintaining the excellent limit running performance of a tire having a conventional asymmetrical tread pattern, the cornering power is increased so that the steering stability performance during normal running and the limit running are not generally achieved. An object of the present invention is to provide a tire having an asymmetric tread pattern with improved turning performance on a wet road surface.

[0005]

According to the present invention, when mounted on an automobile, the tread surface of the grounded portion of the rotating tire is reduced by reducing the crown radius of curvature of the inner side of the equator of the tread. Friction causes a momentary phase delay in rotation, and then the road surface is swept to quickly return to a predetermined position, so-called wiping is increased, thereby increasing the initial value of the cornering force and turning performance on a wet road surface. Is improved. That is, according to the present invention, the carcass is reinforced by at least one layer of a carcass ply in which a large number of cords are arranged at right angles to the tire circumferential direction and rubberized on both sides, and the crown portion of the carcass extends in the tire circumferential direction. Covered with a tread rubber provided with a block pattern formed by a plurality of extending vertical grooves and a large number of horizontal grooves connecting the vertical grooves, the side portions are covered with sidewall rubber, and a tire circumference is provided between the tread rubber and the carcass. A belt in which at least two layers of belt plies rubberized on both sides are arranged diagonally with respect to the direction and a belt in which at least two layers are superposed is arranged, and a surface to be a front side of a side is defined when the belt ply is mounted on an automobile. In a flat radial tire, when the normal internal pressure is filled and a design load is applied, the outer half surface of the tread from the edge of the contact surface on the side shown in the table to the equator has a width of 2 etc. The inner half of the tread from the other end of the contact surface to the equator is divided into two parts, the inner shoulder and the inner mediate, and the inner shoulder 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 large number of lateral grooves connecting longitudinal grooves extending in the tire circumferential direction and adjacent vertical grooves. A row of blocks, the outer shoulder comprises a rib with one end open to the tread end and the other end provided with a number of transverse grooves closed within the shoulder,
The inner shoulder has a row of blocks divided by a large number of lateral grooves, one end of which opens at the tread end and the other end of which opens at the longitudinal groove, and the inner half of the tread and the outer half of the tread both have voids in the shoulder. A flat radial tire having an asymmetric profile and an asymmetric tread pattern, wherein the ratio is smaller than the void ratio of the mediate portion and the void ratio of the inner half surface of the tread is larger than the void ratio of the outer half surface of the tread.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION In the radial tire of the present invention, the carcass is bilaterally symmetrical with respect to the center line, but the profile and the tread pattern are asymmetrical. . Details of the radial tire of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing a cross section of a 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 by at least one layer of a carcass ply 2 in which a large number of cords are arranged at right angles to the tire circumferential direction and rubberized on both sides, the crown portion is covered with the tread rubber 3, and the side portions are sidewall rubber. It is covered with 4 and is 15 between the carcass 1 and the tread rubber 3 in the tire circumferential direction.
A large number of cords inclined at an angle of -30 ° are arranged and at least two layers of rubberized belt plies on both sides are superposed on each other so that the cords are inclined in mutually opposite directions. The tread rubber 3 is provided with a vertical or zigzag vertical groove 6 extending in the tire circumferential direction and a lateral groove (not shown) extending at right angles or at an angle to the circumferential direction. The tread from the edge Eo of the grounding surface on the side shown when mounting on a vehicle to the equator C when the design load is applied by filling the regular internal pressure prescribed by public standards such as JIS, JATMA Yearbook, TRA, etc. The outer half face 7 has a width of 2
The outer shoulder portion 9 and the outer mediate portion 10 are equally divided.
The inner half surface 8 of the tread from the end Ei of the ground contact surface on the opposite side to the equator C is divided into two equal parts and the inner shoulder part 1
1 and the 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.
One end of the outer shoulder portion 9 opens at the tread end,
A large number of the lateral grooves 13 closed at the other end inside the outer shoulder portion 9 have ribs provided at a predetermined pitch. The outer mediate portion 10 and the inner mediate portion 12 extend diagonally with respect to 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 that connects the lateral grooves 14 that are adjacent in the circumferential direction can be provided. The inner shoulder 11 comprises a vertical groove 6c and a row of blocks 17 defined by lateral grooves 15 which open at one end at the end of the tread and at the other end open at the vertical groove 6c. The pitch of the lateral grooves 15 arranged in 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 the number of the groove openings are determined so that the void ratio, which represents the ratio of the area of the groove openings to the area where the ground plane is developed, 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 surface void ratio <Tread inner half surface 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 likely to be deformed than the outer shoulder portion at the time of ground contact, and the wiping action is improved. As the reaction force is increased, the reaction force generated against the lateral force is also increased, the cornering power is increased, and the turning performance is improved. Further, the canvas last generated on the outer side of the wearing is reduced by the lateral force due to the inner wiping, which makes it difficult to wander when traveling on a road surface with a rut. The radius of curvature Ri of the inner shoulder portion 11 is the radius of curvature R of the outer shoulder portion 9
If it is less than 60% of o, the conicity becomes too large than the permissible range and becomes impractical. If it is more than 90%, the lateral force increasing effect by wiping is small.

Since the mediate portion is involved in the aquaplaning performance, the void ratio of the mediate portion is increased, and the range of 40 to 50% is preferable. When the slip angle during turning is large, the contribution of the lateral force on the outside to turning performance is large, so make the void ratio of the outer shoulder part smaller than the void ratio of the outer mediate part, and at the same time,
Since the in-plane bending rigidity is increased by providing a continuous portion in the circumferential direction without being divided by the lateral groove, the reaction force generated by the action of lateral force is increased by increasing the in-plane bending rigidity, and the maximum cornering force is increased. Becomes higher and the turning performance at a high slip angle is improved. When the slip angle at the time of turning is small, the lateral force on the inside contributes greatly to the turning performance. Therefore, in order to improve the turning performance, it is preferable to reduce the void ratio of the inner shoulder portion to increase the in-plane rigidity. ,
Since the groove of the inner shoulder portion greatly affects the drainage, it is preferable to increase the void ratio, and the void ratio of the inner shoulder portion is made smaller than the void ratio of the inner mediate portion in order to balance the two.

[0009]

EXAMPLE The radii of curvature of the outer shoulder portion and the inner shoulder portion are set to the sizes shown in Table 1, and 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 are formed. Tire size 205 / with the void ratio shown in Table 1
A 55R16 radial tire was prototyped. On the other hand, although a control tire having a 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 tread pattern shown in FIG. 2 and the arrangement of grooves are the same, the width relationship of the lateral grooves is different. A comparative example tire having different similar tread patterns was manufactured. For the above-mentioned example tires, control tires and comparative example tires, cornering power, maximum cornering force, aquaplaning resistance, dry road turning lateral force acceleration, wet road turning lateral force acceleration and wandering test were conducted according to the following methods. The result is 1 for Comparative Example 1 which is a control tire.
It is set to 00 and shown in Table 1 as an index. The larger the value, the better.

Cornering power (CP) and maximum cornering force (CFmax): Using a flat belt type tire cornering tester, the lateral force is gradually increased while gradually increasing the slip angle from 0 to 13 degrees while the tire is rolling. Measure the lateral force when the slip angle is 1 degree as cornering power (CP), and display the maximum lateral force as the maximum cornering force (CFmax) in the process of gradually increasing the slip angle from 0 degree to 13 degrees. did. Aqua-planing resistance: A vehicle equipped with a prototype tire enters a road with a water pool of 5 mm depth at 80 km / h, and further accelerates to measure the speed at which the aqua-planing phenomenon occurs. It was an aquaplaning resistance. Dry road turning lateral acceleration: A prototype tire was attached to an automobile, and running was performed 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 turning was possible was measured. Wet road turning lateral force acceleration: A prototype tire was attached to an automobile, the running was performed 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 turning was possible was measured. Wandering property: Prototype tires were mounted on an automobile, run on a straight road with a rut, and wandering was evaluated using a rating based on feeling.

[0011]

[Table 1]

The example tires are slightly inferior in aquaplaning performance to Comparative Example 1 having a symmetrical tread pattern in the left-right symmetrical profile, but are excellent in cornering power, maximum cornering force, dry road turning performance and wandering performance. The cornering power, the maximum cornering force, the dry corner turning performance, and the wandering performance are superior to those of Comparative Example 2 in which the symmetrical profile has an asymmetric tread pattern, and other characteristics are the same. It will be appreciated that performance and wandering performance are improved without compromising other properties. However, Comparative Example 3 in which the radius of curvature of the inner shoulder portion is larger than that of the outer shoulder portion is inferior to Comparative Example 1 in all characteristics. Comparative Examples 4 and 5 having an asymmetric tread pattern in which the outer half-void ratio of the tread and the inner half-void ratio of the tread are the same in the symmetric profile are inferior to the first comparative example in cornering power and wandering performance. In each of the comparative tires, the performance improved by the present invention was lower than that of the control tire.

[0013]

The outer half surface of the tread from the edge of the grounding surface on the side exposed when mounted on a vehicle to the equator is divided into two equal parts, the outer shoulder part and the outer mediate part, and The inner half surface of the tread from the other end 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 60 to 90% of the outer shoulder part. Part void ratio> Shoulder part void ratio, Tread outer half surface void ratio <Tread inner half surface void ratio By satisfying the relationship, wiping increases the reaction force of lateral force and maintains the limit running performance,
The cornering power is increased to improve the performance during normal driving, the turning performance on a general wet road surface, and the wandering performance.

[Brief description of drawings]

FIG. 1 is a sectional view of a radial tire of the present invention.

FIG. 2 is a partial development view of a ground contact surface of the radial tire of the present invention.

[Explanation of symbols]

 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 Transverse groove 14 Transverse groove 15 Transverse groove 16 Block 17 block Eo Edge of the grounding surface on the side that is shown Ei Edge of the grounding surface on the opposite side C Equator Ro Radius of curvature of outer shoulder Ri Rifle radius of inner shoulder

Claims (1)

[Claims] 1. A carcass is reinforced by at least one layer of a carcass ply in which a large number of cords are arranged at right angles to the tire circumferential direction and rubberized on both sides, and a crown portion of the carcass extends in the tire circumferential direction. Is covered with a tread rubber provided with a block pattern formed of vertical grooves and a large number of horizontal grooves connecting the vertical grooves, side portions are covered with sidewall rubber, and a tire circumferential direction is provided between the tread rubber and the carcass. A flat radial tire in which a belt in which at least two layers of belt plies in which a large number of cords are diagonally arranged and rubberized on both sides are arranged is arranged, and the surface to be the front side of the side when being mounted on a vehicle is defined. At
When the normal internal pressure is filled and the design load is applied, the outer half of the tread from the end of the grounding surface on the front side to the equator is divided into two parts, the outer shoulder part and the outer mediate part. The inner half surface of the tread from the other end of the contact surface to the equator is divided into two parts, the inner shoulder part and the inner mediate part, and the radius of curvature of the inner shoulder part is equal to that of the outer shoulder part. 60-90%,
The outer mediate part and the inner mediate part are provided with rows of blocks defined by a large number of lateral grooves connecting adjacent longitudinal grooves extending in the tire circumferential direction, and one end of the outer shoulder part is opened at the tread end. However, the other end is provided with a rib provided with a large number of transverse grooves closed in the shoulder portion, and the inner shoulder portion is divided by a large number of transverse grooves having one end opening to the tread end and the other end opening to the vertical groove. The inner half of the tread and the outer half of the tread have a smaller void ratio in the shoulder than the void ratio in the mediate and the void ratio in the inner half of the tread is larger than the void ratio in the outer half of the tread. A flat radial tire with an asymmetric profile and an asymmetric tread pattern.