JP2556913B2 - Radial tire - Google Patents

Description

TECHNICAL FIELD The present invention relates to a radial tire having improved steering stability performance.

[Problems to be Solved by Prior Art and Invention]

In recent years, radial tires in which carcass cords are arranged in the radial direction and a belt layer made of metal cords are arranged are often used because of their excellent durability performance, steering stability, wear resistance performance, etc., and also for vehicles, especially passenger cars. With the increase in power performance, further improvement in driving stability is required among these performances.

In a passenger car radial tire having a belt composed of a belt ply composed of two metal cords, the belt enhances the circumferential rigidity of the radial tire and reduces the movement of the contact surface during tire rolling. Therefore, the width of the belt in the axial direction of the tire is set so as to substantially cover the ground contact surface.

For example, in the conventional tire, as shown in FIG. 2, the width Wa measured in the tire axial direction of the innermost belt ply A arranged closest to the carcass layer is equal to the outermost belt ply B.
By setting the width to be wider than the width Wb of the tire, as shown in FIG. This is to prevent concentration, damage starting from this point, so-called belt edge loose (hereinafter referred to as "BEL"), and to prevent deterioration in structural durability performance. However, although such a conventional tire is useful for preventing BEL, it has not been able to satisfy the desired steering stability performance in recent years.

An object of the present invention is to provide a radial tire capable of improving steering stability performance without impairing other performance of the radial tire, particularly, structural durability performance.

[Means for solving the problem]

The present invention is a carcass layer composed of carcass cords wound around the bead core of the bead part from the tread part to the sidewall part from the inside to the outside of the tire and arranged substantially in the radial direction, and the tire of the carcass layer. A belt layer composed of two belt plies formed on the outer side in the radial direction and on the inner side of the tread portion and formed by a cut ply using a metal cord, and a belt layer arranged on the outer side in the tire radial direction of the belt layer and of the belt layer. A reinforcing layer that covers the entire width and has organic fiber cords arranged in parallel in the tire circumferential direction, while the belt ply in the belt ply is closer to the carcass layer than the axial width of the belt ply. The outer belt ply, which is located on the tread side in contact with the ply and is close to the ground contact surface, has a larger width in the axial direction. Between the difference in the axial direction of the width and the step formed by between the ends of the inner and outer belt plies and the carcass is a radial tire hardness it is characterized in that by interposing a 60-90 degree cushion gum.

[Operation] By increasing the width of the belt ply located closer to the ground contact surface, the cornering power can be increased, and as a result, the steering stability performance can be improved.

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, a radial tire 1 has a bead core 5 of a bead portion 4 extending from a tread portion 2 to a side wall portion 3.
Has a carcass 6 made up of carcass cords that are wound from the inside to the outside of the tire and are arranged in the radial direction. As the carcass cord, an organic fiber cord such as polyester, nylon or aromatic polyamide or a metal cord can be used.

On the outside of the carcass 6 in the radial direction of the tire and on the inside of the tread portion 2, there are formed metal cords arranged in parallel and cut ply cut instead of folding both edges in the tire axial direction as shown in FIG. The belt ply 7i and the outer belt ply are arranged inside and outside.
The inner belt ply arranged closest to the carcass layer 6
The widths Wi and Wo in the tire axial direction of the outer belt ply 7o that is in contact with the ply 7i and is disposed on the tread side in the tire axial direction are Wi <Wo. Therefore, a step 8 that is half the difference between the width Wi and the width Wo is formed between the ends a and b of the inner and outer belt plies 7i and 7o. This step 8 is in the range of 2 to 10 mm. If it is less than 2 mm, as in the structure shown in FIG. 3, the concentration of strain is caused at the end portions a and b of the belt, and the BEL resistance performance is deteriorated. If it exceeds 10 mm, the area of one ply becomes too large, and the effect of the belt 7 is reduced.

Further, the width Wo is preferably set in the range of 90 to 125% of the ground contact width Wg. If it is less than 90%, the improvement of the steering stability performance by the ply 7o is not sufficient, and if it exceeds 125%, the belt end portion a is located in the region where the strain is large, and the BEL resistance performance is deteriorated.

The cushion rubber 9 fills the space between the step 8 and the carcass 6. Cushion rubber 9 is belt ply 7o
In order to relieve the strain during rolling of the tire, the hardness is set to a constant hardness, for example, about 60 to 90 °.

In this example, reinforcing layers 10 and 11 are provided on the tread side of the belt layer 7. The reinforcing layer 10 has the same width as the width Wo of the belt ply 7o and covers the entire belt layer 7. The reinforcing layer 11 covers only the shoulder portion of the belt layer 7 and the end portions thereof coincide with the belt layer 7. The reinforcing layers 10 and 11 are composed of organic fiber cords arranged in parallel to the tire circumferential direction. Therefore, this reinforcing layer 10, 11
The belt ply 7o because the cords are arranged in the circumferential direction.
Radially outward deformation of the end of Prevents damage from the edges as a result. Reinforcing layer
10 and 11 do not wrap the belt layer 7 in a fold shape, so that the deformation of the belt layer 7 inward in the radial direction becomes relatively easy. As a result, the end portions of the reinforcing layers 10 and 11 coincide with the end portions of the belt layer 7, and in addition, the rigidity difference between the peeling of the belt layer 7 and the sidewall portion connected to the belt layer 7 is reduced, and damage to the end portions is prevented. prevent.

〔Concrete example〕

A radial tire having a tire size of 185 / 70HR14 was prototyped according to the specifications shown in Table 1 and tested together with the comparative example shown in the table.

As shown in the lower column of Table 1, the tires of the present invention were found to have improved CP and improved steering stability performance as compared with tires having the same belt angle.

〔The invention's effect〕

It has become possible to further improve steering stability performance without impairing the original performance of radial tires.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, and FIGS. 2 to 3 are sectional views of a conventional tire. 1 ... Tire, 2 ... Tread part, 3 ... Sidewall part,
4 ... Bead part, 5 ... Bead core, 6 ... Carcass, 7 ... Belt layer, 8 ... Step, 9 ... Cushion rubber, 10, 11 ... Reinforcing layer.

Claims (2)

(57) [Claims] 1. A carcass layer composed of carcass cords wound around the bead core of the bead part from the inside of the tire to the outside through the side wall part from the tread part and arranged substantially in the radial direction, and the carcass layer of the carcass layer. A belt layer composed of two belt plies formed on the outer side in the tire radial direction and on the inner side of the tread portion and formed by a cut ply using a metal cord, and a belt layer arranged on the outer side in the tire radial direction of the belt layer. And a reinforcing layer in which organic fiber cords are arranged in parallel with the tire circumferential direction while covering the entire width of the belt ply, while the inner width of the belt ply is closer to the carcass layer than the axial width of the belt ply. It is located on the tread side in contact with the belt ply, and the outer width of the belt ply near the contact surface is wider in the axial direction. Radial tire by the axial difference of width between the step formed by between the ends of the inner and outer belt plies between the carcass, characterized in that the hardness is interposed 60-90 degrees cushion gum. 2. The axial width of the inner belt ply is narrower than the axial width of the outer belt ply by 4.0 to 20.0 mm,
The radial tire according to claim 1, wherein the outer belt ply has a width of 90 to 125% of the ground contact width, and the reinforcing layer has the same width as the outer belt ply.