JPH05319018A - Penumatic radial tire - Google Patents

Abstract

PURPOSE:To provide a tire which is superior in its cornering characteristic, by contriving a tire whose tread area is not shifed to the outside part or to the inside part especillay at cornering. CONSTITUTION:This pneumatic radial tire has a carcass comprising a ply which is formed of radially arranged cords and extends toroidally between a pair of bead parts, as a framework, and belts comprising steel cords parallel arranged on the carcass. The cords used to constitute the belts are not less than 17000kgf/mm<2> in their tensile modulus and not more than 4500kgf/mm<2> in their compression modulus.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire having excellent dynamic performance, and is intended to realize particularly stable cornering.

[0002]

2. Description of the Related Art In a pneumatic radial tire, it is customary to reinforce the carcass, which forms the skeleton of the tire, with a belt. The belt is formed by arranging the cords arranged in parallel with each other at an inclination angle of 15 to 25 ° with respect to the equator of the tire. When a plurality of the cords are laminated, the cords are arranged so that the cords intersect with each other.

Here, as the cord to be used for the belt,
For example, a single twist steel cord having a 1 × 4 structure and a 1 × 5 structure, a double twist steel cord having a 3 × 4 structure, or an organic fiber cord such as an aromatic polyamide is known.

Generally, the physical properties of the cord, which influences the characteristics of the belt and thus of the tire, particularly the tensile modulus and the compression modulus, are large when one is large, and the other is small when one is small. For example, 1 × 4 and 1 × 5 single twist steel cords and 2 + 6 layer twist cords have a large tensile modulus and compression modulus, and 3 × 4 double twist steel cords and organic fiber cords have a tensile modulus. Also, the compression modulus is small.

[0005]

By the way, the cornering performance of a pneumatic tire depends largely on the ground contact shape of the tire. That is, in cornering, a compression input is applied to the outside of the tire located outside the corner, and a tensile input is applied to the inside of the tire.
The contact shape of the tire changes during cornering, which hinders stable driving at the corner.

The above-mentioned cords have both a large tensile modulus and a small compressive modulus, and when both cords having a large modulus are applied to the belt, the contact area on the outer side of the tire is reduced, while both the modulus are increased. When a small cord is applied to the belt, the contact area inside the tire is reduced, and good ground contact cannot be obtained.

Therefore, an object of the present invention is to provide a tire having excellent cornering characteristics in which the contact area of the tire during cornering is not biased outside or inside the tire.

[0008]

SUMMARY OF THE INVENTION According to the present invention, a carcass composed of a ply of radial arrangement cords extending in a toroidal shape between a pair of bead portions has a skeleton as a skeleton, and cords are arranged in parallel on the carcass. a pneumatic radial tire which includes a steel cord constituting the belt tension and compression modulus at modulus 17000kgf / mm ² or more is characterized by using those 4500 kgf / mm ² or less, It is a pneumatic radial tire.

Here, the tensile modulus is a value obtained by dividing the stress per unit elongation of the linear portion in the tensile stress-strain curve of the cord by a commonly used tensile tester by the cord cross-sectional area, and the compression modulus is , Is a value obtained by dividing the stress excluding the stress due to the rubber portion in the straight line portion in the compressive stress-strain curve of the cord when the rubber in which the cord is embedded is compressed by a compression tester, by the cord cross-sectional area.

[0010]

Next, the experimental results which are the basis of the present invention will be described. The tires using various cords for the belt were experimentally manufactured, and the results of examining the grounding properties of the tires are shown for representative cords. That is, the characteristics are shown in FIG.
When the grounding property of a belt-equipped tire composed of steel cords of 1 × 5 × 0.23 mm structure and 3 × 4 × 0.15 mm structure was examined, the cord of 1 × 5 structure showed that the tire was outside the tire as shown in FIG. It was found that the 3 × 4 structure cord had insufficient grounding property inside the tire.

Therefore, as shown in FIG. 1, a cord having both the characteristics of the cord of 1 × 5 structure and the cord of 3 × 4 structure was prototyped, and the grounding property of the tire applied to the belt was examined. As shown in (3), a good ground contact shape was obtained in which the ground contact property was not biased to the outside or inside of the tire.

Based on the above experimental results, a cord suitable for a belt that further affects the cornering characteristics was examined, and the tensile modulus of the cord was 17,000 k.
gf / mm ² or more and compression modulus of 4500 kgf / mm ² or less, more preferably 18500 kgf / mm ² or more and 3500 kgf
It has been found that it is effective to set it to / mm ² or less.

That is, the higher the tensile modulus of the cord, the more the ground contact area inside the cornering can be secured, which has a very good influence on the motion performance. If the tensile modulus is less than 17000 kgf / mm ² , the ground contact area is sufficient. As a result, it is not possible to obtain satisfactory exercise performance,
17,000kgf / mm ² or more.

The compression modulus in the code is
The lower it is, the more the ground contact area on the outside of the cornering can be secured, and the lifting phenomenon due to buckling deformation at the ground contact part can be avoided, which has a good effect on motility, and when this compression modulus exceeds 4500 kgf / mm ^2. ,
The ground contact area is reduced, and the floating phenomenon caused by buckling deformation also causes the actual ground contact area to decrease, making it impossible to obtain satisfactory exercise performance. Therefore, the value should be 4500 kgf / mm ² or less.

In the present invention, the cord used for the belt is not particularly limited in material, structure or filament diameter as long as the tensile modulus and the compression modulus are within the above ranges. Therefore, there are no restrictions on changes such as a part of the filaments constituting the cord being organic fibers, open twisting, or arranging the filaments of the sheath in the layer-twisted cord in a biased manner.

Specific examples of the code applied to the present invention are shown in FIGS. First, in the steel cord shown in FIG. 3, the sheath in the layer twisted cord of the 1 + 3 structure is arranged such that the three filaments are gathered on one side of the core, and the space is provided on the other side of the core. It has been lowered.

The cords shown in FIGS. 4 to 5 are the filaments 1 or 2 of the single twist cord having the structure of 1 × 2 to 5.
An organic fiber is used for the book, and FIG. 6 shows the spiral single wire and FIG. 7 shows the cord of FIG. 4 with open twist.

[0018]

EXAMPLE The cords having the structures shown in FIGS. 3 and 4 were prototyped under the specifications shown in Tables 1 and 2, and these cords were applied to a belt of a radial tire for passenger cars of size 175 / 70R13. Here, the carcass has a polyester cord
Tires each having two layers of belts each having 56 cords / 50 mm, which is one of the plies driven and on which various cords shown in Tables 1 and 2 are driven, are trial-produced on the carcass. For comparison, the structures shown in FIGS.
The tires in which the cords prototyped with the specifications shown in and 2 were also applied to the belts were prototyped.

The trial tires thus obtained were mounted on a vehicle and a maneuverability test was conducted to evaluate the driver's feeling of control performance. The evaluation results are also shown in Tables 1 and 2 as a maximum of 10 points.

[0020]

[Table 1]

[0021]

[Table 2]

[0022]

According to the present invention, by using a cord suitable for a tire belt, it is possible to provide excellent cornering characteristics in which the contact area of the tire during cornering does not deviate outside or inside the tire. Therefore, the exercise performance of the tire can be improved by a simple method.

[Brief description of drawings]

FIG. 1 is a graph showing physical properties of cords.

FIG. 2 is a schematic view showing a ground contact shape of a tire.

FIG. 3 is a sectional view of a cord.

FIG. 4 is a sectional view of a cord.

FIG. 5 is a sectional view of a cord.

FIG. 6 is a sectional view of a cord.

FIG. 7 is a cross-sectional view of a cord.

FIG. 8 is a sectional view of a cord.

FIG. 9 is a sectional view of a cord.

FIG. 10 is a cross-sectional view of a cord.

FIG. 11 is a sectional view of a cord.

Claims (1)

[Claims] 1. A pneumatic radial tire having a carcass composed of a ply of radial array cords extending in a toroidal shape between a pair of bead portions as a skeleton, and a belt having steel cords arranged in parallel on the carcass. The cords that make up the belt have a tensile modulus.
17,000 kgf / mm ² or more and compression modulus is 4500 kgf /
A pneumatic radial tire characterized in that it is made of a material of mm ² or less.