JPH06344712A - Radial tire - Google Patents

Abstract

PURPOSE:To enhance driving stability and drivability with a radial tire provided with carcass plies having a first ply extending from inside to outside around a bead core and a second ply extending form outside to inside by specifying the elastic moduli of the plies independently. CONSTITUTION:In a radial tire provided with carcass plies 1 having a first ply 1a extending from inside to outside around the bead core 3 of a bead portion 2 and a second ply 1b extending from outside to inside around the bead core 3, the first ply 1a is formed by a layer of relatively low elastic-modulus cords having an elastic modulus of 1800 to 2100kgf/cm per unit width. The second ply 1b is formed by a layer of relatively high elastic-modulus cords having an elastic modulus of 2400 to 2800kgf/cm per unit width. Thereby the ratio of the elastic modulus of the second ply 1b to that of the first ply 1a is set to the range of 110-140%. Then ride comfort can be greatly improved without deteriorating driving stability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radial tire mainly for passenger cars having a two-layer carcass ply.

[0002]

2. Description of the Related Art A radial tire basically has a carcass ply (1) in which steel cords are arranged in the radial direction, as shown in FIG.
Both ends of the belt are wound around and supported by a pair of bead cores (3) in the bead portion (2), and one or more belt layers are provided outside the carcass ply (1) in the tread portion (4). (5) is arranged. If necessary, a belt reinforcing layer (6) called a cap ply or an edge ply made of a fiber cord is further arranged on the outer side thereof. (7) is a bead filler.

Regarding the carcass structure of such a radial tire (T), generally, as shown in FIG.
A so-called 1-up structure in which a layered carcass ply (1) is wound around a bead core (3) from the inside to the outside. A so-called 2-up structure in which the first ply (1a) on the inner surface side is rolled up from the inner side to the outer second side as shown in FIG.
The plies (1b) are roughly classified into three types of so-called 1-up 1-down structure in which they are wound from the outside toward the inside.

In recent years, in vehicles such as passenger cars for which steering stability is important, the flatness ratio (tire height H and tire width W) is generally known.
A flat tire having a ratio (H / W) of 60% or less is increasingly used. Such flat tires are required to have high steering stability. Therefore, as the carcass structure, a 1-up 1-down structure is often adopted as shown in FIG.

[0005]

The radial tire having the 1-up 1-down structure described above provides structurally high steering stability. However, in the case of a tire having an aspect ratio of 60% or less, a higher performance is obtained. In order to obtain the above, a carcass ply having a high elastic modulus per unit width having a cord having a relatively high modulus is often used.

For example, for both the first ply and the second ply,
The most common idea is to use a high modulus cord such as rayon, but in this case, the rigidity of the tire increases, so steering stability is satisfied, but riding comfort performance is often sacrificed. It is not satisfactory in terms of riding comfort.

A high modulus cord having a relatively small heat shrinkage is used for the first ply on the inner surface side, and a low modulus cord having a relatively large heat shrinkage ratio is used for the second ply on the outer side. Attempts have also been made to improve the efficiency of the cord tension of the first ply and improve the steering stability. However, in this case, there is a drawback in that the riding comfort is greatly deteriorated despite the small improvement in the steering stability.

Generally, in the case of a tire having a 1-up 1-down structure, an average tension is applied to both the first ply and the second ply when the tire is running, so that the response to steering is good and the steering stability is good. In the case of a conventional radial tire of this type, the second
The ply may not have sufficient tension.

That is, in the radial tire, in the first stage of the molding process, the first ply (1a) and the second ply (1b) of the carcass are placed on the molding drum (not shown) as shown in FIG.
With the bead core (3) and the filler (7) sandwiched between them, shaping this at the second stage (not shown) to attach a belt and tread to make a green tire, and vulcanizing this to produce the final product. Use tires. Therefore, the bead portion (2) of the tire changes from the state shown in FIG. 3 to that shown in FIG.

Here, looking at the change in the code path of the first ply (1a) and the second ply (1b), in FIG.
The code paths (A′B) and (C′D) at the bead portion of the first ply (1a) and the second ply (1b) are (A′B <C ′).
D), which is the code path (A "B") of FIG. 4, respectively.
And (C "D"). At this time, the first ply (1
The code path of a) is almost unchanged (A ″ B ″) = (A ′
B), but the code path of the second ply (1b) is (C ″ D ″) <(C′D), and (C ″ D ″) −
It becomes shorter by (C'D) and the code tries to sag. Therefore, the second ply (1b) is in a state in which tension is not sufficiently applied.

In such a situation, in the process of the tire being filled with the internal pressure being subjected to the vertical load and the lateral force, 1) when only the vertical load is applied, a large tension is generated in the first ply, The contribution of the second ply is small.

2) When a lateral force is applied from a state in which a vertical load is obtained, the contribution of the second ply increases and the contribution of the first ply decreases as the lateral force increases.

It is known that

Therefore, when a cord having a high modulus is used for the first ply, the vertical bending with respect to the vertical load is suppressed and the riding comfort is sacrificed.

The present invention has been made in view of the above.
In a radial tire provided with a carcass ply having an up 1 down structure, the ride comfort is improved without impairing steering stability.

[0016]

According to the present invention, a first ply is wound around a bead core from the inside to the outside in a bead portion, and a second ply is wound from the outside to the inside.
In a radial tire having a two-layer carcass ply with a ply, the first ply has an elastic modulus of 180 per unit width.
It is composed of a cord layer having a relatively low modulus of 0 to 2100 kgf / cm, and the second ply has an elastic modulus of 24 per unit width.
It is characterized by comprising a cord layer having a higher modulus of 00 to 2800 kgf / cm, and the ratio of the elastic modulus of the second ply to the first ply is in the range of 110 to 140%.

[0017]

According to the above radial tire, the elastic modulus per unit width of the first ply is 1800 to 8000 under the condition that the tire is subjected to longitudinal load and lateral force.
By using the cord layer having a relatively low modulus of 2100 kgf / cm, it is possible to generate sufficient vertical deflection with respect to changes in vertical load, and ride comfort is improved.

The second ply uses a cord layer having a modulus of elasticity per unit width of 2400 to 2800 kgf / cm, which is higher than that of the first ply. In the second ply, a sufficiently high cord tension corresponding to the change in tension can be secured, the delay in the response to steering is improved, and the followability to the addition of steering during cornering is also improved.

Further, by combining the first ply composed of a cord layer having a relatively low modulus and the second ply composed of a cord layer having a higher modulus, sufficient vertical deflection and appropriate lateral deflection can be realized, resulting in a step. The grounding of the surface is improved,
Along with the increase in grip limit, the behavior near the limit becomes gentle and the controllability is improved.

In the present invention, the elastic modulus per unit width of the first ply is 1800 to 2100 kgf / c.
The reason why m is set is that if the elastic modulus is smaller than the above range, the steering stability is impaired, and if it is larger than the above range, the effect of improving the riding comfort is reduced.

The elastic modulus per unit width of the second ply is 2
The reason why the elastic modulus is set to 400 to 2800 kgf / cm is that if the elastic modulus is smaller than the above range, steering stability is impaired, and if it is larger than the above range, the effect of improving riding comfort cannot be expected. Further, the ratio of the elastic modulus per unit width of the second ply to the first ply is set to 110 to 14
When the value is set to 0%, the effect of improving the riding comfort performance without impairing the driving stability becomes smaller when the value exceeds the range, and when it is less than the above range, the driving stability is impaired even if the riding comfort is improved. This is because

[0022]

EXAMPLES Examples of the present invention will be described below.

FIG. 1 shows a radial tire (T) provided with a carcass ply (1) having a 1-up 1-down structure. In FIG. 1, (1a) is the first ply on the tire inner surface side and (1b) is the outer side. The second ply is shown.

In the present invention, the first ply (1a)
Has an elastic modulus per unit width of 1800 to 2100 kgf /
It comprises a relatively low modulus cord layer of cm, and is constructed using a relatively low modulus cord such as polyester fiber cord. The second ply (1b) is composed of a cord layer having a higher modulus of elasticity per unit width of 2400 to 2800 kgf / cm and having a relatively higher modulus, such as rayon fiber cord or polyamide fiber cord. Consists of

The second ply (1b) is replaced with the first ply (1b).
It can also be constructed by using the same polyester fiber cord as in a). In this case, the elastic modulus per unit width as the cord layer is set within the above range by changing the number of cords to be driven and the cord cross-sectional area. To do.

Further, the first ply (1a) and the second ply
Regarding the relationship between the elastic modulus per unit width of the ply (1b), the elastic modulus A per unit width of the first ply (1a) is
When the elastic modulus per unit width of the second ply (1b) is B, the ratio (A / B) of both elastic moduli is set to be in the range of 110 to 140%.

The elastic modulus per unit width (kgf
/ Cm) is the tensile elastic modulus of the cord (kgf / mm ² ).
× Cord cross-sectional area (mm ² ) × number of imprinted cords per unit width (number / cm).

In the radial tire in which the carcass ply (1) having the 1-up 1-down structure is constructed as described above, the riding comfort can be improved without impairing the steering stability, and the steering stability and the riding comfort can be improved. Both will be satisfied.

(Example) A radial tire having the following structure was subjected to a steering stability test with an actual vehicle and a riding comfort test. The results are shown in Table 1 below.

Example tires A to D Tire size: 195/50 R15, tire internal pressure:
2.0 kg / cm ² , belt layer: Two steel belt layers, and a belt reinforcing layer called a cap ply made of nylon cord was provided outside the belt layer to obtain a tire having a sectional structure shown in FIG. 1. And the carcass structure is shown in Table 1 below.
The first ply and the second ply have the same structure.

Comparative tires 1 to 8 The tire size, tire internal pressure, belt layer and belt reinforcing layer were the same as those of the example tires, and the carcass structure was as follows.
The structure was as shown in Table 1 below.

The test was carried out by a test slalom vehicle using a test driver, and the running speed was 180 km / h. Both the driving stability and the riding comfort are sensory evaluations of the driver, and the driving stability is shown as an index with the tire of Comparative Example 1 having a general carcass structure as 100, and the riding comfort is 100% satisfied. Is displayed as an index.

[0033]

[Table 1]

As shown in Table 1 above, in any of the example tires A to D of the present invention, the riding comfort was significantly improved without impairing the steering stability, and it reached almost a satisfactory level. became.

On the other hand, in Comparative Example 1 in which both the first ply and the second ply are made of a cord layer having a relatively high modulus (having a high elastic modulus per unit width), the riding comfort is not satisfactory and the riding comfort is not satisfactory. Comparative Examples 2 and 8 in which the satisfactorily reached the satisfactory level
In the case of No. 2, both the first ply and the second ply had a low elastic modulus per unit width, the tire rigidity was insufficient, and the steering stability was impaired.

Further, Comparative Example 5 in which the elastic modulus per unit width of the first ply is higher than that of the second ply, and Comparative Example 7 in which the elastic modulus per unit width of the first ply is higher than the range specified by the present invention. Further, in Comparative Example 6 in which the elastic modulus of the second ply was too high, the tire rigidity became high and the effect of improving the riding comfort could not be obtained.

Of course, in the case where the carcass ply has one layer (Comparative Examples 3 and 4), the steering stability as in the 1-up 1-down structure could not be obtained.

[0038]

As described above, according to the present invention, in the carcass ply having the 1-up 1-down structure, the elastic modulus per unit width of the first ply on the inner surface side and the second ply on the outer surface side is within the scope of claims. With this setting, the riding comfort can be significantly improved without impairing the steering stability, and both performances can be achieved at the same time.

[Brief description of drawings]

FIG. 1 is a half sectional view illustrating a radial tire including a carcass ply having a 1-up 1-down structure.

2A to 2C are schematic explanatory views illustrating a carcass structure in each of FIGS.

FIG. 3 is a schematic explanatory view showing a carcass molded state in the first stage of the molding process.

FIG. 4 is a schematic explanatory view showing a carcass shape of a bead portion in a tire of a final product.

[Explanation of symbols]

 (1) Carcass ply (1a) First ply (1b) Second ply (2) Bead part (3) Bead core (4) Tread part (5) Belt layer (6) Belt reinforcement layer

Claims (1)

[Claims] 1. A first ply on the inner surface side wound from the inside toward the outside around the bead core in the bead portion,
In a radial tire having a two-layer carcass ply wound from the outside toward the inside, the first ply has an elastic modulus per unit width of 1800 to 2100.
It is composed of a cord layer of relatively low modulus of kgf / cm, and the second ply has an elastic modulus of 2400 to 28 per unit width.
A radial tire comprising a cord layer having a higher modulus of 00 kgf / cm and having a ratio of the elastic modulus of the second ply to the first ply in the range of 110 to 140%.