KR920007837B1 - Pneumatic radial tire of passenger car - Google Patents

Abstract

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Description

Air radial tires for passenger cars

1 is a partial cross-sectional perspective view of one example of the air radial tire of the present invention.

2 is a relationship between the diameter and the durability of the aromatic polyamide fiber cord.

3 is a cross-sectional view of the belt cover layer which is a conventional tire.

4 is a cross-sectional view of an aromatic polyamide fiber cord layer as a belt covering layer of the tire of the present invention.

* Explanation of symbols for main parts of the drawings

1: tread 2: caracas layer

3d: lower belt reinforcement layer 3u: upper belt reinforcement layer

5: Bells cover layer 5s: Splice part

6: sidewall

The present invention relates to an air radial tire for a passenger car. More specifically, the splice of the belt cover layer is improved by improving the aromatic polyamide fiber cord constituting the reinforcing cord of the belt cover layer laminated on the outermost layer of the belt reinforcement layer. The present invention relates to an air radial tire for a passenger car, which prevents separation failure occurring in a part and greatly improves durability.

In recent years, in accordance with the development of the highway network and the high performance of the passenger car, the advancement of the required performance for the tire and the diversification have been continuously developed.

For example, HR tires that can drive at higher speeds than SR tires, VR tires that can drive at higher speeds, or demands for flat tires with superior steering stability can be cited.

On the other hand, from the vehicle side, a tire is preferable because of the tire house relationship, which enables high-speed driving at the same flat rate and excellent in stability of adjustment. Therefore, high-speed driving performance is achieved by laminating a belt cover layer in which a reinforcement cord made of nylon cord is disposed at approximately 0 ° with respect to the tire circumferential direction on the outermost layer of the two-layer belt layer made of steel cord as reinforcement code. Attempts have been made to improve and have some effect. Nylon cord, however, had low modulus and could not hope for improved steering stability.

Therefore, in recent years, in order to solve the problems described above, air radial tires for passenger cars using aromatic polyamide fiber cords having a much higher modulus than nylon cords have been proposed and proposed.

However, as described above, when the aromatic polyamide fiber cord is used as the reinforcing code of the belt cover layer, the steering stability is significantly compared with the air radial tires for passenger cars in which the belt cover layer using the nylon cord as the reinforcement cord is stacked and arranged. Although it can be improved, the aromatic polyamide fiber cord has poor adhesion to the coated rubber due to its molecular structure, and the so-called peeling off of the aromatic polyamide fiber cord and the coated rubber constituting the belt cover layer, especially at the splice portion of the belt cover layer. There is a fear that a failure may occur and reduce the durability of the tire.

The present invention provides an air radial tire for a passenger car that prevents the occurrence of separation in the splice portion and greatly improves the durability of the tire when an aromatic polyamide fiber cord layer is used for the belt cover layer. It aims to do it.

For this reason, the present invention is formed by a pair of left and right bead portions, a pair of left and right sidewall portions connected to the bead portions, and a tread positioned between the pair of sidewall portions, and between the left and right pair of bead portions. In an air radial tire in which a carcass layer is hypothetically mounted and a belt reinforcement layer is disposed between a tread and a carcass layer, the belt reinforcement layer is at least two layers of steel cord, and an outer side of the aromatic polyamide fiber cord layer A belt cover layer was formed, and the cords of the aromatic polyamide fiber cord layer were substantially parallel to the tire circumferential direction, so that the aromatic polyamide fiber cord layer formed an aromatic polyamide fiber cord having a diameter of 0.55-0.65 mm. In the coated rubber with% modulus of 30㎏ / ㎠-70㎏ / ㎠, buried 40 strands-70 strands per 5cm in the direction perpendicular to the cord To the car air for radial tires according to claim that generated by the invention.

Next, the structure of this invention is demonstrated in detail according to drawing.

1 is a partial cross-sectional perspective view of an example of an air radial tire of the present invention.

In FIG. 1, (1) is a tread, (2) is a carcass layer hypothetically mounted between a pair of right and left bead portions (4) and (4), and in the tread 1 this carcass layer (2) The lower belt reinforcement layer 3d and the upper belt reinforcement layer 3u made of steel cord are enclosed so as to surround the outer periphery of), and the belt cover 5 made of aromatic polyamide fiber cord is arranged on the outer periphery side thereof. 5s is a splice portion of the belt cover layer 5. (6) and (6) are a pair of left and right sidewalls connected to the pair of right and left bead portions 4 and 4. The carcass layer 2 is folded around the bead at the bead portion 4. EE 'means the circumferential direction. As a cord material of the carcass layer 2, glass fibers, such as nylon, a silkworm, and polyester, are used. These fibers usually have a strength of about 5-10 g / d.

In the present invention, the belt reinforcing layer is a steel cord layer as described above. Here, the steel cord layer is represented by two layers of the lower belt reinforcement layer 3d and the upper belt reinforcement layer 3u, but may not necessarily be two layers, and may be at least two layers. In addition, the aromatic polyamide fiber cord layer constituting the belt cover layer 5 is disposed on the outer side of the belt reinforcement layer in which the cord is substantially parallel to the tire circumferential direction. The steel cord of the steel cord layer is preferably composed of steel wire having a carbon content of 0.62-0.87% and a tensile strength of 250 kg / mm 2 or more.

K

3500의 범위가 되도록 꼬아서 코오드로 하여 접착 열처리한 것을 말한다.(1) In the present invention, the aromatic polyamide fiber cord used for the aromatic polyamide fiber cord layer constituting the belt cover layer 5 has a tensile strength of 150 kg / mm 2 or more and a tensile modulus of 3000 kg / mm 2 or more. The aromatic polyamide fibers with a twist coefficient K of 150 can be represented by

K

It refers to the adhesive heat treatment made by twisting the wire so as to be in the range of 3500.

K: twist,

T: Number of twists of the cord (times 10 cm)

D: total denier of the cord

K

3400이면 코오드의 내굴곡 피로성을 향상시킨다는 점에서 더욱 바라직하다.Moreover 2800

K

3400 is more preferable in that it improves the bending fatigue resistance of the cord.

This aromatic polyamide fiber cord is superior in strength as shown in the following table in comparison with organic fibers such as nylon, honeycomb, and polyester, which have been used as conventional carcass codes.

(2) The diameter of the aromatic polyamide fiber cord described above is 0.55 mm-0.65 mm. The smaller the diameter of the cord, the more effective the durability. However, in terms of the strength of the belt cover layer, the rigidity per unit width of the belt cover layer cannot be made too small. This naturally limits the diameter of the cord. Therefore, an indoor endurance test was performed on tires having various diameters of cords, except that the tensile stiffness per unit width in the cord direction was almost constant. In this case, the tire size is 195-70HR 14, the rim is 5 1/2 JJ × 14, the air pressure is 2.1㎏ / ㎠, the diameter of the drum is 1707㎜, the speed is 80km / hr, the initial load is 525㎏, 2 The load was increased by 50 kg every hour. The result is shown in FIG.

In Figure 2, the horizontal axis represents the diameter of the cord, and the vertical axis represents the durability (index). According to FIG. 2, when the diameter of the cord is in the range of 0.55 mm-0.65 mm, it can be seen that durability over conventional tires can be obtained.

In particular, it can be seen that durability is remarkably improved between 0.58 mm and 0.63 mm, which has a durability of 110 (exponent) or more as compared with the diameter of the cord adopted as a conventional tire cord is 0.7 mm. The method of measuring the diameter of a cord was based on JISL-1017.

(3) The coating rubber for embedding the aromatic polyamide fiber cord described above is 30 kg / cm 2 -70 kg / cm 2 with 100% modulus. If it is less than 30 kg / cm 2, since the modulus of the aromatic polyamide fiber cord is large, the durability of the carcass layer is reduced, while if it exceeds 70 kg / cm 2, the coated rubber becomes too hard and productivity is worsened.

(4) In the present invention, an aromatic polyamide fiber cord layer is formed as a belt cover layer by embedding an aromatic polyamide fiber cord into the coated rubber at 40 or 70 strands per 5 cm in a direction perpendicular to the cord. This is because of the following reasons.

In general, with reference to FIGS. 3 (conventional structure) and 4 (structure of the present invention) showing the bending strain of the tire, in particular, the vertical section with respect to the cord of the belt cover layer when the tire is grounded. Consider the stiffness of the warpage against the deformation of the warpage of the cord (if the stiffness of this warpage is large, separation is likely to occur in the code terminal). Larger distance to the surface of the cord relative to the center line of the cord tends to cause larger deformation on the surface of the cord. Here, the stiffness D of the warp means that the cross-sectional secondary moment I is multiplied by the tensile stiffness E.

n = ends

When the number of ends (number of codes per unit width) of each code is n ₁ and n ₂ , respectively, the code intervals e ₁ and e ₂ are as follows.

If the tensile strength in the cord direction per 3rd and 4th unit width is constant,

EA ₁ n ₁ = EA ₂ n ₂

Here, A ₁ = πd equations above because it is ^{_{1 2/4, A = πd}} 2 2/4 is as follows.

When the stiffness ratio of the warp of FIG. 3 and FIG. 4 is m, m becomes as following Formula (5).

That is, even when the tensile stiffness is the same, the stiffness of the warpage (a guideline indicating the degree of easy separation) can be changed. Therefore, by setting d ₂ <d ₁ , this ratio can be made small, thereby making it difficult to segment. However, there is a limit even if the diameter of the cord is made small.

Eventually, parallel buried cords and cords rub against each other, causing cord breakage. Therefore, in the present invention, the number of cords is 40 strands-70 strands per 5 cm in the direction perpendicular to the cords. If it is less than 40 strands, it is not preferable because the coated rubber easily flows between the cords and the rigidity of the belt cover layer is lowered. In addition, when 70 strands are exceeded, invasion of rubber between the cords is inhibited, resulting in lowering of adhesive strength and lowering durability, which is undesirable and expensive. For this reason, the range of 45-65 strands is the best.

As described above, according to the present invention, the belt reinforcement layer is composed of two layers of steel cord layers, and the belt cover layer is composed of an aromatic polyamide fiber cord layer, and the cord of the aromatic polyamide fiber cord layer is tired. 40 to 70 per 5 cm orthogonal to the cord in a coating rubber having an elastic polyamide fiber cord having a diameter of 0.55-0.65 mm and having a diameter of 30 kg / cm 2 to 70 kg / cm 2 substantially parallel to the circumferential direction. Since the strands are embedded in the aromatic polyamide fiber cord layer, the durability of the tire, in particular the durability of the splice portion of the aromatic polyamide fiber cord layer can be improved.

Claims (1)

A pair of right and left bead portions 4 and 4, a pair of left and right sidewall portions 6 that follow the bead portion, and a tread I positioned between the pair of sidewall portions 6; An air radial in which a carcass layer 2 is hypothetically mounted between the pair of right and left bead portions 4 and 4 and a belt reinforcing layer is disposed between the tread 1 and the carcass layer 2. In the tire, the belt reinforcing layers 3d and 3u are at least two layers of steel cord, and a belt cover layer 50 is formed of an aromatic polyamide fiber cord layer on the outer side thereof to provide The cord is substantially parallel to the tire circumferential direction, and the aromatic polyamide fiber cord layer is coated with an aromatic polyamide fiber cord having a diameter of 0.55-0.65 mm in coated rubber having 100% modulus of 30 kg / cm 2 -70 kg / cm 2. Bury 40-70 strands per 5cm at right angles to Lady Air for passenger cars comprising come configured Earl tires.

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