JPH07149115A - Pneumatic tire having bead core reinforced by organic fiber - Google Patents

Abstract

PURPOSE:To provide a lightweight tire in which the rigidity of a tire bead core is increased, and ring shape keeping ability is set up to improve working ability. CONSTITUTION:A bead core is composed of a rubber matrix 4 arrangedly reinforced by a high strength organic fiber cord 2, and the circumstance of the organic fiber cord 2 is oriented in about parallel to the longitudinal direction of the organic fiber cord 2 by an organic short fiber 3, and it is desirable that the diameter D of the section of the organic short fiber 3 be 0.05 to 0.8mum, and its length L be longer than 8mum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire having a bead core reinforced with an organic fiber, and particularly an organic fiber bead core using an organic fiber short fiber as an auxiliary reinforcing material.

[0002]

2. Description of the Related Art Generally, a bead core which constitutes a bead portion of a conventional pneumatic tire is reinforced with a steel wire, and a rubber layer is in contact with the periphery of the bead core and between the wires, which is required there. In order to obtain a predetermined bead core strength, the realization was possible even with a relatively small bead core volume.

That is, there is a bead core 13 composed of a conventional steel wire 11 and a rubber layer 12 shown in FIG.

In response to the recent demand for fuel saving, weight reduction of the bead core has been studied as one of the measures to realize the weight reduction of the tire. For that reason, the conventional steel wire forming the bead core is replaced with a light weight and a relatively small weight. High-strength organic fiber cords, glass fibers, and carbon fibers have come to the fore. In particular, the aramid fiber cord has been attracting a lot of attention, and the development of a bead core structure using it has been vigorous.

However, here again, it results in how to maximize the strength of the aramid fiber cord, and its auxiliary materials, that is, the fixing material and the fixing method, are one of the measures, and are related to this. Various attempts have been made. For example, an attempt has been made in which the aramid fiber, which is a high modulus organic fiber, is replaced with a conventional matrix of rubber or the like and integrally cured with a thermosetting resin such as polyurethane, polyester, or polyepoxy resin (JP-A-57-660).
07).

[0006]

However, in such a bead core, since it has been hardened to a solidified state with a thermosetting resin or the like in order to approximate the rigidity of the conventional bead wire, there are the following problems. That is, when the tire is mounted on the rim, when the lever is passed over the flange portion of the rim, the bead wire may be locally bent and deformed. May decrease and, in the worst case, may break. In order to prevent this, there is a measure to increase the cord cross-sectional area, but this is against the measure to reduce the weight of the bead core for the purpose of using the aramid fiber cord. Furthermore, since the bending rigidity is insufficient in the solidified state of the bead core consisting only of the aramid cord and the thermosetting resin matrix, the bead core 1 as shown in FIG.
Also, it is easily deformed by its own weight, and a procedure for expanding it before the next work step is required, which lowers workability in the manufacturing process.

In view of the above-mentioned circumstances, the present inventors have considered the relationship between the number of twists and the tenacity retention ratio in the case of using a high tenacity organic fiber as the bead core, the deformability and shape retention of the bead core in the molding process, Further, the relationship between these and the reinforcing effect of the bead core was eagerly studied from the viewpoint of the reinforcing material. As a result, by improving the rigidity and circular shape retention of the bead core by orienting in the length direction of the bead core in the rubber matrix using the short fibers of the nylon fiber as a reinforcing material and arranging the beads around the aramid cord. I came to discover the fact that.

Therefore, an object of the present invention is to provide a lightweight tire which improves the rigidity of the bead core and establishes the ring shape retaining property to improve workability.

[0009]

[Means for Solving the Problems] A rubber matrix is arranged and reinforced by a high-strength organic fiber cord, and organic short fibers are arranged around the high-strength organic fiber cord substantially parallel to the length direction of the high-strength organic fiber cord. It is characterized by a structure oriented to. The organic short fibers are nylon short fibers, and the cross-sectional diameter D of the nylon short fibers is 0.05 to 0.8 μ.
It is preferable that m and the length L are 8 μm or more. Further, when the twist number of the high-strength organic fiber cord is in the range of 0 to 20 times / 10 cm, the aramid fiber cord is particularly preferable since it is effective from the viewpoint of maintaining the strength.

In the above, if the cross-sectional diameter is less than 0.05 μm, it is too fine and orientation becomes difficult, resulting in no reinforcing effect.
If it exceeds μm, it will be too large and it will be difficult to mix it in the matrix. Further, if the length is less than 8 μm, it is difficult to mix it with the rubber matrix. A preferable maximum length is 500 μm, and when it exceeds 500 μm, the fibers are entangled with each other to cause poor dispersion, resulting in pills and further cracking of the rubber. The number of twists of the high-strength organic fiber cord must be 0 to 20 times / 10 cm. If the number of twists exceeds 20 in 10 cm, the strength retention decreases as shown in the graph of the relationship between the number of cord twists and the strength retention shown in FIG. The preferred blending amount of the short nylon fibers is 5 to 30 parts by weight based on 100 parts by weight of the total weight. In this case, if the amount is less than 5 parts by weight, the reinforcing effect is low, and if the amount exceeds 30 parts by weight, compounding into the rubber matrix becomes somewhat difficult. Here, the rubber of the rubber matrix includes natural rubber, synthetic rubber and the like, and also includes synthetic elastomer.

[0011]

As described above, in the tire according to the present invention, the organic short fibers are oriented in the longitudinal direction around the high-strength organic fiber cords arranged in the rubber matrix in the untwisted or sweet twisted state which constitutes the bead portion. Because of this configuration, when a deformation stress is applied to the cord in the lateral direction, the inside of the deformation in the strand of the bead core is elastic because it does not solidify between the filaments of the cord with resin as in the conventional case. It withstands compressive force well, absorbs deformation stress well and does not break. In addition, since the high-strength organic fiber cord, which is the main reinforcement material of the bead core, has a limited number of twists, the filaments are unlikely to rub against each other in the cord, and the cutting strength is also improved (see FIG. 2). Furthermore, since the high strength organic fiber cords are mixed with the organic short fibers in the rubber matrix and oriented in the length direction, the bending rigidity is improved, and the ring shape retention in the manufacturing process is good, so workability is improved. Exhibits effects such as improvement.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the present invention will be described below with reference to the accompanying drawings, but the present invention is not limited thereto.

FIG. 1 is a partial perspective view showing a sectional structure of a bead core which is an example of an embodiment according to the present invention. In the figure, 1 is a bead core, and 2 is a high-strength organic fiber cord which is a main material of the reinforcing cord of the bead core 1, and is specifically an aramid fiber. 3 is a rubber matrix 4
Is an organic short fiber which is oriented around the aramid fiber cord 2 in the longitudinal direction of the aramid fiber cord 2.
Specifically, it is a nylon short fiber. In addition, one of the molding methods for this bead core is the aramid fiber cord, which is the main reinforcing cord, and the adhesive is pre-treated with an epoxy resin to improve the adhesiveness with rubber, and then an adhesive is applied with resorcin / formalin resin latex (RFL). A reinforced rubber (FRR) in which short fibers are preliminarily blended is extruded and pulled around the treated material to orient the short fibers in the length direction of the aramid fiber cord, and a predetermined number of the covered fibers are collected to form a bead core. As another method, there is a method in which the FRR is coextruded with a common nozzle to coat and pull the surface of the aramid fiber cord at once.

Comparison with Comparative Examples 1) Test tire Tire size; 175/70 R 13 82S bead core structure; as shown in Table 1.

2) Test method Water pressure test method: The pressure at the time when the bead portion broke while the tire was installed in the rim and water pressure was applied was 10 in Comparative Example 2.
It was displayed as an index of 0. The larger the number, the better.

As described above, the tires 1, 2 and 3 of the present invention and the tires of Comparative Examples 1 and 2 were prepared and subjected to a predetermined test. The test results are shown in Tables 1 and 2. Comparative Example 1,
No. 2 is an example of non-use of organic short fibers.

As can be seen from Tables 1 and 2 above, a bead wire made of conventional steel wire (Comparative Example 2)
The weight ratio of the bead core is 70%, which is 30% lighter. Further, in the bead core according to the present invention in which nylon short fibers are blended and oriented as compared with the bead core having only the aramid fiber cord (see Comparative Example 1), there is no difference in the bead core weight, but the hydraulic test burst pressure is greatly improved. It can be seen that the steel wire of Comparative Example 2 is also improved. Margin below

[0018]

[Table 1]

[0019]

[Table 2]

[0020]

According to the present invention, a high-strength organic fiber cord, which is untwisted or sweet-twisted and is filled with a thermosetting resin between filaments and is not solidified, is surrounded by organic short fibers to surround the cord in a rubber matrix. Since the cords are oriented in the length direction, even if a deformation stress from the lateral direction of the cord acts, the deformation stress is well absorbed, the cord does not break, and high strength is retained. Since it is surrounded by short fibers, the bending rigidity of the center cord is increased and the required characteristics of the bead core are satisfied. Moreover, the bead core according to the present invention can be manufactured in the step shown in FIG.
Even if it is hooked on the hook of the molding machine as shown in (b), it does not hang down like the conventional bead core (Fig. 3-a).
Since it has a substantially circular shape, when moving to the next work step as it is, there is an effect that the pickup fitting of the bead core becomes easy and the work efficiency is improved.

[Brief description of drawings]

FIG. 1 is a partial perspective view showing a cross-sectional structure of a bead core showing an embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the number of twists of an aramid fiber cord and the strength retention.

3A and 3B are perspective views for explaining a ring-shaped holding state in a bead core forming step.

FIG. 4 is a partial perspective view showing a sectional structure of a conventional bead core.

[Explanation of symbols]

 1 bead core 2 high-strength organic fiber cord 3 organic short fiber 4 rubber matrix

Claims (3)

[Claims] 1. A high-strength organic fiber cord comprising a rubber matrix arranged and reinforced by an array, the high-strength organic fiber cord being surrounded by organic short fibers, and the organic short-fibers being surrounded by the high-strength organic fiber cord in a rubber matrix. A pneumatic tire having a bead core reinforced with an organic fiber, which is oriented substantially parallel to the length direction of the. 2. The organic short fibers are nylon short fibers, and the cross-sectional diameter of the nylon short fibers is 0.05 to 0.8 μm,
The pneumatic tire having a bead core reinforced with an organic fiber according to claim 1, having a length of 8 μm or more. 3. The high-strength organic fiber cord has a twist number of 0 to
A pneumatic tire having a bead core reinforced with an organic fiber according to claim 1 or 2, which is an aramid fiber cord of 20 times / 10 cm.