JPH0516622A - Radial tire and its manufacture - Google Patents

Abstract

PURPOSE:To improve the tire lateral rigidity and the tire cornering power without accompanying an improper condition such as an increase of weight of the tire. CONSTITUTION:In a radial tire in which both ends 16 of a carcass ply 10 are wound up from the inner side and the outer side making the bead core 18 of a bead as the fulcrum, a reinforcing layer 22 which consists of a cord with the elastic modulus smaller than that of a carcass cord is provided at the inner side of a bead apex 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radial tire having a bead portion provided with a reinforcing layer and a method for producing the same.

[0002]

2. Description of the Related Art FIG. 2 shows an example of the structure of a conventional radial tire. In the figure, 10 is a carcass ply made of a tire fabric composed of a large number of cords, a tread 12 and a sidewall 14 are attached to the outer side thereof, and a belt 15 is arranged inside the tread 12. Both side portions 16 of the carcass ply 10 are wound around a bead core 18 of a bead portion provided with a bead apex 20 as a fulcrum. In the illustrated example, the both side portions 16 are from the inside (left side of the figure) to the outside (right side of the figure) of the tire. It is wound up toward. Then, after this winding is performed, both side portions 1
A reinforcing layer 22 is attached from the outside of 6, and the bead portion is reinforced by the reinforcing layer 22.

By the way, in recent years, in order to simplify the structure of the radial tire, the carcass is monoply formed, that is, the carcass is composed of one carcass ply 10. In order to realize such monoply, reinforcement to compensate for the strength decrease accompanying this,
In particular, it is necessary to take measures to prevent the lateral rigidity of tires and the reduction of cornering power. Here, conventionally, as the reinforcing means, the bead apex 20 is increased in size, or the winding height PH of the carcass ply 10 (that is, the distance from the bead base line BL to the carcass ply end portion 16) PH is increased. Has been done.

[0004]

The above-mentioned means are as follows.
In addition, the weight of the tire as a whole is increased, and the increase in the weight of the tire increases the amount of heat generated by the tire during traveling, resulting in a decrease in durability. Further, these means have a limited reinforcing effect, and a reinforcing layer made of steel must be arranged for further reinforcement, which further increases the weight of the tire.

In view of the above circumstances, the present invention provides a radial tire capable of effectively improving tire lateral rigidity and cornering power without causing an inconvenience such as an increase in weight of the tire, and a manufacturing method thereof. The purpose is to

[0006]

SUMMARY OF THE INVENTION The present invention comprises a carcass ply composed of a tire fabric, and both sides of the carcass ply from the inside of the tire with a bead core of a bead portion having a bead apex as a fulcrum. In a radial tire wound up on the outside, a reinforcing layer formed of a tire fabric is arranged on the inner side in the tire axial direction of the bead apex, and the carcass ply core
The elastic modulus of the cord is set to be larger than the elastic modulus of the cord of the reinforcing layer (Claim 1).

Further, the present invention is the above-mentioned method for manufacturing a radial tire, in which a reinforcing layer is attached to the outer surface of the carcass ply, and then the carcass ply is rolled up (claim 2).

[0008]

According to the above construction, despite the so-called monoply structure, as is apparent from the experimental data described later, sufficient lateral rigidity and cornering power are secured without increasing the weight of the tire. Further, since the elastic modulus of the cord forming the carcass ply is larger than the elastic modulus of the cord forming the reinforcing layer, the amount of strain of the carcass ply against the load acting during traveling is suppressed accordingly.
Therefore, even if the reinforcing layer is directly attached to the carcass ply, the stress generated in the reinforcing layer is slightly suppressed.

[0009]

EXAMPLE FIG. 1 shows the internal structure of a radial tire according to an example of the present invention.

In the figure, reference numeral 10 is a carcass ply made of a tire fabric composed of a large number of cords. In this radial tire, only one carcass ply 10 constitutes the tire carcass. A tread 12 and a side wall 14 are attached to the outer side of the carcass ply 10 in the radial direction, and a belt 15 is arranged inside the tread 12 adjacent to the outer side of the carcass in the radial direction. Both side portions 16 of the carcass ply 10 are wound around a bead core 18 of a bead portion having a bead apex 20 having a triangular cross section as a fulcrum.
6 is wound from the inside (left side of the figure) of the tire toward the outside (right side of the figure).

As a characteristic of this tire, the carcass ply 1 inside the bead apex 20 is provided.
A reinforcing layer 22 is attached to the outer side surface of No. 0, and the bead portion is reinforced by this reinforcing layer 22. The reinforcing layer 22 is composed of a single ply or a plurality of plies of a tire fabric composed of a plurality of cords, and the material of the cord is an elastic modulus higher than that of a carcass cord. The material is low.

As a method of manufacturing this radial tire,
Instead of winding the carcass ply 10 and then pasting the reinforcing layer 22 as in the conventional case, the reinforcing layer 22 is pasted on the outer surface of the carcass ply 10 in advance, and then the carcass ply 10 is rolled up. do it.

With such a structure, although the carcass ply 10 is monoplyed, it is possible to secure sufficient lateral rigidity and cornering power, as will be apparent from the experimental data described later. Moreover,
Since the elastic modulus of the carcass cord is set to be larger than the elastic modulus of the reinforcing layer 22 and the amount of strain of the carcass ply 10 generated in response to the compressive load acting on the tire is suppressed, the carcass ply as described above is suppressed. Even if the reinforcement layer 22 is directly attached to the ply 10, the stress generated in the reinforcement layer 22 is suppressed to a minute level, and the deterioration of the reinforcement layer 22 is suppressed.

* Experimental data The data shown in Table 1 below shows the tire lateral elastic modulus and cornering power for the standard specification conventional product having a plurality of carcass plies, the conventional monoply structure product, and the two types of the present invention products. The measured results are shown, and the tire lateral elastic modulus and the cornering power are represented by a relative index with that of the standard specification conventional product as 100. Further, in the table, TH, FH, PH, B
H indicates the tire cross-section height from the bead base line BL shown in FIG. 1, the reinforcing layer tip height, the bead apex tip height, and the carcass ply tip height (ply hoisting height). The carcass ply is wound up from the inside to the outside with the bead core of the bead as a fulcrum.

[0015]

[Table 1]

From this data the following considerations can be made.

(A) Compared to the standard specification conventional product having two carcass plies, simply changing the product to monoply reduces both the tire lateral elastic modulus and the cornering power,
Therefore, traveling stability is reduced.

(B) Even if monoplying is performed, if the reinforcing layer 22 is arranged inside the bead apex 20 as in the present invention, the bead apex 20 does not become larger than the standard specification (the apex height). BH), and while suppressing the angle of the reinforcing layer 22 with respect to the radial direction, the tire lateral elastic modulus and the cornering power can be ensured to be equal to or higher than the standard specifications, or can be further increased.

(C) Further, if the carcass cord is made of aromatic polyamide fiber having higher rigidity than polyethylene, the number of twisted cords (that is, the number of filaments constituting each cord) is the same as that of the standard specification. In addition, the winding height PH of the carcass ply 10 is set to the reinforcing layer 22.
Even if the height is lower than the height FH, the tire lateral elastic modulus and the cornering power can be dramatically improved.

Summarizing the above matters, according to the present invention, it is possible to effectively improve the tire lateral elastic modulus and the cornering power without increasing the weight of the tire, while making the carcass monoply. You can say that. If the height FH of the reinforcing layer 22 is too small, a sufficient reinforcing effect cannot be obtained, and if the height FH is too large, the tip of the reinforcing layer 22 bends due to the deformation of the tire and peeling easily occurs. It is desirable to set it to 40 to 60%. Further, if the angle of the reinforcing layer 22 with respect to the radial direction is too small, the rigidity of the tire decreases, so it is generally desirable to set it to 15 to 45%.

[0021]

INDUSTRIAL APPLICABILITY As described above, according to the present invention, the reinforcing layer made of a cord having a smaller elastic coefficient than that of the carcass cord is arranged inside the bead apex, so that the carcass does not increase in weight. It is possible to effectively improve the lateral elastic modulus of the tire and the cornering power while achieving the monoply of the above, and to suppress the deterioration of the reinforcing layer. Further, since the carcass ply can be manufactured by winding the carcass ply with the reinforcing layer attached in advance, the workability of assembly is improved as compared with the conventional carcass ply in which the reinforcing layer is provided after winding.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a radial tire according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing an example of a conventional radial tire.

[Explanation of symbols]

10 carcass ply 16 Both sides of carcass ply 18 bead core 20 bead apex 22 Reinforcing layer

Claims (2)

[Claims] 1. A radial tire comprising one carcass ply composed of tire fabric, wherein both sides of the carcass ply are wound from the inside to the outside of the tire with a bead core of a bead portion having a bead apex as a fulcrum. The reinforcing layer formed of a tire fabric is arranged on the inner side in the tire axial direction of the bead apex, and the elastic coefficient of the cord of the carcass ply is set to be larger than the elastic coefficient of the cord of the reinforcing layer. Radial tires. 2. The method for manufacturing a radial tire according to claim 1, wherein a reinforcing layer is attached to an outer surface of the carcass ply, and then the carcass ply is rolled up.