JPH0585111A - Bead core of pneumatic tire - Google Patents

Abstract

PURPOSE:To provide a bead core of a pneumatic tire where the change of the sectional shape due to vulcanization is prevented, and the sectional shape is not changed by traveling. CONSTITUTION:A bead wire layer is formed by winding bead wires 18 along one side of the axial direction of a tire (L and R direction as marked by the arrow) in a consecutively and closely contact condition, and a bead core of hexagonal sectional shape is made by arranging the specified number of plies of the bead wire layers. The bead wires 18 are arranged so that the respective rows may be set along the circumferential direction of the tire, and connection is made to the following row through a bent part 18A. The bent part 18A is arranged at equal spaces along the circumferential direction of the bead core. The bead core formed in this manner has diversified arrangement of the bent parts 18A, and the stresses are not concentrated on a limited part of the circumference even when the tension is generated in the vulcanization process of the tire and the stresses are exerted on the bent parts 18A, leaving no changes in the original sectional shape.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire bead core used in vehicles such as automobiles, and more particularly to a pneumatic tire bead core having a polygonal cross section.

[0002]

2. Description of the Related Art A bead portion of a pneumatic tire is provided with a ring-shaped bead core. The bead core wraps and fixes a carcass ply and defines the inner circumference of a tire main body, and a wheel rim. Secures a fit.

The bead core is formed in a hexagonal cross section by sequentially stacking a bead wire layer in which a bead wire covered with raw rubber is wound a predetermined number of times along the tire width direction. This bead core is produced by winding a bead wire around a predetermined mold, and as shown in FIG. 5, the bead wire layer 62 is wound once along the tire circumferential direction (directions A and B in FIG. 5). A plurality of bead wire rows are formed by being arranged along the tire axial direction (the arrow R and L directions in FIG. 5). Here, a bent portion 60A is formed between the end of each row of the bead wires 60 and the winding start of the next row, and the position of this bent portion 60A is the same width direction on the circumference of the bead core 52 (see arrow R in FIG. (L direction).

The bead core 52 thus formed
Is incorporated in a raw tire, vulcanized in a mold, and the raw rubber of each bead wire 60 is fixed.

By the way, when the green tire is vulcanized, the carcass is pulled in the direction of arrow C as shown in FIG. 6, and tension acts on the bead core 52. Therefore, each bent portion 60A
Is applied to the bead core 52 near the bent portion 60A.
In addition to the deformation of the cross-sectional shape of No. 1 to obtain the initial cross-sectional shape, it also affects the arrangement of other reinforcing materials such as the stiffener 64, the chafer 66, and the ply end 68.
For this reason, not only the tire performance originally designed was not obtained, but also the deformation of the bead core 52 increased as the traveling distance increased.

[0006]

SUMMARY OF THE INVENTION In consideration of the above facts, an object of the present invention is to provide a bead core for a pneumatic tire which prevents a change in cross-sectional shape due to vulcanization and which does not change even when running. ..

[0007]

The invention according to claim 1 is
A bead core of a pneumatic tire in which a steel wire coated with rubber is wound a plurality of times in the circumferential direction to form a polygonal cross section, and a bent portion when moving to the next winding side of the steel wire is circumferentially applied. It is characterized by being distributed and arranged.

The invention according to claim 2 is characterized in that the bent portions are arranged at substantially equal intervals in the circumferential direction of the bead core.

[0009]

According to the first aspect of the present invention, even if tension is applied to the bead wire when the green tire is vulcanized, since the bent portion of the bead wire is dispersed along the outer peripheral direction, the bent portion is Even if it is deformed, since the bent parts are not concentrated at one point, the deformation of one bent part does not affect the surrounding bead wire, and the bead core is deformed even after vulcanization of the raw tire. The cross-sectional shape before vulcanization is maintained without performing.

In the invention according to claim 2, the invention according to claim 1
In the invention described, since the bent portion of the bead wire is arranged at substantially equal intervals along the circumferential direction, the bent portion is not adjacent to the bent portion on the front winding side and the bent portion on the next winding side, Since the tension during vulcanization acts substantially evenly in the outer peripheral direction, the stress at the time of deformation of the bent portion does not overlap and the surrounding bead wire is not deformed.

Preferably, the adjacent bent portions are (3
They are arranged in the circumferential direction of the bead core at intervals corresponding to the angle from the axis of the bead core expressed by 60 ° / number of turns of steel wire). That is, the bent portion is separated from the bent portion of the adjacent steel wire for a predetermined period, so that the structure of the bead core in the circumferential direction is made uniform.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS.

As shown in FIG. 2, a ring-shaped bead core 10 is arranged in the bead portion 12 of a pneumatic tire 12 (tire size: 11R22.5) to which the present invention is applied. Carcass ply 16 around the bead core 10
Is folded back from the inner side in the tire width direction (right side in FIG. 2) toward the outer side (left side in FIG. 2), and the folded ply 16A is formed on the outer side in the tire width direction. This carcass ply 16
A stapler 17 is arranged in a substantially triangular area surrounded by the body ply 16B and the folded ply 16A. Further, in the bead portion 12, the chafer 1 is provided on the side opposite to the bead core 10 side of the carcass ply 16.
9 are provided.

The bead core 10 is formed by winding the bead wire 18 a predetermined number of times and has a hexagonal cross-section, and the first layer on the side 24 side facing the tire shaft center side (the lower side in FIG. 2). The number of bead wires 18 arranged is 9 in number. As shown in detail in FIG. 4, the total number of bead wires 18 in each bead wire layer in the direction perpendicular to the side 24 is
Nine, ten, eleven, and twelve from the first layer, respectively.
The number of beads is 11, 11, 10 and 9, and the bead core 1
The total of 0 is 72 in total.

As shown in FIG. 3, this bead wire 18
Has a structure in which the outer circumference of the steel wire 20 is covered with raw rubber 22, and the cross-sectional shape orthogonal to the axis is circular. In this embodiment, the diameter d of the steel wire 20 is φ1.55 mm, and the outer diameter D of the bead wire 18 is φ1.8 mm.

As shown in FIG. 1, the bead wire layer (see FIG.
The first layer is shown in the figure), and the bead wire 18 is formed by winding the bead wire 18 toward one side in the tire axial direction (direction of arrows L and R in FIG. 1) in a state of being closely adhered to each other. In the bead wire layer (shown by an imaginary line in FIG. 1), the bead wire 18 is wound in a state in which the bead wire 18 is in close contact with the other side in the tire axial direction, that is, the other side in the tire axial direction.

Here, each row of the bead wire 18 is arranged along the tire circumferential direction, and the bent row 18 is different from the next row.
It is connected through A. Bead core 10 of the present embodiment
Then, the bent portion 18A and the next bent portion 18A are set to have an equal interval in the circumferential direction, and the interval P between the bent portions 18A is an angle when the bead core 10 in the circumferential direction is viewed from the axial direction. The bent portions 18A are arranged at approximately 5 ° intervals (in this embodiment, there are 71 bent portions 18A on the bead core 10, and therefore, in order to evenly distribute these in the circumferential direction, the space between the bent portions 18A is The interval P is the angle at which the bead core 10 is viewed from the axial direction, and 360 degrees of one round is divided by 71 to obtain an angle of 5,
It was set to 07 °. ), The bent portions 18A are arranged so as to be sequentially shifted in the direction opposite to the winding direction.

Next, the operation of this embodiment will be described.
When the raw pneumatic tire 12 is vulcanized, the carcass 10 is pulled in the direction of arrow C in FIG. 2, and tension is applied to the bead core 10. In the bead core 10 of this embodiment, since the bent portions 18A of the bead wire 18 are evenly distributed along the circumferential direction of the bead core 10, the tissue structure along the circumferential direction of the bead core 10 is uniform, and the tension Therefore, even if stress is applied to the bent portion 18A, the stress is not concentrated on a part of the circumference, and even if the bent portion 18A is deformed, the adjacent bead wire 18 is not deformed. Therefore, the cross-sectional shape of the bead core 12 is not deformed during the vulcanization of the pneumatic tire 12, and the initial cross-sectional shape is maintained. Therefore, the positions of the stiffener 17, the chafer 19, the ply end 16A, and the like are not displaced, the tire performance initially designed can be effectively exhibited, and the initial cross-sectional shape of the bead core 12 hardly changes even during running. (Experimental example) A pneumatic tire of the related art (see FIG. 6) (tire size 11R22.5, internal pressure 8.00 kg / c)
m ² , the diameter of the bead wire 56 = 1.55 mm, and the pneumatic tire of the present embodiment (see FIG. 1) (tire size 11R22.5, diameter of the bead wire 16 (D) = 1.
55mm) drum running test (280% of specified load)
%, Running distance 15,000 km) and comparing the bead core deformation amounts are shown in Table 1 below as an index (the conventional product is 100 and the smaller the number is the better).

[0019]

[Table 1] From the above experimental results, the deformation amount of the bead core 12 of this example was 15% smaller than that of the conventional product, and it was revealed that the bead core 12 of this example is superior.

In this embodiment, the bead core 1
The cross-sectional shape of 2 is hexagonal, but the present invention is not limited to this, and needless to say, a bead core having a shape other than a hexagonal cross-section may be used.

Further, it is desirable that the bent portions 18A are arranged at equal intervals in the circumferential direction, but it is sufficient that the bent portions 18A are arranged so as to be dispersed in the circumferential direction, and it is not always necessary to arrange them at equal intervals.

[0022]

Since the bead core of the pneumatic tire of the present invention has the above-mentioned structure, it has an excellent effect of preventing the cross-sectional shape from changing due to vulcanization and preventing the cross-sectional shape from changing during running.

[Brief description of drawings]

FIG. 1 is a plan view of a bead wire row of a bead core according to an embodiment of the present invention as viewed in a radial direction.

FIG. 2 is a cross-sectional view showing a bead portion and its periphery of a pneumatic tire to which a bead core according to an embodiment of the present invention is applied, with partial hatching omitted.

FIG. 3 is a sectional view of a bead wire forming a bead core according to an embodiment of the present invention.

FIG. 4 is an enlarged sectional view of a bead core according to an embodiment of the present invention.

FIG. 5 is a plan view of a bead wire row of a bead core of a conventional pneumatic tire as viewed from a radial direction.

FIG. 6 is a cross-sectional view showing the periphery of a bead portion of a conventional pneumatic tire with partial hatching omitted.

[Explanation of reference numerals] 10 bead core 18A bent portion 20 steel wire 22 raw rubber

Claims (2)

[Claims] 1. A bead core of a pneumatic tire, wherein a steel wire covered with rubber is wound a plurality of times in the circumferential direction to form a polygonal cross section, and the bending is performed when the steel wire is moved to the next winding side. A bead core for a pneumatic tire, characterized in that the parts are arranged in a distributed manner in the circumferential direction. 2. The bead core for a pneumatic tire according to claim 1, wherein the bent portions are arranged at substantially equal intervals in the circumferential direction of the bead core.