JPH0559677A - Steel cord - Google Patents

Abstract

PURPOSE:To suppress the permeation of water and the fretting of wires with each other and to improve the corrosion resistance and fatigue resistance of steel cord by sufficiently impregnating a rubber into each layer of a steel cord having three-layer structure. CONSTITUTION:A core part (a) is formed by twisting three wires 1 subjected to excessive forming exceeding 100%. An intermediate layer (b) is formed on the outer circumference of the core part (a) by twisting plural wires 2 subjected to excessive forming exceeding 100%. An outer layer (c) is formed on the outer circumference of the intermediate layer (b) by twisting plural wires 3 subjected to excessive forming exceeding 100%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel cord used for reinforcing a tire for a vehicle.

[0002]

2. Description of the Related Art Generally, in a tire of a large vehicle such as a truck or a bus, a steel cord having a 3 + 9 + 15 structure is used to reinforce the carcass portion or the belt portion.

As shown in FIG. 5, the steel cord of this structure has a core portion a formed by twisting three wires 1 and a core portion a having nine wires 2 on the outer periphery of the core portion a.
An intermediate layer b formed by twisting in the same twisting direction as that of the intermediate layer b at different twist pitches, and an outer layer formed by further twisting 15 wires 3 around the intermediate layer b in a twisting direction and a twist pitch different from those of the intermediate layer b. It has a three-layer structure with c.

[0004]

However, in such a steel cord, each wire 1 constituting each layer 1,
There is almost no gap between the two and three. Therefore, even if the steel cord is embedded in the rubber material and the rubber is vulcanized, it is difficult for the rubber to enter the inside of each layer. The unfilled space 4 remains.

Therefore, when the tire is damaged by reaching the steel cord due to nailing or the like while the tire is running, water penetrates through the damaged portion, and the water is transmitted through the space 4 to the entire length of the steel cord. Penetration into the part, which promotes corrosion of the steel cord and shortens the life of the tire.

Further, between the wires 1 of the core portion a, the intermediate layer b
Since there is almost no gap between the wires 2 of the outer layer c, between the wires 3 of the outer layer c, and between the wires 1, 2, and 3 of the core portion a, the outer layer portion b, and the outer layer c, the fretting of these wires is performed. Frictional resistance reduces the fatigue resistance.

From the above, by reducing the number of wires of the intermediate layer b and the outer layer c, or increasing the number of wires of the core portion a, the wires 2 of the intermediate layer b and the outer layer c are separated from each other. Attempts have been made to create a gap between the wires 3.

However, it is technically difficult to twist the wires 2 and 3 around the outer periphery of the core portion a and the outer periphery of the intermediate layer b with a uniform gap between them, and even if such means is taken, In the core portion a, it is difficult to form a gap between the wires 1, and therefore rubber cannot penetrate into the center portion of the core portion a.

The present invention has been made by paying attention to such a point, and an object of the present invention is to sufficiently penetrate rubber inside each layer to suppress water permeation and fretting between wires. The purpose of the present invention is to provide a steel cord which can surely improve the corrosion resistance and the fatigue resistance.

[0010]

In order to achieve such an object, the present invention forms a core by twisting three excessively shaped wires each of which exceeds 100%,
The outer circumference of this core is twisted with multiple wires that are over-shaped to exceed 100% to form an intermediate layer, and the outer circumference of this intermediate layer is over-shaped to exceed 100%. The plurality of wires thus formed are twisted together to form an outer layer.

[0011]

[Operation] In the steel cord having such a structure,
Excessive shaping of each wire causes the core wires to be separated from each other, the intermediate layer wires to be separated from each other, the outer layer wires to be separated from each other, and the core wire, the intermediate layer wire, and the outer layer wire to be separated from each other. A gap is formed between them,
Therefore, the rubber sufficiently penetrates into the inside of the cheer cord through the gap, the outer circumference of each wire is filled with the rubber, and each wire is independently covered with the rubber. As a result, the penetration of water inside the steel cord is reliably suppressed, and therefore corrosion resistance is improved.Fretting is also suppressed because contact between wires is avoided, and fatigue resistance is greatly improved. To be done.

[0012]

EXAMPLES Examples of the present invention will be described below.

As shown in FIG. 1, three wires 1 having a diameter of 0.175 mm are twisted together to form a core portion a. Before twisting these wires 1,
Excessive shaping exceeding 00% is applied.

After forming the core a, the diameter of the core a is different from that of the core a in the same twisting direction but at a different twist pitch.
The nine wires 0.175 mm are twisted together to form the intermediate layer b. Before the wires 2 are twisted together, the wire 2 is contacted with the theoretical circumscribing circle of the core a, that is,
Excessive shaping exceeding 100% is applied, and in this state, the wire 2 is twisted around the outer periphery of the core portion a.

After the intermediate layer b is further formed, the outer layer b is formed on the outer periphery of the intermediate layer b by twisting 15 wires 3 having a diameter of 0.175 mm in a twist direction and a twist pitch different from those of the intermediate layer b. .. Before these wires 3 are twisted together, the wires 3 are excessively shaped to contact the theoretical circumscribing circle of the intermediate layer b, that is, more than 100%. In this state, the wire 3 is attached to the outer periphery of the intermediate layer b. Twist together.

Such a process can be carried out using a twisting device as shown in FIG. Explaining this twisting device, 10 is a rotor, which is rotatably supported via spindles 11 and 12, and a guide bow 13 is installed inside the rotor 10. Inside the rotor 10, a take-up bobbin 14 and an overtwist 15 that maintain a fixed position regardless of the rotation of the rotor 10 are provided. A ball clamping die 16 and a shaping table 17 are provided on the side of the rotor 10, and a plurality of bobbins 18 and one bobbin 19 are further provided on the sides thereof.

In such a twisting device, the bobbin 19 is wound with the core portion a formed by twisting the three wires 1 as described above, and the bobbin 18 is provided with the intermediate layer b. Each wire 2 for winding is wound. Then, the core a is pulled out from the bobbin 19, and the core a is tightened with the ball clamping die 16, the spindle 11, the guide bow 13,
The bobbin 18 is wound around the winding bobbin 14 through the spindle 12 and the overtwist 15, and the wires 2 are drawn out from the respective bobbins 18, and these wires 2 are respectively shaped table 17, ball clamping die 16, spindle 11, guide bow 13, spindle 12, Take-up bobbin 14 through twist 15
Wrap around.

In such a state, the rotor 10 rotates about the spindles 11 and 12, and the winding bobbin 14 rotates in the direction around the axis thereof.
The core portion a and each wire 2 are sequentially wound by the rotation of 4. Then, when the wires 2 pass through the shaping table 17, the wires 2 are excessively shaped by more than 100%, and the wires 2 thus excessively shaped pass through the ball clamping die 16. When the rotor 10 is rotated, it is twisted around the outer periphery of the core a by the rotation of the rotor 10.

By such a process, a cord in which nine wires 2 are arranged as the intermediate layer b on the outer periphery of the core a is obtained. Next, this cord is wound around the bobbin 19 while changing the core a. The wire 3 constituting the outer layer c is wound around each bobbin 18, and in this state, the wire 3 is twisted around the outer circumference of the cord in the same process as described above. When the wire 3 passes through the shaping table 17, the wire 3 is excessively shaped by more than 100%, and is twisted around the outer circumference of the cord in this state. In such a process, a steel cord having a structure of 3 + 9 + 15 is manufactured.

Forming rate t applied to the wire 1 constituting the core a
1 (%) is about 105 ≦ tl ≦ 125, the shaping rate tm (%) applied to the wire 2 forming the intermediate layer b is about 110 ≦ tm ≦ 130, and the wire 3 forming the outer layer c is As the shaping ratio tn (%) applied to, 115 ≦ tn ≦ 13
Set to about 5. Further, the wire 1 forming the core portion a has, for example, S twist, the wire 2 forming the intermediate layer b has S twist, and the outer layer c
The wire 3 constituting the wire is Z twisted.

In the steel cord having such a structure, due to excessive shaping of the wires 1, 2, 3
As shown in FIG. 1, as shown in FIG.
The wires 2 in the outer layer c, the wires 3 in the outer layer c, the wire 1 in the core a, the wire 2 in the intermediate layer b, and the wire 3 in the outer layer c are separated from each other, and a gap G is formed between them. Therefore, when the steel cord is embedded in a rubber material and the rubber is vulcanized, the rubber is sufficiently intruded into the gap G and the outer circumferences of the wires 1, 2 and 3 are filled with the rubber, that is, The wires 1, 2 and 3 are individually covered. Therefore, there is no space left inside the steel cord, so the penetration of water into the inside of the steel cord is reliably suppressed,
As a result, corrosion resistance is dramatically improved, and contact between the wires is avoided, so fretting is reliably suppressed and fatigue resistance is significantly improved.

3 + 9 composed of wire with a diameter of 0.175 mm
Conventional steel cord of +15 structure and 3 according to the present invention
Table 1 shows the results of measurement of mechanical properties of steel cords having a structure of + 9 + 15. The degree of rubber penetration was evaluated by the amount of air permeation from one end to the other end of the steel cord embedded in the rubber material, and the fatigue resistance was measured by the 3-roll fatigue test method.

[0023]

[Table 1] As is clear from Table 1, the product of the present invention has good rubber penetration and good corrosion resistance and fatigue resistance.

In the above embodiment, nine wires were twisted as an intermediate layer on the outer circumference of the core portion in which three wires were twisted, and 15 wires were twisted on the outer circumference of this intermediate layer. Although the structure is 3 + 9 + 15, FIG.
The structure may be 3 + 9 + 14 as shown in FIG. 4, or the structure may be 3 + 8 + 13 as shown in FIG.

Tables 2 and 3 show the mechanical properties of the steel cord of the present invention and the conventional steel cord of the same structure when they are constructed in the 3 + 9 + 14 structure and the 3 + 8 + 13 structure. It can be seen that good corrosion resistance and fatigue resistance can be obtained even in the product of the present invention having a structure.

[0026]

[Table 2]

[0027]

[Table 3]

[0028]

As described above, according to the present invention, it is possible to surely invade the rubber inside each portion of the steel cord, so that the permeation of water can be suppressed and the corrosion resistance can be improved. There is an advantage that fretting between wires can be suppressed and fatigue resistance can be improved.

[Brief description of drawings]

FIG. 1 is a sectional view of a steel cord having a 3 + 9 + 15 structure according to the present invention.

FIG. 2 is a configuration diagram showing an example of a twisting device used for manufacturing the steel cord of the present invention.

FIG. 3 is a sectional view of a steel cord having a 3 + 9 + 14 structure according to the present invention.

FIG. 4 is a sectional view of a steel cord having a 3 + 8 + 13 structure according to the present invention.

FIG. 5 is a sectional view of a conventional steel cord having a 3 + 9 + 15 structure.

[Explanation of Codes] a ... Core part b ... Intermediate layer c ... Outer layer 1 ... Core part wire 2 ... Intermediate layer wire 3 ... Outer layer wire

Claims (1)

[Claims] 1. A core part is formed by twisting three wires each having an excessive shape of more than 100%, and a plurality of wires each having an excessive shape of more than 100% are formed on the outer periphery of the core part. A steel cord formed by twisting two wires together to form an intermediate layer, and then twisting multiple wires with excessive shaping of more than 100% on the outer circumference of each intermediate layer to form an outer layer.