JP3179255B2 - Steel cord for rubber article reinforcement - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a steel cord used as a reinforcing material for rubber articles such as pneumatic tires and industrial belts.

[0002]

BACKGROUND ART Rubber articles reinforced with steel cords,
For example, regarding tires and the like, weight reduction and low rolling resistance have been desired in response to recent environmental problems and higher energy efficiency. In particular, for fuel-efficient tires, a steel cord that is lighter and stronger is required.

Hitherto, various proposals have been made for the structure of a steel cord (JP-A-59-1790, JP-A-61-1552, etc.). However, these are intended to improve the durability of the rubber article by increasing the rubber permeability to the steel cord, and the strength of the steel cord has hardly been studied.

[0004] Japanese Patent Application Laid-Open No. 2-154086 discusses in detail the effect of the twist pitch on a pneumatic radial tire reinforced with a steel cord.
However, similarly to the above, it is intended to improve the durability by increasing the rubber permeability to the steel cord, and the correlation between the strength of the steel cord and the twist pitch has not been studied.

[0005]

Generally, when the ratio Pc / Ps of the twist pitch Pc of the core filament in the core strand to the twist pitch Ps of the sheath filament is increased, the twist loss of the core filament increases. is there. Conversely, when Pc / Ps is reduced, when a tensile stress is applied in the longitudinal direction of the cord, the core filament in the core strand has a higher twist angle than other filaments, leading to premature breakage and loss of filament strength. However, there is a problem that is increased.

The present invention has been made in view of the above-mentioned problems of the prior art, and has as its object to excel in reinforcing rubber articles such as pneumatic tires and industrial belts. Is to provide a steel cord.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above problems, and as a result, have found a novel structure that enhances the strength of a steel cord, and have completed the present invention.

That is, in the present invention, in a cord in which a core strand and a plurality of sheath strands are twisted concentrically around the core strand, each strand has a core filament and a sheath filament twisted around the core filament. A cord having a twisted structure of two or more layers, in which the twist direction of the core strand and the cord is the same, and the twist direction and the twist pitch of the core filament and the sheath filament in the sheath strand are the same. The twist pitch of the core filament and sheath filament in
When c and Ps are used and the cable pitch is Pk, 0.5 <Pc / Ps <1.0 2.6 ≦ Pk / Pc, preferably 0.54 ≦ Pc / Ps ≦ 0.90 2.6 ≦ Pk /Pc≦6.0 is a steel cord for reinforcing rubber articles.

As a reinforcing material, in order to secure the strength of the composite and reduce its weight, the carbon content must be 0.80 to 0.85 watts.
Steel cords in the range of t% are advantageously suitable.

Further, in order to suppress breakage of the cord and to give the cord an appropriate extensibility, the outer diameter dc of the core filament in the strand and the outer diameter ds of the sheath filament twisted around the core filament are determined. Ratio dc / d
A twisted steel cord having a different diameter in which s is in the range of 1.00 ≦ dc / ds ≦ 1.25 is desirable.

[0011]

The ratio of the twist pitch Pc of the core filament in the core strand to the twist pitch Ps of the sheath filament is set to 0.5 <Pc / Ps <1.0, preferably 0.54 ≦ Pc / Ps ≦ 0.90. Is that when the value of the Pc / Ps ratio becomes 0.5 or less,
Since the twist loss of the core filament is increased, the strength of the cord is reduced, and the strength desired as a reinforcing material cannot be obtained. Conversely, when the value of the Pc / Ps ratio is 1.0 or more,
Although the twist loss of the core filament is reduced, the core filament in the core strand breaks prematurely when subjected to tensile stress in the longitudinal direction of the cord because the twist angle is higher than the other filaments. Causes a drop in power.

Next, the ratio of the cable pitch Pk to the twist pitch Pc of the core filaments in the core strand is 2.6 ≦ Pk / Pc, preferably 2.6 ≦ Pk / Pc ≦ 6.0 When the value of the / Pc ratio is smaller than 2.6, the twist loss of the sheath strand increases, and the cord strength decreases. Further, as the value of the Pk / Pc ratio becomes larger than 6.0, the twist angle of the sheath strand increases, and the effect of twisting the twist pitch of the core filament in the core strand shorter than the twist pitch of the sheath filament decreases. .

With respect to the sheath strand, if the helical trajectory of the sheath strand itself is increased, when a tensile stress is applied in the longitudinal direction of the cord, the twist angle of the core filament in the sheath strand is higher than that of the surrounding sheath filament. The large helical trajectory offsets the difference and does not increase the loss of filament strength. In addition, by appropriately suppressing twisting such as twisting of the filament, twist loss of the filament itself is reduced, and cord strength is improved.

The ratio of the outer diameter dc of the core filament constituting the strand to the outer diameter ds of the sheath filament twisted around the core filament is 1.00 ≦ dc / ds ≦ 1.25 because the ratio dc ≦ dc / ds ≦ 1.25 When the ratio of / ds is smaller than 1.00, the contact pressure between the sheath filaments increases, and the cord is easily broken. On the other hand, the ratio of dc / ds is 1.
If it is larger than 25, the distance between the sheath filaments will be large, and the adjacent strands will fall into each other, impairing the extensibility, or breaking easily due to the partial increase in the contact pressure.

[0015]

The present invention will be described below with reference to the drawings based on examples and comparative examples, but the present invention is not limited to these examples. (Examples 1 to 6, Comparative Examples 1 to 4) Here, the steel cord shown in the example is a cord 1 in which a core strand 2 and a plurality of sheath strands 5 are concentrically twisted around the core strand 2. , Each strand comprises a core filament 3, 3a and a core filament 3,
The core strand 2 has a layered structure of two or more layers in which sheath filaments 4 and 4a are twisted around 3a.
The core filament 3a and the sheath filament 4 in the sheath strand 5 have the same twisting direction.
The cord 1 has the same twisting direction and the same twisting pitch a, and the twisting pitches of the core filament 3 and the sheath filament 4 in the core strand 2 are Pc, respectively.
Let Ps be the cable pitch and Pk be the following equation:
(I) and (II) 0.5 <Pc / Ps <1.0 (I) 2.6 ≦ Pk / Pc (II) The steel cords of the example and the comparative example had the same filament arrangement number of 7 × (3 + 9) +
One. FIG. 1 shows a cross-sectional structure of an example of a steel cord according to the present invention, and FIGS. 2 and 3 show Pc /
The cross-sectional structure of a steel cord having a Ps ratio of 0.5 and 1.0 is shown, respectively.

Table 1 below shows the results of measuring the cord strength of each trial steel cord in which the twist pitch and cable pitch of the filament in the strand, the filament diameter, and the carbon content were changed. The code strength is J
It was measured based on the measuring method of "cutting load" of Section 6.4 defined in "Steel tire cord test method" of IS G3510. In addition, the measured value was represented by an index with the result of the control (Comparative Example 1) being 100.

[0017]

[Table 1]

From the results in Table 1, the following has been found.
In Example 1, the twist pitch of the core filament was made longer than that of Comparative Example 1, whereby the twist pitch ratio (Pc / Ps) increased, and the cord strength increased accordingly. In Example 2, the twist pitch of the core filament in the core strand was further lengthened, and the cord strength increased with an increase in the twist pitch ratio (Pc / Ps), as described above. In Example 3, the twist pitch of the core filaments in the core strand was made longer than in Example 2, and the cord strength was improved. Example 4 has a longer cable pitch, which increases the twist pitch ratio (Pk / Pc),
Code strength has also improved. In Example 5, the carbon content was increased to 0.82% by weight, whereby the cord strength was significantly increased. In Example 6, the carbon content was increased to 0.82 wt%, and the outer diameter of the core filament in the sheath strand was increased, whereby the outer diameter ratio dc / ds was increased, and the cord strength was remarkable. Has increased.

In Comparative Example 2, the twist pitch of the core filaments in the core strand was made shorter and the twist pitch of the core filaments in the sheath strand was made longer than in Comparative Example 1, whereby the twist pitch ratio ( Pc / P
s) has been reduced to 0.33 (outside the scope of the invention) and the code strength has been reduced. In Comparative Example 3, the twist pitch of the core filament in the core strand was longer than that of Example 3, and the twist pitch ratio (Pc / Ps) was increased to 1.00 (outside the scope of the present invention). Power is decreasing. In Comparative Example 4, the cable pitch was shortened, whereby the twist pitch ratio (Pk / Pc) was 2.40.
(Outside the scope of the invention) and the code strength is reduced.

[0020]

According to the present invention, as described above, the strength of a steel cord can be improved, and the performance of a rubber article using the steel cord as a reinforcing material can be greatly improved. .

[Brief description of the drawings]

FIG. 1 is a sectional view of a steel cord.

FIG. 2 is a sectional view of a steel cord.

FIG. 3 is a sectional view of a steel cord.

[Explanation of symbols]

 1 Cord 2 Core strand 3, 3a Core filament 4, 4a Sheath filament 5 Sheath strand 6 Spiral filament

Claims (5)

(57) [Claims] 1. A cord comprising a core strand and a plurality of sheath strands concentrically twisted around the core strand, wherein each strand is a core filament and at least two layers of sheath filaments twisted around the core filament. Wherein the core strand and the cord have the same twist direction, and the core filament and the sheath filament have the same twist direction and twist pitch in the sheath strand. The twist pitches of the filament and the sheath filament are Pc and Ps, respectively.
When the cable pitch is Pk, the following equations (I) and (I
I) 0.5 <Pc / Ps <1.0 (I) 2.6 ≦ Pk / Pc (II) A steel cord for reinforcing rubber articles satisfying (II). 2. A twist pitch Pc of a core filament in a core strand and a twist pitch Ps of a sheath filament in a core strand.
The steel cord for reinforcing rubber articles according to claim 1, wherein a ratio Pc / Ps of the steel cord is represented by the following expression: 0.54 ≦ Pc / Ps ≦ 0.90. 3. The ratio Pk / Pc of the twist pitch Pc of the core filament in the core strand to the cable pitch Pk.
The steel cord for reinforcing a rubber article according to claim 1 or 2, wherein is represented by 2.6 ≦ Pk / Pc ≦ 6.0. 4. A steel cord having a carbon content of 0.8.
The steel cord for reinforcing rubber articles according to any one of claims 1 to 3, wherein high carbon steel in a range of 0 to 0.85 wt% is used. 5. A ratio dc / ds of an outer diameter dc of a core filament in a strand to an outer diameter ds of a sheath filament twisted around the core filament is expressed as 1.00 ≦ dc / ds ≦ 1.25. The steel cord for reinforcing rubber articles according to any one of claims 1 to 4.