JPH0754286A - Steel cord for reinforcing rubber product - Google Patents

Abstract

PURPOSE:To provide a steel cord excellent for reinforcing rubber products such as pneumatic tires or industrial belts. CONSTITUTION:The steel cord so designed that the core filament 3a and sheath filaments 4a in a sheath strand 5 are made identical in both twist direction and twist pitch, and also satisfying the following relationships (I) and (II): 0.5<Pc/Ps<1.0... (I); 2.6<=Pk/Pc... (II) (Pc and Ps are the twist pitches of the core filaments 3 and sheath filaments 4 in a core strand 2, respectively; Pk is cable pitch).

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 as a reinforcing material for rubber articles such as pneumatic tires and industrial belts.

[0002]

Rubber articles reinforced with steel cords,
For example, regarding tires and the like, weight reduction and low rolling resistance have been demanded in response to recent environmental problems and high energy efficiency. In particular, for low fuel consumption tires, steel cords that are lighter and have greater strength are required.

Various proposals have been made so far as the structure of the steel cord (Japanese Patent Laid-Open No. 59-1790, Japanese Patent Laid-Open No. 61-1552, etc.). However, these are intended to improve the durability of the rubber article by increasing the rubber permeability into the steel cord, and the strength of the steel cord has hardly been studied.

Further, Japanese Patent Laid-Open No. 154086/1990 examines in detail the effect of the twist pitch on a pneumatic radial tire reinforced with a steel cord.
However, similarly to the above, this is also intended to improve the durability by increasing the rubber permeability into the steel cord, and the correlation between the strength of the steel cord and the twist pitch has not been examined.

[0005]

Generally, when the ratio Pc / Ps of the twist pitch Pc of the core filament and the twist pitch Ps of the sheath filament in the core strand is increased, the twist loss of the core filament increases. is there. On the other hand, if Pc / Ps is reduced, when 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. There is a problem in that

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

[0007]

As a result of intensive studies aimed at solving the above problems, the present inventors have found a novel structure for increasing the strength of a steel cord, and have completed the present invention.

That is, the present invention provides a core strand and a cord in which a plurality of sheath strands are concentrically twisted around the core strand, and each strand has a core filament and a sheath filament twisted around the core filament. A cord having a layered structure of two or more layers, wherein the core strand and the cord have the same twisting direction, and the core filament and the sheath filament in the sheath strand have the same twisting direction and pitch. The twist pitch of the core filament and the sheath filament inside is P
c, Ps 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 A steel cord for reinforcing a rubber article represented by /Pc≦6.0.

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

Further, in order to suppress the breakage of the cord and 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 set. Ratio dc / d
A stranded steel cord having a different wire 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 Pc / Ps ratio becomes 0.5 or less,
Since the twisting loss of the core filament becomes large, the strength of the cord decreases, and it becomes impossible to obtain a strength suitable as a reinforcing material. On the contrary, when the value of Pc / Ps ratio is 1.0 or more,
The twist loss of the core filament is small, but when 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 breakage. Results in a loss of power.

Next, the ratio of the cable pitch Pk to the twist pitch Pc of the core filaments in the core strand is set to 2.6 ≦ Pk / Pc, preferably 2.6 ≦ Pk / Pc ≦ 6.0. When the value of / Pc ratio is smaller than 2.6, the twist loss of the sheath strand becomes large and the cord strength decreases. Also, as the value of Pk / Pc ratio becomes larger than 6.0, the twist angle of the sheath strand becomes higher, 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 is reduced. .

Regarding the sheath strand, when the helical orbit of the sheath strand itself is increased, when a tensile stress is applied in the longitudinal direction of the cord, the core filament in the sheath strand has a higher twist angle than the surrounding sheath filaments. Due to the large spiral orbit, the difference is offset and the loss of the filament strength is not increased. Further, by appropriately suppressing the twisting process such as twisting of the filament, the twisting loss of the filament itself is reduced, and the cord strength is improved.

The ratio of the outer diameter dc of the core filament forming the strand to the outer diameter ds of the sheath filament twisted around the core filament is set to 1.00≤dc / ds≤1.25 because dc When the ratio of / ds is smaller than 1.00, the contact pressure between the sheath filaments becomes high, 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 becomes large, and the adjacent strands fall into each other to impair the extensibility, or the contact pressure is partially increased, so that the strands easily break.

[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 and Comparative Examples 1 to 4) Here, the steel cords shown in Examples are cords 1 in which a core strand 2 and a plurality of sheath strands 5 are concentrically twisted around the core strand 2. In, each strand is composed of a core filament 3, 3a and a core filament 3,
The core strand 2 has a layer twist structure of two or more layers in which sheath filaments 4 and 4a are twisted around a circumference 3a.
And the cord 1 have the same twisting direction, and the core filament 3a and the sheath filament 4 in the sheath strand 5 are
In the cord 1 having the same twisting direction and twist pitch of a, the twisting pitches of the core filament 3 and the sheath filament 4 in the core strand 2 are Pc,
When Ps and the cable pitch are Pk,
(I) and (II) 0.5 <Pc / Ps <1.0 (II) 2.6 ≦ Pk / Pc (II) The steel cords of Examples and Comparative Examples have the same number of filament arrangements of 7 × (3 + 9) +
Has 1. FIG. 1 shows a sectional structure of an example of a steel cord according to the present invention, and FIGS. 2 and 3 show Pc /
The cross-sectional structures of steel cords with Ps ratios of 0.5 and 1.0 are shown, respectively.

Table 1 below shows the results of measuring the cord strengths of trial steel cords having different twist pitches and cable pitches of filaments in the strands, filament diameters, and carbon contents. Code strength is J
It was measured based on the measuring method of "cutting load" in Section 6.4 defined in "Steel Tire Cord Test Method" of IS G3510. In addition, the measured value is represented by an index with the result of the control (Comparative Example 1) being 100.

[0017]

[Table 1]

From the results shown in Table 1 above, the following was 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) was increased, and the cord strength was increased accordingly. In Example 2, the twisting pitch of the core filament in the core strand was further lengthened, and the cord strength increased as the twisting pitch ratio (Pc / Ps) increased, as in the above case. 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 wt%, which significantly increases the cord strength. 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. Is increasing.

In Comparative Example 2, as compared with Comparative Example 1, the twist pitch of the core filament in the core strand was shortened and the twist pitch of the core filament in the sheath strand was lengthened, whereby the twist pitch ratio ( Pc / P
s) is reduced to 0.33 (outside the scope of the present invention) and chord strength is reduced. In Comparative Example 3, the twist pitch of the core filament in the core strand was made longer than that of Example 3, the twist pitch ratio (Pc / Ps) was increased to 1.00 (outside the range of the present invention), and the cord 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 chord strength is reduced.

[0020]

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

[Brief description of 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)

[Claims] 1. A cord in which a core strand and a plurality of sheath strands are concentrically twisted around the core strand, and each strand has two or more layers in which a core filament and a sheath filament are twisted around the core filament. A cord having a layer twist structure of, wherein the core strand and the cord have the same twisting direction, and the core filament in the sheath strand has the same twisting direction and pitch as the sheath filament, and the core in the core 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, which satisfies (II). 2. The twist pitch Pc of the core filament and the twist pitch Ps of the sheath filament in the core strand.
The steel cord for reinforcing a rubber article according to claim 1, wherein a ratio Pc / Ps thereof is 0.54 ≦ Pc / Ps ≦ 0.90. 3. A ratio Pk / Pc between a twist pitch Pc of core filaments in a core strand and a cable pitch Pk.
Is represented by 2.6 ≦ Pk / Pc ≦ 6.0, The steel cord for reinforcing a rubber article according to claim 1 or 2. 4. The carbon content in the steel cord is 0.8.
The steel cord for reinforcing rubber articles according to any one of claims 1 to 3, wherein a high carbon steel in the range of 0 to 0.85 wt% is used. 5. The ratio dc / ds of 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 is expressed as 1.00 ≦ dc / ds ≦ 1.25. The steel cord for reinforcing a rubber article according to any one of claims 1 to 4.