JP2554189Y2 - Steel cord for reinforcing rubber products - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel cord for reinforcing rubber products used as a reinforcing material for rubber products such as automobile tires and conveyor belts.

[0002]

2. Description of the Related Art Steel cords of this kind are used as reinforcing materials for rubber products such as automobile tires, conveyor belts, etc., which are covered with a rubber material in a state where many cords are aligned in parallel. .

As a steel cord for reinforcing a conventional rubber product, for example, a pneumatic radial tire for heavy load, as shown in FIG. 3, a core 12 formed by tightly twisting three strands 11 and 3 + 9 + 15 twisted structure including an intermediate layer 14 formed by tightly twisting nine strands 13 around the periphery of the wire and an outer layer 16 formed by tightly twisting 15 strands 15 around the intermediate layer 14 Is known.

In the steel cord 17, the wires 11, 13, or 13, 15 between the respective layers and the adjacent wires 11, 11, or 13, 13, or 1 in the same layer are provided.
5, 15 are arranged closely or very close.

[0005] Therefore, when the rubber cord is formed, the rubber material cannot penetrate into the space between the above-mentioned strands. Complex could not be formed.

For this reason, in the tire using the steel cord 17, the cord and the rubber material are not sufficiently adhered to each other, so that the cord and the rubber material are peeled off when the automobile is running. , And by the fretting phenomenon caused by the contact between adjacent strands,
A part of the cord breaks, and further, the slight gap existing between the layers of the cord becomes a propagation path of the moisture in the rubber and the moisture that has entered from the cuts of the tire, causing rust on the entire steel cord, This caused the mechanical strength of the steel cord to be greatly reduced.

[0007] In recent years, in order to eliminate the above-mentioned problems, various steel cords have been proposed in which a rubber material can sufficiently enter the inside of the cord.

For example, Japanese Patent Application Laid-Open No. 54-50640 discloses that the number of wires constituting the intermediate layer 21 and the outer layer 22 is reduced to reduce the number of wires between adjacent wires in the same layer, as shown in FIG. A steel cord 23 is disclosed, in which a minute gap C is formed to allow a rubber material to enter.
In Japanese Utility Model Laid-Open Publication No. Sho 56-103092, as shown in FIG. 5, the wire diameter of the wire 32 constituting the core 31 is increased by 5 to 60% from the wire diameter of the wire 35 of the intermediate layer 33 and the outer layer 34. By making the diameter, the minute gap C between adjacent strands in the same layer
And a steel cord 36 that allows the rubber material to penetrate is disclosed.

[0009]

However, even with the above steel cords 23 and 36, the disadvantages of the separate phenomenon, the fretting phenomenon or the decrease in mechanical strength could not be sufficiently solved. The reason is that a void D is still present in the center of the cord because it has a core composed of three strands twisted in close contact with each other.

The present invention has been made in order to eliminate the above-mentioned problems, and provides a rubber material infiltration path extending from the outer periphery of the cord to the center thereof so that the rubber material can penetrate between the wires constituting the cord. It is an object of the present invention to provide a rubber cord for reinforcing a rubber product, which is capable of forming a complete composite of an element wire and rubber by greatly improving the steel cord.

In order to achieve the above object, the steel cord for reinforcing rubber products of the present invention is composed of strands having the same diameter.
3 + m + n (m = 7-9, n = 11-15) three-layer structure
The steel cord with a structure in which each layer is tightly twisted
This is a prerequisite technology and is an improvement of this technology. That is,
Each of the strands has a diameter of 0.15 to 0.30 mm, and at least one of the three strands constituting the core is represented by the formula: P ₁ = 0.1S _{1 to} 0.7S ₁ d ₁ = (D = 2/100 mm) to (d + 2/10 mm) (however, P ₁ : habit pitch (mm), S ₁ : twist pitch of the core (mm), d ₁ : apparent outer diameter (mm), d: element characterized by comprising a habit of substantially spiral shape satisfying the wire diameter (mm)).

By the way, the above various numerical limits are determined based on the results obtained by a number of experiments.

The reason why the diameter of each strand is 0.15 to 0.30 mm is that if the diameter is less than 0.15 mm, the strength of the steel cord is insufficient, and if it exceeds 0.30 mm, the flexibility is poor. .

[0014] In addition, the habit of the spiral, when the twisting pitch of the core was _{S 1,} habit pitch _{P 1} is _P 1 = 0.1
S ₁ in ~0.7S _1, and when the wire diameter is d, the outer diameter _{d 1} of the apparent _{d 1 = (d + 2 /} 100mm) ~ (d +
The reason for setting the range of 2/10 mm) is that if the habit pitch P ₁ is smaller than 0.1 times the twist pitch S ₁ , unreasonable plastic deformation will be applied to the strand when the habit is attached to the strand. The line is easily broken and the productivity is reduced.
On the other hand, if it is larger than 0.7 times, the gap between the wires decreases due to the tensile force due to the flow of the rubber material during molding of the rubber product or the ironing force applied to the cord surface, and the rubber material does not penetrate sufficiently. That's why. Furthermore, the apparent outside diameter d ₁ is d + 2/100 mm less, the use of fluidity of good rubber material can not rubber material is sufficiently penetrating into the interior steel cord pressurized and vulcanization, d + 2/1
If the diameter is larger than 0 mm, the twisting stability is deteriorated, and the fatigue resistance is reduced.

It should be noted that the substantially spiral habit referred to in the present invention does not require a precise spiral shape, and the spiral shape slightly changes within a range satisfying the above expression.
It also includes what is being shaped.

[0016]

[Function] At least one of the three wires constituting the core
Wire with a substantially spiral shape different from the twist of the cord.
The rubber material between the core wires
Is formed, and the rubber material is firmly
Real and full penetration. Therefore, the conventional steel
There is no defect such as gap D, which was a problem with
Become. When the steel cord constructed as described above is pressed and vulcanized between two rubber sheets, the rubber material enters the inside of the cord from the minute gap formed between adjacent strands in the same layer. Penetrate securely and sufficiently until

This rubber material covers the periphery of each element wire to form a complete composite of rubber and cord, thereby preventing the steel cord from being reduced in strength due to fretting phenomenon, separation phenomenon and corrosion.

[0018]

Embodiment 1 An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, 1 indicates a wire diameter d of 0.23 mm.
3 + 9 + 15 consisting of 27 strands of the same diameter having
Steel cord for reinforcing rubber products with a structure.
Has a core 2 composed of three strands at the center.

[0019] The core 2, the habit pitch _{P 1} is 2.4mm
It is formed of two substantially spiral-shaped strands 3 having an apparent outer diameter d1 of 0.28 mm, and _one substantially straight strand 4 without any distortion. , twist pitch S ₁ is at 6 mm, and is constituted by twisted S twist direction.

Around the core 2, nine straight wires 4 are twisted in the S twisting direction at a twist pitch S ₂ of 12 mm and an intermediate layer 5 is formed.

Around the intermediate layer 5, fifteen straight wires 4 are twisted in the Z twist direction at a twist pitch S ₃ of 18 mm to form an outer layer 6.

[0022]

[Embodiment 2] As shown in FIG.
using a wire having a mm, habit pitch _{P 1} is 2.4m
m, a _single spiral wire 3 having a substantially spiral shape having an apparent outer diameter d ₁ of 0.28 mm and two substantially straight wires 4 having a twist pitch S ₁ of 6 mm The core 7 is formed by twisting in the S twist direction, and eight substantially straight wires 4 are twisted in the S twist direction at a twist pitch S2 of 12 mm around the core 7 to form the intermediate layer 5. further, rubber products steel cord for reinforcing this pitch S ₃ twisted strands 4 of substantially straight thirteen around the intermediate layer 5 is in 18 mm, Z twist to form an outer layer 6 by twisting the direction 3 + 8 + 13 construction 8
Was configured.

The wire 3 having a substantially spiral shape in each of the above embodiments is formed by using a buncher-type twisting machine, and using a wire between three to five pins of a hammering cone disposed in front of the twisting machine. , And formed in advance.

The cords in each of the above embodiments were produced using a tubular (tubular) twisting machine.

In each of the above embodiments, the values of m and n in the 3 + m + n structure are set such that m is 9 or 8 and n is 15
Alternatively, although 13 is used, m can be 7 to 9 wires and n can be 11 to 15 wires.

It is sufficient that the gap C between adjacent wires, which is a rubber material intrusion path, is about 0.02 to 0.04 mm. In consideration of the strength of the cord, m is 8,
It can be said that n is more preferably 13 to 14.

Furthermore, the twist pitch S1 of the core is 3 to ₁
It is preferably within a range of 2 mm. This is because the twist pitch S ₁ is is less than 3 mm, too low a strong code of the steel cord, the fatigue resistance decreases when exceeding 12 mm. In addition, since high elongation (corrosion at break is 5% or more) is generally desired for this type of steel cord, it is more preferably in the range of 4 to 8 mm.

Further, it is preferable twist pitch S ₂ of the wires in the intermediate layer 5 is within the length plus 10mm longer than the pitch S ₁ twist the core, and the twist pitch S _1.
The reason is equal to the pitch S ₁ twisting pitch S ₂ is twisted, or when short, if the tensile stress is loaded to a steel cord, easily lead to broken loadbearing of the intermediate layer 5 is too large, on the other hand, if longer than the length of twist pitch S ₂ was added 10mm to the pitch S ₁ twist, because the fatigue resistance is lowered.

Similarly, the twist pitch S ₃ of the outer layer 6 is longer than the twist pitch S ₂ of the intermediate layer 5 and is equal to 1 in the twist pitch S ₂ .
It is preferable that the length be within 0 mm added length.

In order to further improve the stability of twisting of the steel cord, it is possible to wrap the steel cord around with a single steel wire having a diameter smaller than the diameter of the element wire.

Usually, the wire constituting the steel cord is
A steel wire with a carbon content of 0.70 to 0.90 wt% is used, but a steel wire with a carbon content of 0.80 to 0.85 wt% should be used to give the steel cord high strength and good toughness. Is more preferred.

Further, in order to improve the adhesion between the rubber material and the steel cord, it is preferable that each of the above-mentioned wires is plated with brass plating, bronze plating or the like.

Next, the steel cord of the present invention was evaluated with respect to the breaking strength, the penetration rate of the rubber material, and the compressive tensile bending fatigue as a composite with rubber, together with the conventional example and the comparative example, and the results are shown in Table 1. Show. The wires constituting each cord used in the test have a carbon content of 0.82 watts.
t%, the surface of which is plus-plated.

In the evaluation, the breaking strength indicates a breaking load of only the steel cord, and this kind of steel cord requires at least 250 kgf.

The penetration rate of the rubber material is determined by applying a 5 kg tensile load to each cord, embedding the cord in the rubber material, vulcanizing the cord, extracting the cord, disassembling the cord, and decomposing the cord to a fixed length. The length was observed, and the ratio of the length with the trace in contact with the rubber material to the observed length was expressed as a percentage.

The compression-tension / bending fatigue property is obtained by embedding a plurality of cords in a rubber sheet and using a three-point pulley bending fatigue tester to repeat the number of repetitions until breakage due to fretting wear, buckling, or the like. Was measured, and the code of Experiment No. 1 was set to 100 and displayed as an index.

[0037]

[Table 1]

As is clear from the above table, the steel cord of the present invention can satisfy all of the breaking strength, the infiltration property of the rubber material, and the fatigue property. When used for tires, it is expected that the life and ride comfort of the tire will be further improved.

[0039]

[Effect of the Invention] Since the steel cord for reinforcing a rubber product of the present invention has the above-described structure, a rubber intrusion path from the outer periphery of the cord to the inside of the cord is formed, and the rubber material surely penetrates to the inside of the cord. And complete complex.

Therefore, when the steel cord of the present invention is used for a tire, for example, it is possible to remarkably reduce the strength of the cord due to fretting phenomenon, separation phenomenon and corrosion.

The steel cord of the present invention has a core
Twisted because the inter-layer and outer layer are tightly twisted
Is stable and strong as steel cord
And for flexibility is sufficient, so an excellent practical effect that it is possible to extend the life of the tire by a large margin
Can be .

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a steel cord according to the present invention.

FIG. 2 is a sectional view showing another embodiment of the steel cord of the present invention.

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

FIG. 4 is a sectional view of a conventional steel cord.

FIG. 5 is a sectional view of a conventional steel cord.

[Explanation of symbols]

 1,8 steel cord 2,7 core 3,4 strand 5 middle layer 6 outer layer

Claims (1)

(57) [Scope of request for utility model registration] 1. A Ri Do from the strands of the same wire diameter, are three wire
Twisted core and m cores around this core (m = 7
And 9) an intermediate layer formed by tightly twisting the strands;
N (n = 11 to 15) element wires are closely arranged around the intermediate layer.
In a steel cord for reinforcing a rubber product having a 3 + m + n structure having a twisted outer layer , each element wire diameter is 0.1
5 to 0.30 mm, and at least one of the three wires constituting the core is represented by the formula: P ₁ = 0.1 S _{1 to} 0.7 S ₁ d ₁ = (d + 2/100 mm) to ( d + 2/10 mm) (where P ₁ : habit pitch (mm), S ₁ : core twist pitch (mm), d ₁ : apparent outer diameter (mm), d: element wire diameter (mm)) A steel cord for reinforcing rubber products, characterized by having a substantially spiral habit.