JPH11200263A - Steel cord for tire reinforcement - Google Patents

Abstract

(57) [Summary] [PROBLEMS] A rubber material can penetrate to the center of a cord to form a complete composite of cord and rubber, and the elongation of each strand is well balanced, and the twisting cost is low. And practical steel cords for tires. SOLUTION: A total of three spiral core strands 2 and corrugated core strands 3 are used as cores, and eight side strands 4 are arranged therearound. This is a steel cord 1 that is simultaneously twisted.

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 a belt or a carcass of an automobile tire.

[0002]

2. Description of the Related Art A large number of steel cords of this type are covered with a rubber material in a state of being aligned in parallel and used as a reinforcing material for a belt or a carcass of an automobile tire. As a conventional steel cord, as shown in FIG. 6, nine side strands 13 are arranged around three core strands 12 arranged in the center, and twelve strands having the same diameter are arranged. Are tightly twisted in the same direction and at the same pitch, and a so-called 1 × 12 steel cord 11 is known. As the steel cord having the same number of strands as the steel cord 11, nine side strands are formed around a core strand composed of three core strands densely twisted in a direction or at a pitch different from the twist. There is known a steel cord having a so-called 3 + 9 structure in which are twisted densely.

[0003] The steel cord 11 having the above 1 x 12 structure.
However, while the steel cord having the 3 + 9 structure requires two twisting steps, the steel cord can be manufactured by one twisting step, so that the twisting cost can be reduced. However, when the steel cord 11 is covered with a rubber material, as shown in FIG. 6, since the individual wires are in close contact with each other and the gap D is present inside the cord as shown in FIG. It did not penetrate into the cord from between the strands, and a complete composite of steel cord and rubber could not be formed. Therefore, the above steel cord 1
In the tire using No. 1, the cord and the rubber material are not sufficiently bonded to each other, so that the cord and the rubber material are separated during running of the vehicle, so-called separation phenomenon occurs, and a flare caused by contact between adjacent wires. A part of the cord was sometimes broken due to the marking phenomenon. Further, the moisture in the rubber or the moisture that has entered through the cuts of the tire is reduced by the void D.
And propagated in the longitudinal direction of the cord to generate rust on the entire steel cord, which was a cause of significantly reducing the mechanical strength of the steel cord.

[0004] In recent years, in view of the above circumstances, various steel cords have been proposed in which a rubber material can be expected to sufficiently enter the inside of the cord, even with this kind of twisted steel cord. For example, in Japanese Patent Application Laid-Open No. 9-256283, as shown in FIG. 7, two straight core strands 22 and one corrugated core strand 23 are arranged in the center of the cord. 3
By bundling the core strands without twisting them, it becomes a core,
A steel cord 21 having a 3 + n structure in which n (n = 6 to 11) side strands 24 are wound around the core is disclosed. The steel cord 21 is provided with a corrugated core wire 23 so that rubber can enter the core. However, this steel cord 21
Since the elongation of the straight core wire 22 is extremely low as compared with the elongation of the corrugated core wire, when a tensile load is applied to the cord, the straight core wire 22 is overloaded, and It will break. In this case, a load must be applied with the remaining wires, which eventually leads to cord breakage. In other words, when the steel cord 21 is viewed as a whole cord,
The cord has a poor balance of elongation of the constituent wires and is weak in strength. In addition, since the steel cord 21 needs to be in a non-twisted state with three core strands, only a tubular type twisting machine can be used, and an efficient double twisting buncher type twisting machine can be used. Not available.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned various problems of the prior art, and the rubber material penetrates to the inner center of the cord to completely separate the cord and the rubber material. An object of the present invention is to provide a practical steel cord which can form a composite, has a good balance of elongation of each strand, and has a low twisting cost.

[0006]

Means for Solving the Problems To solve the above problems, the steel cord of the present invention has 7 to 9 side strands arranged around three core strands constituting a core. So-called 1 × twisted strands in the same direction and pitch at the same pitch
Assuming a steel cord having an n structure (n = 10 to 12), the core is composed of two kinds of core strands having different curly shapes, and a rubber material is penetrated to the inner center of the steel cord. The balance of the elongation of each strand constituting the steel cord is improved. That is, in the steel cord of the present invention, one or two of the three core strands have a habit pitch P ₁ = 0.2P-
0.7P (where P is the cord twist pitch), habit outer diameter d
₁ = (d + 2/100 mm) to (d + 2/10 mm)
[Where d is the diameter of the element wire] has a substantially spiral shape defined by the following equation, and the remaining two or one core element have a wave pitch P ₂ = 0.2 P to 0.7 P, and a wave height of H = 2/100
It is characterized by having a substantially wavy shape defined by mm to 2/10 mm.

According to the structure of the present invention, a minute gap through which a rubber material can enter is formed between each side strand and between each core strand,
The rubber material is fully penetrated into the center of the steel cord. Further, a core element wire having a small, substantially spiral shape (hereinafter, referred to as a spiral core element wire) and a core element wire having a substantially wavy shape (hereinafter, referred to as a wave) are different from three twisted elements. (Referred to as “attached wires”), there is no core wire with extremely small elongation, and the balance between the core wires is balanced. In addition, since the balance between the elongation of the core strand and the elongation of the side strand is well-balanced, the load applied to the cord is suitably distributed to each strand. Here, the reason why the core element is formed by combining two kinds of core elements, that is, a spiral core element and a corrugated element element is as follows. For example, when all three core strands are formed of spiral core strands, as shown in FIG. 5, the habits of the three core strands are synchronized, and a portion where the core strands come into close contact with each other is generated. This is because voids are partially generated inside the cord, and the rubber penetration is reduced. Therefore, by combining two types of core strands, the core strands are prevented from adhering to each other, and the generation of a void inside the cord is prevented.

Further, the steel cord of the present invention has a 1 × n
Since the structure is a so-called bundle twist structure, it can be manufactured in one twisting step, and an efficient buncher twisting machine can be used. Therefore, the twisting cost can be significantly reduced as compared with the conventional 3 + 9 steel cord 21 shown in FIG.

[0009] Here, the habit spiral of the spiral Shinmotosen, the twist pitch of the cord in the habit pitch P ₁ is 0.2P~0.7P when is P, and the wire diameter d
Is habit outer diameter d ₁ when the (d + 2 / 100mm) ~
(D + 2/10 mm). The habit pitch P ₁ is more preferably 0.3 P to 0.6.
P range. In addition, the wavy habit of the above-mentioned corrugated strand is
A wave pitch P ₂ is 0.2P～0.7P, and wave height H is required to satisfy 2 / 100mm~2 / 10mm.
This is because, when less than 0.2 times the pitch P twist habit pitch P _1, will be added to excessive plastic deformation during processing habit to strand, decreases the strength of the wire, there is a risk of breakage Because. Also, if it is larger than 0.7 times,
Tensile and compressive forces due to the flow of rubber material during tire molding,
Alternatively, the ironing force applied to the cord surface reduces the gap between the strands, and the penetration of the rubber material becomes insufficient. For the same reason, the wave pitch P ₂ is 0.2P~0.
The range of 7P is good. Also, the habit outer diameter d ₁ is d + 2/10
If it is smaller than 0 mm, even if a rubber material having good fluidity is used, penetration of the rubber material into the inside of the steel cord during processing and vulcanization is not sufficient. This is because the fatigue property is reduced.
For the same reason, the wave height H is 2/100 mm to 2/10 m
The range of m is good.

The habit outer diameter d ₁ is the apparent outer diameter of the spiral core wire 2 as shown in FIG.
Further, the habit pitch P _1, as shown in FIG. 2, means the pitch of the habit of different small spiral and habit for the twisted cord. Also, the wave pitch P of the corrugated core element wire 3
_As shown in FIG. 3, the term ₂ and the wave height H refer to the distance between the vertices of two wavy waves and the distance between the vertices and the valley. The core element wire configured as a steel cord is given not only a regular spiral shape or a corrugated shape but also a habit shape in which this kind of habit and a twisted spiral habit of the cord are combined.

[0011]

FIG. 1 shows an example of a steel cord according to the present invention. This steel cord 1 has two spiral core strands 2 and one corrugated core strand 3 as cores, and eight side strands 4 arranged around the core.
It has a 1 × 11 structure in which two strands are simultaneously twisted. The steel cord 5 in FIG. 4 has one spiral core strand 2 and two corrugated core strands 3 as cores,
The side strands 4 are arranged, and these strands are simultaneously twisted. The substantially spiral small habit of the spiral core element wire 2 can be applied by a known rotating hammering means (for example, disclosed in Japanese Patent Publication No. 63-63293). In addition, the wavy small habit of the corrugated core element wire 3 is formed by using a hammering means having a hammering pin arranged in a staggered manner, and the strand is fixed to the hammering pin in a stationary state without rotating the hammering means. It can be applied by passing in a zigzag pattern.

Although the steel cord of the present invention can be manufactured by a buncher twister or a tubular twister, a great advantage is that a buncher twister having a high twisting efficiency can be used. In addition, if the above-mentioned rotation hammering means and the hammering pin are connected to the twisting machine, the space can be saved. Further, by adjusting the interval and diameter of the hammering pins, the number of twists of the strand, the tension, and the like, a desired habit can be imparted.

If the wire diameter d of the wire is too small, the strength is insufficient, and if it is too thick, the flexibility is poor.
It is preferably in the range of 30 mm. In addition, the wires constituting the steel cord have a carbon content of 0.70 to 1.0.
By using 00% by weight of carbon steel wire, high strength and good toughness can be provided. A particularly preferred range of the carbon content is 0.80 to 0.90% by weight. Further, each of the above-mentioned wires is plated with brass plating, bronze plating or the like in order to improve the adhesion between the rubber material and the steel cord.

It is a common sense to apply twisting to a substantially straight side wire in advance so that good twisting can be achieved. It is much larger and has a completely different effect.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. In FIG. 1, reference numeral 1 denotes a steel cord. The steel cord 1 is composed of eleven wires having the same wire diameter with a wire diameter d = 0.22 mm, and is disposed substantially at the center of the steel cord. Two of the core strands are spiral core strands 2 having a habit pitch P ₁ = 6 mm and a habit outer diameter d ₁ = 0.28 mm, and the remaining one core strand The line is a corrugated core element wire 3 having a wave pitch P ₂ = 6 mm and a wave height H = 0.1 mm. Then, a substantially straight 8 around the central three core strands
The side strands 4 are arranged, and these eleven strands are twisted in a twist pitch of 12 mm in the S twist direction.

Next, in order to examine the performance of the steel cord of the present invention, a steel cord of a comparative example, a conventional steel cord and other examples were manufactured, and a rubber penetration rate, a fatigue resistance,
Test evaluation was performed on the twisting cost. The wires constituting each of the steel cords used in the test were all high carbon steel wires having a carbon content of 0.82% by weight, and the surfaces thereof were subjected to brass plating.

[0017] In this evaluation item, the "rubber penetration rate" means that each steel cord was embedded in a rubber material while a tensile load of 5 kg was applied, the steel cord was taken out after vulcanization, and the steel cord was disassembled. A constant length was observed for each of the strands, and the ratio of the observed length to the length of the trace in contact with the rubber material was expressed as a percentage.
The rubber penetration rate was evaluated for the entire cord and the core strand, respectively. The rubber penetration rate is preferably 70% or more.
"Fatigue resistance" means that multiple steel cords were embedded in a rubber sheet, and after vulcanization, the sheet was set on a three-point pulley bending fatigue tester to determine the number of repetitions until breakage due to fretting wear, buckling, etc. Experiment No. 3 which is a conventional 3 + 9 steel cord. 13 codes to 10
It is expressed as an index as 0. The larger the numerical value, the better the fatigue resistance. “Twisting cost” is the cost required for the steel cord twisting step, and is calculated from the manufacturing difficulty, the manufacturing time, the number of steps, the handling cost, and the power consumption. This is also the experiment No. 13 steel cords were set to 100 and indexed. The lower the numerical value, the better the twist cost. Table 1 summarizes the evaluation results of these tests.

[0018]

[Table 1]

As is clear from the above table, the steel cord of the present invention is excellent in all of rubber penetration, fatigue resistance and twisting cost, and is superior to the conventional steel cord in each step. I got an evaluation.

[0020]

Since the steel cord of the present invention has the above-described structure, a rubber infiltration path from the outer periphery of the cord to the cord core is formed, and the rubber material surely penetrates to the inside of the cord, thereby completely forming a composite with the rubber material. Be a body. In addition, the three core strands have an appropriate elongation, and the elongation of the core strand and the side strands are well balanced, so that the load applied to the cord is appropriately distributed to each strand. Therefore, when the steel cord of the present invention is used for a carcass or a belt of a tire, fretting wear, separation phenomena and deterioration of the cord due to corrosion can be significantly reduced, and the fatigue life can be considerably extended. Therefore,
The life of the tire can be greatly extended. Moreover,
Excellent effects such as buncher twisting can be achieved and twisting cost can be reduced.

[Brief description of the drawings]

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

FIG. 2 is an explanatory diagram of a spiral core element wire.

FIG. 3 is an explanatory diagram of a corrugated core element wire.

FIG. 4 is a schematic sectional view of a steel cord according to another embodiment of the present invention.

FIG. 5 is an explanatory view of a core composed of only spiral core strands.

FIG. 6 is a schematic sectional view of a conventional steel cord having a 1 × 12 structure.

FIG. 7 is a schematic sectional view of a conventional improved 3 + 9 steel cord.

[Explanation of symbols]

 1,5 ... steel cord 2 ... spiral core strand 3 ... corrugated core strand 4 ... side strand

Claims (1)

[Claims] 1. Seven to nine side strands around three core strands
And twist these wires in the same direction and pitch.
1xn (n = 10 to 12) structured steel
In the cord, one or two of the above core strands
But habit pitch P₁ = 0.2P to 0.7P [where P is
Cord twist pitch], habit outside diameter d₁ = (D + 2/100
mm) to (d + 2/10 mm) [where d is the element diameter]
Has a substantially spiral shape, and the remaining two
Or one core strand has a wave pitch P _Two = 0.2P-0.7
P, approximate wave height H = 2/100 mm to 2/10 mm
A tire reinforcing stiffener having a wavy habit
Code.