JP2597836Y2 - 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 Generally, a steel cord of this kind is used as a reinforcing material for rubber products such as automobile tires and conveyor belts, in which a large number of steel cords are covered with a rubber material in a state of being aligned in parallel. It is.

As a conventional rubber product, for example, a steel cord for reinforcing a heavy-duty pneumatic radial tire, as shown in FIG. 4, nine lateral elements 8 are disposed around three core strands 8 arranged substantially at the center. There is known a so-called 1 × 12 steel cord 7 in which wires 9 are arranged and twelve strands having the same wire diameter are densely twisted in the same direction and at the same pitch.

As shown in FIG. 5, a core strand 1 composed of three core strands 11 tightly twisted is used as a steel cord having the same number of strands as the steel cord 5.
There is also known a so-called 3 + 9 steel cord 10 in which nine side strands 13 are densely twisted around 2 in a direction or a pitch different from the above-mentioned twisting.

[0005] The steel cord 7 having the 1 × 12 structure is
The steel cord 10 having the 3 + 9 structure requires two twisting steps, but can be produced by one twisting step, so that there is an advantage that the twisting cost can be reduced.

However, in the above-mentioned steel cord 7, since the adjacent wires are closely or extremely close to each other, the rubber material cannot penetrate inside between the wires at the time of molding the rubber product. , It was not possible to form a complete composite with rubber. Therefore, in the tire using the steel cord 7, since the adhesion between the cord and the rubber material is not sufficient,
In some cases, the cord and the rubber material are separated from each other when the automobile is running, so-called a separates phenomenon, or a part of the cord is broken by a fretting phenomenon caused by contact between adjacent strands. Further, the so-called water in the rubber or the water penetrating from the cuts of the tire reaches the gap D formed by being surrounded by the adjacent wires, and propagates in the longitudinal direction of the cord to generate rust on the entire steel cord. Corrosion occurred, causing a significant decrease in the mechanical strength of the steel cord.

[0007] In recent years, in view of the above circumstances, various steel cords have been proposed in which even such a twisted steel cord can be expected to sufficiently infiltrate a rubber material into the cord.

For example, in Japanese Patent Application Laid-Open No. 56-163905, as shown in FIG. 6, a core strand 16 in which three core strands 15 are twisted and a gap T provided around the core strand are provided. There is disclosed a so-called open cord (hereinafter referred to as an open cord) having a loosely twisted steel cord 14 composed of the arranged side wires 17. This allows
The purpose is to sufficiently infiltrate the rubber material into the cord from the gap T.

Also, Japanese Utility Model Laid-Open No. 4-60590 discloses that
As shown in FIG. 8, a steel cord 18 for reinforcing rubber products having a 1 × 12 structure comprising a habitually twisted wire 19 having a substantially spiral small habit having an apparent outer diameter d ₁ and a normal wire 20. Is disclosed. Thus, a rubber infiltration path with a minute gap formed between the strands is provided to improve the infiltration of the rubber material.

[0010]

However, in the open cord 14, since the twist is weak in the entire longitudinal direction, the twist tends to be unstable as apparent from the structure thereof, and as shown in FIG. Since the displacement of the strand 17 occurs locally, a phenomenon occurs in which the twist becomes uneven in the longitudinal direction of the cord. In such a case, even if the rubber penetrates to the center of the cord, when formed into a composite material with the rubber, adverse effects such as a change in bending rigidity in the longitudinal direction or a deterioration in compression bending fatigue locally. There is. Therefore, when this composite material with rubber is used by incorporating it into a tire,
Since stable tire rotation cannot be obtained, ride comfort deteriorates. In addition, a plurality of strands of steel cord do not produce an integrated effect, and one or
A phenomenon occurs in which the book is cut extremely quickly, which not only deteriorates the performance of the tire but also shortens the life. Also, at the time of cord production, the twist is not stable,
Since twisting failure and disconnection occur, twisting cost and workability deteriorate.

Further, the steel cord 18 is excellent in that the penetration of the rubber material is improved while maintaining the stability of twist. However, when the steel cord 18 is made of a composite material with rubber, the open cord 1
4 is inferior to the compression fatigue property as compared with 4. Because the gap between the wires in the steel cord 18 is minute compared to the gap between the wires in the open cord 14, the gap between the wires is formed when a composite material with rubber is formed and receives a compressive force. This is because the fretting phenomenon cannot be completely prevented, and as a result, the compression fatigue property is reduced. Also, the bending rigidity is inferior to the open cord 14. Because when the same strand is used, the cord diameter is open cord 1.
4 is larger than the steel cord 18, so that the bending resistance when formed into a composite with rubber increases substantially in proportion to the cord diameter. According to the research of the inventor, the bending stiffness of the steel cord 18 is equal to that of the open cord
It is 5-15% inferior to that of 4.

The present invention has been made to solve the above problems, and can improve the penetration rate of rubber into the inside of a cord, and can reduce the bending rigidity and compression bending fatigue when formed into a composite with rubber. It is an object of the present invention to provide a steel cord for reinforcing a rubber product having a novel configuration capable of improving the twisting cost and workability.

[0013]

In order to achieve the above-mentioned object, a rubber cord for reinforcing a rubber product according to the present invention is provided around a core formed by twisting three core strands having the same wire diameter.
Nine side strands having the same diameter as this core strand are arranged as an outer layer, and these 12 strands are twisted in the same direction and at the same pitch. At least one of the three core wires constituting the core is represented by the formula: P ₁ = 0.1 P to 0.7 P d ₁ = 1.08d to 1.30d (where P ₁ : habit Pitch (mm), P: twist pitch (mm), d ₁ : apparent spiral diameter (mm), d: wire diameter (mm)) Three of the wires fall into the recesses between the three core strands of the core, and a total of six strands form a substantially equilateral triangle,
An average gap C between the remaining six side wires of the outer layer and the wires forming the substantially equilateral triangle satisfies the following expression: 0.02 mm ≦ C ≦ 0.50d, and the outer layer is provided on each side of the substantially equilateral triangle. The remaining six side strands are divided and arranged two by two.

By the way, the above-mentioned various numerical limitations are determined based on the results obtained by a number of experiments, and the outline thereof is as follows.

Assuming that the twisting pitch of the spiral habit is P, the habit pitch P ₁ is P ₁ = 0.1 P to 0.7 P
And the wire diameter is d, the apparent outer diameter d ₁ is d ₁
= Was in the range of 1.08d~1.30d, when less than 0.1 times the pitch P twist habit pitch P _1, during the imprint of the strand, the addition of excessive plastic deformation to wire This is because the strands are 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. Further also be used as the outer diameter d ₁ of the apparent smaller than 1.08d fluidity good rubber material can not rubber material is sufficiently penetrating into the interior steel cord pressurized and vulcanization, 1. If it is larger than 30 d, the twisting stability will be poor and the fatigue resistance will be reduced.

When the average distance C between the remaining six side wires of the outer layer and the wires forming the substantially equilateral triangle is less than 0.02 mm,
Insufficient rubber penetration, resulting in reduced flexural rigidity and compressive flexural fatigue. On the other hand, when C exceeds 0.50d, the rate of occurrence of poor twisting in the twisting step increases, and the twisting cost and workability deteriorate.

The size of the average gap C can be controlled by adjusting a straightening roller provided at the entrance of the twisting machine.

In order to satisfy the strength and flexibility required for the steel cord,
A range of 0.15 to 0.30 mm is appropriate.

It should be noted that the substantially spiral habit in the present invention does not need to be exactly spiral, but may be simply wavy, and has the same effect as the spiral. is there.

[0020]

The steel cord constructed as described above is
When pressed and vulcanized while sandwiching between two rubber sheets, a gap formed between the nine side strands forming the outer layer of the steel cord and a gap formed between the three core strands forming the core were formed. Due to the minute space, the rubber material sufficiently penetrates into the cord.

With this rubber material, the periphery of each element wire is covered to form a complete composite of rubber and cord, and the strength of the steel cord due to fretting, separation, and corrosion is prevented from being reduced.

In addition, three of the side strands of the outer layer fall into the recesses between the three strands of the core, and the structure of the approximately equilateral triangle formed by the six strands in total is a stable structure. In addition, the remaining six side strands of the outer layer are arranged two by two with an appropriate gap provided on each side of the substantially equilateral triangle, and do not move to the other side. When formed as a composite material, the change in bending stiffness and fatigue resistance in the longitudinal direction of the steel cord is small, and shows a stable and good value.

[0023]

An embodiment of the present invention will be described below with reference to the drawings.

Example 1 As shown in FIG. 1, around a core formed by twisting three core wires having a wire diameter d = 0.22 mm, the same wire diameter as the core wire is used. Are arranged, and these 1
Two strands in S twist direction, twist pitch P = 12.5mm
And a steel cord 1 for reinforcing rubber products having a 1 × 12 structure was formed.

The core has a custom pitch P ₁ of 1.4 mm.
Thus, one core wire 2 having a substantially spiral small habit having an apparent outer diameter d ₁ of 0.24 mm and two substantially straight core wires 3 having no habit are provided. Become.

Three of the nine side strands fell between the three core strands, and the six strands formed a substantially equilateral triangle. The remaining six side strands were distributed two on each side of the substantially equilateral triangle. The average gap C obtained by averaging the gaps Ci between the strands forming the substantially regular triangle and each of the six side strands was 0.04 mm.

Example 2 As shown in FIG. 2, around a core formed by twisting three core strands having a wire diameter d = 0.22 mm, a wire having the same wire diameter as this strand is formed. Nine side wires 4 are arranged, and these 12
These strands were twisted in the S twist direction and twist pitch P = 12.5 mm to form a rubber cord reinforcing steel cord 5 having a 1 × 12 structure.

[0028] The core is, habit pitch P ₁ is 4.1mm
The two core strands 2 having a substantially spiral shape having an apparent outer diameter d ₁ of 0.26 mm and a single straight strand 3 having no habit are formed. Become.

Example 3 As shown in FIG. 3, around a core formed by twisting three core strands having a wire diameter d = 0.22 mm, a wire having the same diameter as this strand is formed. Nine side wires 4 are arranged, and these 12
These strands were twisted in the S twist direction and twist pitch P = 12.5 mm to form a rubber cord reinforcing steel cord 6 having a 1 × 12 structure.

[0030] The core is, habit pitch P ₁ is 8.1mm
It consists of three core strands 2 having a substantially spiral small habit and an apparent outer diameter d ₁ of 0.28 mm.

The outline of the manufacture of the steel cord in each of the above embodiments will be described. It is sufficient to twist 12 strands by a known twisting device. In this case, the inner three strands are The outer nine strands may be interchanged, resulting in poor twisting, so the inner three core strands are slightly twisted first and then twisted so that the nine outer strands are arranged on the outer layer. Is good.

By the way, some spiral small habits of the inner three core strands are described in JP-B-63-632.
As shown in 93 JP, with in attaching device habit rotated strands supplied as axial, it is intended to impart an outer diameter d ₁ of the apparent and desired habit pitch P _1. At this time, in order to adjust the desired habit pitch P ₁ and the apparent outer diameter d ₁ , the interval and size of the hammer pins and the number of rotations with the element wire as the axis are adjusted.

A steel wire having a carbon content of 0.70 to 0.95% by weight is used for the wire constituting the steel cord. However, in order to give the steel cord a high strength and good toughness, a carbon content is required. It is more preferable to use a steel wire having an amount of 0.80 to 1.05% by weight.

Incidentally, the carbon content is 0.80 to 1.0.
In the range of 5% by weight, it was confirmed that the average gap C tends to increase as the carbon content increases when twisted under the same twisting conditions. This is probably because the higher the carbon content, the more difficult it is for the strand to plastically deform.

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

Next, in order to confirm the performance characteristics of the steel cord of the present invention, in addition to the above embodiment, the habit pitch P ₁ , the apparent outer diameter d ₁ , and the average distance C of the core wire are varied. The steel cords of other Examples and Comparative Examples and a conventional steel cord were subjected to a comparative test, and a rubber penetration rate,
When the bending rigidity, compression bending fatigue, twisting cost, and workability of the composite with rubber were evaluated, the results shown in Table 1 were obtained. The wires constituting each cord used in the experiment all had a carbon content of 1.01% by weight, and the surface thereof was subjected to brass plating.

At the time of evaluation, the rubber infiltration rate was determined by applying a rubber material having a 100% modulus of 35 kg / cm ² under a tensile load of 5 kg to each cord (an ordinary rubber used as a breaker for a tire in which a steel cord is embedded). After embedding in the material) and vulcanizing under pressure, the cord is extracted, the cord is disassembled, a certain length is observed for each strand, and the area of the area where there is evidence of contact with the rubber is The ratio was determined as a percentage and the average was displayed. Usually, this value needs to be 75% or more.

The bending stiffness was determined by embedding five steel cords in a rubber sheet having a thickness of 5 mm and vulcanizing under pressure.
A load was applied to the center while supporting both points at an interval of 1 cm, and the load required to deflect this sheet by 5 mm was measured.
And 100 as an index.

The compressive fatigue resistance was determined by embedding a plurality of steel cords in a rubber material having a 100% modulus of 35 kg / cm ² to form a composite sheet, and using this sheet by a three-point pulley bending fatigue tester. , The number of repetitions until the cord was broken after fretting wear, buckling, etc., was calculated.

The twisting cost and workability are comprehensive evaluations of the number of twisting steps in the production of steel cord, the complexity of the work, and the handleability of the cord. Excellent was evaluated as 、, and very excellent was evaluated as ◎.

[0041]

[Table 1]

Table 1 shows that Conventional Example 1 of Experiment No. 13
Is a tight-twisted 1 × 12 steel cord whose cross-sectional structure is shown in FIG. 4. Since the strands are densely twisted, the rubber penetration rate is extremely poor, and the bending rigidity and compression fatigue resistance are poor. I have. Conventional Example 2 of Experiment No. 14 is a steel cord having a 3 + 9 structure whose cross-sectional structure is shown in FIG. 5, and the rubber penetration rate cannot be said to be sufficient, and the compression fatigue property is inferior.

In Comparative Example 1 of Experiment No. 7, P ₁ = 0.07P, d
₁ = for the outer diameter d ₁ of a 1.05d apparent and habit pitch P ₁ of habit substantially spiral small core wire is too small, the work and disconnection occurs twisted costs imprint when the wires Sex has become worse. Also, rubber penetration is not sufficient, and compression fatigue properties are slightly inferior. In Comparative Example 2 of Experiment No. 8, P ₁ = 0.8 P, and the small spiral habit pitch P ₁ of a substantially spiral shape of the core element wire is too large, so that rubber penetration is inferior and compression fatigue property is slightly inferior. In Comparative Example 3 of Experiment No. 9, d ₁ = 1.05d, and the apparent outer diameter d ₁ of the substantially spiral small habit of the core wire is too small, so that the rubber infiltration is inferior and the compression fatigue property is slightly inferior. . In Comparative Example 4 of Experiment No. 10, d ₁ = 1.45d, and the apparent outer diameter d of a small spiral having a substantially spiral shape of the core wire.
_{Since 1} was too large, poor twisting occurred. Also, the compression fatigue properties are slightly inferior. In Comparative Example 5 of Experiment No. 11, the average gap C was 0.01 mm.
And too small, resulting in poor rubber penetration, poor bending rigidity and poor compression fatigue. In Comparative Example 6 of Experiment No. 12, the average gap C was 0.55 d.
(0.12 mm), which was larger than 0.50 d, so that twisting failure occurred. Also, the compression fatigue properties are slightly poor.

On the other hand, in Experiment No. The steel cords of the present invention of 1 to 6 have rubber penetration, bending rigidity, compression fatigue resistance,
It was satisfactory in both the twisting cost and workability, and proved to have excellent performance as a rubber product reinforcing material.

[0045]

Advantages of the Invention The steel cord for reinforcing rubber products of the present invention has a stable twist structure in the longitudinal direction of the cord at the time of cord production, has no deviation of strands, and does not have poor twisting. In addition, when the steel cord is covered with rubber material, the rubber material surely spreads between the wires constituting the steel cord, making it a complete composite with rubber material. And the code separation phenomenon can be prevented. Therefore, buckling is not easily generated even when repeated bending stress is applied, and the wear resistance due to the fretting phenomenon is small, so that the fatigue resistance is excellent. Further, since the bending stiffness is stabilized and improved in the longitudinal direction, the amount of steel cord embedded in the rubber material can be reduced, and an excellent effect such as reduction in weight of the tire can be achieved.

[Brief description of the drawings]

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

FIG. 2 is a sectional view illustrating a steel cord according to a second embodiment of the present invention;

FIG. 3 is a sectional view showing a steel cord according to a third embodiment of the present invention;

FIG. 4 is a sectional view showing a conventional steel cord having a 1 × 12 structure.

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

FIG. 6 is a sectional view showing a conventional open cord having a 3 + 9 structure.

FIG. 7 shows a conventional 3 + 9 open code.
It is explanatory sectional drawing which shows the state in which the side strand shifted.

FIG. 8 is a cross-sectional view showing a conventional steel cord having a 1 × 12 structure composed of a conventional wire having a substantially spiral shape and a normal wire.

[Explanation of symbols]

 1, 5, 6, 7, 10, 14, 18 Steel cord 2 Core strand having a substantially spiral small habit 3, 8, 11, 15 Core strand 4, 9, 13, 17 Side strand 12, 16 Core strand 19 A wire having a substantially spiral small habit 20 A wire

Claims (1)

(57) [Scope of request for utility model registration] 1. Around a core formed by twisting three core wires having the same wire diameter, nine side wires having the same wire diameter as the core wire are arranged as outer layers, and these 12 wire wires are arranged. In a steel cord for reinforcing rubber products having a 1 × 12 structure, which is obtained by twisting the above-mentioned strands in the same direction and at the same pitch, at least one of the three core strands constituting the core has the formula: P ₁ = _0.1P~0.7P d ₁ = _1.08d~1.30d (However, P _1: habit pitch (mm), P: twist pitch (mm), d _1: the outside diameter of the apparent (mm), d: wire diameter (mm)), and three of the outer layer side wires fall into the recesses between the three core wires, and a total of six wires Form a substantially equilateral triangle,
An average gap C between the remaining six side wires of the outer layer and the wires forming the substantially equilateral triangle satisfies the following expression: 0.02 mm ≦ C ≦ 0.50d, and the outer layer is provided on each side of the substantially equilateral triangle. A steel cord for reinforcing rubber products, characterized in that the remaining six side strands are divided and arranged two by two.