JP2560976Y2 - 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, conveyor belts, etc., in which a large number of steel cords are coated in parallel 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. 4A, nine wires are arranged around three wires arranged substantially at the center. Lines are arranged, and one having the same wire diameter
A steel cord 5 having a polygonal cross section in which two strands 6 are densely twisted in the same direction and at the same pitch, that is, a steel cord 5 having a so-called 1 × 12 structure is known.

[0004] Further, as a steel cord having the same number of wires as the steel cord 5, as shown in FIG.
A strand 9 consisting of three strands 8 densely twisted
Around in a different direction or pitch from the twist
There is also known a so-called 3 + 9 structure steel cord 7 in which the strands 10 are densely twisted.

The steel cord 5 having the 1 × 12 structure is
The steel cord 7 having the 3 + 9 structure requires two twisting steps, but can be produced in one twisting step. Therefore, the production time can be shortened without having many expensive twisting facilities. Is also possible, and has the advantage that the production cost can be reduced.

However, in the steel cord 5, since the adjacent wires 6, 6 are closely or extremely close to each other, the rubber material can penetrate into the steel cord 5 between the wires 6, 6 during molding. However, simply covering the outer periphery of the cord could not form a complete composite with rubber. Therefore, in the tire using the steel cord 5, 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, that is, a so-called separation phenomenon occurs, and the adjacent element is not used. A part of the cord was sometimes broken due to the fretting phenomenon caused by the contact between the wires. Further, the moisture in the rubber or the moisture that has entered 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, thereby causing the steel cord to rust. This greatly reduced the mechanical strength of the steel.

[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 penetrate a rubber material into the cord.

For example, as shown in FIG. 5, a steel cord 13 disclosed in Japanese Patent Laid-Open Publication No.
Nine wires 12 whose wire diameters are slightly smaller than the wire diameters are arranged around the three wire wires 11 arranged substantially at the center,
A gap C is provided between the strands 12, which are twisted in the same direction and at the same pitch, so that a sufficient rubber material does not penetrate into the cord from the gap C.

[0009]

However, in the steel cord 13 as well, the three strands 1 arranged substantially at the center are used.
1 has a gap D substantially at the center, and it is not possible to attain the desired sufficient rubber material infiltration, thereby causing the various adverse effects described above. The present invention has been made in view of the above-described problem, and has a rubber infiltration path extending from the outer periphery of the cord to a central gap, greatly improving the infiltration of the rubber material, and a complete composite with the rubber material. It is an object of the present invention to provide a steel cord for reinforcing rubber products.

[0010]

In order to achieve the above object, a rubber cord for reinforcing a rubber product according to the present invention has nine identical wires around a wire having three identical wire diameters (d ₁ ). In a steel cord for reinforcing rubber products having a 1 × 12 structure in which wires having a diameter (d ₂ ) are arranged, and these 12 wires are twisted in the same direction and at the same pitch, the above-mentioned three wires and 9 lines of wire diameter ratio d ₁ / d ₂ = 1.02~1.
25 and at least one of the wire diameters of the three strands.
Book pitch P ₁ = 4d _{1 to} 35d ₁ , apparent outer diameter d ₀
= 1.08 d _{1 to} 1.5 d ₁ .

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. The reason why the wire diameter ratio of the three wires and the nine wires is d ₁ / d ₂ = 1.02 to 1.25 is that when the wire diameter ratio is smaller than 1.02, the gap C between the wires is set. This is because the desired width of the rubber material cannot be expected, and if the width is larger than 1.25, the shape becomes poor and the core pops out.

It is also conceivable to make the wire diameter ratio smaller than 1.02 and increase the apparent outer diameter d _{0. In} this case, however, the spiral shape of the rubber product is reduced due to the tension applied to the steel cord during molding. Easy to deform,
It is not a good idea because it makes it difficult for rubber to enter.

Further, if the warp pitch P ₁ is smaller than four times d ₁ , the wire will be subjected to excessive plastic deformation during the warping of the wire, and the wire will be easily broken and the productivity will be reduced. On the other hand, if it is larger than 35 times, the gap between the wires decreases due to the tensile force due to the flow of the rubber material during the molding of the rubber product or the ironing force applied to the cord surface, and the rubber material does not penetrate sufficiently.

Further, when the apparent outer diameter d ₀ is smaller than 1.08 times d ₁ , the rubber material sufficiently penetrates into the steel cord during the pressure vulcanization even when a rubber material having good fluidity is used. If it is not more than 1.5 times, 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 need to be exactly spiral, and even if it is simply wavy, it exhibits the same effect as the spiral. Such a shape is also included.

[0016]

[Operation]

When the steel cord constructed as described above is pressed and vulcanized by being sandwiched between two rubber sheets, the rubber material enters the inside of the cord through a rubber infiltration path of a minute gap formed between the strands. It penetrates and forms a composite with a complete rubber material, preventing the steel cord from being strongly degraded due to fretting phenomena, separation phenomena and corrosion.

[0018]

[Example] Hereinafter, the steel cord for reinforcing rubber products of the present invention will be described in detail with reference to examples. (Embodiment 1) In FIG. 1, nine wires 4 having the same wire diameter d ₂ are arranged around three wires 3 having the same wire diameter d ₁ , and these 12 wires are used. It is a 1 × 12 structure that is twisted in the same direction and at the same pitch.
A steel cord is formed in which the strands 2 have a substantially spiral small habit. With this configuration, the wire diameter d _{1 of the} three wires 2 and 3 is 0.32 mm, and the nine wires 4
Diameter d ₂ = 0.30 mm, small spiral pitch P ₁ = 4.0 mm, apparent outer diameter d ₀ = 0.4
An example in which the twist pitch of the cord was 6 mm and the cord twist pitch P was 15 mm is shown in Table 1. 8, d ₁ = 0.36 mm,
d ₂ = 0.30 mm, P ₁ = 2.0 mm, d ₀ = 0.46
mm, P = 15 mm, the experiment No. of Table 1 was used. 9
Shown in

(Embodiment 2) In FIG. 2, the structure is substantially the same as that of Embodiment 1,
Two of the wires 2 having the same wire diameter d ₁ have a substantially spiral small habit. Diameter d ₁ of the three wires 2,3 in this configuration = 0.31 mm, 9 strands 4 of diameter d ₂ = 0.30 mm, the pitch P ₁ = 8 of habit substantially spiral small 0.0 mm, apparent outer diameter d ₀ =
An example in which the twist pitch of the cord was set to 0.43 mm and the cord twist pitch P was set to 15 mm was shown in Experiment 1 of Table 1. 11, d ₁ = 0.3
2 mm, d ₂ = 0.30 mm, P ₁ = 4.0 mm, d ₀ =
An example in which 0.38 mm and P = 15 mm were set in Experiment No. 1 in Table 1. 12, and d ₁ = 0.36 mm, d ₂ =
0.30 mm, P ₁ = 2.0 mm, d ₀ = 0.40 mm,
An example in which P = 15 mm is shown in Experiment 1 of Table 1. FIG.

(Embodiment 3) FIG. 3 is different from Embodiment 1 and Embodiment 2 in that a steel cord in which all of the three strands 2 have a substantially spiral small habit is shown. Have been. The wire diameter d ₁ 3 strands 2 in this configuration = 0.26 mm, 9 pieces of wire diameter d ₂ = 0.25 mm of the wire 4, the habit substantially spiral small pitch P ₁ = 8.0 mm, Apparent outer diameter d ₀
= 0.37 mm and the cord twist pitch P = 12 mm. 15, d ₁ = 0.
28 mm, d ₂ = 0.25 mm, P ₁ = 4.0 mm, d ₀
= 0.35 mm and P = 12 mm are shown in Table 1. 16, and d ₁ = 0.30 mm, d ₂ =
0.25 mm, P ₁ = 2.0 mm, d ₀ = 0.33 mm,
An example in which P = 12 mm was used in Experiment No. 1 in Table 1. 17 is shown.

A brief description of the manufacture of each of the above steel cords is as follows. Twelve strands may be simultaneously twisted by a known twisting device. In this case, the three inner strands and the outer nine strands are used. Since the strands may be replaced and the twist may be poor, it is preferable that the three inner strands are slightly twisted first, and the outer strands are arranged such that nine strands are arranged.

By the way, some spiral small habits of the inner three strands are disclosed in JP-B-63-6329.
As disclosed in Japanese Unexamined Patent Publication (Kokai) No. 3 (1999) -2002, a desired habit pitch P _{1 is obtained} by a hammering device that rotates around a supplied strand.
And an outer diameter d ₀ . In this case in order to impart the outer diameter d ₀ of the apparent and desired habit pitch P ₁ adjusts the rotational speed of the rotation interval of the imprint pins, the dimensions and strand as axial.

[0023] In the above embodiments, it is preferred that the wire diameter d ₂ of the wires 4 is in the range of 0.15～0.40Mm. The reason is that when the wire diameter d ₂ is less than 0.15 mm, the strength of the steel cord is insufficient, while the strength of the steel cord is less than 0.15 mm.
If it exceeds 40 mm, the flexibility is inferior.

Further, a steel wire having a carbon content of 0.70 to 0.90 wt% is usually used as a wire constituting the steel cord. However, in order to give the steel cord 1 high strength and good toughness, Each strand 4 has a carbon content of 0.80
It is preferred to use ~ 0.85 wt% steel wire.

Further, in order to improve the adhesion between the rubber material and the steel cord 1, Cu, Zn
It is preferable to use a brass-plated material whose main component is.

Further, in order to further improve the twisting stability of the steel cord 1, a single wire (for example, 0.1 mm) having a diameter smaller than that of the cord constituting wire 4 is provided around the steel cord 1.
(15 mm diameter).

Next, in order to confirm the performance characteristics of the steel cord of the present invention, a comparison test between the steel cord of the present invention described in the above embodiment and a conventional steel cord was performed.
Evaluation of rubber material infiltration, salt water rubber adhesion coverage, fatigue, fretting amount and handling workability,
The results as shown in Table 1 were obtained.

It should be noted, in the NS table, the number of small shaping wire of spiral, d ₀ is the habit outer diameter, P ₁ Hakuse pitch, d ₁ is the three strands arranged substantially at the center The wire diameter, d _2, is the wire diameter of the nine wires arranged around d ₁ . In addition, RP is the penetration rate of the rubber material, RC is the salt water adhesion rubber coverage, R
F represents fatigue, and CO represents manufacturing cost.

[0029]

[Table 1]

At the time of this evaluation, the rubber material penetration rate RP
(%) Is a rubber material having a 100% modulus of 35 kg / cm ² (a normal rubber material used for a breaker of a tire in which a steel cord is embedded) under a tensile load of 5 kg applied to each cord. After embedding and vulcanizing, take out the steel cord, disassemble the cord, observe a certain length between each strand, and calculate the ratio of the length of the trace that has been in contact with the rubber material to the observed length as a percentage. And the average was displayed. This value needs to be 70 or more.

The salt water adhesive rubber coverage ratio RC (%) is determined by AST
MD2229, after preparing a rubber-steel cord vulcanized specimen based on a steel cord adhesion test, the bottom of the specimen was
% Of sodium chloride aqueous solution for 10 days, followed by a pull-out test, and the rubber coverage of the cord surface after pull-out was indicated. This value needs to be 60% or more.

For the fatigue RF, a plurality of steel cords are used.
A 100% modulus is embedded in a rubber material having a modulus of 35 kg / cm ² to form a composite sheet. Using this sheet, the cord breaks through fretting wear, buckling, etc. using a three-point pulley bending fatigue tester. The number of repetitions up to this point was determined, and the code of Conventional Example 1 was set to 100 and displayed as an index. The higher the value, the better the fatigue.

The production cost CO is the cost of obtaining each code, and is related to the difficulty of production, the production time, and the like. The lower the value, the better the manufacturing cost.

In Table 1, in the experiment No. 1
Is a 3 + 9 steel cord, which has a very stable twist, but is inferior in the penetration rate of the rubber material and the coverage rate of the salt water adhesive rubber.

Experiment NO. Reference numeral 2 denotes a steel cord having a 1 × 12 structure twisted with strands having the same wire diameter, and is excellent in manufacturing cost, but is inferior in the penetration rate of rubber material and the coverage rate of salt water adhesive rubber.

Experiment NO. Reference numeral 3 is a steel cord having a 1 × 12 structure twisted with strands having different wire diameters, and is excellent in fatigue property and manufacturing cost, but is inferior in rubber material infiltration property and salt water adhesive rubber coverage.

Experiment NO. 4 to 7, 10, 1
No. 4 is a steel cord having a 1 × 12 structure using a spiral wire having a small habit. 4
Is different from that of the present invention in the wire diameter ratio (d ₁ / d ₂ ), 5 to 7, 10 and 14 have different habit shapes from those of the present invention, so that all of the evaluation items cannot be satisfied.

On the other hand, in experiment NO. 8,
Steel cords Nos. 9, 11 to 13, and 15 to 17 satisfy all of the infiltration rate of the rubber material, the coverage ratio of the salt-water-adhesive rubber, the fatigue property and the production cost, and are proved to be optimal as a reinforcing material for rubber products. did.

[0039]

[Effect] The steel cord for reinforcing rubber products of the present invention is:
Because of the above configuration, a rubber intrusion path is formed from the outer periphery of the cord to the inside of the cord, and the rubber material is surely spread between the individual wires, so that a complete composite with the rubber material is obtained, and the corrosion of the cord can be prevented, The separation phenomenon between the rubber material and the cord can be prevented, and the fatigue life of the rubber product can be extended. In addition, buckling does not easily occur even when repeated bending stress is applied, and the amount of wear due to the fretting phenomenon is small, so that excellent effects such as excellent fatigue properties and reduction in manufacturing cost can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a steel cord according to a first embodiment.

FIG. 2 is a sectional view showing a steel cord according to a second embodiment.

FIG. 3 is a sectional view showing a steel cord according to a third embodiment.

FIG. 4A is a sectional view showing a conventional steel cord having a 1 × 12 structure. (B) is a sectional view showing a conventional steel cord having a 3 + 9 structure.

FIG. 5 is a cross-sectional view showing a conventional steel cord having a 1 × 12 structure using wires having different wire diameters.

[Explanation of symbols]

 1, 5, 7, 13 ... steel cord 2 ... strand having a small spiral in a substantially spiral shape 3, 4, 6, 8, 10, 11, 12 ... strand 9 ... strand

Claims (1)

(57) [Scope of request for utility model registration] 1. Nine wires having the same diameter (d ₂ ) are arranged around three wires having the same wire diameter (d ₁ ), and these twelve wires are placed in the same direction. In a steel cord for reinforcing rubber products having a 1 × 12 structure, which is twisted at the same pitch, the wire diameter ratio of the three strands and the nine strands is d ₁ /.
d ₂ = 1.02 to 1.25, and at least one of the three strands has a habit pitch P ₁ = 4d _{1 to} 35d
_1, the apparent outer diameter d ₀ = 1.08d ₁ ~1.5d ₁ become substantially rubber products for reinforcing steel cord, characterized by comprising a habit spiral small.