JPH0726397Y2 - Steel cord for reinforcing rubber products - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] 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.

[Conventional technology]

This type of steel cord is used as a reinforcing material for rubber products such as automobile tires and conveyor belts by covering a large number of them in parallel with each other and covering them with a rubber material.

As a steel cord for reinforcing a conventional rubber product, for example, a pneumatic radial tire for heavy load, as shown in FIG. 2, a core made of one wire (12) and six wires around the core. Steel cord (1) with a 1 + 6 + 12 twist structure having an intermediate layer formed by wire-twisting (13) in a wire-tight manner and an outer layer formed by wire-twisting 12 strands (14) around the intermediate layer in a wire-tight manner
It has been known.

[Problems to be solved by the device]

In the above steel cord, the wires (12) between the layers are
(13) or (13), (14) and adjacent strands (13), (13) or (14), (14) in the same layer are close or very close to each other.

Therefore, in the steel cord (11), when the rubber product is formed, the rubber material cannot penetrate into the inside between the strands, and it is impossible to form a complete composite body by simply covering the outer peripheral portion of the cord. It was Therefore, in the tire using the steel cord (11), since the adhesion between the cord and the rubber material is not sufficient, the cord and the rubber material are separated when the automobile is running, a so-called separate phenomenon occurs, Also, a part of the cord may be broken due to the fretting phenomenon caused by the contact between the adjacent strands, and a slight gap between the layers inside the cord may be a route for moisture in the rubber or moisture that has penetrated from the cuts in the tire. However, rust was generated on the entire steel cord, and the strength of the steel cord was greatly reduced.

The present invention has been made in view of the above-mentioned problems, and a gap for allowing a rubber material to enter is provided between the strands of each layer forming a cord and between the adjacent strands in the same layer so that the permeability of the rubber can be improved. It is an object of the present invention to provide a steel cord for reinforcing a rubber product which is a complete composite with a rubber material.

[Means for Solving the Problems]

In order to achieve the above object, the steel cord for reinforcing rubber products of the present invention is a steel cord having a structure of 1 + 6 + n made of strands of the same diameter, and each strand diameter is 0.15 to 0.30 mm.
When the number of the strands is n = 7 to 12 and the diameter of the strand is d, the peculiar pitch P ₁ = 4d
It has a substantially spiral habit of 35d and an apparent outer diameter d ₁ = 1.08d to 1.3d.

By the way, the above-mentioned various numerical limits are determined based on the results obtained from many experiments, and the outline thereof is as follows.

The wire diameter of each wire is set to 0.15 to 0.30 mm because if it 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.

Further, the number of strands n of the outer layer constituting the cord is set to 7 to 12 because when n is 6 or less, the shape of the cord becomes unstable and the strength of the cord is reduced, while n is 13 or more. This is because the gap between the adjacent strands becomes too narrow and the rubber material cannot penetrate into the cord.

If the gap is about 0.02 to 0.04 mm, the rubber material can sufficiently penetrate, so that n = 11 is most preferable.

Further, the spiral habit of the core wire has a habit pitch P ₁ of P ₁ = 4d to 35d and an apparent outer diameter d ₁ of d ₁ = 1.08d to 1.3d, where d is the wire diameter. Need to be satisfied. The reason for this is that if the habit pitch P ₁ is smaller than 4 times the diameter of the strand, it becomes difficult to squeeze the strand, resulting in reduced productivity.
On the other hand, if it is more than 35 times, the strands of the intermediate layer are twisted together along the spiral habit of the core strand, resulting in insufficient penetration of the rubber material, which is not preferable.

Further, if the apparent outer diameter d ₁ is smaller than 1.08 times the strand diameter, the gap between the adjacent strands in the intermediate layer does not allow rubber material to penetrate, and if it is larger than 1.3 times, the tensile stress Residual strain is generated when loaded, and the core wire projects into the intermediate layer, which shortens the fatigue life of the cord.

[Action]

When the steel cord configured as described above is sandwiched between two rubber sheets and pressure-vulcanized, the rubber material enters inside the cord from the minute gaps formed between the adjacent strands of each layer and the same layer. Once infiltrated, the steel cord is covered with a rubber material around each wire, forming a complete composite of the rubber material and the cord, and preventing the strength of the steel cord from being deteriorated due to fretting phenomenon, separation phenomenon and corrosion.

Further, since the core wire is provided with the spiral habit, it contributes to the improvement of the flexibility of the steel cord.

〔Example〕

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

In FIG. 1, (1) is a steel cord for reinforcing a rubber product, and the steel cord (1) has a core (5) consisting of a single strand (2) having a wire diameter d = 0.22 mm in the center thereof. Have.

The strand (2) is provided with a spiral habit with a habit pitch P ₁ = 3.5 mm and an apparent outer diameter d ₁ = 0.26 mm.
Around the core (5), six strands (3) having the same diameter as the strand (2) are twisted at a twist pitch S ₁ of 10.5 mm in the S twist direction to form an intermediate layer (6). ) Is formed.

Around the intermediate layer (6), 11 wires (4) having the same wire diameter as the wires (2) and (3) are twisted with a pitch S ₂ = 15.8 mm, Z
The outer side (7) is formed by twisting in the twisting direction to form the desired steel cord (1).

In the above-mentioned embodiment, the buncher type twisting machine is used to set the strand (2) of the core (5) before the gathering point of twisting with the six strands (3) forming the intermediate layer (6). It was carried out by passing only the above-mentioned strand (2) between 3 to 5 pins of the curling cone provided in the above.

By the way, in the above-mentioned strand (2), by adjusting the spacing, dimensions, etc. of the squeezing pins provided in a part of the twisting machine, and also of the gear which is provided in front of the twisting machine and which engages the strand. By adjusting the shape and the number of twists of the strands, it is possible to give a substantially spiral habit having a desired habit pitch and an apparent outer diameter.

Twisting pitch S ₁ of each wire (3) in the intermediate layer (6)
Is preferably in the range of 6-18 mm. The reason for this is that if the twist pitch S ₁ is less than 6 mm, the cord strength of the steel cord (1) becomes too low, while if it exceeds 18 mm, the fatigue resistance decreases. Also, the outer layer (7)
It is preferred that each strand (4) twist pitch S ₂ of longer than twist pitch S _1, and twist is within length plus 10mm to the pitch S ₁ in.

The reason is that if the twist pitch S ₂ is equal to or shorter than the twist pitch S ₁ , if the tensile stress is applied to the steel cord, the load on the intermediate layer (6) will be too large and the fracture will easily occur. This is because if the pitch S ₂ becomes longer than the length obtained by adding 10 mm to the twist pitch S ₁ , fatigue resistance decreases.

Furthermore, the twisting directions of the intermediate layer (6) and the outer layer (7) may be the same or opposite, but twisting in the opposite direction makes it easier for the rubber material to penetrate into the steel cord (1). preferable.

In addition, a steel wire having a carbon content of 0.70 to 0.90 wt% is usually used for the wire constituting the steel cord, but since the steel cord (1) has high strength and good toughness,
The carbon content of each wire (2), (3), (4) is 0.80 ~
More preferably, 0.85 wt% steel wire is used.

In addition, in order to improve the adhesion between the rubber material and the steel cord (1), the wires (2), (3) and (4) are plated with brass or bronze. Preferably.

Next, the steel cord of the present invention, together with the conventional example and the comparative example, were evaluated for breaking strength, rubber material infiltration rate, and compression tensile bending fatigue resistance as a composite with rubber, and the results are shown in the following table. In addition, all the wires constituting each cord used in the test had a carbon content of 0.82 wt%, and the surface thereof was brass-plated.

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

For the penetration rate of the rubber material, each cord was embedded in the rubber material under a tensile load of 5 kg, vulcanized, and then the cord was taken out.The cord was disassembled and a certain length of the core wire was observed. , The ratio of the length with the trace of contact with the rubber material to the observed length was expressed as a percentage.

The compression tensile bending fatigue property is obtained by embedding each cord in a plurality of rubber sheets and measuring the number of repetitions until the sheets are broken by fretting wear, buckling, etc. using a three-point pulley bending fatigue tester. Experiment No.1 code is 100
Is displayed as an index.

As is clear from the above table, the steel cord of the present invention is capable of satisfying all of breaking strength, rubber material penetration and fatigue resistance. For example, the steel cord of the present invention is used for a tire. In this case, the life of the tire and the riding comfort can be further improved.

[Effect of device]

Since the steel cord for reinforcing a rubber product of the present invention has the above-mentioned structure, the rubber material can surely penetrate into the cord. Moreover, the strength as a steel cord is sufficient, and the twist is stable.

For this reason, when it is used for a tire, for example, fretting wear, a separation phenomenon, and a decrease in cord strength due to corrosion are significantly reduced. Therefore, the life of the tire can be greatly extended, and riding comfort is also improved, which is an excellent effect.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a rubber product reinforcing steel cord of the present invention, and FIG. 2 is a sectional view of a conventional rubber product reinforcing steel cord. (1) …… Steel cord (2) (3) (4) …… Wire (5) …… Core (6) …… Intermediate layer (7) …… Outer layer

Claims (1)

[Scope of utility model registration request] 1. A steel cord for reinforcing a rubber product having a structure of 1 + 6 + n made of strands having the same diameter, each strand having a diameter of 0.
15 to 0.30 mm, the number of wires in the outer layer is n = 7 to 12, and the core wire has a peculiar pitch P ₁ = 4d when the wire diameter is d.
～35D, rubber products for reinforcing steel cord, characterized by comprising a habit of substantially spiral as the apparent outer diameter d ₁ = 1.08d~1.3d.