JPH07216767A - Steel cord for rubber reinforcement - Google Patents

Abstract

PURPOSE:To obtain a steel cord for rubber reinforcement, having an open multi- layer twisted structure and enabling uniform impregnation of rubber into each part in the cord. CONSTITUTION:This steel cord for rubber reinforcement is an open multi-layer steel cord having a (3+8+13) three-layer twisted structure. The forming ratio of the element wires of the intermediate layer and the outermost layer is 85-120% each and the diameter ratio of the element wires of the intermediate layer and the outermost layer to the element wire of the core strand is 1.015-1.030 each.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber-reinforcing steel cord which is embedded in a radial tire and used for reinforcement thereof.

[0002]

2. Description of the Related Art Steel cords are used by being embedded in rubber, that is, a plurality of steel cords are arranged in parallel between sheets of unvulcanized rubber, and the rubber is added in this state. It is vulcanized to form a composite of rubber and steel cord, and the composite is incorporated into a belt portion of a tire and used for reinforcement thereof.

A steel cord having a two-layer twist structure or a three-layer twist structure is generally used for reinforcing the radial tire. The two-layer twisted steel cord is generally a (3 + 9) structure, and the three-layer twisted steel cord is a (3 + 9 + 15) structure compact multi-layer twisted cord.

However, in this compact multi-layer twisted structure steel cord, the strands of the side layer are adjacent to each other so as to be in close contact with each other, so that the permeability of rubber into the cord is poor, and as a result, the cord There is a problem that moisture penetrates inside and corrosion fatigue occurs at an early stage.

Therefore, recently, by reducing the number of wires in the side layer portion and forming a gap between the wires,
A steel cord having an open multi-layer twist structure has been proposed in which the permeability of rubber is enhanced to prevent corrosion fatigue.

As an example of the open multi-layer twisted steel cord, in the double-layer twist, a (3 + 7) structure or (3 + 7) structure is used.
In the 8) structure and the three-layer twist, the (3 + 8 + 13) structure or the (4 + 9 + 15) structure is general.

[0007]

However, in the conventional open multi-layer twisted steel cord, the gaps between the strands of the side layer portion are uneven, and the gaps between the strands are partially excessive. A so-called mouth opening that becomes larger occurs, so that the rubber does not uniformly permeate inside the cord, and there is a part where the rubber does not permeate.As a result, the adhesion between the cord and rubber does not become constant, and the cord When the rubber sheet in which is embedded is expanded in the width direction, the intervals between the cords in the sheet become uneven, which causes a decrease in strength and the like.

The present invention has been made by paying attention to such a point, and an object thereof is an open multi-layer twisted rubber-reinforcing steel cord capable of uniformly permeating rubber into each portion inside the cord. To provide.

[0009]

In order to achieve such an object, the present invention is an open multi-layer steel cord having a two-layer or three-layer twist structure, in which a side wire portion has a wire forming ratio of 85. To 120%, and the ratio of the wire diameter of the outermost layer to the wire diameter of the core strand is 1.015 to 1.030.

[0010]

In the open multi-layer steel cord having such a structure, since the patterning rate of the wire in the side layer and the ratio of the wire diameter of the outermost layer to the wire diameter of the core strand are large, the wire of the side layer is A sufficient gap between the wires is generated without unevenness, so that the rubber uniformly penetrates the inside of the cord and the adhesion between the cord and the rubber becomes constant. Therefore, the rubber sheet with the cord embedded has its width The unevenness of the intervals between the cords when expanded in the direction is prevented.

[0011]

EXAMPLES An example of the present invention will be described below.
Fig. 1 shows a cross-sectional structure of a steel cord having an open multilayer twist structure. In this steel cord,
(3 + 8 + 13) three-layer twisted structure consisting of three strands δ0 constituting the core strand, eight strands δ1 of the intermediate layer constituting the side layer portion, and 13 strands δ2 of the outermost layer Is configured.

The diameter d of the strand δ0 of the core strand
0, the diameter d1 of the wire δ1 of the intermediate layer and the diameter d2 of the wire δ2 of the outermost layer, d2 / d0 = 1.015 to 1.030 d2 / d1 = 1.015 to 1.030. In this embodiment, the diameter d0 of the strand .delta.0 of the core strand is 0.175 mm.

The strands δ1 and δ2 of the intermediate layer and the outermost layer are each preliminarily spirally shaped before being twisted as a cord. The patterning rate K1 of the wire δ1 of the intermediate layer is K1 = {H1 / (D0 + 2d1)} × 100 (%), where H1 is the diameter of the spiral of the wire δ1 that is spirally shaped. The patterning rate K2 of the outer layer wire δ2 is
Let H2 be the diameter of the spiral of the wire δ2 that is spirally shaped.
Then, K2 = {H2 / (D0 + 2d1 + 2d2)}. Times.100 (%), but both of these molding ratios K1 and K2 are 85 to 120.
%, Preferably 85-100%, more preferably 93-100%
Set to.

In the conventional open multi-layer steel cord having the (3 + 8 + 13) structure, the strand δ0 of the core strand is
D0 of the intermediate layer, d1 of the wire δ1 of the intermediate layer and d2 of the wire δ2 of the outermost layer, d2 / d0 = 1.00 d2 / d1 = 1.00, and the patterning ratio K1 of the wire δ1 of the intermediate layer is The outermost layer strands δ2 both have a molding rate K2 of 60 to 80%.

Regarding the steel cord of the present invention and the conventional steel cord, when observing the state of the gap between the wires of the outermost layer, the conventional steel cord has a partial deviation in the gap, and it opens considerably wide. Where there are portions that do not exist and portions that do not, in the steel cord of the present invention, there is no bias in the gap, and the entire outermost layer wire is evenly distributed to maintain a stable shape. It could be confirmed.

When the conventional steel cord and the steel cord of the present invention were measured and compared with the rubber penetration, the results shown in the following table were obtained. In addition, the penetration degree of the rubber is such that the steel cords of the present invention and the conventional steel cords are alternately arranged in parallel between the rubber sheets having a thickness of 5 mm, and the rubber sheets are 50
It is vulcanized under a pressure of ~ 70kg / cm and a temperature of 160 ° C for 20 minutes. After this vulcanization, the wires of the outermost layer of steel cord are peeled off one by one from the sheet, and the wires of the inner layer Whether or not the rubber was attached to the portion in contact with was visually determined and evaluated by the number of strands to which the rubber was attached.

[0017]

[Table 1]

As can be seen from this table, in the conventional steel cord, the penetrability is 80%, and there is a portion where the rubber does not penetrate, but in the steel cord of the present invention, the penetrability is 100%, It can be seen that the rubber uniformly penetrates into the gaps inside the outermost layer and the intermediate layer.

For this reason, when a plurality of steel cords of the present invention are arranged in parallel in a rubber sheet and embedded in parallel,
The degree of adhesion between each cord and the rubber becomes constant. For this reason, when the rubber sheet is expanded in the width direction, the force applied to each cord becomes constant, so that the intervals between the cords do not become uneven, and the reduction in the strength of the cord can be prevented.

In addition to the case of the three-layer twist structure of (3 + 8 + 13), the present invention is an open multi-layer steel cord of the three-layer twist structure of (4 + 9 + 14), or the two-layer twist structure of the (3 + 7) structure or the (3 + 8) structure. It is also possible to apply to.

[0021]

As described above, according to the present invention, a sufficient gap is stably formed between the strands of the side layer portion, so that the rubber uniformly penetrates into the inside of the cord to form the cord. The effect of making the degree of adhesion with the rubber constant and preventing unevenness of the intervals between the cords when the rubber sheet in which the cords are embedded is expanded in the width direction and suppressing a decrease in strength Play.

[Brief description of drawings]

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

[Explanation of symbols]

 δ0… Core strand wire δ1… Intermediate layer wire δ2… Outermost layer wire

Claims (2)

[Claims] 1. An open multi-layer steel cord having a two-layer or three-layer twist structure, wherein the laying ratio of the wire in the side layer portion is 85 to 120%, and the outermost layer of the core strand with respect to the core strand diameter. Steel cord for rubber reinforcement, which has a wire diameter ratio of 1.015 to 1.030. 2. An open multi-layer steel cord having a three-layer twist structure of (3 + 8 + 13), in which both the intermediate and outermost strands have a stencil patterning ratio of 85 to 120% and the core strand diameter. Steel cord for rubber reinforcement, characterized in that the ratio of the wire diameters of the middle layer and the outermost layer is both 1.015 and 1.030.