JPH1161662A - Steel cord for reinforcing rubber article and pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a steel cord for reinforcing rubber articles, capable of keeping good productivity, low cost and excellent workability and remarkably improving resistance to propagation of corrosion due to water content. SOLUTION: In double lay steel cord 1 comprising core strands 3 and outer sheath strands 6, the core 2 is composed of two strands having same structure, being mutually non-lay and parallel arranged in contact state and outer sheath strands 6 laid around the core strands 3 comprises 6-8 strands and at least either ones of the core strands 3 and the outer sheath strands 6 have rubber penetration structure and the outer sheath strands 6 have rubber penetration lay constitution to core strands 3 and form non-wrapping structure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a steel cord for reinforcing rubber articles (the former) and a pneumatic radial tire using the steel cord for reinforcing a tire belt as a rubber article (the latter). About steel cord which had high productivity and high quality,
The latter is low-cost and has excellent corrosion propagation resistance of the cord of the belt cord layer, so that the corrosion propagation of the steel cord from the cut is unlikely to occur, and it has excellent cut separation resistance, and there are many opportunities for off-road driving The present invention relates to a pneumatic radial tire, typically, for example, a tire for a construction vehicle.

[0002]

2. Description of the Related Art A conventional multi-twisted steel cord mainly occupies a structure of 1 (core, hereinafter the same) +6 (outer sheath, hereinafter the same) composed of one core strand and six outer sheath strands. . Moreover, in consideration of productivity, the circumscribed circular shapes of the cross sections of the respective strands are almost the same, and if some increase in cost must be recognized, the circumscribed circular shape of the core strand may be increased.

In all of these cases, the above 1 + 6
The structure has the following four disadvantages. One is that, as shown in the steel cord cross section in FIGS. 5 and 6, the curve C tangent to the outside of the cord cross section is almost circular, and in order to satisfy a predetermined tensile strength, a large number of parallelly arranged The thickness of the steel cord rubber covering member must be increased, which not only impairs the productivity of the steel cord reinforced rubber article and increases the cost, but also increases the gauge of the belt cord layer when the rubber article is a tire. Thicker,
This results in an increase in tire weight and deterioration of heat separation resistance.

Second, in order to increase the productivity of the steel cord, when the core strand 11 and the outer sheath strand 12 have the same strand 10 structure as shown in a steel cord cross-sectional view of FIG. Although the outer sheath strand 12 and the outer sheath strand 12 both have a bent rubber penetration structure, the core strand 1
1, the outer sheath strands 12 are twisted around each other, so that the outer sheath strands 12 come into contact with each other, and the unvulcanized rubber becomes the core strand 1 during vulcanization molding.
I can't get into 1 As a result, it is unsuitable to use this type of steel cord as a rubber reinforcing member that emphasizes corrosion propagation resistance due to moisture.

[0005] Here, the rubber penetration structure means that in each strand, there is a sufficient gap between the steel wires constituting the outer sheath, and the rubber is pressed under pressure applied to the inner surface of the tire during vulcanization molding of the tire. Refers to a structure in which rubber can easily penetrate easily into the inside of the strand and at least around each of the wires constituting the outer sheath and between these wires and the steel wires constituting the core. Therefore, in the steel cord having the cross section shown in FIG. 5, there is no room for rubber to enter into the black-filled portion of FIG. 7 in which the cross section is simply illustrated by at least the circumscribed circle of the strand, so that the rubber cannot reach the core strand 11. A void portion is formed, and the rubber penetration only stops at the outer side of the outer sheath strand 12 at the most, impairing the corrosion propagation resistance due to moisture.

Third, in order to improve the above-mentioned problem of rubber penetration, a steel cord having a cross-section shown in FIG. The core strand 15 is made larger than the diameter of the steel wire 13 of the outer sheath strand 16 so that the outer sheath strand 1
6 has a larger circumcircle than the outer circumscribed circle, whereby the rubber enters not only the inside of the outer sheath strand 16 but also the inside of the core strand 15, and the rubber can cover each steel strand.

However, the steel cords shown in FIG. 6 are spaced apart from each other because the circumscribed curves of the core strands 15 are circular during the calendering operation for covering the unvulcanized rubber from above and below to form a wide sheet. The twisted outer sheath strand 16 has a tendency to be biased as shown in FIG. 8 in which the cross-section is simply illustrated only by the circumscribed circle, as in FIG. 7, and as a result, the black portion in FIG. Is difficult to enter. As a result, especially core strand 15
A void portion is formed inside, and the corrosion propagation resistance due to moisture is impaired similarly to the steel cord shown in FIG.

The fourth problem is that, in the steel cord shown in FIG. 6, when the unvulcanized rubber-coated steel cord sheet is cut to a required size, the outer sheath strand 16 moves easily. As shown in FIG. 6, at least one outer winding wrapping wire is required as shown in FIG. It is unavoidable that the productivity of the steel cord is impaired and the cost is increased.

[0009]

Therefore, the invention described in claim 1 of the present invention advantageously eliminates the above-mentioned four disadvantages, and achieves good productivity, low cost and excellent workability. Another object of the present invention is to provide a steel cord for reinforcing a rubber article, which can greatly improve corrosion propagation resistance due to moisture as a reinforcing steel cord of the rubber article while holding the tire tread. Another object of the present invention is to provide a pneumatic tire provided with a belt having a rubber penetration property capable of preventing corrosion propagation resistance due to moisture against deep cut flaws.

[0010]

Means for Solving the Problems To achieve one of the above objects, the invention described in claim 1 of the present invention provides a core of a strand made of a plurality of steel strands and a plurality of cores around the core strand. In a double-stranded rubber cord for reinforcing a rubber article having an outer sheath formed by twisting a plurality of strands of steel strands, the core is a non-twisted parallel contact array of two strands having the same structure. Wherein the outer outer sheath strand twisted around the core strand is comprised in the range of 6 to 8, and at least one of the core strand and the outer outer sheath strand has a rubber penetration structure, and the outer outer sheath The strand is a rubber penetrator for the core strand. Down twisted has a configuration, a steel cord for reinforcement of rubber articles, characterized by comprising a non-wrapping structure.

The wires, strands, cores, outer sheaths and wrapping used in the above-mentioned steel cord are defined in accordance with “Definition of terms” described in the steel tire cord test method of JIS G 3510 (1992).
Elementary wire: solid wire that composes the cord, Strand: A small wire in which several strands are twisted, Core: Elementary wire or strand used as the core in the cord, Outer sheath: Elementary wire located on the surface of the cord or Strands and wrapping:
A wire wound spirally around a cord.

The rubber penetration structure is
As described above, there is a gap between the steel wires constituting the strand, and refers to a structure in which a part of the steel cord covering rubber enters around the wire under pressure during vulcanization molding from this gap, The non-wrapping structure refers to a structure that does not include a steel wire spirally wound around a steel cord.

In order to achieve one of the objects, the invention according to claim 2 of the present invention comprises a pair of beads, a pair of sidewalls, and a tread, and these parts are embedded in the beads. One or more ply of radially arranged cords to reinforce between the bead cores, preferably a carcass which becomes a rubber coating of a one ply radially arranged steel cord, and two or more cord crossing layers which strengthen the tread portion around the outer periphery of the carcass In the pneumatic tire provided with at least two belts close to the tread rubber
A pneumatic tire characterized in that the steel cord according to claim 1 is applied to a cord layer of the pneumatic tire.

This pneumatic tire is suitable for a pneumatic radial tire that is used for a general dump truck or a construction vehicle that travels on rough terrain that is easily damaged by cuts.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 and 2 are cross-sectional views taken along a plane perpendicular to the central axis of the steel cord. 1 and 2, the core 2 of the steel cord 1 is 2
As a matter of course, the strands 3 having the same structure of the books are arranged in parallel contact with each other and are in a non-twist state. The two strands 3 need to be mutually twisted and have a parallel contact arrangement. Here, "parallel" means that the central axes of the strands 3 are parallel to each other.

Therefore, at any position along the central axis of the cord, two tangent lines which are in contact with the circumscribed circles of the two strands 3 and are parallel to each other, and two arcs of a circumscribed circle extending outside these tangent lines , That is, the circumscribed composite line L of the core 2 maintains the position shown in the figure along the length direction of the steel cord.

The outer sheath 5 is formed by twisting six to eight strands 6 around the core 2 so as to be in contact with the circumscribed composite wire L of the core 2, and in the illustrated example, an outer sheath 5 is formed. I do. Unusual circumscribed composite line L of core 2
As a result, a curve E smoothly connected so as to enclose the seven circumscribed circles of the outer sheath 5 from the outside has an elliptical shape or an elliptical shape, and the steel cord 1 is always drawn at any position along its length direction. The direction of the elliptical or elliptical curve E shown in FIGS. In other words, the steel cord 1 has a flat shape in the same direction along its length, and this flat shape is never twisted.

The two parallel strands 3 forming the core 2 and the seven strands 6 forming the outer sheath 5
In the example shown in FIG. 1, the strand 3 of the core 2 has a rubber penetration structure, and the strand 6 of the outer sheath 5 has a normal structure. In the example shown in FIG. 2, both the strand 3 of the core 2 and the strand 6 of the outer sheath 5 have a rubber penetration structure.

The structure of the steel cord 1 shown in FIG. 1 is 2 × according to the display method of JIS G 3510 mentioned above.
(2 + 7 × D ₁ ) + 7 × (3 + 9 × D ₂ ), and in the illustrated example, the diameter D ₁ of the steel wire (hereinafter referred to as the wire) 7 of the core 2 is larger than the diameter D ₂ of the wire 8 of the outer sheath 5. large. The structure of the steel cord 1 shown in FIG. 2 is 2 × (2+
7 × D ₃ ) + 7 × (2 + 9 × D ₃ ), and the wire 9 of the core 2 and the wire 9 of the outer sheath 5 have the same diameter D ₃ .
Each of the steel cords 1 shown in FIGS. 1 and 2 has a non-wrapping structure having no wrapping (element wire).

The steel cord 1 having the above configuration has the following effects. (1) First, by making two strands 3 having the same structure in the core 2 of the steel cord 1 in a parallel arrangement and non-twist state, cord productivity can be improved and a low-cost steel cord can be obtained. Becomes possible. If three strands 3 having the same structure are used, the winding force of the outer sheath (the direction in which the force is applied is schematically shown in FIG. 3) as shown in FIG. 3), the core 2 as shown in the right-hand diagram shown at the tip of the thick arrow in FIG.
The rubber is crushed, and the rubber does not enter the central portion (the black portion) of the core 2, so that the bent rubber penetration structure cannot be effectively used.

(2) Next, when the strand 6 of the outer sheath 5 is twisted around the core 2, since the circumscribed composite wire L of the core 2 forms an oval L, a predetermined winding force on the core 2 is applied. 6 to 8 of the outer sheath 5
In the illustrated example, the seven strands 6 can be neatly twisted around the core 2 with a predetermined distance apart, and as a result, a rubber penetration structure can be realized at least for the core 2.

(3) Next, as shown in FIG. 4, the cross section of the steel cord 1 is schematically illustrated by a circumscribed circle of each strand.
A large number (only one is shown in the figure) of steel cords 1 are inserted in parallel at a predetermined number of inserts (the number per unit length measured in a direction perpendicular to the cords), and in a flat and horizontal and longitudinal direction. When the cord-shaped steel cords 1 aligned by applying a predetermined tension to the rolls are passed between calender rolls CR to coat (cure) the uncured rubber cg, the outer sheath 5 has an elliptical or elliptical curve E. The strand 6 is caught by the helical twisted wire anywhere in the core 2, the gap 6 is secured without moving the strand 6 of the outer sheath 5 even under the above-mentioned tension action, and the coated rubber cg is vulcanized. Sometimes, it can completely enter the core 2 in the direction of the arrow in the figure.

(4) Next, as shown in FIG. 4, the rubberized sheet of the finished steel cord 1 coated with the unvulcanized rubber CG is further twisted because the two strands 6 of the core 2 are not twisted. A thin gauge can be realized, thereby improving productivity and reducing costs. In addition, when the steel cord 1 is applied to a rubber article, for example, a cord layer of a tire belt, the belt is thinned. It is possible to reduce the cost and weight of the tire.

(5) Next, since the movement of the strand 6 of the outer sheath hardly occurs during the period from the production of the steel cord 1 to the vulcanization through the unvulcanized rubber coating,
Even when the sheet of the unvulcanized rubber-coated steel cord 1 is cut, or in the case of a finished tire after vulcanization molding, the cord hardly disperses, so that wrapping is not required. This also results in a considerable reduction in the production costs of the steel cord 1.

(6) Finally, in the case of a rubber article in which the corrosion propagation resistance of the steel cord 1 is extremely important based on the use and required characteristics of the rubber article to which the steel cord 1 is applied, as shown in FIG. In addition, a rubber penetration structure is applied to both the strand 3 of the core 2 and the strand 6 of the outer sheath 5 to obtain a complete rubber penetration multi-twisted steel cord 1, while the steel cord 1
When applying to a rubber article desirably imparting a certain degree of elongation to a steel cord, as shown in FIG. 1, a steel cord 1 in which a rubber penetration structure is applied only to a strand 3 of a core 2 is required. It has the advantage that it can be used properly according to the characteristics.

The two strands forming the core of the strand 3 of the core 2 shown in FIGS. 1 and 2 and the strand 6 of the outer sheath 5 shown in FIG. 2 have a twisted structure and a non-twisted parallel arrangement. Shall be included.

As the rubber article to which the steel cord 1 having the above-described specific structure is applied, a pneumatic radial tire having a large number of cut injuries on the tread portion of the tire, particularly a tire for a dump truck having a chance to run on a rough terrain or a rough terrain Construction vehicle tires that are exclusively used for traveling are suitable, and in this case, of course, the tires are applied to the steel cord layer of the belt.

The tire has a pair of bead portions, a pair of sidewall portions, and a tread portion, and each portion has at least one ply of radially arranged cords, preferably one ply, for reinforcing between the bead cores embedded in the bead portions.
A pneumatic tire having a carcass that becomes a rubber coating of a radially arranged steel cord of the ply and two or more cord cross layers that strengthen the tread portion at the outer periphery of the carcass, and a steel cord layer closer to the tread rubber of the belt, A steel cord layer disposed adjacent to this layer and having a cord arrangement intersecting the tire equatorial plane with the cord of the layer,
The steel cord 1 is applied to at least two layers.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A radial ply tire for construction vehicles having a size of 14.00R24, a carcass having a rubber coating of a one-ply radially arranged steel cord, and a belt having four steel cord cross layers arranged on the outer periphery of the carcass. Rubber coating. The belt is the first counting from the carcass side
In Examples 1 and 2, a steel cord 1 having a cross section shown in FIGS. 1 and 2 was applied to the second layer and the third layer in Examples 1 and 2 at a driving number of 7.2 / 5 cm.

Compared to Examples 1 and 2, Comparative Examples 1 and 2 in which a steel cord whose cross section is shown in FIGS.
And a conventional example in which steel cords whose cross sections are shown in FIG. 9 are applied to the second and third layers, and all other parts were produced according to the example. Table 1 summarizes the code structure and the like, including the application drawing of the steel cord.

[0031]

[Table 1]

The steel cords of the second and third layers were taken out from the tires of Examples 1 and 2, Comparative Examples 1 and 2, and Conventional Example.
After separating into a core strand and an outer sheath strand, all the outermost strands of each strand were removed, and the rubber coating length of the core was expressed in percent (%), which was defined as the rubber permeability. When the steel cord was cut, the length from the cutting end to the portion where the element wire was loosened and showed a diameter larger than the steel cord diameter before cutting was measured, and this was taken as the length (mm). This break length is 20m
A code that reaches m or more is called a loose code and is regarded as poor workability. The rubber penetration rate (%) is divided into the core strand and the outer sheath strand, and the separation length (m
m) are shown in the lower part of Table 1.

Table 1 shows that the steel cords 1 of Examples 1 and 2
In Example 1, the rubber penetration (penetration) of the strands of the core 2 is sufficient, and Example 1 is excellent in the corrosion propagation resistance of the core 2 and also has excellent elongation. It shows penetration properties and is excellent in corrosion propagation resistance, whereas Comparative Examples 1 and 2 have relatively good rubber permeability of the outer sheath strand, but the break length of the cut end of the cord is at a problem level, Further, the conventional example is not optimal for a tire for running on rough terrain because both the rubber permeability and the length of the rubber are inferior in corrosion propagation resistance due to moisture from the cut.

[0034]

According to the invention described in claim 1 of the present invention, while maintaining good productivity, low cost, and excellent workability, corrosion resistance due to moisture as a reinforcing steel cord of a rubber article due to moisture is maintained. A steel cord for reinforcing rubber articles can be provided, which can significantly improve the water content. According to the invention described in claim 2 of the present invention, it is possible to reduce the weight, A pneumatic tire excellent in cut separation resistance from corrosion can be provided.

[Brief description of the drawings]

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

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

FIG. 3 is an explanatory diagram illustrating an example of three core strands.

FIG. 4 is an explanatory diagram of a steel cord represented by a circumscribed circle when the embodiment of the present invention is covered with rubber.

FIG. 5 is a sectional view of a steel cord of a comparative example.

FIG. 6 is a sectional view of a steel cord of another comparative example.

FIG. 7 is an explanatory view showing a conventional steel cord strand as a circumscribed circle.

FIG. 8 is an explanatory view in which a strand of another conventional steel cord is represented by a circumscribed circle.

FIG. 9 is a sectional view of a conventional steel cord.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Steel cord 2 Core 3 Core strand 5 Outer sheath 6 Outer sheath strand 7, 8, 9 Element wire L Core circumscribed compound wire LE Curve in which the outer circumscribed circle of the outer sheath is in contact with it and smoothly connected S Wrapping

Claims (2)

[Claims] 1. A multi-twisted rubber having a core of a strand composed of a plurality of steel strands and an outer sheath formed by twisting a plurality of strands of a strand composed of a plurality of steel strands around the core strand. In the steel cord for reinforcing an article, the core is made of two strands having the same structure in a parallel contact arrangement and is non-twisted, and the outer sheath strand twisted around the core strand is made of 6 to 8 strands. At least one of the strand and the outer sheath strand has a rubber penetration structure, and the outer sheath strand has a rubber penetration twist structure with respect to the core strand, and has a non-wrapping structure, for reinforcing a rubber article. Steel cord. 2. A one-ply or more radial arrangement cord, preferably a one-ply radial, comprising a pair of beads, a pair of sidewalls, and a tread, and reinforcing these parts between bead cores embedded in the beads. A carcass that becomes a rubber coating of the array steel cord,
In a pneumatic tire having two or more cord cross layers for reinforcing a tread portion at an outer periphery of a carcass, the steel cord according to claim 1 is attached to at least two cord layers of a belt close to a tread rubber. A pneumatic tire characterized by being applied.