JPH11200264A - Steel cord for reinforcing rubber article and pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cord more improved in durability by making mutual filaments in the outermost ply in a linear contact state in mutual adjacent strands of the whole strands constituting a cord of a multiple lay structure. SOLUTION: This cord is obtained by laying four strands 3A and 3B prepared by laying cores 1A and 1B formed of 1 to 3 steel filaments and at least one ply of sheaths 2A and 2B formed of a plurality of steel wires arranged around the cores 1A and 1B. The lay direction of the filaments constituting the outermost ply of the respective strands 3A and 3B are opposite between the adjacent strands 3A and 3B.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel cord used as a reinforcing material for rubber articles such as pneumatic tires and industrial belts, and more particularly, to twisting a plurality of strands of a plurality of steel filaments. An object of the present invention is to improve the durability of a cord having a multiple twist structure.

[0002] Tires well known as rubber articles reinforced with steel cords, especially so-called heavy duty tires for supporting heavy loads such as for trucks, buses and construction vehicles, have an opportunity to travel on rough terrain and rough terrain. When the tire rides on a large protrusion or rock etc. during this running, the part that hits the protrusion or rock etc. is locally deformed significantly, so the compression force is especially applied to the belt cord in the tire radial outside. In addition, a tensile force acts on the inner side and the inner side, and in many cases, the cord breaks due to a crack from the tensile side, and in many cases, the belt breaks to a tire failure.

[0003]

2. Description of the Related Art In heavy-duty tires, therefore, it is customary to use a high-strength and durable cord for reinforcing a belt so as to withstand use in a severe environment. The cord having high strength and durability often employs a multi-twist structure in which a plurality of strands in which a plurality of steel filaments are twisted are twisted.

For example, Japanese Patent Application Laid-Open No. 8-109585 discloses
A core consisting of ~ 3 steel filaments and at least one layer of sheath consisting of a number of steel filaments arranged around the core, twisted together, consisting of 1 ~ 3 steel filaments around the core strand A cord having a multi-twist structure in which six cores and at least one sheath made of a number of steel filaments arranged around the core are twisted and twisted by arranging six cores and twisting the core strands. By reversing the twisting directions of the sheath filaments forming the outermost layer of the sheath strand, the outermost sheath filaments between the core strand and the sheath strand come into line contact with each other to reduce stress concentration when a large load is applied. Relaxing to prevent filament breakage, It is draft.

[0005]

However, since the sheath filaments between adjacent sheath strands are in point contact with each other, stress may concentrate on the sheath filaments and impair the durability of the cord, leaving room for further improvement. was there.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a cord having improved durability by making the outermost filaments be in line contact with each other adjacent to all the strands constituting the cord having a multiple twist structure. It is in.

[0007]

SUMMARY OF THE INVENTION The present invention provides a strand of a strand comprising a core of one to three steel filaments and at least one sheath of a plurality of steel filaments arranged around the core. A cord formed by twisting four strands, wherein a twisting direction of a filament forming an outermost layer of each strand is reversed between adjacent strands, and a cord for reinforcing a rubber article and a plurality of steel filaments are provided. A cord for reinforcing rubber articles, wherein the twisted direction of filaments forming the outermost layer of each strand is reversed between adjacent strands, the cord being formed by twisting four twisted strands. .

The present invention is also a pneumatic tire having a carcass extending in a toroidal shape between a pair of bead portions as a skeleton, and a crown portion of the carcass reinforced with at least two layers of belts. A pneumatic tire obtained by applying any one of the above codes to at least one of the above.

[0009]

FIG. 1 shows a cross section of a steel cord applied to a carcass or a belt of a tire according to the present invention, with a twisted structure (1 + 6) × 4. The cord comprises a strand 3A and a 6 steel filament sheath around a single steel filament core 1B with a 6 steel filament sheath 2A twisted around a 1 steel filament core 1A. Strand 2B (indicated by diagonal lines)
Strand 3B twisted in the opposite direction to 3A sheath 2A
Are twisted under an arrangement in which two of each two are alternately arranged.

That is, in the four strands 3A and 3B constituting the cord, the twist direction of the filament forming the outermost layer, in the illustrated example, the filament of the sheath is
It is essential that the reversal be made between adjacent strands 3A and 3B. With this cord structure, the filaments between adjacent strands are in line contact with each other, and the point contact portion, which has been the starting point of stress concentration between the filaments, is eliminated, so that the durability of the cord can be improved.

The cord shown in FIG. 1 is an example in which the core of each strand is composed of one filament. However, a core formed by twisting or simply pulling a plurality of filaments is applied. Is also good. Furthermore, it is also possible to add a wavy shape to the filament of the core. Although the sheath is a single layer in FIG. 1, the sheath may be multi-layered. In this case, the twisting direction of the outermost sheath may be reversed between adjacent strands. And
When the strands are multilayered, it is preferable that the twisting direction of the sheath of the outermost layer of the strand is the same as that of the inner layer, so that the filaments in the strand are in linear contact with each other. However, from the viewpoint of the stability of the contact between the sheaths, a two-layer structure is more preferable than a three-layer structure.

Next, the cord shown in FIG.
In other words, a strand 4A in which four steel filaments are twisted and a strand 4B (indicated by oblique lines) in which four steel filaments are twisted in the opposite direction to the strand 4A are each two in each case. A total of four are twisted under an alternately arranged arrangement. This code also has the same structure as the code shown in FIG.
In the strands 4A and 4B of the book, since the twist direction of the filament is reversed between the adjacent strands 4A and 4B, the durability of the cord is improved.

Although the cord shown in FIG. 2 is an example in which each strand is composed of four filaments, the number of filaments in each strand does not need to be particularly limited, and can be increased or decreased as appropriate. Incidentally, it is preferable that each strand is composed of 2 to 4 filaments in that the twist shape of the strand is stable, local addition to each filament is relaxed, and the durability of the cord is improved.

Here, the code shown in FIG. 1 or 2 is
The ply formed by embedding a plurality of the wires in parallel with each other and embedding in a rubber sheet is applied to a carcass or / and a belt of the tire to reinforce the tire. The structure of the tire includes a conventional truck, A pneumatic tire for a bus or a construction vehicle may be used. For example, a truck or bus tire shown in FIG. 3 is advantageously used. In addition,
In the figure, reference numeral 5 denotes a bead core, 6 denotes a carcass wound around the bead core 5 from the inside to the outside of the tire, and 7 denotes a carcass.
And a belt 8 having a four-layer structure disposed on the carcass 6 and a tread disposed on the belt 7.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a carbon steel wire rod subjected to heat treatment and wire drawing to obtain a filament having a predetermined strength and diameter.
A cord having the structure shown in FIGS. 2 and 3 was manufactured under the specifications shown in Table 1. The strength of each of the cords thus obtained was measured, and a bending stress of 120 kgf / mm ² and a rotation speed of 3000 rpm were measured using a Hunter-type rotary bending fatigue tester.
The cord was repeatedly rotated and bent under the conditions of a temperature of 20 ° C. and a relative humidity of 60%, and the total number of rotations until the cord was broken was measured. Fatigue resistance was evaluated as an index. The larger the value, the better the fatigue resistance.

Further, each cord is applied to the tire belt shown in FIG.
We have prototyped 20 radial tires for trucks and buses.
And about the tire thus obtained, JIS D4230
According to "5.1 Tire strength (breaking energy) test", the plunger was pressed against each tire to measure the pushing force and the movement amount until the belt was broken, and the breaking energy was calculated. The tire strength was evaluated as a relative index when the index was set to 100. The larger the value is, the higher the strength of the tire is. Table 1 shows the results of the above measurements and evaluations.

[0017]

[Table 1]

[0018]

According to the present invention, the filaments can be in line contact with each other adjacent to all the strands constituting the multi-twisted cord, so that a cord having extremely excellent durability can be provided. obtain. By applying this cord to a tire carcass or belt, it is possible to provide a tire suitable for heavy-duty tires having improved durability especially in rough terrain.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a cord according to the present invention.

FIG. 2 is a sectional view showing a cord according to the present invention.

FIG. 3 is a sectional view showing a tire structure suitable for the present invention.

[Explanation of symbols]

 1A, 1B core 2A, 2B sheath 3A, 3B strand 4A, 4B strand 5 bead core 6 carcass 7 belt 8 tread

Claims (3)

[Claims] A cord formed by twisting four strands in which a core of one to three steel filaments and a sheath of at least one layer of a plurality of steel filaments arranged around the core are twisted. A cord for reinforcing a rubber article, wherein a twist direction of a filament forming an outermost layer of each strand is reversed between adjacent strands. 2. A cord formed by twisting a plurality of steel filaments and twisting four strands, wherein the twist direction of the filament forming the outermost layer of each strand is reversed between adjacent strands. A cord for reinforcing rubber articles. 3. A pneumatic tire in which a carcass extending in a toroidal shape between a pair of bead portions is used as a skeleton, and a crown portion of the carcass is reinforced with at least two layers of belts, wherein at least one of the carcass and the belts is provided. A pneumatic tire to which the cord according to claim 1 is applied.