JP2007332489A - Steel cord for reinforcing rubber article and tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new structure for suppressing the occurrence of twist disorder such as protrusion of core wires from gaps between sheath wires or the sheath wires in excess of the core wires in a steel cord in which the sheath composed by winding a plurality of wires around the core composed of a plurality of paralleled wires without twisting is arranged. <P>SOLUTION: The average preforming ratio of the core is regulated within the range of 15-70% and the average preforming ratio of the sheath is regulated within the range of 70-95% in the cord in which the sheath composed by winding the plurality of preformed wires around the core composed of the plurality of paralleled and preformed wires without twisting is arranged. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a steel cord for reinforcing rubber articles, in particular, a steel cord without twisting disturbance and a tire to which the steel cord is applied. The steel cord serves to reinforce rubber articles such as tires, hoses or conveyor belts.

  There are various types of steel cords used to reinforce rubber articles, but a tire, which is a typical example of rubber articles, has a sheath in which a plurality of strands are wound around a core composed of a plurality of strands. A steel cord having a so-called layer twist structure is frequently used.

In recent years, two or three strands that make up the core are arranged straight without twisting, and are molded around this core, with the aim of reducing the cost of the cord itself and improving tire performance by improving tensile rigidity, etc. A cord having a sheath around which several strands having been subjected to wrapping are wound has been developed (see Patent Document 1). In such a cord, if the number of strands constituting the sheath is too large, the gap between the sheath strands will be reduced, and rubber penetration from the sheath to the core will be reduced, impairing cut separation resistance in the tire. Therefore, 3 to 6 are appropriate.
Japanese Unexamined Patent Publication No. 9-15314

  Here, in the cord having the structure shown in FIGS. 1A and 1B, the cord axis direction in the case where the sheath 2 made of four strands is arranged around the core 1 made of two strands. As shown in FIG. 2, the cord is twisted through a large gap S between the strands of the sheath 2 so that the strands of the sheath 2 are evenly distributed on the circumference of the core 1. It is a feature that the wire group of the sheath 2 is wound together as a group. That is, the core has a structure characterized in that it is always exposed through the large gap S between the sheath wires in the cord axis direction. Accordingly, the rubber can be reliably guided between the core strands via the large gap S between the sheath strands, and a cord structure excellent in rubber penetration can be obtained.

  However, the steel cord having the above structure has a large gap between the sheath strands, and the number of sheath strands is small to surround the core. It becomes more susceptible to strands.

  When a cord having such a structure is twisted using a tubular stranding machine in particular, as shown in Fig. 2 (a), the strand 10 of the core 1 protrudes from the large gap of the sheath 2, or conversely As shown in (b), twisting disturbance such as the remaining strand 20 of the sheath 2 remaining with respect to the strand 10 of the core 1 occurs.

  If such a twisted cord is applied to tire production, it will be forced to occur when it is combined with a rubber sheet in the calendar process of the tire factory, resulting in a decrease in tire durability. Is a problem.

  Accordingly, the present invention provides a steel cord in which a sheath formed by wrapping a plurality of strands around a core made of a plurality of strands aligned without twisting is provided, wherein the core strand is a sheath strand. The object of the present invention is to provide a novel structure for suppressing the occurrence of twisting turbulence that protrudes from the gap or leaves the sheath wire remaining with respect to the core wire.

  Now, in order to manufacture a cord having the above structure with a tubular stranding machine, as shown in FIG. 3, for example, two strands 10 to be the core are passed straight through the center of the preform device 3, and then the core For example, four strands 20 that form a sheath molded by the preform device 3 are arranged around the strand 10, and the sheath strand 20 is placed around the core strand 10 by the voice 4 together with the core strand 10. After winding, the product is prepared by adjusting the twist properties with the straightening roll 5.

  In the above manufacturing process, in the steel cord immediately after the core wire 10 and the sheath wire 20 are twisted together by the voice 4, the core wire 10 often protrudes greatly from the gap between the sheath wires 20, The protrusion is usually adjusted by a straightening roll 5 and finally adjusted to a twisted property so that the core wire 10 does not protrude.

  However, under mass production on an industrial scale, the cord may not always be sufficiently corrected with the straightening roll due to failure of the straightening roll or variations in how the wire surface slides against the straightening roll. Even after passing through the correction roll, it was difficult to suppress the occurrence of twisting disturbance.

  In view of such circumstances, it is important to suppress the twisting of the cord on the entering side of the straightening roll, and as a result of earnest investigation of the means for that purpose, appropriate shaping is also applied to the strands constituting the core. As a result, it has been found that it is effective to balance the molding amounts of the core strand and the sheath strand, and the present invention has been completed.

That is, the gist of the present invention is as follows.
(1) A steel cord in which a sheath formed by winding a plurality of typed strands around a core obtained by arranging a plurality of typed strands without twisting the core is provided. A steel cord for reinforcing rubber articles, characterized in that the average forming rate of the wires constituting the sheath is 15 to 70%, and the average shaping rate of the strands constituting the sheath is 70 to 95%.

(2) The steel for reinforcing rubber articles according to the above (1), wherein the core is composed of 2 or more and 3 or less strands, and the sheath is composed of 3 or more and 6 or less strands. code.

(3) A tire having a carcass extending in a toroidal shape between a pair of bead portions and having at least one belt on the outer side in the tire radial direction of the carcass, wherein the belt has the above (1) or (2 ) Tires made by applying the steel cord described in the above.

  According to the present invention, as a result of arranging a sheath formed by wrapping a plurality of strands around a core made of a plurality of strands aligned without twisting, the sheath strands are evenly distributed around the core. In the steel cord with a structure in which the sheath strands are wound together as a group without being dispersed in the core, the core strands protrude from the gap between the sheath strands, or the sheath is against the core strands. It is possible to provide a structure capable of reliably suppressing twisting disturbance in which the strands remain. Therefore, when the cord of the present invention is applied to a tire, the cord is driven uniformly in the tire, and as a result, a tire having excellent durability can be provided.

  The steel cord of the present invention has a structure in which a sheath formed by wrapping a plurality of strands around a core of a plurality of strands aligned without twisting is arranged in the same manner as the cord shown in FIG. In the cord having such a basic structure, the core wire that has been conventionally applied to the sheath wire is further applied to the core wire, and the sheath wire and the core are configured. It is characterized in that the type of the wire to be adjusted is adjusted to a predetermined range.

That is, the average typing rate defined by the following formula (1) is used as a typing index.
Average molding rate = (average molding amount / cord diameter) · 100 ---- (1)

  Here, the average shaping amount in the above formula (1) means that when the cord that has been straightened by the straightening roll is loosened to the strands of the core and the sheath, t shown in FIG. Measure the typed amount t in each strand and mean the average of its maximum and minimum values.

The cord diameter can be calculated according to the following formula (2) when the number of core wires is two and according to the following formula (3) when the number of core wires is three. In the following formula (2), the coefficient when calculating the diameter of the core composed of two strands was set to 1.5.If the two strands serving as the core are arranged side by side, the outline of the core is This is because it becomes an ellipse, and the average of the major axis and minor axis in the ellipse is the core diameter.
When there are two core wires: Cord diameter = (1.5 · dc + 2.0 · ds) ---- (2)
When there are three core wires: Cord diameter = {2.0 · (dc + ds)} ---- (3)
However, dc: Core wire diameter (mm)
ds: sheath wire diameter (mm)

  And when winding the sheath wire around the core, in order to suppress the twisting turbulence where the core wire protrudes from the gap between the sheath strands, or the sheath wire remains in the core strand It is important that the average mold forming rate of the strands constituting the core is 15 to 70% and the average mold rate of the strands constituting the sheath is 70 to 95%.

  That is, when the average forming rate of the strands constituting the core is less than 15%, when the sheath strand is wound around the core, as shown in FIG. Since the strands are left over, the tension balance of the strands becomes uneven and the cord strength is reduced.

  On the other hand, when the average forming rate of the strands constituting the core exceeds 70%, when the sheath strand is wound around the core strand, the core strand is left in the sheath strand. That is, as previously shown in FIG. 2 (a), the core strand protrudes from the large gap between the sheath strands, the balance of strength of the strands becomes uneven, and the cord strength decreases.

  In addition, if the average forming rate of the strands constituting the sheath is less than 70%, in the calender process at the tire factory, a cord is made after manufacturing a treat material of a predetermined length by pressing rubber on the peripheral surface of the cord. When cutting and guiding the cord to the crimping process with rubber through the guide during the manufacture of the next treat material, the cord end after cutting will be scattered, causing trouble when passing the cord through the guide etc. The performance is significantly reduced.

  On the other hand, when the average forming rate of the strands constituting the sheath exceeds 95%, when the sheath strands are wound around the core strands, as shown in FIG. On the other hand, the sheath strands are left in excess, and the contact force between the core strands and the sheath strands is weakened, so that the tension load balance of the strands becomes uneven and the cord strength decreases.

  Therefore, by adjusting the cords that have been straightened by the straightening rolls, the average forming rate of the strands constituting the core is adjusted to 15 to 70%, and the average shaping rate of the strands constituting the sheath is adjusted to a range of 70 to 95%. In addition, it is possible to suppress the twisting disturbance in which the core strands protrude from between the sheath strands, or the sheath strands remain, and to obtain a property having no problem in workability and tire performance in a tire factory. More preferably, the average forming rate of the strands constituting the core is 20 to 40%, and the average typing rate of the strands constituting the sheath is 75 to 90%.

  Here, in order to mold the core strand in addition to the sheath strand, in the conventional process shown in FIG. 5 (a), as shown in FIG. 5 (b), the sheath strand 20 is guided. This can be easily achieved by newly introducing the core wire 10 to the home device 3.

  In the steel cord for reinforcing rubber articles of the present invention, the number of strands constituting the core is preferably 2 or more and 3 or less, and the number of strands constituting the sheath is preferably 3 or more and 6 or less.

  That is, the number of strands constituting the core is set to 2 or more and 3 or less. If the number of strands constituting the core is one, the strength of the cord may be insufficient. Further, when the number of strands constituting the core is more than 3, the cord diameter becomes too large, and there is a concern about belt edge separation.

The reason why the number of strands constituting the sheath is 3 or more and 6 or less is that if the number of strands constituting the sheath is 2 or less, the strength of the cord may be insufficient. Further, when the number of sheath strands is more than 6, the gap between the sheath strands becomes narrow, and there is a concern that the rubber penetration may be reduced when rubber is intruded into the cord.

  The above steel cord is used to reinforce a carcass by applying a ply formed by arranging a plurality of steel cords parallel to each other at a predetermined interval and embedded in a rubber sheet, to a tire belt. As the structure, it may be in accordance with a conventional tire. For example, the tire structure shown in FIG. In the figure, reference numeral 30 is a bead core, 31 is a carcass wound around the bead core 30 from the inside to the outside of the tire, 32 is a belt having at least a two-layer structure disposed on the carcass 31, and 33 is a crown of the carcass 31. It is a tread arranged in the section.

  Similar to the cord shown in FIG. 1, various structures shown in Table 1 are based on a structure in which a sheath formed by winding a plurality of strands around a core made of a plurality of strands aligned without twisting is arranged. A steel cord having the following specifications was produced.

  The various steel cords thus obtained were examined for twisting of the cord after the straightening roll 5. In other words, the twisting of the cord after the straightening roll is as shown in Fig. 7 in which a cord with a diameter of 15 cm is made, and the cord is twisted when the cord is squeezed and the loop is made with a diameter of 3 cm while squeezing the cord. The condition was investigated. The results are also shown in Table 1.

  In addition, in order to investigate the variation of the cord terminal, about the twisted cord, cut the part 1m or more away from the terminal with pliers, and the part where one strand is loosened from the cut surface is 5cm The above cases were considered to be scattered, and if the part was less than 5 cm, it was considered not to be scattered. The results are also shown in Table 1.

  In addition, Table 1 also shows the results of the investigation of the code strength index as an evaluation of the characteristics of the code. The cord strength index is the index when the tensile strength of each cord is measured with a tensile tester and the tensile strength of Comparative Example 3 is taken as 100 for these measured values.

It is a figure which shows the basic structure of the steel cord of this invention. It is a figure which shows twist twist of a cord. It is a figure which shows the manufacturing process of a code | cord | chord. It is a figure which shows the amount of shaping | molding. It is a figure which shows the typing method of a cord strand. It is sectional drawing which shows a tire structure suitable for applying the cord of this invention. It is a figure which shows the investigation procedure of the twist disorder of a cord.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Core 2 Sheath 3 Preform apparatus 4 Voice 5 Straightening roll 10 Core strand 20 Sheath strand 30 Bead core 31 Carcass 32 Belt 33 Tread
s large gap
t Molding amount

Claims (3)

  A steel cord in which a sheath formed by wrapping a plurality of typed strands around a core obtained by arranging a plurality of typed strands without twisting is arranged, and constitutes the core A steel cord for reinforcing rubber articles, characterized in that an average forming rate of the strands is 15 to 70% and an average forming rate of the strands constituting the sheath is 70 to 95%.   2. The steel cord for reinforcing rubber articles according to claim 1, wherein the core is composed of 2 or more and 3 or less strands, and the sheath is composed of 3 or more and 6 or less strands. A steel cord having a carcass extending in a toroidal shape between a pair of bead portions, and having at least one belt on the outer side in the tire radial direction of the carcass, wherein the steel cord is on the belt. Applying a tire.

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