JP6203543B2 - Steel cord, rubber-steel cord composite and tire - Google Patents

Description

  The present invention relates to a steel cord suitable for reinforcing a tire, a rubber-steel cord composite using the steel cord, and a tire.

  The steel cord is used to reinforce a tire member. For example, a rubber-steel cord composite in which a plurality of steel cords are embedded in a sheet-like rubber in parallel with a gap as a tire belt is used.

  In recent years, there has been a demand for weight reduction of tires for the purpose of improving vehicle fuel efficiency. Accordingly, the rubber of the rubber-steel cord composite constituting the belt is made thin. As the rubber of this rubber-steel cord composite is made thinner, the outer shape of the cord in the cross section of the cord is similar to the cord structure in which the core has two steel filaments and the sheath has six steel filaments. The virtual outline is not a perfect circle, but a flat oval steel cord has been used (Patent Document 1). However, producing a steel cord by twisting a sheath filament around a core in which two or more filaments are arranged in a straight line has a risk that the arrangement of core filaments may be uneven depending on the process. In particular, when filaments having three or more cores are arranged in a straight line, the arrangement of the core filaments tends to be uneven when the sheath filament is wound around the core filament by a twisting machine. Although a twisting machine that does not disturb the arrangement of the three untwisted core filaments has been proposed (Patent Document 2), in order to produce a steel cord using this twisting machine, Significant modifications are required from the twisted wire machines used so far.

  It is also considered that the cross-sectional shape of the core filament constituting the core of the steel cord is elliptical or other flat shape. For example, Patent Document 3 describes an elliptical or triangular core filament, Patent Document 4 describes a substantially rectangular core filament, and Patent Documents 5 and 6 describe a flat core filament. However, processing the cross section of a single steel filament into an ellipse, triangle, or rectangle requires an excessive manufacturing cost and is not practical. Rolling a steel filament with a circular cross-section into a flat core filament is easier to process than an elliptical, triangular, or rectangular shape, but it is a high carbon used in tire cords. It is difficult to flatten steel at the same flattening ratio as a core with two filaments aligned.

JP 2000-8282 A Japanese Patent No. 4361638 Japanese Patent Laid-Open No. 7-197388 Japanese Patent Laid-Open No. 63-135584 JP 2004-58707 A JP 2000-355889 A

  An object of the present invention is to provide a stranded wire steel cord, a rubber-steel cord composite, and a tire having a flat cross section.

The steel cord of the present invention that solves the above-described problems is obtained by drawing a plurality of steel filaments through the die hole of a die having a deformed die hole, and using the filament after the wire drawing as a core. A steel cord manufactured by a method of manufacturing a steel cord in which a sheath filament is twisted around the core,
The plurality of filaments constituting the core are characterized by being untwisted.

  In the present invention, the term “unusual die hole” refers to a cross section in which a die used for wire drawing is usually perpendicular to the wire drawing direction when producing a steel filament used in a steel cord for tire reinforcement. Since it has a circular shape (substantially perfect circle) in (cross section), it means a die hole shape other than this true circle. That is, the “irregular shape” refers to a shape other than a true circle.

The odd-shaped die hole is preferably flat or substantially rectangular in the cross section of the die perpendicular to the wire drawing direction. Here, the “substantially rectangular shape” is not limited to the “rectangular shape” in the geometrical sense, and in the industrial manufacturing process of the filament, the length with accuracy obtained by wire drawing with a die and It is meant to include a rectangular shape with angular variation and rounded corners.
Moreover, it is particularly preferable to perform the step of twisting the sheath filament around the core using the filament after wire drawing as a core, using a tubular twisting machine.

  In the steel cord of the present invention, it is preferable that the contour shape of the steel cord is a flat shape or a substantially rectangular shape.

  Further, in the rubber-steel cord composite of the present invention, the above-described steel cord has a flat or substantially rectangular outline, and the short diameter direction in the outline of the steel cord is rubber in the sheet-like rubber. It is embedded so as to be aligned in the thickness direction, and is particularly suitable for use in a belt member of a tire. Moreover, the tire of this invention is provided with the rubber-steel cord structure mentioned above.

  According to this invention, since a plurality of steel filaments are drawn through the die hole of a die having a deformed die hole as a core, a plurality of steel filaments are obtained by this wire drawing. Adhere to each other by plastic deformation. Therefore, a stranded wire steel cord having a flat shape can be easily obtained by making the irregularly shaped die hole into a flat shape or a substantially rectangular shape.

3 is a flowchart of an example of a steel cord manufacturing method according to the present invention. It is sectional drawing which shows the die hole of the unusual shape of dice | dies. It is a schematic diagram of a tubular stranded wire machine. It is sectional drawing of an example of the steel cord of this invention. It is typical sectional drawing of an example of the rubber-steel cord composite of this invention.

  Hereinafter, a steel cord manufacturing method, a steel cord, a rubber-steel cord composite, and a tire according to the present invention will be specifically described with reference to the drawings.

  In the steel cord manufacturing method of the present invention, as shown in the flow chart of the steel cord manufacturing process in FIG. 1, a plurality of steel filaments are prepared (step S1), and these steel filaments are formed with irregularly shaped die holes. The wire drawing is performed through the die hole of the die to be held (step S2). Using the filament subjected to the wire drawing as a core, stranded wire processing is performed by winding a plurality of sheath filament filaments around the core by a twisting machine (step S3) to obtain a steel cord (step S4).

  The steel filament to be prepared is plated on the surface, specifically, brass-plated in order to improve the corrosion resistance of the steel filament and improve the adhesion to rubber, and is substantially circular in cross section. . The filament diameter can be approximately the same as the normal filament diameter used for steel cord cores. About the manufacturing method of the plated steel filament which has such a diameter, what is necessary is just to follow the manufacturing method of a normal steel filament. For example, on a high carbon steel wire, after performing dry wire drawing with annealing as necessary, after performing a patenting treatment, pickling and plating treatment, and then performing wet wire drawing as described above. A steel filament having a predetermined diameter plated is obtained.

  2, the shape of the die holes of the dies 1 to 4 may be the equilateral triangle shown in FIG. 2A, but preferably, as shown in FIG. b) a flat shape as shown in FIG. 1, specifically, an elliptical shape formed by crushing a circle in the diametrical direction and connecting two parallel segments with curved lines that project outward from both ends, in other words, A track shape is preferable for obtaining a flat steel cord. Moreover, it can also be set as a rectangle (FIG.2 (c)) and another ellipse (FIG.2 (d)), and all can obtain a flat steel cord.

  The size of the die hole can be set to a size that provides an appropriate area reduction with respect to the steel filament relative to the size when a plurality of steel filaments to be drawn are combined. As a result, a plurality of steel filaments are drawn with a die hole. Specifically, it is preferable that the area reduction rate at the time of drawing once in the drawing process is 3 to 25%. This is because if the area reduction ratio exceeds 25%, there is a possibility that filament breakage and ductility decrease due to the influence of heat generation and drawing tension at the time of wire drawing, whereas if it is less than 3%, plastic deformation is not sufficient. . Further, after the wire drawing, the steel filaments are brought into close contact with each other to be integrated into a plate shape, so that a surface reduction rate of 5% or more is required. Therefore, a more preferable condition for the surface reduction rate is 5 to 15%. It is.

  The number of steel filaments that pass through one die hole is equal to or less than the number of core filaments in the steel cord to be manufactured. For example, two cores are two, and three cores are three. It is.

  In wire drawing, oil or a water-soluble lubricant is added to one or both of the die and the filament before the die in consideration of suppression of heat generation due to wire drawing processing, ensuring lubrication performance of wire drawing work and reduction of ductility due to heat generation. It is preferable to take measures for supplying to both or immersing the entire die and filament in a lubricant and then wiping.

  It is also possible to prepare a plurality of dies having the above-mentioned irregularly shaped die holes with different sizes of the die holes, and perform wire drawing a plurality of times for a plurality of steel filaments using these dies.

  By drawing a plurality of filaments with the above-mentioned irregularly shaped die, the filaments that become the core of the steel cord can be arranged in a flat shape or the like in a non-twisted state at once, and the filaments in this arranged state Can be led to a twisting machine. Therefore, a flat core can be obtained easily. In addition, because the steel filaments are plastically deformed by wire drawing and are in close contact with the adjacent steel filaments, the core filaments are not aligned in the stranded wire using a stranded wire machine that is used in the subsequent process. Can be prevented. In addition, the steel cord can increase the rigidity of the core. The ability to increase the rigidity of the core allows further flattening of the steel cord. Further, since the core filaments are in close contact with each other, the corrosion resistance of the core filaments can be improved. Being able to improve the corrosion resistance of the filament of the core eases restrictions on the method of twisting the sheath filament and the cord structure of the sheath in consideration of rubber penetration.

  The filament that has been drawn can be once wound on one spool. When twisting with a twisting machine, a plurality of filaments that have been drawn are unwound at a time from one wound spool and supplied to the twisting machine. A plurality of sheath filaments are wound around a filament serving as a core by this twisting machine to obtain a flat steel cord. This twister is preferably a tubular twister.

  Generally, a buncher twisting machine or a tubular twisting machine is used as a twisting machine for manufacturing a steel cord for a tire. Of these twisting machines, it is preferable to use a tubular twisting machine. The tubular stranding machine 5 shown as an example in FIG. 3 includes a rotating barrel 6, a core filament spool 7 supplied in the barrel 6, and a sheath filament spool 8 provided in the barrel 6; A twisting die 9 for twisting the core filament and the sheath filament is provided.

  In general, a buncher twisting machine essentially twists the core itself due to its structure. Therefore, using a buncher twisting machine, even if a plurality of sheath filaments are wound and twisted around the core filament after the wire drawing process described above to produce a flat steel cord, this flat steel cord is According to the twist of the core filament, the direction of the minor axis direction in the cross section changes around the core center in the longitudinal direction of the steel cord. Such a steel cord cannot sufficiently guarantee the thinning of the rubber-steel cord composite.

  On the other hand, in the tubular stranded wire machine, the core is essentially not twisted. Therefore, using a tubular twisting machine, the flat steel cord obtained by winding and twisting a plurality of sheath filaments around the core filament after the drawing process described above has a short diameter in cross section. The direction of the direction is constant in the longitudinal direction of the steel cord. Therefore, the steel cord can be embedded in the rubber so that the minor axis direction thereof is aligned with the thickness direction of the sheet-like rubber, and the rubber-steel cord composite can be reliably reduced in thickness.

  The plurality of steel filaments subjected to the above-described wire drawing are unwound from one spool and supplied to a tubular stranded wire machine. In the conventional twisting method using a buncher twisting machine, the number of spools around which the steel filament for the core is wound is prepared, and one steel filament is unwound from each spool to obtain a tube. It was supplied to the stranded wire machine. Compared with this conventional stranded wire method, it is advantageous in productivity and cost that a plurality of core steel filaments are unwound from one spool as described above.

  By using a plurality of steel filaments that have been subjected to wire drawing as described above for the core, even when there are a plurality of core steel filaments, the arrangement of the core filaments becomes uneven in the middle of the stranded wire. Can be prevented. Therefore, a steel cord with stable quality can be manufactured.

  As shown in FIGS. 4A and 4B, preferred examples of the steel cord obtained by the manufacturing method described above are as follows. FIG. 4A shows a 2 + 8 cord structure, and FIG. 4B shows a 3 + 10 cord. Each has a structure. These steel cords 10 and 20 are formed by winding a plurality (m pieces) of sheath filaments 12 and 22 around a plurality (n pieces) of core filaments 11 and 21 constituting a core as a sheath, and twisting them together. It is a steel cord having a so-called n + m cord structure and a flat cross section. However, the steel cord of the present invention is not limited to the cord structure shown in FIG. 4, and may be another flat steel cord having a cord structure such as 3 + 9, and a steel cord having an elliptical outline. You can also The cores of the steel cords 10 and 20 are untwisted cores that are not twisted.

  The steel cords 10 and 20 shown in FIGS. 4 (a) and 4 (b) are formed so that each of the core filaments 11 and 21 is plastically deformed by the wire drawing using the die having the above-mentioned irregularly shaped die holes. It is in close contact. In addition, it can be said that the plating formed on the surface of the steel filament before plastic deformation exists in the adhesion interface of the cores of the steel cords 10 and 20.

  In the steel cords 10 and 20 in the example shown in FIG. 4, the core filaments 11 and 21 constituting the core are plastically deformed and brought into close contact with the adjacent steel filaments. The rigidity of the core can be increased compared to the case where the core filaments 11 and 21 are arranged in parallel without twisting, and the corrosion resistance of the core filaments 11 and 21 can be improved. Further, the steel cords 10 and 20 have a flat shape or a substantially rectangular outline, and contribute to the thinning of the rubber-steel cord composite using the steel cords 10 and 20.

  As shown in FIG. 5, a schematic cross-sectional view of an example of the rubber-steel cord composite 30, the rubber-steel cord composite 30 includes a plurality of steel cords 10 at predetermined intervals in a rubber sheet 31. The steel cord 10 has a short diameter direction aligned with a thickness direction of the rubber sheet 31. Since the steel cord 10 is embedded in the rubber sheet 31 in such a direction, the rubber-steel cord composite 30 can be thinned. Such a rubber-steel cord composite 30 is suitable for use as a tire belt member.

  In the tire using the rubber-steel cord composite 30 as a belt member of the tire, the thickness of the belt layer can be reduced, and the weight of the tire can be reduced.

  Steel cords having 2 + 8 and 3 + 10 cord structures shown in Table 1 were produced. When manufacturing the steel cord, the core filament was drawn through a flat die. In the comparative example, the core filament was not drawn through the flat die. In these examples and comparative examples, a plurality of filaments were wound around a core filament by using a tubular stranded wire machine and twisted together.

Table 1 also shows the production cost when these steel cords are manufactured with a length of 1000 m, and the number of locations where the core filaments intersect, which is an indicator of the irregularity of the core filaments.
From Table 1, each example had a lower production cost than the comparative example, and there was no crossing of the core filaments.

1, 2, 3, 4 Dies 5 Tubular stranding machine 6 Barrel 7 Spool 8 Spool 9 Twisting dies 10, 20 Steel cord 11, 21 Core filament 12, 22 Sheath filament 30 Rubber-steel cord composite 31 Sheet rubber

Claims (5)

A steel cord of a steel cord in which a plurality of steel filaments are drawn through a die hole having a deformed die hole, and the sheath filament is twisted around the core using the drawn filament as a core. A steel cord manufactured by a manufacturing method ,
A steel cord characterized in that a plurality of filaments constituting the core are non-twisted. Contour of the steel cord, steel cord according to claim 1, wherein a flat shape or a substantially rectangular shape. A rubber-steel cord composite in which the steel cord according to claim 1 or 2 is embedded in a sheet-like rubber so that the minor axis direction in the contour of the steel cord is aligned with the thickness direction of the rubber. The rubber-steel cord composite according to claim 3, which is used for a belt member of a tire. A tire comprising the rubber-steel cord composite according to claim 3 or 4 .

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