JP4628133B2 - Steel cord and manufacturing method thereof - Google Patents

Description

  The present invention relates to a steel cord and a manufacturing method thereof, and more particularly to a steel cord that can be suitably used for reinforcing various rubber articles such as pneumatic tires and industrial belts and a manufacturing method thereof.

  In pneumatic tires, which are typical examples of rubber articles, as a factor that reduces the durability of the tires, moisture that penetrates into the inner belt from the outside of the tire via cut flaws corrodes the belt cord, and this corroded area There is a known separation that occurs when the cord and rubber are peeled off due to the expansion of.

  In order to avoid the separation, a so-called rubber penetrating structure in which rubber is sufficiently infiltrated into the cord so that a gap for transmitting moisture between the filaments of the cord is not effective. This rubber penet structure realizes the penetration of rubber by increasing the gap between filaments by loosely twisting the cord, and is particularly suitable for a single twist cord having a 1 × 3 or 1 × 5 structure.

  On the other hand, in recent years, a steel cord having higher rigidity has been demanded in terms of performance such as riding comfort and handling stability of a pneumatic tire. On the other hand, it is possible to ensure the belt's tensile rigidity by increasing the number of cords driven in the belt of the tire, but this causes an increase in the weight of the tire and narrows the distance between adjacent cords in the belt. Therefore, there is a problem that rubber peeling starting from the cord end at the end portion in the belt width direction easily propagates between adjacent cords, so that so-called belt edge separation is easily caused.

Further, as a technique for realizing a steel cord having high rigidity, for example, in Patent Document 1, a tension load applied to the steel cord is applied almost evenly to the core and the sheath, and the strength possessed by the core and the sheath wire is disclosed. In order to exhibit it effectively, a steel cord having a 2 + 4 twist structure in which a spiral brazing process is applied to the core is described.
JP 2002-227081 A

  However, the steel cord described in Patent Document 1 is not provided with a core wire when a tension is applied to the cord at the time of tire manufacture because of corrugated spiral brazing applied to a bundle of two steel wires constituting the core. The gap between the sheath strands disappears and sufficient rubber permeability into the cord cannot be obtained, which may cause a problem that a separation phenomenon occurs (see FIG. 5).

  For such a problem, the applicant of the present invention is a steel cord for reinforcing rubber articles constituted by a core composed of two untwisted core strands and a sheath composed of three to five sheath strands. For the purpose of improving rubber penetrability, a technique has been proposed in which the inclination of the core wire viewed from the side of the cord is 3 ° or less with respect to the cord axis direction (Japanese Patent Application No. 2004-158772).

  However, in this case as well, since the core is spirally molded by twisting with the sheath strand, it is difficult to manufacture the core strand with an inclination of 3 ° or less with respect to the cord axis direction as viewed from the side of the cord. Met. Accordingly, there has been a demand for a technology capable of achieving both good rubber penetrability and high rigidity in the steel cord.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a steel cord that solves the above-described problems, has good rubber penetrability and high rigidity, and does not cause separation around the cord when applied to a rubber article, and a method for manufacturing the steel cord. There is.

  As a result of intensive studies, the present inventor has found that the above-described problem can be solved by adopting the following configuration, and has completed the present invention.

That is, the steel cord of the present invention includes a core formed by arranging a plurality of untwisted core strands in parallel in the longitudinal direction and a plurality of sheath strands twisted around the core. In the steel cord that is constituted by the sheath of the layer and the cord contour shape in a cross section perpendicular to the cord axis is flat,
The core is spiral-shaped with a smaller amplitude than the sheath wire, and the phase of the spiral of the core and the average phase of the spiral of the sheath wire are substantially the same in the longitudinal direction. It is what.

  In the steel cord of the present invention, it is preferable that the sheath strands are arranged unevenly without being uniformly distributed around the core.

Further, the steel cord manufacturing method of the present invention includes a core in which a plurality of untwisted core strands are arranged in parallel in the longitudinal direction and a plurality of sheath strands by a preformer. In the method of manufacturing a steel cord in which the sheath wire is twisted around the core after being molded,
The molding is performed such that a method of hanging the sheath wire on a pin on the preform and a method of hooking the core on the preform on the preform are opposite to each other. .

  In the manufacturing method of the present invention, it is preferable to use a straightness correcting jig after the mold by the preformer, and before the mold by the preformer, the core wire may be oiled. preferable.

  According to the steel cord of the present invention, with the above configuration, high rigidity can be ensured by the N untwisted + M structure, and the core can be formed by changing the size of the spiral forming to substantially match the phase. It was possible to improve the rubber permeability by ensuring the distance between the sheath strands by arranging the sheath strands. Such a steel cord of the present invention can be manufactured by the manufacturing method of the present invention. In particular, the inclination of the core wire viewed from the side of the cord, which has been difficult to manufacture, is 3 ° or less with respect to the cord axis direction. A certain steel cord can also be easily manufactured according to the manufacturing method of the present invention, whereby the rubber penetrability can be further improved.

Hereinafter, preferred embodiments of the present invention will be described in detail.
FIG. 1 (a) shows a schematic structure of a twisted structure as viewed from the side of a steel cord according to a preferred embodiment of the present invention. The illustrated steel cord 10 includes a core 1 in which two untwisted core strands are arranged in parallel in the longitudinal direction, and a single layer in which four sheath strands are twisted around the core 1. As shown in FIG. 1B, which is a cross-sectional view taken along the line AA in FIG. 1A, the cord contour shape in the cross section orthogonal to the cord axis is flat. is there.

  In the steel cord 10 of the present invention, the core 1 is spirally formed with a smaller amplitude than the sheath wire, and the spiral phase of the core 1 and the average phase of the spiral of the sheath wire are approximately in the longitudinal direction. Match. That is, the core 1 draws a spiral having an amplitude smaller than that of the sheath wire without causing any substantial deviation from the sheath wire. For this reason, as shown in the drawing, the core 1 is disposed inside the sheath 2 formed by the sheath strands, thereby widening the gaps between the sheath strands, and between the sheath strands. The distance is ensured and the permeability of rubber into the steel cord 10 can be improved.

  The steel cord of the present invention can be suitably used for reinforcing various rubber articles such as pneumatic tires, without causing a decrease in durability due to the occurrence of separation around the cord in the rubber article. It is possible to increase the tensile rigidity of the rubber article. Therefore, particularly when this cord is applied to a tire, it is possible to simultaneously satisfy the durability, riding comfort, and steering stability of the tire.

  In the steel cord of the present invention, by satisfying the above conditions, it is possible to simultaneously obtain high rigidity by the N untwisted + M structure and the effect of improving the rubber penetrability by the spiral forming. There are no particular restrictions on the diameter or the pitch of the helix. Also, the twisted structure is not particularly limited as long as it is an N untwisted + M structure, but can be suitably applied to, for example, a two untwisted core + three to five twisted sheath structure.

  Moreover, in the steel cord 10 of the present invention, as shown in FIG. 1B, it is preferable that the sheath strands are not uniformly distributed around the core 1 but are arranged unevenly. By adopting such an arrangement, the thickness in the vertical direction of the cord can be reduced. For example, when applied to a belt layer of a tire, the thickness can be reduced, so that the weight of the tire can be reduced. Further, it is possible to obtain the effect of improving the flexibility and the cord folding property against the buckling deformation of the belt generated outside the tread surface portion during cornering.

In addition, although not particularly limited, the tensile strength of the core strand and the sheath strand is preferably 2.9 kN / mm ² (300 kg / mm ² ) or more from the viewpoint of weight reduction. Furthermore, it is preferable that the diameters of the core wire and the sheath wire are in the range of 0.21 mm to 0.24 mm. If the diameter is less than 0.21 mm, it is difficult to ensure strength when applied to the belt. On the other hand, if it exceeds 0.24 mm, the bending rigidity in the out-of-plane direction of the belt becomes too large, and the steering stability is lowered. It is advantageous in terms of productivity that the core wire and the sheath wire have the same diameter.

  In manufacturing the steel cord of the present invention, the core of the sheath and the sheath wire before being molded by the preformer before twisting the sheath strand around the core, the sheath wire is applied to the pins on the preform. It is important that the way of hanging is opposite to the way of hanging on the pins on the core preformer. FIG. 2 (a) shows a side view and a front view of an example of a preformer 20 used in the case of a two untwisted core + four twisted sheath structure, and FIG. 2 (b) shows this preformer 20 according to the present invention. The development which shows the state which hung the core 1 and the sheath strand 2a-2d with respect to each is shown. For comparison, a developed view showing a state in which the core 1 and the sheath wires 2a to 2d are hung on the preformer 20 according to the conventional method is shown in FIG. As shown in the drawing, unlike the conventional method in which the sheath wires 2a to 2d and the method of hanging the core 1 on the pins 21 are all the same, the method of hanging the sheath wires 2a to 2d on the pins 21 and the pins of the core 1 are shown. By reversing the way to hang 21, as shown in FIG. 3A, the phase of the spiral forming of the core 1 is shifted by 180 ° from the sheath strand side, and the average spiral of the core spiral and the sheath strand is shifted. Are substantially the same in the longitudinal direction. Thereby, the core 1 is arrange | positioned in the sheath strand 2 in the twisting jig | tool 30 (refer FIG. 1), the distance between sheath strands is ensured, and it becomes possible to improve rubber penetrability. FIG. 3B is an explanatory diagram showing the phases of the core and the sheath wire after molding, corresponding to the conventional method of FIG.

However, since the twisting property expected when the core molding amount is excessively large cannot be obtained, the core processing amount in the preformer 20 is preferably 60% or less of the sheath processing amount. This processing amount F is expressed by the following formula:
F = xd (n−2) / (b × b)
(Where x is the biting amount, d is the wire diameter, n is the number of pins, and b is the pin distance (see FIG. 4)).

  According to the manufacturing method of the present invention, even when a helically shaped strand is used, the inclination of the core strand viewed from the side of the cord is 3 ° or less with respect to the cord axis direction, preferably substantially 0 °. It is possible to easily obtain a steel cord. By making the inclination of the core strand 3 ° or less, preferably substantially 0 °, the core strands are arranged side by side and substantially straight, thereby suppressing the cord elongation at the time of applying tension to the cord applied during tire manufacture, A closed space is not formed between the core and the sheath. As a result, the rubber easily infiltrates between the core wire and the sheath wire, so that moisture that has entered the inner belt from the outside of the tire via cut flaws corrodes the belt cord, and this corrosion It is possible to obtain an effect of avoiding separation in which separation occurs between the cord and the rubber due to the expansion of the area.

  Here, in order to obtain such a steel cord with high straightness, the core and the sheath wire formed after the forming by the preformer 20 are twisted together, and then the roll is arranged in a staggered shape and bent into a cord. It is preferable to correct using a straightness correcting jig that corrects the straightness of the cord by applying (not shown). Furthermore, it is also preferable that oiling is performed on the core wire prior to molding by the preformer 20, whereby the variation in tension at the time of stranded wire can be stabilized. The smoothness of the core wire changes depending on the surface condition, and if the tension at the time of twisting is set high, it is easily affected, and the tension balance is not uniform and the twisting property becomes unstable, but the oil on the surface By adhering, the slip property is stabilized regardless of the surface state of the strand, and the twist property is stabilized.

  In the production method of the present invention, it is important only to set the molding conditions by the preformer as described above, and the other production conditions are not particularly limited, and use a known apparatus or the like. Can be carried out according to conventional methods. As the stranded wire machine, for example, a tubular type stranded wire machine can be used.

Hereinafter, the present invention will be described in more detail with reference to examples.
A steel cord having a 2 + 4 twisted structure (core: 2 untwisted, sheath: 4 twisted (pitch 14 mm)) using a strand having a strand diameter of 0.225 mm is shown in FIG. 6 (Example) and FIG. Example) 6 and 7, (a) is a schematic diagram of the used tubular-type stranding machine 100, in which the strand S is drawn out from the bobbin 40, molded by the preform 20, and twisted by the twisting jig 30. The process is shown. (B) shows how the core 1 and the sheath wire 2 are hooked on the pins 21 of the preformer 20, and (c) shows the phase of the core 1 and the sheath wire 2 after molding. Furthermore, (d) is a cross-sectional structure diagram of the core 1 and the sheath wire 2 at the time of twisting indicated by arrows in (c).

Further, the processing amounts of the core and the sheath in the preformer 20 were set as shown in Table 1 below. As a result, in the example, the core was spiral-shaped with a smaller amplitude than that of the sheath wire, and the phase of the core spiral and the average phase of the sheath strand spiral were approximately the same in the longitudinal direction.
Tires were actually made using the steel cords obtained in the examples and comparative examples, and the rubber penetrability of each steel cord was evaluated. The results are also shown in Table 1 below.

(A) is the schematic seen from the side surface of the steel cord of one suitable example of this invention, (b) is sectional drawing in the AA cross section in (a). (A) is the side view and front view which show an example of a preformer, (b) is the expanded view which shows the state which hung the core and the sheath strand with respect to the preformer according to this invention, (c) FIG. 6 is a development view showing a state in which a core and a sheath wire are hung on a preformer according to a conventional method. (A) is explanatory drawing which shows the phase of the core and sheath strand after type | molding according to this invention, (b) is explanatory drawing which shows the phase of the core and sheath strand after type | molding according to a conventional method. It is explanatory drawing which concerns on the calculation method of the processing amount of the core in a preformer. (A) is the schematic seen from the side surface of the steel cord of one suitable example of this invention, (b) is sectional drawing in the BB cross section in (a). (A) is a schematic view of a tubular-type strand wire machine, (b) is a development view showing how to lay the core and sheath wire on the pins of the preformer, (c) is a core after molding and It is explanatory drawing which shows the phase of a sheath strand, (d) is a cross-section figure of the core at the time of the twist shown by the arrow in (c), and a sheath strand (Example). (A) is a schematic view of a tubular-type strand wire machine, (b) is a development view showing how to lay the core and sheath wire on the pins of the preformer, (c) is a core after molding and It is explanatory drawing which shows the phase of a sheath strand, (d) is a cross-section figure of the core at the time of the twist shown by the arrow in (c), and a sheath strand (comparative example).

Explanation of symbols

1 Core 2 (2a to 2d) Sheath (Sheath strand)
10 Steel cord 20 Preformer 21 Pin 30 Twisting jig 40 Bobbin 100 Tubular type stranding machine S Wire

Claims (5)

It is constituted by a core in which a plurality of untwisted core strands are arranged in parallel in the longitudinal direction, and a single layer sheath in which a plurality of sheath strands are twisted around the core. In the steel cord where the cord contour shape in the cross section orthogonal to the axis is flat,
The core is spiral-shaped with a smaller amplitude than the sheath wire, and the phase of the spiral of the core and the average phase of the spiral of the sheath wire are substantially the same in the longitudinal direction. Steel cord.   The steel cord according to claim 1, wherein the sheath wires are not uniformly distributed around the core but are arranged in a biased manner. After a plurality of untwisted core strands arranged in parallel in the longitudinal direction and a plurality of sheath strands are respectively molded by a preformer, the sheath strands are connected to the core. In the manufacturing method of steel cords twisted around,
Production of a steel cord, wherein the molding is performed so that a method of suspending the sheath wire on a pin on a preform and a method of suspending the core on a preform on the preform are reversed. Method.   The method of manufacturing a steel cord according to claim 3, wherein a straightness correcting jig is used after molding by the preformer.   5. The method of manufacturing a steel cord according to claim 3, wherein oiling is performed on the core strand prior to molding by the preformer.

Images