JPH10292277A - Steel cord and tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a steel cord having a simple structure and sufficient rubber- permeating property and capable of carrying out sufficient twisting by one twisting step and inexpensive in production cost. SOLUTION: This steel cord comprises an open type steel cord having two- layer structure and obtained by arranging three core wires 1a in a core part 1, arranging eight or nine side wires 2a around the core part 1 and simultaneously loosely twisting these wires in same direction and same pitch. In the steel cord, the wires of the core part 1 have continuous wave habit smaller than a wave habit due to twisting in addition to the wave habit due to twisting and cross section of the cord has flat form in the longitudinal direction and the cord has each space between core wires and between side wires and between core wire and side wire.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-cost steel cord optimal for tire reinforcement and a long-life steel radial tire using the same.

[0002]

2. Description of the Related Art Conventionally, as a reinforcing member for a radial tire for trucks and buses, a steel cord having a two-layer twist or a multi-layer twist as shown in FIG. 1 or FIG. 2 has been used. These steel cords are required to have high strength and high durability as a reinforcing material, and also to have high corrosion resistance in a tire. In addition, simplification of the structure of the steel cord is required for cost reduction.

[0003] However, the conventional two-layer or three-layer steel cord has a two-stage twist in which the core A is tightly twisted and the side B is tightly twisted on the outer periphery thereof. In the latter case, the latter requires a total of three steps of tightly twisting the side C of the outermost layer, which has a disadvantage of increasing the manufacturing cost. Also, as shown in FIGS. 1 and 2, in these structures, the center of the core A is closed by three strands, so that the rubber is not It is hollow without penetrating to the center. Therefore, a small amount of water contained in the tire and water entering from scratches such as metal fragments and stones travel through the hollow portion in the still cord, thereby generating rust and shortening the life of the tire. Will be.

[0004] In order to solve this problem, the present applicant has
In JP-A-6-10281, a 1 × n structure in which eight or more strands are twisted in multiple layers, or a large number of side strands are twisted around a strand in which three strands are twisted. In the 1 × 3 + n structure, there has been proposed a structure in which a gap is intentionally provided between the strands of the core strand or between the strands of the side strand, and the cord section has a flat shape.

[0005] According to this prior art, since there is a gap between the strands of the core strand and between the strands of the side strand, rubber invades through the gap between the side strands during vulcanization after tire molding. The rubber also enters the inside from the gap between the strands of the core strand and is easily filled with rubber up to the center of the core strand. However, in this structure, a close examination reveals that many contact portions exist between the core strand strand and the side strand strand, and a tension is applied to the steel cord particularly during vulcanization after tire formation.
As shown in (a) and (b), the number of contact portions C increases, and this may cause a portion where rubber cannot penetrate into the inside of the cord. Therefore, it is still insufficient to obtain stable rubber permeability. Could not be said.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been made by research to solve the above-mentioned problems, and its object is to provide a simple structure and sufficiently stable rubber permeability. Another object of the present invention is to provide a steel cord which can be obtained by a single twisting process and has a low production cost. Another object of the present invention is to provide a tire having good corrosion resistance and a long life.

[0007]

In order to achieve the above-mentioned object, the present invention comprises three core strands arranged on a core, and 8 core strands around the core strand.
In an open-type two-layer steel cord in which up to nine strands are arranged and simultaneously loosely twisted in the same direction, the strands of the core are separated from the wavy by twisting. A configuration in which the cord has a small continuous wavy shape, and the cord has a flat cross section in the longitudinal direction, and further has gaps between the core strands, between the side strands, and between the core strands and the side strands. It is what it was.

The continuous wavy shape may be a spiral shape or a planar wave shape before twisting.
Further, a wave intermediate between the two may be used. In addition, although the diameters of the wires are basically the same, the wire may be configured by combining wires having different diameters in some cases.

[0009]

The present invention not only twists the core element wire 1a and the side element wire 2a loosely but also has a very small contact because the core element wire 1a has a continuous wavelet 100. Alternatively, most of the contact between the core element wire 1a and the side element wire 2a is non-contact. Therefore, even if tension is applied to the steel cord at the time of vulcanization of the rubber, the continuous small wave habit 100 causes the gap s.
And stable rubber permeability can be obtained. Moreover, since the entire cord has a flat cross-sectional shape, even if loosely twisted, the shape is stable, and even if tension is applied, the cord is unlikely to be untwisted, and the gap between the wires is hardly reduced. In addition, since it can be manufactured by twisting all the wires at once, only one process is needed.
Manufacturing costs can also be reduced.

[0010]

Embodiments of the present invention will be described below with reference to the accompanying drawings. 4 to 6 show an embodiment of a steel cord according to the present invention. 1 is a core part, 2 is a side part on the outer periphery of the core part 1, and the core part 1 is composed of three strands 1a. The side part 2 is composed of eight strands 2a. The three strands 1a and the side 2 forming the core 1
Are arranged as described above, and in this state, they are loosely twisted together in the same direction at the same time, thereby forming a 3 × 8 shape while being a bunched cord having a 1 × 11 structure. The gap s is formed between the strands 2a at the side portions by being loosely twisted. Further, the entire cord has a flat cross section perpendicular to the longitudinal direction.

More specifically, in the present invention, at least one, preferably two or more, of the three strands 1a constituting the core portion 1 are continuous, apart from the wavy formed by twisting. The one having the ripple habit 100 is used. As shown in FIG. 6, the continuous wavelet habit 100 has a predetermined range in which the pitch length p is smaller than the twisting pitch length P of the cord as typically shown in FIG. It has become. This predetermined range is set so that the wavy processing is not too tight and the fatigue resistance of the steel cord is not impaired, and that when the tension is applied to the steel cord, the wave is stretched and the gap forming function is not lost. It is set appropriately. In addition, continuous wavelet habit 1
The height h of 00 is a predetermined range smaller than the spiral wave height H of the core twist. The predetermined range is appropriately set so that the gap between the strands is sufficient to obtain rubber penetration, and the core 1 does not lose its shape and the uniformity of the cord does not deteriorate. The continuous wavelet habit 100 may be spiral in a state before twisting, may be planar unevenness, or may be intermediate between the two.

The wire 1a provided with the continuous wavelet habit 100 is twisted together with the other wires 1a. Therefore, also in the core part 1, the continuous wavelet
With 0, a gap s is reliably formed in the adjacent strand, and the rubber can be stably penetrated through the gap s to the inside of the cord without fail. Since the wire 2a at the side is loosely twisted, a gap s is formed between adjacent wires, and the wire 1a of the core 1 has a continuous wavelet habit 100. A gap s is also formed between the portion and the inner diameter side of the element wire 2a, through which rubber can penetrate inside. Unlike the present invention, when the core strand 1a and the side strand 2a are both tightly stranded cords, the core strand is tightly pressed into the side strand, so that the core strand has a continuous wave form. Although the effect of forming the gap due to the ripples is reduced even if the above method is performed, the problem is avoided in the present invention because the core strand 1a and the side strand 2a are loosely twisted as described above. Thus, the gap forming effect of the continuous wave habit 100 of the core element wire 1a can be sufficiently exhibited.

Further, as shown in FIG. 5, the steel cord has a flat sectional shape by being compressed in the vertical direction. The ratio of the short diameter D ₁ and the diameter D ₂ of the flat cross section (D ₁ / D ₂ oblateness) is generally 0.6 to 0.9 is suitable. In the present invention, in addition to the gap forming effect by loosely twisting the strands 1a and 2a, by forming the steel cord into a flat sectional shape, the side strands 2a are mainly forcibly separated from each other. In addition to the formation of s, the cord shape is stabilized, the twist of the cord does not easily return to the load in the longitudinal axis direction, and the contact between the wires can be reduced. In addition,
When the flatness ratio is low (when the flatness ratio approaches 0.9)
However, when the flattening rate is high (when the flattening rate approaches 0.6), the cross-sectional shape becomes one direction in the longitudinal direction. The present invention includes this case. In this case, there is an advantage that when the cords are aligned in parallel during tire production, the stability is good and the cover rubber thickness can be reduced.

FIG. 7 shows a second embodiment of the present invention.
In this embodiment, at least one, and preferably two or more (all three in this embodiment) three core strands 1a in which a continuous wave wave 100 smaller than the wave wave caused by twisting the cords is applied. And nine side strands 2a are arranged around the core portion 1 and are collectively twisted loosely in the same twisting direction and the same twisting pitch, and the whole is flattened in cross section. . The other configuration is the same as that of the first embodiment, and the description is omitted.

In any of the embodiments, the wires 1a, 2
In a, a surface of a high carbon steel wire is generally provided with a coating having good adhesion to rubber such as brass. In the embodiment, the strands 1a and 2a have the same diameter, but may be different in some cases.
That is, for example, the diameter of the wire 1a of the core 1 may be smaller or larger than the diameter of the wire 2a of the side portion 2, or one or two of the three wires 1a of the core 1 may be used. The diameter may be different from other wires. Alternatively, side 2
At least one of the strands 2a may have a diameter different from that of the other strands. However, in any case, the strands 1a, 2
The diameter of a is preferably selected from the range of 0.17 to 0.36 mm. If the diameter is less than 0.17 mm, the cord breaking load becomes too low. If the thickness exceeds the above range, the breaking load and the rigidity of the cord are too high, which is not appropriate.

Next, a method of manufacturing a steel cord according to the present invention will be described. Three strands 1a for the core and 8-9 for the side
A plurality of core strands 2a are prepared, and a continuous wave habit 100 is applied to a required number of three core strands 1a. That is, when the continuous wavelet habit 100 is helical, a wire twister in which about three rollers are arranged at intervals on a rotating body, and three to five pins on a base body immediately before (upstream side). Processing is performed using a staggered corrugating device, and the corrugating device is not used for the side strand 2a. The corrugating device does not rotate and is used as a fixed position. After passing through the corrugating device, the core wire 1a is wound around a roller at the entrance side of the wire twister and a central roller, and the wire twister passes through the wire in the same direction as the rotation direction of the bow of the main body of the double twist twisting machine. Revolve around the line. As a result, the core element wire 1a passes through the pins of the corrugating device, so that a spiral continuous wavelet habit 100 is formed. Thereafter, the wires 1a and 2a for each core and the side are passed through the pins of a downstream molding device in which 3 to 5 pins are staggered on the base in the same manner as the corrugating device. This molding device is also fixed in position without rotating, and each of the strands 1a and 2a passes through the pins of the molding device, so that the molding is appropriately performed larger than in the case of the compact cord.

In such a state, the three core strands 1a are located in the central region, and the side strands 2a are positioned so as to surround the core strands 1a. The wires are loosely twisted together. Since a bunched cord having a gap between the strands is obtained by such a process, the steel cord may be lightly compressed from the symmetrical position by 180 degrees with a pair of rollers or the like. In the case where the continuous wave habit 100 of the core element wire 1a is formed into a planar wave form, a pair of gears whose teeth are meshed with each other is used as a corrugating device, and the gear is moved in the same manner as described above. It is only necessary to place the wire in a path and pass a wire to be subjected to a continuous rippled wave between the pair of gears, whereby the wire is crimped in a zigzag manner by the meshing teeth.

FIG. 8 shows a radial tire to which a steel cord according to the present invention is applied, wherein 8 is a belt,
9 is a carcass. When the flatness of the steel cord according to the present invention is large, it is preferable that the long side of the belt 8 is arranged parallel to the tread surface and that the carcass 9 is arranged parallel to the center of the tire. Therefore, the thickness of the cover rubber can be reduced, which is effective in reducing the weight of the tire.

[0019]

According to the present invention described above, three core strands are arranged at the core, and eight to nine side strands are arranged around the core strand, and these are arranged at the same pitch in the same direction. At the same time, in the open-type two-layer steel cord loosely twisted, the strands of the core have a continuous wavy shape smaller than the wavy shape apart from the wavy shape due to twisting, and the cord has a longitudinal section. Has a flat shape, and furthermore, a gap between the core strands is formed by three synergistic effects of forming a gap by loose twisting, forming a gap by forming a flat cross section, and forming a gap by the continuous small wave habit 100 of the core strand 1a itself. Since there are gaps between the side strands and between the core strands and the side strands, the rubber can be surely permeated to the inner center of the two-layer cord. Nevertheless, since the cord is flattened, the wires are maintained in a stable shape, and the wires are difficult to approach each other even when tension is applied during rubber vulcanization. As a result, even when tension is applied, the continuous ripples 100 can reliably maintain an appropriate gap, and uniform and stable rubber permeability over the entire length of the cord can be obtained.
In addition, since the cord has a two-layer structure but has a single twist, an excellent effect that the manufacturing cost can be reduced can be obtained. According to claim 2, since the steel cord of the present invention is used for reinforcing a belt or carcass of a tire, it is excellent in corrosion resistance and can be a long-life tire, and the longer diameter side is parallel to the tread surface in the belt,
If the carcass is arranged in parallel toward the center of the tire, the thickness of the cover rubber can be reduced, so that an excellent effect that the weight of the tire can be reduced can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view of a conventional two-layer steel cord.

FIG. 2 is a sectional view of a conventional three-layer steel cord.

FIG. 3A is a cross-sectional view showing a conventional two-layer flat-structured steel cord under a tension load, and FIG. 3B is a cross-sectional view showing a state at another cross-sectional position.

FIG. 4 is a side view schematically showing a first embodiment of a steel cord according to the present invention.

FIG. 5 is a schematic sectional view of the first embodiment.

FIG. 6 is a side view schematically showing a core element wire obtained by disassembling a steel cord in the first embodiment.

FIG. 7 is a sectional view schematically showing a second embodiment of the steel cord according to the present invention.

FIG. 8 is a partially cutaway perspective view showing an example of a radial tire to which the present invention is applied.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Core part 1a Core strand 2 Side part 2a Side strand 100 Continuous wavelet s Gap

Claims (2)

[Claims] 1. An open type in which three core strands are arranged on a core portion and 8 to 9 side strands are arranged around the core strands, and these are simultaneously loosely twisted in the same direction at the same pitch. In the two-layer steel cord, the core wire has a continuous wavy shape smaller than the wavy shape apart from the wavy shape due to twisting, and the cord has a flat cross section in a longitudinal direction, A steel cord having gaps between the side strands, between the side strands, and between the core strand and the side strands. 2. A radial tire for an automobile, wherein the steel cord according to claim 1 is used for reinforcing at least a part of a belt or a carcass.