JP2837551B2 - Steel cord for reinforcing tire belt and method of manufacturing the same - Google Patents

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 a tire belt, and more particularly to a 2 + N-layer twisted structure (N = 6 to 8) which contributes to improving the shape of a cut piece of rubberized cord ( (Hereinafter simply referred to as a 2 + N structure) and a method of manufacturing the same.

[0002]

2. Description of the Related Art In a calendering process, a steel cord generally used for a belt of a pneumatic tire is aligned in parallel and then coated with a sheet of rubber to form a composite with rubber (hereinafter referred to as a treat material). Subsequently, in a cutting step, the treated material is cut obliquely with respect to the longitudinal direction of the cord at regular intervals to obtain a treated material as shown in FIG. Further, the side edges of the cut treated material are joined to each other, and FIG.
This is used as a belt belt reinforcing material for a tire belt. In this way, a treatment material for a tire belt is created.Because the steel cord used here is mainly twisted at the time of manufacture, cutting is performed by cutting between the filaments in the cord at the treatment edge corresponding to the cutting position. Is released, a force is generated to rotate the cord in the circumferential direction. And the twist imparted to the normally aligned steel cords is offset in one direction between the steel cords, and the treated material cut in the above cutting step is the force by which the cords themselves try to untwist or try to tighten. Since the forces collectively act outward in the radial direction, the ends of the treated material will spring up. The treating material having such a shape in which the end portion is raised has a problem that the bonding shown in FIG. 2 becomes impossible. Alternatively, when the bounce is relatively small, joining can be performed by manual correction. However, it takes time and effort to correct the correction, and there is a disadvantage that the cord driving at the bonding portion is disturbed, resulting in poor appearance and reduced tire belt durability.

Conventionally, 1 × 4 and 1 × 5 have been used for tire belts.
Steel cords with a single twist structure such as 2 + 6 or a layer twist structure such as 2 + 6 are used. However, when a large cord strength is required, 2 + 6 etc. having a gap between the filaments of the sheath with a layer twist and excellent rubber penetrating properties. Is generally used. Especially with a tubular stranded wire machine (tubular stranded wire machine), 2 + N layer laying,
The steel cord in which the core and the sheath have the same twist angle in the same direction has a remarkable problem that the treat material end portion jumps up due to the twist of the steel cord. In other words, the cord is in contact with the guide in the calendering process, that is, the cord of the layered structure is subjected to “ironing” by the guide in the calendering process, so that the filament of the sheath falls into the gap between the filaments of the core and the binding force in the cord is reduced. On the other hand, since the sheath filament moves along the core to generate a torsional force, the above-mentioned problem of the end of the treated material jumping up is remarkable. There is a particularly strong demand for suppressing the spring of the edge of the treated material.

[0004]

SUMMARY OF THE INVENTION Accordingly, the present invention proposes a steel cord having a novel structure, in particular, in a layer-twisted steel cord having a 2 + N structure, which can suppress the rise of the end after cutting a treating material using the cord. What you want to do.

[0005]

SUMMARY OF THE INVENTION The present invention provides a steel cord having a layered structure in which a sheath made of six to eight steel filaments is twisted in the same direction around a core made of two steel filaments. Then, in the section perpendicular to the axis of the steel cord, the arrangement in which one of the filaments of the core is sandwiched between the filaments of the sheath is defined as [300 / {twist pitch of sheath (mm)}] per 300 mm of cord length. ２2 × [300 / {twist pitch of core (mm)}] is a steel cord for reinforcing a tire belt.

In order to manufacture the above-mentioned steel cord, a core formed by twisting two steel filaments is continuously subjected to a corrugated bending process, and then 6 to 8 steel filaments are wound around the core. Twenty to eight steel filaments are twisted in the same direction as the core around the core, which is twisted in the same direction as the core, or two steel filaments are twisted, and then the steel cord is repeated. A manufacturing method in which bending deformation is applied to plastically deform is advantageously adapted.

FIG. 3 shows a cross section of a steel cord according to the present invention for the type of the twisted structure 2 + 6. In the figure, two filaments 1a and 1b showing the central axis
Constitute the core 2, and the six filaments 3 a to 3 f arranged around the core 2 constitute the sheath 4. The filament arrangement shown in the drawing, that is, the arrangement in which one of the cores 2, in the illustrated example, the steel filament 1 b is sandwiched between the filaments 3 a and 3 b of the sheath 4 is represented by a cord length.
For 300mm, [300 / {twisted pitch of sheath (mm)}]
２2 × [300 / {core twist pitch (mm)}].

[0008] The above-mentioned filament arrangement is advantageously realized by continuously applying a corrugated bending process to the core in advance, or by repeatedly applying a bending deformation to the steel cord to plastically deform the steel cord.

[0009]

The steel cord having the 2 + N structure has an asymmetrical arrangement with a gap between the filaments of the sheath disposed around the circumcircle of the core in a cross section orthogonal to the central axis. And, for example, in a stranded wire using a tubular type stranded wire machine, the core and the sheath are twisted after the regular helical shaping is performed on the filament in advance by the rivet plate, so that the sheath filament is on the core circumcircle. The core filaments are not arranged between the sheath filaments. In the cord having such a structure, it is impossible to sandwich the core filament between the sheath filaments.
Since the core and the sheath are restrained only by the contact between them, each filament cannot be restrained at the cord end of the cut portion of the treatment material, and the twist given to each filament is released and the cord jumps up. To develop. Above all, when the twist angles of the core and the sheath are similar, the number of contact points is reduced, and when subjected to “ironing” by the above-mentioned guide, the filament of the sheath easily falls into the gap between the filaments of the core. It is presumed that the phenomenon of the movement of the filament of the sheath due to “ironing” is likely to occur because of the decrease in the temperature.

[0010] Such a movement phenomenon between the core and the sheath causes the cord to be twisted. In particular, in a 2 + N structure twisted by a tubular type twisting machine, the core and the sheath are twisted in the same direction, and in particular, the twist angle. The problem of the bounce of the edge of the treated material to which a steel cord similar to the above is applied becomes remarkable.

[0011] As described above, the restoring force generated in the filament of the sheath that has been moved when it is subjected to "ironing" by the guide in the calendering process becomes a torsional force for rotating the cord, and the end of the treating material at the time of cutting. It is thought that it will lead to a splash. Therefore, in the present invention, the arrangement in which one of the filaments of the core is sandwiched between the filaments of the sheath is changed from [300 / {twist pitch of sheath (mm)}] to
By restricting the 2 × [300 / {twist pitch of core (mm)}] portion to the upper and lower limits, the splashing can be suppressed. That is, if the location of the above arrangement is less than the lower limit,
The movement of the sheath filament when receiving “ironing” cannot be sufficiently suppressed. On the other hand, if the upper limit is exceeded, the twist structure of the cord is significantly impaired, and the fatigue resistance required for the tire cord, especially buckling fatigue resistance, is reduced. descend.

[0012]

EXAMPLE Two steel filaments each having a diameter of 0.23 mm were drawn together using a tubular type stranding machine and spirally formed with a bracing plate, and then these two filaments were twisted at a pitch of 6.0 mm. The core 2 is twisted to form a core, and the core 2 is fed into a pair of corrugated rolls 5 each having a tooth profile shown in FIG. 4 to be corrugated. Then, a steel filament serving as a sheath is formed around the core. In the same direction as above, a steel cord A was prepared by twisting at a pitch of 12.0 mm, and a core was similarly prepared. Then, similarly, six filaments having a diameter of 0.23 mm were similarly molded using a tubular type twisting wire machine. 6 filaments wrapped around the core in the same direction as the core, pitch 12.0mm
A cord 6 having a layered structure formed by twisting with each other is shown in FIG.
The steel cords B were passed through straightening rollers 7a to 7c arranged in a zigzag pattern and disturbed the regular arrangement of filaments in the circumcircle of the core. For comparison, a steel cord C prepared in the same manner as the steel cord B and not passed through the straightening roller was also prepared.

The steel cord thus obtained is aligned to form a rubber composite by laminating a sheet-like rubber, and the rubber composite is applied to the cord in the longitudinal direction of the cord.
It was cut at an interval of 295 mm at an angle of ° to produce the treatment material shown in FIG. Next, the jump of the edge of the treatment material when the treatment material was naturally left on a horizontal plane was measured.
As for the steel cords A, B and C used for the treating material, as shown in FIG. 6, each cord was embedded in resin, and cross sections were observed at a core pitch interval along the 30 cm cord longitudinal direction. The number of locations where the core filaments were clamped (hereinafter referred to as the core constraint number) was investigated. The determination as to whether the filament of the core is sandwiched between the filaments of the sheath is made by determining the center of one of the filaments of the core outside the polygon formed by connecting the centers of the sheaths in the above-described cross-sectional observation. When the axis is located (see FIG. 7), it is determined that the core is sandwiched, and when both filaments of the core are located inside the polygon (see FIG. 8), it is sandwiched. It was determined that it was not.

Table 1 shows the results of the measurement of the amount of bounce of the edge of the treated material and the number of core constraints, together with the conditions of the corrugating pitch correcting roller for corrugating the core.

[0015]

[Table 1]

From the table, it can be seen that the steel cord A in which the filament of the core is restricted by the sheath by changing the cross-sectional shape of the core.
And B, compared to a similar unconstrained steel cord C,
It can be seen that the splash at the end of the treatment material is extremely small.

[0017]

According to the present invention, the torsion in the steel cord having the 2 + N structure can be greatly reduced, the jump of the edge of the treated material after cutting is reduced, and the joining of the treated materials can be easily performed. This is industrially useful because it is significantly improved and can prevent poor appearance during tire molding and a reduction in tire performance associated therewith.

[Brief description of the drawings]

FIG. 1 is a plan view of a treating material.

FIG. 2 is a plan view of a band-shaped bonded treating material.

FIG. 3 is a sectional view of a steel cord according to the present invention.

FIG. 4 is a schematic view of a corrugated roll used in the present invention.

FIG. 5 is a schematic view of a straightening roller used in the present invention.

FIG. 6 is a schematic diagram of a resin-embedded cord created for observing a cord cross section.

FIG. 7 is a cross-sectional view showing a state in which a filament of a core is sandwiched between filaments of a sheath.

FIG. 8 is a cross-sectional view showing a state in which a filament of a core is not sandwiched between filaments of a sheath.

[Explanation of symbols]

 1a filament 1b filament 2 core 3a filament 3b filament 3c filament 3d filament 3e filament 3f filament 4 sheath 5 corrugated roll 6 cord 7a straightening roller 7b straightening roller 7c straightening roller

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shinji Saito 800 Shimonakano, Kuroiso City, Tochigi Prefecture Bridgeton Bekaert Steel Code Co., Ltd. Tochigi Plant (56) References JP-A-61-82995 (JP, A (58) Fields investigated (Int. Cl. ⁶ , DB name) D07B 1/06 B60C 9/00

Claims (3)

(57) [Claims] 1. A steel cord having a layer-twisted structure in which a sheath made of 6 to 8 steel filaments is twisted around a core made of two steel filaments in the same direction. In an orthogonal cross section, one of the filaments of the core is placed between the filaments of the sheath.
per m [300 / {sheath twist pitch (mm)}] ~ 2
× [300 / {core twist pitch (mm)}] location, steel cord for tire belt reinforcement. 2. In producing the steel cord according to claim 1, a corrugated bending process is continuously applied to a core obtained by twisting two steel filaments, and then 6 to 8 cores are wound around the core. A method for producing a steel cord for reinforcing a tire belt, comprising twisting steel filaments in the same direction as a core. 3. The steel cord according to claim 1, wherein 6 to 8 steel filaments are twisted in the same direction as the core around the core formed by twisting two steel filaments. And then subjecting the steel cord to repeated bending deformation to plastically deform the steel cord, thereby producing a steel cord for reinforcing a tire belt.