JP2009114590A - Method for producing steel cord - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a steel cord by which an effect of bending is reduced and the shape disorder of the outermost ply filaments is suppressed, to provide the steel cord produced by the method for production, and to provide a pneumatic tire in which the steel cord as a reinforcement is applied when a three-ply twisted steel cord subjected to planar waveform preforming is produced. <P>SOLUTION: The method for producing the steel cord comprises twisting the three-ply twisted steel cord so as to provide a helical preforming ratio f (%) of the outermost ply filaments 3 within the range of ≥0.35×α+74.5 to ≤0.45×α+82.5 when the twist angle of the outermost ply filaments 3 is α(°), and then subjecting the resultant steel cord to the planar waveform preforming in the method for producing the three-ply twisted steel cord subjected to the planar waveform performing. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a method for manufacturing a steel cord, and more particularly, a steel cord that reduces the influence of bending and suppresses the disturbance of the shape of the outermost layer filament when manufacturing a three-layer twisted steel cord with plane wave shape molding. The manufacturing method of this, the steel cord manufactured by this manufacturing method, and the pneumatic tire which applied this steel cord as a reinforcing material.

  As a reinforcing material cord of a tire that is a typical example of a rubber article, the carcass cord forming the skeleton and the tire equatorial plane are extended at a small inclination angle, for example, 15 to 35 ° and arranged in parallel with each other. A belt cord is well known in which a plurality of plies in which a plurality of cords are covered with rubber are overlapped in an arrangement in which the cords cross each other between the plies.

  Also, heavy duty radial tires used at high internal pressure such as for trucks and buses and off-the-road use, especially flat tires, are not even rigid even with the belt of the above structure, so they are wavy or zigzag shaped in the tire width direction. A plurality of cords or filaments extending along the equator plane of the tire are used as reinforcing elements, and a plurality of layers of plies in which these reinforcing elements are covered with rubber are used instead of or in addition to the belt with the above-described inclined cords. It is proposed in Patent Document 1 to be used in the same manner.

  By using such a reinforcing element, it is possible to suppress the growth due to the internal pressure and the growth due to running without causing deformation of the crown part or cutting of the cord during expansion of the tire vulcanization molding.

Furthermore, as a means for manufacturing a cord or filament extending in a waveform or zigzag shape, for example, a method of forming a sinusoidal waveform on a wire using a pair of upper and lower gears (gears) described in Patent Document 2 is known. ing. In this molding process, a large bending input is applied to the surface of the cord through contact with the tooth mold, and as a result of plastic deformation, a plane wave shaped mold is obtained.
JP-A-2-81706 (Claims etc.) Japanese Patent Application Laid-Open No. 64-075227 (claims, etc.)

  When performing the above-mentioned type of gear meshing on a three-layer twisted steel cord subjected to plane wave shape molding, due to the stress of the gear biting, the contact portion with the tooth mold is affected by bending, There has been a problem that so-called cord cracking occurs in which the interval between the outermost layer (second sheath layer) filaments of the three-layer twisted cord is locally widened. The code is severely broken, and those that have been judged on the production line are now excluded from the line.

  Accordingly, an object of the present invention is to produce a steel cord that reduces the influence of bending and suppresses the disturbance of the shape of the outermost layer filament when producing a three-layer twisted steel cord that has been subjected to plane wave shape shaping. An object of the present invention is to provide a steel cord manufactured by the method and a pneumatic tire to which the steel cord is applied as a reinforcing material.

  The present inventor has earnestly investigated the cause of disturbance of the outermost layer when corrugated mold is applied to a three-layer twisted steel cord subjected to plane wave shape typing. In the three-layer twisted steel cord subjected to plane wave shape typing, By setting the helical mold rate of the outermost layer filament to an optimal range according to the twist angle in a state before the plane wave shape molding is performed, the twist property disorder of the outermost layer sheath of the plane waveform shaping unit is suppressed, The present inventors have found that the level of occurrence of code cracking can be reduced and have completed the present invention.

That is, the steel cord manufacturing method of the present invention is a method for manufacturing a three-layer twisted steel cord that has been subjected to plane wave shape molding.
When the twist angle of the outermost layer filament is α (°), the outermost layer filament has a spiraling rate f (%) of 0.35 × α + 74.5 or more and 0.45 × α + 82.5 or less. A three-layer twisted steel cord is twisted, and then the obtained steel cord is subjected to plane wave shape molding.

  The steel cord of the present invention is manufactured by the above manufacturing method.

  Furthermore, the pneumatic tire of the present invention is characterized in that the steel cord is applied as a reinforcing material. Preferably, the tire is for trucks and buses.

  According to the present invention, in manufacturing a three-layer twisted steel cord subjected to plane wave shape typing, it is possible to suppress the twist property disorder of the outermost layer sheath of the plane wave shape shaping portion and reduce the level of cord cracking. As a result, it is possible to provide a plane wave shape-molded steel cord with improved processing quality and reduced appearance defects on the production line. Furthermore, by using the obtained steel cord as a reinforcing material for the tire, it is possible to reduce the material processing cost included in the manufacturing cost of the tire.

The steel cord manufacturing method of the present invention will be described in detail with reference to the drawings.
As a preferred example of the three-layer stranded steel cord subjected to plane wave shape molding according to the present invention, a core 1 made of three steel filaments and a first steel wire made of nine steel filaments wound around the core 1 are used. In manufacturing a steel cord having a 3 + 9 + 15 twist structure having the sheath 2 and the second sheath 3 made of 15 steel filaments wound around the first sheath 2, first, the outermost layer of the second sheath 3 is manufactured. When the filament twist angle is α (°), the outermost layer filament spiraling rate f (%) is in the range of 0.35 × α + 74.5 or more and 0.45 × α + 82.5 or less. A three-layer twisted steel cord is obtained.

  In obtaining such a three-layer stranded steel cord, known molding devices and twisting machines can be used, and are not particularly limited. For example, in a steel cord having a 3 + 9 + 15 twist structure, the outermost layer filament of the second sheath 3 spirally formed is arranged around the first sheath 2 twisted around the core 1 to form a steel cord having a three-layer structure. To obtain, all 15 steel filaments installed in the twisting machine are passed through a molding device for spiral molding, and then the two-layer twisted cord and each strand are introduced to the twisting point (voice). And twist them together.

  Next, the obtained steel cord is meshed with a gear for shaping a plane wave shape to obtain a desired steel cord. In the steel cord thus obtained, the twisting disorder of the outermost layer sheath of the plane wave shape shaping portion is suppressed, and the level of occurrence of cord cracking is reduced. Thereby, improvement of processing quality can be aimed at.

The reason why the outermost filament filament spiraling rate f is defined within the above range is as follows.
That is, the present inventor first discovered that the forming rate of the outermost layer cord of the cord has an influence on the cracking, and further has an optimum value depending on the twist angle of the filament. Specifically, when the filament molding rate is large, the stress in the direction of spontaneous twisting is inherent, and cord cracking is likely to occur. Conversely, when the filament molding rate is small, the twisting stress is inherent. Therefore, it was found that the code cracking is suppressed. On the other hand, the filament in the stranded wire is restrained by being wound and works to stabilize the position. However, if the twist angle of the filament defined by the inclination angle from the cord longitudinal axis direction is small, the filament is restrained. Since the force is small, it is necessary to suppress the cord cracking with a small die-setting rate. Conversely, if the twist angle of the filament is large, the binding force of the filament increases, so even if the die-setting rate is slightly high, cord cracking suppression is possible. It was also found that the effect of. Based on this knowledge, as a result of setting the styling rate of the outermost layer sheath of the cord before being meshed with the plane wave shape tying gear in a region depending on the twist angle, the above tying rate range was found. If this molding rate is larger than the upper limit, the cracking level will increase, while if it is smaller than the lower limit, there will be no problem of cracking, but the wire breakage at the end where the cord is cut will become too large and work in the factory Sexuality becomes difficult.

  In the waveform patterning applied to the cord, the wavelength λ shown in FIG. 3 is preferably not less than the twist pitch of the second sheath and not more than 200 mm. If the wavelength λ is less than the twist pitch, the tension balance in the stranded wire is affected by bending. On the other hand, if it exceeds 200 mm, it is difficult to obtain elongation due to the corrugated shape. The amplitude 2a is preferably 1 to 10 mm. If the amplitude 2a is less than 1 mm, it is difficult to obtain elongation due to the corrugated shape. On the other hand, if it exceeds 10 mm, it is stretched by deformation of the tension load, and the lateral deformation of the cord when the corrugated shape disappears increases. . Furthermore, the filament diameter in the cord of the present invention is preferably in the range of 0.15 to 0.40 mm, and if it is smaller than this range, it becomes soft and difficult to corrugate. It becomes large and it becomes difficult to obtain elongation at low load when applied to a tire.

Hereinafter, the present invention will be specifically described based on examples.
A steel cord having a 3 + 9 + 15 structure (twisting direction is SSZ) shown in FIG. 1 was produced with a filament diameter of 0.23 mm and a cord diameter of 1.4 mm under the specifications shown in Tables 1 and 2 below. As shown in FIG. 2, the second sheath mold application rate f in the table is (D2 / D1) × 100, where D1 is the maximum diameter in a twisted cord state and D2 is the maximum amplitude when the filament is loosened. It is a value expressed in (%).

  Further, the average value of the maximum amount of cracks is the maximum value of the filament interval (in the bending inner portion of the cord vertical cross section in the trough portion of the cord shown in FIG. L) is an average value obtained by measuring N = 10 points in a continuous valley. The target value for plane wave shape typing is a value implemented at a wavelength λ = 32 (mm) and an amplitude 2a = 2.5 (mm).

Furthermore, in the example and the comparative example in the cord of the same twist structure, the plane wave shape molding process is performed on the cord having a different molding rate of the second sheath filament, the maximum crack amount is measured, and the average value is compared according to the following formula Expressed as an index.
Crack amount comparison index = cracking amount of example (mm) / cracking amount of comparative example (mm) × 100
A smaller crack amount comparison index means that the crack amount is reduced.

  Furthermore, as the evaluation of dispersibility, it was determined that the loosening of the end strands when each cord was cut with a cable cutter was good when it was not loosened or stopped at hand, and the case where the loosening was significant was judged as bad. The obtained results are shown in Tables 1 and 2 below.

  From the results shown in Table 1 and Table 2, it can be seen that in any cord twist structure, the amount of cracking is significantly reduced and the dispersibility is improved compared to the comparative example.

It is sectional drawing of the steel cord of the 3 + 9 + 15 structure in Examples 1-3 and Comparative Examples 1-3. It is explanatory drawing which shows a filament shaping | molding rate. It is explanatory drawing which shows the crack measurement part and crack amount of a plane wave shape shaping | molding cord.

Explanation of symbols

1 Core 2 First sheath 3 Second sheath

Claims (4)

In the method of manufacturing a three-layer stranded steel cord subjected to plane wave shape molding,
When the twist angle of the outermost layer filament is α (°), the outermost layer filament has a spiraling rate f (%) of 0.35 × α + 74.5 or more and 0.45 × α + 82.5 or less. A method of manufacturing a steel cord, comprising twisting a three-layer twisted steel cord and then subjecting the obtained steel cord to plane wave shape shaping.   A steel cord manufactured by the manufacturing method according to claim 1.   A pneumatic tire, wherein the steel cord according to claim 2 is applied as a reinforcing material.   The pneumatic tire according to claim 2, which is a tire for trucks and buses.

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