JP4688355B2 - Steel cord for tire reinforcement and tire - Google Patents

Description

【００２４】
下記表２は、〔解決手段２〕による発明の実施例についての試験結果を示すものである。なお、これは上記〔解決手段２〕において効果がでにくいと考えられる１X１２構造、３＋９構造についてのものである。
【表２】

表１、表２から明らかなように、本発明のコードは伸び率においてすべて合格であり、撚り崩れも波形くせ不良もなかった。
また、他の鋼種および略平面状の波形くせにおいても同様の効果が得られることも確認した。
【００２５】
【発明の効果】
本発明のコードは、上記構成であるため、適度な伸び特性および強度を有し、タイヤ製造時の加硫処理におけるタイヤの膨張に追従してコード環が増径するので、所望のベルト部近傍に止めおくことができ、しかも、タイヤ成型後には伸び特性が小さいので、高速連続回転によるタイヤの径方向への膨張を抑止できる。従って本発明のコードをトラックやバスの重荷重用タイヤに使用した場合、タイヤの保形性を高め、寿命を著しく向上させることができる。
【図面の簡単な説明】
【図１】（ａ）は、本発明の実施形態を示すコードの概略平面図及び矢印方向の断面図である。（ｂ）は、本発明の他の実施形態を示すコードの概略平面図及び矢印方向の断面図である。
【図２】従来のタイヤの構造を示す概略断面斜視図である。
【図３】ベルト部近傍を工業繊維にて補強した従来の別のタイヤの構造例を示す概略断面斜視図である、
【符号の説明】
１、１０・・・コ−ド
２０・・・ベルト部補強コ−ド（ベルトコ−ド）
３０・・・カ−カス部補強コ−ド（カ−カスコ−ド）
Ａ・・・タイヤ補強コ−ド
Ｐ・・・くせ付けピッチ
ｐ・・・撚りピッチ
Ｄ・・・見掛けの外径，波高
ｄ・・・コ−ド径[0001]
[Industrial application fields]
The present invention relates to a tire-reinforcing steel cord used as a reinforcing material for automobile tires, particularly heavy-duty tires such as trucks and buses, and a tire using the same.
[0002]
[Prior art]
To reinforce tires, so-called tire cords are used, in which a plurality of fine wires made of industrial fibers such as nylon, polyester, aramid fibers or steel are combined.
[0003]
As shown in FIG. 2, the portion reinforced by the tire cord is a carcass portion in which carcass portion reinforcing cords (carcass cords) 30 are arranged in a radial pattern while supporting the side wall from the center of the tire circle. The belt portion reinforcing cord (belt cord) 20 is a belt portion arranged like a “rib” in the circumferential direction of the tire. In passenger car tires, steel cords are used for the belt part, and industrial fiber cords are used for the carcass part. In heavy duty tires for trucks and buses, steel cords are used for both the belt part and the carcass part. Is common.
[0004]
By the way, in addition to the reinforcement of the belt portion and the carcass portion, as shown in FIG. 3, the tire reinforcement cord A is wound around the circumference of the belt portion in the vicinity of the both side edges of the belt portion, and is wound a plurality of times. Tires are being developed. The tire reinforcing cord A is different from a cord arranged at an angle with respect to the tire rotation direction, such as a belt portion reinforcing cord (belt cord) 20 and a carcass portion reinforcing cord (carcass cord) 30. It is called a zero degree belt cord because it is wound along the rotational direction, and it suppresses the tire from expanding in the radial direction due to heat generated by friction between the road surface and the tire during traveling or centrifugal force due to high-speed rotation of the tire. It is arranged for this purpose. For this tire reinforcing cord A, an industrial fiber cord is used.
[0005]
However, in recent years, due to the rapid increase in truck transportation and long-distance buses due to the widespread use of highways, the high-speed driving time of trucks and buses has increased rapidly, and the friction with the road surface due to the high-speed rotation of tires accompanying high-speed driving As the amount of heat generated by the resistance and the radial centrifugal force applied to the tire increased, the bulge force in the radial direction of the tire increased. On the other hand, since the industrial fiber cord currently used has low strength, it cannot sufficiently cope with this swelling force.
[0006]
[Problems to be solved by the invention]
In order to cope with the above problem, it is conceivable to use a steel cord for the zero degree belt cord instead of the industrial fiber cord. Steel cords are much stronger than industrial fiber cords, so that expansion during tire high-speed rotation can be suppressed. However, steel cords have the disadvantage of low elongation properties, which poses a major problem in tire manufacture. That is, in tire manufacture, a molding process (so-called vulcanization process) is performed at a high temperature and a high pressure, and at this time, the tire expands in the radial direction. The steel cords arranged in the belt and carcass parts are arranged in such a way that both ends are cut free and the industrial fiber cords have a certain degree of elongation characteristics. It can follow the expansion of the tire during processing. However, if a steel cord with low elongation characteristics of the cord itself is used for a zero degree belt cord, this steel cord is wound many times without being cut along the direction of rotation of the tire. I cannot follow it. Therefore, after the tire is vulcanized, the zero degree belt cord cannot be stopped in the vicinity of the desired belt portion, which induces deformation of the tire and suppresses the expansion of the tire during high speed rotation, which is the original purpose. Can not demonstrate.
[0007]
The present invention has been made in view of the above problems, and is a steel cord embedded in a tire as a zero-degree belt cord for heavy duty tires such as trucks and buses. Expansion in the radial direction of the tire in a vulcanization process at the time of tire formation It is an object of the present invention to provide a steel cord that has an appropriate elongation characteristic that can follow a tire, has a small elongation characteristic after molding of the tire, and can suppress expansion of the tire in the radial direction due to high-speed continuous rotation of the tire. .
[0008]
[Means for Solving the Problems]
[Solution 1]
The cord of the present invention for solving the above-mentioned problems is obtained by twisting 4 to 7 strands having a wire diameter of 0.20 to 0.45 mm, which are arranged by winding a plurality of turns in the vicinity of both side edges of the belt portion of the tire. This steel cord has a 1 × n structure, and the steel cord has a substantially spiral or substantially flat corrugation, and the corrugation satisfies the following formula.
P / p = 1.0-1.8
D / d = 2.0 to 2.9
P: Corrugated pitch (mm)
p: Twist pitch (mm)
D: Apparent cord outer diameter or wave height (mm)
d: Cord diameter (mm)
[0009]
By the way, numerical limitation by the above configuration is due to the following reasons.
That is, the wire diameter of the steel cord is set to 0.20 to 0.45 mm because sufficient strength cannot be obtained if the strand diameter is less than 0.20 mm. This is because there is a need to increase the cost and the cost becomes high, and if it is thicker than 0.45 mm, the rigidity becomes too high and the tire performance deteriorates.
Moreover, the reason for limiting to the single layer twist of 1Xn structure is that it can be twisted once and the production cost can be kept lower than that of the double twisted structure of n + m structure. This is because the number of strands is suitable for single layer twisting.
[0010]
Further, the ratio of the cord corrugation pitch P to the twist pitch p, P / p being 1.0 to 1.8 is less than 1.0 when the twist pitch is larger than the cord corrugation pitch. This is because the twisted shape collapses in the corrugation process, and when this is used for a tire, stress concentrates on the location where the twist is broken, and fatigue resistance is reduced.
On the other hand, if P / p exceeds 1.8, the corrugated pitch becomes too large, a uniform cord waveform cannot be obtained, and an appropriate elongation characteristic cannot be obtained.
[0011]
Further, the apparent outer diameter of the cord or the ratio of the wave height D to the cord diameter d, and D / d being 2.0 to 2.9 are appropriate because the corrugation amount is too small below 2.0. This is because the elongation characteristics cannot be obtained, and when it exceeds 2.9, the apparent outer diameter or wave height becomes too large, and adjacent cords come into contact with each other in the sheet process before vulcanization processing, which is a tire forming process. This is because, when a tire is vulcanized in a state, when a load is applied due to road surface unevenness or the like, the load is not evenly applied to the cord, and the life of the tire is reduced.
[0012]
[Solution 2] Another cord of the present invention for solving the above-mentioned problem is that a wire having a wire diameter of 0.20 to 0.45 mm disposed by winding a plurality of turns in the vicinity of both sides of the belt portion of the tire is 8 a steel cord 12 twisted 1X 12 structure or n + m structure, the steel cord has a substantially spiral or generally planar wave habit, those habit the waveform has to satisfy the following formula is there.
P / p = 1.0 to 1.8 D / d = 2.0 to 2.9 P: Corrugated wrinkle pitch (mm)
p: Twist pitch (mm)
D: Apparent cord outer diameter or wave height (mm)
d: Cord diameter (mm)
[0013]
A cord arranged by winding a plurality of turns in the vicinity of both side edges of the belt portion of the tire is a steel cord having a 1 × 12 structure or an n + m structure in which 8 to 12 strands having a wire diameter of 0.20 to 0.45 mm are twisted together. Since the steel cord has a substantially spiral or substantially flat corrugation, when the molding process is performed at a high temperature and high pressure in the tire manufacturing process, the tire expands in the radial direction. The cord follows the radial expansion of the tire by the extension of the spiral or substantially flat corrugation, and the steel cord (zero-degree belt cord) is set near the both side edges of the desired belt part. Elongation characteristics are small, and the tire is prevented from expanding in the radial direction due to high-speed continuous rotation. Also, the wire diameter of the steel cord is set to 0.20 to 0.45 mm because sufficient strength cannot be obtained if the strand diameter is less than 0.20 mm. This is because there is a need to increase the cost and the cost becomes high, and if it is thicker than 0.45 mm, the rigidity becomes too high and the tire performance deteriorates. In addition, the point made into the steel cord of the 1 * 12 structure or n + m structure which twisted 8-12 strands is a range which can be practically used as the said cord. The ratio of the cord corrugation pitch P to the twist pitch p, the reason why P / p is 1.0 to 1.8, the ratio of the apparent outer diameter or wave height D of the cord to the cord diameter d, D / The reason why d is set to 2.0 to 2.9 is the same as the reason described in [Solution 1].
[0014]
It is preferable that the substantially spiral corrugation direction in [Solution 1] is opposite to the twist direction. The reason is as follows.
That is, the steel cord having the above configuration is a so-called closed type cord in which adjacent strands are gradually tightened. When corrugation is applied to this cord, twisting in the direction opposite to the twisting direction and twisting in the direction of twisting will twist in the direction of untwisting, so a gap for further infiltration of rubber is formed between each strand of the cord Because it can be done.
[0015]
The cord of the present invention has an appropriate elongation characteristic by specifying the size of the corrugation that is applied to the cord, and the cord ring increases in diameter following the expansion of the tire in the vulcanization process at the time of tire manufacture. The belt can be stopped in the vicinity of the desired belt portion. In addition, after vulcanization, the cord is stretched to some extent to form an integral structure with the rubber and has high strength, so that expansion during high-speed rotation of the tire is suppressed.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 (a) is a schematic plan view of a cord showing an embodiment of the present invention. Code 1 shown in FIG. 1 (a), 1Xn structure strands combined 4-7-ply of wire diameter 0.20～0.45Mm, or 8-12 present twisted 1X 12 structure or n + m structure steel The cord itself has a substantially spiral corrugation, the ratio of the pitch P of the corrugation to the twist pitch p, P / p is 1.0 to 1.8, and the apparent outer diameter of the cord The ratio of D to cord diameter d, D / d is 2.0 to 2.9. In addition, the apparent outer diameter of the steel cord 1 in FIG. 1A means the apparent outer diameter of the cord that is corrugated in a substantially spiral shape. Further, the “substantially spiral shape” in the configuration of the present invention includes an elliptical shape or a track shape, and D in this case means a “major diameter”.
[0017]
FIG.1 (b) shows other embodiment of this invention, and a wrinkle is a substantially planar shape. Here, the wave height of the steel cord 10 means the amplitude in the substantially flat waveform waking (two-dimensional wave) as shown in FIG.
[0018]
【Example】
Next, an example will be specifically described in comparison with a comparative example.
The steel type is equivalent to SWRS82A JIS wire diameter of 5.5mm, and after repeated patenting and wire drawing, the surface is subjected to brass plating, and then wire drawing to wire diameter of 0.20 to 0.45mm. After finishing, a 1Xn structure obtained by twisting 4, 6 and 7 strands, or a 1X12 structure obtained by twisting 12 strands or a 3 + 9 structure, a steel cord having a corrugated weave with a substantially spiral corrugation was produced.
[0019]
As a means for applying a substantially spiral wave shape to the cord, there is a method in which the cord is fed by a tacking device that rotates using the supplied cord as an axis. Further, as means for applying a substantially planar corrugation, there are a method of pressing the substantially spiral corrugation and pressing it with a roller or the like, and a method of engaging a gear or the like.
[0020]
The cord of the present invention was manufactured by passing the cord between three pins provided on a brazing device that rotated at high speed. The adjustment of the apparent outer diameter and pitch was determined by variously selecting the diameter and interval of the crimping pins, the degree of pressing, the tension of the cord, and the rotational speed of the tacking device.
[0021]
In manufacturing the cord, the apparent spiral outer diameter and pitch were changed, and the cord of the example satisfying the conditions of the present invention and the cord of the comparative example deviating from the conditions of the present invention were manufactured.
[0022]
In the above cords, whether the cords were twisted or not, the presence or absence of corrugation defects, and the elongation when a 50 N load was applied to the cords were evaluated. The evaluation criteria for the elongation rate was 1.0 to 2.5% as acceptable. This reference value is a value determined on the assumption that an internal pressure is applied during the vulcanization process in the manufacture of the tire and the bulge in the radial direction at that time. The results are shown in Tables 1 and 2.
[0023]
Table 1 below shows the test results for Examples of the invention according to [Solution 1].
[Table 1]

[0024]
Table 2 below shows the test results for the examples of the invention according to [Solution 2]. This is for the 1 × 12 structure and the 3 + 9 structure, which are considered to be less effective in the above [Solution 2].
[Table 2]

As is apparent from Tables 1 and 2, all the cords of the present invention passed in terms of elongation, and there were no twist breaks and corrugated defects.
It was also confirmed that similar effects can be obtained with other steel types and substantially planar corrugations.
[0025]
【The invention's effect】
Since the cord of the present invention has the above-described configuration, it has appropriate elongation characteristics and strength, and the cord ring increases in diameter following the expansion of the tire in the vulcanization process at the time of tire manufacture. In addition, since the elongation characteristic is small after the tire molding, expansion in the radial direction of the tire due to high-speed continuous rotation can be suppressed. Therefore, when the cord of the present invention is used for heavy duty tires for trucks and buses, the shape retention of the tire can be improved and the life can be remarkably improved.
[Brief description of the drawings]
FIG. 1A is a schematic plan view of a cord showing an embodiment of the present invention and a cross-sectional view in the direction of an arrow. (B) is the schematic plan view and sectional drawing of an arrow direction of the code | cord | chord which shows other embodiment of this invention.
FIG. 2 is a schematic cross-sectional perspective view showing the structure of a conventional tire.
FIG. 3 is a schematic cross-sectional perspective view showing a structural example of another conventional tire in which the vicinity of the belt portion is reinforced with industrial fibers.
[Explanation of symbols]
1, 10 ... code 20 ... belt part reinforcement code (belt code)
30 ... Carcass part reinforcement code (carcass code)
A ... Tire reinforcement code P ... King pitch p ... Twist pitch D ... Apparent outer diameter, Wave height d ... Code diameter

Claims (4)

A steel cord having a 1 × n structure in which 4 to 7 strands having a wire diameter of 0.20 to 0.45 mm, which are arranged by being wound a plurality of times in the vicinity of both side edges of a belt portion of a tire, are twisted. A steel cord for reinforcing tires having a spiral or substantially planar corrugation, and the corrugation satisfies the following formula.
P / p = 1.0 to 1.8 D / d = 2.0 to 2.9 P: Corrugated wrinkle pitch (mm)
p: Twist pitch (mm)
D: Apparent cord outer diameter or wave height (mm)
d: Cord diameter (mm) A steel cord having a 1 × 12 structure or an n + m structure in which 8 to 12 strands having a wire diameter of 0.20 to 0.45 mm, which are arranged by being wound a plurality of times in the vicinity of both side edges of a belt portion of a tire, are twisted, A steel cord for reinforcing tires, characterized in that the steel cord has a substantially spiral or substantially planar corrugation, and the corrugation satisfies the following formula.
P / p = 1.0 to 1.8 D / d = 2.0 to 2.9 P: Corrugated wrinkle pitch (mm)
p: Twist pitch (mm)
D: Apparent cord outer diameter or wave height (mm)
d: Cord diameter (mm) The steel cord for reinforcing tires according to claim 1, wherein the direction of wrinkling of the substantially spiral corrugation is opposite to the twisting direction. A tire using the steel cord for tire reinforcement according to any one of claims 1 to 3.

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