JP4373585B2 - Steel cord for reinforcing rubber articles and pneumatic tire using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a steel cord used as a reinforcing material for rubber articles such as pneumatic tires and industrial belts. In particular, the present invention aims to increase cord breaking strength and / or reduce cord rigidity in comparison with the same cord diameter. The present invention relates to a steel cord for reinforcing rubber articles and a pneumatic tire using the steel cord for improving durability and / or productivity.
[0002]
[Prior art]
Rubber articles reinforced with steel cords include pneumatic tires and industrial belts. Here, for example, in a pneumatic tire, a structure in which a multi-layer belt is disposed on the outer side in the radial direction with a carcass as a skeleton and is reinforced, and a steel cord is used as a reinforcing material for the belt and the carcass. . In particular, large tires for construction vehicles and the like are particularly rough and uneven and run under heavy loads, so the (3 + 9 + 15) + 6 × (3 + 9 + 15) structure or (3 + 9) + 6 × A steel cord having a (3 + 9) structure is generally adopted.
[0003]
The steel cord shown in FIGS. 5 and 6 is a cross-sectional view showing a conventional steel cord adopted in such a construction vehicle tire, and FIG. 5 is a (3 + 9 + 15) + 6 × (3 + 9 + 15) structure ( Conventional example 1), and FIG. 6 shows a (3 + 9) + 6 × (3 + 9) structure (conventional example 2). That is, FIG. 5 is a cross-sectional view showing a steel cord having a cord diameter of 5.4 mm in which six side strands 2 are twisted around the core strand 1, and the filaments 1a to 1c and 2a to 2c constituting each strand are shown. The diameter is 0.290 mm, the core strand 1 has a three-layer twist structure, and the side strand 2 also has a three-layer twist structure. Further, the steel cord shown in FIG. 6 has a cord diameter of 5.4 mm formed by twisting six side strands 2 around the core strand 1 as in FIG. The diameters of the filaments 1a to 1b and 2a to 2b are all 0.430 mm, and the core strand 1 and the side strand 2 have a two-layer twist structure.
[0004]
[Problems to be solved by the invention]
However, with the increase in size of construction vehicles, conveyor belts, etc., steel cords with even greater cord breaking strength have been demanded. However, simply increasing the diameter of the filaments that make up the steel cord results in excessively high cord rigidity, which makes it difficult to cut the steel cord or turn the end of the carcass, for example, during tire molding operations. It will drop significantly. In addition, when the cord breaking strength is not so important, it is natural that a steel cord having a low cord rigidity is required from the viewpoint of workability and the like.
[0005]
Further, if the filament diameter is increased in order to increase the cord breaking strength, the weight of the steel cord increases, which leads to an increase in the weight of the tire and the like, which is not preferable. Furthermore, particularly severe repeated compressive stress acts on the tire, so that a filament having a large diameter may break due to compression fatigue at an early stage of running.
[0006]
In view of the above, the present invention is based on the premise that the cord diameter is substantially the same as that of a conventional steel cord, and can reduce the cord rigidity while at least equaling the cord breaking strength, or conversely, the cord It is an object of the present invention to provide a steel cord for reinforcing rubber articles that can increase the strength at which the cord breaks while maintaining the rigidity at least equal to or less.
[0007]
It should be noted that the premise of the comparison that the cord diameters are substantially the same is, for example, to increase the strength of the belt layer of the tire by increasing the cord breaking strength x the number of cords driven, but the separation resistance, etc. From the viewpoint of securing the tire performance, there is a limit to the increase in the number of cords to be driven (decrease in the distance between cords), and the larger the cord diameter, the more severely the limitation on the number of cords to be driven. Therefore, the cord breaking strength per cord unit cross-sectional area is an important factor. In addition, the description of the cord rigidity in this specification mainly indicates bending rigidity.
[0008]
[Means for Solving the Problems]
The present invention has been made in order to solve the above problems. The gist of the present invention is that, first, the cord diameter is 3.5 to 7.0 mm, and the filament diameter constituting the cord is 0.175 to 0. it relates to rubber articles reinforcing steel cord of .400mm.
[0009]
The code structure is a (3 + 9 + 15) + 8 × (3 + 9 + 15) structure, a (3 + 9 + 15) + 6 × (3 + 9 + 15) + 12 × (3 + 9 + 15) structure, or a (3 + 9 + 15) + 6 × (3 + 9) + 12 × (3 + 9) structure. it is a steel cord is.
[0010]
Furthermore, when the cord structure is a (3 + 9 + 15) + 8 × (3 + 9 + 15) structure, the core strand diameter is made larger than the side strand diameter, and the filament diameter constituting the core strand is made larger than the filament diameter constituting the side strand. It is preferable to increase the size. Further, in the case of (3 + 9 + 15) + 6 × (3 + 9 + 15) + 12 × (3 + 9 + 15) structure, it is preferable that all strand diameters are the same and all filament diameters are also the same.
[0011]
Each filament is preferably made of high strength steel having a carbon content of 0.80 to 0.85% by weight.
[0012]
The gist of the present invention is secondly related to a pneumatic tire using a steel cord for reinforcing rubber articles in at least one layer of a belt and / or carcass of the tire for a construction vehicle. is there. That is, by adopting the steel cord of the present invention for a construction vehicle tire that requires a particularly large cord breaking strength, a pneumatic tire with greatly improved durability and / or productivity can be obtained.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
One feature of the steel cord for reinforcing rubber articles of the present invention is that eight or more side strands are twisted around one core strand. That is, if the side strands are twisted to 7 or less, the effect of reducing the cord rigidity cannot be obtained. This is because the cord rigidity is roughly proportional to the fourth power of the filament diameter × the number of filaments, so the filament diameter has a large effect, but the cord diameter is the same as the conventional steel cord that is the premise of the present invention. If the number of side strand twists is 7 or less under the conditions, there is a limit to the thinning of the filament diameter, and the thinning cannot be performed to the extent necessary for reducing the cord rigidity.
[0014]
On the other hand, as the upper limit of twisting of the side strands, the cord diameter of the present invention is defined as 3.5 to 7.0 mm, and the filament diameter is defined as 0.175 to 0.400 mm. own limitations arise in the number twisting of side strands by diameter and filament diameter.
[0015]
When the cord diameter is smaller than 3.5 mm, the cord breaking strength necessary for reinforcing rubber articles such as pneumatic tires and industrial belts cannot be obtained, and the cord diameter is larger than 7.0 mm. In such a case, the weight of the steel cord itself and the rubber coating the cord becomes too heavy, making it difficult to apply to a tire or the like from the viewpoint of molding workability.
[0016]
In addition, when the filament diameter is smaller than 0.175 mm, not only the required cord breaking strength is obtained as in the case described above, but also the drawing process becomes difficult due to disconnection at the time of drawing, This is not realistic because the productivity of the filament is reduced. On the other hand, when the filament diameter is larger than 0.400 mm, the cord rigidity is approximately proportional to the fourth power of the filament diameter × the number of filaments as described above, so that the filament diameter becomes excessively large and the cord rigidity is reduced. Cannot be obtained.
[0017]
Thus, from the viewpoint of reducing the cord rigidity, the steel cord of the present invention has more side strands around the core strand than the conventional one in consideration of workability while ensuring the necessary cord breaking strength. It is in the point to twist.
[0018]
In addition, the steel cord for reinforcing rubber articles according to the present invention is also characterized in that the core strand has a three- layer twist structure and the side strand has a two-layer or three- layer twist structure. Here, in the first place, the core strand and the side strand have a layer twist structure. When the core strand or the side strand is a single strand, the filament diameter must be increased in comparison with the layer twist, and the fatigue property is reduced. Because. In addition, in the case of double twisting, the filament diameter must be made extremely thin, and a decrease in productivity due to disconnection in the wire drawing process can be considered.
[0019]
The core strand has a three-layer twist structure. When the core strand is twisted in two layers under the conditions of the present invention in which eight or more side strands are twisted together, the filament diameter constituting the core strand is changed to the side. This is because the tension load on the core strand and the side strand is greatly different from each other because the diameter of the filament constituting the strand must be made very large. On the other hand, the upper limit twist number of layers of the core strand and the side strands, as in the case of the upper limit of the twisting of the side strands that describes above, themselves limit the cord diameter and filament diameter arising.
[0020]
In the present invention, the core strand is a three-layer twist, and the side strand is a two-layer twist or a three-layer twist. This is because if the core strand is twisted more than four layers, the equipment for twisting the strand (for example, a tubular twisting machine) becomes longer during the production, and the tension of the twisted portion can be controlled uniformly. This is because it becomes difficult and it is difficult to align the filaments. Further, the cord breaking strength is generally increased as the distance from the outer surface of the core strand to the center of the adjacent side strand is shorter. Therefore, if the filament diameter is the same, the number of twisted layers of the side strand is smaller. The side strands are best when the two strands are twisted or three layers are twisted.
[0021]
More specifically, in the best embodiment of the steel cord for reinforcing rubber articles of the present invention, the cord structure is a (3 + 9 + 15) + 8 × (3 + 9 + 15) structure, or (3 + 9 + 15) + 6 × (3 + 9 + 15) + 12 × ( 3 + 9 + 15) structure. In addition, the code structure may be a (3 + 9 + 15) + 6 × (3 + 9) + 12 × (3 + 9) structure.
[0022]
Thus, from the viewpoint of increasing the cord breaking strength, the steel cord of the present invention is adjacent to the outer surface of the core strand while avoiding the occurrence of problems due to the twisted structure of the core strand and the side strand. The distance to the center of the side strand is shorter than before.
[0023]
Each filament is necessary and sufficient to ensure the strength of rubber articles such as pneumatic tires and industrial belts by using high tensile strength steel having a carbon content of 0.80 to 0.85% by weight. Cord breaking strength is obtained.
[0024]
Further, the steel cord for reinforcing rubber articles is preferably used for a belt and / or a carcass of a tire for a construction vehicle. In particular, the pneumatic radial tire for construction vehicles using the steel cord for reinforcing rubber articles as the belt has excellent durability, and is the best embodiment of the pneumatic tire of the present invention.
[0025]
【Example】
Embodiments of the present invention will be described below with reference to the drawings. The steel cord shown in a cross-sectional view in FIG. 1 is a first embodiment that is most suitable for use in a pneumatic radial tire for construction vehicles, and the cord structure is a (3 + 9 + 15) + 8 × (3 + 9 + 15) structure. That is, eight side strands 2 are twisted around the core strand 1, and the diameter of each filament 1a to 1c of the core strand 1 of 5.4 mm and three-layer twist is 0.390 mm and three-layer twist. The diameter of each filament 2a-2c of the side strand 2 is 0.240 mm.
[0026]
In Example 1, the core strand 1 and the side strand 2 have the same (3 + 9 + 15) structure, and the diameters of the filaments 1a to 1c constituting the core strand 1 are made larger than the diameters of the filaments 2a to 2c constituting the side strand 2. Thus, the diameter of the core strand 1 is made larger than the diameter of the side strand 2. That is, in Example 1, compared with the conventional example having the same cord diameter shown in FIGS. 5 and 6, the diameter of the side strand 2 is relatively narrowed, and from the outer surface of the core strand 1 to the center of the adjacent side strand 2. By shortening the distance D, the cord breaking strength is increased.
[0027]
As described above, in the first embodiment, the core strand 1 and the side strand 2 are (3 + 9 + 15) structures as in the conventional example 1 in FIG. The structure is focused on.
[0028]
The steel cord shown in the cross-sectional view in FIG. 2 is an embodiment 2 that is optimal for use in a pneumatic radial tire for construction vehicles, and the cord structure is a (3 + 9 + 15) + 6 × (3 + 9 + 15) + 12 × (3 + 9 + 15) structure. . That is, the core strand 1 and the side strands 2 each have a cord diameter of 5.4 mm obtained by twisting six side strands 2 of the first layer and twelve side strands 3 of the second layer around the core strand 1. , 3 are all the same diameter and are all three-layer twisted, and the diameters of the filaments 1a to 1c, 2a to 2c, 3a to 3c are all 0.175 mm.
[0029]
In Example 2, the core strand 1 and the side strands 2 and 3 have the same (3 + 9 + 15) structure, and the filaments 1a to 1c, 2a to 2c, and 3a to 3c all have the same small diameter. That is, in Example 2, compared to the conventional example shown in FIGS. 5 and 6, the filament diameter is reduced to the limit, thereby reducing the value of the filament diameter to the fourth power × the number of filaments to reduce the cord rigidity. Is. The reduction in breaking strength due to the thinning of each filament diameter is dealt with by providing the second side strand 3 in addition to the first side strand 2 within the same cord diameter range as the conventional example. ing.
[0030]
Thus, Example 2 has a structure that focuses on reducing the cord rigidity while providing the second layer side strands 3 so that the cord breaking strength is equal to or higher than that of the conventional example.
[0031]
The steel cord shown in a cross-sectional view in FIG. 3 is a third embodiment that is optimal for use in pneumatic radial tires for construction vehicles, and the cord structure is a (3 + 9 + 15) + 6 × (3 + 9) + 12 × (3 + 9) structure. . That is, around the core strand 1, 6 cords of the first layer 2 are twisted and 12 cords of the second layer 3 are twisted, and the cord diameter is 5.4 mm. The diameters of the filaments 1a to 1c are 0.175 mm, and the diameters of the filaments 2a to 2b and 3a to 3b of the two-side strands 2 and 3 are all 0.260 mm.
[0032]
In Example 3, the side strands have a two-layer twisted structure, but within the same cord diameter range as the conventional example, the second side strand 3 is provided in addition to the first side strand 2. Yes. Compared with the conventional example shown in FIGS. 5 and 6, the diameter of each filament 2a to 2b, 3a to 3b of the side strands 2 and 3 is reduced to reduce the value of the fourth power of the filament diameter × the number of filaments. Thus, the cord rigidity is reduced, and the second layer side strand 3 is provided, so that the cord breaking strength is equivalent to that of the conventional example.
[0033]
Next, FIG. 4 shows the structures of Example 1 (FIG. 1), Example 2 (FIG. 2), Example 3 (FIG. 3), Conventional Example 1 (FIG. 5), and Conventional Example 2 (FIG. 6). A comparison table of cord breaking strength and cord stiffness is shown. As is clear from FIG. 4, when the cord breaking strength and the cord stiffness of the conventional example 1 are compared as 100, the cord breaking strength is increased in the first embodiment although the cord stiffness is equal. Further, in Example 2, although the cord breaking strength is increased to some extent, the cord rigidity is greatly reduced. In Example 3, the cord breaking strength is almost the same, but the cord rigidity is greatly reduced.
[0034]
【The invention's effect】
As described above, according to the steel cord for reinforcing rubber articles of the present invention, the cord rigidity can be reduced while at least making the cord breaking strength at least equal to the conventional one. Further, when the cord rigidity is set to the same level as the conventional one, the cord breaking strength can be increased. Furthermore, by adopting the steel cord of the present invention for a construction vehicle tire that requires a particularly large cord breaking strength, a pneumatic tire with greatly improved durability and / or productivity can be obtained.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing Example 1 of a steel cord for reinforcing rubber articles according to the present invention.
FIG. 2 is a sectional view showing Example 2 of a steel cord for reinforcing rubber articles according to the present invention.
FIG. 3 is a sectional view showing Example 3 of a steel cord for reinforcing rubber articles according to the present invention.
FIG. 4 shows a comparison table between examples and conventional examples.
FIG. 5 is a cross-sectional view showing Conventional Example 1 of a steel cord for reinforcing rubber articles.
FIG. 6 is a cross-sectional view showing Conventional Example 2 of a steel cord for reinforcing rubber articles.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Core strand 1a ... Core filament 1b of core strand ... 1st sheath filament 1c of core strand ... 2nd sheath filament 2 of core strand ... 1st layer side strand 2a ... Core filament 2b of 1st layer side strand ... First sheath filament 2c of the first layer side strand ... Second sheath filament 3 of the first layer side strand ... Second layer side strand 3a ... Second layer side strand filament 3b ... Second layer side strand The first sheath filament 3c of the second layer, the second sheath filament D of the second side strand, the distance from the outer surface of the core strand to the center of the adjacent side strand

Claims (7)

A steel cord having a cord diameter of 3.5 to 7.0 mm and a filament diameter of 0.175 to 0.400 mm constituting the cord, wherein the cord structure is a (3 + 9 + 15) + 8 × (3 + 9 + 15) structure. Steel cord for reinforcing rubber articles. The steel cord for reinforcing rubber articles according to claim 1 , wherein the core strand diameter is larger than the side strand diameter, and the filament diameter constituting the core strand is larger than the filament diameter constituting the side strand. A steel cord having a cord diameter of 3.5 to 7.0 mm and a filament constituting the cord having a diameter of 0.175 to 0.400 mm, and the cord structure is (3 + 9 + 15) + 6 × (3 + 9 + 15) + 12 × (3 + 9 + 15) structure A steel cord for reinforcing rubber articles, characterized in that: The steel cord for reinforcing rubber articles according to claim 3 , wherein all strand diameters are the same and all filament diameters are the same. A steel cord having a cord diameter of 3.5 to 7.0 mm and a filament diameter of 0.175 to 0.400 mm, and the cord structure is (3 + 9 + 15) + 6 × (3 + 9) + 12 × (3 + 9) structure A steel cord for reinforcing rubber articles, characterized in that: The steel cord for reinforcing rubber articles according to any one of claims 1 to 5 , wherein each filament is a high strength steel having a carbon content of 0.80 to 0.85 wt%. An air for a construction vehicle tire, wherein the steel cord for reinforcing rubber articles according to any one of claims 1 to 6 is used for at least one of the belt and / or carcass. Enter tire.

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