JPH0640620Y2 - Steel cord for reinforcing rubber products - Google Patents

Description

TECHNICAL FIELD The present invention relates to a steel cord for reinforcing rubber products such as tires, rubber crawlers, and belts.

2. Description of the Related Art As a steel cord for reinforcing a conventional rubber product, for example, a pneumatic radial tire for heavy load, as shown in FIG. 2, a core 2 formed by twisting three filaments 1 and a periphery of the core 2. An inner sheath 4 composed of nine filaments 3 spirally wound around the inner sheath 4 and an inner sheath 4
A layer-twisted steel cord 7 of 3 + 9 + 15 twists is known, which has an outer sheath 6 consisting of 15 filaments 5 spirally wrapped around the. In addition, 8 is a spiral filament. Steel code 7 like this
Was excellent in tread cut resistance and belt edge separation resistance, but had some problems in cut separation resistance. It ’s in core 2,
Since the filaments 1, 3, 5 forming the outer sheaths 4, 6 are in close contact with each other, a space where rubber cannot enter is formed inside the steel cord 7, but such a space is formed inside the steel cord 7. If there is a cut, for example, the tread has a cut, and the water content comes from the cut.
This is because the water penetrates into the space and rusts when it reaches, and separation occurs at the interface between the steel cord 7 and the rubber.

In order to solve such a problem to some extent, a steel cord as disclosed in, for example, JP-A-54-50640 has been proposed. By reducing the number of filaments constituting the inner sheath and the outer sheath, this one forms a minute gap through which rubber can pass between the filaments of these inner and outer sheaths.
The rubber is made to penetrate into the inner and outer sheaths.

Problems to be solved by the invention However, even with such a steel cord,
The cut separation resistance could not be sufficiently improved. The reason is that, in the above-mentioned steel cord, the core is composed of three filaments that are in close contact with each other, so that a triangular space where rubber cannot penetrate is still left at the center of the core. As a result, when water enters this space, rust occurs and the separation as described above also occurs.

Means for Solving the Problems These problems are caused by a core composed of one filament, an inner sheath composed of m filaments spirally wound around the core, and a spiral surrounding the inner sheath. A steel cord for reinforcing a rubber product, comprising: an outer sheath wound around n filaments,
The number of filaments m is in the range of 3 to 5 and the number of filaments n is in the range of 7 to 11, and the diameter of the filaments constituting the core, inner and outer sheaths is 0.20 mm to 0.40 mm. It is possible to solve the problem by using steel cords in which the diameters of the filaments constituting the outer sheath are equal to each other.

Operation First, in this invention, since the core is composed of one filament, there is no room for producing a space inside the core. Moreover, since the number of filaments forming the inner and outer sheaths is set within the range described above, a minute gap through which rubber can pass is formed between these filaments. Therefore, the space around the filaments of the core, inner and outer sheaths is filled with rubber. As a result, even if moisture reaches the steel cord,
Since there is almost no space where this water penetrates around the filament of the steel cord, the separation hardly occurs.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 11 is a steel cord for reinforcing a rubber product such as a pneumatic tire, a rubber crawler, a belt, and a pressure-resistant hose, and the steel cord 11 has a core 13 composed of one filament 12 in the center. This core 13
An inner sheath 14 is helically wound around the periphery of the inner sheath 14, and the inner sheath 14 is composed of m steel filaments 15. Here, the number m of filaments 15 must be within the range of 3 to 5. The reason is that if m is 2 or less, the shape of the steel cord 11 becomes unstable. On the other hand, if m is 6 or more, the distance between the filaments 15 becomes too narrow, and the rubber inside the inner sheath 14 becomes too narrow. Can no longer enter. The twist pitch of the filaments 15, that is, the twist pitch S ₁ of the inner sheath 14 is preferably in the range of 6 mm to 18 mm. The reason is that when the twist pitch S ₁ of the inner sheath 14 is less than 6 mm, the cord strength of the steel cord 11 becomes too low.
This is because if it exceeds 18 mm, fatigue resistance is reduced and tire durability is reduced. An outer sheath 16 is spirally wound around the inner sheath 14, and the outer sheath 16
Consists of n steel filaments 17. Here, the number n of filaments 17 must be in the range 7 to 11. The reason is that if n is 6 or less, the shape of the steel cord 11 becomes unstable. On the other hand, n
If 12 is 12 or more, the distance between the filaments 17 becomes too narrow and the rubber cannot penetrate into the outer sheath 16. The twist pitch of such a filament 17, that is, the twist pitch S ₂ of the outer sheath 16 is longer than the twist pitch S _{1 of} the inner sheath 14, and is equal to the twist pitch S ₁ of the inner sheath 14.
It is preferable that the length is within 10 mm. The reason is,
If the twist pitch S ₂ of the outer sheath 16 is the same as or shorter than the twist pitch S _{1 of} the inner sheath 14, when the steel cord 11 is tensioned, the load on the inner sheath 14 becomes too large and the cord durability is increased. On the other hand, the twist pitch S ₂ of the outer sheath 16 is 10 times smaller than the twist pitch S ₁ of the inner sheath 14.
This is because if the length is longer than the length added in mm, the fatigue resistance is reduced and the tire durability is reduced. The filaments 15 and 17 of the inner sheath 14 and the outer sheath 16 may be twisted in the same direction or in the opposite direction, but if twisted in the opposite direction, the rubber will easily enter the steel cord 11. If anything, the opposite direction is preferable. Further, the diameter of the filaments 12, 15, 17 is 0.20 mm to 0.
Must be within 40mm. The reason is 0.
If it is less than 20 mm, the strength of the steel cord 11 is insufficient,
This is because when used for reinforcing the belt layer of a tire, its rigidity is insufficient. On the other hand, if it exceeds 0.40 mm, the diameter of the steel cord 11 becomes thicker, the pitch between cords becomes narrower, and the amount of rubber interposed between the steel cords 11 becomes smaller. As a result, the stress transfer of the cut input is suppressed. It is impossible to do so, and the tread is likely to be cut. It is more preferable that the diameters of the filaments 12, 15, 17 constituting the core 2, the inner and outer sheaths 4, 6 are in the range of 0.24 mm to 0.36 mm for the above reason. Thus, the steel cord 11 has a three-layer twist structure of 1 + m + n.

When vulcanizing a rubber product in which the steel cords 11 are embedded as described above, a small gap is formed between the filaments 17 and 15 of the outer sheath 16 and the inner sheath 14 of each steel cord 11 so that the rubber is easy to use. To these filaments 17,1
It passes through between 5 and penetrates into the outer sheath 16 and the inner sheath 14. As a result, the space around the filaments 12, 15, and 17 of the core 12 and the inner and outer sheaths 14 and 16 is almost completely filled with rubber. If you use such a rubber product for a long time,
A cut reaching the embedded steel cord 11 may enter the rubber product, but even if moisture is guided to the steel cord 11 through such a cut, there is a space inside the steel cord 11. In addition, since all the filaments 12, 15 and 17 are adhered to the rubber, rust due to such water hardly occurs and the cut separation resistance is remarkably improved.

As the steel cord according to the present invention, a steel cord having a carbon content of 0.70 to 0.90 wt% is usually used.
A steel cord having a carbon content of 0.80 to 0.85 wt% is more preferable because it has high strength and good toughness.

Next, a test example will be described. In this test, two types of conventional tires reinforced with conventional steel cords and six test tires reinforced with steel cords to which the present invention was applied were used.
Three types of comparative tires were also prepared, reinforced with steel cords outside the scope of this invention. Here, the twist pitch of the steel cord reinforcing the conventional tires 1 and 2 is 6 mm in the core, 12 mm in the inner sheath, and 18 mm in the outer sheath, and the twisting of the steel cord reinforcing the test tire 3 Pitch is straight core, inner sheath is 11.4m
m, the outer sheath is 20.7 mm, and the twist pitch of the steel cord that reinforces tires other than the above is that the core is straight, the inner sheath is 10 mm, and the outer sheath is 18 mm. Further, in each steel cord, the diameters of the filaments forming the core, the inner sheath, and the outer sheath are all the same. The carbon content of all steel cords is 0.82 wt%
Is. Each tire is a large radial tire for trucks and buses reinforced by four layers of belt plies, and the size is 1000R20 14PR. In addition, the steel cords shown in the attached table were embedded in the second and third belt plies that intersect each other across the tire equatorial plane of each tire while intersecting the tire equatorial plane at an angle of 20 degrees. The chord strength and chord number are adjusted as shown in the attached table so that the total strength is the same. 7.25 on such a tire
After filling the internal pressure of kg / cm ² , 3 normal roads including 20% bad roads
The tire was run at 100% load for 10,000 km and the cut separation resistance of each tire at the end of the run was measured and evaluated. The results are shown in the attached table. As is apparent from this appendix, the test tires have significantly improved cut separation resistance as compared with the conventional and comparative tires. Here, the cut separation resistance is obtained by separating the third and fourth belt plies of each tire and looking for a portion where a tread cut is generated on the third belt ply, and a steel cord in the portion where the tread cut is generated. It is the result of having measured the maximum length of the adhesion failure of with a caliper. Further, the above-mentioned tires after actual running were measured and evaluated for the tret-cut resistance and the belt edge separation resistance, and the results are shown in a separate table. From these results, it can be seen that the tread cut resistance and the belt edge separation resistance of the test tire are not deteriorated to the same extent as the conventional tire. Here, the tret cut resistance was obtained by peeling the tread of each tire after the above-mentioned actual running on the outermost layer belt ply, obtaining the number of cuts reaching the outermost belt ply, and indexing this. Here, the numerical value of the conventional tire is set to 100, and the larger the index, the better the tread cut resistance. On the other hand, the belt edge separation resistance is that the cord end of the third belt ply is exposed by separating the second and third belt plies of each tire after the actual running described above.
The maximum length of the adhesion failure occurring at the cord end of the third belt ply is measured with a caliper from the cord end,
The measurement was performed from the second belt ply side.

Effects of the Invention As described above, according to the present invention, the cut separation resistance of a rubber product can be dramatically improved without lowering other performances such as tread cut resistance and belt edge separation resistance. .

[Brief description of drawings]

FIG. 1 is a sectional view of a steel cord showing an embodiment of the present invention, and FIG. 2 is a sectional view of a conventional steel cord. 11 …… Steel cord 12,15,17 …… Filament 13 …… Core, 14 …… Inner sheath 16 …… Outer sheath

Claims (1)

[Scope of utility model registration request] 1. A core made of one filament, an inner sheath made of m filaments spirally wound around the core, and an outer sheath made of n filaments spirally wound around the inner sheath. A steel cord for reinforcing rubber products, comprising a sheath, wherein the number of filaments m is in the range of 3 to 5 and the number of filaments n is in the range of 7 to 11, and further, The diameter of the filaments forming the inner and outer sheaths is in the range of 0.20 mm to 0.40 mm, and the diameters of the filaments forming the outer sheath are the same, which is a steel cord for reinforcing rubber products.