JPH0672369B2 - Steel cord - Google Patents

Description

TECHNICAL FIELD The present invention relates to a steel cord which can be suitably used for reinforcing a tire, can enhance corrosion resistance, and can improve the service life.

[Conventional technology]

In pneumatic tires and the like, steel cords are often used for carcass plies, belt plies, etc. in order to improve structural strength, durability, etc., and such steel cords are usually, for example, as shown in FIG. In addition, an inner sheath B and an outer sheath C formed by spirally winding an inner filament b ... and an outer filament c ... around a core A formed by twisting three to four core filaments a ... Are used. . It should be noted that the figure shows a 3 + 9 + 15 structure.

[Problems to be Solved by the Invention]

However, in such a conventional structure,
Since the core filaments a ... Are intimately twisted with each other, a cavity d into which rubber cannot penetrate is formed continuously in the longitudinal direction at the center of the core A.

Therefore, for example, in the tread portion, when damage reaches the cord, moisture or the like penetrating from the damaged portion propagates through the cavity d, and as a result, filaments, rubber separation, and corrosion such as rust. The tire life was greatly reduced by causing breakage and damage of the cord.

An object of the present invention is to provide a steel cord which can improve the corrosion resistance and the service life by adjusting the tensile strength and the bending rigidity based on the fact that the core is formed by one core filament.

[Means for Solving the Problems]

In order to achieve the above object, the steel cord of the present invention comprises a core consisting of one core filament, and three or more and seven or less inner filaments wound around the core in a spiral line and having the same diameter. And an outer filament of 7 or more and 13 or less and the same diameter wound around the inner layer in a spiral shape with a spiral pitch larger than the spiral pitch of the inner layer and in the opposite spiral direction. On the other hand, at least the inner filament, the outer filament, the inner filament, and the outer filament have a diameter of 0.15 mm or more and 40 mm or less, and the core filament diameter is the inner filament diameter and the outer filament diameter 1.3. It is not less than twice and not more than 1.7 times, and a gap is provided between adjacent inner filaments and outer filaments.

[Action]

As described above, the steel cord of the present invention forms a core with one filament, eliminates the hollow portion at the center of the core, and provides a gap into which rubber can penetrate between the inner filament and the outer filament, respectively. Since each filament can be completely covered with rubber, it is possible to suppress breakage due to corrosion of each filament due to moisture infiltrating from the damaged part and separation between the filament and rubber, etc., and greatly improve the service life. .

Further, in order to optimize the tensile strength and bending rigidity of the cord while maintaining the above suppressing effect, 3 to 7 inner filaments and 7 to 13 outer filaments are used, and the diameter of the core filament is set to the inner filament. By making the diameter 1.3 times to 1.7 times the diameter of the outer filament, a gap is maintained between the cords to facilitate the intrusion of the rubber. In addition, by making the inner filament and the outer filament both have the same diameter, for convenience of production, the cord strength of each layer and the cord rigidity are constant, and the stability of the overall strength is maintained. Further, by making the spiral pitch of the outer layer larger than the spiral pitch of the inner layer and in the reverse spiral direction, the line contact between the inner and outer filaments is reduced, and the rubber penetration amount is made large and easy.

〔Example〕

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

The steel cord includes a core 3 composed of one core filament 2 and a core 3 wound around the core 3 in a spiral shape.
1, an inner layer 6 using 7 inner filaments 5 and an outer layer 9 using 7 to 13 outer filaments 7 ... 1
A cross-sectional view of the + 6 + 12 structure is illustrated.

Each of the filaments 2, 5 and 7 is made of a long steel wire which has a circular cross section and is continuous in the same cross section. The filaments 2, 5 and 7 have diameters d1, d2 and d3, respectively.
It is set to 0.15mm or more and 0.40mm or less.

If it is less than 0.15 mm, the strength is too small, and if it exceeds 0.40 mm, the fatigue resistance decreases, which is not suitable for practical use.

The type of the steel wire is not particularly limited, but one having a carbon content of 0.6 to 0.9% can be suitably adopted from the viewpoint of strength and cost, and its surface enhances adhesiveness with rubber. For the purpose, it is preferable to coat with copper, tin, zinc or the like or alloys thereof.

Further, in order to improve the service life which is one of the objects of the present invention, in addition to forming a solid core 3 having no cavity at the center by one core filament 2, the adjacent inner filaments 5, 5 It is necessary to set the gap g1 between them and the gap g2 between the outer filaments 7, 7 to 0.012 mm or more, respectively.

Here, the gap of 0.012 mm is the minimum gap that can be penetrated by rubber, which can be derived by various experiments.
When g1 and g2 are set to 0.012 mm or more, respectively, in combination with the formation of the solid core 3, the filaments 2, 5 and 7 are formed by the rubber that penetrates the steel cord 1 without forming a cavity. Can be completely covered. The gaps g1 and g2 are preferably 0.02 mm or more, more preferably 0.03 mm or more.

As a result, even when a damaged portion reaching the steel cord 1 is generated in the rubber product and moisture or the like penetrates from the damaged portion,
It is possible to suppress breakage due to corrosion of each filament due to the water content and separation between the filament and the rubber.

Further, in this product, since each filament is completely covered with rubber, adjacent filaments can be bent without repeated rubbing when repeatedly deformed, and heat generation, abrasion, residual strain, etc. due to the rubbing can be prevented. Can be reduced.

The gaps g1 and g2 can be expressed by the following equation.

Where N2 is the number of inner filaments 5 and N3 is the number of outer filaments 7. Thus, the gaps g1 and g2 are the diameters d1, d2, d3 and the number of filaments 2, 5 and 7, respectively.
The diameter d1 of the core filament 2 can be set to the diameter of the inner filament 5 in order to optimize the tensile strength and bending rigidity of the steel cord 1, although it can be set as appropriate by N2 and N3.
d2 and the diameter d3 of the outer filament 7 are 1.3 times or more and 1.7 times or less, the number N2 of the inner filaments 5 is 3 or more and 7 or less, and the number N3 of the outer filaments 7 is 7 or more and
It should be 13 or less.

This is because when the diameter d1 exceeds 1.7d2 and 1.7d3, the bending rigidity of the core 3, that is, the bending rigidity of the entire steel cord becomes excessively large as compared with the tensile strength, making it difficult to use as a reinforcing cord for rubber products. This is because the cord strength becomes insufficient when is less than 1.3d2 and 1.3d3. On the other hand, when the diameter d1 exceeds 7 in the above range, the inner filament 5 exceeds 13 and the outer filament 7 exceeds 13
If it is difficult to form g2, and if the number of inner filaments 5 is less than 3 and the number of outer filaments 7 is less than 7, the tensile strength of the steel cord 1 will be insufficient and the gap
Since g1 and g2 are larger than the diameter of the filaments that are placed inside, the gap between the filaments that are placed inside when bent is g1 or g2
Cause a protrusion from.

In particular, by using 6 to 7 inner filaments 5 and 12 to 13 outer filaments 7, tensile strength and flexural rigidity can be enhanced in a well-balanced manner, and it can be used in pneumatic tires that require toughness. And

The spiral pitch P3 of the outer filament 7 in the steel cord 1 is set to be larger than the spiral pitch P2 of the inner filament 5. Table 1 shows the case of 1.6 times. Further, as shown in Table 1, the inner layers are S-twisted and the outer layers are Z-twisted, and the twisting directions are opposite. This prevents the outer filament 7 from falling into the valley portion between the inner filaments 5 and 5 while reducing the line contact, and facilitates the infiltration of rubber into the steel cord 1. The pitches P2 and P3 are preferably 2 to 20 mm. If the pitch is less than 2 mm, it takes a long time to wind the filament, resulting in poor productivity, and if the pitch is 20 mm or more, the filament is likely to break due to bending fatigue.

In the steel cord 1 of the present invention, the core filament 2 may be made of stainless steel or other non-corrosive metal and synthetic resin. Even in such a case, separation and other components are eliminated by eliminating voids inside the core 3. Corrosion of the inner filament 5 and the outer filament 7 can be prevented.

〔Concrete example〕

The steel cords of the example products 1 and 2 based on the specifications in Table 1 were prototyped, and the air permeation amounts of the rubber products using the example products 1 and 2 were compared with the conventional products 1 and 2.

As is apparent from Table 1, the products 1 and 2 of Example have an air permeation amount of 0, that is, the rubber is densely infiltrated into the steel cord without forming a cavity.

[Advantages of the Invention] As described above, the steel cord of the present invention forms a solid core with one core filament and has a gap between the inner filament and the outer filament into which rubber can penetrate. , Each filament can be completely covered by the rubber that penetrates without forming a cavity,
Corrosion, separation, abrasion, etc. of the filament can be suppressed and the service life of the rubber product can be improved. Moreover, by controlling the diameter of the core filament and the number of twisting pitches, directions, diameters, etc. of the inner filaments and the outer filaments, the tensile strength and bending rigidity can be optimized while maintaining the above-mentioned suppressing effect.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, and FIG. 2 is a sectional view explaining a conventional technique. 2 ... core filament, 3 ... core, 5 ... inner filament, 6 ... inner layer, 7 ... outer filament, 9 ... outer layer.

Claims (3)

[Claims] 1. A core comprising one core filament,
An inner layer using 3 or more and 7 or less and inner filaments having the same diameter wound around the core in a spiral shape, and spirally around the inner layer and larger than the spiral pitch of the inner layer At least the inner filament, the outer filament, the inner filament, and the outer filament, while having an outer layer using an outer filament of 7 or more and 13 or less and both having a spiral pitch and an opposite spiral direction Is 0.15 mm or more and 0.40 mm or less, and the diameter of the core filament is 1.3 times or more and 1.7 times or less the diameter of the inner filament and the diameter of the outer filament, and a gap is provided between adjacent inner filaments and outer filaments. Become a steel cord. 2. The steel cord according to claim 1, wherein the inner layer is composed of 6 or more and 7 or less inner filaments. 3. The steel cord according to claim 1, wherein the outer layer is composed of 12 or more and 13 or less outer filaments.