JPH0210160Y2 - - Google Patents

Description

[Detailed explanation of the idea]

Industrial Application Field The present invention relates to improvements in rubber reinforcing steel cords used as reinforcing materials for tires, belts, etc. Conventional technology and its problems In general, this type of steel cord is constructed by twisting a plurality of strands of wire, for example, as shown in Fig. 3 A and B, 4 or 5 of the same strand 2 are twisted together. The steel cord 1 is formed by twisting them together.
A plurality of these steel cords 1 are arranged in parallel and covered with a rubber material, and are used as a rubber reinforcing material for tires, belts, etc. Thus, when a steel cord is used as a reinforcing material, the essential requirements are that it chemically adheres well to the rubber material and that the rubber material penetrates well into the steel cord. That is, in order for the steel cord to fully fulfill its role as a rubber reinforcing material, it is necessary that it be a complete composite with the rubber material. For example, when used in tires, if the adhesion between the steel cord and the rubber material and the infiltration of the rubber material into the steel cord are poor, a so-called separation phenomenon occurs in which the steel cord and the rubber material separate when the car is running. Significantly impairs tire function. In addition, moisture in the rubber or moisture that has entered through cuts in the rubber travels through the space A inside the steel cord and reaches the inside of the tire, causing rust on the steel cord wires and greatly reducing the strength of the steel cord. This has the disadvantage of causing the above-mentioned separation phenomenon to occur more quickly. For this reason, steel cords have recently been developed in which the rubber material penetrates into the center of the steel cord and is adhered to the entire circumference of each strand. Examples of this type of steel cord include a lightly twisted steel cord (Japanese Patent Laid-Open No. 55-90692), which is twisted together with a gap C between each strand, as shown in Figure 4 A and B; As shown in Figure 6 A and B, two equivalent groups of wires each consisting of two wires are twisted together to form a spiral body with a constant pitch and approximately constant shape. There is a steel cord in which the first group is a bundle of parallel wires and the twist pitch of the second group is in the same direction as the pitch of the spiral body and has the same value (Japanese Patent Application Laid-Open No. 193253/1983). . However, the sweetly twisted steel cord of the former,
In order to ensure that the rubber material adheres to the entire circumference of each wire and to allow sufficient penetration of the rubber material into the interior, the gap C between each wire must be a sufficient distance for the rubber material to penetrate, i.e.
It must be 0.02mm or more. However, if a sufficient gap C is provided between each strand, the twisted structure tends to become unstable during pressure vulcanization of the steel cord and rubber material, and as shown in Figure 5 A and B, the twisted structure tends to become unstable. The wire 2 may become offset or the twist may become uneven in the longitudinal direction of the steel cord. In such cases, even if the rubber material penetrates into the inside of the steel cord, it will elongate significantly under very low loads, which will have a negative impact on tire manufacturing operations, and if the steel cord buckles, it will cause stress concentration. This has the disadvantage that the multiple wires that make up the steel cord do not work as a unit and may cause fatigue failure. Next, the latter steel cord (hereinafter referred to as 2+2 configuration) consisting of two equivalent wire groups 3 and 4 each consisting of two wires has a rubber material adhered to the entire circumference of each element wire. Moreover, it is excellent in that it allows sufficient penetration of the rubber material into the interior. However, its structural shape is very different from conventional ones,
Since the structure shown by the - line and - line cross sections in Figure 6 appears periodically, when used as a tire reinforcing material, the steel cord is more likely to buckle than the part with the structure of this cross-sectional shape, and the steel cord is The disadvantage is that it is difficult for the plurality of strands to exhibit the effect as a unit, and local wear occurs in this part in case of fatigue failure. Therefore, the purpose of the present invention was to eliminate the above-mentioned drawbacks, and to ensure that the rubber material penetrates into the steel cord and to bond the rubber material and the steel cord, and to achieve extremely low load. To provide a steel cord having improved fatigue resistance by suppressing elongation in the steel cord and stabilizing the longitudinal twisting of the steel cord. Means for solving the problem In order to achieve the above-mentioned purpose, the present invention aims to solve the problem, especially in a steel cord composed of three strands.
Two side wires having a circular cross section and approximately the same wire diameter are arranged on both sides of a core wire having a flat or oval cross section and twisted at a certain pitch, and the core wire is It is characterized by being twisted at the same pitch and in the same direction. Embodiment An embodiment of the present invention will be described below with reference to the drawings. Figures 1 and 2 show an embodiment of the steel cord of the present invention, in which 5 is a core wire with a flat cross-section of 0.5 mm in width and 0.20 mm in thickness, and has a constant pitch P.
(10.0mm) and is twisted in the S direction. In addition, 6 is a side wire having a circular cross section and the same wire diameter (wire diameter 0.20 mmφ), and is twisted along both sides of the core wire 5 at the same pitch and in the same direction. Together, they constitute the steel cord 7 of the present invention. By the way, the core wire 5 may have an oval cross-section or may be pre-curved into a wavy shape. Furthermore, the wire used in the present invention may have its surface plated with copper alloy in order to improve adhesion to the rubber material. Furthermore, as a core wire, the width is 0.3 mm to 1.0 mm, and the thickness is
Approximately 0.15 to 0.5 mm, the diameter of the side wire is approximately 0.15 to 0.5 mm,
Twisting pitch or twisting pitch is 6mm to 30mm.
A range of is preferred. Function Next, a comparison will be made between the above embodiment of the steel cord of the present invention and a conventional steel cord.

[Table] As shown in the table above, the steel cord according to the present invention has very few twist defects compared to conventional products, and the rubber penetration rate (rubber penetration cross-sectional area/rubber penetration possible cross-sectional area x 100) is also 100%. % and also in fatigue resistance than any of the conventional products. Moreover, the initial load (5Kg) is lower than that of conventional lightly twisted cords.
It is superior to conventional wires in terms of the workability of stranded wires, as the cord elongates less and has better workability, the number of strands is smaller, and the core strands are easier to twist than round wires. By the way, in the steel cord of the present invention, the major axis of the core strand arranged approximately at the center is approximately 1.5 to 4.0 times the diameter of the side strands, and the minor axis is 0.75 to 1.2 times.
A range that is twice that is more appropriate. This range is particularly effective for stabilizing the twisted shape and eliminating buckling in fatigue tests. In addition, if the core wire is wavy in the longitudinal direction in advance, the flexibility of the steel cord will improve, and since the rubber will fit into the gaps between the cords, the adhesion between the cord and the rubber will be stronger, causing fatigue. Lifespan is also improved. Effects of the invention Since the steel cord of the invention has the above-mentioned structure, when used by covering it with a rubber material, each strand can be reliably covered with the rubber material, the twisting is stable, and the flat wire can be attached to the core strand. Its use improves fatigue resistance and reduces elongation under low loads, so it has excellent workability not only in the wire stranding process but also in the process of calendering steel cord together with rubber into sheets. ing. Furthermore, the use of flat wires reduces the number of strands and makes it easier to twist, which is an idea with great practical effects.

[Brief explanation of the drawing]

Fig. 1 is a front view of a steel cord showing one embodiment of the present invention, Fig. 2 A, B, C, D, E, and F are sectional views of the corresponding parts in Fig. 1, and Fig. 3 A, Fig. , Fig. 4 A and B, and Fig. 5 A and B are cross-sectional views of conventional steel cords, Fig. 6 shows another conventional steel cord, A is a front view, B is a - line of A,
FIG. 2 is a cross-sectional view taken along the - line, - line, and - line. 1, 7... Steel cord, 2, 3, 4... Element wire, 5... Core element wire, 6... Side element wire.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) In a steel cord composed of three strands, a core strand with a flat or oval cross section that is twisted at a certain pitch has a circular cross section on both sides. A steel cord characterized in that two side strands having substantially the same wire diameter are arranged and twisted together at the same pitch and in the same direction as the twist of the core strand. (2) Utility model registration claim 1, characterized in that the major axis of the core strand is 1.5 to 4.0 times the strand diameter of the side strand, and the minor axis is 0.75 to 1.2 times. steel cord. (3) The steel cord according to claims 1 and 2 of the utility model registration claim, wherein the core strand is pre-wavy in the longitudinal direction.