JPS59199888A - Metal cord and production thereof - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a metal cord used for reinforcing rubber in vehicle tires and a method for manufacturing the same.

Conventionally, metal cords used in vehicle tires have been made by twisting several strands of wire together to provide good bending resistance. An example of this is shown in FIG. Figure 1 (a), (mouth)
1 shows a cross section of a metal cord, and numeral 1 in the figure represents a wire.

Metal cords have greater tensile strength and bending rigidity than other fiber cords, so when placed inside vehicle tires, they improve wear resistance and maneuverability. However, it has been found that this metal cord also has the following drawbacks. In other words, when extreme deflection is applied to the tire, the shearing force (sliding force) directed toward the center of the tire contact patch increases, and this force causes a large compressive force to act on the metal cord, and as a result, the second As shown in Figure (A), the metal cord 2 buckles like a birdcage, resulting in extremely large bending strain, that is, A of the strand 1 in Figure 2 (B).
Tension occurs at the part B, and compression occurs at the part B, and due to this repeated action, the metal coat 2 is damaged and shattered. The destruction of a metal cord is a crack failure due to the progression of cracks on the surface of the cord, and this is caused by tensile strain. This damage causes the tire to develop a crank and destroy it. In the case of fiber cords, the buckling critical load is extremely small compared to metal cords, so the strands escape due to buckling, so large bending strains do not occur, so it can be said that there is no such drawback.

Therefore, the present invention has been made to improve the bending resistance of metal cords, and an object of the present invention is to provide a metal cord that does not have the above-mentioned drawbacks and a method for manufacturing the same. For this purpose, metal cords are made by twisting strands formed by drawing, but since initial tensile strain is given to the strands at the time of formation, we varied the state of this strain and found that a predetermined initial This was achieved based on the knowledge that resistance to local bending strain due to buckling increases in the case of a strained state.

Therefore, in the metal cord of the present invention, in a metal cord formed by twisting a plurality of strands, the portion of the strands located closer to the center of the metal cord than the initial tensile strain of the portion of the strands located closer to the center of the metal cord. It is characterized by reducing the initial tensile strain of the portion located on the outside of the metal cord facing the metal cord. In addition, the manufacturing method is a method for manufacturing a metal cord in which wires of a predetermined shape drawn from a die are twisted together, and a die having opposing asymmetrical portions is used in a direction parallel to the die axis or slightly away from the die axis. The method is characterized in that the strands are drawn in similar directions to produce opposing portions of the strands having different initial tensile strains.

Embodiments of the present invention will be described in detail below with reference to the drawings.

In the conventional metal cord, the strand 1 has a circular cross section as shown in Fig. 3 (a), and the cross section as shown in Fig. 3 (b)
As shown in the figure, the initial tensile strain of part a is equal to the initial tensile strain of part b, which is opposite to part a. On the other hand, in the present invention, as shown in FIG. 4(o)K, the initial tensile strain of section b is greater than that of section a. In the example shown in Fig. 4 (a), the cross section of the cable wire 1 is not circular as shown by the dotted line, but has a distorted shape due to the caustic line, and b
This is because the curvature of the part is narrower and the curvature of the a part is smaller. In the present invention, regarding the cable line 1 shown in FIG. 4 (A), section a is changed to section A in FIG.
Set the section to section B in Figure 2 (b). That is, the part of the strand 1 with the smallest curvature is arranged at the outermost side of the metal cord, and the part with the largest curvature is arranged at the innermost side of the metal cord. An example of this is shown in FIG. By arranging it in this way, for example, when the metal coat 2 shown in FIG. 5(a) is banked into the state shown in FIG. Because the strain is small), the total tensile force is smaller than that of conventional strands, which is advantageous in suppressing crack failure. There is no particular problem since a large compression strain is applied. Therefore, the metal cord of the present invention is significantly superior to conventional metal cords.

Ushi, in a wire with a circular cross section and a larger initial tensile strain on one side than the other, the part with the larger initial tensile strain on the innermost side of the cord has a smaller initial tensile strain on the outermost side of the cord. The parts may be twisted together so that they are arranged individually.

Generally, metal cords are used under tension or bending, but in the present invention, the same tensile strength can be maintained by making the cross-sectional area of the strands equal to that of conventional strands. When a bending moment acts on the metal cord as shown in FIG. 6(a), the metal cord of the present invention produces the following additional effects. That is, the bending moment M
Given that, the maximum bending stress σ is Iy/Z.

It is expressed as , and becomes tensile when bending and elongating, but the a of the strand is
Since the initial tensile strain is small, the total tensile stress is small, and compressive strain is applied at the bottom of the bend, so there is no particular problem. Therefore, the stress state is more relaxed than that of conventional metal cords. Here, ■ is the cross-sectional moment of inertia of the wire with respect to the y-axis shown in Figure 6 (b) (20 is the distance of the upper or lower side of the metal cord furthest from the y-axis), and・S earthwork y', and 1y/ is the moment of inertia of area passing through the center of the wire (S is the cross-sectional area of the wire, the distance between the efdy axis and the y' axis), but the cross section of the tension wire is the present invention In the case of , even if the cord diameter is equal to the conventional cord diameter, e will be large, and depending on how the curvature of parts a and b of the wire shape of the present invention is determined, , the bending stress σ becomes smaller.

In addition, if there is no need to reduce the bending stress σ, Zo
It is very flexible, i.e.
Even a metal cord with a bold cut-and-punch type as shown in Figure (B) is durable.

At the same time, the method for manufacturing the metal cord of the present invention will be explained.

In the conventional metal cord, one tension wire is immediately pulled out in the length direction, and then one wire is pulled out in the length direction, and the other is the chew method or the seventh wire as shown in Figure 7 (A).
As shown in Figure (b), it is based on the Kuncha method.

In the present invention, the method shown in FIG. 7(b) is used in order to arrange the part of the wire cross section with the smallest curvature at the outermost side of the metal cord and the part with the largest curvature at the innermost side of the metal cord.

When twisting cords, generally the drawn wires are wound up, and then the required number of wires are taken out and twisted in the twisting process.
Since the initial strain of the cord of the present invention differs within the cross section, the cord bends in the direction of part b in Figure 4 (a) after being pulled out.Using this property, the cord can be wound up and twisted immediately after being pulled out. By doing this, a metal coat with extremely uniform twisting can be obtained.

If you do not want to twist immediately, you can wind it in the curved direction and there will be no problem in the subsequent twisting process.

In order to make the metal-coated wire of the present invention, as shown in FIG. The strand 1 is pulled out in the direction (θ0).

As a result, &! 1 to produce opposing portions with different initial tensile strains. FIG. 8(1) shows an example in which the wire 11 is drawn using a die 6 in which the shape of the die drawing hole is asymmetric and the curvature of one part is smaller than the curvature of the other opposing part. Figure 8 (1) shows the cross-sectional shape of the drawing hole. Figure 8 (2), <3) shows that the shape of the die drawing hole is asymmetric, and the curvature of one part is greater than the curvature of the other opposing part. The die 3 is also small, and the longitudinal cross-sectional shape of the die is asymmetric at the die inlet and the die outlet, respectively.
This is an example of pulling out 1. Figure 8 (2) and (3') respectively show the cross-sectional shapes of the drawing holes. Figure 8 (4) shows that the shape of the die drawing hole is asymmetrical, and the curvature of one part is the same as that of the other part. This is an example in which a wire 1 is drawn in a direction inclined by 00 degrees from the die axis using a die 6 with a small curvature.The degree of inclination θ may be set as appropriate. show.

In addition, in these examples, Fig. 8 (2〃), (3
″）.

As shown in (4"), the shape of the extraction hole may be circular with the same curvature. Also, as shown in FIGS. 8(2) and (3).

(4) may be appropriately combined to make a wire.

As described above, according to the present invention, the cross section of the coat is improved by arranging the portion of the cross section of the wire with a small initial tensile strain on the outermost side of the cord, and the portion with a large initial tensile strain on the innermost side of the cord. The shape significantly improves the ease of writing codes. In a coat where the curvature of the strands is large at the innermost part of the cord and small at the outermost part of the cord, the shape stability of the cord increases, for example, when the number of strands is increased as shown in Figure 5 (c) Many chords, specifically 2+7 structure and 3+9
+15 construction cords (these often have lining wires) can eliminate the wrapping wire used to secure the shape, which is advantageous in terms of costs such as I2 fees and productivity. Become.

Hereinafter, the effects of the present invention will be specifically explained with reference to experimental examples.

The example tire size is a radial tire for a passenger car with a size of 195/70 HR14, and two N steel belts are used.

The cord has a]×5 structure, cord diameter 0.7 ++ia 1
-1- The outermost wire cross-sectional curvature is 1.33 Vynr
a, innermost curvature 13.3' Anm, strand diameter 0.2
5y+m was tested (Example).

On the other hand, the wire diameter is 0.25111 m and the cord diameter is 0.7 mm.
1× wire cross section is circular as shown in Figure 1 (A).
The test was conducted in the same manner as in the above example except that the metal cord No. 5 was used (comparative example).

The test method is air pressure 1.4 K9/i, load 1
420 per tire, 10% gravel road, 90% paved road
Of the roads in question, 3α of the paved roads are curved roads.
After driving for 10,000 km, the tires were cut and analyzed to determine the number of belt cords that were broken.

As for the number of folds, if the comparative example using the conventional cord is taken as an index of 100, the number of folds is taken as an index of 30 to 4 in the example using the cord of the present invention.
It was at 0.

As described above, according to the present invention, the cross-sectional shape of the tension wire, which is the composition of the metal cord, is changed. By making the portion small and having a large curvature, the durability of the p1 metal cord can be improved.

[Brief explanation of the drawing]

Figures 1 (a) and (b) are explanatory diagrams showing the cross section of a conventional metal cord, Figure 2 (a) is an explanatory diagram showing the bird gauge state of the metal cord, and Figure 2 (b) is an explanatory diagram showing the cross section of a conventional metal cord. The cross-sectional explanatory diagram of the dashed-dotted line part, Figures 3 (a) and (b) are explanatory diagrams showing the initial tensile strain state of the strands of the conventional metal cord, and Figures 4 (a) and (b) are An explanatory diagram showing the state of initial tensile strain of an example of a strand of a metal cord of the present invention, FIGS. Figure 6 (a). (B) is an explanatory diagram showing the case where a bending moment acts on the metal cord of the present invention, FIGS. The figure is an explanatory diagram showing an example of the method for manufacturing the metal cord of the present invention, and FIG.
1'), (2'), (2〃), (3')
, (3"). (4') and (4") are respectively shown in Figure 8 (1),
(2), (3). An example of the XX cross section in (4) is shown. 1-...Element wire, 2...Metal cord, 3...Dice. Agent Patent attorney Makoto Ogawa − Patent attorney Ken Noguchi Patent attorney Kazuhiko Saishita 5 Figure 1 (a) Figure 1 (b) (a)
(B) Figure 5 (Inquiry)
(c) (4) Figure 8 (3"') (4") Method of writing procedural amendments) 1. Indication of the case 1982 Patent Application No. 68317
No. 2, Name of the invention Metal cord and its manufacturing method 3, Relationship with the case of the person making the amendment Patent applicant 4, Agent Address: Shishi Pelican, 3-113-3 Nishi-Shinbashi, Ito-ku, Tokyo 05 "Building Ogawa/No1" inside the country's extermination permit office (
Telephone number 431 536]) 6. Target of amendment 7, Contents of amendment τ≧ (1) Page 9, line 11 of the specification, “Figure 8 (1) is” is changed to “Figure 8 (1A] is,” (2) On page 9, lines 14-15, “Figure 8...Figure 8 (2) and (3) are” is replaced with “
FIG. 8(1B) shows the cross-sectional shape of the pull-out hole. Figure 8 (2
A), (3A) is corrected as ". (3) On page 9, line 20, "Figure 8 (2'), (3')" was replaced with "Figure 8 (2B)".
), (ko). Correct “Figure 8 (4) ba,” on page 110, line 1, to “Figure 8 (4A).” (5) Page 10, line 6, “ Correct “Figure 8 (4′)” to “Figure 8 (4B)”. Page 10, lines 7-8, Figure 8<2″), (3″), (4″) D As shown. ” to “Figure 8 (2C), (3C), (
As shown in 4C), take O (7) Specification, page 10, 9~ ] 0 line ``Figure 8 (2)
, (3), (4)" to "Figure 8 (2A),
Correct (3A) and (4A). (8) On page 13, lines 7 to 9, “in Figure 8” was changed to “Figure 8 (IB), (2
B), (2C), (3B), (3C),
(4,B) and (4C) are respectively shown in Figure 8 (IA)
, (2A), (3A), (4A). (9) Figure 8 shall be corrected as shown in the attached sheet.

Claims (1)

[Claims] 1. In a metal cord formed by twisting a plurality of strands of wire, the initial tensile strain of the portion of the strands located on the center side of the metal cord is opposed to the portion of the wire that is located on the outer side of the metal cord. A metal cord characterized in that the initial tensile strain of the portion located on the outside of the metal cord is reduced. 2. Claim No. 2 characterized in that the curvature of the part of the strand of wire located on the outside of the metal cord, which is opposite to the part located on the center side of the metal cord, is smaller than the curvature of the part of the strand located on the center side of the metal cord. Metal coat according to item 1. 3 In a method for manufacturing a metal cord in which wires of a predetermined shape drawn from a die are twisted together, a die having opposing asymmetrical portions is used to twist the wires in a direction parallel to the die axis or in a direction slightly inclined from the die axis. 1. A method for manufacturing a metal cord, the method comprising: drawing out a wire to produce opposing portions having different initial tensile strains.