JPS604312B2 - Steel cord for reinforcement - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to reinforcing steel cords, particularly steel cords used for reinforcing car tires and rubber or plastic products.

Traditionally, thin strands of wire are used to reinforce the carcass of radial tyres, chafers, etc. for automobiles such as trucks and buses.
Normally, 3 side strands are twisted together around a core strand, which is made up of a plurality of strands twisted together.
Steel cords with a twisted structure (lobed type) having a large number of strands, such as 8 (lx35x7) to 2$ (7x4), are used. This is because, for example, when reinforcing a case, it is required to have high shear strength and high flexibility because it is constantly subjected to high air pressure and is repeatedly bent and deformed by driving the car. If you observe the cord after long distance running when using a steel cord with a conventional structure, you will notice fretting caused by the friction between the wires that make up the cord.
A large number of fretting habits are observed, and fatigue fractures are very often caused by these fretting habits.

The cause of this fretting rudder is mainly that the core strands and the side strands constituting the twisted wires cross and contact each other, forming a point contact. The present invention solves the above-mentioned drawbacks by configuring the steel cord so that the core strand and side strand tie wires are in line contact, thereby increasing fatigue resistance without causing the above-mentioned fretting eaves during use. It is an object of the present invention to provide a steel cord that is durable, has a small decrease in breaking strength due to twisting, can have a small outer diameter with the same cross-sectional area, and has a core strand that provides a reliable bond.

In the present invention, in a twisted wire, the directions of twisting the outer layers of the core strand and the side strands are opposite to each other, and the direction of gathering and combining of the plurality of side strands is the same as the twisting direction of the outer layer of the core strand. The number of strands in the outer layer of the core strand is the same as the number of strands in the side strand, and the number of strands in the outer layer of the core strand is always in line contact with each strand in the outer layer of the side strand. The reinforcing steel cord is characterized in that the twisting pitch of each outer layer constituting the strand and the side strand and the collective twisting pitch are selected.

As the wire used in the present invention, a special steel wire such as iron, steel, or stainless steel is used. In the present invention, the number of strands constituting each of the core strand and side strand is usually 3.
~7 pieces, but not limited to these.

In addition to the above-mentioned self-stranded wires, the steel cord of the present invention may also include, if necessary, a wire wrapped in a spiral shape around the above-mentioned twisted wires. In the present invention, the twisting directions of the outer layers of the core strand and the side strands are opposite to each other, and the collective twisting direction of the side strands is the same as the twisting direction of the outer layer of the core strand. The portion of the wire that contacts the core strand is in an approximate direction close to the line tangent side.

This idea is based on concentric ropes.
ire strand core (IWSC)) and rope core (IWSC) and rope core (IWSC)
pecore (IWRC), etc., but in the present invention, the number of strands and the twisting pitch are taken into consideration, so that the core, sides, and both strands are always parallel, that is, line contact is achieved. It is characterized by having a relationship. Hereinafter, the present invention will be explained using the drawings.

Fig. 1 is a cross-sectional view showing an embodiment of the present invention, in which strands of the same diameter are used throughout, and six four-strand side strands are twisted together around a seven-strand core strand. be.

In this case, the outer layer of the core strand is Z-twisted, the layer of side strands is S-twisted, and the collective twisting direction of the side strands is Z-twisted.
Furthermore, by appropriately selecting each twist pitch, Fig. 1A
At a certain position, as shown in FIG. As the pile of strands of strands falls down, the strands of core strand 1 and side strands 2 synchronize and interlock with each other.

The formula showing the relationship between each twisting pitch to satisfy the requirements between these strands is derived as follows. The number of twists in the outer layer of the core strand is m, and the number of twists in the outer layer of the side strands is n.
, the collective twisting pitch of the twisted wires is A, the twisting pitch of the outer layer of the side strand is B, and the twisting pitch of the outer layer of the core strand is C.

In order to satisfy the above requirements, each of the core strand and side strands is considered to be a solid round wire, and when the bran antennae are set to 8, the contact line between the two becomes m spiral curves on the outer periphery of the core strand. exist.

If the number of peaks (or valleys) of the strands constituting each of the two strands on the contact line is the same, the above-mentioned interlocking should be possible. Let's think about the unit length of steel cord using this idea.

The side strands circulate around the core strand 〆′A times.

The number of peaks (or troughs) of the core strands on this contact spiral is equal to the number of peaks (or troughs) because the direction of gathering and burning and the direction of twisting the outer layer of the core strands are the same. Also, the number of peaks (or valleys) on the spiral wire that contacts the core strand of the side strand is 8 times because the outer layer twisting direction and the collective twisting direction of the side strand are opposite to each other. . Therefore, in order for the two to be the same, the sketch = Nabeori. Layer Core Homo D
(Twice the distance of the straight line connecting the center point of the core strand circumscribed circle and the center of the side strand circumscribed circle) tan8=
Since this is the Usaran ratio, in order to determine each twisting pitch used in the present invention from the formula {1}, after determining any two pitches among the twisting pitches A, B, and C, use the other one using the formula m. All you need to do is decide on one pitch.

In addition, in the present invention, in order to select the outer diameter of each strand, the number of strands, and the diameter of the strands, appropriate dimensions are determined geometrically in the same way as for ordinary twisted wires, and the outer diameter of the core strand is determined from the theoretical value. It is desirable to increase the size by about 0 to 5%.

That is, in the present invention, the ridges (valleys) of the strands of the core strand engage with the troughs (peaks) of the strands of the side strands, so even if the conventional twisting method creates gaps in the outer layer due to collective twisting, it is difficult to create gaps. It can be twisted tightly without any formation.

Therefore, the filling rate as a twisted wire is high. 3 shown in FIGS. 1A and 1B is a wire wrapped in a spiral shape on the twisted wire.
Next, examples of the present invention will be described.

Example 1: A steel cord according to the present invention having the following configuration was created.

core. (Rugo Hou)<.

・75 side 10th place (no window) X0-175 side 11x0
This is as shown in Figure 1, which corresponds to m = 6 and n = 4 in the Kawa method. A steel cord of the present invention was produced.

. There is wrapping on the surface of each stranded wire, and I created it with great care. Table 1 Among these, No. No. 5 is a steel cord in which six side strands are attached vertically around a core strand without being twisted together, wrapped in a spiral shape with a line of 0.15 ribs 8, and bundled.

In this case, (area is fort=n&OS8(COS8i1).

In all of the cases shown above, the strands of the outer layer of the core strand and the strands of the side strands always showed good wire contact. No. The result of measuring the breaking strength of 1 is 202k9
This represented 95.1% of the total breaking strength of the strands.

A steel cord of 31 twists in which all the wires have the same diameter as in this embodiment has the advantage of being easy to manufacture, having high breaking strength, and high fatigue strength because there is no risk of mixing of wires.
In this case, selecting a pitch like {1} = 12 connections. Figure 1C is Table 1, No. For example 1, a situation in which the cross section changes in the length direction of the cord is illustrated.

A shows one side strand before the cord is twisted, the mouth shows the state in which one side strand is twisted on top of the core strand, and C shows a cross-sectional view at each layer.

One of the side strands shown in the opening is shown as a thick line, and one of the strands in the side strand and one of the strands in the core strand are painted black in C. Table 2 shows the changes in the angle of rotation and revolution at the position of each strand in C. Table 2 In addition, the tree in Figure 1 C shows the pitch of the core strand C side strand B and the collective twist A, where C is the Z twist,
B is S twist, and A is Z twist.

Fig. 3 shows the state of contact between the core strand and the side strands (only one strand is shown in the figure) by further disassembling C in Fig.
c, d indicate side strands. Core strand green 01
It can be seen that the twill contact state of 1 and the side strands a to d changes depending on the revolution angle of each side strand. Comparing the above relationships, it should be understood that the twist pitch is selected so that the core strands and side strands mesh with each other like gears, while the strands always maintain line contact with each other.

Example 2: A steel cord according to the present invention having the following configuration was created.

□Strand Side strand wrapping 0ri 12 side mesh (lx5 main combustion) xo. 17 Willow Ten (5 x 4 strands) xo.

19 willow ten lxo. The cross section of this steel cord made of No. 15 willow is as shown in FIG. 2, and the same reference numerals as in FIG. 1 indicate the same parts.

In this example, m=5 and n=4, so {1}
The formula was equal to 4 melons, 80 gourds, and each twist pitch was selected using this formula.

. Also in this case, as in Example 1, good line contact was always obtained between each strand.

As described above, in the steel cord of the present invention, the number of strands, the twisting direction, and the twisting pitch are selected so that each strand of the outer layer of the core strand and the outer layer of the side strand are always in line contact. Therefore, it has the following advantages.

(A) There is little decrease in the breaking strength of the steel cord due to twisting, and a breaking strength close to the total breaking strength of the strands can be obtained.

In other words, in the case of conventional steel cord, the above total of 90~
93%, while the steel cord of the present invention has a
It is 5-98%. (o) Due to the repeated bending of the steel cord during use, since the wires are in line contact, fretting is less likely to occur, and even if fretting occurs, there is little cross-sectional reduction due to wear of the wires, so the fatigue of the steel cord is reduced. Strength increases and fatigue limit improves.Since the core strand and side strands are well interlocked, there is no misalignment between the core strand and side strands at the cut surface.

Also, a reliable bond with the rubber can be obtained up to the core strand.

〇 A large cross-sectional area can be obtained for the same outer diameter of the steel cord. That is, since the filling rate is high, it is advantageous when there is a limit to the number of impressions per tire, such as in automobile tires.
■ Even if the pitch of the collective twists is made large, the steel cords are well organized, and especially when wrapping is used, a structure without collective twists is possible, which reduces costs.

[Brief explanation of the drawing]

FIGS. 1A, B, and C and FIG. 2 are sectional views showing embodiments of the steel cord of the present invention, respectively. Figure 3 shows the contact of the strands between the core strand and the side strands,
This is a partial cross-sectional area showing changes in combustion conditions. 1...
Core strand, 2...side strand, 3...wrapping line,
A... Cord twist pitch, B... Side strand pitch, C... Core strand pitch, 11, 12, 13, 14
, 15 (16... core strand, strands a, b, c, d... side strand strands.

Claims (1)

[Claims] 1. In a twisted wire formed by collectively twisting m side strands having an outer layer around a core strand having m outer layers, the twisting direction of the outer layer of the core strand is Z
twist (or S twist), the twist direction of the outer layer of the above side strand is S
(or Z twist), the direction of the collective twist is Z twist (or S twist), and the twist pitch C of the outer layer of the core strand, the twist pitch B of the outer layer of the side strands, and the collective twist pitch. A and m/c=n/(BCOS+)+
(n+mcosθ)/(ACOSθ) (θ represents the twist angle formed by the core strand and the side strands.) By selecting the respective pitches so as to have the following relationship, each strand of the outer layer of the core strand and the above A reinforcing steel cord characterized in that the side strands are configured so that they are always in line contact with the outer layer strands.