JPH0450390A - Steel cord for reinforcing rubber article - Google Patents

Abstract

PURPOSE:To obtain the subject cord having remarkably improved workability, stably twisted in longitudinal direction, having remarkably improved fatigue resistance and useful for automobile tire, etc., by twisting a straight element wire with a spirally deformed element wire. CONSTITUTION:The objective steel cord has a 1Xn structure composed of n element wires (n is 3-6) having equal diameter, wherein at least one of straight element wires 2,3 is twisted with one or plural element wires 2 having a form spirally deformed in a state to satisfy the relationships 0.1P<=P1<=0.7P (P1 is spiral pitch and P is twist pitch) and (d+2/100mm)<=d1<=(d+2/10mm) (d1 is apparent outer diameter and d is diameter of element wire).

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a steel cord for reinforcing rubber products, which is used as a rubber reinforcing material for automobile tires, conveyor belts, and the like.

[Prior art] In general, this type of steel cord has the structure shown in Fig. 4 (a) to (
D) A structure in which multiple strands of wire are closely twisted together is used, as shown in (d).

A plurality of the steel cords (5) are arranged in parallel and covered with a rubber material, and are used as reinforcing materials for rubber products such as automobile tires and conveyor belts.

By the way, when steel cord is used as a reinforcing material for rubber products, the essential requirements are firstly that it has excellent strength, but also that it chemically adheres well to the rubber material, and that there is no rubber inside the steel cord. It is also mentioned that wood often invades. That is, in order for the steel cord to sufficiently fulfill its role as a rubber reinforcing material, it is necessary that it be a complete composite with the rubber material.

However, in the above-mentioned conventional steel cord (5), since the individual wires (4) constituting the steel cord are closely twisted together, the rubber The material does not penetrate into the cavity formed in the center of the steel cord, and the cavity exists continuously along the length of the cord.

For this reason, in tires using conventional steel cords (5), the adhesion between the rubber material and the steel cord is not sufficient, causing the so-called separation phenomenon in which the steel cord and the rubber material separate when the car is running. In addition to significantly impeding the function, moisture in the rubber or moisture that has entered through the tire's cuts reaches the hollow part of the steel cord, propagates in the longitudinal direction of the cord, corrodes the steel cord, and damages the mechanical strength of the steel cord. The strength was to be drastically reduced.

In recent years, in view of the above circumstances, various steel cords having structures that can improve the adhesiveness between the steel cord and the rubber material have been proposed.

For example, in Japanese Patent Application Laid-open No. 55-90692, there is a
Steel cords (7), so-called open-stranded cords, which are twisted together with gaps C between each strand (6) as shown in A) to (D), are also used.
JP-A No. 57-193253 discloses, as shown in Fig. 7, two wire groups (8) having parallel or nearly parallel twist pitches and twisted in the same direction and pitch as the steel cord. 2 consisting of two groups of wires (9)
A steel cord (10) of +2 twist construction is disclosed.

[Problems to be Solved by the Invention] In the former steel cord (7), in order to adhere the rubber material to the entire circumference of each strand and to ensure that sufficient rubber material penetrates into the interior, each strand ( 6) It is necessary to make the gap C between them sufficient for the rubber material to penetrate, that is, 0°01 mm or more.

However, if the above-mentioned gap C is sufficiently provided, each strand (6
), the free space in which the steel cords can move becomes larger, and the twisted structure tends to become unstable during steel cord manufacturing.
As shown in (b), the strands (6) may be biased,
The twist may become uneven in the longitudinal direction of the cord. In addition, this steel cord has a large elongation under extremely low loads, so it not only has poor handling and workability during rubber molding, but also
Due to the low tension applied during rubber molding, the above-mentioned gap C is reduced, and in the end it becomes similar to the steel cord shown in Figure 4, and the rubber material does not penetrate sufficiently into the inside of the cord.
There are problems such as difficulty in improving adhesion with rubber materials.

In addition, the latter steel cord (1o) has good penetration of the rubber material and has little elongation due to tension under low loads, so the above-mentioned disadvantages of the former steel cord (7) are eliminated, but the twisted form is very unstable in the longitudinal direction of the cord. For this reason, if repeated bending stress is applied to this steel cord (1o), buckling is likely to occur, and at this time, stress concentration occurs, so that the individual wires that make up the steel cord do not exhibit any effect as a whole. , which causes fatigue failure and has a problem of poor fatigue resistance.

The present invention has been made in view of the above-mentioned problems, and it is possible to create a steel cord by applying a small spiral shape to some of the multiple wires constituting the cord, in addition to the twisting shape. By preventing the rubber material from entering the interior and by ensuring good adhesion between the rubber material and the steel cord, and by densely twisting the straight wire and the spirally curled wire, the To provide a steel cord which suppresses elongation under load, stabilizes longitudinal twisting of the steel cord, is resistant to buckling even under repeated bending stress, and has excellent fatigue resistance.

[Means for Solving the Problems] In order to achieve the above object, the steel cold for reinforcing rubber products of the present invention has a 1×n structure consisting of n wires (n = 3 to 6) of the same wire diameter. In steel cold, at least one straight strand and -<se pitch P□
When the twist pitch is P, P = O, IP ~ 0.7P
And when the apparent outer diameter d is the diameter of the wire, d□
= (d+2/100 strokes) ~ (d+2/10+m
It is made by twisting one or more strands of wire having a spiral-like habit such as +).

In the above configuration, it is preferable to have one or two spirally curled strands; if the number is too large, the elongation under low load will be large and there is a risk that the rubber material will not be able to penetrate into the inside of the cord. Furthermore, the twisting tends to become unstable.

It should be noted that if there is even a gap in the rubber material, it will penetrate through the gap and fully penetrate into the interior.

In addition, in the above configuration, the spiral habit is d□=
(d+2/10o1m) to (d+2710m) is because if it is smaller than ci+2/1100a, even if a rubber material with good fluidity is used, the rubber material will enter the inside of the steel cord during pressure vulcanization. is not sufficient, and d
This is because if it is larger than +2/10 mm, not only will the twisting stability deteriorate and the fatigue resistance will decrease, but also the elongation at extremely low loads will increase.

The wire diameter d of the wire used in the steel cord of the present invention is preferably in the range of 0.2 to 0.4 mm.

Furthermore, the twisted pitch P□ of the spiral shape is changed to
The reason for setting the value to be 0.1 to 0.7 times is because if it is smaller than 0.1 times, the curling will sometimes apply unreasonable plastic deformation to the wire, making it easier to break the wire, and if it is larger than 0.7 times. This is because the gap between the strands decreases due to the tensile force caused by the flow of the rubber material during molding of the rubber product or the squeezing force applied to the cord surface, and the rubber material does not penetrate sufficiently.

Here, the apparent outer diameter d is the apparent outer diameter of the strands curled in a spiral shape, as shown in Figure 1 (a) and Figure 2 (b), and the curl pitch means P shown in Figure 3.
l, and for the twist pitch P, P = O, IP ~ 0.
The range is 7P.

The spiral shape does not necessarily have to be an exact spiral shape, but simply a wavy shape can have the same effect as a spiral shape, so it also includes such a shape.

Embodiments of the present invention will be described below based on the drawings.

[Example 1] Figure 1 (a) is a schematic cross-sectional view of a steel cord for reinforcing rubber products according to the present invention, in which one wire (2) with a spiral curl and two wires with straightness are used. Element wire (3)
The steel cord (1) is constructed by twisting them together at a twisting pitch of P = 8 nxn.

The above-mentioned wire (2) having a spiral curl has a curl pitch P□=3.2m+, and an apparent outer diameter d=0°40m.
n, and the diameter d of each strand was Q, 28 mm.

Figures (b), (c), and (d) show that lX4X0°25, lX5X0 .2
A steel cord (1) of the present invention was formed with a twist configuration of 5.1 x 6 x 0.22, and the twist pitch P, curl pitch P□, and apparent outer diameter d as shown in the table.

[Example 2] Figure 2 (a) is a schematic cross-sectional view of a steel cord for reinforcing rubber products according to the present invention, in which two wires (2) have a spiral shape and one wire has a straightness. Element wire (3)
A steel cord (1) is constructed by twisting these together at a twisting pitch of P=8 mm.

The strands (2) having the spiral curl had a curl pitch P = 3.2 mm, an apparent outer diameter d = 0°35 mm, and the diameter d of each strand was 0.2811I11.

Figures (B), (C), and (D) show lX4X0.25, lX5X0. 25
and the twisting configuration of lX6X0.22, the twisting pitch P,
A steel cord (1) of the present invention was formed with a curved pitch P□ and an apparent outer diameter d as shown in the table.

In addition, as an example of the means for giving the strands (2) a spiral shape, by adjusting the spacing, dimensions, etc. of the combing pins provided on the wire twisting machine, or by arranging the strands in a small diameter staggered manner after that, It is easily made by passing it through a roller. It can also be easily done by inserting a single wire into a gear or the like and twisting the wire before putting it into a twisting machine. in this case,
Adjust the shape of the gear and the number of twists of the single wire.

The steel cord in this experiment was twisted into a spiral shape by using a puncher machine as a twisting machine and passing the cord through between 3 to 5 pins of a setting cone provided in front of the twist gathering point.

Furthermore, each strand (2) constituting the steel cord,
(3) Plus plating on the surface.

It is preferable to apply plating such as bronze plating to improve adhesion to the rubber material.

Next, the rubber reinforcing steel cords of Example 1.2, the conventional example, and the comparative example were evaluated for rubber material penetration, initial load elongation, fatigue resistance, and handling workability during rubber product molding. The results shown in Table 1 were obtained.

In addition, all the wires that make up each cord have a tensile strength of 30
0 kg/1lln2, and its surface is plated with plastic.

For this evaluation, the intrusibility (%) of the rubber material was determined by embedding each cord in the rubber material with a tensile load of 5 kg applied, taking out the cord after vulcanization, disassembling the cord, and cutting it to a certain length. The ratio of the length with evidence of contact with the rubber material to the observed length was expressed as a percentage.

The test was carried out in an ambient atmosphere, and the number of cycles until each cord broke was determined, and for cords with the same number of strands constituting each cord, the index was expressed as 100 for a cord with a closed strand structure. In other words, the code N011.6 of the conventional example.
The value of 13.20 was set as 100, and the code of the number of isotropic wires corresponding to them was expressed as an index.

Handling workability refers to the handling workability of steel cords during manufacturing, embedding rubber sheets, and molding rubber products such as tires. Conventional code N001.6.
13.20 was evaluated as × if it was very inferior, △ if it was slightly inferior, and O if there was no difference.

Fatigue properties were tested using a Hunter rotary bending fatigue tester, with a distance between rotational axes of 84 mm, a length between cord grips of 183 mm, a bending cuff of 5) cg/la2, and a rotation speed of 3000 cord No.
1.6.13.2o is a so-called closed twisted cord in which all the wires are in contact with each other, and has poor penetration of the rubber material.

Codes No. 62, 7, 14, and 21 all have an average shading rate (cord diameter when twisted together with gaps between each strand/cord diameter when each strand is twisted tightly together)
00) This is a 140% open-stranded cord, which is excellent in rubber material penetration and fatigue resistance, but has a large initial load elongation and poor handling workability.

Cord No. 8 is a cord with a 2+2 twist structure, which has good penetration into the rubber material but poor fatigue resistance.

Code N013.9.10.15.16.17.22.
23.24 is a cord with a twisted structure of IX3.1×4 and IX5.1×6 using wires with a spiral-like curl, and the curl pitch P□ and the apparent outer diameter d are the same as those of the present invention. The rubber material is inferior in its penetrability, fatigue resistance, and/or handling workability.

As is clear from the above comparative test, the steel cord of the present invention (Code N004.5.11.12.18.19
．． Only 25 and 26) can satisfy all of the rubber material's penetration properties, fatigue resistance, initial load elongation, and handling workability.

In the above embodiment, one or two strands having a spiral shape were used, but it is also possible to use a plurality of strands, and each strand may be a steel wire with a wire diameter of 0.2 to 0.4 mm. The same effect can be obtained by using

[Effects of the Invention] Since the steel cord for reinforcing rubber products of the present invention has the above structure, when covered with a rubber material, the rubber material easily penetrates the steel cord through the gap created between the strands (2) and (3). It is possible to penetrate into the inside of the steel cord, and each of the wires (2) and (3) constituting the coat can be reliably covered with the rubber material, and the adhesion between the rubber material and the steel cord can be reliably performed.

Furthermore, since elongation under extremely low loads is reduced, workability is greatly improved. For example, when winding a steel cord onto a reel or calendering it onto a rubber sheet, if the elongation is large under extremely low loads, the reel may become punctured or the rubber sheet may wrinkle. This will be resolved.

Furthermore, the twisting of the steel cord in the longitudinal direction is stabilized, resulting in excellent effects such as significantly improved fatigue resistance.

[Brief explanation of the drawing]

1 (a) to (d) are schematic cross-sectional views of a steel cord according to a first embodiment of the present invention, and FIGS. 2 (a) to (d) are schematic cross-sectional views of a steel cord according to a second embodiment of the present invention. Fig. 3 is a schematic side view of the steel cord shown in Fig. 2 (c), Figs. D) is a schematic cross-sectional view of a conventional twisted resteel cord, FIGS. FIG. 2 is a cutaway end view of a steel cord having a 2+2 structure. (1), (5), (7), (10)...Steel cord (2), (3), (4), (6)...Element wire (8),
(9)... Group of strands D... Cavity C... Gap

Claims (1)

[Claims] In a steel cord with a 1×n structure consisting of n wires (n = 3 to 6) of the same wire diameter, at least one wire has straightness and the twist pitch P_1 is when the twist pitch is P When P_1=0.1P to 0.7P and the apparent outer diameter d_1 is the diameter of the wire, d_1=(d+2/
A steel cord for reinforcing rubber products, which is made by twisting together one or more strands having a spiral shape of 100 mm) to (d+2/10 mm).