JPH06346386A - Metallic cord for reinforcing rubber article - Google Patents

Abstract

PURPOSE:To obtain a metallic cord for reinforcing a rubber article capable of enhancing the flexural rigidity after compounding thereof with rubber and thereby reducing both the number of cords used and the weight of the rubber article while satisfying conventional prescribed properties. CONSTITUTION:This metallic cord is obtained by laying (n) [(n) is 5 in the figure] metallic filaments having 0.20-0.28mm diameter (d) at a constant pitch within the range of 10-18mm, respectively distributing the metallic filaments 1-1, 1-3 and 1-5 at positions capable of drawing the first inscribed circle (D1) and further the metallic filaments 1-1, 1-2 and 1-4 at positions capable of drawing the second inscribed circle (D2) and making the average diameter (Dim) of the inscribed circles (D1) and (D2) satisfy the following formula: 3.1(d){sin<-1>pi/[(n)-1]}<=dim<=7.0(d){sin<-1>pi/[(n)-1]}. Thereby, a prismatic space continuous in the longitudinal direction is produced in the interior of the cord and the resultant part is embedded in a rubber to improve the flexural rigidity after compounding the cord with the rubber.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal cord for reinforcing rubber articles such as automobile tires, conveyor belts and high pressure hoses, and particularly to a structure effective for reinforcing rubber articles for which rigidity and weight reduction are desired. For metal cords with.

[0002]

2. Description of the Related Art For metal cords used to reinforce radial tires for automobiles, adhesion to rubber, adhesion durability, corrosion resistance and various mechanical performances of the cord (cutting load, bending rigidity, fatigue resistance, In addition to the conventionally required characteristics such as flexibility, there is a new demand for weight reduction without significantly impairing these characteristics.

A metal cord for the purpose of weight reduction is 1 × 5
Alternatively, a parallel 2 + 2 twist structure, a 1 × 2 twist structure through a parallel 2 + 1 twist structure, and a 1 × 2 twist structure are often used. For example, JP-A-62-234921 discloses
Proposal of compact cords of 1 × 2 × 0.28 and 1 × 2 × 0.30 in which the total number is reduced to two by using high strength and diameter-increasing metal filaments with a carbon content ratio increased to 0.82 wt%. In addition, Japanese Patent Laid-Open No. 2-229286
The publication proposes a 1 × 2 × 0.30 local open code with improved corrosion resistance.

Further, Japanese Patent Laid-Open No. 3-76881 also discloses
Weight reduction is not the main purpose, but the filament strength is increased to 400 kgf / mm ² or more without reducing the number of strands to reduce the diameter, and the filament is 125% or more so that the flatness is about 80%. By molding in a flat spiral shape with an average mold ratio, the out-of-plane bending rigidity of the reinforced rubber article is reduced to improve flexibility and mechanical durability, while maintaining the in-plane bending rigidity. We propose an open cord with a twisted structure of 1 × 5 × 0.18 (or 0.20) that improves ride comfort and maneuverability.

[0005]

SUMMARY OF THE INVENTION 1 × 2 × 0.3 described above
0 (or 0.28) compact cords and local open cords have a large change in bending rigidity due to the irregular longitudinal cross section at each part in the longitudinal direction, and also because of the relatively large diameter,
Repeated application of bending stress causes premature rupture of the cord, and is therefore not particularly suitable for reinforcing heavy vehicle tires.

The 1 × 5 flat open cord is
Since the longitudinal cross section is an ellipse, the out-of-plane bending rigidity can be reduced if the ellipses of the ellipse can be aligned stably in the in-plane direction when the cords are aligned. Due to the residual stress and the residual torsion, the directions of the elliptical ellipses are not aligned, and eventually, the same defects as those of the cord having the 1 × 2 twist structure occur.

Further, in the technique disclosed in Japanese Patent Laid-Open No. 3-76881, a tubular type twisting machine is used in which "a twist does not occur in a wire. Double twist type buncher twisting machine uses a wire. It is not preferable because it twists and breaks. "
From the description above, it is considered that the twisting value decreases, and it is doubtful to put such a metal cord in which strands are twisted together for practical use. In addition, it is not preferable to use a buncher type twisting machine in view of manufacturing cost.

Therefore, according to the present invention, the effect of improving the bending rigidity by the rubber to be reinforced is reduced so that the amount of cords used is reduced accordingly, whereby the weight can be reduced without sacrificing the various required characteristics. An object of the present invention is to provide a metal cord for reinforcing a rubber article as described above.

[0009]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides an n (3 having a diameter of 0.20 to 0.28 mm.
≦ n ≦ 6) The metal filaments were twisted together at a constant twist pitch defined in the range of 10 to 18 mm.

Further, in each of the metal filaments, the average diameter Dim of the first and second inscribed circles drawn by the first group of metal filaments and the second group of metal filaments in the cross section perpendicular to the longitudinal direction of the cord satisfies the following expression. Distributed in position.

3.1d (sin ⁻¹ π / n−1) ≦ Dim
≦ 7.0 d (sin ⁻¹ π / n−1) where d: diameter of metal filaments forming metal cord n: total number of metal filaments forming metal cord Note that the first group and the second group of metal filaments Are three or more, and at least one of them belongs to both the first and second groups and one of the metal filaments of the same group which is located at a position opposite to the other metal filaments. Included one. Further, the average diameter Dim of the inscribed circle is maintained at each part in the longitudinal direction of the cord, and a space of polygonal columns continuous in the longitudinal direction is generated inside the cord.

The metal cord preferably has an elongation (LLE) under a load of 0 to 5 kg within 0.90 to 1.6%.

[0013]

The metal cord of the present invention is a so-called open cord. As the prior art of this open code, those shown in FIGS. 3 (a) to 3 (h) are disclosed in JP-A-55-9069.
No. 2, Jitsuko Sho 48-48392, Japanese Examined Patent Publication 1-1563
No. 2, JP-B-4-3474 and JP-B-4-50427
Proposed in the issue. These codes are all 3
A gap is created between each filament in order to facilitate rubber penetration into the internal space that occurs when two or more metal filaments are twisted into a single twist structure. Expressed as a rate, 1
It is about 05 to 165%. However, when the degree of openness is about this level, the cord is crushed by the mold vulcanization pressure of the rubber when it is compounded with the rubber, so that the rubber cannot be sufficiently filled into the internal space.

The inventor pays attention to the inner space of the open cord, that is, the inner region of the inscribed circle drawn by the distribution of three or more metal filaments, and if this portion is completely filled with the filler, it becomes a composite with rubber. Later, we thought that the bending rigidity could be improved by the filling material inside, and the cord usage could be reduced accordingly.

It was also considered to insert nylon, polyester or rubber having a small specific gravity in the twisted wire stage for the complete filling, but this is technically difficult and unreasonable, so it is reinforced. The study proceeded on the assumption that rubber will be infiltrated.

Generally, the diameter of the inscribed circle becomes smaller in the order of 1 × 5, 1 × 4, 1 × 3 if the cord diameters are the same, that is, as the structure is simplified, and it becomes The rubber permeability of the same also becomes better as the structure is simplified. In this respect, when the rubber to be reinforced is infiltrated to fill the internal space, a twisted structure of 1 × 5 or the like, which has a large number of twists, seems to be disadvantageous at first glance. However, considering fatigue resistance against repeated bending, it is important to keep the filament diameter thin by increasing the number of twists.

Therefore, after further study, the type ratio of each filament was increased to 165% or more, which is the conventional upper limit,
If the average diameter of one or two inscribed circles that can be drawn from the distribution of three or more filaments is set to 3.1 times or more the inscribed circle diameter {d (sin ^-1 π / n-1)} in the case of a compact cord. It was found that a space of polygonal columns continuous in the longitudinal direction of the cord can be easily created regardless of the number of twists.

As described above, the cord of the present invention produces a polygonal column space continuous in the longitudinal direction inside by making the type ratio of the filament so large that it is generally disliked. By ensuring a sufficient gap, the rubber is completely filled and the bending rigidity is improved by the filled rubber. This makes it possible to reduce the amount of cords used and achieve the purpose of weight reduction.

The polygonal space mentioned here has a cross section drawn by connecting the contact points of each metal filament and the inscribed circle, and the cross section extends in the cord longitudinal direction while being twisted at the same pitch as the twist pitch. It is what

The reasons for limiting numerical values will be described below.

First, regarding the number n of twisted metal filaments, the target cord is an open cord excluding a 1 × 2 cord that is not suitable for heavy vehicle tires, so the lower limit is 3. On the other hand, when n is 7 or more, the filament easily falls into the space generated at the center of the cord,
The upper limit of n was set to 6 which can be twisted in a single twist structure without causing a drop.

If the upper limit of the diameter of the metal filament used is 0.28 mm,
To prevent early fracture due to repeated bending in heavy vehicle tires, the lower limit is that if the filament diameter is too small, the bending rigidity will decrease, and the effect of improving the bending rigidity by the filled rubber will not be able to compensate for the decrease. It is necessary to increase the number, and this hinders the realization of weight reduction.

Further, if the twisting pitch exceeds 18 mm, it becomes less like a cord and the flexibility and fatigue resistance are deteriorated. On the other hand, if the twisting pitch is less than 10 mm, the bending rigidity is insufficient and the productivity is low. Considering the difficulty of stranded wire with a high buncher type stranded wire machine, 10
It was set in the range of up to 18 mm. Among them, the practical value is 12 to 1
It is 5 mm.

Regarding the average diameter Dim of the inscribed circle,
The reason for limiting the inscribed circle of the compact cord to 3.1 to 7.0 times is that the apparent cord diameter increases at 7.0 times or more, so the adjacent cords when the embedding pitch in the rubber is regulated. It becomes difficult to secure the gap required in the design between them, while if it is less than 3.1 times, a space that leads to improvement of bending rigidity in the cord, that is, a polygonal column space that can be filled with rubber is stably and continuously created. This is because it is difficult to do.

The quality inspection of the completed metal cord is
It is more advantageous to measure the elongation under load of 0 to 5 kg (LLE) than to measure the average diameter of the inscribed circle.
L. L. E has been verified that it can be used for quality evaluation as a substitute characteristic, and unlike the measurement of the average diameter of the inscribed circle, the test can be performed without much time. The L.D. equivalent to the average diameter Dim in the range limited in the present invention. L. The range of E is about 0.90 to 1.6% in consideration of the twist pitch.

[0026]

【Example】

-Example 1-Five brass-plated metal filaments having a diameter of 0.23 mm were overmolded (molded), and then twisted together with a twist pitch of 14 mm, and the cross-sectional shape shown in FIG. Two
3 excessive open code 10 (EOC) was obtained. In the figure, D ₁ is the first group of three metal filaments 1 _-1 , 1 _-3 , 1
_-5 is an inscribed circle drawn by _-5 , D ₂ is a _second inscribed circle drawn by three metal filaments 1 _-1 , 1 _-2 , 1 _-4 of the second group, and here, the average diameters of the two are 0.58 mm (5
This is 3.6 times that of the fully twisted compact cord. When the contact points of each metal filament and the inscribed circle are connected by a straight line, a space with a pentagonal cross section with hatching appears inside the cord. This space is twisted at the same pitch as the cord pitch and extends in the longitudinal direction of the cord.

Example 2 Four brass-plated metal filaments having a diameter of 0.25 mm were overmolded and then twisted at a twist pitch of 14 mm to form a cross section of 1 × 4 × 0. 25 oversized open code 10 (EOC) was obtained.

The metal filament of this cord is 1 _-1 ,
1 _-2 , 1 _{-4 contact} the first inscribed circle D ₁ and 1 _-1 , 1 _-3 , 1 _-4
Are distributed at positions contacting the second inscribed circle D ₂ . First,
The average diameter of the second inscribed circle is 0.41 mm (4.0 times that of a 4-strand compact cord), and a space with a square cross section is formed inside the cord.

Example 3-Three brass-plated metal filaments having a diameter of 0.28 mm were overmolded and then twisted at a twist pitch of 14 mm, and the cross-sectional shape of 1 × 3 × 0. 28 oversized open code (EOC) was obtained. This code
Since there are three twists, only one inscribed circle D can be drawn. Here, the diameter of the inscribed circle D was set to 0.29 mm (6.7 times that of a three-strand compact cord).

-Comparative Examples- As comparative codes, the codes of Comparative Examples 1 to 6 were prepared. This comparative example includes three types of compact cords (C.C.) having a cross-sectional shape shown in Fig. 2 and open cords (O.C.) of five strands shown in Fig. 3A. The twist pitch of each comparative cord was 14 mm. Also, the metal filament type coverage of O and C was set to 165% or less.

For each of the above samples, the rubber filling rate of the space inside the cord (average diameter of the inscribed circle) and L. L. E (elongation in low load range) and bending rigidity were investigated. The results are shown in Table 1.

[0032]

[Table 1]

As can be seen from Table 1, Examples 1, 2 and
No. 3 has a higher rubber filling rate in the internal space than the comparative examples, and despite having the same number of metal filaments of the same diameter twisted together, the bending rigidity after compounding with rubber is higher than that of the comparative example. It is getting bigger.

[0034]

As described above, according to the metal cord of the present invention, the inner space of the open cord and the gap between the metal filaments are positively expanded within a range where the apparent cord diameter does not become excessively large and the rubber is filled in the cord. The ratio and the amount of filling are increased, and the filling rubber is used to increase the bending rigidity after compounding with rubber, so the number of cords used is reduced and the conventional required characteristics are satisfied, while the weight of the reinforced rubber article is light. Can be realized.

[Brief description of drawings]

FIG. 1 (a), (b), (c) are all sectional views showing a metal cord of the present invention.

2A, 2B, and 2C are cross-sectional views of conventional compact cords.

3A to 3H are sectional views of conventional open cords.

[Explanation of symbols]

1, 1 _-1 to 1 _-5 Metal filament 10 Metal filament D ₁ 1st inscribed circle D ₂ 2nd inscribed circle D 3 Inscribed circle that can be drawn with a twisted cord

Claims (2)

[Claims] 1. An n (3 ≦ 3 having a diameter of 0.20 to 0.28 mm.
n ≦ 6) metal filaments are twisted together at a constant twist pitch defined in the range of 10 to 18 mm, and each metal filament has a first group of metal filaments and a second group of metal filaments in a cross section perpendicular to the longitudinal direction of the cord. The average diameter Dim of the first and second inscribed circles that can be drawn by the metal filament is distributed in a position satisfying the following formula, and 3.1d (sin ⁻¹ π / n−1) ≦ Dim ≦ 7.0d
(Sin ⁻¹ π / n−1) where d: the diameter of the metal filaments that form the metal cord n: the total number of metal filaments that form the metal cord, and the metal filaments of the first group and the second group are both 3 or more. And each of them includes at least one that belongs to both the first and second groups, and one that is in a position facing each other in the same group of metal filaments, A metal cord for reinforcing a rubber article, wherein the average diameter Dim of the inscribed circle is maintained at each portion in the longitudinal direction of the cord, and a space of polygonal columns continuous in the longitudinal direction is generated inside the cord. 2. The elongation under load of 0 to 5 kg is 0.90.
The metal cord for reinforcing a rubber article according to claim 1, wherein the content is 1.6%.