JPH0921083A - Steel cord for radial tire and its production - Google Patents

Abstract

PURPOSE: To obtain a steel cord for radial tire, having durability without causing increase in weight and lowering of rigidity by twisting plural side filaments in same direction and pitch as core filaments round plural core filaments. CONSTITUTION: Five side filaments 3 comprising wire rods having thick diameter with 0.80-0.90% carbon content are twisted in mutually adjacent intervals G round core filaments 2 comprising two wire rods having fine diameter twisted while keeping mutually adjacent interval S and an elastic material 4 such as a rubber is sealed into the adjacent interval S between these core filaments 2 and the adjacent interval G between the side filaments 3 without space to provide the objective steel cord for radial tire having flat cross section, having 0.085-0.110 estimated value of rigidity obtained from total of diameter of whole filament and 0.55-0.65 total cross section of whole filament.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel cord for radial tires and a method for manufacturing the same.

[0002]

2. Description of the Related Art As a steel cord used in a belt layer of a radial tire, as shown in FIG. 4, three small diameter filaments 20 are twisted together to form a core, and six large diameter filaments 21 are formed around the core. What has a so-called 3 + 6 structure, in which the reverse twist is applied to surround it, is the mainstream. Between the adjacent large filaments 21,
A rubber 22 is enclosed between the large diameter filament 21 and the small diameter filament 20.

[0003]

In the steel cord having the above structure, the center of the core (between the thin filaments 20) is used.
A triangular prism-shaped gap 23 that is sealed along its longitudinal direction
However, there was a case where the rubber 22 could not be enclosed in the closed gap 23. Therefore, in the unlikely event that the steel cord is damaged from the outside to the center of the core, water will enter into the sealed gap 23 through the damage, and therefore, along the longitudinal direction of the steel cord. This leads to the generation of rust, and in some cases, this rust leads to the drawback of causing separation.

Incidentally, in the past, a steel cord using only the large-diameter filament 21 has been developed (see JP-A-3-96404 and JP-A-6-65877). In many of these steel cords, the number of the large-diameter filaments 21 used is extremely reduced (for example, 4) and the rubber sealing port between the filaments is increased, or conversely, increased (for example, 7). (More than this) The flatness of the cross section of the cord is increased, so that at least 1
It is designed to secure the rubber sealing port at some places.

However, such a large-diameter filament 2
The increase / decrease in the number of cords in No. 1 directly leads to an increase in the cord weight, a decrease in the cord rigidity, a deterioration in the riding comfort of a tire using this steel cord, and the like, and it was difficult to balance them. . Further, in some cases, the production of the steel cord may be troublesome and difficult.

The present invention has been made in view of the above circumstances. In addition to an increase in the weight of the cord and a reduction in the rigidity of the cord, the riding comfort is deteriorated and the performance of the tire using the steel cord is degraded. It is an object of the present invention to provide a steel cord for a radial tire and a method for manufacturing the same, which can improve the durability of the elastic material such as rubber without increasing the durability of the elastic material such as prevention of rust. .

[0007]

According to the present invention, the following technical measures have been taken in order to achieve the above object. That is, in the steel cord for radial tires according to the present invention, two core filaments that are twisted at an adjacent interval to each other and five side filaments that are twisted at an adjacent interval to each other around these core filaments are twisted. And has a flat cross section with the elastic material enclosed between the adjacent core filaments and between the adjacent side filaments.

The twist of the core filament and the twist of the side filament can be in the same direction and at the same pitch. At least the side filaments having a carbon content of 0.80% or more and 0.90% or less are used, and the rigidity standard value obtained as the total diameter of all filaments is set to 0.085 or more and 0.110 or less. ,
It is preferable that the total cross-sectional area of all filaments is 0.55 or more and 0.65 or less.

On the other hand, in the method for manufacturing a steel cord for a radial tire according to the present invention, the virtual longitudinal isosceles triangle 3
Place one side filament on each corner,
The core filaments are arranged one by one in correspondence with the two long side portions of the above-described vertically-long isosceles triangle, and further, two side filaments remaining on the outer sides of these core filaments are arranged one by one, and then the above-mentioned 2 The core filaments of this book are positioned so that their respective centers are outside the two long side portions of the above-described vertically-long isosceles triangle, and all core filaments and side filaments are twisted together in the same direction and at the same pitch, After that, while applying a reduction in the direction of crushing the height direction of the above-mentioned vertically elongated isosceles triangle, the elastic material is enclosed between the adjacent core filaments and the adjacent side filaments to form a flat cross section. I am trying.

[0010]

The steel cord according to the present invention has two core filaments (corresponding to conventional thin filaments).
And 5 side filaments surrounding these core filaments (corresponding to conventional thick filaments) have a 2 + 5 structure. Since a predetermined interval is maintained between the adjacent core filaments and between the adjacent side filaments, a structure in which an elastic material is securely enclosed in this portion (that is, there is no closed gap) is provided. Has become. As a result, the generation of rust along the longitudinal direction can be prevented as much as possible.

As described above, since the side filaments are not used alone but the core filaments are combined, there is no possibility of causing an increase in cord weight or a decrease in cord rigidity. Since the core filament and the side filament are twisted in the same direction and at the same pitch,
Predetermined spacing maintained between adjacent core filaments and adjacent side filaments (encapsulation of elastic material)
Is continuously formed along the longitudinal direction of the steel cord. Therefore, this is also useful for enhancing the encapsulation property of the elastic material.

For the side filaments having a large occupation rate, it is preferable to use one having a carbon content of 0.80% or more and 0.90% or less in order to obtain a tough and light steel cord. Of course, it is preferable to use the same core filament. In addition, the rigidity standard value (nd ⁴ + ND ⁴ where the diameter of the core filament is d, the diameter of the side filament is D, and the number of each filament used is n, N) obtained from the total diameter of all filaments is 0.085 or more. When it is 0.110 or less, rigidity, abrasion resistance, steering stability, riding comfort, etc. are preferably maintained, and separation is prevented.

The total cross-sectional area of all filaments (n (1 / 2d) ² where d is the diameter of the core filament, D is the diameter of the side filament, and n and N are the number of filaments used)
When π + N (1 / 2D) ² π) is set to 0.55 or more and 0.65 or less, it is useful in increasing rigidity and reducing weight.
On the other hand, in the method for manufacturing a steel cord for radial tires according to the present invention, the core filaments and the side filaments arranged in a predetermined positional relationship are twisted together in the same direction and at the same pitch, and then compressed between filaments. Since the elastic material is enclosed between the core filaments and between the side filaments, it is possible to manufacture a steel cord with a flat cross section in which the elastic material is enclosed without a gap. Easy and reliable.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of a steel cord 1 according to the present invention, which is shown as being used for a radial tire (TBR) for trucks and buses. The steel cord 1 is formed in a flat shape such as an ellipse in its cross-sectional shape, and has two core filaments 2 and a surrounding portion 5
The side filament 3 of the book constitutes a 2 + 5 structure.

Predetermined intervals S and G are held between the core filaments 2 and the side filaments 3 adjacent to each other. Without elastic material 4 such as rubber
Is enclosed. And these core filaments 2
The side filament 3 and the side filament 3 are twisted in the same direction and at the same pitch. Therefore, the contact portion between the core filament 2 and the side filament 3 and the space between them (the enclosed portion of the elastic material 4) are continuous in the longitudinal direction of the steel cord 1.

A small diameter wire is used for the core filament 2 and a large diameter wire is used for the side filament 3. Each of the wires has a higher carbon content than before (0.75 in the prior art). % Or less is normal) 0.80% or more 0.9
Those of 0% or less are used. Therefore, it is suitable for obtaining a tough and light steel cord. The diameters of the core filament 2 and the side filaments 3 are in a relationship satisfying the following two conditions.

The first condition is that the rigidity reference value (the diameter of the core filament 2 is d, the diameter of the side filament 3 is D, and the number of filaments used is n and N respectively) obtained from the total diameter of the filaments. The value obtained by nd ⁴ + ND ⁴ ) is 0.085 or more and 0.110 or less. If the rigidity reference value is less than 0.085, the rigidity may be poor, and the abrasion resistance and the steering stability as a tire may be poor. If it exceeds 0.110, not only the riding comfort of the tire may be deteriorated, but also separation may easily occur at the belt edge portion during traveling.

The second condition is that the total cross-sectional area of each filament (the diameter of the core filament 2 is d, the side filament 3 is
Where D is the diameter of N and N and N are the numbers used, the value obtained by n (1 / 2d) ² π + N (1 / 2D) ² π is 0.55 or more and 0.65 or less. There is a point in doing so. If this total cross-sectional area is less than 0.55,
Even if the above-mentioned rigidity standard value is set to 0.085 or more, the predicted rigidity cannot be satisfied. Also 0.
If it exceeds 65, there is a disadvantage in weight reduction.

FIG. 2 schematically shows the manufacturing state of the steel cord 1. In this manufacturing method, the wire for the core filament 2 and the wire for the side filament 3 are unwound to the guide portion 6. Then, the filaments 2 and 3 are arranged in a predetermined manner as shown in FIG. In this case, three of the side filaments 3 are arranged at the three corners of the virtual vertically long isosceles triangle T. Then, one core filament 2 is arranged corresponding to each of the two long side portions t1 and t2 of the vertically long isosceles triangle T, and two side filaments 3 remaining outside each of the core filaments 2 are arranged.

In the core filament 2, each center P thereof has two long side portions t in the vertically long isosceles triangle T.
It should be positioned so as to be outside of 1 and t2.
Then, as shown in FIG. 2, in the twisting portion 7 provided on the downstream side of the guide portion 6, all the core filaments 2 and the side filaments 3 are twisted together in the same direction and at the same pitch.

Next, in the pressure-reducing section 8 provided on the downstream side of the twisted section 7, a reduction is applied in the direction of crushing the height direction (see h dimension in FIG. 3) of the vertically-long isosceles triangle T. Of course, the rolling may be applied also in the direction orthogonal to this. Even under such a rolling condition, initially, each center P of the core filament 2 is equal to 2 of the above-described vertically-long isosceles triangle T.
Since the outer side is longer than the long side portions t1 and t2, the side filament 3 positioned at the apex angle position (the uppermost position in FIG. 3) of the vertically elongated isosceles triangle T is inserted between the core filaments 2 adjacent to each other. Therefore, both core filaments 2 are prevented from approaching and contacting each other. That is, the predetermined space S (see FIG. 1) is secured between the core filaments 2 adjacent to each other.

After that, the elastic material 4 is sealed in the rubber vulcanizing section 9 between the adjacent core filaments 2 and the adjacent side filaments 3 (see G in FIG. 1). (Experimental example) Table 1 shows experimental examples 1 and 2 of the present invention and 3 + 6.
The results of various performance measurements are summarized for Conventional Examples 1 and 2 having a structure. Further, Table 2 shows Comparative Example 1 in which both the first condition (standard value of rigidity obtained from the total diameter of each filament) and the second condition (total cross-sectional area of each filament) are less than the proper range for the present invention. And the comparative example 2 in which both the first condition and the second condition exceed appropriate ranges, the measurement results of various performances are summarized.

Each of the above-mentioned measurements was carried out using the steel cord of 10.
It was applied to the TBR of 00 / R2 / 14PR. In this tire, the belt layer has a four-layer structure, and the first layer (innermost layer)
Then, 20 steel cords per 5 cm width, 28 second / 5 cm for the second layer, 28/5 cm for the third layer, and 20/5 cm for the fourth layer.

[0024]

[Table 1]

[0025]

[Table 2]

In each table, "air permeation amount" means that the steel cord is embedded in the melted elastic material 4 at a depth of 50 mm, and the length per minute for each steel cord. The amount of air permeation along the direction was investigated. Therefore, the smaller this value is, the better the sealing of the elastic material 4 in the steel cord is. The "rust progress test" means that a hole is made from the tread portion of the tire to the belt layer, salt water is sprayed from this hole, and then a running test of 30,000 km is performed using a drum running device.
In this state, the degree of rust progress was examined.

The "actual vehicle driving stability" and "actual vehicle riding comfort" are based on the subjective evaluation of the same driver in the actual vehicle. The comparative example 1 is a comparative judgment criterion, ○ is equivalent, × is inferior, and ◎ is excellent. did. “Abrasion index” is a traveling distance required for the tread groove depth to decrease by 1 mm, and is represented by an index with Comparative Example 1 being 100. Therefore, the larger the value, the better.

"Belt edge separation test"
Means that the tire was set on the drum traveling device, the camber angle thereof was adjusted to 4 °, and a running test of 200 hrs was performed. In this state, the crack length of the edge portion between the second layer and the third layer of the belt layer was measured. This is what I investigated. As is clear from Tables 1 and 2, in Experimental Examples 1 and 2, the gaps between the adjacent core filaments 2 and the adjacent side filaments 3 (including the core filament 2 and the side filaments 3) Since the elastic material 4 is enclosed instead, extremely good results are obtained in the rust progress test. Further, in terms of rigidity, weight, tire performance (steering stability and riding comfort), etc.
The result is much better than that.

On the other hand, in Comparative Example 1 in which both the first condition and the second condition are less than the proper range, there is a problem in rigidity and the steering stability is also unpopular. Further, in Comparative Example 2 in which both the first condition and the second condition are out of the proper range, the result which can be said to be excessive in terms of rigidity is obtained, but on the other hand, there is a problem in terms of weight. As a result, uncomfortable riding and low durability (fast wear and easy cracking at the edge) are noticeable.

The present invention is not limited to the above embodiment. For example, the size and use of the applied tire are not limited at all. Also, the number of tires used, the pitch, the number of layers, and the like are not limited.

[0031]

The steel cord according to the present invention has a structure of 2 + 5 consisting of two core filaments and five side filaments, and the elastic material is enclosed between these core filaments without any gap. In addition, it is possible to prevent the generation of rust along the longitudinal direction as much as possible, and is excellent in terms of durability.
Moreover, there is no possibility that the weight of the cord is increased or the rigidity of the cord is decreased.

If the core filament and the side filaments are twisted in the same direction and at the same pitch, the predetermined spacing (the elastic material enclosing portion) held between the adjacent core filaments and the adjacent side filaments is steel. Since it is formed continuously along the longitudinal direction of the cord, this is also useful for enhancing the encapsulation property of the elastic material.

As the side filament (the same applies to the core filament), the carbon content is 0.80% or more and 0.9.
The use of 0% or less is more suitable for obtaining a tough and light steel cord. Rigidity standard value calculated from the total diameter of all filaments is 0.085 or more and 0.11
When the value is 0 or less, it is useful in favorably maintaining rigidity, abrasion resistance, steering stability, riding comfort, and the like and preventing the occurrence of separation.

When the total cross-sectional area of all filaments is set to 0.55 or more and 0.65 or less, it is useful in enhancing rigidity and reducing weight. On the other hand, in the method for manufacturing a steel cord for radial tires according to the present invention, the core filaments and the side filaments arranged in a predetermined positional relationship are twisted together in the same direction and at the same pitch, and then compressed between filaments. The procedure is to enclose the elastic material between the adjacent core filaments and between the adjacent side filaments, and to produce a steel cord with a flat cross section in which the elastic material is enclosed without any gap. Can be done easily and reliably.

[Brief description of drawings]

FIG. 1 is a sectional view showing a steel cord according to the present invention.

FIG. 2 is a schematic view showing a method for manufacturing a steel cord according to the present invention.

FIG. 3 is an enlarged cross-sectional view corresponding to line AA in FIG.

FIG. 4 is a cross-sectional view of a steel cord that has been a mainstream in the past.

[Explanation of symbols]

 1 Steel Cord 2 Core Filament 3 Side Filament 4 Elastic Material T Virtual Vertical Isosceles Triangle t1 Long Side t2 Long Side

Claims (4)

[Claims] 1. Two core filaments (2) twisted with a space (S) adjacent to each other, and five core filaments (2) twisted with a space (G) adjacent to each other around these core filaments (2). A side filament (3) of a book, and is formed into a flat cross section with the elastic material (4) enclosed between the core filaments (2) and between the side filaments (3). Steel cord for radial tires that is characterized by 2. The steel cord for a radial tire according to claim 1, wherein the twist of the core filament (2) and the twist of the side filament (3) are made in the same direction and at the same pitch. 3. At least the side filaments (3) having a carbon content of 0.80% or more and 0.90% or less are used, and the rigidity standard value obtained from the total diameter of all filaments is 0. 085 or more and 0.110 or less, and the total cross-sectional area of all filaments is 0.55 or more and 0.6
It is 5 or less, The steel cord for radial tires of Claim 1 or Claim 2 characterized by the above-mentioned. 4. The method for manufacturing a steel cord according to claim 2, wherein one side filament (3) is arranged at each of three corners of the virtual vertically long isosceles triangle (T), and the vertically long strip is formed. One core filament (2) is arranged corresponding to the two long side portions (t1, t2) of the isosceles triangle (T), and these core filaments (2) are further arranged.
The two side filaments (3) remaining on the outer side of the core are arranged one by one, and then the above two core filaments (2) are arranged.
Are positioned so that their respective centers (P) are outside the two long side portions (t1, t2) of the above-described vertically-long isosceles triangle (T), with respect to all core filaments (2) and side filaments (3). Twisting in the same direction and at the same pitch, and then applying a reduction in a direction that crushes the height direction of the above-described vertically-long isosceles triangle (T), and also between adjacent core filaments (2) and side filaments (3). ) The elastic material (4) is enclosed between the adjacent parts to form a flat cross-section, and a method for manufacturing a steel cord for a radial tire.