JP2001316991A - Metal cord and pneumatic tire using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To raise rubber permeability while securing shape retention of a metal cord. SOLUTION: This metal cord comprises metal filaments having 0.017-0.25 mm filament diameter and number (n) of filaments of n=7-12 composed of two or more preformed filaments and three or more nonpreformed filaments. The preformed filaments have relations of formula (1) 10.0d<=Pw<=35.0d... (1), formula (2) 0.5d<=h<=4.0d... (2) and formula (3) 0.014<=d×h/Pw<=0.028... (3) among the filament diameter (d), a wave pitch Pw and a wave height (h). A wire having 0.13 to 0.17 mm is wound at 3.0-7.0 mm pitch on the outside of a bundle obtained by twisting the whole filaments at 10-30 mm pitch while replacing the positions of the filaments.

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, which is capable of improving the permeability of rubber into a filament while keeping the shape of the cord wound by a wrapping wire, and a pneumatic tire using the same.

[0002]

2. Description of the Related Art Various rubber materials, for example, as shown in FIG. 3, are arranged in a bead portion B separately from a carcass C which forms a tire frame of a heavy load tire T, and the bead portion is provided. For the cord reinforcing layer G for reinforcing B, a metal cord obtained by twisting a plurality of metal filaments is often used.

For example, as shown in FIG. 4, the cord reinforcing layer G is twisted without forming a gap between the metal filaments f and f to ensure good formability of the cord reinforcing layer G. A compact cord a around which a wrapping wire j is wound is used.

However, although each of the filaments f, f has been subjected to surface plating, the filaments f, f
Since a space in which rubber cannot penetrate is formed between f, rust is generated or spread in the cord due to the influence of moisture, and the adhesive strength between the cord and rubber is reduced, and the strength of the cord is reduced. There were problems such as breakage of the cord.

In recent years, in order to solve such a problem, as shown in FIG.
A so-called open cord b twisted so that a gap is generated between them, or as shown in FIG.
A metal cord c is proposed in which a gap is formed between the metal filaments by twisting a molding filament f1 having a three-dimensional spiral molding and a non-molding filament f2 to increase the rubber permeability inside the cord. Have been.

However, in the cords b and c shown in FIGS. 5 and 6, when a large number of metal filaments are used,
It is difficult to manufacture a cord in which a wrapping wire is wound while securing the permeability of rubber between filaments. Further, the bead portion B is also a portion to be fitted to a rim, and it is necessary to mold the cord reinforcing layer G with high precision. However, when a metal cord without a wrapping wire is used, the ply There is also a problem that molding accuracy is reduced.

The present invention has been devised in view of such a situation, and replaces 7 to 12 filaments, each of which has a specific shape and is formed into a two-dimensional corrugated shaped filament and a non-shaped filament. On the basis of twisting at a predetermined pitch without forming a specific core filament, a wrapping wire is wound around this filament bundle to secure shape retention and rubber permeability between filaments. It aims to provide a metal cord.

According to the third aspect of the present invention, it is possible to secure the permeability of rubber between filaments while winding a wrapping wire around a filament bundle around a cord reinforcing layer disposed on the bead portion and reinforcing the bead portion. It is an object of the present invention to provide a pneumatic tire capable of improving the molding accuracy of the reinforcing layer and improving durability and the like by using a metal cord.

[0009]

Means for Solving the Problems The invention according to claim 1 of the present invention comprises n (n = 7 to 12) metal filaments having a wire diameter d of 0.17 to 0.25 mm, The metal filaments are two or more and (n-3) or less shaped filaments formed in a two-dimensional wave shape having a straight portion between a peak and a valley of a wave before being twisted. And the remaining non-shaped filament,
And the shaping filament has the same shaping wave pitch Pw and the same wave height h, and the wire diameter d of each shaping filament, the shaping wave pitch Pw, and the wave height h satisfy the following relationship: All of these filaments are twisted at a twist pitch of 10 to 30 mm without forming a specific core filament while exchanging the positions of the filaments to form a filament bundle, and the twist direction of the filament bundle is set outside the filament bundle. Is a metal cord provided with a wrapping wire having a wire diameter of 0.13 to 0.17 mm wound in the opposite direction and at a winding pitch of 3.0 to 7.0 mm. 1
0.0d ≦ Pw ≦ 35.0d
0.5d ≦ h ≦ 4.0d 0.014 ≦ d × h / Pw ≦ 0.028

The invention according to claim 2 is the metal cord according to claim 1, wherein the filament bundle is formed by twisting the forming filament while twisting.

According to a third aspect of the present invention, there is provided a pneumatic tire, wherein the metal cord according to the first aspect is used for a cord reinforcing layer disposed on a bead portion separately from the carcass and for reinforcing the bead portion. It is.

[0012]

An embodiment of the present invention will be described below with reference to the drawings. In the present embodiment, as shown in FIG. 3, a case where the metal cord 1 of the present invention is used for a cord reinforcing layer G arranged on a bead portion B of a heavy-duty tire T and reinforcing the bead portion B is illustrated. And the metal cord 1
As shown in FIGS. 2 (A) and 2 (B), the wire diameter d is 0.
It is composed of n (n = 7 to 12) metal filaments 2 each having a diameter of 17 to 0.25 mm, and the present embodiment exemplifies a metal filament 2 having the same wire diameter d.

Conventionally, as the metal cord constituting the cord reinforcing layer G of the heavy duty tire T used for trucks, buses, etc., for example, a 3 + 9 configuration (total number of filaments: 12) or a 3 + 9 + 15 configuration (total number of filaments: 27) Books) have been used frequently.

In general, increasing the diameter of the metal filament and reducing the number of the metal filaments are advantageous in terms of cost and productivity in producing a cord. Also, in terms of the performance of the cord, there is an advantage that the smaller the number of filaments, the easier it is to increase the degree of penetration of the rubber into the cord.

Accordingly, in the present invention, the 3+
N metal filaments having a wire diameter d of 0.17 to 0.25 mm (n = 7 to 12) so as to be a substitute for the metal cord having the configuration of 9, 3 + 9 + 15, and particularly to be preferably implemented with a reduced number of filaments. It is configured using.

If the wire diameter d of the metal filament 2 is less than 0.17 mm, it becomes difficult to obtain the required rigidity as the cord reinforcing layer G of the heavy duty tire even if the n filaments 2 are twisted. In addition to reducing the durability of the tire, even if the filament is corrugated as described later, the corrugation tends to return to its original state before the cord is twisted, and the rubber permeability tends to be insufficient.

On the other hand, when the wire diameter d exceeds 0.25 mm, the flexibility of the cord required for winding around the bead portion B as the cord reinforcing layer G is insufficient. It is preferable that the metal filament 2 has various surfaces such as metal or resin plated thereon.

Further, the n metal filaments 2 are:
As shown in FIG. 1, two or more and (n−3) or less two-dimensionally shaped two-dimensional waves having a straight portion 3 between a wave peak U and a wave trough D before being twisted. The shaping filament 2A and the remaining non-shaping filament 2B are used.

Each of the molding filaments 2A has at least a wave pitch Pw and a wave height h of the molding.
They are identical to each other. The wave pitch Pw and wave height h are measured as shown in FIG.

Thus, all the metal filaments 2 are
The reason why the molding filament 2A and the non-molding filament 2B are mixed is that all the metal filaments 2
When the metal cord is formed, the initial elongation of the metal cord becomes large, for example, it becomes difficult to use the metal cord for the cord reinforcing layer G for reinforcing the bead portion B, and the cost for the molding is increased, and the bending is also caused. Rigidity and strength decrease.

In the present invention, the molding filament 2A
Is limited to a two-dimensional wavy shape having the linear portion 3, it is easy to form a gap between the filaments. For example, compared to a three-dimensional spiral shaped one, the shaped wave height Even if the height h is relatively small, it is possible to ensure the permeability of the rubber into the cord. Further, even in the case where a large number of filaments are provided and a wrapping wire is wound around the outer periphery, it is possible to increase the permeability of rubber while keeping the cord diameter compact. If the straight portion 3 is not included in the corrugated shape, the permeability of the rubber into the cord is reduced, and the intended purpose cannot be achieved.

As a result of various experiments conducted by the present inventors, when a cord having a limited wire diameter d and including a specific number of the shaping filaments 2A is manufactured, the wire diameter d of the shaping filament 2A, It has been found that it is important that the wave pitch Pw and the wave height h of the shaping satisfy the relationship of the following formulas. 10.0d ≤ Pw ≤ 35.0d ... 0.5d ≤ h ≤ 4.0d ... 0.014 ≤ dxh / Pw ≤ 0.028 ...

When the shaping wave pitch Pw is less than 10.0 times the wire diameter d of the metal filament 2 to be used,
The wave pitch becomes too small, and the shaping process greatly damages the shaping filament 2A, which causes a decrease in strength. Conversely, if it exceeds 35.0 times, the wave pitch becomes too large, and the permeability of the rubber decreases.

If the wave height h is less than 0.5 times the wire diameter d of the metal filament 2 to be used, it becomes difficult to secure rubber permeability, and if it exceeds 4.0 times, it becomes difficult.
The molding process causes a large damage to the molding filament 2A, which causes a decrease in strength.

Further, as shown in the above equation, the present inventors examined the rate of decrease in cord strength (%) and the degree of rubber penetration (%) by variously changing d × h / Pw. h /
It has been found that a remarkable effect is exhibited by limiting Pw to the range of 0.014 to 0.028.

FIG. 7 shows the relationship between the cord strength reduction rate (%), the rubber penetration rate (%), and the parameter d × h / Pw. As is clear from this figure, d × h / P
It can be seen that as w increases, the strength reduction rate of the cord increases and the performance deteriorates, but the rubber permeability increases. Therefore, in the present invention, the possible range of d × h / Pw is set to 0.
014-0.028, more preferably 0.020-0.028.
By limiting the range to 025, the rate of decrease in the strength of the cord is kept within an allowable range, and at the same time, the permeability of the rubber is increased. The strength reduction rate (%) and the rubber permeability (%) here are in accordance with the definitions in Examples (described later).

In this embodiment, all of these filaments 2A are twisted together at a twist pitch of 10 to 30 mm without changing the filament positions and forming a specific core filament and twisting. A filament bundle 4 (shown in FIG. 2) is formed, and the filament bundle 4 is provided outside the filament bundle 4.
The metal cord 1 is obtained by winding a predetermined wrapping wire 6 in a direction opposite to the twisting direction of the wire.

By twisting all the filaments 2 in this manner, it is possible to effectively prevent the waves of the molding filaments 2A from overlapping each other while winding the wrapping wire 6 around the outer periphery of the filament bundle 4.
At the time of twisting, when twisting while twisting, it is possible to form more gaps 5 between the filaments while making the diameter of the filament bundle 4 more compact, and further improve the permeability of rubber into the cord.

FIGS. 2A and 2B are cross-sectional views of the metal cord 1 of the present embodiment. FIG. 2A shows five shaped filaments 2A and five non-shaped filaments 2A.
A metal cord 1 is shown which is formed by twisting bundles into one while replacing the positions of these filaments 2A, 2B using four B's. The metal cord 1 shown in FIG. 2 (B) has six shaping filaments 2A and a non-shaping filament 2A.
B is twisted and bundled into one while replacing these positions using six B's. It can be seen that many gaps are formed between the filaments to increase the permeability of the rubber.

Note that “twisting without forming a specific core filament while changing the position of the filament” means, for example, as shown in FIGS. 2 (A) and 2 (B).
In the cross section of the metal cord 1, the filaments C, C existing near the center are twisted so that the filaments C arranged outside the cord 1 at positions spaced apart in the longitudinal direction of the cord are switched in position. This means that the same filament 2 does not always stay near the center of the metal cord 1. At this time, the positions of the filaments may be switched in a fixed order or in a non-fixed order.

In general, when a large number of molding filaments 2A are twisted into one, very large gaps are formed between the filaments, and problems such as "breakage" in which the filaments are not united in the manufacturing process tend to occur. By twisting the filaments while changing their positions in the longitudinal direction of the cord as in the present invention, the filaments are entangled with each other, the filaments are united well, and the above-mentioned unevenness can be prevented.

Further, by twisting the filaments without changing the positions of the filaments to form a specific core filament, a problem that occurs particularly in a cord having a specific core filament as the cord reinforcing layer G of the bead portion B conventionally. It is possible to exert a remarkable improvement effect on a so-called core missing trouble in which the filament at the central part of the cord that has been pulled through comes through.

If the twist pitch of the filament bundle 4 to be twisted is less than 10 mm, the initial elongation of the cord becomes large, for example, making it difficult to use it for the cord reinforcing layer G for reinforcing the bead portion B. There is a tendency to increase the cost in the process. Conversely, when the twist pitch exceeds 30 mm, when the cord is cut, the molding filament 2
A becomes easy to disperse, which is not preferable in the process.

The relatively thin metal filament 2 having a wire diameter d of 0.17 to 0.25 mm is easily stretched when a load is applied. Therefore, each molding filament 2A per unit length of cord (filament bundle) before molding is formed. If the filament lengths are different from each other, that is, if the wave pitch Pw and the wave height h are not the same, there is a problem in the process that the filament jumps out.

The wrapping wire 6 is wound around the filament bundle 4 outside the filament bundle 4.
And a winding pitch of 3.0 to 7.0 mm. When the winding direction of the wrapping wire 6 is the same as the twisting direction of the filament bundle 4,
It is difficult to prevent misalignment of each filament, and as a result, the precision of molding the ply is reduced. Further, when the winding pitch of the wrapping wire 6 is less than 3.0 mm,
If the productivity is remarkably reduced, on the other hand, if it exceeds 7.0 mm, the shape assurance of the cord will be deteriorated, and the molding accuracy of the ply will be deteriorated.

The wrapping wire 6 needs to have a wire diameter of 0.13 to 0.17 mm. In this embodiment, the wrapping wire 6 is exemplified by a single wire. If the wire diameter of the wrapping wire 6 is less than 0.13 mm, for example, it becomes difficult to maintain the cross-sectional shape of the cord when the cord is bent, and if it exceeds 0.17 mm, the cord diameter becomes large and the weight increases. Is also undesirably large.

The metal filament 2 and the wrapping wire 6 have a carbon content of, for example, 0.65 to 0.88 wt%.
Is preferably used. If the carbon content is less than 0.65%, the strength of the filament or wire tends to decrease. Conversely, if it exceeds 0.88% by weight, the hardness is too high. For example, the strength decreases during molding or lapping. Tends to be larger.

The metal cords 1 are, for example, a plurality of cords arranged in parallel at equal intervals and covered with a topping rubber or the like to form a rubberized ply. For example, the metal cords 1 are arranged separately from a carcass on a bead portion B of a heavy load tire T. It is used for the cord reinforcing layer G for reinforcing the portion B. At this time, the number of metal cords included per unit length of the ply in a direction perpendicular to the longitudinal direction of the cords can be variously set according to the specifications of the tire.

If the number of cords per unit length of the ply is too small, the cord arrangement tends to be disturbed when used in a tire, for example, the cord spacing becomes uneven during vulcanization molding. If the space between the cords is too small, the rubber hardly penetrates between the cords, and the peeling between the cord and the rubber easily occurs.

[0040]

EXAMPLES In order to confirm the effects of the present invention, various metal cords were experimentally produced, and the characteristics of the cords and the tire performance when used as a cord reinforcing layer for reinforcing a bead portion of a tire were compared and evaluated. The prototype tire is size 11R2
2.5 is a heavy duty radial tire. The definitions of the terms in the table are as follows.

<Strength reduction rate> A cord having a compact structure (hereinafter, referred to as a "corresponding cord") which is made of a material having the same composition (having the same composition such as carbon content) and the same number of metal filaments and twisted at the same twist pitch. ), Which is measured in a state before the tire is used. The smaller the numerical value is, the less the strength decreases and the better.

<Elongation under load> Elongation of a cord when a load of 50 N is applied to one cord.

<Bending rigidity>"V-
The bending stiffness of the metal cord was measured using a “5 stiffness tester”.

<Shape retention> A metal cord of about 1000 mm is prepared, and a loop having a diameter of 200 mm is formed on a flat surface.
Both ends of the cord are fixed. Apply force to the loop on the side opposite to the fixed side and crush the loop, and deform in 15 seconds until it touches the point on the loop opposite to the section where the force was applied. The contact state is held for 10 seconds, and then it takes 15 seconds to slowly return to the original position, and the distance L between the point that no longer returns and the contact position is measured.
It is calculated by the formula of measured value E = (L / 200) × 100. The shape retention is indicated by an index, which is the reciprocal of the value obtained by dividing the measured value of each code by the measured value of Example 1 × 100, and the larger the numerical value, the better.

<Rubber Permeability> A tire having the above-described cord reinforcing layer using a sample metal cord is manufactured, and the metal cord is removed from the tire with the topping rubber adhered thereto. After removing the rubber as much as possible from the surface of the rubberized cord, a knife is inserted from the cross section to remove two adjacent filaments, and formed between the removed two filaments and the bundle of the remaining filaments. The length of the portion where the rubber is completely filled in the voids is measured over about 10 cm, and the ratio of the length of the portion filled with rubber to the total length is defined as the rubber permeability.

<Cord pull-out force> After a tire having a cord reinforcing layer is manufactured, a predetermined cut sample of the cord reinforcing layer is cut out from the tire, and a pulling force when pulling out a metal cord from the sample and the force. Plot the length of the metal cord pulled out with
The force required to pull out the metal cord by 15 mm was determined.

<Rust generation index after running> After running the tire for about 200,000 km, the tire is disassembled, the rust generation state of the metal cord is observed from the cord reinforcing layer, and the index for comparison is set to 100. Displayed with. The smaller the numerical value, the better the less rust is generated.

<Strength Retention after Running> After running the tire for about 200,000 km, the tire is disassembled, the metal cord is taken out from the cord reinforcing layer, and the strength of the cord before running is 100%.
It is indicated by an index. The higher the value, the better.

Tables 1 and 2 show the test results.

[0050]

[Table 1]

[0051]

[Table 2]

[0052]

As described above, in the metal cord according to the first or second aspect, it is possible to increase the rubber permeability into the cord while securing the shape retention of the cord by winding a wrapping wire. The generation of rust inside can be greatly reduced, and the durability can be improved. In addition, by limiting the wire diameter and winding pitch of the wrapping wire, and by mixing typed filaments and non-typed filaments, the cord diameter is reduced and the shape retention of the cords is improved while improving the ply molding accuracy. Help to do.

Further, the metal cord can exhibit good properties comparable to those of the compact cord in terms of the cord strength, strength reduction rate, elongation under load (at 50 N), flexural rigidity and the like. Further, there is no problem such as jumping out of the filament or unevenness in the process, which is very good. Further, when the shaped filaments are twisted while being twisted, it is possible to further improve the permeability of the rubber into the cord while making the diameter of the filament bundle more compact.

According to the third aspect of the present invention, by using the metal cord for the cord reinforcing layer for reinforcing the bead portion of the tire, the generation of rust inside the tire of the metal cord can be suppressed, and the strength of the cord can be reduced. While effectively preventing breakage and the like, it is possible to improve the durability of the tire, and as a result of the metal cord being excellent in shape retention, it is possible to provide a pneumatic tire having improved ply molding accuracy and excellent dimensional stability. .

[Brief description of the drawings]

FIG. 1 is a plan view showing an example of a molding filament.

FIGS. 2A and 2B are cross-sectional views illustrating a cord according to the present invention.

FIG. 3 is a sectional view of a heavy duty tire.

FIG. 4 is a sectional view of a compact cord.

FIG. 5 is a sectional view of an open cord.

FIG. 6 is a cross-sectional view of a cord including a spiral shaped filament.

FIG. 7 shows the rate of decrease in cord strength, rubber permeability, and d × h /
It is a graph which shows the relationship of Pw.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metal cord 2 Metal filament 2A Molding filament 2B Non-molding filament 3 Straight part 4 Filament bundle 6 Wrapping wire T Heavy load tire

Continuation of the front page (72) Inventor Kazumi Yamazaki 3-6-9, Wakihama-cho, Chuo-ku, Kobe-shi, Hyogo Inside of Sumitomo Rubber Industries Co., Ltd. No. 9 Sumitomo Rubber Industries, Ltd. (72) Inventor Yasuo Sakai 1-1-1, Kunyokita, Itami-shi, Hyogo F-term in Sumitomo Electric Industries, Ltd. Itami Works 3B153 AA06 AA46 BB13 BB20 CC52 GG01 GG05 GG07 GG40

Claims (3)

[Claims] The present invention comprises n (n = 7 to 12) metal filaments having a wire diameter d of 0.17 to 0.25 mm, and the metal filaments have a wave crest before being twisted. The two or more (n-3) or less two-dimensionally shaped filaments having a straight portion between the valley portion and the valley portion, and the remaining non-molded filaments; The shaping wave pitch Pw and the wave height h are the same, and the wire diameter d of each shaping filament, the shaping wave pitch Pw and the wave height h satisfy the following formula: The filament bundle is formed by twisting the filament bundle at a twist pitch of 10 to 30 mm without forming a specific core filament while changing the position of the filament. Metal cord to the twist direction of the filament bundle to the side is the wire diameter that is wound at the winding pitch of 3.0~7.0mm to and in the opposite direction becomes comprise a wrapping wire 0.13～0.17Mm. 10.0d ≤ Pw ≤ 35.0d ... 0.5d ≤ h ≤ 4.0d ... 0.014 ≤ dxh / Pw ≤ 0.028 ... 2. The metal cord according to claim 1, wherein the filament bundle is formed by twisting the forming filament while twisting. 3. A pneumatic tire characterized in that the metal cord according to claim 1 or 2 is arranged in a bead portion separately from the carcass and is used as a cord reinforcing layer for reinforcing the bead portion.