JP2000045190A - Metal cord and pneumatic tire using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metal cord ensuring its shape retainability and simultaneously enhancing rubber permeability. SOLUTION: This metal cord comprises nine metal filaments each having a wire diameter (d) of 0.17-0.25 mm. All the metal filaments comprise embossed filaments 2A embossed in two-dimensional wave shapes before stranded. The embossed filaments 2A have two or more different kinds of pitches Pw. The wire diameter (d), embossed wave pitch Pw and embossed wave height (h), or the like, of each embossed filament 2A are formed in prescribed ranges, respectively. While the positions of all the embossed filaments are replaced, all the embossed filaments are stranded in a strand pitch of 10-20 mm to form a filament bundle. The non-embossed lengths of the embossed filaments contained in a unit length of the filament bundle are approximately equalized to each other. A lapping wire is wound on the outside of the filament bundle in a prescribed pitch.

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. 4, are arranged in a bead portion B separately from a carcass C which forms a tire skeleton of a heavy load tire T, and the bead portion is provided. The cord reinforcing layer G that reinforces
A metal cord obtained by twisting a plurality of metal filaments is often used.

For example, as shown in FIG. 5, 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.

Therefore, in recent years, in order to improve 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. 6 and 7, when the number of metal filaments becomes large,
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 the above situation, and is capable of forming a specific core filament while forming nine specific shaped filaments which are two-dimensionally corrugated while changing positions. A wrapping wire is wound around the filament bundle on the basis that the filament length is twisted at a predetermined pitch, and the length of each of the molding filaments contained per unit length of the twisted filament bundle is made substantially equal before molding. It is an object of the present invention to provide a metal cord capable of ensuring rubber permeability between filaments while ensuring shape retention.

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]

The invention according to claim 1 of the present invention comprises nine metal filaments having a wire diameter d of 0.17 to 0.25 mm. It is composed of two-dimensionally shaped filaments having a straight portion between the peaks and valleys of the waves before being twisted, and at least two types of the filaments having different wave pitches Pw. The shaping wave pitch Pw and the wave height h are the same for each filament of a different type, and the wire diameter d of each shaping filament, the shaping wave pitch Pw and the wave height h are represented by the following formulas: When the wave pitch of the shaping filament having the minimum wave pitch is Pw1 and the wave height is h1, the shaping filament having another wave pitch is satisfied. Wave pitch Pwn, wave height h
n satisfies the relationship of the following formula, and replaces all of these shaped filaments without forming a specific core filament while changing the positions of the filaments.
A twisted filament bundle is formed while being twisted at a twist pitch of 0 to 20 mm, and the length of each of the shaped filaments contained per unit length of the filament bundle is substantially equal before molding, and the outside of the filament bundle is formed. The metal cord comprises a wrapping wire having a wire diameter of 0.13 to 0.17 mm wound in a direction opposite to the twisting direction of the filament bundle and at a winding pitch of 3.0 to 7.0 mm. 10.0d ≦ Pw ≦ 35.0d... 0.5d ≦ h ≦ 4.0d... 0.75 × h1 / Pw1 ≦ hn / Pwn ≦ 1.25 × h1 / Pw1.

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. 4, a metal cord for tire reinforcement used for a cord reinforcement layer G disposed on a bead portion B of a heavy-duty tire T and reinforcing the bead portion B is illustrated. , The metal cord is
It is composed of nine metal filaments having a wire diameter d of 0.17 to 0.25 mm, and the present embodiment exemplifies a metal filament having the same diameter.

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+
In order 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, nine metal filaments having a wire diameter d of 0.17 to 0.25 mm are used.

The wire diameter d of the metal filament is equal to 0.
If it is less than 17 mm, it becomes difficult to obtain the required rigidity as the cord reinforcing layer of the heavy duty tire even if the nine filaments are twisted, and the durability of the tire is reduced. Even if wavy shaping is performed, the shaping tends to return to the original state during twisting before twisting into the cord, and the rubber permeability tends to be insufficient.

On the other hand, if the wire diameter d exceeds 0.25 mm, the flexibility of the cord required for winding around the bead portion as a cord reinforcing layer is insufficient. It is preferable that the metal filament has a surface on which various kinds of plating such as metal or resin are applied.

Further, all the metal filaments 2 are shown in FIG.
As shown in (A) and (B), the two-dimensional corrugated molding filaments 2A1,... 2An having a straight part 3 between the wave peak U and the valley D before being twisted.
(Hereinafter, when simply collectively referred to as “typed filament 2
A ". ).

The shaping filament 2A includes at least two shaping filaments 2A1 and 2An having different wave pitches Pw, and in this example, two shaping filaments 2A1 and 2An. However, the wave pitch Pw and the wave height h of the shaping for the filaments of different types are the same.
The wave pitch Pw and the wave height h are measured as shown in FIG.

The reason why all the metal filaments 2 are formed from the molding filaments 2A is that if only a part of the metal filaments 2 is molded, more unmolded non-molding filaments are used. This is because a load may act to cause a problem of reducing the strength of the entire cord.

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 Even if the height h is relatively small, the permeability of the rubber into the cord can be ensured. 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.

Further, when the molding filament 2A does not include at least two or more filaments having different wave pitches Pw, when a relatively large number of metal filaments such as nine are twisted, as shown in FIG. The straight portions 3 of the shaping waves of the shaping filaments 2A1 and 2A1 are likely to overlap each other, and this is not preferable because the permeability of rubber is reduced.

Preferably, the number of types of the forming filament 2A is two in consideration of easiness of manufacture and cost. It is desirable that the minimum number of the molding filaments 2A included in each type is at least two, and preferably three.

The wire diameter d, the shaping wave pitch Pw, and the wave height h of each shaping filament 2A must satisfy the following relationship. 10.0d≤Pw≤35.0d ... 0.5d≤h≤4.0d ...

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 causes a large damage to 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 is difficult to ensure rubber permeability, and if it exceeds 4.0 times,
The molding process causes a large damage to the molding filament 2A, which causes a decrease in strength.

Further, as shown in FIG. 1B, for example, as shown in FIG. 1B, when the wave pitch of the shaping filament 2A1 having the minimum wave pitch is Pw1 and the wave height is h1, the shaping filament 2An having another wave pitch is used.
It is necessary that the wave pitch Pwn and the wave height hn satisfy the following relationship. 0.75 × h1 / Pw1 ≦ hn / Pwn ≦ 1.25 × h1 / Pw1 ...

According to this equation, the ratio (hn1 / Pw1) of the molding filament 2A1 having the minimum wave pitch is obtained.
Can be limited to the ratio (hn / Pwn) of the shaping filaments 2An having another wave pitch in the range of ± 25%. If there are two or more shaping filaments having the smallest wave pitch PW1 but different wave heights, the wave pitch of the shaping filament having the smallest wave height is defined as Pw1, and the wave height is defined as h1.

As a result of various experiments conducted by the present inventors, the ratio between the wave pitch and the wave height of the shaping filaments 2 of different types is, as described above, the (hn1 / Pw1) of the shaping filament 2A1 having the minimum wave pitch. It has been found that it is preferable to limit the range to ± 25%. (Hn /
When (Pwn) is less than 0.75 times (h1 / Pw1) or more than 1.25 times (h1 / Pw1), both are included per unit length of the filament bundle 4 in which they are twisted. A large difference occurs in the filament length of the molding filament 2 before molding, and when a tension is applied to the cord, a large load is applied only to a specific filament, which causes a decrease in the strength of the cord.

In the present embodiment, all of these molding filaments 2A are replaced with each other without changing the positions of the filaments to form a specific core filament.
And twist at a twist pitch of 10 to 20 mm while twisting.
A filament bundle 4 (shown in FIG. 2) twisted into a book is formed, and the filament length of each molding filament 2A per unit length of the filament bundle 4 before molding is made substantially equal. The metal cord 1 is obtained by winding a predetermined wrapping wire around the outside of the bundle in a direction opposite to the twisting direction of the filament bundle 4.

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

FIG. 2 is a sectional view of the metal cord 1 of the present embodiment. It is constituted by using six shaping filaments 2A1 having a small wave pitch and three shaping filaments 2An having a larger wave pitch, and twisting them into one while changing the positions of these filaments.
It can be seen that many gaps are formed between the filaments to increase the permeability of the rubber.

"Twisting without forming a specific core filament while changing the position of the filament" means that, for example, as shown in FIG. , C
However, at a position spaced apart in the longitudinal direction of the cord, a molding filament 2 disposed outside the cord 1 in the cross section
A means that the same typed filament 2A is not always stopped near the center of the metal cord 1 because it is twisted so as to exchange its position with A. 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 position of the filaments while forming the specific core filaments, it becomes a particular problem 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 20 mm, when the cord is cut, the molding filament 2
It is easy to disperse, which is not preferable in the process.

Further, in the filament bundle 4 to be the metal cord 1 of the present invention, the filament lengths before the molding of all the molding filaments 2A included per unit length are substantially equal (the difference in length is ± 2%). %), The strength of the cord can be increased by making full use of the forces of all the shaping filaments.

Since the relatively thin metal filament 2 having a wire diameter of 0.17 to 0.25 mm is easily stretched when a load is applied, the filament 2A per unit length of the cord (filament bundle) is formed by the filament before molding. If the lengths are different from each other, there is a problem in the process that the filaments fly out.

The wrapping wire 5 is wound outside the filament bundle 4 in a direction opposite to the twisting direction of the filament bundle 4 and at a winding pitch of 3.0 to 7.0 mm. If the winding direction of the wrapping wire 5 is the same as the twisting direction of the filament bundle 4, it is difficult to prevent the displacement of each filament, and the ply molding accuracy is reduced. If the winding pitch of the wrapping wire 5 is less than 3.0 mm, the productivity is remarkably reduced, and if it is more than 7 mm, the shape security of the cord is deteriorated, and the precision of forming the ply is deteriorated.

The wrapping wire 5 needs to have a wire diameter of 0.13 to 0.17 mm. In this embodiment, the wrapping wire 5 is exemplified by a single wire. If the wire diameter of the wrapping wire 5 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 5 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. 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 for a tire, for example, the cord spacing becomes uneven at the time of 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.

[0044]

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 definitions of the terms in the table are as follows.

<Strength Reduction Rate> A cord having a compact structure (hereinafter referred to as a "comparative 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.

<Bending Rigidity of Cord> The bending rigidity of the metal cord was measured using a “V-5 Rigidity Tester” manufactured by Taba (USA).

<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 provided with 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 attached. 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 pulling force of tire in tire> After manufacturing a tire having a cord reinforcing layer, a predetermined cut sample of the cord reinforcing layer is cut out from the tire, and the pulling force when the metal cord is pulled out from this sample is determined. ,
The pulling length of the metal cord pulled out by the force was plotted, and the force required to pull out the metal cord by 15 mm was obtained.

<Rust index after running the tire> After running the tire for about 200,000 km, disassemble the tire, observe the occurrence of rust on the metal cord from the cord reinforcing layer, and set the comparison target code to 100. It is indicated by exponent. The smaller the numerical value, the better the less rust is generated.

<Strength Retention after Running Tire> After running the tire for about 200,000 km, disassemble the tire, take out the metal cord from the cord reinforcing layer, and indicate the index with the strength of the cord before running as 100. are doing. The higher the value, the better.

<Protrusion of Filament in Step> In the step of forming the cord reinforcing layer of the tire, the state of protrusion of the filament of the metal cord was examined.

<Variation when the cord is cut in the process> In the process of forming the cord reinforcing layer of the tire, the condition of the variation in the cord when the metal cord was cut was examined. Table 1 shows the test results.

[0054]

[Table 1]

[0055]

[0056]

In Table 1, Comparative Example 1 is a compact cord obtained by bundling and twisting 12 non-shaped filaments, Comparative Example 2 is a layer-twisted structure having a specific core filament, and Comparative Example 3 is 9 non-shaped filaments Comparative Example 4 is a bundle twisted structure composed of one type of shaped filament and non-typed filament, Comparative Example 5 is a bundle twisted structure composed of nine typed filaments having one type of wave pitch. Example 6 is composed of two types of shaped filaments, but the difference of the ratio (h / Pw) is out of the specified range, Comparative Example 7 is the one in which the wrapping wire winding pitch is out of the specified range, and Comparative Examples 8 and 9 are metal. The filament diameter of the filament is out of the specified range, Comparative Examples 10 to 13 are those in which the wave pitch or wave height of the shaped filament is out of the specified range, Comparative Example 14 There 15 as wire diameter of the wrapping wire is out of the specified range, Comparative Example 16 to 17 are those twist pitch of the filaments bundle is outside the specified range.

On the other hand, in Examples 1 to 8, it can be confirmed that the cord diameter is relatively compact while the wrapping wire is wound, and the rubber permeability is high.
In addition, it was confirmed that the shape retention of the cord was very good by limiting the winding pitch, wire diameter, and the like of the wrapping wire.

In each of the cords of the examples, the cords were cut without centering in the tires in the centering force test of the cords, and it was confirmed that the cords had good adhesion to rubber. it can.

Further, in the cord of the embodiment, the twist of the filament bundle is improved and the wrapping wire is used.
It was extremely good without causing the filaments to jump out or the cords to be uneven in the process. In Example 5, slight variation was confirmed when the cord was cut in the process, but it was not to the extent that it would cause a problem in the process.

Further, by using such a metal cord as a cord reinforcing layer disposed on a bead portion to reinforce the bead portion, a pneumatic tire capable of improving molding accuracy of the reinforcing layer and improving durability and the like can be provided. Can be provided.

[0062]

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, the shape of the cord is maintained while the cord diameter is reduced,
This is useful for improving the precision of forming the ply.

Further, the metal cord can exhibit good properties comparable to those of the compact cord in terms of 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, it is possible to suppress the occurrence of rust inside the tire of the metal cord, and to reduce the strength of the cord. 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]

FIGS. 1A and 1B are plan views showing an example of a molding filament. FIG.

FIG. 2 is a sectional view of a cord according to the present invention.

FIG. 3 is a plan view illustrating the overlapping of waves of a forming filament.

FIG. 4 is a cross-sectional view of a heavy duty tire.

FIG. 5 is a sectional view of a compact cord.

FIG. 6 is a sectional view of an open cord.

FIG. 7 is a cross-sectional view of a cord including a spiral shaped filament.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metal cord 2 Metal filament 2A Molding filament 3 Straight part 4 Filament bundle 5 Wrapping wire T Heavy load tire

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Yasuo Sakai 650 No. 630, Kami-Oso-cho, Utsunomiya-shi, Tochigi F-term (reference) 3B153 AA07 AA18 AA46 BB13 CC52 FF16 GG05 GG13

Claims (3)

[Claims] The present invention comprises nine metal filaments having a wire diameter d of 0.17 to 0.25 mm, and all of the metal filaments have a wave crest and a valley before being twisted. A two-dimensional corrugated filament having a linear portion between the corrugated filaments, and the corrugated filament has at least the wave pitch P
w includes two or more different type filaments,
Wave pitch P of the above-mentioned molding for each type of filament
w and the wave height h are the same, and the wire diameter d of each molded filament, the molded wave pitch Pw, and the wave height h satisfy the following equation: Assuming that Pw1 and the wave height are h1, the wave pitch Pwn and the wave height hn of the molding filament having another wave pitch
However, while satisfying the relationship of the following formula, and forming a filament bundle by twisting all these shaped filaments at a twist pitch of 10 to 20 mm without forming a specific core filament while changing the position of the filaments The length of each of the shaped filaments contained per unit length of the filament bundle before molding is made substantially equal, and outside the filament bundle, in the direction opposite to the twist direction of the filament bundle and 3.0 to 3.0. A metal cord comprising a wrapping wire having a wire diameter of 0.13 to 0.17 mm wound at a winding pitch of 7.0 mm. 10.0d ≦ Pw ≦ 35.0d... 0.5d ≦ h ≦ 4.0d... 0.75 × h1 / Pw1 ≦ hn / Pwn ≦ 1.25 × h1 / Pw1. 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.