JP3349447B2 - Metal cord and pneumatic tire using the same - Google Patents

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 can increase rubber permeability into filaments while reducing the cord diameter, and a pneumatic tire using the same.

[0002]

2. Description of the Related Art Metal cords obtained by twisting a plurality of metal filaments are often used in various rubber materials, for example, a carcass layer of a pneumatic radial tire. Although such a metal cord has a plated surface, for example, as shown in FIG. 4, in the case of a compact cord a having no gap between the metal filaments f, rubber penetrates between the filaments. Unsuitable space is formed, which causes rust in the cord due to the influence of moisture or the spread of the cord, causing problems such as a decrease in the adhesive strength between the cord and rubber, a decrease in the strength of the cord, and a break in the cord. There was a point.

In recent years, in order to improve such a problem, as shown in FIG.
By so-called open cord b twisted so that a gap is generated between f, as shown in FIG. 6, by twisting a three-dimensional spiral shaped shaping filament f1 and a non-shape filament f2, There has been proposed a metal cord c in which a gap is formed between metal filaments to increase the permeability of rubber inside the cord.

However, in each of the above-mentioned cords, there is a disadvantage that the cord diameter naturally becomes large in order to ensure a sufficient rubber permeability. In addition, such cords tend to have a very large elongation under low load.For example, when used for a carcass layer forming a skeleton of a pneumatic tire, the shape of the tire is not stable and is not suitable for practical use. found.

The present invention has been devised in view of the above-mentioned situation, and a specific core is formed by changing the positions of eight to twelve molding filaments which are molded into a two-dimensional wave shape having a specific shape before twisting. Twisting while twisting at a predetermined pitch without forming a filament, and on the basis that the filament length before molding of each molding filament included per unit length of the twisted filament bundle is substantially equal, It is an object of the present invention to provide a metal cord capable of ensuring rubber infiltration between filaments while reducing the cord diameter and suppressing elongation under a low load, and a pneumatic tire using the same.

[0006]

The present invention according to claim 1 of the present invention comprises 8 to 12 metal filaments having the same diameter and a wire diameter d of 0.15 to 0.30 mm. Before being twisted, the metal filament comprises a two-dimensionally corrugated molding filament having a straight portion between a peak and a valley of a wave, and the molding filament has at least the wave pitch. While including two or more types of shaping filaments having different Pw, the shaping wave pitch Pw and the wave height h are the same for each type of filament, and the wire diameter d, shaping wave pitch Pw, and wave height of each shaping filament are the same. Sa is the following formula,
Is satisfied, and the wave pitch of the shaping filament having the minimum wave pitch is Pw1 and the wave height is h1,
Wave pitch P of shaped filament with other wave pitch
wn and wave height hn satisfy the relationship of the following formula, and all these molded filaments are twisted at a twist pitch of 10 to 25 mm without forming a specific core filament while changing the position of the filament. This is a metal cord that forms a bundle and that has a substantially equal filament length before molding of each molding filament included per unit length (1 m) of the filament bundle. 10.0d ≦ Pw ≦ 35.0d... 0.5d ≦ h ≦ 4.0d... 0.75 × h1 / Pw1 ≦ hn / Pwn ≦ 1.25 × h1 / Pw1.

According to a second aspect of the present invention, the shaped filament is twisted and twisted to form the filament bundle.
It is a metal cord described.

According to a third aspect of the present invention, there is provided a pneumatic tire using the metal cord according to the first or second aspect in a carcass layer.

[0009]

An embodiment of the present invention will be described below with reference to the drawings. In the present embodiment, a metal cord for tire reinforcement used in a carcass layer of a pneumatic radial tire is illustrated, and the metal cord has a wire diameter d of 0.1.
It is composed of 8 to 12 metal filaments having the same diameter of 15 to 0.30 mm.

Conventionally, as a carcass cord constituting a carcass layer of a heavy duty tire used for a truck, a bus or the like, for example, a 3 + 9 configuration (total number of filaments: 12) or a 3 + 9 + 15 configuration (total number of filaments: 27), etc. It has been heavily used.

In general, it is advantageous to increase the wire diameter of the metal filament and to reduce the number of the metal filaments 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 + 9, 3 + 9 +
The wire diameter d is set to 0.15 to 0.15 in order to be able to be used as a substitute for the metal cord of the 15 configuration and to reduce the number of filaments after sufficiently considering the fatigue resistance.
8-12 metal filaments of the same diameter of 0.30 mm
It is configured using this.

The wire diameter d of the metal filament is equal to 0.1.
If it is less than 15 mm, it becomes difficult to obtain the necessary strength as a reinforcing cord material for the carcass layer of a heavy duty tire when twisting 8 to 12 filaments, and the filament is corrugated as described later. Even before the cord is twisted, the mold tends to return to its original state when twisted, and the rubber permeability tends to be insufficient. Conversely, if the wire diameter d exceeds 0.30 mm, the flexibility of the cord required for the carcass layer is impaired, and the fatigue resistance of the cord also deteriorates.
It is preferable that the metal filament has a surface on which various kinds of plating such as metal or resin are applied.

Further, as shown in FIGS. 1A and 1B,
Before the metal filaments 2 are twisted together, the two-dimensional corrugated molding filaments 2A1, having a straight portion 3 between the peak U and the valley D of the wave, are formed.
2An (hereinafter sometimes simply referred to as “molding filament 2A”).

The shaping filament 2 is illustrated as including at least two or more shaping filaments 2A1 and 2An having different wave pitches Pw, in this example. 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 composed of 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, for example, the cord diameter can be made smaller than that of a three-dimensional spiral shape. Even if the height h is relatively small, and even if there are many filaments, it is relatively easy to form a gap between the filaments when twisted. If the straight portion 3 is not included in the corrugated shape, the permeability of the rubber into the cord decreases, and the intended purpose cannot be achieved.

Furthermore, if the shaping filament 2A does not include at least two or more filaments having different wave pitches Pw, when a relatively large number of metal filaments of 8 to 12 are twisted, as shown in FIG. For example, the linear portions 3 of the shaping waves of the shaping filaments 2A1 and 2A1 tend to overlap with 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 ease 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 ...

The wave pitch Pw of the shaping is from 10.0 times to 35.0 times the wire diameter d of the shaping filament 2 to be used.
Times, preferably a value in the range of 15.0 to 30.0 times. When the wave pitch Pw is less than 10.0 times the wire diameter d, the wave pitch becomes too small, and the molding filament 2A is greatly damaged by the molding process, which causes a decrease in strength. Conversely, if it exceeds 35.0 times, the wave pitch becomes too large, and the permeability of rubber decreases.

The wave height h is 0.5 times the wire diameter d.
The range is from 2 to 4.0 times, preferably from 1.0 to 3.0 times. When 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 increase the rubber penetration rate. Damage to the molding filament 2A is large and 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 (hn / Pwn) of the molding filament 2An having another wave pitch is limited to a range of ± 25% of the ratio (h1 / Pw1) of the molding filament 2A1 having the minimum wave pitch. be able to. In the case where two or more types of filaments having the minimum wave pitch PW1 but different wave heights exist,
Let the wave pitch of the shaped filament with the minimum wave height be P
w1 and the wave height are 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 (h1 / 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%. The above (hn / P
wn) is less than 0.75 times (h1 / Pw1),
In addition, when the value exceeds 1.25 times (h1 / Pw1), the unit length (1
m) , it is difficult to make the filament length of the molding filament 2 before molding equal to that of the molding filament 2, and a load is easily applied 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 formed without changing the positions of the filaments and forming a specific core filament.
The filament bundle 4 (shown in FIG. 2) is formed by twisting the filament bundle at a twist pitch of 10 to 25 mm while twisting, and the unit length of the filament bundle 4
In the table of Examples, "filament length per meter of cord"
(Cm) ”and the unit length (1
The metal cord 1 is obtained by making the filament lengths before molding of each of the molding filaments 2A included per m) substantially equal. Here, “substantially equal” means “co
Per meter. Example of "filament length (cm)"
8, 106.4, 106, 7, 106.6 and
The three different filaments of
Therefore, “substantially equal” means (106.7-10
6.4) within the range of about 106.4, that is, within 0.28%
Means substantially equal lengths.

As described above, all the molding filaments 2A
By twisting the filaments, it is possible to effectively prevent the waves of the molding filaments 2A from overlapping each other while reducing the cord diameter, so that many gaps 5 can be formed between the filaments, and thus the rubber inside the cord can be formed. Permeability can be increased. Moreover, it is possible to effectively prevent the initial elongation of the cord from becoming extremely large.

Further, when twisting is applied to the molding filament in twisting as in this embodiment, it is preferable in that the cord diameter can be further reduced and the permeability of rubber into the cord can be increased.

FIG. 2A is a sectional view of the metal cord 1 composed of nine molding filaments 2A. Six shaping filaments 2A1 having a small wave pitch and three shaping filaments 2An having a larger wave pitch are used.
The present invention is used while replacing the positions of these filaments. It can be seen that many gaps are formed between the filaments to increase the rubber permeability.

FIG. 2B is a cross-sectional view of a metal cord 1 composed of eight molding filaments 2 as another example. The configuration is such that five molding filaments 2A1 having a small wave pitch and three molding filaments 2An having a larger wave pitch are used, and the positions of these filaments are interchanged.

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 of the metal cord 1 are replaced at positions spaced apart in the longitudinal direction of the cord with the molding filaments 2 A located outside the cord 1 in the cross section. This means that the same shaped filament 2A 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.

Further, a large number of molding filaments 2A are
When twisted into a book, very large gaps are formed between the filaments, causing problems such as "barrage" in which the filaments are not united in the manufacturing process.However, as in the present invention, the position of the filament is set to the length of the cord. By twisting the filaments while changing their positions in the direction, entanglement occurs between the filaments, which improves the unity of the filaments and can prevent the above-mentioned unevenness.

If the twist pitch of the filament bundle 4 is less than 10 mm, the initial elongation of the cord becomes large, making it difficult to use the filament as a carcass layer for stabilizing the shape of a pneumatic tire. There is a tendency to increase the cost in the process. Conversely, twist pitch is 2
If it exceeds 5 mm, when the cord is cut, the molding filaments 2 tend to come apart, which is not preferable in the process.

Further, in the filament bundle 4 which becomes the metal cord 1 of the present invention, the filament lengths before molding of all the molding filaments 2A included per unit length are substantially equal (for example, the difference in length is small). The range of ± 25% or less, preferably ± 10% or less, and more preferably ± 5% or less) allows the strength of the cord to be increased by maximizing the use of the power of all the molding filaments.

In addition, a relatively thin metal filament having a wire diameter of 0.15 to 0.30 mm, which is employed in the present invention, is easily elongated when a load is applied. If the filament lengths per unit length of the filament 2A before molding are greatly different from each other, a problem in the process that the filament jumps out in the rubber attaching step to the cord is likely to occur. By making the lengths substantially equal, such a problem can be prevented.

The metal filament 2 is preferably made of a hard steel wire having a carbon content of, for example, 0.65 to 0.88 wt%. The carbon content of the metal filament is 0.65
%, There is a tendency for the strength of the filament to decrease. Conversely, when it exceeds 0.88 wt%, the hardness of the filament tends to be too high, and the strength tends to decrease during molding.

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, which is used, for example, as a carcass layer of a heavy duty tire. 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 is liable to be disturbed when used for a tire, for example, the cord spacing becomes uneven at the time of vulcanization molding. If the gap between the cords is too small, the rubber sandwiched between adjacent cords during running of the tire will have a large distortion, and it will easily cause a decrease in tire durability due to the occurrence of cracks and the like in the rubber layer.

[0039]

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 carcass layer 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 “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.

<Rubber Permeability> A tire having a carcass layer using a sample metal cord is manufactured, and the metal cord is removed from the tire with the topping rubber attached. After removing as much rubber as possible from the surface of the rubber cord, a knife is inserted from the cross section to remove two adjacent filaments out of 8 to 12 filaments, and the removed two filaments and the remaining two filaments are removed. Measure the length of the part where the gap formed between the filament bundle is completely filled with rubber over about 10 cm, and determine the ratio of the length of the part filled with rubber to the total length to determine the permeation of rubber. Rate.

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

<Rust generation index after running the tire> After running the tire for about 200,000 km, the tire is disassembled, and the rust generation state of the metal cord is observed. ing. The smaller the numerical value, the better the less rust is generated.

<Strength Retention after Running Tire> The tire is disassembled after the tire has been run for about 200,000 km, and a metal cord is taken out. The higher the value, the better.

<Protrusion of Filament in Step> In the step of rubberizing the cord, it was examined whether or not there was a problem that the filament was protruded from the metal cord.

<Variation at the time of cutting the cord in the process> In the step of forming the carcass layer of the tire, the state of variation of the cord when the metal cord was cut was examined. Table 1 shows the test results.

[0047]

[Table 1]

Each of Comparative Examples 1 to 11 and Examples 1 to 8 is a cord composed of nine metal filaments having a wire diameter d of 0.20 mm. Comparative Example 1 has a compact cord (corresponding cord), Comparative Example 2 has one type and five filaments, Comparative Example 3 has a three-dimensional spiral shape, and Comparative Examples 4 and 5 have a three-dimensional spiral shape. Nine shaping filaments but one type of wave pitch, Comparative Example 6 has a wave pitch smaller than a specified range,
Comparative Example 7 has a wave pitch larger than a specified range, Comparative Example 8 has a wave height smaller than a specified range, Comparative Example 9 has a wave height larger than a specified range, Comparative Examples 10 and 11.
The twist pitch is out of the specified range of the present invention.

On the other hand, Examples 1 to 8 are comparative examples 3
(Cord with spiral shaped filament)
In each case, it can be confirmed that the cord diameter is reduced. Also, compared to Comparative Example 1, the strength of the cord, the rate of decrease in strength, and the elongation under load (5
0N), it can be confirmed that good code characteristics are exhibited.

In the cords of the examples, it can be confirmed that the cord diameter is reduced and the permeability of the rubber is increased, and the occurrence rate of rust on the tires is very low and very good. In addition, there was no problem such as a filament jumping out or a rag in the process, and it was very good.

In Comparative Example 12 in which the wire diameter of the metal filament is smaller than the specified range of the present invention, the flexural rigidity of the cord is extremely small, and in Comparative Example 13 in which the wire diameter is larger than the specified range of the present invention. Excessive rigidity causes loss of cord flexibility.

In addition, in Example 9 and Comparative Example 14, the cord made of the thinnest metal filament having a wire diameter d of 0.15 mm in the range of the present invention, and Comparative Example 15 and Example 1
0 indicates a cord made of the thickest metal filament in the range of the present invention having a wire diameter d of 0.30 mm, and a cord made of Example 12, Comparative Example 17, and 12 metal filaments, respectively. The cord of the embodiment has a good rubber permeability and strength retention while reducing the cord diameter, and can limit the initial elongation (at 50 N) of the cord to 0.09 to 0.19%.

[0053]

As described above, the metal cords according to the first and second aspects can increase the rubber penetration into the cords while reducing the cord diameter, and greatly reduce the occurrence of rust inside the cords. To improve durability. In addition, the cord can exhibit excellent properties comparable to those of a compact cord in terms of strength, rate of decrease in strength, 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 twisting is applied to the molding filament in twisting, the cord diameter can be made more compact and the rubber permeability into the cord can be further increased.

According to the third aspect of the present invention, the use of the metal cord in the carcass layer of the tire can suppress the generation of rust inside the tire of the metal cord, and can effectively reduce the strength and breakage of the cord. In addition to preventing carcass cords, it is possible to improve the durability of the tire and prevent initial elongation from being restricted to an optimum range as a carcass cord.

[Brief description of the drawings]

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

FIGS. 2A and 2B are cross-sectional views 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 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.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metal cord 2 Metal filament 2A Molding filament 3 Straight part 4 Filament bundle

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuo Sakai 650 No. 63 Roy Jarlesan 309, Kamioso-cho, Utsunomiya-shi, Tochigi Prefecture (56) References JP-A-10-110396 (JP, A) JP-A-5-95 33277 (JP, A) JP-A-5-279974 (JP, A) JP-A-8-49177 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) D07B 1/06 B60C 9 / 00 EUROPAT (QUESTEL) WPI / L (QUESTEL)

Claims (3)

(57) [Claims] The present invention comprises 8 to 12 metal filaments having the same diameter and a wire diameter d of 0.15 to 0.30 mm, and all of the metal filaments are in a state of a wave peak before being twisted. A two-dimensionally corrugated shaped filament having a straight portion between the valley and the trough, 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 25 mm without forming a specific core filament while changing the positions of the filaments And a metal cord in which the length of each of the forming filaments contained per unit length (1 m) of the filament bundle before forming is substantially equal. 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 forming filament is twisted and twisted to form the filament bundle. 3. A pneumatic tire using the metal cord according to claim 1 for a carcass layer.