JPH04308287A - Steel cord for reinforcing rubber article - Google Patents

Abstract

PURPOSE:To provide the subject steel cord containing a particular spiral wire, having a specific cross-sectional structure and excellent elongation and flexibility under low load, resistant to the lowering of the cord strength, having stable twist and giving a complete composite material with a rubber material. CONSTITUTION:The objective product is a steel cord 4 composed of 2-6 twisted strands 3 having the same diameter. It contains plural strands 2 having nearly spiral parts 1 satisfying the formula P1=0.1P to 0.7P (P1 is pitch of the spiral part; P is twisting pitch; d1 is outer diameter of the spiral part; d is diameter of the strand) and distributed nearly periodically in the direction of length in such a manner as to contain at least one of the nearly spiral parts on any cross-section of the cord perpendicular to the fiber axis. The steel cord can be produced, e.g. by twisting two spiral strands 2 and one straight strand 3 in such a manner as to contain at least one of the nearly spiral parts on any cross-section of the cord perpendicular to the fiber axis by shifting the spiral- forming parts 1,1 of two strands 2 along the longitudinal direction by one twist pitch.

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 reinforcing rubber products, which is used as a reinforcing material for rubber products such as automobile tires and conveyor belts.

0002

2. Description of the Related Art A large number of steel cords of this type are arranged in parallel and covered with a rubber material, and are used as reinforcing materials for rubber products such as automobile tires and conveyor belts.

[0003] The above-mentioned steel cord has a different twist structure depending on the use of the rubber product to be reinforced. For example, steel cords for reinforcing pneumatic radial tires for passenger cars generally have a 1×n (n=3 to 6) twisted structure, called single-layer twisted structure, as shown in Figures 6 (a) and (b). Steel cords 20 and 21, and steel cords for reinforcing heavy-duty pneumatic radial tires used for trucks, buses, etc., are called bundle-stranded steel cords as shown in Figures 7 (a) and (b). 1×n (n=12, 19, 27
) Stranded structure steel cord 22, 23 or Figure 8 (
k+m, which is called multi-layer twisting as shown in a) to (c),
k+m+n (k=1-3, m=6-9, n=12-15
) Stranded steel cords 24, 25, 26, or m×n (m=3 to 7, n=3 to 7) twisted structures called multiple twists as shown in FIGS. 9(a) and (b) Steel cords 27 and 28 are known.

By the way, when steel cord is used as a reinforcing material for rubber products, the essential conditions are firstly that it has excellent mechanical strength, but also that it has good chemical adhesion to the rubber material. and good rubber penetration into the interior of the steel cord. That is, in order for the steel cord to fully fulfill its role as a reinforcing material for rubber products, it is necessary that it be a complete composite with the rubber material.

However, the steel cord 20~
In No. 28, the individual wires 3 constituting the cord are twisted together in close contact with each other, so when forming a composite sheet of the steel cord and the rubber sheet, the rubber material is inserted into the cavity D inside the cord. It does not penetrate to the depths, but simply covers the outer periphery of the cord, and the above-mentioned cavity D exists continuously over the length of the cord. Rubber products using such steel cords, such as automobile tires,
The adhesion between the rubber material and the steel cord is insufficient, causing the so-called separation phenomenon in which the steel cord and the rubber material separate when the car is running, which significantly impedes the function of the tire and also causes water in the rubber material and the tire to deteriorate. Moisture that has entered through the cut reaches the cavity D inside the steel cord,
It propagates in the longitudinal direction of the cord and corrodes the steel cord, significantly reducing its mechanical strength.

[0006] In recent years, in view of the above circumstances, various steel cords having structures capable of improving the adhesion between the steel cord and the rubber material have been proposed. For example, JP-A-62-234
Publication No. 921 discloses a steel cord 2 having a 1×2 twisted structure in which two strands 3 are twisted together as shown in FIG. 10(A).
9 has been disclosed, and in Japanese Patent Application Laid-open No. 193253/1983,
As shown in FIG. 10(B), a steel cord 32 having a 2+2 twisted structure in which two wire groups 30 and two wire groups 31 having parallel or nearly parallel twist pitches are twisted together is disclosed. , Japanese Unexamined Patent Publication No. 55-90692 discloses that the shape of each strand 3 is made larger than in a normal twisted state, and a gap C is created between each strand 3, as shown in FIGS. 10(c) and 10(d). Steel cords 33 and 34, which are so-called open-stranded cords, are disclosed in which the strands are loosely twisted while being twisted together. A steel cord 35 is disclosed in which a gap C is formed between the strands 3 by thinning out several wires, and a path for rubber material to penetrate into the interior is provided.
Publication No. 103092 discloses a steel in which a gap C is formed between three strands of strands 37 and 38 of the outer layer by increasing the wire diameter of the strands constituting the core 36, as shown in FIG. 10(f). Code 39 is disclosed.

[0007]

[Problem to be solved by the invention] Figures 10 (a) to (a) above
Although the steel cord shown in f) can improve the adhesion to the rubber material to some extent, it is accompanied by the following problems.

In the steel cord 29 having a 1×2 twisted structure shown in FIG. 10(a), there is no cavity D surrounded by the strands, but the contact points between the strands 3 are continuous along the length. This contact point becomes a path for moisture to propagate and corrode the cord. In addition, it tends to cause fretting wear, buckling, etc., and also has problems in that flexibility decreases as the number of strands decreases.

[0009] Furthermore, in the case of the steel cord 32 having a 2+2 twisted structure shown in FIG. It has problems such as being easy to occur and having poor fatigue resistance.

Furthermore, in the steel cords 33 and 34 of open twisted structure shown in FIGS. 10(c) and 10(d),
In order to sufficiently infiltrate the rubber material into the inside of the cord, it is necessary to provide a gap C between each strand 3 of at least 0.01 mm. However, if the gap C is large enough, the free space in which each strand 3 can move becomes large, resulting in uneven twisting in the longitudinal direction, such as deviation of the strands, and buckling when repeated bending stress is applied. tends to occur. Also, this steel cord 3
3 and 34 have large elongation under extremely low loads, which not only results in poor handling workability, but also reduces the gap C due to the tension applied at low loads during composite sheet forming, resulting in steel cords as shown in Figure 6. Similar to 20 and 21, the rubber material may not fully penetrate into the cord.

In the steel cords 35 and 39 shown in FIGS. 10(e) and 10(f), the hollow portion D surrounded by the strands constituting the core 36 still exists.
It does not form a perfect composite with the rubber material, and the former has problems such as a decrease in cord strength due to a decrease in the number of strands, and the latter has problems such as a decrease in flexibility due to an increase in diameter.

The present invention has been made in view of the above-mentioned problems, and its object is to provide a cord with good elongation in a low load range, excellent flexibility, and a twisting method that does not involve a decrease in cord strength. The object of the present invention is to provide a steel cord that can form a complete composite with a stable rubber material.

[0013]

[Means for Solving the Problems] The present invention uses at least two or more curled strands in which substantially spiral-formed portions consisting of small substantially spiral-shaped curls are provided substantially periodically in the longitudinal direction, and the curled strands The purpose is to achieve the above object by optimally arranging the wires as the wires constituting the cord. That is, the present invention provides a steel cord formed by twisting two to six strands of the same wire diameter, wherein the steel cord has strands having approximately periodic spiral-formed portions in the longitudinal direction that satisfy the following formula. The first invention provides a steel cord for reinforcing rubber products, which includes a plurality of steel cords and has at least one substantially spiral-molded portion as described above in any vertical cross section.

P1 =0.1P~0.7Pd1 =(d
+2/100mm) ~ (d+2/10mm) However,
P1 is the twist pitch, P is the twist pitch, d1 is the twist outer diameter, and d is the wire diameter.

[0015] Further, in a steel cord formed by twisting 7 to 27 strands of the same wire diameter, the steel cord has a plurality of strands having approximately periodic spiral forming portions in the longitudinal direction that satisfy the following formula. A second invention provides a steel cord for reinforcing rubber products, which includes the steel cord and includes at least one substantially spirally formed portion around any straight portion of the strands constituting the cord.

P1 =0.1P~0.7Pd1 =(d
+2/100mm) ~ (d+2/10mm) However,
P1 is the twist pitch, P is the twist pitch, d1 is the twist outer diameter, and d is the wire diameter.

Further, a third invention is a steel cord for reinforcing rubber products, which is made by using the steel cord of the first invention as a strand, and twisting a plurality of the strands together.

Furthermore, a fourth invention is a steel cord for reinforcing rubber products, which is made by using the steel cord of the second invention as a strand, and twisting a plurality of the strands together.

[0019] In the first, second, third or fourth invention, the rubber product uses a straight wire other than the wire having substantially spiral molded portions approximately periodically in the longitudinal direction. The reinforcing steel cord is the fifth invention.

[0020] In the above structure, at least two or more strands are required to have substantially spirally formed portions approximately periodically in the longitudinal direction, and these may be used for all the strands constituting the cord. It may be used in combination with a straight strand or a strand having continuous substantially spirally formed portions in the longitudinal direction. When combining with other strands, it is preferable to use straight strands in terms of twisting stability, productivity, and elongation characteristics in a low load range. Note that the straight portion of the wire in the present invention refers to the non-spiral formed portion of the curled wire as well as the straight wire itself.

[0021] In the above structure, the outer diameter of the substantially spiral-shaped curve of the substantially spiral-formed portion is d1 = (d+2/100
mm) to (d+2/10mm) is d+2
/100mm, the rubber material will not penetrate into the steel cord sufficiently during pressure vulcanization, and d+2/1
This is because if it is larger than 0 mm, not only will the stability of twisting deteriorate and fatigue resistance decrease, but also the elongation at extremely low loads will increase.

[0022] Furthermore, the substantially spiral curling pitch of the substantially spiral forming portion is set to P1 = 0.1P to 0.7P because if it is smaller than 0.1P, unreasonable plastic deformation will occur to the strands during curling. This makes the wire more likely to break. In addition, if it is larger than 0.7P, the gap between the strands will decrease due to the tensile force due to the flow of the rubber material during rubber product molding or the ironing force applied to the surface of the steel cord, and the rubber material will not penetrate sufficiently. It is from. In addition, the approximately spiral-shaped habit of the approximately spiral molded part does not require an exact spiral shape, and even if it is simply wavy, it will have the same effect as a spiral shape. It also includes.

[0023]This kind of steel cord is generally employed with d=0.15 to 0.40 mm and P=5 to 20 mm. The twist pitch P in the above configuration means the twist pitch of the steel cord, but in a steel cord with a multi-layer twist or multi-twist structure, it indicates the twist pitch of the layers and strands including the curled strands.

[0024]

[Operation] When the steel cord configured as described above is sandwiched between two rubber sheets and pressure vulcanized, at least one substantially spiral-molded portion is present in any vertical cross section of the steel cord, or Since there is at least one approximately spiral formed part around any straight part of the strands, a minute gap is formed between the strands, and this minute gap becomes a path for the rubber material to penetrate into the steel cord. Infiltrate. In addition, since the approximately spiral forming portions are provided approximately periodically in the longitudinal direction, the elongation under low loads is reduced, and even when mixed with approximately straight strands, the difference in elongation coefficient between the two is small. , there is almost no decrease in relative code strength.

[0025]

Embodiments Hereinafter, embodiments of the present invention will be explained based on the drawings.

FIG. 1 shows a curved strand 2 having approximately spiral molded portions 1 approximately periodically in the longitudinal direction, which is used in the steel cord for reinforcing rubber products according to the present invention. ) is a cross-sectional view. In addition, 1a is the straight part,
P1 is the pitch of the spiral, Pe is approximately the period of the spirally formed part, d1 is the outside diameter of the spiral, d is the wire diameter, and e is approximately the length of the spirally formed part.

[0027] Then, the wire diameter d = 0 of this curled wire 2
．． 28 mm, curl pitch P1 = 1.8 mm, curl outer diameter d1 = 0.38 mm, and spiral molded parts 1 with length e = 8 mm were periodically present in the longitudinal direction at intervals equal to the length e 2. A real curled strand 2 and a straight strand 3 are twisted together at a twisting pitch P=8 mm,
A steel cord 4 having a cross section as shown in FIG. 2(a) was obtained. When twisting each strand together, as shown in FIG. The spiral molded portion 1 was also arranged in such a manner that the spiral molded portion 1 was also present. As a result of covering the steel cord in this example with a rubber material and pressurizing it, the rubber material penetrates into the inside of the steel cord sufficiently, and the rubber material covers the entire circumference of each strand, making it completely A composite with rubber material was obtained.

FIG. 2(b) is a cross-sectional view of a steel cord for reinforcing rubber products according to a different embodiment of the present invention, in which a steel cord 4 is formed by twisting three curled strands 2 together at a twisting pitch P=8 mm. It consists of In addition, the curled strand 2
is the same as in the above example, and the wire diameter d of each wire is
was also set to 0.28 mm. When twisting each strand together, as shown in FIG. Spiral forming part 1 of real wire
was shifted in the longitudinal direction by the twisting pitch, and the spiral formed portion 1 was arranged so that it existed in any vertical cross section of the length of the steel cord. As a result of covering the steel cord of this example with a rubber material and pressurizing and vulcanizing it, a complete composite with the rubber material was obtained. In addition, since the elongation coefficient of each strand is the same, even when a compressive tensile bending load is applied to the steel cord, each strand will have the same elongation, and the steel cord will work as a single unit, reducing the strength of the cord. There is no
It showed good breaking load.

In each of the above embodiments, the curled strand 2
The length e of the spiral forming part 1 is the same as the twist pitch P (
Although the period Pe is set to 2p), it is not limited to this and can be set arbitrarily.

[0030]Also, in the above embodiment, a steel cord having a 1×3 twisted structure, which is a single-layer twisted structure, was shown.
The present invention is not limited to this, but the bundle twisting structure as shown in Fig. 4 (a), Fig. 4 (
Multi-layer twisted structures such as b) and (c) as well as Fig. 4 (d),
Even if the steel cord has a multi-strand structure like (e), a steel cord with good adhesion to the rubber material can be obtained by variously selecting and setting the number and arrangement of the curled strands 2 in the steel cord. Is possible.

In each of the above embodiments, the curled strand 2 can be easily obtained by, for example, biting the strand into a gear partially formed with teeth and twisting the strand. Can be done. In this case, the shape of the spiral can be arbitrarily adjusted by adjusting the shape of the teeth, the number of twists, the winding speed, etc. The curled strand 2 can also be obtained by passing a strand between several pins arranged in a staggered manner and periodically rotating the group of pins about the axis of the strand. In this case, the spiral shape can be arbitrarily adjusted by adjusting the diameter of the pins, the interval between the pins, the rotation speed, the rotation period, the winding speed, etc.

Next, a method for manufacturing the curled strand will be explained in detail. First, as shown in FIG. 5(a), a straight strand 3 is inserted between a pair of gears 5, 5 which face each other and partially have teeth, and then wound around a roller 6 several times. The wire was guided to a buncher type twisting machine 7 and wound onto a reel 8 to obtain a curled wire 2. As an example of a method for obtaining a steel cord from this curled strand 2, the case shown in FIG. 3 were let out from each reel 8, collected by a collecting voice 9, guided to a buncher type twisting machine 7, and twisted together to obtain a steel cord having a cross section as shown in FIG. 2(A). By the way, a plurality of the gears 5, 5 are arranged in parallel, each strand is meshed between the gears 5, 5, and the gear itself is rotated in the circumferential direction of the strand to obtain a curled strand, A steel cord can be manufactured in one step by gathering these curled strands or the curled strands and other strands and guiding them to a twisting machine.

Next, regarding the steel cords for reinforcing rubber products of each of the above-mentioned Examples, conventional examples, and comparative examples, we will examine the permeability of the rubber material, 5 kg load elongation (initial load elongation), breaking load (breaking strength), fatigue resistance, and When handling workability was evaluated,
The results shown in Table 1 below were obtained. In addition, all the wires that make up each steel cord have a carbon content of 82% by weight.
It is made of the same wire material as , and its surface is plated with brass.

[0034] During this evaluation, the penetrability (%) of the rubber material
In this method, each steel cord was embedded in a rubber material with a tensile load of 5 kg applied, and after vulcanization, the steel cord was taken out, and the steel cord was disassembled and a certain length was observed.
The ratio of the length with evidence of contact with the rubber material to the observed length is expressed as a percentage. Note that this value must be 60 or more.

[0035] If the 5% load elongation is 0.40% or less, handling workability and twisting stability can be maintained.

[0036] Fatigue resistance was determined by embedding a plurality of steel cords in a rubber sheet, and using this sheet, using a three-pulley bending fatigue tester, the number of repetitions until breakage through fretting wear, buckling, etc. was determined. The results are shown in Experiment No.
The value of 2 was set as 100 and expressed as an index.

[0037] Handling workability is determined when manufacturing steel cords.
This shows the handling workability when embedding rubber sheets and when molding tires, etc. Experiment No. Those that were very inferior to the steel cord No. 2 were evaluated as ×, those that were slightly inferior were evaluated as △, and those that showed no difference were evaluated as ○.

[0038]

[Table 1]

The following points are clear from Table 1.

Experiment No. 1 steel cord is 1×2
It is a steel cord with a twisted structure, and has good rubber material penetration, but because the number of strands is small, the breaking load is low, and the fatigue resistance is poor.

Experiment No. Steel cord No. 2 is a steel cord with a 1×3 twisted structure in which all the wires are in close contact with each other, and there is no infiltration of the rubber material at all.

Experiment No. The steel cord No. 3 has an average forming rate ((Steel cord diameter when each strand is twisted together with a gap provided/Steel cord diameter when each strand is twisted closely together) x 100) 130 % open-twisted cord, and is excellent in rubber material penetration and fatigue resistance, but has a large 5 kg load elongation (initial load elongation) and is inferior in handling workability.

Experiment No. 4~No. 7 is a steel cord with a 1×3 twisted structure having curled strands 2, but the number of curled strands 2 and the substantially spiral curl shape (curl pitch P1, curl outer diameter d1) are different from those of the present invention. It is inferior in the penetrability of the rubber material, fatigue resistance, and/or handling workability.

As is clear from the above comparative test, the steel cord of the present invention, Experiment No. 8~No. 10
Only the steel cord satisfies all of the permeability of rubber material, 5 kg load elongation (initial load elongation), breaking load (breaking strength), fatigue resistance, and handling workability.

[0045] The above evaluation is only for the steel cord with a 1×3 twisted structure, which is a single layer twisted structure.
Results showing a similar tendency were obtained not only for steel cords having bundle-stranded, multilayer-stranded, and multiple-stranded structures.

[0046]

[Effects of the Invention] Since the steel cord for reinforcing rubber products of the present invention has the above structure, when covered with a rubber material, the rubber material can easily penetrate into the steel cord through the gaps created between the strands, and the steel Since the spaces between each of the wires constituting the cord can be reliably covered with the rubber material, the rubber material and the steel cord can be reliably bonded.

Furthermore, since the elongation is small under extremely low loads, workability is greatly improved. For example, when winding a steel cord onto a reel or embedding it in a rubber sheet, if the elongation is large under extremely low loads, the reel may become punctured or the rubber sheet may wrinkle. This will be resolved.

Furthermore, since the steel cord is twisted in the longitudinal direction stably, buckling is less likely to occur and fatigue resistance is good. Moreover, since it has good breaking load and flexibility, it has excellent effects such as further improving the functions of rubber products such as tires and conveyor belts.

[Brief explanation of the drawing]

FIG. 1 shows a curved strand used in the steel cord for reinforcing rubber products of the present invention, in which (a) is a side view and (b) is a cross-sectional view.

FIGS. 2A and 2B are cross-sectional views showing examples of the steel cord for reinforcing rubber products of the present invention, respectively.

[Figure 3] (A) and (B) are respectively shown in Figure 2 (A) and (B).
FIG. 2 is a layout diagram of each strand for explaining the twisted structure of the steel cord.

FIGS. 4A to 4E are cross-sectional views showing different embodiments of the steel cord for reinforcing rubber products of the present invention.

5A and 5B are schematic configuration diagrams for explaining an example of the method for manufacturing a steel cord for reinforcing rubber products according to the present invention, respectively; FIG.

FIGS. 6A and 6B are cross-sectional views showing conventional steel cords for reinforcing rubber products having a single-layer twisted structure; FIGS.

FIGS. 7A and 7B are cross-sectional views respectively showing steel cords for reinforcing rubber products having a conventional bundle-twisted structure.

FIGS. 8A, 8B, and 8C are cross-sectional views respectively showing a steel cord for reinforcing rubber products having a conventional multi-layer twisted structure.

FIGS. 9A and 9B are cross-sectional views showing conventional steel cords for reinforcing rubber products having a multi-strand structure; FIGS.

FIGS. 10A to 10F are cross-sectional views showing conventional steel cords for reinforcing rubber products, each of which is said to have been improved.

[Explanation of symbols]

1... Spiral molded portion 1a... Straight portion 2... Curved wire 3... Strand wire 4, 20, 21, 22, 23, 24, 25, 26, 27
, 28, 29, 32, 33, 34, 35, 39...Steel cord 5...Gear 6...Roller 7...Buncher type stranding machine 8...Reel 9...Collective voice 30, 31...Flat wire group 36...Core 37, 38 ...outer layer

Claims (5)

[Claims] Claim 1: A steel cord formed by twisting two to six strands of the same wire diameter, the steel cord having a plurality of strands having approximately spiral formed portions approximately periodically in the longitudinal direction that satisfy the following formula. A steel cord for reinforcing rubber products, in which at least one of the substantially spirally formed portions is present in any vertical cross section. P1 = 0.1P ~ 0.7P d1 = (d+2/100mm) ~ (d+2/10m
m) However, P1 is the twisted pitch, P is the twisting pitch, and d
1 is the curved outer diameter, and d is the wire diameter. 2. A steel cord formed by twisting 7 to 27 strands of the same wire diameter, wherein the steel cord has a plurality of strands having approximately periodic spiral forming portions in the longitudinal direction that satisfy the following formula: A steel cord for reinforcing rubber products, including the main wire and having at least one or more substantially spirally formed portions around any straight portions of the wires constituting the cord. P1 = 0.1P ~ 0.7P d1 = (d+2/100mm) ~ (d+2/10m
m) However, P1 is the twisted pitch, P is the twisting pitch, and d
1 is the curved outer diameter, and d is the wire diameter. 3. A steel cord for reinforcing rubber products, which is made by using the steel cord according to claim 1 as a strand, and twisting a plurality of the strands together. 4. A steel cord for reinforcing rubber products, which is made by using the steel cord according to claim 2 as a strand, and twisting a plurality of the strands together. 5. The steel cord for reinforcing rubber products according to claim 1, wherein straight strands are used as the strands other than the strands having substantially spiral molded portions substantially periodically in the longitudinal direction.