JPH09279492A - Steel cord for reinforcing rubber product and radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a steel cord, comprising each wire having a small wave postforming having a smaller pitch and height than those of a wave postforming by laying thereof and excellent in fatigue resistance and rubber permeability and suitable for a radial tire by simultaneously laying plural wires at the same laying pitch in the same direction. SOLUTION: This steel cord for reinforcing a rubber product is prepared by simultaneously laying (n)×wires 1 to 4 [(n) is 3-7] having a galvanized or a brass plated surface and 0.22-0.40mm diameter at the same laying pitch in the same direction. The resultant steel cord has >=30mm laying pitch P thereof, parts (a) where the wires 1 to 4 do not mutually cross and parts (b) where the wires 1 to 4 mutually cross present nearly periodically in the cord longitudinal direction and >=0.5 part (b) where the wires 1 to 4 mutually cross based on the one laying pitch length P and the wires have small wave postforming (w] of 0.1P to 0.6P pitch and 0.03-0.20mm height based on the cord laying pitch length P. The steel cord is used in at least a part of belt parts to from a radial tire for automobiles.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel cord and a radial tire used as a reinforcing material for rubber products such as a conveyor belt and a radial tire for automobiles.

[0002]

2. Description of the Related Art As a reinforcing material for rubber products such as conveyor belts and radial tires for automobiles, steel cords made by twisting multiple high-strength wires plated with zinc or brass are used. There is. In the above rubber product, a large number of the steel cords are arranged in parallel in the rubber to form a reinforcing layer, and one or a plurality of the reinforcing layers are stacked and used. For example, in radial tires for automobiles, as a steel cord for belt reinforcement for passenger cars, strands of 1 × 4 or 1 × 5 whose cross section is shown in FIGS. 5 (a) and 5 (b) are twisted loosely. Steel cords such as a combined single-layer twist structure are used. On the other hand, for trucks and buses, for example, as shown in the cross section of FIG. 6, 1 × is formed by winding 6 large-diameter wires around a core strand formed by winding 3 small-diameter wires. A steel cord with a 3 + 6 two-layer twist structure is used.

The diameter of the wire used in the above-mentioned steel cord is 0. 0 in the single-layer twist structure for passenger cars.
It is about 23 to 0.25 mm, and about 0.32 to 0.38 mm in the second layer (side) of the two-layer twist structure for trucks and buses. On the other hand, the twist pitch length is about 10 to 14 mm in the single-layer twist structure for passenger cars, and about 16 to 18 mm in the second layer of the two-layer twist structure for trucks and buses.

Since the above steel cords need to function as a reinforcing material in rubber together with all the element wires constituting the steel cords, the cohesiveness of the cords (difficulty of separation)
Good fatigue resistance to bending and bending is required. Further, since the steel cord constitutes a composite with the rubber, in order to maintain the integrity with the rubber, the structure is such that the rubber can permeate well into the steel cord during the vulcanization process of tire manufacturing. It is necessary to have That is, by filling the inside of the steel cord with rubber, it is possible to sufficiently exert the function as a composite body, prevent water from propagating inside the cord, and ensure corrosion resistance. However, in the single-layer steel cord of FIG. 5, the strands are loosely twisted together, so the shape is unstable and the fatigue resistance to bending is also unstable. Although good, in practice, when tension is applied to the cord, the wires tend to come into close contact with each other and the gap tends to disappear, so there is a problem in that some rubber does not easily penetrate to the central portion.
On the other hand, the two-layer steel cord shown in FIG. 6 has a good cohesiveness as a cord and good fatigue properties, but in the core strand, since the strands are in close contact with each other, the permeability of rubber is low. There was a problem of being bad. Further, since this steel cord is manufactured in two steps, there is a problem that the manufacturing cost becomes high.

By the way, recently, the structure of the steel cord tends to be simplified for cost reduction. That is, attempts have been made to make the steel cord simpler in structure, such as reducing the number of strands forming the steel cord or changing the structure from a two-layer structure to a single-layer structure. As an example, consider a structure in which a plurality of straight or continuous small wavy strands are bundled in parallel and then one or more strands are wrapped around this bundle in a spiral shape. Has been.

Since this steel cord is manufactured by bundling a plurality of strands and then wrapping the strands on the strands, there is a problem in that the bundled strands are easily disordered and uncoordinated.
That is, from the viewpoint of the productivity of the cord, it is better that the wrapping pitch is long, but if it is larger than the twisting pitch of a normal cord, the strands tend to swell like a cage when the cord is bent, and Even if it returns to a straight line, it may be difficult to restore the original wire. Furthermore, since this steel cord is not twisted and because the bundled wires are indented by lapping, fatigue resistance is inferior to the steel cord that was twisted at a relatively short pitch. There are drawbacks. In addition, since this steel cord has wrapping, there is a problem that the cord diameter becomes large. That is, when the cord diameter is large, the rubber thickness of the reinforcing layer is inevitably increased when manufacturing a tire, and the amount of rubber used is increased, which is economically unfavorable. In view of such characteristic problems and productivity, further improvement is required as an alternative to the conventional code.

[0007]

SUMMARY OF THE INVENTION The present invention was made by research to solve the above problems, and its purpose is to improve cohesion, fatigue resistance and rubber penetration. The object is to provide a simplified steel cord which is good and which is particularly cheap to manufacture. Another object of the present invention is to provide a radial tire for automobiles which is low in cost and has good performance.

[0008]

In order to achieve the above-mentioned object, the present invention provides n pieces (n = n = 0.22 to 0.40 mm in diameter).
In the steel cord of 1 × n structure in which the strands 3 to 7) are simultaneously twisted in the same direction at the same twist pitch, the twist pitch length of the cord is 30 mm or more, and the strands intersect in the longitudinal direction of the cord. Parts exist almost periodically,
In addition, each of the wires of the cord has a continuous small wave pattern in which both the pitch length and the height are smaller than the wavy pattern caused by twisting. More preferably,
The number of intersections between the strands is 0.5 times or more per twist pitch of the cord on average, and the pitch length of the continuous wavelet of the strands is 0.1 with respect to the pitch length P of the cord twists.
P-0.6P and its height is 0.03-0.20mm
In the range. The present invention also provides a radial tire for passenger cars or trucks / buses in which the steel cord is used to reinforce the belt portion.

In the steel cord of the present invention, since the wires are simultaneously twisted in the same direction at a very long pitch of 30 mm or more, the manufacturing cost is very low. That is, since the twisting pitch is more than twice as long as the conventional one, the cord production amount per one rotation of the twisting machine is more than twice as much as the conventional one. And, even though the cords are twisted at a very long pitch, the strands of the cord have a continuous wave pattern with a smaller pitch and height than the wave pattern caused by the twisting. When subjected to compression bending, the stress can be relieved by expansion and contraction to maintain fatigue resistance, and since the gaps are created between the strands due to the wavy unevenness, ensure rubber permeability as well. You can In addition, since the intersecting parts of the wires are intentionally made to exist substantially periodically in the longitudinal direction of the cord, the wires are entangled with each other, which prevents loosening and maintains good cohesiveness of the cord. It is possible to efficiently exert the reinforcing effect.
At the same time, since the gap is created by the intersection, it is possible to further improve the rubber permeability. In addition, since it is not necessary to wrap the outer circumference, the cord can be made relatively compact.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 and 2 schematically show an example of the steel cord of the present invention. 1, 2, 3, in the drawing
4 is a wire having a diameter of 0.22 to 0.40 mm, the surface of which is zinc-plated or brass-plated, and four wires are twisted in the same direction at the same twist pitch of 30 mm or more at the same time. It has a layered structure. The four strands 1,
Nos. 2, 3 and 4 are twisted together with a long pitch length P which is about twice as long as that of a conventional steel cord using the four strands of FIG. 5 (a). Then, in the longitudinal direction of the cord, a portion a where the strands do not intersect and a portion b where the strands intersect are repeatedly formed. In the portion B where the strands do not intersect with each other, the strands 1, 2, 3, 4 are in line contact with each other, and in the intersecting portion B, at least two strands are in point contact with each other. FIG. 2A shows a state before the strands intersect, and FIG. 2B shows an example of a state after the strands intersect.

The intersection of the strands may be formed so that only one strand moves so as to be exchanged and formed only between one or more adjacent strands, but preferably two or more strands. From the viewpoint of balance, it is preferable that the lines are formed by moving so as to alternate with the lines or randomly. The intersecting portions (b) are made to exist substantially periodically in the cord longitudinal direction, and the frequency thereof is at least 0.5 times per twist pitch on average.

Further, each of the wires 1, 2, 3 and 4 is separated from the twisted wavy pattern W as shown in FIG. , A continuous small wave w with a pitch length p smaller than the twisted pitch P and a height h smaller than the twisted wave height H.
In the longitudinal direction of the wire. Specifically, the continuous small wave w has a pitch length p of a cord twisted pitch length P.
Is set in the range of 0.1 P to 0.6 P, and the height h thereof is set in the range of 0.03 to 0.20 mm. The shape of the continuous wave pattern w of the wires 1, 2, 3, 4 is basically spiral, but may be two-dimensional flat in some cases. The steel cord of the present invention is formed with a space s communicating with the inside thereof everywhere due to the above-described crossing portions B of the wires and the continuous small wave w.

FIG. 3 schematically shows another example of the steel cord according to the present invention. In this example, seven strands 1, 2, 3, 4, 5, 6, 7 are used, each strand is subjected to a continuous wave w, and they are arranged in the same direction by 30 waves.
It is twisted at the same twist pitch at the same time with a length of mm or more, and intersecting portions due to the exchange of the strands are formed almost periodically in the cord longitudinal direction. FIG. 3A shows a state before the strands intersect, and FIG. 3B shows an example of a state after the strands intersect. Since other configurations are the same as those in the above-described embodiment, the description thereof will be omitted to avoid duplication.

Next, the reasons for limitation of the present invention will be explained. First,
The steel cord according to the present invention is basically a steel cord having a 1 × n structure in which 3 to 7 strands are simultaneously twisted in the same direction at the same twist pitch. The upper limit of the number of strands is 7
I chose the book because it does not fit into the simplification of the code. The reason why the cord twisting pitch is 30 mm or more is that if the twisting pitch is shorter than that, the difference from the twisting pitch length of the conventional cord is reduced and the productivity is not significantly improved. Further, it is preferable that the intersection B between the wires exists 0.5 times or more per one twist pitch P of the cord. If the crossing frequency is lower than this, the cords will be greatly dislocated, which is not preferable in terms of the cohesiveness of the cords. It should be noted that if the number of intersections (B) is too large, the twisting of the cord will be disturbed and the fatigue resistance will be deteriorated. Therefore, the upper limit is preferably about 4 times per twist pitch P.

The pitch length p of the continuous wave pattern w of the wire is 0.1P to the pitch length P of the cord twists.
If the pitch length is less than 0.1P, the wave processing becomes so tight that the strand strength is likely to be lowered and the fatigue resistance is lowered. This is because when the tension is applied during vulcanization, the small wave curl of the strands is likely to extend, which reduces or eliminates the gaps and reduces the rubber permeability. The height h of the continuous small wave w of the wire is set to 0.03 to 0.20 mm,
If it is less than 0.03 mm, the improvement of fatigue resistance will be insufficient, and the created gap will be small, resulting in a decrease in rubber permeability. If it exceeds 0.20 mm, the cord tends to lose its shape and This is because the uniformity decreases and the fatigue resistance also decreases. The steel cord of the present invention is not limited to the case where all the strands have the same diameter, and may include one or more strands having different diameters.

The above-described steel cord of the present invention can be manufactured, for example, by the following device and method. That is, a wiring board, a wire tension variation device that causes the wires to intersect with each other, and a wire at the upstream side of the hollow shaft on the inlet side of the cradle of the buncher type wire twisting machine (twist wire twisting machine). A wire twister (having the same number as the number of strands) and a molding device for imparting a small wave pattern are sequentially arranged, and a supply bobbin for winding the strands is provided upstream of this. Here, the wiring board has a number of wire insertion holes equal to or larger than the number of wires arranged at equal intervals and on the same circumference. The strand tension changing device has a plurality of rotatable eccentric guide rollers arranged in a direction perpendicular to the line through which the strand passes. As the wire twister, one in which three rotatable rollers are attached at intervals to a plate-shaped rotating body is used. As a typing device,
A plate-shaped, conical-shaped, or cylindrical base having three to five pins attached in a zigzag or linear shape is used. Each embossing device is fixed in position, and each wire twister is revolved around the strand in the same direction as the rotation direction of the bow of the wire twisting machine. In order to obtain this revolution, the power from the twisting machine may be guided through the clutch and the transmission, and the rotating bodies themselves may be linked by gears, timing belts, or the like.

In the production of the cord, the strands of wire are drawn from each supply bobbin, each strand of wire is guided to a wire twister after passing through a pin of a molding device, and guided by a roller on the inlet side of the strand to form a central roll. After winding it around the wire, guide it with a roller on the exit side, then guide each wire to a predetermined eccentric guide roll of the wire tension variation device, and further penetrate each wire into each insertion hole of the wiring board. ,
Collected in a voice, guided from the guide roll through the bow through the hollow shaft of the twisting machine, guided from the other guide roll to the overtwisting machine through the hollow shaft, and guided to the winding bobbin through the capstan or the like. If the hollow shaft is driven in this state to rotate the bow and each wire twister rotates itself about the wire passing line at a required ratio with this, the wire can pass through the pins of the molding device. Gives a continuous small wave habit. Further, in this state, the wire is sent to the eccentric roller which is performing the crank motion of the tension changing device, and the tension of the wire changes here. After that, it is sent to the voice through the wiring board and becomes a bundle, and each strand is twisted the first time in the process of reaching from the hollow shaft to the guide roller. The intersection is formed by the replacement of the. Further, the wire is twisted a second time in the process of reaching the hollow shaft from the guide roller on the opposite side, and then wound up through a supertwisting machine and a capstan etc., and becomes a steel cord according to the present invention. .

Next, specific examples of the present invention will be shown. Example 1 Using four strands having a diameter of 0.25 mm and having a surface plated with brass, a steel cord was produced by the above twisting machine. Strand pitch length, degree of small wavy (spiral) of the wire,
Also, three types of steel cords having different intersecting frequencies of the strands were manufactured and named as Examples 1 to 3. Also, using the same four strands of wire as above, simply bundle them in parallel, and make a cord by spirally winding a single strand of brass with a diameter of 0.15mm at a pitch of 10mm. Comparative Example 1 was obtained. Similarly, the above diameter 0.2
A 1 × 4 loose open cord was manufactured by using a 5 mm strand, which was taken as Conventional Example 1. Table 1 shows these characteristics.

Concrete Example 2 Similarly, seven strands having a diameter of 0.35 mm, which are brass-plated on the surface, are used, and the twist pitch length, the degree of small wavy (spiral) of the strands, and the number of strands Three types of steel cords having different crossing frequencies were manufactured and named as Example 4 to Example 6. In addition, a cord was prepared by simply bundling the same 7 strands of wire as described above in parallel, and spirally winding one strand of 0.15 mm in diameter of Example 1 around it with a pitch of 12 mm. And In addition, a strand pitch of 10 mm is obtained by using three strands of 0.20 mm in diameter plated with brass on the surface.
To produce a 1 × 3 core strand, and around this core strand, the same strand of 0.35 mm in diameter as in the above embodiment is twisted in the same direction as the core strand to produce a 1 × 3 + 6 steel cord. Conventional example 2 is used. The characteristics of these conditions and cords are shown in Table 2.

[0020]

[Table 1]

[0021]

[Table 2]

In Tables 1 and 2, the term "cohesiveness" means that the cord is cut at a right angle to the longitudinal direction with pliers to determine the degree of dispersion of the strands.
Δ: Medium, X: Large. "Rubber permeability" means vulcanizing one cord in rubber to prepare a sample, then taking out the cord in the rubber, disassembling this cord in the longitudinal direction, and visually observing the degree of penetration of the rubber into the cord. Observe at
It is judged that 100% is completely permeated. “Fatigue resistance” means that one cord is vulcanized in rubber and strip-shaped samples are arranged in a zigzag pattern over three rolls with a constant diameter, and a tensile load of 10% of the breaking load is applied to the cord. The results are obtained by repeatedly moving the roll to the left and right to repeatedly bend the sample and measuring the number of repetitions until the cord breaks. Table 1 shows Conventional Example 1 and Table 2 shows Conventional Example 2. Each is represented by 100 as an index.

As is clear from Tables 1 and 2, especially in Examples 1 to 6, although the cord twist pitch is remarkably long, the crossing of the strands and the continuous wave pattern are appropriate, so that the cohesiveness, The rubber penetration and fatigue resistance are achieved in a well-balanced manner, and the properties are equal to or higher than those of the practical examples 1 and 2 of the related art. On the other hand, in Comparative Examples 1 and 2, although the cord configuration is simple, cohesiveness, rubber permeability,
Fatigue resistance is poor. Although the cord characteristics of the conventional examples 1 and 2 are equivalent to those of the example, the cost is high because the cord twist pitch length is shorter than that of the example.

[0024]

According to the first aspect of the present invention described above, although the cords are twisted with each other at a very long twist pitch, the cords have good cohesiveness, fatigue resistance and rubber penetration. Moreover, since the productivity is remarkably high, the excellent effect that the steel cord which can be manufactured at a low cost can be provided is obtained. According to the second aspect, the excellent effect that the cohesiveness of the cord is particularly good, and the fatigue resistance and the rubber permeability are also good can be obtained. Claim 3
According to the above, an excellent effect that a radial tire for an automobile with low cost and high performance can be obtained is obtained.

[Brief description of drawings]

FIG. 1 is an enlarged side view showing a first embodiment of a steel cord according to the present invention.

2A and 2B are explanatory views schematically showing cross sections at different positions in the first embodiment.

3 (a) and 3 (b) are explanatory views schematically showing cross sections at different positions in the second embodiment of the steel cord according to the present invention.

FIG. 4 is a schematic enlarged side view of one strand of wire taken out by disassembling the steel cord according to the present invention.

5A and 5B are enlarged cross-sectional views of a conventional loose open type steel cord.

FIG. 6 is an enlarged cross-sectional view of a conventional two-layer structure steel cord.

[Explanation of symbols]

 1 to 7 Element w w Continuous wave pattern s Gap Part where wire does not intersect Ro Part where wire intersects P Cord twist pitch length p Cord pitch wave length H Cord twist height h Continuous Small wave height

Claims (3)

[Claims] 1. n pieces (n having a diameter of 0.22 to 0.40 mm)
= 3 to 7), the steel cord having a 1 × n structure in which the strands are simultaneously twisted in the same direction at the same twist pitch, the twist pitch length of the cord is 30 mm or more, and the strands are It is characterized in that the intersecting portions are present in a substantially periodic manner, and that each of the strands of the cord has a continuous wave pattern in which both the pitch length and the height are smaller than the wave pattern caused by twisting. Steel cord for reinforcing rubber products. 2. The number of intersections between the wires is 0.5 times or more on average per twist pitch of the cord, and the pitch length of the continuous wave pattern of the wires is relative to the pitch length P of the cord twists. 0.1P-0.6P and its height is 0.03-
The steel cord for reinforcing a rubber product according to claim 1, wherein the steel cord is in a range of 0.20 mm. 3. A radial tire for an automobile, wherein the steel cord according to claim 1 or 2 is used to reinforce at least a part of a belt portion.