JPH09209282A - Steel cord for reinforcing tire and radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a steel cord for reinforcing tires, excellent in rubber permeability, durability and compression resistance in the axial direction, by twisting plural wires provided with a small wave shape in the same direction in the same twisting pitch at one time. SOLUTION: One of wires 1-6 previously provided with a small wave shape 10 having a pitch (p) shorter than a twisting pitch P of a cord is laid at a core part and the other five wires are arranged around the core wire and twisted in the same direction in the same twisting pitch P at one time to give the objective steel cord having the ratio p/P of the pitch (p) of the spiral small wave shape 10 to the twisting pitch P of the cord of 0.25-0.55, the ratio h/d of the small wave height (h) to the wire diameter (d) of 1.05-1.50, the mutual crossing frequency of the wires 1-6 of 0.5-3.0 times per twisting pitch P in which both parts in which the wires 1-6 do not cross in the length direction of the cord and gaps (s) exist and parts in which the wires cross coexist. The cord is used for reinforcing a belt part to form the objective radial tire.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to passenger cars and trucks.
The present invention relates to a steel cord used to reinforce a tire of a vehicle such as a bus and a radial tire using the steel cord.

In radial tires, steel cords are used as reinforcing materials in the belt portion of passenger car tires and in the belt portion and carcass portion of truck and bus tires. Among them, the steel cord used for reinforcing the belt portion is required to have high rigidity and compression deformation resistance, and further, it is required that the rubber penetrates and adheres well to the inside of the cord. A tire using a steel cord that satisfies these requirements can sufficiently exhibit its function as a rubber composite. That is, due to its high rigidity, it is possible to enhance the steering stability of the vehicle during traveling, and especially when the steering wheel is turned, a high compressive force is applied to the cord in the axial direction, but the deformation resistance against this is also great. It becomes a thing. Also, since rubber penetrates inside the steel cord, when the tire steps on a foreign object such as a metal piece and the flaw reaches the steel cord inside, rainwater that invades from the flaw propagates inside the steel cord. Therefore, it is possible to prevent the progress of rust and avoid the separation between the steel cord and the rubber.

As a steel cord used to reinforce such a belt portion, conventionally, in a passenger car tire, the strands are twisted loosely into a cross-sectional shape as shown in FIGS. 1 (a) (b) (c). An open type having an n structure is known. On the other hand, a steel cord having a 3 + 6 structure having a cross-sectional shape as shown in FIG. 2 is often used for truck / bus tires. In the former open type steel cord, the wires are twisted loosely and a gap is provided between the wires to allow rubber to enter. However, since external force is applied to the cord during vulcanization during tire manufacturing,
With such a cord configuration, there is a problem that the strands are likely to move and the gap between the strands is likely to change, and it is difficult to obtain stable rubber penetration. Also, since this type of steel cord has a coreless structure with a large space in the center of its cross section,
The rigidity of the cord was insufficient, and it tended to bulge like a basket when a load was applied from the axial direction, making it difficult to resist compression. Further, when the tire steps on a metal piece or the like, it easily penetrates through the cord and there is a problem in terms of resistance to external damage.

On the other hand, the latter steel cord having a 3 + 6 structure has two twisting steps in its production. That is, first, three small-diameter wires are twisted together to form a core strand, and then six relatively large-diameter wires are tightly twisted around this to form a cord.
There is a drawback that the manufacturing cost becomes high. In terms of performance, due to the above-mentioned diameter of the strands, the six strands on the side are tightly twisted around the core strand formed by twisting the three strands, but a gap is formed between the strands. The rubber is designed to enter through this gap. However, since the three strands of the core are tightly twisted together, the rubber can hardly penetrate into the core strand, and rust is generated and propagates due to the penetration of water as described above. It has the drawback of causing a separation phenomenon and shortening the life of the tire.

[0005]

DISCLOSURE OF THE INVENTION The present invention was devised to solve the above-mentioned problems, and its purpose is to have an extremely good and stable rubber permeability, and yet to achieve good results. The purpose of the present invention is to provide an economical steel cord which has excellent durability, rigidity, and axial compression resistance, and is inexpensive to manufacture. Another object of the present invention is to
It is an object of the present invention to provide a long-lived vehicle radial tire that exhibits excellent steering stability and external damage resistance.

[0006]

In order to achieve the above object, the present invention provides one core wire in a core portion and five core wires around the core wire, and arranges each core wire in the same direction and at the same twist pitch. A steel cord with a 1 + 5 structure that is twisted at once, and each strand has a small wavy pitch that is smaller than the wavy pitch of the twist of the cord, and the strands do not intersect in the longitudinal direction of the cord. The structure is such that the intersecting portions are twisted together so as to be mixed. Preferably,
The wave pattern of the small wave of the strand has a spiral shape, and the ratio p / P of the wave pattern pitch p of the small wave pattern and the wave pattern pitch P of the twist of the cord is in the range of 0.25 to 0.55, Further, the ratio h / d of the wave height h of the small wave habit and the wire diameter d is 1.05 to 1.
It is in the range of 50, and the crossover frequency of the wires is in the range of 0.5 to 3.0 times per twist pitch of the cord. Further, the present invention is characterized in that the steel cord is used for reinforcing the belt portion.

[0007]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 3 shows an example of the steel cord of the present invention, and FIG. 4 schematically shows its cross-sectional shape at a 1/4 twist pitch interval. And FIG. 5 has shown the one strand which decomposed | disassembled and took out the code | cord of FIG. 3 and FIG. Reference numerals 1 to 6 are wires, each wire has a diameter of about 0.20 to 0.40 mm, and its surface is brass-plated for good adhesion to rubber in the tire. The wires 1, 2, 3,
4, 5 and 6 are cord twist pitches before twisting
(Wave peculiar pitch of twisting) It has continuous small wave peculiarity 10 with a pitch p shorter than P. And each strand 1 ~
6 is twisted in the same direction and at the same twist pitch P at a time so that there is one strand in the core and five strands around it. By actively and positively exchanging the strands, a portion where the strands intersect and a portion where the strands do not intersect are mixed in the longitudinal direction of the cord.

That is, FIG. 4 (a) shows the wires 1, 2, 3,
4, 5 and 6 are shown as being parallel to each other without intersecting each other, and the strand 1 is the core, around which the strands 2, 3, 4, 5 and 6 are arranged counterclockwise. They are arranged in that order. Then, the cross-sectional position changes from the cross-sectional position (b) and cross-sectional position (c) to cross-sectional position (d).
In (a), the wire 1 located at the center of the cord moves outward from this position so as to divide the space between the wires 2 and 3, while the wire 4 located outside the cord is not filled into the center of the cord. The positions are swapped so that they fall, and the cross-sectional position (e)
In, the cross-sectional position (a) at the beginning of the 1-strand pitch and the wires are completely interchanged. The cross-sectional shape of the cord is disrupted due to the crossing or replacement between the strands existing in the longitudinal direction of the cord, whereby a large gap s is formed between the strands, and moreover, in each of the strands 1 to 6. A gap s is also formed between the strands arranged in parallel without intersecting each other due to the peaks and valleys of the applied small wave habit 10.

In the present invention, first, a steel cord having a structure which can be manufactured by twisting once in order to keep the cost low is provided.
Then, in order to increase the rigidity thereof, a structure with a core in which an element wire is arranged in a substantially central portion of the cord is provided, and a large space portion in the central portion of the cord as in the open twist structure is eliminated. In addition, in order to ensure rubber permeability,
After applying the small wave peculiarity 10 of the pitch p smaller than the peculiar twist pitch P of 6 to the cord, the wires are twisted in the same direction and at the same twist pitch, and the wires may or may not cross each other during the twisting. Replacement,
A gap is provided between the strands by the intersection and the small wave habit 10, and the gap is constrained by the intersection.

The present invention will be described in more detail. Since one element wire is arranged in the core as described above, there is no space in the center of the cord, and a tire using the same steps on metal pieces such as needles. At that time, it becomes a great resistance to penetrate through the cord, and it is possible to obtain a tire with high external damage resistance that is unlikely to cause puncture. However, in a structure with a core of 1 + 5 in which one strand is arranged in the core and five strands are arranged around the core and these six strands are twisted in the same direction and at the same pitch, The core element wire is always specified in the longitudinal direction of the cord because the five element wires are simply twisted around the wire and the core. Therefore, looking at a certain length of cord,
The core wires and the side wires around the core wires have different twisted lengths, and the core wires are shorter than the side wires around them. From this, when a tensile load is applied to the cord, the core strand is more heavily loaded than the side strands, and the core strand breaks first and the breaking load as a cord also increases. It will be low. On the other hand, a vulcanization pressure is applied during vulcanization during tire production, and therefore a tensile load is applied to the cord, and in the initial stage of vulcanization, the rubber flows and an external force such as ironing is applied to the cord. In such a state, the wires forming the cord move, the gap between the wires changes, and stable rubber penetration cannot be obtained.

In order to deal with this, the present invention is to provide a crossed cord in which the strands are interchanged in the collectively twisted cord. The crossing between the strands always requires crossing of the cord outer diameter side strand and the cord center side strand, but in addition to this, there may be crossing between the cord outer diameter side strands, It also includes a case where two or more strands to be crossed with one or more other strands while being parallel to each other. Therefore, in the present invention, the strand that bears the core is not specific,
The strands of the core change and change. For this reason, the twisted lengths of the individual strands of the cord are made uniform, and the individual strands 1 to 6 can be evenly loaded. Further, due to this intersection, the wires and the wires are bound to each other at the intersection. Therefore, even when a compressive force is applied in the axial direction of the cord, it becomes difficult for the wire to bulge like a cage, and the deformation resistance can be improved. Further, this crossing portion has a function of creating a gap between the strands and fixing the gap between the strands against an external force, so that stable rubber permeability can be achieved.

The frequency of crossing the wires is preferably 0.5 to 3.0 times per twist pitch of the cord. The reason is that if the crossing frequency is less than 0.5 times, the rubber permeability is lowered and the compression resistance is also lowered.
This is because if the number of times is greater than 0, the replacement of the strands becomes complicated and the strand lengths may be unbalanced, resulting in a decrease in durability.

In the present invention, each wire is provided with a small wave habit 10 in advance. The wave pitch p of the small wave patterns 10 of the wires 1 to 6 is preferably in the range of 0.25 to 0.55 in the ratio p / P with the twist pitch P of the cord. The reason is p
This is because if / P is smaller than 0.25, it is difficult to carry out the staking process and the strands are damaged by the process, resulting in a decrease in strength and a decrease in durability. Also, p / P
When the value is greater than 0.55, the strands are close to the wavy pattern of the cord twisting, so the strands are likely to move due to external force, and the strands are pushed by the rubber during vulcanization, causing the strands to be biased and the rubber permeability. Is worse. On the other hand, the wave height h of the small wave habit 10 is preferably in the range of 1.05 to 1.50 in relation to the wire diameter d, that is, h / d. The reason is that when h / d is less than 1.05, the gap between the strands is insufficient and rubber penetration is insufficient, and when h / d is greater than 1.50, the shape of the cord is This is because it is not stable, the load is not evenly applied to each strand, and the breaking load of the cord is reduced.

Next, a method for manufacturing the steel cord of the present invention will be described. FIG. 6 and FIG. 7 show an example thereof, in which 15 is a buncher type twisting machine main body, a voice 14 and a wiring board 13 are arranged upstream of the buncher type twisting machine main body, and a strand wire replacement control device 12 and a wire are arranged upstream thereof. A twister 11, a fixed preformer 9 and a supply bobbin 8 are arranged. In manufacturing, each wire 1, 2, 3, 4, 5,
6 are respectively fed from the supply bobbin 8, first passed through the fixed preformer 9 and the wire twister 11, and then the guide roll 12 of the wire replacement control device 12.
It is guided to the eccentric roll 12d via a, 12b, 12c.
Then, after passing through the guide roll 12e, the wiring board 13 having the wire insertion holes on the concentric circles is passed through, and after each wire is converged on the voice 14, it is introduced into the twisting machine body 15 and twisted here. It fits.

Here, the fixed preformer 3 is mounted on the plate.
One to five pins are attached, and the wire twister 11 is composed of three rotatable rollers attached to the plate. The wire is guided by the roll on the entrance side,
Further, it is wound around the central roll 2 to 3 times, and is guided by the roll on the exit side, and the wire replacement control device 12
Is guided to the entrance guide roll 12a. Since the wire twister 11 revolves around the axis of the strands, each strand is given a spiral wavelet when passing through the fixed preformer 9. Each strand is further guided to the eccentric roll 12d through the respective guide rolls 12a, 12b, 12c of the exchanging device 12. As shown in FIG. 7, the eccentric roll 12d has twelve grooves 121 of the same depth formed at equal intervals on a body 120 having a predetermined diameter D ₁ .
Moreover, the body portion 120 is eccentrically formed in a crank shape with respect to the center line CL for each predetermined length, and the six eccentric roll portions 122a, 1
22b, 122c, 122d, 122e and 122f are formed. Therefore, the eccentric roll portion is cranked by the rotation of the body portion 120, and each wire passed through the eccentric roll portion undergoes a change in tension here, and the voice 14 at the twisted end
The cords of the present invention are manufactured by twisting the individual strands in a stranding machine while causing the strands to be exchanged at the inlet of the cord. The small wave habit 10 of the wire is preferably spiral, but it may be two-dimensional depending on the case. In this case, a pair of meshing gears may be used instead of the fixed preformer and the wire twister as described above, and the wire may be passed between them.

[Specific Example] Next, the wire diameter, twist pitch, p
Steel cords were prepared by varying / P, h / d and strand crossing frequency. The results of comparison of the characteristics of the steel cord under the conditions of the present invention with those of the comparative example and the conventional example are shown in Tables 1 and 2. Table 1 shows examples and comparative examples of steel cords for reinforcing belts of passenger car tires and conventional 1 × 5 open type cords. In addition, since the number of strands of the present invention is 6 as compared with 5 of the conventional example, and the breaking load of the cord is different, Example 3 uses the small diameter strand 0.23 mm to change the cord breaking load to the conventional example. It suits. Table 2 shows steel cords for tires for trucks and buses, which are steel cords for reinforcing belts, having an example diameter of 0.35 mm, comparative examples, and a conventional 1 × 3 + 6 structure (however, the core and the side have different twisting directions). Shows the characteristics of. Again, in order to match the breaking load with the cord of the conventional example, the wire diameter of 0.38 is used in Example 6.
mm.

In Tables 1 and 2, "bending rigidity" is the length.
Given a given bending angle for a 70 mm code sample,
The magnitude of the moment required for this is measured, and the conventional example is represented as 100. For "compression resistance", a cord sample was placed in the center, and cylindrical rubber (20 mmφ x 30 mmL) vulcanized under 100 gr tension was compressed by 3% from the top and bottom, and the shape of the cord at that time was examined using X-rays. The one with the cord that opens like a basket is ×, and it is slightly open △
The one that was not opened was marked as ◯. "Rubber penetration" is a 100 point method in which the cord was embedded in rubber under 100gr of tension, vulcanized, and then the cord was decomposed into its longitudinal length to visually inspect the rubber penetration inside the cord. . "Durability" is that a cord sample is embedded in rubber and vulcanized, and a strip-shaped test body is placed on a testing machine with three rolls with a diameter of 25 mm. The roll is shaken left and right, and repeatedly bent under a specified load. Was given and the number of times until the cord was broken was measured, and the conventional example was expressed as 100. Small wave pitch p of wire
And the wave height h are obtained by disassembling the cord, taking out the wire, and actually measuring it.
I asked.

[0018]

[Table 1]

[0019]

[Table 2]

As is clear from Table 1 and Table 2, Example 1
All of # 6 to # 6 have good rubber permeability, bending rigidity, compression resistance, and durability. Generally, the bending rigidity becomes higher as the diameter of the wire constituting the cord is larger and the number of the wires is larger, while the durability becomes better as the diameter of the wire is smaller. However, in Example 3, even if the wire diameter was made smaller than that of the conventional example in order to match the breaking loads, the bending rigidity comparable to that of the conventional example could be maintained, and the durability was remarkably good. In Example 6, although the strand diameter is large, the durability is not inferior to the conventional example, and the rigidity is remarkably high.

[0021]

As described above, according to claim 1 of the present invention, there is provided a 1 + 5 structure in which six strands are twisted in the same direction at the same twist pitch so that one strand exists in the core. , Each strand has a continuous wave pattern, and in that state, the strands are exchanged and twisted so that the strands cross each other, so the permeability of the rubber is extremely good and stable, yet it has good durability. With rigidity and axial compression resistance,
Moreover, it is possible to obtain an excellent effect that an economical steel cord can be manufactured at a low manufacturing cost. Claim 2
According to this, since the pitch and height of the small wave habits of the strands are set in a predetermined range and the frequency of crossing the strands is set in a predetermined range, the effect of claim 1 can be reliably achieved in a well-balanced manner. Excellent effect can be obtained. According to claim 3,
An excellent effect is obtained in that it is possible to obtain a long-life radial tire that is excellent in steering stability and is also excellent in external damage resistance.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an open type steel cord used for reinforcing a conventional passenger vehicle tire.

FIG. 2 is a sectional view showing a steel cord used for reinforcing a conventional truck / bus tire.

FIG. 3 is an enlarged external view schematically showing an example of a steel cord according to the present invention.

FIG. 4 is an explanatory diagram schematically showing a cross section at position 5 in FIG.

FIG. 5 is an enlarged side view of a wire obtained by disassembling the cord.

FIG. 6 is an explanatory view showing an outline of an apparatus and a method for producing the cord of the present invention.

FIG. 7 is a partially cutaway side view showing a main part of the wire replacement device shown in FIG.

[Explanation of symbols]

 1 to 6 Elementary wire 10 Small wave habit p Small wave habit pitch P Cord twist pitch (Wave habit pitch of twisting) d Element wire diameter h Small wave habit wave height

Claims (3)

[Claims] 1. A steel cord having a 1 + 5 structure in which one element wire is arranged in a core portion and five element wires are arranged around the element wire, and the element wires are twisted at a time in the same direction and at the same twist pitch, Each wire has a small wave pattern with a pitch smaller than the wave pattern of the cord twisting, and the wires are twisted so that the parts where the wires do not intersect and the parts where they intersect in the longitudinal direction of the cord are mixed. Steel cord for tire reinforcement that is characterized by 2. A small wave habit of the strands has a spiral shape, and a ratio p / P between the pitch p of the small wave and the wave habit pitch P of the cord twist is in the range of 0.25 to 0.55. Further, the ratio h / d between the wave height h of the small wave and the wire diameter d is 1.05 to 1.
The steel cord for tire reinforcement according to claim 1, wherein the steel cord is in the range of 50 and the crossover frequency between the strands is in the range of 0.5 to 3.0 times per twist pitch of the cord. 3. A radial tire characterized in that the steel cord according to claim 1 or 2 is used to reinforce the belt portion.