JPH07126992A - Steel cord for reinforcing rubber - Google Patents

Abstract

PURPOSE:To obtain a readily producible steel cord of a five wire type having excellent rubber permeability, suppressed fretting wear and excellent bending fatigue performance. CONSTITUTION:In a steel cord comprising a first wire bundle 1 of two threads and a second wire bundle 2 of three threads, the first wire bundle has >=50mm torsional pitch P1 and is spirally wound with the second bundle at a pitch P2 smaller than pitch P1 in such a way that >=10% gaps are formed in the wire pitch between the first wire bundle and the second wire bundle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber reinforcing steel cord.

[0002]

2. Description of the Related Art Steel cords embedded in carcasses of radial tires for vehicles are required to have not only tensile strength but also excellent bending fatigue and rubber permeability. Figure 4 shows a conventional steel cord used for such applications.
As described above, a 1 × 5 structure having five wires W twisted together is known. In this prior art, when a tensile force is applied to the cord, equal loads are applied to the wires, and therefore the tensile strength is excellent and the cyclic bending fatigue property is good. However, since the adjacent wires contact each other and a void is formed in the center, the permeability of the rubber is poor, and when damaged, water enters the void and spreads in the longitudinal direction of the cord, promoting corrosion and accelerating corrosion. However, there is a problem that the adhesive strength of the is deteriorated and so-called separation phenomenon is likely to occur.

Further, Japanese Patent Publication No. 3-23683 discloses that
The two wires and the three wires are twisted together to make the two wires parallel in the longitudinal direction of the cord, and the three wires are halved with respect to the two wires as shown in FIG. There has been proposed a steel cord having a structure in which they are alternately twisted into a substantially umbrella shape as shown in FIG. However, in this prior art, in practice, as is clear from the above figure, the two sets of wires W ₁ and the three sets of wires W ₂ forming the steel cord are in close contact with each other,
Moreover, since the two sets of wires W ₁ and the three sets of wires W ₂ are constantly in close contact with each other in the longitudinal direction of the cord, a closed space S is formed between them, which causes difficulty in rubber permeability. Further, since the latter has a large winding length of the two-piece wire W ₁ and the three-piece wire W ₂ , the two-piece wire W ₁ of the core may be broken early when a tensile force acts. Since the wires are in contact with each other, fretting due to repeated bending occurs in the wire W ₁ and the three-piece wire W ₂ , which causes wire breakage, which reduces bending fatigue properties and impairs tire durability. There was a problem.

The present invention was devised in order to solve the above-mentioned problems, and the purpose thereof is to provide good rubber permeability, suppress fretting wear and good bending fatigue. , To provide a 5-wire type steel cord that is easy to manufacture.

[0005]

To achieve the above object, the present invention provides a steel cord comprising two first wire bundles and three second wire bundles, the first wire bundle having a length of 50 m.
The first wire bundle having a twist pitch of m or more, the second wire bundle having a pitch smaller than the pitch with respect to the first wire bundle having the twist pitch, and the first wire bundle having one pitch between the first wire bundle and the second wire bundle. It is configured so that it is spirally wound so that a gap of 10% or more is created therein.

[0006]

Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 and 2 show an example of a rubber-reinforcing steel cord according to the present invention, where 1 is two wires 1a, 1a.
A first wire bundle 2 consisting of three wires 2a, 2a,
A second wire bundle consisting of 2a, the wires 1a,
2a each have a diameter of 0.10 to 0.40 mm, and are plated with brass to improve the adhesiveness with rubber. First wire bundle 1 composed of the two wires
Are twisted in the aligned state at a pitch P ₁ in the range of approximately 50 to 400 mm (in FIG. 1, the pitch of the first wire bundle is emphasized), and the twisted first wire bundle is A second wire bundle 2 consisting of three wires is wound around 1 in a regular spiral pattern with a constant pitch P ₂ .

As shown in FIG. 2, the second wire bundle 2 maintains a substantially triangular mountain shape in any cross section as shown in FIG. 2, and the space between the first wire bundle 1 and the second wire bundle 2 is as shown in FIG. A release gap 3 that opens to the outside is formed. It is preferable that 10% or more of the release gap 3 exists within one pitch P ₁ of the first wire bundle 1. The reason for limiting the release gap 3 is based on the result of the field test conducted by the present inventor. That is, wire diameter 0.23 mm, first wire bundle twist pitch: 50-40
100 steel cords were prototyped with 0 mm and the second wire bundle winding pitch: 14 mm, embedded in each rubber compound, vulcanized to make a rubber block, and an air permeation amount measurement test was performed on each rubber block. It was To measure the amount of air permeation, connect the lower end of the cord protruding from the rubber block to the compressed air supply source via a pipe, cover the upper end of the cord protruding from the rubber block with a graduated cylinder, and sunk it in the water tank. 5 kgf
Compressed air of / cm ² was sent for 1 minute, and the amount of leak air at the upper end of the cord was observed. Then, the rubber of these steel cords is removed, embedded and fixed in a synthetic resin, 1 pitch P ₁ of the first wire bundle 1 is divided into 20 equal parts, and the cross sections of the cords are sequentially observed with an electron microscope. And the number of those having a gap in the second wire bundle 2 is counted, and the average value thereof is obtained. The quality cord (steel cord with an air permeability of 5% or less) has more than 10% gaps, and the air permeability is
The number of defective cross-sections of the defective code exceeding 5% was less than 10%. From this knowledge, the release gap between the first wire bundle 1 and the second wire bundle 2 is defined as 10% or more. However, if the release clearance ratio is too large, the elongation under low load is likely to be easily deformed, and the clearance will be closed when compounding with rubber or the tire uniform property will be deteriorated.
Usually, it is preferable to keep it at about 35%.

The twisting directions of the first wire bundle 1 and the second wire bundle 2 may be the same or different. The lower limit of the twisting pitch P ₁ of the first wire bundle 1 is set to 50.
The reason why mm is set is that it is effective for forming the release gap 3 because the number of contact points with the second wire bundle 2 is small at a twist pitch below this, but since the twist degree becomes too strong,
This is because there is a risk that the bending fatigue property will decrease. But,
When the twist pitch P ₁ is 400 mm or more, the bending fatigue property is prevented, but the angle of intersection between the wire bundles is reduced and the number of contacts is increased, so that the degree of formation of the release gap 3 is decreased, and the 1st pitch of the first wire bundle 1 is reduced. Release clearance 3 at 10
%, The upper limit is 400 mm. Pitch P ₁ twist of the first wire bundle 1 are rubber penetration, preferably in terms of tensile strength and fatigue resistance of the balance is about 100 to 250 mm. Pitch P ₂ of the second wire bundle 2 is much smaller than the pitch P ₁ of the first wire bundle 1, generally pitch ratio (P ₂ / P ₁₎ is 0.025 to 0.
35 is suitable. The reason is that if the pitch ratio is less than 0.025, the rubber permeability becomes poor, and if it exceeds 0.35, the tensile strength decreases due to the warp.

It is also possible to make two sets of wires parallel to each other or to give a large twist pitch of 300 mm to 1000 mm and to wind the two sets of wires in a spiral shape. In this case, four wires are used. Tend to form a bundle that is in close contact with each other and has a quadrangular cross section, so that the rubber permeability is poor and fretting is likely to occur, and the features of the present invention cannot be obtained.

FIG. 3 shows an example of an apparatus and method for obtaining a steel cord according to the present invention. A vertical axis 7 rotatably erected on a base and a vertical axis extending from the upper end of the vertical axis parallel to the vertical axis. With a twisting arm 8 rotatable about
In the same direction as the twisting machine A around the horizontal axis OO on the inlet side,
A second in-out buncher type having guide rollers 5a and 5b that rotate at the same speed, guide rollers 5c and 5d on the outlet side, and a pair of arc-shaped rotation guides 6a and 6b between the guide rollers. The twisting machine B is arranged in series. Two spools 9 and 9 are attached to the vertical axis 7 of the first stranding machine A, and the wires 1a and 1a for the first wire bundle 1 are wound around the spools 9 and 9, respectively. The wires 1a, 1a are pulled out from the spools 9, 9 and provided on the twisting arm 8 as a guide roller 8
The twisting arm 8 is aligned through 0,80
Of the feed roller 81 near the center of rotation of
It is adapted to be guided to the inlet of the second twisting machine B via the. In the area surrounded by the rotation guides 6a, 6b of the second stranding machine B, a non-rotationally fixed holder (not shown) is provided with three wires 2a, 2a, 2a for the second wire bundle 2. 3 bobbins 10a to 10c, each of which is wound up, are attached to the bobbin 10a to 10c.
A guide plate 11 with holes and a tightening die 12 that does not allow rotation around the axis of the wire bundle are arranged on the -O. The bobbins 10a to 10c are arranged in parallel at positions displaced from the horizontal axis OO, or arranged at intervals at positions surrounding the horizontal axis OO.

When the twisting arm 8 of the first twisting machine A rotates, the two wires 1a, 1a are pulled out from the two spools 9, 9 on the vertical axis 7, and the wires are sent out in a bundle state as a feeding roller 81. 1 of the twisting arm 8 before reaching
The rotation gives a single twist with a large pitch (for example, the S direction). This twist pitch can be adjusted to 50 mm to 400 mm by rotating the spools 9, 9 around the vertical axis 7. As described above, the two wires 1a and 1a that have been twisted once pass through the delivery roller 81, the inlet side guide roller 5a of the second twisting machine B, the arc-shaped rotation guide 6a, and the outlet side guide roller 5c. Then, it is guided to the tightening die 12 through the holes of the guide plate 11 with holes.
As a result, the two wires 1a, 1 twisted once
A is twisted a second time (for example, in the S direction) between the outlet side guide rollers 5c. This second twist has a pitch corresponding to the pitch of the second wire bundle 2 and becomes strong between the exit side guide roller 5c and the tightening die 12. On the other hand, in the second twisting machine B, three wires 2a, 2b, 2c are paid out from the bobbins 10a to 10c, and these three wires are gathered in the holes of the guide plate 11 with holes and guided to the tightening die 12. As a result, the two wires 1a, 1a in the twisted state are affixed to each other, and in this state, all the wires pass through the clamping die 12, pass through the inlet side guide roller 5b, pass through the arc-shaped rotation guide 6b, and exit side. Guide roller 5d
Reach. In the meantime, all the wires 1a, 1a, 2a, 2
a and 2a have a short pitch P ₂ for the second wire bundle and are twisted in a direction opposite to the twisting direction (for example, the Z direction) between the inlet side guide roller 5b and the arc-shaped rotation guide 6b. As a result, the two wires 1 twisted twice in the previous stage
Since a and 1a receive the twist in the opposite direction, the twist in the previous stage is returned to form the first wire bundle 1 having a large twist pitch P ₁ , and the second wire around which three wires are spirally wound in the Z direction. The wire bundle 2 is surrounded, and the cord 4 of the present invention thus produced is wound up on the external winding reel 13 via the outlet side guide roller 5d. In this example, the twist direction of the cord is SZ.

The twisting direction in the second twisting machine B may be Z direction in the former stage and S direction in the latter stage. In this case,
If the twisting direction in the twisting machine A is set to S, the wires 1a, 1a (twisting in the S direction) of the first wire bundle 1 are added with a small pitch P ₂ twist in the Z direction before the second twisting machine B. For,
Since excessive twisting back in the Z direction and a small pitch P ₂ in the S direction are given in the subsequent stage, excessive twisting back in the Z direction is eliminated, and a large pitch P ₁ twisting state in the S direction is obtained. Therefore, the cord twisting direction in this case is SS. The rotation direction of the twisting arm 8 of the first stranding machine A is 2
The wires 1A, 1A may be twisted either in the S direction or in the Z direction. In the latter case, the first twisting direction in the second twisting machine B is the Z direction,
If the second stage is the S direction, the twisting direction of the obtained cord will be ZS.

Next, the practical data of the present invention and the conventional product are shown in Table 1 below.

[0014]

[Table 1]

The air permeability in Table 1 is the value by the above-mentioned air permeability test method, and the fatigue property is the data by the 3-roll test, that is, one end of the vulcanized sample cord in which the steel cord is embedded in the rubber compound is fixed. Then, while the other end is connected to the weight that weighs 10% of the cord breaking load, a set of three rolls (each with a diameter of 1 inch) are simultaneously horizontally reciprocated to repeatedly apply tensile and compressive bending loads. Is the way. In addition, in order to improve the accuracy of comparison, the tensile strength of the present invention product, the conventional product, and the comparative product were constant. As is clear from Table 1, the first wire bundle composed of two wires is formed with a twist pitch of 50 to 400 mm,
A second wire bundle consisting of three wires is arranged around it with a pitch ratio.
(P ₂ / P ₁ ) 0.25 to 0.35 in a spiral shape, the number of windings is 10 in one pitch of the first wire bundle.
% Or more of the open gap is created, so that the rubber permeability is good, and since the rubbing of the wires is suppressed, the fretting is improved and the fatigue property is also good. When the twist pitch of the first wire bundle is set to a value less than 50 mm, the rubber permeability is good, but the twist strength is reduced and the tensile strength is lowered. The twist pitch of the first wire bundle is 500 mm
When it is made larger than 1.0, the tensile strength is good, but the open gap ratio is reduced and the rubber permeability is lowered.

[0016]

According to the present invention described above, 5
This wire-type steel cord has excellent rubber penetration, good fretting wear resistance, good bending fatigue, easy manufacture, and continuous manufacturing in one step. To be

[Brief description of drawings]

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

FIG. 2 is a sectional view of each part of the steel cord shown in FIG.

FIG. 3 is a side view showing an example of a steel cord manufacturing apparatus of the present invention.

FIG. 4 is a cross-sectional view of a conventional steel cord.

FIG. 5 is a sectional view of a conventional steel cord.

[Explanation of symbols]

1 1st wire bundle 2 2nd wire bundle 3 Release gap P ₁ 1st wire bundle twist pitch P ₂ 2nd wire bundle twist pitch

Claims (2)

[Claims] 1. A steel cord comprising two first wire bundles and three second wire bundles, wherein the first wire bundle is 50
a first wire bundle having a twist pitch of mm or more, a second wire bundle having a pitch smaller than the above-mentioned first wire bundle having the twist pitch, and a first wire bundle having one pitch between the first wire bundle and the second wire bundle. A steel cord for rubber reinforcement, which is spirally wound so that a gap of 10% or more is created therein. 2. The wire of the first wire bundle and the wire of the second wire bundle have the same diameter, and the winding pitch P _{2 of} the second wire bundle and the first wire bundle are equal to each other.
The ratio of the twist pitch P ₁ of the wire bundle (P ₂ / P ₁ ) is 0.025
The steel cord for rubber reinforcement according to claim 1, which is 0.35.