JPH1088488A - Steel cord for reinforcing rubber and radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an inexpensive steel cord for reinforcing a rubber, simple in structure but having a moderate elongation characteristic and good rubber permeability and fatigue resistance. SOLUTION: The improvements of a steel cord of 1+n structure comprising a core element wire and five or more side element wires 2 stranded around the core element wire comprises that the core element wire comprises a flat wire 1 having continuous waves in the longitudinal direction, that the core has an approximately unidirectional flat shape in the longitudinal direction, that spaces are formed between the flat wire 1 and the side element wires 2 due to the continuous waves of the flat wire 1, and that spaces 3 having distances of >=0.04mm are formed at least two places between adjacent side element wires 2 in the cross section rectangular to the longitudinal direction of the cord.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art In rubber products such as radial tires for automobiles and conveyor belts for transportation, a steel cord formed by twisting a plurality of steel wires is used as a reinforcing material. For example, in the radial tire for trucks and buses shown in FIG. 10, a steel cord is used as a reinforcing material in the belt portion 10 and the carcass portion 13. As such a steel cord, generally, three strands are used. Twisted to form a core and around 6 to 8 side strands are twisted around this core to form a two-layer structure, or 13 to 15 side strands around 6 to 8 side strands. A three-layer structure in which wires were twisted was used.

In recent years, weight reduction of rubber products has been required in order to reduce fuel consumption, and demand for cost reduction has been increasing. However, the steel cord as described above has a problem that the number of strands is large, the structure is complicated, and the cord manufacturing process requires two or three twisting steps, thereby increasing the manufacturing cost. . Therefore,
Attempts have been made to use steel cords having a small cord diameter and a simple structure.
No. 877 (Prior Art 1) discloses, as shown in FIG.
There has been proposed a steel cord in which each strand is overmolded and twisted and then flattened as a whole to have a substantially elliptical cross section. JP-A-63-135584 (prior art 2) discloses a steel cord in which a flat core is used as shown in FIG. 10 and a plurality of strands are spirally twisted around the core. Proposed.

The steel cords of the prior arts 1 and 2 have the advantage that they can be manufactured in a single twisting step, and the steel cord of the prior art 1 is loosely twisted by excessive molding. There is a gap between the wires that allows rubber to penetrate. In addition, since the uneven planes are substantially aligned in the same direction, the thickness of the cover rubber can be reduced, which is effective in reducing the weight. The steel cord of the prior art 2 also has the same effect as the prior art 1 because the uneven planes are aligned in substantially the same direction.

[0005]

However, the steel cord of the prior art 1 has a large low-load elongation because the strand is loosened due to the excessive shaping of the wire. For this reason, the handleability during the manufacture of the tire is not good, the workability of calendering is deteriorated, or the sheet is wavy due to the variation in low load elongation between cords at the time of cutting the sheet after calendering, or the sheet is cut. In addition, uneven edges may occur, and the dimensional accuracy of the sheet may deteriorate.
In addition, there is a problem that it is difficult to obtain dimensional accuracy of the tire because it is easily stretched during vulcanization or the like. Furthermore, when such a steel cord is used to reinforce the belt portion, there is a problem that the steering response is poor because the steel cord is easily elongated during running and the shape is easily collapsed. Prior art 2 has good shape stability due to the presence of the core, and can reduce the amount of tensile elongation of the cord. However, while the side strand is spirally wound, the core strand is straight. When a cord is subjected to a tensile or compressive force, a large load is applied to the core strand,
There is a problem in that the durability (fatigue resistance) is poor. In addition, since the core strand and the side strand are close to each other, it is difficult for rubber to penetrate between the core strand and the side strand, so There was a problem in that tink wear easily occurred.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a simple structure having good elongation characteristics, good rubber permeability and good fatigue resistance. It is to provide an inexpensive steel cord for rubber reinforcement. Another object of the present invention is to provide a lightweight radial tire excellent in corrosion resistance, durability, steering stability, and steering response.

[0007]

In order to achieve the above object, the present invention provides a steel cord having a 1 + n structure in which one core strand and n (n ≧ 5) side strands are twisted therearound. The core strand is formed of a flat wire having a continuous wave in the longitudinal direction, and the cord has a flat shape in substantially the same direction in the longitudinal direction, and a gap is formed between the core strand and the side strand due to the presence of the continuous wave. It is configured such that a gap of 0.04 mm or more is provided in at least two places between adjacent side wires in a cross section perpendicular to the longitudinal direction of the cord. Preferably, the flat wire has a flat ratio (thickness / width) of 0.60 to 0.60.
0.90, and the wave pitch p of the continuous wave is 4.0 to 8.0.
mm, and the wave height h is 0.30 to 0.45 mm. The continuous wave may be formed in the thickness direction of the flat wire,
It may be formed in the width direction, or may be formed in both the thickness direction and the width direction. Further, in order to achieve another object of the present invention, the steel cord is used in at least a part of a belt portion or a carcass portion of a radial tire.

[0010] The reason for the limitation in the present invention is as follows. First, the lower limit of the number of side strands is set to five, because if the number is less than this, the strength of the cord is insufficient. The upper limit of the number of side strands is preferably 9 when excessive cord weight is not preferred. The reason why the distance between the side strands is 0.04 mm or more and two or more is because rubber does not permeate with a gap amount and number smaller than this. The reason why the flat ratio (thickness / width) of the flat wire is set to 0.60 to 0.90 is that when the flat ratio is 0.60 or less, the coarse cord (corresponding to looseness around the flat wire) The side strand must be plastically deformed by applying a strong compressive force to the side strands), which deteriorates the fatigue and reduces the gap between the side strand and the flat wire. This is because unevenness occurs in rubber penetration. If the aspect ratio is 0.90 or more, the purpose of reducing the gauge pressure to reduce the weight cannot be achieved, and since the side strands come into line contact, the gap becomes small and the rubber permeability deteriorates. . The reason why the lower limit of the wave pitch p of the continuous wave is set to 4 mm is that if the pitch is too small in the range of the above-mentioned flattening ratio, it becomes difficult to process, and the productivity is deteriorated. This is because there is a possibility that the strength may be reduced. 0.30m lower limit of wave height h
The reason for setting m is that if it is less than this, the gap forming effect is insufficient and the rubber permeability deteriorates, and the upper limit is set to 0.45 mm. This is because calendar workability deteriorates.
By setting the flat wire to the above-described flatness ratio and wave condition, the low load elongation of the cord, that is, the 10 kg load elongation can be set to an appropriate range of 0.20 to 0.40%.
When the 10 kg load elongation s of the cord is 0.20% or less, the gap between the strands becomes small, so that the rubber permeability deteriorates,
This is because a large elongation of 0% or more deteriorates calendar workability.

[0009]

The steel cord according to the present invention has a loose open flat structure.
Since the flat line of 0.90 exists, the shape hardly collapses, the stability of the shape is good, and since the flat plane of the cord is substantially flush with the longitudinal direction, as shown in FIG. Cover rubber thickness for rubber sheet (reinforcement layer gauge thickness)
T can be reduced, and appropriate weight reduction can be achieved. The flat line at the center of the cord has an aspect ratio of 0.60 to 0.60.
Since it is 0.90, the low-load elongation during the calendering step, rubber vulcanization, and the like is reduced, thereby suppressing waving and uneven cut edges during sheet cutting, and improving dimensional accuracy.

In addition, the flat wire core is not linear, but a continuous wave is formed in the thickness direction, the width direction, or the thickness direction and the width direction. Moreover, the continuous wave has a wave pitch p of 4.
0 to 8.0 mm, and the wave height h is 0.30 to 0.45 mm. For this reason, firstly, when a tensile load or a compressive load is applied to the cord, the load applied to the side strand and the core strand is improved, and the fatigue resistance can be improved. Second
Although it has a loose open structure, since the rubber sufficiently penetrates around the core element wire, it is possible to suppress the occurrence of a core drop phenomenon. Third, since the side strands are loosely twisted, a sufficiently large gap is formed between the strands, and at the same time, a gap is surely formed between the flat wire of the core and the side strand.
As a result, the permeability of the rubber is improved, and the rubber and the steel cord are securely bonded and integrated. And 10kg
The load elongation can be in an appropriate range of 0.20 to 0.40%.

Therefore, when the cord of the present invention is applied to tire reinforcement, excellent corrosion resistance, fatigue resistance and light weight can be obtained with a simple structure. and again,
When used to reinforce the belt portion, the in-plane stiffness in the direction X parallel to the ground plane indicated by the arrow in FIG. 8 is increased, so that steering response is improved, and flexibility is provided in the direction Y perpendicular to the ground plane. Therefore, steering stability is improved. When used to reinforce the carcass part, the durability in the direction parallel to the shoulder surface indicated by X in FIG. 8 is improved, and the rigidity in the direction perpendicular to the shoulder surface indicated by Y is improved. And a very preferable tire reinforcing layer can be obtained.

[0012]

1 to 4 show a first embodiment of a steel cord according to the present invention. 1 and 2 show a first embodiment of the present invention, wherein 1 is a flat wire as a core wire, and 2 is a loosely twisted six side wire which is arranged on the outer periphery of the flat wire 1. The flat wire 1 and the side wires 2 form a steel cord having a 1 + 6 structure and a flat cross section. FIG. 3 shows a second embodiment, which is a steel cord having a flat cross section of a 1 + 5 structure in which five side strands 2 are loosely twisted around one flat wire 1.

The flat wire 1 is made of high-carbon steel, and its surface is coated with a material such as brass having good adhesion to rubber. The flat wire 1 has a band-shaped or block-shaped cross section having a thickness t that is relatively small with respect to the width w, and two planes at 180-degree symmetric positions are substantially flat as shown in the figure. However, in some cases, it may have an appropriate curvature. The flat body 1 has a flattening ratio (thickness / thickness) in the range of 0.60 to 0.90 in order to balance the elongation and the cord shape.
Width). The side strands 2 are also made of high-carbon steel, usually have a diameter of 0.20 to 0.45 mm, and are coated on the surface with good adhesion to rubber such as brass. In the first embodiment, the flat wire 1 has a flat continuous wave 100 formed in the thickness direction, and the apparent core dimension increases in the minor axis direction due to the unevenness constituting the continuous wave 100. ing. Also, FIG. 2 (a) (b)
As shown in (c) and FIGS. 3 (a), (b), and (c), the cord has an elliptical shape at each cross-sectional position perpendicular to the longitudinal direction, and the elliptical shape is always in a substantially constant direction in the longitudinal direction of the cord. ing. Since the side strands 2 are forcibly arranged outside by the irregularities constituting the continuous wave 100, the flat wire 1 and the side strands 2 have less contact portions, and the side strands 2 A gap S is formed between the flat wire 1 and the flat wire 1. On the other hand, the side strands are loosely twisted, and a gap S of 0.04 mm or more is formed in two or more places of the adjacent side strands 2.

FIGS. 5 and 6 show an example of the second embodiment of the present invention, in which a flat cross-section steel having a 1 + 6 structure in which six side wires 2 are twisted around one flat wire 1 is shown. Code. In this embodiment, the flat wire 1 is the first wire.
It has a flattened ratio in the predetermined range described in the embodiment and has a flat continuous wave 101 in the width direction, and the wave in the plate width direction has a long diameter as shown in FIGS. Since the apparent core dimension in the direction increases, it can be made almost flat in an elliptical shape at each cross-sectional position perpendicular to the longitudinal direction, and the elliptical shape is always in a substantially constant direction in the cord longitudinal direction. I have.
Also, the side strands 2 due to the irregularities constituting the continuous wave 100,
In particular, since the wire at the position corresponding to the width direction is disposed outward, the gap S between the flat wire and the side wire is
Increase. On the other hand, a gap S of 0.04 mm or more is formed at two or more places of the adjacent side wires 2.

FIG. 7 shows a third embodiment of the present invention. In this embodiment, the flat line 1 has the flatness ratio in the predetermined range described in the first embodiment, but in this embodiment, the flat line 1 has a continuous wave 100 in the thickness direction and a continuous wave 101 in the width direction. Of the composite continuous wave 102. Due to the composite continuous wave, the apparent dimension of the core increases on both the major axis side and the minor axis side.
An elliptical cord having a relatively large major axis ratio can be obtained. And since the side strand 2 will be arrange | positioned outside by 102 by a compound continuous wave, the clearance gap S between the flat wire 1 and the side strand 2 is large, while the side strand is loose. Since the wires are twisted, a gap S of 0.04 mm or more is formed at two or more places of the adjacent side strands 2 and 2.
In this embodiment, the pitch p of the continuous wave 100 in the thickness direction and the pitch p ′ of the continuous wave 101 in the width direction may be the same or different (p> p ′ or p <p ′).

In the first to third embodiments, the continuous waves 100, 101, and 102 should be set under constant conditions.
First, the pitch p needs to be in the range of 4.0 to 8.0 mm in consideration of stability of the cord shape and productivity, and the wave height h is 0.3 in consideration of the balance between elongation and gap formation.
It is necessary to set it in the range of 0 to 0.45 mm. And by satisfying these conditions, 10kg of cord
The load elongation is set to fall within the range of 0.20 to 0.40%. The detailed reasons for these limitations are as described above. By setting the pitch and the wave height in the specific ranges as described above, it is possible to improve the balance between the tensile strength and the elongation of the flat wire 1 and the side strand 2 in the cord state. In addition,
The number of the side strands 2 is 5 and 6 in the embodiment, but is not limited to this, and may be 7, 8, or 9, and the twisting direction may be any of the S direction and the Z direction. In addition, one wrapping wire may be wound around the side strand 2 as necessary.

The flat wire 1 with a continuous wave according to the first embodiment of the present invention
Can be manufactured by rolling a round wire having a predetermined diameter by a rolling device including a pair of rolls, and then passing the roll through a crimping device including a set of disks with pins or gears. In addition, the flat wire with continuous wave 1 of the second embodiment is passed through a crimping device in a state of a round wire to form a flat continuous wave, and is rolled by a rolling device in a direction orthogonal to the continuous wave. Can be manufactured. In the case of the third embodiment, after the flat line 1 with a continuous wave of the second embodiment is formed, the continuous wave in the thickness direction may be formed by passing through the crimping device. The method of manufacturing the cord according to the present invention is not limited. For example, a required number of side strands are arranged around the flat wire 1 with the continuous wave while being fed using a tubular twisting machine or the like and twisted. Then, the coarse cord is formed, and then the coarse cord is appropriately compressed by a pair of upper and lower rolls or the like to adjust the shape, and then wound up on a take-up reel. The flat line 1 with continuous waves may be manufactured in advance and wound on a reel, or may be manufactured continuously and continuously. That is, in the first embodiment, the rolling device is provided in the core wire supply line in the preceding stage of the tubular twisting machine.
In the second embodiment, a crimping device and a rolling device are arranged in a core wire supply line at a preceding stage of a tubular twisting machine. In a third embodiment, a crimping device and a rolling device are arranged at a preceding stage of a tubular twisting machine. What is necessary is just to arrange | position crimping apparatus-rolling apparatus-crimping apparatus in a line supply line, and to perform it.

[0018]

Next, examples of the present invention will be described together with comparative examples.
The manufactured steel cord has a long diameter of 1.4 ± 0.1 m
m, short diameter: 1.0 ± 0.1 mm, cutting load: 200 ± 1
0kg, 0kgf → 50kgf elongation: 0.8 ± 0.1%
It is of the specification. As the side strands, six plated high-carbon steel wires with a diameter of 0.34 mm are used.
High-carbon steel wire with plating has various flatness ratios made by rolling against roll and then crimping, and the wave direction is taken in the thickness direction, and the pitch and wave height are variously used.
A 1 + 6 structure steel cord with a flat cross section was manufactured using a tubular twisting machine and a roll-type compression device. The twist direction of the side strand was S direction, and the twist pitch was 16.0 mm. Each sample is shown in Table 1. Table 2 shows the results of a characteristic test performed on the obtained steel cord having a flat cross section having a 1 + 6 structure. In Table 2, the "gap between the side strands" was measured based on the cross-sectional photograph obtained by cutting a sample into four equal twisted pitches. "Rubber permeability" means that a sample cord is placed between unvulcanized rubber sheets and vulcanized while applying a pressure of 50 kgf / cm ² to make a test piece 50 mm long. The core wire (flat wire) was removed by pulling out the wire, and the extent to which the ground of the core wire (flat wire) was covered with rubber was measured with a stereoscopic microscope, and expressed as a ratio (%). "Fatigue" means that one end of the sample is fixed, the middle part is passed through three rolls, then the leading part is attached to a guide roll, and the entire three rolls are reciprocated 5,000 times while applying a weight of 5% of the breaking load. The number of breaks of the core strand and the side strand was observed. 100 indicates no break.

[0019]

[Table 1]

[0020]

[Table 2]

As is clear from Tables 1 and 2, the flat wire having a flatness ratio, pitch, and wave height within the range of the present invention has a 10 kg load elongation, a gap, a rubber permeability, and a fatigue property. Good. However, if any one of the aspect ratio, pitch and wave height is out of the range of the present invention, 10 kg
It is understood that at least one of the load elongation, the size of the gap, the rubber permeability, and the fatigue property becomes defective.

[0022]

According to the first aspect of the present invention, the combination of the flat wire 1 with continuous waves and the side strands 2 makes it possible to obtain a moderate elongation characteristic and a good rubber permeability while having a simple structure. An excellent effect of being able to provide a fatigue-resistant rubber reinforcing steel cord at low cost is obtained. According to Claims 2 to 5, since the flatness of the flat body, the wave pitch and the wave height are within predetermined ranges, an excellent effect that the elongation, the rubber permeability and the fatigue resistance can be accurately improved in a well-balanced manner. Is obtained. According to claim 6,
An excellent effect of being able to provide a lightweight radial tire suitable for trucks and buses having excellent corrosion resistance, durability, steering stability and steering response is obtained.

[Brief description of the drawings]

FIG. 1 is a partially enlarged perspective view schematically showing one example of a first embodiment of a steel cord according to the present invention.

2 (a), 2 (b) and 2 (c) are cross-sectional views of different portions of the steel cord of FIG. 1, respectively.

FIGS. 3 (a), 3 (b) and 3 (c) are cross-sectional views showing different examples of the first embodiment of the steel cord according to the present invention, in different sections.

FIG. 4 is a side view of the flat body used in the first embodiment of the present invention.

FIG. 5 is a partially enlarged perspective view schematically showing an example of a second embodiment of the steel cord according to the present invention.

6 (a), (b) and (c) are cross-sectional views of different portions of the steel cord of FIG. 5, respectively.

FIG. 7 is a partially enlarged perspective view schematically showing an example of a third embodiment of the steel cord according to the present invention.

FIG. 8 is a partial perspective view of a reinforcing layer using a steel cord according to the present invention.

FIG. 9 is a sectional view of a conventional steel cord.

FIG. 10 is a sectional view of a conventional steel cord.

FIG. 11 is a partially cutaway plan view of a tire to which the present invention is applied.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Flat wire 2 Side strand 100 Continuous wave 101 Continuous wave 102 Composite continuous wave w Flat wire width t Flat wire thickness S Gap

Claims (6)

[Claims] 1. One core strand and n strands around the core strand (n ≧ 5)
A steel cord having a 1 + n structure obtained by twisting the side wires of the above, wherein the core wire is a flat wire having a continuous wave in the longitudinal direction, and the cord has a flat shape having substantially the same direction in the longitudinal direction. A gap is formed between the flat wire and the side wire by the continuous wave of the flat wire, and a gap of 0.04 mm or more in at least two places between adjacent side wires in a cross section perpendicular to the longitudinal direction of the cord. A steel cord for rubber reinforcement characterized by being provided. 2. The flat wire has an aspect ratio (thickness / width) of 0.60.
0.90 to 0.90, and the wave pitch p of the continuous wave is 4.0 to 8.0.
The rubber cord for reinforcing rubber according to claim 1, wherein the cord has a thickness of 0 mm and a wave height of 0.30 to 0.45 mm. 3. The steel cord for rubber reinforcement according to claim 1, wherein a continuous wave of the flat wire is formed in the thickness direction. 4. The steel cord for reinforcing rubber according to claim 1, wherein a continuous wave of the flat wire is formed in the width direction. 5. The steel cord for reinforcing rubber according to claim 1, wherein a continuous wave of the flat wire is formed in a thickness direction and a width direction. 6. A radial tire using the steel cord according to claim 1 for at least a part of a belt portion or a carcass portion.