JP2920110B2 - Steel cord and steel radial tire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a steel cord used for a rubber molded product such as a steel radial tire and a conveyor belt, and a steel radial tire using the same.

[0002]

2. Description of the Related Art Steel cords are used as reinforcing materials for rubber molded products such as steel radial tires and conveyor belts. A typical example of a steel cord is a two-layer twist (3) described in JP-A-5-302283.
+6) There is a steel cord with a structure. This (3 + 6) steel cord is formed by first twisting three steel wires to form a core strand, and then twisting six steel wires around the outer periphery to form side strands. Such a two-layer twisted steel cord has a different direction twist (SZ twist) type in which the twist of the core strand and the twist of the side strand are reversed, and the twist of the core strand and the side strand in the forward direction. Same direction twist (SS
(Twist) type.

[0003]

However, the conventional (3 + 6) steel cord requires two twisting steps, so that the productivity is low and the manufacturing cost is high. Especially when manufacturing using a buncher (double twister), the twist of the core strand is returned during the cross-twisting process in the different direction twist type, so it must be twisted beforehand at a pitch shorter than the pitch of the final cord. The productivity is low.

Further, in the (3 + 6) steel cord, rubber hardly penetrates to the center of the three-strand core strand, and a gap is easily generated in the center of the core. Having a void in the center of the core easily shortens the life of the steel cord because internal corrosion and fretting wear easily occur.

[0005] Further, in the steel radial tire, one
In order to ensure a certain level of durability, the steel cord must have a certain level of breaking strength. Co
To improve the breaking strength, the wire diameter must be increased.
In general, if the cross-sectional area of the steel cord is simply increased to obtain a desired breaking strength, the pitch of the cords in the calendering process becomes too large, and the pitch of the cords is spread on the rubber sheet. The number of lines cannot be increased. While meeting the required breaking strength
In order to increase the number of cords
Use a large-diameter core wire and use a small-diameter core wire.
There is a need. However, the side wire
The larger the diameter ratio (wire diameter ratio), the more the core wire
Can be easily pulled out of the cord core.

An object of the present invention is to provide a steel cord which has high productivity, has a desired breaking strength, hardly comes off the cord core , and has excellent rubber permeability. Also, the object of the present invention is to prevent the cord core from slipping out.
Another object of the present invention is to provide a long-life steel radial tire reinforced with a steel cord that is less likely to cause internal corrosion and fretting wear.

[0007]

SUMMARY OF THE INVENTION A steel cord according to the present invention is embedded in a rubber molding to form a rubber molding.
It consists of strands in which multiple wires for reinforcement are twisted.
Steel cord, the strand is flattened
Up to now, each has been molded to the molding rate Kc and is substantially the same.
The two core wires of diameter and the strand are flattened
Five sides each of which has been molded to the molding ratio Ks before, and whose diameter is larger than the diameter of the core wire, and which are substantially the same diameter and are twisted together with the core wire around the core wire And the core wire has a molding rate K.
c is greater than the molding rate Ks of the side wire, and
The cross section of the strand composed of the two side wires and the two core wires is flat. The present invention
In the wire cord, the molding rate Kc of the core wire is
Since it is larger than the molding rate Ks, the rubber permeability is improved.
And 2 core wires come off from 5 side wires
It becomes difficult, and becomes excellent in shape retention. Multiple Wye
So-called bunched steel cords
, The core wire and the side wire are twisted together
Therefore, both are in line contact, and the core wire comes off the cord core.
Easy to put out. In particular, the side wire
The larger the diameter ratio (wire diameter ratio), the more the core wire
Easily escapes from the core of the cord, keeping the cord in shape
Is impaired. Therefore, in the present invention, the strand
Before flattening, the shaping rate Kc of the core wire is
Each wire should be larger than the ear molding rate Ks.
Type each, and twist these typed wires at once
Join together. As a result, when the wire diameter ratio is large,
Also, the core wire does not come out of the cord core. here
The “molding rate” means that adjacent wires come into contact with each other.
From the center axis of the strand when twisted tightly
When the displacement of each wire is 100,
Twist wires that have been plastically deformed before twisting
And flatten the strand as shown in FIG.
Of each wire from the center axis of the strand before
Is expressed as an index in percentage.

In this case, the cross section of the strand consisting of five side wires and two core wires is formed in an elliptical shape,
The ratio (flat ratio) of the major axis to the minor axis of this ellipse is 1.1
It is desirable that the ratio be in the range of 0 to 2.00, and it is most preferable that the aspect ratio be in the range of 1.20 to 1.40.

When the aspect ratio is smaller than 1.10, the rubber permeability decreases and the core wire is pulled out of the cord core.
This is because it is easy to break out . In the present invention, the core wire type
Make the attachment rate Kc larger than the side wire molding rate Ks
The core wire cannot easily come out of the cord core.
No. On the other hand, when the aspect ratio is larger than 2.00, the major axis increases and the number of cords laid on the rubber sheet decreases, and in particular, the desired number of laid cords can be secured up to an aspect ratio of 1.40. Therefore, the strength level of the rubber molded product can be increased.

In addition, the core wire has substantially the same diameter, the side wires have substantially the same diameter, and the ratio of the side wire diameter to the core wire diameter (wire diameter ratio) is 1.45 to 1.45.
It is preferable that the ratio be in the range of 2.25, and it is particularly preferable that the wire diameter ratio be in the range of 1.60 to 2.12.

[0011] If the wire diameter ratio is smaller than 1.45, the mutual interval between the side wires becomes too wide, and twisting failure occurs. On the other hand, if the line diameter ratio greater than 2.25, Kokorowa
This is because the ear can easily come off from the cord core, and the interval between the side wires becomes too narrow, so that the rubber permeability decreases. In addition, this is because the effective cross-sectional area of the cord decreases and the breaking strength becomes insufficient.

The range of the wire diameter ratio is based on the case where two wires of the same diameter and five wires of the same diameter are tightly twisted together (an aspect ratio of 1.0). For example, when the side wire diameter is D (= 0.370 mm), the diameter d of the core wire is obtained using the following equation (1), and the obtained d (= 0.130) is obtained.
mm), the range of the wire diameter ratio can be set. Since this corresponds to a state in which the twist is tight, the diameter D ₁ of the actual core wire is larger than d.

D = (D / 2) × [1 / {sin (360 ° / 10)}] − (D / 2) (1) Furthermore, the constituent wires have a tensile strength of 300 to 360 k.
It is desirable to use a high-strength steel wire of gf / mm ² . This is because, in order for the steel cord to obtain a desired breaking strength, the tensile strength of the wire needs to be 300 kgf / mm ² or more. On the other hand, the tensile strength of the wire is 360 kgf /
If the thickness exceeds mm ² , the wire becomes brittle and the wire is easily broken. In this case, especially when the tensile strength is 33
It is preferable to use a high tensile strength steel wire in the range of 0 to 340 kgf / mm ² .

[0014]

The inventor of the present invention has intensively studied a so-called bunched type steel cord in which a plurality of wires are twisted at one time in order to solve the above-mentioned drawbacks of the two-layer twisted steel cord. As a result of various studies, the following has been found.

In the bunched type steel cord, the core strand and the side strand are in line contact with each other, so that the core strand is easily pulled out. Further, since the adjacent wires are in close contact with each other, it is difficult for the rubber to sufficiently penetrate into the core strand. Furthermore, in a bunched type steel cord, the balance between the torque of the core strand and the torque of the side strand is not well-balanced, and the residual rotational torque of the core strand is extremely large, so that the sheet warps near or far from the cut surface of the rubber sheet. Is generated.

The present inventors have based on these findings, and five side wire with the two heart wires and heart
Various studies have been made on flat steel cords having variously changed wire shaping rates and side wire shaping rates. As a result, it is possible to obtain a small bunch de type of the steel cord of linear contact ratio by selecting a shaping rate Ks of typed index Kc and side wires of suitable cardiac wires, heart
Uniform collective twisting of the wires, which makes it difficult for the wires to come out of the cord core, can be realized, and since the number of the core wires is two, flattening is easy and rubber permeability is greatly improved.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Various preferred embodiments of the present invention will be described below with reference to the accompanying drawings. As shown in FIG. 1, a core wire supply unit 12 and a side wire supply unit 14 are provided upstream of a steel cord manufacturing line. The core wire supply unit 12 includes two bobbins 12a and 12b, and the side wire supply unit 14 includes five bobbins 14a to 14b.
e. 0.20 for each bobbin 12a, 12b
An alloy-plated steel wire 3 having a diameter of mm is wound. Further, an alloy-plated steel wire 4 having a diameter of 0.37 mm is wound around each of the bobbins 14a to 14e. In addition, each steel wire 3,
4 are disclosed in JP-A-3-28396 and JP-A-2-26.
Alloy plating is performed by the method described in Japanese Patent No. 7257.

Immediately downstream of the core wire supply unit 12, a tension equalizer is provided. The tension equalizer includes a powder brake 16 and a drive motor 18. Excessive feeding of the wire 3 is prevented by applying an appropriate frictional resistance to the wire 3 by the powder brake 16 while pulling the wire 3 by the drive motor 18. The tension equalizer includes a moving pulley 36 having a sensor 37, a detector 37a, and a swing arm 36a as shown in FIGS.
Is mounted, and the tension applied to the wire 3 is feedback-controlled with high precision. The arm 36a is swingably supported by a shaft 36b.

Further, the two wires 3 are sent from the tension equalizer to the preformer 24 via the guide rollers 20 and 22, and as shown in FIG.
Each is preformed (corrugated) into a waveform.

Next, a tension equalizer for controlling the wire tension will be described with reference to FIGS. 2 (A) to 2 (C). A tension equalizer is provided immediately downstream of the side wire supply unit 14. The tension equalizer includes a powder brake 32, a drive motor 34, a moving pulley 36, a swing arm 36a, a detector 37a, and a sensor 37.

As shown in FIG. 2A, the wire 4 is wound around the drum of the powder brake 32 and the drum of the drive motor 34 so as to reciprocate a plurality of times. The powder brake 32 is provided with a dedicated braking mechanism, and the rotation braking of the drum is controlled independently and independently of the braking mechanism (bobbin brake) of the bobbins 14a to 14e.

The moving pulley 36 and the magnetic sensor 37 are connected to the motor 3
4 to control the feeding speed of each wire 4. A weight (not shown) is attached to the moving pulley 36 so that a desired tension is applied to each wire 4. Arm 36a of moving pulley 36
At one end, a detector 37a for posture detection is attached. The detector 37a faces the magnetic sensor 37. The detection end of the detector 37a is formed so as to form a cycloid curved surface.

The magnetic sensor 37 has a magnetic field forming circuit. The sensor 37 and the detector 37a are connected to an input side of a controller (not shown). When the swing arm 36a is inclined with respect to the horizontal plane, the magnetic flux density of the magnetic field formed between the sensor 37 and the detector 37a changes, and a detection signal is sent to the controller. When the moving pulley 36 is at the reference position and the swing arm 36a is in the horizontal position, no signal is sent from the sensor 37 and the detector 37a to the controller.

As shown in FIG. 2B, when the moving pulley 36 moves above the reference position and the arm 36a is inclined with respect to the horizontal plane, a detection signal is sent from the sensor 37 and the detector 37a to the controller. The controller drives the motor 34 based on the detection signal to speed up the feeding of the wire 4. At this time, the force acting on the wire 4 is mainly due to the rotational driving force of the motor 34, and the powder brake 32 and the bobbin brake are applied lightly so that the wire 4 is evenly spread. As a result, the moving pulley 36 descends to the reference position, and the arm 36a returns to the horizontal position.

As shown in FIG. 2C, when the moving pulley 36 moves below the reference position and the arm 36a is inclined with respect to the horizontal plane, a detection signal is sent from the sensor 37 and the detector 37a to the controller. The controller decelerates the rotation speed of the motor 34 based on the detection signal and delays the feed speed of the wire 4. As a result, the moving pulley 36 moves up to the reference position, and the arm 36a returns to the horizontal position. In this way, the tension applied to the wire 4 is controlled so as to be always at a constant level.

Further, guide rollers 38 and 39 are provided on the downstream side of the moving pulley 36, and each wire 4 is guided toward the preformer 24 of the horizontal portion 40. As shown in FIG.
4a is provided with a plurality of wire guide pins 25. When the wires 3 and 4 pass through the wire guide pins 25 one after another, the wires 3 and 4 are shaped into a desired waveform.

In the horizontal portion 40, the preformer 24, the first end plate 26, the second end plate 28, and the voice 30 are arranged in this order. The first end plate 26, the second end plate 28, and the voice 30 are fixed to the foundation so as not to move. Further, a double twister type buncher (stranded wire machine) 50 is provided downstream of the voice 30. First, when the two wires 3 pass through the second end plate 28, they are sent horizontally to the voice 30 together, and when the two wires 3 and the five wires 4 pass through the voice 30, they are twisted by the buncher 50. Then, (2/5) strand 2a is formed. This (2/5) (or (1 × 7)) strand 2a
_Has a substantially perfect circle with a diameter D ₀ as shown in FIG.

The double twister type buncher 50 has a cradle 100 in which capstans 56a and 56b, a leveling roll 60, and a winding bobbin 69 are provided. These first and second turn rolls 52a, 52b are arranged on the same axis and revolve around the axis. The body frame of the buncher 50 is rotatably supported by the frame by a pair of hollow spindles. A loop extends between the pair of spindles. One spindle is provided with a first turn roll 52a, and the other spindle is provided with a second turn roll 52b. The first and second spindles are provided by the pair of spindles.
Turn rolls 52a and 52b are revolved around the axis. The strand 2a is sent from the first turn roll 52a to the second turn roll 52b so as to draw an arc.

First and second turn rolls 52a, 52
b, each rotation axis is inclined at a predetermined angle with respect to the horizontal plane. The winding bobbin 69 includes the first and second bobbins.
Are provided so as to maintain a constant posture regardless of the revolution of the turn rolls 52a and 52b.

First and second turn rolls 52a, 52
The overtwisters 54a and 54b, the capstans 56a and 56b, the guide roll 58, the leveling roll group 60, and the take-up bobbin 69 are arranged between b. The over twisters 54a and 54b are for applying an excessive twist to the strand 2a to further plastically deform the corrugated wires 3 and 4.

As shown in FIG. 3, when the strand (bundle of wires) 2a passes through the second turn roll 52b, it is overtwisted by the overtwisters 54a and 54b to form the first strand.
It reciprocates between the capstan 56a and the second capstan 56b, enters the leveling roll section 60, and reciprocates between the first capstan 56a and the second capstan 56b, and is wound via the traverser 68. It is taken up by the take-up bobbin 69.

Next, the break-in roll section 60 will be described with reference to FIGS. As shown in FIG. 5, the leveling roll unit 60 includes two upper and lower roller units 61 and 62. The lower roller unit 62 is fixed, and the upper roller unit 61 is supported by a press (not shown) so as to be able to move up and down. The lower roller unit 62 includes two guide rollers 64 and a number of leveling rollers 66,
The upper roller unit 61 includes a number of leveling rollers 66. These upper and lower rollers 64 and 66 are staggered so as to be alternated. The staggered pitch interval of the leveling rollers 66 is preferably in a range from 0.7 times to 2.3 times the roller diameter. In this embodiment, the diameter of the guide roller 64 and the leveling roller 66 is 16 mm.
It is. The diameter of these rollers 64, 66 is preferably in the range of 10 to 20 mm.

As shown in FIG. 6, a V groove 64a is formed on the peripheral surface of the guide roller 64. The strand 2a is guided in the V groove 64a. The guide rollers 64 are provided on the entry side and the exit side of the strand 2a, respectively.

As shown in FIG. 7, the peripheral surface 66a of the leveling roller 66 is flat. When the upper roller unit 61 is lowered, the flat peripheral surface 66a of the leveling roller 66 is pressed against the strand 2a to form the flat strand 2. That is, the strand 2a having a substantially perfect circular cross section as shown in FIG. 8 is crushed, and becomes the strand 2 having an elliptical cross section as shown in FIGS. When the strand 2a is crushed, the two core wires 3 do not protrude outside the five side wires 4. The reason why the core wire 3 does not protrude outward is that the side wire 4 is corrugated by the preformer 24 and an appropriate tension is applied to the core wire 3. Incidentally, in this embodiment, the corrugated maximum peak height of the core wire 3 (diameter 0.20 mm) is 0.54 mm, and the side wire 4 (diameter 0.37 mm).
Has a maximum peak height of 1.371 mm. On the other hand, if the side wire 4 that is not corrugated at all is sent to the leveling roll part 60, the core wire 3 jumps out of the side wire 4. Therefore, as the maximum peak height of corrugation of the side wire 4 increases and the tension of the core wire 3 increases, the core wire 3 does not protrude outside the side wire 4.

Next, the steel cords of Examples 1 and 2 and their evaluation will be described with reference to FIGS. (Embodiment 1) FIGS. 9 to 14 show a cradle-type stranded wire machine described in Japanese Patent Application Laid-Open No. 5-302283.
The steel cord 2 having the (1 × 7) configuration shown in FIG.
FIG. 9 shows a code cross section at a reference point, FIG. 10 shows a code cross section at a position shifted by 1/4 pitch from the reference point,
FIG. 11 shows a code cross section at a position shifted by 1/2 pitch from the reference point, and FIG. 12 shows a code cross section at a position shifted by 3/4 pitch from the reference point. The manufacturing conditions and the product size of Example 1 are shown below.

335 ± 5 kgf / mm ² core wire diameter D ₁ ; 0.175 mm side wire diameter D ₂ ; 0.370 mm twist pitch; 16 mm twist direction; S twist core wire molding rate; 1.3% Side wire mold ratio; 110.4% Flatness ratio; 1.30 Average long diameter LD of cord; 1.29 mm Average short diameter SD of cord; 0.99 mm Cord breaking load; 185.7 kgf / mm ² As shown in FIGS. 13 and 14, a flat steel cord 2 having a long diameter LD and a short diameter SD was obtained. In the steel cord 2 of Example 1, when the average major axis LD was the same, the average minor axis SD was considerably smaller than that of the steel cord of the (1 × 9) configuration of the comparative example.

Incidentally, the steel cord having the (1 × 9) configuration of the comparative example has a flat shape in which three core wires and six side wires described in JP-A-5-302283 are twisted together. It is equivalent to one having a cross section. (Example 2) A steel cord 2A having a (1 x 7) configuration shown in Figs. 15 to 18 was manufactured using the same cradle type twisted wire machine as that of Example 1 described above. 15 shows a code cross section at a reference point, FIG. 16 shows a code cross section at a position shifted by 1/4 pitch from the reference point, and FIG. 17 shows a code cross section at a position shifted by 1/2 pitch from the reference point. FIG. 18 shows a cross section of the cord at a position shifted by 3/4 pitch from the reference point.

The manufacturing conditions and the product size of Example 2 are shown below. 335 ± 5 kgf / mm ^2- core wire diameter D ₄ ; 0.175 mm side wire diameter D ₅ ; 0.370 mm twist pitch; 16 mm twist direction; S twist core wire molding rate; 132.2% 125.0% Flatness ratio; 1.33 Average long diameter LD of cord; 1.42 mm Average short diameter SD of cord; 1.07 mm Cord breaking load; 185.2 kgf / mm ² (Example 3) A steel cord (not shown) of Example 3 having a (1 × 7) configuration was manufactured using the same cradle-type stranded wire machine as in Examples 1 and 2 described above.

The manufacturing conditions and product size of Example 3 are shown below. 335 ± 5 kgf / mm ^2- core wire diameter d; 0.200 mm side wire diameter D; 0.370 mm twist pitch; 16 mm twist direction; S twist Core wire molding rate; 135.0% side wire 112.8% Flatness ratio; 1.34 Average long diameter LD of cord; 1.38 mm Average short diameter SD of cord; 1.03 mm Cord breaking load; 186.5 kgf / mm ² Rubber permeability; 100% [ Evaluation of Rubber Permeability] The steel cords 2 and 2A of Examples 1 to 3 were evaluated for rubber permeability as compared with conventional products and comparative products. In addition, the steel cord of (3 + 6) composition was used for the conventional product. In addition, a comparative example includes JP-A-5-302.
No. 283, a steel cord having a flat cross section (1 × 9) was used.

The rubber permeability was evaluated as follows. First, a steel cord having a length of 20 pitches is prepared for each of the embodiment, the conventional example, and the comparative example. The side wire of each cord is peeled off, and a visual inspection of the rubber permeation state at a total of 40 places at each of the front and rear peaks is visually performed with the naked eye.

A point system was adopted for visual inspection. If 5 points are where the rubber has completely penetrated, 2.5 points where the rubber has penetrated about half and 0 points where the rubber has not penetrated, a total of 100 points in the table Point or back 100
A total of several points were examined. Furthermore, these scores were summed and divided by 2 to obtain an average score, which was expressed as a percentage to evaluate rubber permeability. Those having a rubber permeability of 90% or more were judged to be acceptable.

The results of Examples, Comparative Examples and conventional products are shown below. Rubber permeability (%) at the side of the core Rubber permeability (%) Example (1 × 7) constituent code 90-100 90-100 Comparative example (1 × 9) constituent code 80-90 85-100 Conventional product (3 + 6) Configuration Codes 30 to 50 80 to 95 Next, the effects of the embodiment will be described with reference to FIGS.

FIG. 19 is a graph plotting the result of examining the relationship between the two examples with the major axis (mm) on the horizontal axis and the rubber permeability (%) on the vertical axis. FIG. 20 is a graph plotting the results of examining the relationship between the two examples for each example, with the horizontal axis representing the flatness ratio and the vertical axis representing the rubber permeability (%).

In each figure, the circle (curve A) shows the result when the molding rate of the side wire is 110.4%, and the square (curve B) shows the result when the molding rate of the side wire is 125.0%. And triangles (curve C) show the results when the molding rate of the side wire was 137.0%. The core wire diameter is 0.175m
m, side wire diameter 0.370mm, cord twist pitch 1
6 mm.

As is clear from FIGS. 19 and 20, the rubber permeability increases as the molding rate of the side wire increases. It was also found that the rubber permeability increased with an increase in the major axis and an increase in the aspect ratio at the same mold ratio.

Next, a case of manufacturing a steel radial tire for a truck or a bus using the above-described steel cord will be described with reference to FIGS. As shown in FIG. 21, first, another steel cord 2B is arranged so as to be substantially straight and at equal intervals, and a raw rubber plate 73 is attached from above and below so as to sandwich the steel cord 2B. A carcass plate is manufactured by such calendaring. The carcass plate is cut at predetermined lengths along the cutting line 91. The cutting line 91 is orthogonal to the steel cord 2B. The uncut end surfaces of the obtained cut sheet are joined together and used as a tire carcass 72. The carcass 72 is wound around a drum of a tire forming machine. Side wall 8
4 is formed integrally with the side ply 76 and the bead filler 78. On the other hand, a bead 80 is manufactured by forming a steel wire into a ring shape. Drum with sidewall 8
4 is wound, and this is combined with the carcass 72. Remove the tire assembly from the drum and set it on the drum of the molding machine. Then, the beads 80 are fitted on both sides of the tire assembly, and both ends of the carcass 72 are wound around the beads 80. Pressurized air is supplied into the tire assembly to inflate it.

As shown in FIG.
(2A) are arranged so as to be substantially straight and at equal intervals, and a raw rubber plate 75 is attached to each of the steel cords 2 (2A) from above and below. A belt plate is manufactured by such calendering. Along the cutting line 93, the belt plate is cut into various sizes. The cutting line 93 is oblique to the steel cord 2 (2A). The obtained cut sheet is used as the belts 74a to 74a.
4d. The belts 74a to 74d are pasted on the carcass of the tire assembly one after another.

The synthetic rubber is extruded from the tread extractor,
This is cooled, cut into a predetermined length, and tread 82
Is prepared. The tread 82 is attached to the outer peripheral surface of the tire assembly. The tire assembly is heated while the tire assembly is being inflated under pressure to produce a green tire having a predetermined shape. The green tire is vulcanized in a vulcanizer to cure the raw rubber. Further, after the final inspection, a steel radial tire 70 as shown in FIG. 23 was obtained.

[0050]

According to the steel radial tire of the present invention,
Steel cord core wire comes out of cord core
Since the cord core is sufficiently filled with rubber, fretting does not occur. Further, since the steel cord of the present invention has a flattened cross section, the shape retention of the cord is enhanced, and the twist of the core strand and the side wire is less likely to occur. For this reason, the warpage of the sheet does not substantially occur in the vicinity of the cut surface of the rubber sheet or in the far section.

Further, the steel cord of the present invention has two core wires and adopts a structure in which no void is formed in the core, so that the rubber has excellent rubber permeability and the core is sufficiently filled with rubber.

Further, the steel cord of the present invention has a wire diameter
Even if the ratio is increased, make sure the core wire is
Since it is difficult for the cords to come out, it is possible to ensure a sufficient pitch spacing of the cords in the calendering process without impairing the breaking strength, and it is possible to lay a large number of cords on the rubber sheet.

[Brief description of the drawings]

FIG. 1 is an overall schematic diagram showing a steel cord manufacturing line.

FIGS. 2A, 2B, and 2C are schematic diagrams showing a wire tension control device.

FIG. 3 is a schematic perspective view showing an arrangement relationship of each part of the double twister.

FIG. 4 is a schematic view showing a preformer for shaping a wire.

FIG. 5 is a schematic diagram showing a break-in roll in a double twister.

FIG. 6 is a diagram showing guide rollers provided on the entrance side and the exit side of the leveling roll section.

FIG. 7 is a diagram illustrating an intermediate roller of a leveling roll unit.

FIG. 8 is a cross-sectional view showing a steel cord (a perfect circular strand) before flattening.

FIG. 9 is a transverse sectional view showing the steel cord according to the first embodiment of the present invention.

FIG. 10 is a cross-sectional view showing a steel cord according to the first embodiment of the present invention.

FIG. 11 is a cross-sectional view showing a steel cord according to the first embodiment of the present invention.

FIG. 12 is a cross-sectional view showing a steel cord according to the first embodiment of the present invention.

FIG. 13 is an external view showing a part of the steel cord of the first embodiment viewed from a direction perpendicular to the long axis.

FIG. 14 is an external view showing a part of the steel cord of the first embodiment viewed from a direction orthogonal to the short axis.

FIG. 15 is a cross-sectional view showing a steel cord according to a second embodiment of the present invention.

FIG. 16 is a cross-sectional view showing a steel cord according to a second embodiment of the present invention.

FIG. 17 is a cross-sectional view showing a steel cord according to a second embodiment of the present invention.

FIG. 18 is a cross-sectional view showing a steel cord according to a second embodiment of the present invention.

FIG. 19 is a graph showing the relationship between the major axis of each example and the rubber permeability.

FIG. 20 is a graph showing the relationship between the flatness ratio and the rubber permeability of each example.

FIG. 21 is a plan view showing a calendar sheet before cutting.

FIG. 22 is a plan view showing a calendar sheet before cutting.

FIG. 23 is a cross-sectional view of a steel radial tire.

[Explanation of symbols]

 2,2A ... Steel cord 3,3A ... Core wire 4,4A ... Side wire

Claims (8)

(57) [Claims] 1. A strand formed by twisting a plurality of wires embedded in a rubber molded body and reinforcing the rubber molded body.
A steel cord consisting of, each typed index Kc and before the strand is flattened
And two core wires each having substantially the same diameter, and each having a molding ratio Ks before the strand is flattened.
Typed in, the heart its diameter is larger than the diameter of the wire, with a five and a side wires are substantially same diameter that are twisted together to collectively as heart wire around the heart wire, the heart The wire shaping rate Kc is equal to the side wire shaping rate Ks.
A steel cord which is larger and has a flat cross section of a strand comprising the five side wires and two core wires. 2. A cross section of a strand composed of five side wires and two core wires is formed in an elliptical shape, and the ratio of the major axis to the minor axis of the ellipse is in the range of 1.10 to 2.00. The steel cord according to claim 1, wherein: 3. The steel cord according to claim 1, wherein the ratio of the diameter of the side wire to the diameter of the core wire is in a range of 1.45 to 2.25. 4. The steel cord according to claim 1, wherein a steel wire having a tensile strength in a range of 300 to 360 kgf / mm ² is used for the core wire and the side wire. 5. A strand in which a plurality of wires are twisted.
A steel radial tire reinforced with a steel cord consisting of: each of said steel cords has a molding rate Kc before the strand is flattened.
And two core wires each having substantially the same diameter, and each having a molding ratio Ks before the strand is flattened.
Typed in, the heart its diameter is larger than the diameter of the wire, with a five and a side wires are substantially same diameter that are twisted together to collectively as heart wire around the heart wire, the heart The wire shaping rate Kc is equal to the side wire shaping rate Ks.
A steel radial tire having a larger cross-section and a flat cross section of a strand including the five side wires and the two core wires. 6. A cross section of a strand comprising five side wires and two core wires is formed in an elliptical shape, and the ratio of the major axis to the minor axis of the ellipse is in the range of 1.10 to 2.00. The steel radial tire according to claim 5 , characterized in that: 7. The method according to claim 1, wherein the ratio of the diameter of the side wire to the diameter of the core wire is in the range of 1.45 to 2.25.
The steel radial tire according to claim 5 . 8. The steel radial tire according to claim 5, wherein a steel wire having a tensile strength in a range of 300 to 360 kgf / mm ² is used for the core wire and the side wires.