JP2000336584A - Steel cord for reinforcing rubber article, its production and pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a steel cord useful for pneumatic radial tires excellent in durability by application thereof to reinforcement of belts by forming a cord of a flat contour shape of sheath filaments arranged into a ply lay structure on the periphery of a core of doubled plural steel filaments. SOLUTION: This steel cord fore reinforcing rubber articles is obtained by using steel filaments having 0.10-0.50 mm diameter and arranging a sheath comprising the 5-10 filaments having the same diameter as that of filaments in a core of the 3 filaments doubled without being twisted or arranging the 5-12 sheath filaments having the diameter different from that of the core filaments in a ply lay structure with a buncher stranding machine. The diameter d of the filaments constituting the cord and major axis Dl of the cord contour satisfy the relationship of 5.00d<D1>=7.48d or the core filament diameter dc, the sheath filament diameter ds and the major axis Dl satisfy the relationship of 2.00×(1.5 dc+ds)<D1<=3.38×(1.5 dc+ds).

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 as a reinforcing material for rubber articles such as pneumatic tires and industrial belts, and more particularly to improving durability.

[0002]

2. Description of the Related Art Conventionally, steel cords have been widely used as reinforcing materials for rubber articles such as rubber hoses, conveyor belts and pneumatic tires. For example, a pneumatic tire that is a typical example of a rubber article, in particular, a heavy duty pneumatic tire used for trucks and buses, is obtained by twisting steel filaments having the same wire diameter by changing the twist pitch for each layer.
A steel cord having a +15 structure was used as a reinforcing material for the belt. The steel cord includes a core made of three steel filaments, an inner sheath made of nine steel filaments arranged around the core, and fifteen steel filaments arranged around the inner sheath. An outer sheath is formed. When the cord is embedded in rubber, there is no gap in the outer periphery of the cord with the cavity inside the cord, so that the rubber cannot enter the inside of the cord, so that there is a disadvantage that the cavity is left inside the cord. That is, when the moisture that has penetrated into the rubber from the damage of the rubber article reaches the cord, the moisture penetrates into the cavity inside the cord, causing corrosion of the cord and peeling of the cord from the rubber.

[0003] Therefore, Japanese Patent Application Laid-Open No. 10-8387 discloses a core comprising two or more steel filaments arranged without twisting, and a sheath comprising a plurality of steel filaments arranged around the core. Flat steel cords have been proposed. In the cord, since a gap is formed between the sheath filaments, it is possible to ensure that the rubber enters the inside of the cord.

[0004]

This cord has a structure in which a plurality of molded sheath filaments are arranged around a core of three filaments, and a gap is formed between the sheath filaments. Contour of the cord observed in a cross section orthogonal to the axial direction of the cord,
That is, the outer shape of the cord is characterized by being relatively large. This kind of cord, for example, in the calendering process and vulcanization process during tire manufacturing, when tension is applied to the cord, because there is a gap between the sheath filaments and there is room for the molding of each filament to be extended as it is, A large tensile residual stress occurs in the filament,
This has caused a decrease in the fatigue resistance of the cord.
That is, in the cord having the large tensile residual stress, a crack is easily generated from a portion having a large residual stress as a starting point, and the filament is easily broken with the progress of the crack, so that the fatigue life of the cord is shortened. .

In particular, in a buncher stranded wire machine, it is mechanically difficult to wind a sheath filament along a core, and the outer shape of the cord becomes large. That is, when a cord having a 3 + N structure having a core made of three filaments is manufactured by a buncher twisting machine, an elliptical open cord having a 1 × N structure is arranged around a core made of three filaments. . Such flat cords are inferior in the fatigue resistance of the cords because they cause a larger residual stress to be generated with respect to the tension applied during the production of the cords.

Accordingly, the present invention advantageously suppresses a decrease in fatigue resistance when a tension is applied to a cord of a cord having a large outer shape and having a sheath arranged around a flat core. And a pneumatic tire having excellent durability.

[0007]

The gist of the present invention is as follows.
It is as follows. (1) A steel cord having a layered structure in which a sheath of 5 to 10 filaments having the same diameter as the core filament is arranged around a core in which three filaments are arranged in parallel without being twisted, When the diameter of the filament constituting the cord is d, the major diameter Dl in the outer shape of the cord
Satisfies the following formula: Note 5.00d <Dl ≦ 7.48d

(2) A steel cord having a layer twist structure in which a sheath of 5 to 12 filaments having different diameters from the core filament is arranged around a core in which three filaments are arranged in parallel without being twisted. A steel cord for reinforcing rubber articles, characterized in that, when the diameter of the filament constituting the core is dc and the diameter of the filament constituting the sheath is ds, the major diameter Dl in the outer shape of the cord satisfies the following expression. . Note 2.00 × (1.5 dc + ds) <Dl ≦ 3.38 × (1.5 dc +
ds)

(3) In the above (1) or (2), the outer shape of the core has a relation of 1.82 ≦ cl / cs ≦ 3.00, where the major axis is cl and the minor axis is cs. Steel cord for reinforcing rubber articles.

(4) In the above (1), (2) or (3),
The diameter of the filament constituting the cord is 0.10 to 0.5
A steel cord for reinforcing rubber articles, which is 0 mm.

(5) A steel cord for reinforcing rubber articles according to any one of the above (1) to (4), which is produced by a buncher stranded wire machine.

(6) In producing the steel cord according to any one of the above (1) to (5) with a buncher twisting machine, a molding amount of a filament constituting a sheath is independently controlled. Steel cord manufacturing method.

(7) A pneumatic tire having a carcass extending in a toroidal shape between a pair of bead portions and having at least two layers of belts on a radially outer side of the carcass. A pneumatic tire to which the steel cord according to any of the above is applied.

[0014]

FIG. 1 shows a steel cord 1 applied to a tire belt or the like according to the present invention.
Is shown for the twisted structure 3 + 9. The steel cord is obtained by twisting a sheath 5 of nine steel filaments 4 having the same diameter as the filament 2 of the core 3 around a core 3 in which three steel filaments 2 are arranged in parallel without being twisted. Become. When the core filament 2 and the sheath filament 4 have the same diameter, the other 3 + 5,
3 + 6, 3 + 7, 3 + 8 and 2 + 10 structures are suitable.

A cord 1 having a twisted structure 3 + 9 shown in FIG. 2 has a diameter different from that of the filament 2 of the core 3 around a core 3 in which three steel filaments 2 are similarly arranged in parallel without being twisted. Is formed by twisting the sheath 5 of the nine steel filaments 4. In addition, core filament 2
If the sheath filament 4 and the sheath filament 4 have different diameters,
5, 3 + 6, 3 + 7, 3 + 8, 3 + 10, 3 + 11 and 3
+12 structure is suitable. In each of the cord structures, the core is preferably not twisted, but unintended twisting and twisting need not be particularly restricted. On the other hand, it is possible to apply a shaping or the like to the filament constituting the core.

Here, the number of sheath filaments 4 arranged around the core 3 is 5 to 10 when the core and the sheath have the same diameter, and 5 to 12 when the core and the sheath have different diameters. ,limit. That is, when the number of filaments is less than 5, the cord strength is reduced, and it is necessary to increase the number of cords driven into, for example, a tire belt. As a result, the belt is peeled off from the rubber at the cord end of the belt. This is because the performance against the separation generated at the end, that is, the so-called belt end separation resistance is reduced. On the other hand, if the number of filaments exceeds 10 or 12, the gap between the sheath filaments becomes smaller,
Rubber penetration deteriorates.

Further, when the diameter of the filaments of the core and the sheath is the same, when the diameter of the filament is d,
It is important that the major axis Dl in the outer shape of the cord satisfies the following expression (1). Note 5.00d <Dl ≦ 7.48d ---- (1)

Similarly, when the filament diameter of the core and the sheath is different, the diameter of the filament constituting the core is dc, and the diameter of the filament constituting the sheath is d.
When s is set, it is important that the major axis Dl in the outer shape of the cord satisfies the following expression (2). 2.00 × (1.5 dc + ds) <Dl ≦ 3.38 × (1.5 dc + ds) --- (2)

That is, when the major diameter Dl of the cord exceeds 7.48 d when the core and the sheath have the same diameter, and 3.38 × (1.5 dc + ds) when the core and the sheath have different diameters, the cord is particularly manufactured by buncher twist. In the cord, since the twist is tightened by the tension applied at the time of manufacturing the tire, a residual stress is generated in each filament, so that the fatigue resistance of the cord is deteriorated. Therefore, it is important to regulate the major axis of the cord to each of the above ranges.

Although there is no particular limitation on the lower limit, if the outer shape of the cord is a perfect circle, the deterioration phenomenon of fatigue resistance, which is a problem in the present invention, rarely occurs. When the core and sheath have the same diameter
5.00d, and 2.00 × (1.5
dc + ds).

On the other hand, as shown in FIG. 3, the core preferably has a relationship of 1.82 ≦ cl / cs ≦ 3.00, where cl is the major axis and cs is the minor axis in its outer shape. This is because if the ratio is less than cl / cs1.82, the gap between the core and the sheath filament is small, and the rubber penetration is deteriorated. The upper limit of cl / cs is 3.0, which is a state in which three filaments are arranged in a line.

The diameter of the filament constituting the cord is preferably in the range of 0.10 to 0.50 mm. That is, if the diameter of the filament is less than 0.10 mm, it is necessary to increase the number of driving of the cord because the belt rigidity when applied to a tire belt is reduced,
As a result, the adjacent cords are narrowed, and the separation of the rubber at the cord ends is easily connected between the adjacent cords. As a result, the separation at the belt ends is caused and the so-called belt end separation resistance is deteriorated. On the other hand, if the diameter of the filament exceeds 0.50 mm, there is a possibility that the cord may be broken on the belt, for example, when the tire runs on a rough road or the like due to an increase in the amount of bending distortion in the filament.

Next, a method of manufacturing the cord according to the present invention will be described in detail with reference to FIG. Here, a manufacturing method using a buncher stranded wire machine, in which it is difficult to regulate the cord outer shape to an appropriate range, will be described. However, even with a tubular stranded wire machine in which the control of the twist form of the cord is easier than that of the buncher stranded wire machine. Of course, the cord of the present invention can be manufactured.

In order to manufacture a cord using this buncher stranded wire machine, first, as shown in FIG.
After sending out 4 to 8 filaments 4 a to be sheaths from the respective unwinding reels 7, the filaments 4 a are subjected to a predetermined molding by passing through a molding device 8.
Then, the core filament 2a and the sheath filament 4a are gathered and twisted together with the voice 9 so that the sheath filament 4a is arranged around the core filament 2a, for example, under tension control by a roll pair, thereby obtaining a cord. Can be Next, the cord is wound on a take-up reel 10, but immediately before the roll
It is preferable to make the cord outer shape flat at 11.

The amount of the sheath filament to be molded is
It can be controlled by adjusting the distance between the setting pins in the molding device 8 or the tension of the filament.
For example, in order to reduce the amount of shaping of the sheath filament, it is only necessary to reduce the distance between the shaping pins in the shaping device 8. Thus, by controlling the amount of molding of the sheath filament independently, the outer shape of the cord expected in the present invention can be obtained.

The above-mentioned cord is used for reinforcing a carcass by applying a ply formed by embedding a large number of cords in parallel to each other and burying them in a rubber sheet to a belt of a tire. Here, as the tire, for example, a truck / bus tire shown in FIG. 5 is advantageously adapted. The tire has a carcass 21 composed of a ply of an organic fiber cord extending in a toroidal shape in a radial direction between a pair of bead cores 20, and at least four carcasses 21 arranged outside a crown portion of the carcass 21 in a tire radial direction.
The belt 22 includes a layered belt 22 and a tread 23 disposed radially outward of the belt 22.

The belt 22 has a laminated structure of four layers in the illustrated example. The belt 22 is inclined with respect to the ply cord of the carcass 21 and preferably has a ply of a plurality of steel cords arranged at an inclination angle of 10 to 30 °. It has a structure in which a plurality of sheets are overlapped in an arrangement in which steel cords cross each other between the layers. The present invention is characterized in that the above-mentioned cord is applied to the steel cord constituting the belt 22.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A belt of a radial tire for trucks and buses of size 10.00 R20 14PR shown in FIG. 5 is provided with a cord having the specifications shown in Tables 1 and 2 so that the axial direction of the cord is 20 to the equatorial plane of the tire. It was applied in an arrangement with a tilt angle of °. The tires thus obtained were examined for rubber penetration, belt cord breakage resistance and belt end separation resistance. The results of these investigations are shown in Tables 1 and 2.

Table 1 is a comparison of the 3 + N structure in which the core and the sheath have the same filament diameter. That is, Inventive Example 1 uses a cord with a buncher twist 3 + 8 structure, and Inventive Example 2 uses a cord with a buncher twist 3 + 5 structure. Inventive Examples 1 and 2 are compared with Comparative Example 1 having a 3 + 4 structure, in comparison with belt end separation. It can be seen that the property has been improved. Further, it can be seen that Invention Examples 1 and 2 have improved rubber penetration compared to Comparative Example 2 having a 3 + 11 structure. Inventive Example 3 has a filament diameter of 0.14 mm.
In the case of Inventive Example 4, the filament diameter is 0.48 mm, and it can be seen that the belt end separation resistance is improved as compared with Comparative Example 3 in which the filament diameter is 0.08 mm. In addition, Invention Examples 3 and 4 have a filament diameter of
As compared with Comparative Example 4 which is 0.54 mm, it can be seen that the belt cord break resistance is improved. Inventive Example 5 is a case where the major axis of the cord is 7.03 times the filament diameter, and shows that the belt cord breakage resistance is improved as compared with Comparative Example 5 which is 7.80 times the same as the filament diameter. Invention Example 6 had cl / cs of 1.92.
This shows that the rubber penetration was superior to that of Inventive Example 7 in which cl / cs was 1.69.

[0030]

[Table 1]

Next, Table 2 shows a comparison of the 3 + N structure in which the filament diameters of the core and the sheath are different. That is, Inventive Example 8 is the case of the 3 + 9 structure of the buncher twist, and it can be seen that Inventive Example 8 has improved belt end separation resistance as compared with Comparative Example 6 which is the 3 + 4 structure of the different wire diameter. In addition, Invention Example 8 has a different wire diameter of 3+
It can be seen that the rubber penetration is improved as compared with Comparative Example 2 having 13 structures. Inventive Example 9 has a core filament diameter of 0.16 mm and a sheath filament diameter of 0.14 mm, and Inventive Example 10 has a core filament diameter of 0.48 mm and a sheath filament diameter of 0.46 mm.
As compared with Comparative Example 8 in which the diameter of the sheath filament is 09 mm and the diameter of the sheath filament is 0.08 mm, it is understood that the belt end separation resistance is improved. In addition, it can be seen that Invention Examples 9 and 10 have improved belt cord breaking resistance as compared with Comparative Example 9 in which the core filament diameter is 0.54 mm and the sheath filament diameter is 0.52 mm. Invention Example 11 has a cord major axis of (1.
5 × core filament diameter + sheath filament diameter)
This is a case of 10 times, and it is understood that the belt cord break resistance is improved as compared with Comparative Example 10 which is 3.51 times (1.5 × core filament diameter + sheath filament diameter).

[0032]

[Table 2]

Here, the rubber penetration is measured by taking out a steel cord from a belt of a test tire, measuring the amount of rubber adhered on the peripheral surface of the core, and measuring the measured value on the peripheral surface of the core. 100% when rubber is adhered to all,
The case where no adhesion was observed was evaluated as 0%.

The breaking resistance of the belt cord depends on the internal pressure of the tire.
After adjusting to 725 kPa and installing it on the standard rim, it was mounted on an actual vehicle, the tires were rehabilitated after traveling 30,000 km on bad roads, and after traveling 30,000 km, the tires were dissected and the carcass side of the belt was disassembled. From the third belt layer, the number of broken cords was measured, and the result was expressed as an index by the following equation. The smaller the index is, the smaller the number of cord breaks is, indicating that the belt cord is more resistant to breakage. In addition, the code | cord which manufactured the code | cord | chord which has the same cord structure and filament diameter as Invention Example 1 in Table 1 and Invention Example 6 in Table 1 by the tubular stranded wire machine was applied to the reference tire. (Break resistance index of belt cord) = (Number of cord breaks in test tire) / (Number of cord breaks in reference tire) x 1
00

Since the belt end separation resistance is largely governed by the magnitude of the crack length at the belt end, the crack length is used as a proxy for the belt end separation. That is, in this test, the internal pressure was 725 k
The tire adjusted to Pa and mounted on the standard rim is mounted on an actual vehicle, and after traveling 100,000 km on a general road, the tire is dissected and generated at the edge of the third layer of the belt layer from the carcass side of the belt. The crack length was measured, and the result was expressed as an index by the following equation. The smaller the index is, the shorter the crack length is, indicating that the belt end separation resistance is excellent. The reference tire is the same as in the case of the above-described belt cord breaking resistance. (Belt end segregation resistance index) = (Crack length of test tire) / (Crack length of reference tire) × 100

[0036]

According to the present invention, the fatigue resistance of a cord having a 3 + N structure having a core composed of three filaments can be improved. By applying this cord to a belt, it can be used on a rough road or unpaved road. Even under extremely severe use conditions such as running on a road, cord breakage is avoided, so that a tire having excellent durability can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view of a steel cord having a 3 + 9 structure according to the present invention.

FIG. 2 is a sectional view of a steel cord having a 3 + 9 structure according to the present invention.

FIG. 3 is a view showing a filament arrangement in a core of a steel cord.

FIG. 4 is a view showing a buncher stranded wire machine used in the present invention.

FIG. 5 is a sectional view of a tire according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Steel cord 2 Core filament 3 Core 4 Sheath filament 5 Sheath 6 Unwinding reel 7 Unwinding reel 8 Molding device 9 Voice 10 Take-up reel 11 Rolling roller 20 Bead core 21 Carcass 22 Belt 23 Tread

Claims (7)

[Claims] 1. Around a core in which three filaments are aligned in parallel without being twisted, a 5 filament having the same diameter as the core filament is provided.
A steel cord having a layered structure in which a sheath of up to 10 filaments is arranged, wherein the diameter of the filament constituting the cord is d, and the major diameter Dl in the outer shape of the cord satisfies the following expression. Steel cord for reinforcing rubber articles. Note 5.00d <Dl ≦ 7.48d 2. Around a core in which three filaments are arranged in parallel without being twisted, 5 cores having a different diameter from the core filament are provided.
A steel cord having a layered structure in which a sheath composed of up to 12 filaments is arranged, where the diameter of the filament constituting the core is dc and the diameter of the filament constituting the sheath is ds, the major diameter Dl in the outer shape of the cord Satisfies the following formula: Note 2.00 × (1.5 dc + ds) <Dl ≦ 3.38 × (1.5 dc +
ds) 3. The outer shape of the core according to claim 1 or 2, wherein the major axis is cl and the minor axis is cs.
A steel cord for reinforcing rubber articles, characterized by satisfying a relation of 1.82 ≦ cl / cs ≦ 3.00. 4. The steel cord for reinforcing rubber articles according to claim 1, wherein the diameter of the filament constituting the cord is 0.10 to 0.50 mm. 5. The method according to claim 1, wherein
A steel cord for reinforcing rubber articles, which is produced by a buncher stranded wire machine. 6. In producing the steel cord according to any one of claims 1 to 5 with a buncher stranding machine,
A method for producing a steel cord, characterized in that the amount of filaments forming a sheath is independently controlled. 7. A pneumatic tire having a carcass extending in a toroidal shape between a pair of bead portions and having at least two layers of belts on a radially outer side of the carcass, wherein the belts have the following constructions. A pneumatic tire to which any one of the steel cords described above is applied.