JPH05186979A - Steel cord - Google Patents

Abstract

PURPOSE:To obtain the subject product, good in productivity, having sure rubber penetrability and capable of improving corrosion resistance while holding the cord tenacity by shaping a core filament of a steel cord having a (1+5) structure into a helical form. CONSTITUTION:The objective product is a steel cord having a sheath 2, composed of 5 sheath steel filaments 2 and arranged around a core steel filament 1. The core filaments 1 is shaped into a helical form so that the shaping ratio (Rc) defined by the formula Rc=Lc/dc(Lc is the amplitude of helical form shaping; dc is the element wire diameter of the core filament) may be 0.12-1 and the pitch (Pc) of the helical form shaping may satisfy the formula 3dc/0.34<=Pc<=10dc/0.34. The helical direction is opposite to the sheath twisting direction. The core filament 1 and the sheath filaments 2 preferably have the same diameter for enhancing the productivity.

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. More specifically, the present invention relates to a steel cord which suppresses corrosion propagation due to moisture or the like, improves corrosion propagation resistance, prevents the occurrence of a separation phenomenon, and can maintain cord strength.

[0002]

2. Description of the Related Art A product reinforced with a steel cord has a problem that the durability of the product is shortened due to corrosion of the steel cord filament due to moisture infiltrated into the product. For example, the steel cord used for the belt of a tire has a cavity inside the steel cord, and when the tire tread is injured enough to reach the belt, the moisture that has penetrated into the belt travels through the cavity inside the steel cord. Along the lengthwise direction, and as a result, rust due to water also diffuses, and the adhesive force between the rubber and the steel cord in that portion decreases, eventually leading to the occurrence of a separation phenomenon.

Therefore, in order to prevent such corrosion propagation, a cord structure has been proposed in which rubber is sufficiently penetrated into the cord through a gap between adjacent metal filaments by pressure vulcanization. As one of the above-mentioned cord structures, a cord having a so-called 1 + 5 structure in which five sheath filaments are arranged around one core filament has a gap between the sheath filaments, and rubber easily penetrates, and
Highly productive cords that are twisted in a twisting step are disclosed in JP-A-60-38208 and JP-A-59-1790.

However, in such a structure, even if the average sheath gap is sufficient, the arrangement of the sheaths is biased, and the portions where the sheaths come into close contact with each other are produced. There was a drawback that some parts did not.

Further, in the 1 + 5 structure as disclosed in JP-A-56-131404, since the core filament diameter is smaller than the sheath filament diameter, the spacing between the sheath filaments is narrowed and it is difficult for rubber to enter, and the core filament is also small. However, there is a drawback that the effect of molding is lowered because the rigidity of the mold is weakened, and the strength is lowered even when the mold ratio is increased to improve the permeability of rubber.

Further, the means for increasing the core filament diameter to be larger than the sheath filament diameter, ensuring a certain gap between adjacent sheath filaments, and allowing rubber to penetrate into the inside also increases the weight of the cord, The productivity is also deteriorated, and the sheath filaments are partially biased so that the sheath filaments come into close contact with each other, so that the rubber does not penetrate and sufficient corrosion propagation resistance cannot be obtained.

In Japanese Utility Model Publication No. 56-14396, a steel is formed by bending a core wire into a helical shape and twisting a plurality of side wires (sheath) around the outer circumference of the core wire without contacting each other. The code is disclosed. However, according to the research by the present inventor, this effect cannot be obtained by bending the core in a helical shape and disposing a plurality of sheaths on the outer periphery of the core. In order to obtain corrosion propagation, it was found that it is important to define the casting ratio and pitch, which depend on the number of sheaths, and the direction of the helix.

Further, in the steel cord of the 3 + 6 structure which is the embodiment of this publication, the productivity is poor because the core is composed of three cords, and it is difficult for the rubber to penetrate into the central portion of the three core filaments. There was a doubt about the effect of rubber permeability because a space is easily formed and the direction of molding is not specified by this method.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to take a structure in which one core filament is spirally shaped, and 5, 6, 7 and 8 sheath filaments are arranged on the outer periphery thereof, respectively. It is possible to keep the sheath filaments in a state where they do not come into contact with each other with reliability, good productivity, reliable rubber penetration, and while maintaining a large cord strength,
It is to provide a steel cord having improved corrosion propagation resistance.

[0010]

The present inventor has conducted earnest research to solve the above-mentioned problems, and as a result, 1 + 5, 1+
By appropriately molding the core steel filaments of 6, 1 + 7, 1 + 8 structure, it is possible to easily form the sheath filaments in a state where they do not contact each other surely, and it is possible to stabilize enough rubber on the steel cord after pressure vulcanization. The present invention has been completed by finding that it can be penetrated.

That is, the present invention comprises (1) one core steel filament and five sheath steel filaments arranged around the core, the core filament being shaped in a spiral shape, and the spiral The shaping ratio Rc, that is, L, which is represented by the ratio of the shaping amplitude Lc to the strand diameter dc of the core filament.
c / dc is in the range of 0.12 ≦ Rc ≦ 1.0, and the pitch Pc of the spiral mold is 3.0 dc / 0.34.
A steel cord for reinforcing rubber articles, which has a range of ≦ Pc ≦ 10.0 dc / 0.34 and in which the spiral direction is opposite to the sheath twisting direction,

(2) It is composed of one core steel filament and six sheath steel filaments arranged around the core, and the core filament is helically shaped, and the amplitude Lc of the helical shaping. Of the core filament diameter dc and the molding ratio Rc, that is, Lc / dc, is in the range of 0.12 ≦ Rc ≦ 1.5, and the pitch Pc of the spiral molding is 3.0d.
A steel cord for reinforcing rubber articles, wherein c / 0.34 ≦ Pc ≦ 10.0 dc / 0.34, and the spiral direction is opposite to the sheath twist direction.

(3) One core steel filament and seven sheath steel filaments arranged around the core, the core filament is spirally shaped, and the amplitude Lc of the spiral shaping is And the core filament diameter dc, the molding ratio Rc, that is, Lc / dc, is in the range of 0.42 ≦ Rc ≦ 1.8, and the spiral molding pitch Pc is 3.0d.
A steel cord for reinforcing rubber articles, wherein c / 0.34 ≦ Pc ≦ 10.0 dc / 0.34, and the spiral direction is opposite to the sheath twist direction.

(4) One core steel filament and eight sheath steel filaments arranged around the core. The core filament is spirally shaped, and the spiral shaping amplitude Lc. Of the core filament and the filament diameter dc of the core filament have a molding ratio Rc, that is, Lc / dc in the range of 0.74 ≦ Rc ≦ 2.12, and the spiral molding pitch Pc is 3.0.
A steel cord for reinforcing a rubber article, which has a dc / 0.34 ≦ Pc ≦ 10.0 dc / 0.34 range and the spiral direction is opposite to the sheath twisting direction,

(5) Carbon content is 0.80 to 0.85
The steel cord according to any one of the above items (1), (2), (3) and (4), which is in a weight percentage,

(6) The steel cord according to any one of (1), (2), (3), (4) and (5) above, wherein the core filament diameter dc and the sheath filament diameter ds are substantially dc = ds. is there.

In the present invention, when one core filament is spirally shaped, when one core filament is formed, a cavity may be formed therein as in the case of a plurality of cores, and a portion where rubber does not penetrate may occur. The reason for this is that since the stress is not concentrated in the spiral shape, the fatigue resistance is good and the strength is excellent.

Here, the mold ratio Rc of the core filament is set to 5 when the number of sheath filaments is 0.12≤Rc≤1.0 and when the number of 6 sheath filaments is 0.12≤Rc≤1.5 and 7 of the sheath filaments. In case of book 0.42 ≤ Rc ≤ 1.8 In case of 8 sheath filaments 0.74 ≤ Rc ≤ 2.12 was set so that when Rc is smaller than the value on the left side, Dispersing the arrangement, ensuring the proper gap between the sheaths, the effect of permeating the rubber inside the cord is insufficient,
On the contrary, when Rc exceeds the value on the right side, the cord properties are poor, and when a tensile load is applied to the cord, the stress is not uniformly applied and the cord strength is reduced.

Further, the pitch Pc with the spiral mold of the core is set to 3.0 dc / 0.34≤Pc≤10.0 dc / 0.34.
The reason is that if Pc is greater than 10.0 dc / 0.34, the sheath arrangement is dispersed, the sheath gap is properly secured, and the effect of permeating the rubber inside the cord is insufficient.
Is less than 3.0 dc / 0.34, the strength of the core filament is reduced due to the load on the core filament at the time of molding, and the core filament and the sheath filament are not evenly loaded during the tensile load to the cord. As a result, the code strength is reduced. In the present invention, the molding ratio Rc and the spiral molding pitch Pc are determined by measuring the steel cord taken out from the rubber article without applying plastic deformation.

The reason why the spiral direction with the core type is opposite to the sheath twisting direction is that twisting in the same direction increases the length of contact between the core and the same sheath filament.
The two sheath filaments come into contact with the core, and the part where rubber does not enter (the upper right part in Fig. 4) is connected in the longitudinal direction,
This is because the corrosion propagation resistance deteriorates.

As a reinforcing material, in order to secure the strength of the composite and reduce the weight thereof, the carbon content is 0.80 to 0.8.
It is desirable to use a steel filament composed of 5% by weight of high tensile strength steel.

Further, when a filament having a core filament diameter smaller than that of the sheath filament diameter is used, the problem as described in paragraph number 5 occurs, and when the core filament diameter is larger than the sheath filament diameter, it is described in paragraph number 6. Such problems arise. Therefore, it is preferable to make the core filament diameter dc and the sheath filament diameter ds substantially equal to each other from the viewpoint of improving the productivity in the manufacturing process.

[0023]

EXAMPLES The present invention will be described in more detail with reference to the following examples and comparative examples, but it goes without saying that the present invention is not limited to these examples. The core die attachment ratio Rc, core spiral pitch Pc, cord structure, core strand diameter dc, sheath strand diameter ds, sheath twist pitch Ps, core die attached spiral direction, sheath described in the upper column of Tables 1 to 6 Size 1 with a belt containing steel cords with twist direction
Three 0.00R20 radial tires for trucks and buses
Two types of prototypes were made, and the corrosion propagation resistance (separation resistance) and cord strength of each tire were examined. The results are shown in the lower column of each table. The spiral direction,
Z and S in the sheath twisting direction are defined by JIS G 3510.

The corrosion propagation resistance is determined by taking out 100 mm of the belt cord with the rubber covered from the tire, covering the side surface with a silicone sealant, and immersing one end of the cord in a 10% NaOH aqueous solution to cut only the cut surface. An aqueous solution was allowed to infiltrate, and after soaking for 24 hours, the rubber was pinched with a pair of pliers and peeled off. The exposed portion of the metal was defined as a corrosion propagation portion, and its length (mm) was evaluated.

[0025]

[Table 1]

[0026]

[Table 2]

[0027]

[Table 3]

[0028]

[Table 4]

[0029]

[Table 5]

[0030]

[Table 6]

In Table 4, Comparative Examples 1 to 6 have a 1 + 5 structure, and Comparative Example 1 has a core die attachment ratio Rc of 0.12.
When it is smaller, the corrosion propagation resistance is inferior to 85 mm. In Comparative Example 2, the core spiral pitch Pc is smaller than 3.0 dc / 0.34, and the cord strength is deteriorated. Comparative Example 3
If the core die attachment ratio Rc is larger than 1.0, the cord strength is deteriorated. Comparative Example 4 has a core spiral pitch Pc of 10.
When it is larger than 0 dc / 0.34, the corrosion propagation resistance is 1
It is inferior to 00 mm. In Comparative Example 5, the spiral direction is the same as the sheath twisting direction, and the corrosion propagation resistance is 55 mm, which is inferior. In Table 5, Comparative Example 6 has a core die attachment ratio Rc of more than 1.0, and the cord strength is deteriorated.

Comparative Examples 7 to 14 are in the case of the 1 + 6 structure, and Comparative Example 7 is inferior in corrosion propagation resistance of 100 mm when the core die coverage Rc is smaller than 0.12. In Comparative Example 8, when the core spiral pitch Pc is smaller than 3.0 dc / 0.34, the cord strength is deteriorated. Comparative Example 9 has a core type attachment rate R
When c is greater than 1.5, the cord strength deteriorates.
Comparative Example 10 has a core spiral pitch Pc of 10.0 dc /
When it is larger than 0.34, the corrosion propagation resistance is inferior to 100 mm. In Table 6, in Comparative Examples 11 and 12, the cores are not molded, and not only the corrosion propagation resistance is inferior, but also the cord strength is deteriorated when the sheath wire diameter is reduced. In Comparative Example 13, the direction in which the core mold is attached is the same as the direction in which the sheath is twisted, and the corrosion propagation resistance is poor. In Comparative Example 14, the cord strength is deteriorated when the core die attachment ratio is larger than 1.5 (all of the wire diameters are small, 0.23 mm).

Comparative Example 15 has a 1 + 7 structure, and the core die attachment rate R
When c is less than 0.42, the corrosion propagation resistance is poor.
Comparative Example 16 has a 1 + 8 structure and a core die attachment rate Rc of 0.74.
When it is smaller, the corrosion propagation resistance is poor.

[0034]

EFFECTS OF THE INVENTION The steel cord of the present invention has good productivity, is not affected by variations in the manufacturing process, and retains the strength of the cord while having good corrosion propagation resistance. When used in a rubber composite such as a tire, the durability can be improved and the service life thereof can be greatly improved.

[Brief description of drawings]

FIG. 1 is a view showing one section of a steel cord having a 1 + 5 structure according to the present invention.

FIG. 2 is a conventional steel cord of 1 + 5 structure 1
FIG.

FIG. 3 is a view of a spirally-shaped core filament as viewed from a direction perpendicular to the spiral axis, showing the core wire diameter dc,
It is explanatory drawing of spiral amplitude Lc and spiral pitch Pc.

FIG. 4 is a cross-sectional view showing a portion in which the core spiral direction and the sheath twisting direction are the same, and the sheaths are in contact with each other.

FIG. 5 is a sectional view of a steel cord having a 1 + 6 structure according to the present invention.

FIG. 6 is a sectional view of a steel cord having a 1 + 7 structure according to the present invention.

FIG. 7 is a sectional view of a steel cord having a 1 + 8 structure according to the present invention.

[Explanation of symbols]

 1,3 core filament 2,4 sheath filament dc core filament diameter Lc core filament spiral amplitude Pc core filament spiral pitch

Claims (6)

[Claims] 1. A core steel filament and five sheath steel filaments arranged around the core, wherein the core filament is helically shaped, and an amplitude Lc of the helical shaping. Molding rate Rc represented by the ratio to the core wire diameter dc of the core filament
That is, Lc / dc is in the range of 0.12 ≦ Rc ≦ 1.0, and the pitch Pc of the spiral mold is 3.0 dc /
A steel cord for reinforcing a rubber article, which is in a range of 0.34 ≦ Pc ≦ 10.0 dc / 0.34 and the spiral direction is opposite to the sheath twisting direction. 2. A core steel filament and six sheath steel filaments arranged around the core, wherein the core filament is helically shaped, and an amplitude Lc of the helical shaping. Molding ratio Rc represented by the ratio to the core wire diameter dc of the core filament
That is, Lc / dc is in the range of 0.12 ≦ Rc ≦ 1.5, and the pitch Pc of the spiral mold is 3.0 dc /
A steel cord for reinforcing a rubber article, which has a range of 0.34 ≦ Pc ≦ 10.0 dc / 0.34, and the spiral direction is opposite to the sheath twisting direction. 3. A core steel filament and seven sheath steel filaments arranged around the core, wherein the core filament is helically shaped, and an amplitude Lc of the helical shaping. Molding ratio Rc represented by the ratio to the core wire diameter dc of the core filament
That is, Lc / dc is in the range of 0.42 ≦ Rc ≦ 1.8, and the pitch Pc of the spiral mold is 3.0 dc /
A steel cord for reinforcing a rubber article, which is in a range of 0.34 ≦ Pc ≦ 10.0 dc / 0.34 and the spiral direction is opposite to the sheath twisting direction. 4. A core steel filament and eight sheath steel filaments arranged around the core, wherein the core filament is helically shaped, and an amplitude Lc of the helical shaping. Molding ratio Rc represented by the ratio to the core wire diameter dc of the core filament
That is, Lc / dc is in the range of 0.74 ≦ Rc ≦ 2.12, and the pitch Pc of the spiral forming is 3.0 dc /
A steel cord for reinforcing a rubber article, which is in a range of 0.34 ≦ Pc ≦ 10.0 dc / 0.34 and the spiral direction is opposite to the sheath twisting direction. 5. The carbon content is 0.80 to 0.85% by weight.
The steel cord according to claim 1, 2, 3, or 4. 6. The core filament diameter dc and the sheath filament diameter ds are substantially dc = ds.
The steel cord according to any one of 2, 3, 4, and 5.