JPH0730714Y2 - Steel cord for reinforcing rubber products - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a steel cord for reinforcing rubber products used as a rubber reinforcing material for automobile tires, conveyor belts and the like.

[Prior Art] Generally, a so-called closed twisted cord in which a plurality of element wires as shown in Fig. 3 are closely contacted and twisted is used for this type of steel cord.

The steel cords (4) are covered with rubber in a state where a plurality of the steel cords are aligned in parallel and are used as a rubber product reinforcing material for automobile tires, conveyor belts and the like.

By the way, an indispensable requirement as a rubber product reinforcing material is to have excellent fatigue resistance. In other words, if the steel cord has excellent strength and is a complete composite with rubber and has excellent fatigue resistance, it will prolong the life of the rubber product and improve its safety. Can fully fulfill the role of.

However, in the above steel cord (4),
Since the individual strands (5) of the cord are intimately twisted together, when the composite sheet of the cord and rubber is formed,
The rubber cannot penetrate into the cord from between the strands (5) and (5) and only covers the outer circumference of the cord, and the cavity E is continuously present inside the cord over the length of the cord. It will be.

Therefore, when the steel cord (4) is used for a tire, for example, the rubber and the cord are not sufficiently adhered to each other, so that the cord and the rubber are separated from each other when the automobile runs.
A so-called separation phenomenon is caused to significantly reduce the function of the tire, and moisture in the rubber or moisture that has penetrated from the cuts in the tire reaches the inside of the hollow portion E inside the cord and propagates along the length of the cord to corrode the cord. This leads to a reduction in the mechanical strength of the cord, and the fatigue resistance is greatly reduced.

In recent years, in view of the above circumstances, various steel cords having a structure capable of improving the adhesiveness between the steel cord and rubber have been proposed.

For example, Japanese Patent Laid-Open No. 55-90692 discloses a so-called open twisted cord, in which the twisted wires are twisted while providing a gap C between the wires (6) and (6) as shown in FIG. Disclosed is a steel cord (7).

[Problems to be solved by the invention] In the steel cord (7), in order for rubber to sufficiently infiltrate into the cord, the gap C between the wires (6) and (6) is set to 0.01 mm or more. There is a need.

However, if the above-mentioned gap C is sufficiently taken, the free space in which each wire (6) can move becomes large, and the twisted structure tends to become unstable at the time of manufacturing the steel cord, as shown in Fig. 5 (a) and (b). As shown, the strands (6) are offset, and the twists are uneven in the longitudinal direction of the cord.

Further, since the steel cord (7) has a large elongation under an extremely low load, not only the handling property and the workability at the time of molding the composite sheet are poor, but also the above-mentioned gap is caused by the low load tension applied at the time of molding the composite sheet. C decreases, and eventually becomes the same as the steel cord (4) shown in FIG. 3, the rubber does not sufficiently penetrate into the cord, and therefore it does not become a complete composite with the rubber, which causes the above-mentioned harmful effects. It was supposed to be.

Further, in each of the steel cords (4) and (7), when stress is applied to the unevenness of the road when driving a car or when riding on pebbles, since the circumscribed circle of the cord is substantially circular, it is bent. The rigidity was large, and excessive deformation was caused, which was a cause of deterioration in fatigue resistance.

The present invention has been made in view of the above problems, and an object thereof is to provide a steel cord having excellent fatigue resistance, capable of extending the life of a rubber product, particularly a tire, and improving safety. Especially.

[Means for Solving the Problems] In order to achieve the above object, the steel cord of the present invention is
At least one strand of the multiple strands that make up the cord is provided with a small spiral habit other than the twisted habit, and the interior of the cord is between this strand and the adjacent strand. A rubber intrusion path is provided to improve the rubber infiltration into the cord, and the cord circumscribed circle has an elliptical shape to suppress elongation under load, and fatigue is easily caused by repeated bending stress. It has a new configuration that does not destroy it. That is, the steel cord for reinforcing rubber products of the present invention is a steel cord having a 1 × n structure consisting of n (n = 3 to 6) strands having the same wire diameter, and at least one strand has the following formula. It has a satisfying substantially spiral shape and the cord circumscribing circle is a substantially elliptical shape with the same direction in the longitudinal direction, and the ratio D ₂ / D ₁ of the major diameter D ₁ and the minor diameter D ₂ is set to 0.6 to 0.9. Become.

P ₁ = 0.1P to 0.7P d ₁ = (d + 2 / 100mm) to (d + 2 / 10mm) However, P ₁ : Peculiar pitch P: Twisting pitch d ₁ : Peculiar outer diameter d: Strand diameter It suffices that there is at least one strand having a habit. This is because if there is a gap in one cross section even in one section, the rubber will penetrate from there and penetrate sufficiently into the cord.

In addition, in the above configuration, the substantially spiral habit is d ₁ =
(D + 2 / 100mm) to (d + 2 / 10mm) is limited to d
If it is smaller than +2/100 mm, even if a rubber with good fluidity is used, the rubber does not sufficiently penetrate into the inside of the cord during pressure vulcanization, and if it is larger than d + 2/100 mm, the twist stability is poor. This is because buckling is likely to occur and fatigue resistance is reduced.

The wire diameter d of the wire used for the steel cord of the present invention
Is preferably in the range of 0.2 to 0.4 mm.

In addition, the substantially spiral habit pitch P ₁
0.1 to 0.7 times means that if it is smaller than 0.1 times, the wire will be easily plastically deformed at the time of staking and the wire will be easily broken, and if it is more than 0.7 times, it will be due to the flow of rubber during rubber product molding. This is because the tensile force or the ironing force applied to the surface of the cord reduces the gap between the strands, resulting in insufficient rubber penetration.

Here, the eccentric outer diameter d ₁ is the apparent outer diameter of the strand that is squeezed in a substantially spiral shape as shown in FIGS. 1 and 2, and the slack pitch P ₁ is a substantially spiral shape. It is the pitch of the strands that have been hardened. In addition, the twist pitch P of the cord is preferably in the range of 6 to 16 mm.

By the way, the above-mentioned substantially spiral habit does not need to be exactly spiral, and even if it is simply wavy, since it shows the same effect as the spiral, it is assumed to include such a shape. .

Further, in the above configuration, the elliptical shape of the circumscribed circle of the cord is set to have a minor axis D ₂ / major axis D ₁ = 0.6 to 0.9. The bending work becomes large and the fatigue resistance decreases, and if it is made larger than 0.9 and becomes close to 1, the unidirectional flexibility is improved and the fatigue resistance cannot be improved. Or, it may cause kink or curl of the cord. More preferably 0.
It is in the range of 75 to 0.90.

An embodiment of the present invention will be described below with reference to the drawings.

[Example 1] As shown in Fig. 1 (a), one strand (2) having a substantially spiral habit and two strands (3) having straightness are twisted at a pitch P. = 8 mm, densely twisted together,
A cord having a substantially circular cross-section having a twisted structure of 1 × 3 × 0.38 is formed, and the cord is circumscribed by the processing means such as a roller die, a die having a substantially oval hole, or a straightening roller group so that the cord circumscribed circle becomes the cord length. A steel cord (1) having a substantially elliptical shape extending in the same direction was obtained.

The strand (2) having the substantially spiral habit has a habit pitch P ₁ = 3.2 mm, a habit outer diameter d ₁ = 0.45 mm, and a short diameter D ₂ / long diameter in the elliptical shape of the steel cord (1).
D ₁ was 0.85.

In the same figure, (b), (c) and (d) show one wire (2) having a substantially spiral habit and wire (3) having straightness.
1 x 4 x 0.25, 1 x 5 x 0.22, 1 x 6 x 0.20
Twist pitch configuration, twist pitch P, peculiar pitch P ₁ , peculiar outer diameter
By setting d ₁ and minor axis D ₂ / major axis D ₁ as shown in the table, a steel cord (1) whose circumscribing circle was substantially elliptical as in the above example was formed.

[Example 2] As shown in Fig. 2 (a), three strands (2) having a substantially spiral habit with a habit pitch P ₁ = 3.2 mm and a habit outer diameter d ₁ = 0.45 mm are twisted. By densely twisting at a pitch P = 8 mm, a cord having a substantially circular cross section having a 1 × 3 × 0.38 twist structure is formed, and the cord is circumscribed by the same processing means as in the first embodiment. A steel cord (1) having a substantially elliptical shape extending in the same direction was obtained.

Minor diameter D ₂ / in the elliptical shape of the steel cord (1)
The major axis D ₁ was 0.82.

In the same figure (b), (c) and (d), 1x4x0.25, 1x5x0.22, using a wire (2) having a substantially spiral habit in all the wires forming the cord, A 1 × 6 × 0.20 twist structure, with a twist pitch P, a peculiar pitch P ₁ , a peculiar outer diameter d ₁ and a minor diameter D ₂ / major diameter D ₁ as shown in the table, and the same circumscribed circle as in the above embodiment. Formed a steel cord (1) having a substantially elliptical shape.

In the second embodiment, since there is a gap between all the adjacent strands, the circumference of all the strands forming the cord is covered with rubber, and the local wear caused by the adjacent strands rubbing against each other, So-called fretting wear can be prevented, and fatigue resistance can be further improved.

By the way, in the above-mentioned Examples 1 and 2, one or all of the strands constituting the cord is provided with a substantially spiral habit. However, the present invention is not limited to this, and a plurality of strands are provided with a substantially spiral shape. Of course, it is possible to add a habit.

In addition, the substantially spiral habit to be applied to the wire (2) can be easily made by passing the wire between habit pins provided in the twisting machine and between small-diameter rollers arranged in a zigzag pattern thereafter. You can It is also easy to twist a single wire into a gear and twist the wire before putting it in the twisting machine. The peculiar pitch P _{1 and the} peculiar outer diameter d ₁ can be adjusted by adjusting the distance between pins and rollers in the former case, and by adjusting the shape of the gear and the number of twists of the single wire in the latter case. Can be set to a desired numerical value.

In each of the above-mentioned embodiments, the substantially spiral habit has pins 3 to 5 of the habit-setting cone provided before the twist gathering point.
This was done by running a wire between the books.

Next, comparative tests were conducted on the steel cords for reinforcing rubber products of the present invention and conventional examples and comparative examples shown in the table, and initial load elongation, rubber penetration rate, fatigue resistance and handling workability were evaluated. The results are shown in the attached table. In addition, all the strands constituting each cord have a tensile strength of approximately 280 kg / mm ² , and the surface thereof is brass-plated.

In this evaluation, the rubber penetration rate (%) was determined by embedding each cord under a tensile load of 5 kg in rubber, vulcanizing it and then removing the cord, disassembling the cord and observing a certain length. The ratio of the length with a trace in contact with the rubber material to the observed length was expressed as a percentage.

Fatigue resistance is tested by a three-point pulley bending fatigue tester using a composite sheet in which a plurality of steel cords are embedded in a rubber sheet, and the number of repetitions until the embedded steel cord is broken is obtained, For the cords with the same number of wires that make up each cord, the closed-strand structure was set as 100 and the index was displayed. That is, the values of the code Nos. 1, 7, 14, and 21 of the conventional example are set to 100, and the codes of the number of the same strands corresponding to them are displayed by the index.

The handling workability refers to the handling workability of the steel cord when manufacturing the steel cord, burying the rubber sheet, and molding a rubber product such as a tire. Compared with Nos. 1, 7, 14, and 21 of the conventional example, x was evaluated as very inferior, Δ as slightly inferior, and o as not having a difference.

Codes Nos. 1, 7, 14, and 21 are so-called closed-twisted cords in which all the strands are in contact with each other, and the infiltration of rubber into the cord is poor.

Cord Nos. 2, 8, 15, and 22 are all average form factors (cord diameter when twisted with a gap between each strand / cord diameter when each strand is tightly twisted x 100) 140%
This is an open twisted cord with excellent rubber penetration and fatigue resistance to the inside of the cord, but the initial load elongation is large and the workability is poor.

Code Nos. 3, 4, 9, 10, 16, 17, 23, and 24 are 1x3, 1x4, 1 using wires having a substantially spiral habit.
It is a cord with a twisted structure of × 5 and 1 × 6 and has a peculiar pitch P ₁
The outer diameter d ₁ and the minor diameter D ₂ / the major diameter D ₁ are different from those of the present invention, respectively, and are inferior in rubber penetration rate, fatigue resistance, handling workability, or a plurality of them. .

From the above comparison test, the steel cord of the present invention (cord
Only No. 5, 6, 11, 12, 13, 18, 19, 20, 25, 26, 27) can satisfy all of rubber penetration rate, fatigue resistance, initial load elongation and handling workability. It turned out to be a thing.

[Advantages of the Invention] Since the steel cord for reinforcing a rubber product of the present invention has the above-mentioned configuration, the gap formed between the strands serves as a passageway for the rubber to enter the cord, so that the rubber sufficiently penetrates. Therefore, it is possible to prevent a reduction in cord strength due to a separation phenomenon and rust.

Further, since the elongation under a very low load is small, workability is greatly improved. For example, when calendering a steel sheet on a reel and calendering on a rubber sheet, if the elongation at an extremely low load is large, there is a harmful effect such as puncture of the reel or wrinkling of the rubber sheet.
In the present invention, this is solved.

Furthermore, since the circumscribed circle of the cord is substantially elliptical and has the same direction in the cord longitudinal direction, it is excellent in flexibility in one direction. Therefore, by arranging the minor axis side in the tire thickness direction,
Even when stress is applied to the unevenness of the road when driving a car or when riding on pebbles, the fatigue resistance is not impaired, and the tire thickness can be reduced, making the tire lightweight. It has an extremely excellent effect that it can be realized and it leads to the energy saving effect of the automobile.

[Brief description of drawings]

1 (a), (b), (c), and (d) are schematic cross-sectional views of a steel cord for reinforcing a rubber product, which is an embodiment of the present invention, and FIGS. 2 (a), (b), ( (C) and (d) are schematic sectional views of different embodiments, FIG. 3 is a schematic sectional view of a conventional closed twisted steel cord, FIG. 4 is a schematic sectional view of a conventional sweet twisted steel cord, and FIG. 5 (a) ), (B) are schematic sectional views showing a state in which the strands in FIG. 4 are offset. (1), (4), (7) ... Steel cords (2), (3), (5), (6) ... strand E ... cavity, C ... gap

Claims (1)

[Scope of utility model registration request] 1. A steel cord having a 1 × n structure consisting of n wires (n = 3 to 6) having the same wire diameter, and at least one wire having a substantially spiral habit satisfying the following formula. a and code circumscribed circle is substantially elliptical shape of the same direction in the longitudinal direction, a rubber product reinforced the ratio D ₂ / D ₁ and the diameter D ₁ and the minor axis D ₂ is characterized in that 0.6 to 0.9 For steel cord. P ₁ = 0.1P to 0.7P d ₁ = (d + 2 / 100mm) to (d + 2 / 10mm) However, P ₁ : Peculiar pitch P: Twist pitch d ₁ : Peculiar outer diameter d: Strand diameter