JP2000239984A - Steel cord for reinforcing tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a steel cord for reinforcing a tire having excellent rubber permeation, capable of controlling break, buckling, etc., by twisting a core wire and plural side wires in the same direction at a time and providing the core wire with an approximately spiral habit. SOLUTION: One of three wires having 0.15-0.40 mm wire diameter d is used as a core wire 1 and the residual two wires are used as side wires 2. The wires are twisted at 5-20 mm twisting pitch P in the same direction at a time to form a cord 3. The core wire 1 has an approximately spiral habit composed of a habit pitch P1 mm and a habit outer diameter d1 mm satisfying the relations P1=0.1 P to 0.7 and d1=(d+2/100) to (d+2/10) and a habit outer diameter d1 mm. In the cross section of the cord, a state in which the three core wires are brought into contact with one another or in an adjacent state and a state in which the three wires are arranged in a line with placing the core wire 1 at the center are repeated at approximately 1/2 pitch in the longer direction in the same orientation to give the objective steel cord for reinforcing a tire.

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 automobile tires, and more particularly to a steel cord in which three strands are twisted.

[0002]

2. Description of the Related Art In general, steel cords of this kind are used as reinforcing materials for automobile tires by being covered with a rubber material in a state where many steel cords are aligned in parallel. And
The conditions required for steel cord include not only excellent mechanical strength and flexibility, but also good chemical and physical adhesion to rubber materials, and steel cord. -Good penetration of the rubber into the inside of the metal. That is, in order for the steel cord to sufficiently fulfill the role of a tire reinforcing material, it is necessary to form a complete composite with a rubber material.

Conventionally, in this type of steel code, for example, in addition to a 1 × 3 structure (FIG. 5), a 2 + 1 structure,
There is a pun-type 1 × 3 structure (FIG. 6), and a recently proposed parallel three-wire structure (FIG. 7) in which three strands with a wavy pattern are arranged without twisting. .

As shown in FIG. 5, the conventional 1 × 3 steel cord has a cross-sectional structure of a close-twisted structure, and the individual wires 4 are completely adhered to each other so that there is no gap. , A closed cavity S exists inside the steel code 5. Therefore, when a composite sheet (belt layer) is formed by sandwiching this steel code between two rubber sheets, the rubber material does not penetrate into the hollow portion S, and complete with the rubber material. Complex cannot be formed.

Therefore, when a rubber sheet in which the steel code is embedded is used for a tire, if the rubber coating is partially broken by a foreign substance such as a nail, moisture that has entered from the outside will cause the moisture to enter the cavity S. And rust is generated over the entire surface of the steel code. In this case, the adhesive force between the rubber and the steel cord is weakened, and the two are separated from each other, so that the effect of the steel cord as a reinforcing material is extremely weakened. In the worst case, it leads to tire burst.

In order to solve this problem, as shown in FIG. 6, a steel coil having an open structure is applied to a strand.
Has been proposed. As shown in FIG. 6, a steel cord 7 having a 1.times.3 open structure in which the wire 6 is excessively stiffened.
Since the wires 6 are hardly in contact with each other, the penetration of the rubber into the steel cord is good, and the generation of rust is greatly improved. However, due to its structure, this cord has a large cord diameter, is easily stretched under a low load, and reduces the tension applied to the cord at the time of rubberized and rolled the cord to maintain a gap between wires. It is necessary to rubberize
The tension control is very difficult and there are many manufacturing problems.

Further, the steel cord having the 1 × 3 structure and the 1 × 3 open structure does not have anisotropy in bending rigidity due to its circular cross section, and requires a large bending deflection in the tire. In the part to be bent (in the tire radial direction, that is, in the vertical direction of the belt layer), the bending rigidity of the steel cord is unnecessarily large, while the part in which the bending deflection is required to be small (in the tire rotation direction and In the direction perpendicular to the belt, ie, in the width direction of the belt layer), the bending rigidity of the steel code tends to be slightly too low. Therefore, there is a problem that the steering stability is inferior and the ride comfort is impaired.

Recently, a steel code such as a three-parallel structure shown in FIG. 7 has been proposed. For example, if the steel cords are arranged in the belt layer such that their strands are arranged in the width direction of the belt layer, the bending rigidity in the longitudinal direction of the belt layer becomes small. Therefore, the steering stability is good, and at the same time, the vertical acceleration at the time of traveling is absorbed, and the riding comfort becomes soft without picking up the seam of the road surface at a high speed. However, in this steel cord, since the three strands are not twisted, it is necessary to fix them with a wrapping wire so that they do not come apart. In addition, the bending rigidity in the width direction of the belt layer tends to be too strong, and in a direction other than the longitudinal direction of the belt layer, torsion or buckling easily occurs in bending.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to secure rubber penetration into steel cord to prevent separation due to rust and to improve steering stability and ride comfort. Another object of the present invention is to provide a steel cord which does not cause the steel cord to break or buckle in a belt layer or the like.

[0010]

In order to achieve the above object, a steel cord for reinforcing a tire according to the present invention has a diameter of 0.15.
A steel core having three strands each having a wire diameter of 0.5 mm to 0.40 mm, one being a core strand and the other strand being a side strand, and twisted at a time at a twist pitch P in the same direction. (1) (2) where the core strand is different from the twisted habit
Has a habit of pitch P ₁ Tokuse substantially spiral outer diameter d ₁ habit to satisfy, the steel - Turkey - cross section of the soil, the state where the wires between the three is in contact with or in proximity to each other A tire reinforcing steel cord characterized in that a state in which the core wires are arranged substantially in a line is repeated in substantially the same direction in the longitudinal direction at an interval of about 1/2 pitch. P ₁ = 0.1 P to 0.7 P (1) d ₁ = (d + 2/100) to (d + 2/10) (2) d: wire diameter (mm) (core wire diameter and side wire) If the wire diameter is different side wire of wire diameter) P _1: habit pitch (mm) d _1: habit outer diameter of the core wire (mm) Note, steel - Turkey - twisting pitch of de by reason described later 5 About 20 mm is preferable. Further, the diameters of the core strand and the side strands may all be the same, but the diameter of the core strand may be slightly increased. At this time, the wire diameter d uses the wire diameter of the side strand.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view showing the appearance of the steel code of the present invention. And FIGS. 2 (a) to 2 (i)
FIG. 2 is a schematic view showing an end face of a cross section of a portion (a) to (i) in FIG. 1. This steel code 3 is composed of one core element wire 1 having a substantially spiral shape and a core wire 2 having the same wire diameter.
And two side strands 2. In the steel cord of the present invention, one of the three strands is used as a core strand, and the core strand is given a small, substantially spiral shape different from the twisted one. A gap is generated, and rubber penetration is improved. The steel cord buried in the rubber sheet has a cross section substantially in the same direction in the longitudinal direction, and three strands are arranged at intervals of 1/2 pitch centering on the core strand, for example, in the belt layer in the width direction. , The bending rigidity in the tire radial direction, that is, the longitudinal direction of the belt layer, is greatly reduced as compared with the conventional tire. Therefore, the driving stability of the vehicle is good, and at the same time, the vertical acceleration during traveling is absorbed, and the riding comfort is soft without picking up seams on the road surface at high speed.

Further, since the belt layer has high rigidity in the width direction and high bending rigidity in the longitudinal direction of the belt, the belt has excellent flexibility in vertical bending compression fatigue during running. Code breakage is unlikely. Moreover, the belt modulus at the end of the belt is suppressed, and it approaches the rubber, so to speak, so that the end of the belt can easily follow the repeated deformation caused by the rotation of the tire, and the separation of the end of the belt hardly occurs. Further, unlike the above-described parallel three-piece structure, the bending rigidity in directions other than the belt longitudinal direction is not too high, buckling or twisting does not occur, and cornering performance can be improved. Furthermore, the state in which the three strands are in contact with or close to each other and the state in which they are arranged substantially in a line around the core strand are alternately repeated in the longitudinal direction, so that the cord moves back and forth in the rubber. It is very stable without any risk of bleeding.

Further, in the steel cord of the present invention, in the belt layer, the direction in which the three strands are arranged substantially in a line around the core strand is aligned in the width direction of the belt. The rubber sheet can be made thin. And the number of inserted steel codes can be reduced. As a result, the weight of the tire has been reduced, and it has become possible to reduce the cost of the tire and to improve the fuel efficiency of the automobile. Further, in terms of twist stability, the twist is stable as compared with steel cords as shown in FIGS. 6 and 7, and the shape is almost the same even after being embedded in a rubber sheet. It is also excellent in handling work.

The twist pitch of the steel cord is 5 mm to 2 mm.
0 mm is preferred. Because if it is less than 5 mm,
This is because the bending amount is extremely increased, so that disconnection is liable to occur, and the number of twists per length of the steel cord is increased, thereby lowering productivity. Furthermore, in the present invention, since the habit pitch of the core strand is even smaller than the twist pitch, a twist pitch of less than 5 mm is not appropriate. On the other hand, if the twist pitch of the steel cord exceeds 20 mm, the flexibility of the steel cord is lost, so that the fatigue value is lowered, the twist becomes unstable, and flare is liable to occur. Not.

The wire diameter of the strand is 0.15 mm to 0.40 mm
The reason is that if it is too thin, sufficient strength cannot be obtained, and if it is too thick, the steel cord diameter becomes large. On the other hand, if the strand is made thicker, the steel cord loses its flexibility and the fatigue value becomes lower. This tendency is more remarkable in the present invention in which a strand having a small habit exists, and when the strand diameter exceeds 0.4 mm, it becomes a practical obstacle.

The twist pitch of this steel cord is Pmm
When a, to that the habit pitch P ₁ of the core wire having a habit and 0.1P~0.7P, when P ₁ is less than 0.1P, strands undergo extreme plastic deformation, breakage When the concentration exceeds 0.7P, the effect as a core strand is not achieved, and the tensile force due to the flow of rubber at the time of rubber sheet molding or a load is applied to the cord. This is because the gap between the wires is reduced by the squeezing force, and a sufficient gap for rubber infiltration is not generated between the wires. On the other hand, if it exceeds 0.7P, the steel code structure of the present invention will not be stable, and a part where three strands are substantially aligned will not appear.

When the wire diameter of the steel cord is dmm, the halo outer diameter d ₁ of the halo core wire is d ₁ =
The range that satisfies the expressions (d + 2/100) to (d + 2/10) is such that in this expression, d ₁ is (d + 2/10)
0) It is practically difficult to perform the processing smaller than that described above, and it is more preferable to perform sufficient rubber penetration between the strands. (D
If it exceeds (+2/10), the effect of thinning the rubber sheet is reduced, and the twist becomes unstable. This range is most suitable in terms of production and operation and effect.

The steel cord according to the present invention is characterized in that a single wire is given a preset habit to form a core wire, a side wire is twisted around the core wire, and a roller having a flat surface is formed. −
It can be manufactured by passing through a gap and applying a considerably strong compression process. Conventionally, in such a method, it was thought that the twist of the steel cord was broken and the cord was defective. It was also found that the production could be easily performed by applying the feeding tension and applying a strong compression process between the arranged rollers.

Although the steel cord of the present invention can be manufactured by a tuber type twisting machine, it is more efficient and practical to manufacture it by a buncher type twisting machine. When a buncher-type twisting machine is used, it is necessary to take into account that the twisting of the strand is different from the twisting of the steel cord in advance because of the twist.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be specifically described below in comparison with a conventional example.

In order to evaluate the characteristics of the steel cord of the present invention, the wire diameter d, the twist pitch P, the habit pitch P ₁ of the core wire and the habit outer diameter d ₁ are set within the scope of the present invention. The changed steel codes are referred to as Examples 1 to 3, and a steel code having a cross-sectional shape as shown in FIG.
A steel cord having a cross-sectional shape as shown in FIG. 6 is referred to as Conventional Example 2, and a steel code having an external shape as shown in FIG. The rubber was evaluated for rubber penetration rate, fatigue resistance, torsional and buckling resistance, rigidity ratio, ride comfort and handling workability. The results shown in Table 1 below were obtained. Test conditions and evaluation methods for each item shown in Table 1 are as follows.

Rubber penetration rate: Each steel cord was embedded in rubber while applying a tensile load of 3 kg, and after vulcanization, the steel cord was taken out of the rubber and the steel cord was removed.
The cord was disassembled to observe a certain length of the strand, and the ratio of the observed length to the length of the trace in contact with the rubber was expressed in%. In the table, the larger the value, the better the rubber penetration rate.

Fatigue resistance: A three-point pulley using a composite sheet in which a plurality of steel cords are embedded in a rubber sheet.
The number of repetitions until the embedded steel cord breaks through fretting wear, buckling, etc. is determined by testing using a bending fatigue tester, and the twisted steel of the conventional example 1 is obtained.
The index was expressed as an index with the value of the record being 100. In the table, the larger the value, the better the fatigue resistance.

Twist resistance and buckling: Steel cords that broke out of 100 steel cords after repeated bending fatigue tests for a certain period of time were examined, and the cause was twisting of the strands. And the number of strands resulting from buckling were displayed.

Stiffness ratio: As shown in FIG. 3 (a), "5 steel cords having a 100% modulus of 35 kg /
The length of the steel cord cross section is horizontal with respect to the rubber sheet 11 of cm 2 (in the steel code of the present invention, the direction in which the three strands are arranged substantially in a line) As shown in FIG. 3 (b), a test piece 12 embedded in a row (to be horizontal) and "five steel cords were -In order for the major axis of the cross section to be vertical (in the steel code of the present invention,
The test piece 13 is manufactured by embedding in parallel such that the direction in which three strands are arranged substantially in a line is vertical), and as shown in FIG.
Put on a three-point bending tester with p = 20 mm, and “load G when holding down test piece 12 by 5 mm” /
The "weight G when the test piece 13 was pressed down by 5 mm" was defined as the rigidity ratio.

That is, the ratio of "lateral bending rigidity of steel code" / longitudinal bending rigidity of steel code was defined as the rigidity ratio. In the table, a smaller value indicates a difference in bending stiffness. The steel coils of Conventional Examples 1 and 2 were used.
The rigidity ratio was set to 1 because there was no major axis or minor axis. The thickness of the test piece 12 or 13 is 4 m.
m, the width is 15 mm, and the length is 100 mm.

Ride comfort evaluation: The tires in which these steel cords were embedded were outsourced as trials, and the sensitivity of asphalt-paved roads by 10 panelists was evaluated by a 10-point scale, and the average was calculated. Handling workability: At the time of steel code manufacture and tire manufacture, those with good workability were marked with “〇”, those with poor workability were marked with “x”, and those with intermediate workability were marked with “△”.

[0028]

[Table 1]

The following points are clear from Table 1. Conventional example 1 is a steel cord shown in FIG. 5 in which three strands are twisted into a close, and the workability is good, but the rubber penetration is inferior, the rigidity ratio is the same as the conventional one, and the twisting is performed.・ There are many bucklings.

Conventional Example 2 is a steel cord shown in FIG. 6 in which three strands are twisted into an open wire, and has excellent rubber penetration, but inferior workability and rigidity ratio. As before, there are many twists and buckles. In addition, since the cord diameter is large, there have been problems such as a thick rubber sheet.

Conventional Example 3 is a steel cord having a structure shown in FIG. 7 in which three strands are arranged in parallel and one wrapping wire is wound therearound, and has extremely excellent fatigue resistance. However, the rigidity ratio is too low and the ride quality is inferior,
The result was a little inferior in handling workability.

The steel cords of Examples 1 to 3 do not have the above-mentioned disadvantages, and have rubber penetration, fatigue resistance, riding comfort,
It was confirmed that it was excellent in all aspects such as handling workability.

[0033]

The steel cord for reinforcing a tire according to the present invention is constituted as described above and has the following effects. Steel code is applied over almost the entire area in the longitudinal direction.
There is no hermetically closed cavity inside the steel cord, so that the rubber can well penetrate into the steel cord. Since the thickness of the rubber sheet when it is embedded in rubber to form a sheet can be reduced, the weight of the tire can be reduced, so that the cost of the tire can be reduced and the fuel efficiency of the automobile can be improved. Since the rigidity in the tire rotation direction can be reduced, the riding comfort can be improved. On the other hand, the rigidity in the direction perpendicular to the tire rotation direction (the width direction of the belt layer) can be increased, so that cornering performance can be improved. it can. Since it is not an unstable structure such as an open structure or a parallel structure steel code, the workability is excellent. Since the rigidity ratio in the horizontal and vertical directions is appropriate, breakage due to twisting and buckling of the wire against bending fatigue is significantly reduced as compared with the conventional steel code, and the steel code
The life of tires and thus the life of tires has been greatly extended.

[Brief description of the drawings]

FIG. 1 is a schematic external view of a 1 × 3 structure showing an example of a tire reinforcing steel cord of the present invention.

2 shows an example of a steel cord for reinforcing a tire according to the present invention, wherein (a) to (i) are schematic views showing end faces of cross sections of (a) to (i) in FIG. .

FIG. 3 shows test pieces used in a three-point bending test;
(A) is a schematic diagram of a test piece for measuring bending stiffness in which a state in which three strands are substantially in a row is embedded horizontally in a row,
(B) is a schematic external view of a test piece for measuring bending stiffness in which a state in which three strands are substantially aligned is vertically embedded.

FIG. 4 is an explanatory view showing a three-point bending test method.

FIG. 5 is a cross-sectional view of a conventional steel cord having a 1 × 3 structure of a close twist.

FIG. 6 is a sectional view of a conventional open twisted steel cord having a 1 × 3 structure.

FIG. 7 is a schematic external view of a steel cord having a structure in which one wrapping wire is wound around three parallel wires.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Core wire 2 ... Side wire 3, 5, 7, 10 ... Steel code 4, 6, 8 ... Wire 9 ... Wrapping wire 11 ... Rubber - DOO 12 ... test pieces - scan d ... wire diameter d ₁ ... habit outer diameter W ... present invention steel core wire - Turkey - the three strands a row of de Long diameter when arranged T: diameter when three strands of the steel cord of the present invention are twisted S: hollow part

Claims (1)

[Claims] 1. Three strands each having a wire diameter of 0.15 mm to 0.40 mm, one being a core strand and the other strand being a side strand, are twisted in the same direction at a twist pitch P at a time. twisted steel - Turkey - a de, have a habit of substantially spiral pitch P ₁ Tokuse outer diameter d ₁ habit to satisfy the following formula different from the habit of the core wire is twisted (1) (2) The cross section of the steel cord shows the state in which the three wires are in contact with or close to each other and the state in which the three wires are arranged substantially in a line with the core wire as the center. tire reinforcing steel, characterized by comprising repeating substantially the same orientation in the longitudinal direction - Turkey - de _{P 1 = 0.1P~0.7P ·· (1)} d 1 = (d + 2/100) ~ (d + 2 / 10) ·· (2) d: wire diameter (mm) (on the side strands if the core wire diameter and the side wire diameter different wire diameter) P ₁ Habit Pitch (mm) d _1: Core wire straightening outer diameter (mm)