JP2007177362A - Steel cord for reinforcing rubber product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily and precisely provide a single-ply twisted steel cord for reinforcing a rubber product, having sufficient penetrability of rubber and excellent fatigue resistance. <P>SOLUTION: The steel cord 10 has a single-ply twist of 1×n (n=3-6) and comprises normal filaments (wire 12) having no kink except the spiral kink for cord twist, and spiral filaments having small spiral kinks separated from the spiral kinks for the cord twist. The spiral filament is regulated so that when the spiral cord after untwisting is arranged horizontally, the maximum value of the angle formed by the tangential line t2 of a locus projected on the horizontal plane on the projected plane, and the base line r2 of the spiral kink for the cord twist may be 1.2-2.0 times as much as the twisting angle of the cord. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a steel cord used for reinforcing rubber products such as automobile tires and conveyor belts, and more particularly, to a steel cord having both sufficient rubber penetration and excellent fatigue resistance.

  As a steel cord used for reinforcing rubber products such as automobile tires and conveyor belts, for example, a closed twist structure (so-called closed type) in which 3 to 6 strands (steel filaments) are twisted in a single layer densely Things are often used in the past. This steel cord is made of a plurality of wires arranged in parallel, covered with a rubber material, molded into a composite sheet, and then embedded in a rubber product. It is called a 1 × 3 structure, and it is called a 1 × 4, 1 × 5, or 1 × 6 structure depending on the number of strands.

  However, such a closed type steel cord has a continuous gap in the longitudinal direction inside the cord, and when the composite cord is formed by covering the steel cord with a rubber material, the gap inside the cord is made of a rubber material. It remains as a void without entering. This void is reduced by the rubber surrounding the cord surface entering the inside of the cord at the time of rubber vulcanization pressurization in the tire molding process, etc., but it is not completely filled with the rubber, and the cord center is in the longitudinal direction. It remains as a straw-like hollow portion extending in the direction. Moisture generated as a result of condensation of the gas generated from the rubber material and moisture infiltrated from an external wound, etc., penetrated into the hollow portion, and as a result, corrosion progressed from the inside of the cord, and the steel As the strength of the cord decreases, the adhesiveness between the steel cord and the rubber material decreases, causing a so-called separation phenomenon in which the steel cord and the rubber material peel off, which is a factor that significantly shortens the product life. It was.

  In addition, a steel cord with an untwisted open twist structure (so-called open type) that is twisted into a single layer while providing a gap between the strands so that the rubber material penetrates into the cord is also conceivable and has been used conventionally. Yes. However, steel cords with an open twist structure require a large gap (at least 0.01 mm) between the strands in order to allow the rubber material to sufficiently penetrate into the cord. If the gap is large, the movement of the strands Since the free space that can be made becomes larger, the strands of the wire are displaced, the twist becomes uneven in the longitudinal direction, and it becomes easy to buckle when repeated bending stress is applied. Since the elongation is large, not only the handling workability is bad, but also the gap is reduced due to the tension applied at the time of forming the composite sheet, and the rubber material may not sufficiently enter the cord.

Therefore, by twisting together a strand having a small spiral shape or a wavy strand apart from a spiral strand for twisting a cord and a straight strand having no other than the spiral strand for twisting the cord. A single-layer twisted steel cord has been developed (see, for example, Patent Documents 1 and 2).
Japanese Examined Patent Publication No. 7-68673 Japanese Patent No. 3179915

  Single-layer stranded steel cord is a straight wire that has a small spiral or wavy comb apart from the spiral twist for twisting the cord as described above, and a straight wire that does not have any bracing except for the spiral twist for twisting the cord. By forming a twisted structure with a twisted strand, even if the twist itself is dense, a rubber material between the strands in a twisted state due to a small spiral or corrugation of some strands The steel cord is restrained by the resistance of the straight wire against the tension applied when forming the composite sheet with the rubber material, and the small spiral or wavy comb disappears. It is possible to hold the gap between the wires so that the rubber material sufficiently penetrates into the cord, and the twist itself is dense and stretched at an extremely low load. The suppressed, while improving the handling properties, to stabilize the twist code longitudinally, it considered it is possible to easily and excellent steel cord fatigue resistance that does not cause buckling even with repeated bending stress.

  However, all single-ply stranded steel cords made by twisting strands with small spirals or undulations and straight strands both provide sufficient rubber penetration and excellent fatigue resistance. It does not mean that it will be something that combines. In order to achieve both sufficient rubber penetration and excellent fatigue resistance, the number of wires, the pitch of the wires, the height of the wires should be set for each different number of wires and wire diameter of the cord. It is necessary to evaluate the rubber penetration from both the rubber penetration and fatigue resistance, and to identify the optimum setting, which is not easy.

  The present invention is intended to solve these problems, and it is an object of the present invention to easily and reliably obtain a steel cord for reinforcing a rubber product having a single-layer twist having sufficient rubber penetration and excellent fatigue resistance. And

  The steel cord for reinforcing rubber products of the present invention is a single layer twist formed by twisting n pieces (n = 3 to 6) of strands, and at least one strand is separate from a spiral knot for twisting the cord. A steel cord having a small spiral or wavy habit, and at least one of the strands having a spiral or wavy habit is arranged on a horizontal plane by twisting the steel cord and then horizontally laying the wire The maximum value of the angle formed between the tangent line of the wire trajectory and the reference line of the spiral habit for twisting the cord is 1.2 to 2.0 times the twisting angle of the cord. .

  A small spiral-shaped beak is a three-dimensional spiral beak, and a wavy-shaped beak is a two-dimensional shape that is a projection of a helix, both of which are smaller than the spiral for cord twisting. And it has the same effect. Further, the direction of the spiral habit may be the same as the cord twisting direction, or may be the opposite direction.

  This steel cord is formed by twisting at least one of the n wires (n = 3 to 6) having a small spiral shape or a wavy shape apart from the spiral feature for twisting the cord. There is a gap for the rubber material to enter between the strands in the combined state, and at least one of the strands having a small spiral or corrugated wrinkle is used to level the strands after twisting the steel cord. When the maximum value of the angle formed between the tangent of the element wire on the projection plane when projected and projected onto the horizontal plane and the reference line of the spiral twist for the cord twist is 1.2 to 2.0 times the cord twist angle For example, in forming a composite sheet with a rubber material, the decrease in drag against the load when tension is applied is reduced, and the elongation of the steel cord is suppressed, so that a small spiral or wavy habit is formed. The gap between the wires enough to allow the rubber material to penetrate into the cord can be held between the strands, the twisted shape is stabilized in the longitudinal direction of the cord, and it is easily buckled by repeated bending stress It can be made excellent in fatigue resistance.

  For strands with small spiral or wavy strands separate from spiral strands for twisting cords, strands after untwisting steel cords are placed horizontally and projected on the horizontal plane when projected onto a horizontal plane. If the maximum value of the angle between the tangent of the wire and the reference line of the spiral hose for twisting the cord is smaller than 1.2 times the twisting angle of the cord, a gap (at least 0. 01 mm or more) cannot be obtained. In addition, the maximum value of the angle between the tangent of the strand on the projection surface and the reference line of the spiral hook for twisting the cord when the strand after twisting the steel cord is placed horizontally and projected onto the horizontal plane is the cord When the twist angle is larger than 2.0 times, the resistance against the load of the wire becomes small, the elongation of the entire cord when the steel cord is loaded with tension is increased, and the rubber material sufficiently penetrates into the cord. As a result, it becomes impossible to ensure a sufficient gap, and the twisted shape becomes non-uniform so that the fatigue resistance is lowered.

  As described above, according to the present invention, it is possible to easily and reliably obtain a steel cord for reinforcing a single-layered rubber product having sufficient rubber penetration and excellent fatigue resistance.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a cross-sectional view (a) of a steel cord as an example of an embodiment of the present invention and a cross-sectional view (b) of another example of the steel cord, and FIG. 2 is a side view of the steel cord shown in FIG. Fig. 3 shows the trajectory of the steel cord shown in Fig. 1 (a), which is horizontally arranged after untwisting the strands (normal filaments) that do not have any bracing other than the spiral twist for twisting the cord, and is projected on the horizontal plane. (A) which shows, and the figure which shows the locus | trajectory which is arrange | positioned horizontally after twisting the strand (spiral filament) which has a small spiral-like crack different from the spiral twist for a cord twist, and was projected on the horizontal surface ( b).

  As shown in FIG. 1A, the steel cord of this embodiment is a steel cord 10 having a 1 × 3 structure in which, for example, three strands (filaments) are twisted together, and one strand 11 Is a strand (spiral filament) that has a small spiral-like strand separate from the spiral strand for twisting the cord, and the other two strands 12 are braided except for the spiral strand for twisting the cord. It is formed by twisting them as a straight wire (normal filament) that does not have. Here, the small spiral beak is a three-dimensional spiral beak. The direction of the spiral habit may be the same as the cord twisting direction, or may be the opposite direction.

  As shown in FIG. 1B, this steel cord is a steel cord having a 1 × 3 structure formed by twisting, for example, three strands (core layer filaments). The wire 21 is a strand having a wavy comb different from the spiral twist for twisting the cord, and the other two strands 22 are straightness having no clasp other than the spiral twist for twisting the cord. The steel cord 20 formed by twisting them together as a certain strand (normal filament) may be used. Here, the wavy habit is a two-dimensional wrinkle of a shape projected from a spiral.

Wire having a habit of spiral or wavy 11 and 21, the same wire diameter and the other wire 12, 22 having the straightness, as illustrated in FIG. 2, smaller than the pitch P habit pitch P ₁ is twisted , P ₁ = 0.1 P to 0.7 P, and the apparent outer diameter d ₁ is spiral so that d ₁ = (d + 2/100 mm) to (d + 2/10 mm) where d is the strand diameter. Or it is wavy. Here, the comb pitch P ₁ is a spiral pitch (see FIG. 2) or a wave pitch of the bare strands, and the apparent outer diameter d ₁ is a strand stranded in a spiral shape. 11 is the diameter of the circumscribed circle A1 (see FIG. 1A) viewed from the longitudinal direction, or the wave height of the element wire 21 that has been waved (the circumscribed projection ellipse A2 viewed from the longitudinal direction (see FIG. 1) (Refer to (b))).

  Further, in the case of the steel cord 10 in which one strand is a strand 11 having a small spiral-like shape different from the spiral-like shape for twisting the cord, there is a caulking except for the spiral-like shape for twisting the cord. The wire 12 (normal filament) that has not been twisted is horizontally arranged and projected on the horizontal plane as shown in FIG. 3A, for example, as shown in FIG. The angle α1 formed with the reference line r1 in any case is the same angle as or less than the cord twist angle, but has a small spiral-like strand separate from the spiral twist for cord twist For No. 11 (spiral filament), the trajectory projected horizontally on the surface after untwisting is shown in FIG. The angle α2 formed between the tangent t2 on the projection surface and the reference line r2 of the spiral twist for twisting the cord is local but larger than the cord twist angle, and the maximum value of the angle α2 is the cord twist angle. To be 1.2 to 2.0 times greater.

  The same applies to the case of the steel cord 20 in which one strand is a strand 21 having a small wavy fold different from the spiral fold for twisting the cord, which is different from the spiral fold for twisting the cord. The trajectory of the strand 21 having a small wavy habit, which is horizontally arranged after being twisted and projected onto the horizontal plane is determined by the angle α2 formed by the tangent t2 on the projection plane and the spiral warp reference line r2 for twisting the cord. Although it is ground, it is larger than the cord twist angle, and the maximum value of the angle α2 is set to 1.2 to 2.0 times the cord twist angle.

  These steel cords 10 and 20 are, for example, covered with unvulcanized rubber and molded into a composite sheet with a rubber material, and embedded in the rubber of the tire body at the time of tire molding as a tire reinforcing material. In this case, when the unvulcanized rubber is coated around the steel cords 10 and 20, the unvulcanized rubber is removed from the gaps C1 and C2 between the bare strands 11 and 21 and the straight strands 12 and 22. It penetrates into the inside of the cord, is vulcanized at the time of molding the tire, and penetrates into the hollow portions B1, B2 at the center of the cord. At that time, the steel cords 10 and 20 are trajectories in which the strands 11 and 21 having a small spiral shape or a wavy shape different from the spiral twist for twisting the cord are horizontally arranged after being twisted and projected on the horizontal plane. The maximum value of the angle α2 formed between the tangent t2 on the projection plane and the reference line r2 of the spiral twist for twisting the cord is 1.2 to 2.0 times the twist angle of the cord. Therefore, the decrease in the drag force against the load when tension is applied in the composite sheet molding with the rubber material is small, the elongation of the steel cords 10 and 20 is suppressed, and the rubber material only enters the inside of the cord sufficiently. Thus, the twisted shape is stabilized, and the fatigue resistance is not easily caused by repeated bending stress.

  A horizontal plane in which the strands 11 and 21 of the strands 11 and 21 having a small spiral shape or a wavy strand apart from the spiral strand for twisting the cords are horizontally arranged after the steel cords 10 and 20 are untwisted. If the maximum value of the angle α2 formed between the tangent t2 of the strands 11 and 21 on the projection surface and the reference line r2 for spiral twisting for cord twist is smaller than 1.2 times the cord twist angle, A gap (at least 0.01 mm or more) sufficient for the material to enter the central portion of the cord cannot be obtained. Further, when the strands 11 and 21 after twisting the steel cords 10 and 20 are horizontally arranged and projected onto the horizontal plane, the tangent t2 of the strands 11 and 21 on the projection plane and the spiral habit standard for twisting the cords When the maximum value of the angle α2 formed with the wire r2 is larger than 2.0 times the cord twist angle, the resistance against the load of the strands 11 and 21 becomes small, and when the steel cords 10 and 20 are loaded with tension. As a result, the elongation of the entire cord becomes large, and it becomes impossible to secure a gap enough for the rubber material to enter the inside of the cord, and the twisted shape becomes non-uniform, resulting in a decrease in fatigue resistance.

  In the illustrated example, each of the two strands 12 and 22 of the three strands constituting the steel cords 10 and 20 is a straight strand, and each one strand 11 , 21 is a strand having a small spiral or wavy comb, and the trajectory projected on the horizontal plane after untwisting each of the single strands 11 and 21 having the small spiral or wavy comb and projected onto the horizontal plane is The maximum value of the angle α2 of the angle α2 formed between the tangent t2 on the projection surface and the reference line r2 of the spiral twist for cord twist is 1.2 to 2.0 times the cord twist angle. The strands 11 and 21 having small spiral or corrugated bead may be at least one of the strands constituting the steel cords 10 and 20, and may be plural (or all). In addition, when there are a plurality of strands 11 and 21 having spiral or wavy habits, the trajectory arranged horizontally after being twisted and projected on the horizontal plane is the tangent t2 on the projection surface and the spiral habit for twisting the cord. There may be at least one strand that allows the maximum value of the angle α2 of the angle α2 formed with the reference line r2 to be 1.2 to 2.0 times the cord twist angle, and a plurality of strands may be used (all It may be)

  Moreover, although the example of illustration is a case of 1x3 structure, this invention is applicable similarly to the steel cord of 1x4, 1x5, and 1x6 structure.

  Table 1 shows test results of prototypes of steel cords having various configurations in which a plurality of strands having a surface plated with brass are twisted together. One of the cords of the present invention (Example) has a 1 × 3 structure, a strand diameter of 0.30 mm, the number of strands having small wavy combs, a cord pitch (twist pitch) of 16 mm, a twist angle ( (Cord twist angle) is 3.875 degrees, the maximum corrugation angle (maximum angle between the tangent line on the projected plane of the trajectory placed horizontally after twisting and projected onto the horizontal plane and the reference line of the spiral twist for cord twist Value) is 7.1 degrees, and the ratio of the maximum corrugation angle to the twist angle is 1.832. Another cord of the present invention (example) is a 1 × 4 structure, the wire diameter is 0 .30mm, 2 wires with small wavy combs, cord pitch 16mm, twist angle 4.761 degrees, corrugation maximum angle 6.25 degrees, ratio of corrugation maximum angle and twist angle Is a steel cord of 1.313. One of the comparative examples has a 1 × 3 structure, a wire diameter of 0.30 mm, the number of strands having a small wavy comb, one cord, a cord pitch of 16 mm, a twist angle of 3.875 degrees, and corrugation Steel cord with a maximum angle of 4.5 degrees and a ratio of the maximum corrugation angle to the twist angle of 1.161. Another comparative example is a 1 × 3 structure, wire diameter 0.30 mm, small corrugation The number of strands having a splinter is one, the cord pitch is 16 mm, the twist angle is 3.875 degrees, the maximum corrugation angle is 7.9 degrees, and the ratio of the maximum corrugation angle to the twist angle is 2.039. Steel cord. The conventional example is a steel cord having a 1 × 3 structure, a closed type with a strand diameter of 0.30 mm, a cord pitch of 16 mm, and a twist angle of 3.875 degrees.

  In this test, each steel cord was subjected to a tensile load of 49N, embedded in rubber and vulcanized, then the steel cord was removed from the rubber, the strand was peeled off, and the entire circumference of the strand was observed. The area ratio in contact with the rubber material was measured and displayed as “rubber penetration (%)”.

  Further, the elongation was measured by applying a tensile load of 49 N to each steel cord, and displayed as “low load elongation”.

  In addition, multiple steel cords of the same specification are embedded in a rubber sheet, three-point pulley bending fatigue is repeated a certain number of times with this sheet, then the cord is taken out from the rubber sheet and the breaking strength is measured. The results were expressed as an index as “fatigue resistance”. The smaller the index, the lower the fatigue resistance.

  In addition, the complexity of work at the time of manufacturing the steel cord and the composite sheet and the handling of the cord were displayed as “workability” as an index. The larger the index, the higher the workability.

  The cords of the present invention (Examples) are excellent in rubber penetration and fatigue resistance, have a relatively low low load elongation, and have little deterioration in workability. On the other hand, in the steel cord of the comparative example, the ratio of the maximum corrugation angle and the twist angle is out of the range of 1.2 to 2.0, and this ratio is 1.161 (less than 1.2). Those having a low rubber penetration property and those having this ratio of 2.039 (greater than 2.0) have a high low load elongation and poor fatigue resistance and workability.

It is sectional drawing (a) of the steel cord of an example of embodiment of this invention, and sectional drawing (b) of the steel cord of another example. It is a side view of the steel cord shown to (a) of FIG. The figure which shows the locus | trajectory which is arrange | positioned horizontally after untwisting the strand (normal filament) which does not have a caulking except for the spiral cord for the cord twist of the steel cord shown to (a) of FIG. a) and a diagram (b) showing a trajectory projected on a horizontal plane after untwisting an element wire (spiral filament) having a small spiral-like twist different from a spiral twist for twisting a cord and arranging it horizontally .

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Steel cord 11 Elementary wire with small spiral shaped 12 Straight wire 20 Steel cord 21 Wire with wavy wire 22 Straight wire C1, C2 Crevice B1, B2 Hollow part P Twist pitch P1 Spear pitch r1 Spiral habit reference line for normal filament cord twist α1 Angle between tangent and reference line of normal filament r2 Spiral habit reference line for spiral filament cord twist α2 Spiral filament tangent and reference line Angle with

Claims (1)

Steel with a single layer twist formed by twisting n strands (n = 3 to 6), and at least one strand having a small spiral or wavy comb separate from the spiral for cord twist Code,
At least one of the strands having the spiral or wave-like bend is tangent to the trajectory of the strands on the projection plane when the strands after the steel cord is untwisted are horizontally arranged and projected onto a horizontal plane. The steel cord for reinforcing rubber products is characterized in that the maximum value of the angle between the wire and the reference line of the spiral habit for twisting the cord is 1.2 to 2.0 times the cord twist angle.

Images