JP5465399B2 - Steel cord for reinforcing rubber products - Google Patents

Description

  The present invention relates to a steel cord for reinforcing rubber products used as a reinforcing material for rubber products such as vehicle tires and industrial belts.

  As a steel cord for reinforcing rubber products (hereinafter, also simply referred to as steel cord or cord) used as a reinforcing material for rubber products such as tires and belts, the side around the core (core) consisting of a plurality of strands ( There is a steel cord in which multiple strands that form a sheath are twisted together. For example, in a steel cord having a 2 + 2 structure with two core wires and two side wires, the two core wires are substantially parallel and do not twist each other. It has been conventionally known that the two strands of wire are twisted together in the same direction and pitch as the direction and pitch of twisting the core and the side (see, for example, Patent Document 1).

  In this way, the steel cord of the 2 + 2 structure is such that the two strands that become the core are substantially parallel and do not twist each other, and the two strands that are the sides are in the direction of twisting between the core and the side and By twisting each other in the same direction and pitch as the pitch, rubber penetration can be ensured, and two strands that are substantially parallel and have no twists in the core are crossed in the cord cross section. It is arranged in one direction, and two strands on the side are twisted together, so that the cross section of the cord is thin and flat in the height direction. For example, a rubber sheet with a plurality of cords aligned in parallel to each other When it is embedded in a tire as a reinforcing material for a tire, the thickness of the rubber sheet can be reduced, and the degree of freedom in forming the tire is increased.

  A plurality of strands on the side when a plurality of strands that are cores are substantially parallel and do not twist each other, and the strands that constitute the core are arranged in one direction in the cord cross section It is not limited to a steel cord having a 2 + 2 structure that the cord cross-section becomes a thin flat shape in the height direction by being twisted together. Even in the case of a 3 + 2 structure with three core wires and two strands on the side, or a steel cord with a 4 + 3 structure with four core wires and three strands on the side, The three or four strands are substantially parallel and are not twisted together, and the three or four core strands are arranged in one direction in a substantially straight line in the cord cross section. The cord cross-sectional shape is increased in the height direction by twisting two strands (in the case of three core strands) or three strands (in the case of four core strands) on the side It becomes a relatively thin super flat shape. That is, the steel cord of N + (N−1) structure in which (N−1) strands on the side are wound around the core composed of N (N = 3 to 4) strands, By configuring the N strands to be substantially parallel to each other and arranged in one direction in a substantially straight line in the cord cross section, a steel cord having a super flat cross section can be obtained.

  Separately, for example, in a steel cord of 3 + 2 structure, a virtual line connecting the centers of the three strands that become cores in the cord cross section is arranged in a side-by-side arrangement in which the shape is a straight line or an obtuse triangle, and the three cores that become the core There has been known one in which at least one of the strands is corrugated to promote the penetration of rubber into the core (see, for example, Patent Document 2).

Japanese Examined Patent Publication No. 2-29408 JP-A-9-175112

  As described above, the steel cord of N + (N−1) structure in which (N−1) strands on the side are twisted around the core composed of N (N = 3 to 4) strands is For example, in the case of a cord having a 3 + 2 structure, the cross-sectional shape can be increased by adopting a configuration in which all of the three core wires serving as the core are substantially parallel to each other and aligned in one direction in a substantially straight line in the cord cross section. It can be a flat steel cord. However, for example, in the case of a 3 + 2 structure cord, when all of the three core wires that are the cores are substantially parallel to each other, the three core wires that are the cores usually have a substantially straight shape, and these three wires A core consisting of strands of a substantially straight shape is positioned at the center in a state of being substantially straight in the longitudinal direction of the cord, and is twisted so that the strands on the side are wound around the core in a substantially straight state It becomes. In this case, the cord is in a state in which the strand on the side is easier to extend than the strand of the core. Therefore, when a tensile load is applied to the cord and the cord is stretched, the tensile load is not evenly distributed between the core strand and the side strand, but acts on the strand of the core (tensile load). Will act, resulting in poor fatigue resistance. In other words, it is possible to make an ultra-flat cord with a configuration in which three strands that are cores are arranged in one direction in a substantially straight line in the cord cross section, and two strands that are on the side are twisted around each other. However, the fatigue resistance cannot be sufficiently increased.

  In addition, as described above, for example, a steel cord having a 3 + 2 structure, a virtual line connecting the centers of three strands serving as cores in the cord cross section is arranged in a side-by-side arrangement in a linear or obtuse triangle shape, and the three cores Some of the strands have been made to corrugate by facilitating the corrugation of at least one of the strands. In such a case, at least one of the core strands has a straight shape. It is thought that the bias of the tensile load is alleviated for the element wire, but even in that case, the tensile load is not necessarily distributed evenly to all of the core element wire and the side element wire. In addition, the corrugation applied to the core wire in order to promote the penetration of rubber is preferably corrugated so that the direction of the wave height is transverse to the side-by-side direction of the core wires. Because In that case, the code of the cross-sectional shape is not a flat.

  Also, even if the core strand is straight in the state of the strand before twisting the cord, if the cord twist pitch is reduced, the core strand will also be twisted in the cord state, The force applied to the core wire when the tensile load is applied is somewhat relaxed. However, there is a limit to this, and when the twist pitch is reduced, the productivity of the cord deteriorates.

  An object of the present invention is to make a steel cord for reinforcing rubber products used as a reinforcing material for rubber products such as vehicle tires and industrial belts to be super flat and excellent in fatigue resistance.

The steel cord for reinforcing rubber products according to the present invention has N + (N−1) obtained by twisting (N−1) strands on the side around a core composed of N (N = 3 to 4) strands. ) A steel cord having a structure in which all N core wires serving as cores are substantially parallel to each other and arranged in one direction in a substantially straight line in the cord cross section, and have a phase aligned in the longitudinal direction of the cord ( N core strands that are cores are corrugated in a direction in which they are arranged in a substantially straight line, and the phases are aligned with each other in the longitudinal direction of the cord. 1) The strands have the same strand diameter D, and the waveform amplitude (the apparent wave height of the core in the cord state) d and the strand diameter D are (N−1.5) ≦ d / D ≦ (N−0.6) is satisfied, that is, when N = 3, 1.5 ≦ d / D ≦ 2.4 is satisfied, and when N = 4, 2.5 ≦ d / D 3.4 and satisfies the.

  In this steel cord, N (N = 3 to 4) strands that are cores are all substantially parallel to each other and arranged in one direction in a substantially straight line in the cord cross section, and are on the side around (N−1). ) Since the strands of the wires are twisted together, the cord cross-section has an ultra-flat shape, and the substantially parallel and N-core wires that are the cores are aligned in the longitudinal direction of the cord. And when the amplitude d of the waveform and the wire diameter D satisfy (N−1.5) ≦ d / D ≦ (N−0.6), when a tensile load is applied to the cord, The core wire and the side wire extend together, and the tensile load is appropriately distributed between the core wire and the side wire, resulting in a cord with high breaking strength and excellent fatigue resistance It becomes.

  If d / D> (N−0.6), the amplitude d of the core wire waveform is too large, the core wire tends to be excessively stretched, and the tensile load is biased toward the side wire. , The breaking strength of the cord is lowered, and the fatigue resistance is deteriorated.

  Also, if d / D <(N-1.5), the core wire has a waveform amplitude d that is too small, is nearly straight, is difficult to stretch, and the tensile load is biased toward the core wire. Since it cannot be sufficiently relaxed, the breaking strength of the cord is not sufficiently increased, and the fatigue resistance is not sufficiently improved.

  ADVANTAGE OF THE INVENTION According to this invention, the steel cord for rubber product reinforcement can be made super flat and excellent in fatigue resistance while increasing the twist pitch to reduce the production cost. For example, when a reinforcing material such as a tire is formed by arranging a plurality of cords parallel to each other and embedded in a rubber sheet, the rubber sheet can be thin, strong, and excellent in fatigue resistance.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 relates to an example of an embodiment of the present invention, (a) is a plan view of a steel cord, (b) is a side view of the steel cord, (c) is a sectional view of the steel cord, and FIG. It is explanatory drawing which shows the waveform in the cord state of the strand of the core of the steel cord shown in FIG.

  The steel cord of this embodiment is a steel cord for reinforcing rubber products used as a reinforcing material for vehicle tires, industrial belts, etc., and is composed of five strands (steel filaments) 1 to 5, and 5 The wire strands 1 to 5 have the same wire diameter (wire diameter), and the three wire strands 1 to 3 become cores, and around the core composed of the three strands 1 to 3 This is a 3 + 2 steel cord in which two strands 4 and 5 on the side are twisted together. The wire diameters of the five strands 1 to 5 are, for example, 0.20 to 0.38 mm. Further, the twist pitch of the cord is, for example, 10 to 20 mm.

In this steel cord, all of the core wires (three core wires) 1 to 3 are substantially parallel to each other in the cord state as shown in FIGS. 1 (a) and (b), and , together arranged in one direction (horizontal direction) in a substantially linear shape in the coding section, as shown in FIG. 1 (c), a waveform whose phase is aligned to each other in the cord longitudinal direction as shown in FIG. 1 (a) ( (Corresponding to a waveform in which phases are aligned in the longitudinal direction of the cord, in which N strands as cores are corrugated in a direction in which they are arranged substantially linearly) .

  The waveforms of the core strands 1 to 3 are as shown in FIG. 2, and the amplitude of the waveform (the apparent wave height of the core in the state of the cord) d and the strand diameter D are 1.5 ≦ d / D ≦ The relationship of 2.4 is satisfied.

  In this steel cord, all of the three strands 1 to 3 as the core are substantially parallel to each other and arranged in one direction in a substantially straight line in the cord cross section, and the two strands 4 on the sides around the strand 4 5 is twisted together so that the cord cross-section has a super flat shape, and the three parallel wires 1 to 3 that are substantially parallel to each other have a waveform in which the phases are aligned in the longitudinal direction of the cord. And when the tension d is applied to the cord when the amplitude d of the waveform and the wire diameter D satisfy 1.5 ≦ d / D ≦ 2.4, The side strands 4 and 5 are stretched together, and the tensile load is appropriately dispersed in the core strands 1 to 3 and the side strands 4 and 5, resulting in a high breaking strength and fatigue resistance. Excellent code.

  If d / D> 2.4, the amplitude d of the waveform of the core strands 1 to 3 is too large, and the core strands 1 to 3 tend to be excessively stretched. Therefore, the breaking strength of the cord is lowered and the fatigue resistance is deteriorated. Further, when d / D <1.5, the core wires 1 to 3 have a waveform amplitude d that is too small, close to a substantially straight shape, hardly stretched, and the tensile load is reduced to the core wires 1 to 3. Since it is not possible to sufficiently relax the bias, the cord breaking strength is not sufficiently increased, and the fatigue resistance is not sufficiently improved.

  The illustrated example is an embodiment applied to a steel cord having a 3 + 2 structure, but the present invention can also be applied to a steel cord having a 4 + 3 structure. In this case, the steel cord (not shown) is composed of seven strands (steel filaments), and these seven strands have the same wire diameter (strand diameter), and the four strands are cores ( 4 + 3 steel cord in which three strands on the side are twisted around the core composed of the four strands. The wire diameter of the seven strands is, for example, 0.20 to 0.38 mm. Further, the twist pitch of the cord is, for example, 10 to 20 mm.

  The steel cord has all the core strands (four core strands) arranged substantially parallel to each other in the cord state and arranged in one direction (lateral direction) in a substantially straight line in the cord cross section. It exhibits a waveform whose phases are aligned with each other in the longitudinal direction. The waveform of the core wire is still as shown in FIG. 2, and in this case, the amplitude (the apparent wave height of the core in the state of the cord) d and the wire diameter D are 2.5 ≦ d. The relationship /D≦3.4 is satisfied.

  In this steel cord, all four strands that are cores are substantially parallel to each other and arranged in one direction in a substantially straight line in the cord cross section, and the three strands that are on the sides are twisted around each other. As a result, the cross section of the cord becomes ultra-flat, and the substantially parallel and core four strands exhibit a waveform in which the phases are aligned in the longitudinal direction of the cord. When the wire diameter D satisfies 2.5 ≦ d / D ≦ 3.4, when a tensile load is applied to the cord, both the core wire and the side strand extend, and the core As a result, the tensile load is appropriately dispersed between the element wire and the element wire on the side, and the cord has a high breaking strength and excellent fatigue resistance.

  In this case, if d / D> 3.4, the amplitude d of the waveform of the core strand is too large, the core strand tends to be excessively stretched, and the tensile load is biased toward the side strand. The breaking strength of the cord is lowered and the fatigue resistance is deteriorated. Moreover, when d / D <2.5, the core wire has a waveform amplitude d that is too small, is close to a substantially straight shape, is not easily stretched, and the tensile load is sufficiently applied to the core wire. Therefore, the breaking strength of the cord is not sufficiently increased, and the fatigue resistance is not sufficiently improved.

  Samples (Examples 1 to 3) to which the present invention was applied were prepared, and fatigue resistance and shape (uniformity) were evaluated. The results are shown in Table 1 in comparison with the evaluation of the conventional example and Comparative Examples 1 and 2.

  Example 1 is a steel cord having a 3 + 2 structure, in which all three strands of the core are substantially parallel to each other in the cord state and arranged in one direction (lateral direction) in a substantially straight line in the cord cross section, and in the cord longitudinal direction The wire diameter is 0.25 mm, the twist pitch is 14 mm, the amplitude of the core wire waveform (the apparent wave height of the core in the cord state) d and the wire diameter D Is d / D = 1.75, which satisfies 1.5 ≦ d / D ≦ 2.4.

  Example 2 is a steel cord having a 3 + 2 structure, in which all three strands of the core are substantially parallel to each other in the cord state, and arranged in one direction (lateral direction) in a substantially straight line in the cord cross section, and the cord longitudinal direction The wire diameter is 0.25 mm, the twist pitch is 16 mm, the amplitude of the core wire waveform (apparent wave height of the core in the cord state) d and the wire diameter D Is d / D = 2.2, which satisfies 1.5 ≦ d / D ≦ 2.4.

  Example 3 is a steel cord having a 4 + 3 structure, in which all four strands of the core are substantially parallel to each other in the cord state and arranged in one direction (lateral direction) in a substantially straight line in the cord cross section, and the cord longitudinal direction The wire diameter is 0.35 mm, the twist pitch is 18 mm, the amplitude of the core wire waveform (apparent wave height of the core in the cord state) d and the wire diameter D Is d / D = 2.56, which satisfies 2.5 ≦ d / D ≦ 3.4.

  In addition, the conventional example is a steel cord with a 2 + 2 structure, and the two core wires that are cores are substantially parallel and do not twist each other (aligned in one direction in the cord cross section), the wire diameter is 0.25 mm, and the twist pitch 14 mm, the core wire has a gentle waveform due to the twist of the cord, and the relationship between the amplitude (apparent wave height of the core in the cord state) d and the strand diameter D is d / D = 0.3. It is.

  Comparative Example 1 is a steel cord having a 3 + 2 structure, in which all three strands of the core are substantially parallel to each other in the cord state and arranged in one direction (lateral direction) in a substantially straight line in the cord cross section. It has a waveform in which the phases are aligned in the longitudinal direction, the strand diameter is 0.25 mm, and the twist pitch is 14 mm. However, the relationship between the amplitude of the waveform of the core wire (the apparent wave height of the core in the state of the cord) d and the wire diameter D is d / D = 1.22, and 1.5 ≦ d / D ≦ 2. Does not satisfy 4.

  Comparative Example 2 is a steel cord having a 3 + 2 structure, and all three strands of the core are substantially parallel to each other in the cord state and arranged in one direction (lateral direction) in a substantially straight line in the cord cross section. It has a waveform in which the phases are aligned in the longitudinal direction, the strand diameter is 0.25 mm, and the twist pitch is 16 mm. However, the relationship between the amplitude of the core wire waveform (the apparent wave height of the core in the cord state) d and the wire diameter D is d / D = 2.48, and 1.5 ≦ d / D ≦ 2. Does not satisfy 4.

  For fatigue resistance, a composite sheet is created by embedding a plurality of cords in a rubber material, and this sheet is used to create a composite sheet until the cord breaks through fretting wear, buckling, etc. The number of repetitions was determined and the index was displayed with the conventional example of 2 + 2 structure as 100.

  With respect to the shape (uniformity), the conventional example of the 2 + 2 structure was set as a reference (uniform), and the case of better shape was “uniform”, and the case of other cases was “non-uniform”.

  From this evaluation result, the steel cords of Examples 1 to 3 which are samples to which the present invention is applied are much more excellent in fatigue resistance than the conventional example and Comparative Examples 1 and 2, and the uniformity of the shape. It turns out that it is also excellent.

It relates to an example of an embodiment of the present invention, (a) is a plan view of a steel cord, (b) is a side view of the steel cord, (c) is a sectional view of the steel cord. It is explanatory drawing which shows the waveform in the cord state of the strand of the core of the steel cord shown in FIG.

Explanation of symbols

1, 2, 3 strands (core strands)
4, 5 strands (side strands)
d Waveform amplitude D Wire diameter

Claims (1)

A steel cord of N + (N-1) structure in which (N-1) strands on the side are wound around a core composed of N (N = 3-4) strands,
The length of the cord in which the N strands serving as the core are all substantially parallel to each other and arranged in one direction in a substantially straight line in the cord cross section, and the N strands are corrugated in a direction in which the N strands are arranged in a substantially straight line Presents a waveform whose phases are aligned with each other,
The N strands serving as the core and the (N-1) strands serving as the side have the same strand diameter D,
The steel cord for reinforcing rubber products, wherein the amplitude d of the waveform and the wire diameter D satisfy (N-1.5) ≦ d / D ≦ (N−0.6).

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