JP5049734B2 - Steel cord for reinforcing rubber products and manufacturing method thereof - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a steel cord for reinforcing rubber products (hereinafter sometimes simply referred to as “cord”) used as a reinforcing material for rubber products such as automobile tires and conveyor belts.

  Conventionally, a plurality of strands have been used as steel cords with a bundle of two layers of 1 × 13 or the like and a bundle of three layers of 1 × 19 used for reinforcing rubber products such as automobile tires and conveyor belts. A so-called closed twisted cord, in which the cords are tightly twisted and brought into close contact with each other, is generally used. However, such a closed twisted cord has a hollow portion that is closed between adjacent strands. When a composite sheet is formed by sandwiching the cord between two rubber sheets and heating and compressing the rubber, The material does not invade the cavity between the strands, and it is a composite that simply wraps the cord with the rubber sheet, and the rubber material completely penetrates into the cavity between the cord strands. Does not become a so-called perfect composite. Therefore, when a composite sheet obtained by compressing a conventional closed twisted cord sandwiched between rubber sheets is incorporated into, for example, an automobile tire, the adhesion between the rubber material and the cord is insufficient, and the rubber material peels off from the cord when the automobile is running. The so-called separation phenomenon is highly likely to occur, and when the moisture that has penetrated into the rubber material reaches the cavity of the cord, the moisture propagates through the cavity and quickly propagates in the longitudinal direction of the cord to corrode the cord. As a result, the mechanical strength of the cord is significantly reduced.

  Therefore, as shown in FIG. 5, in the cord 50 having the two-layer structure, the core strand group and the outer layer strand group are each composed of a predetermined number of strands 51 and 52, and are twisted to a part of the core strand group. It has a small helical comb that is different from the matching comb (the example shown in the figure shows a case where a helical comb is provided in one of the three strands 51 of the core strand group. .) It is proposed to be. Since the cord 50 is bundle-twisted, the manufacturing cost can be reduced. In addition, there is a gap 53 communicating with the outside between a strand provided with a spiral bevel (referred to as “spiral strand”) and a strand not provided with a spiral bevel (referred to as “non-spiral strand”). Rubber material invades. However, the cord in which only a part of the core wire group is provided with a spiral bend in this way becomes a closed cavity portion 54 surrounded by the non-spiral strands, and rubber does not enter there. .

  Further, as shown in FIG. 6, in the cord 60 having a bundle-twisted two-layer structure, the core strand group and the outer layer strand group are each composed of a predetermined number of strands 61 and 62. It is considered that the strand 61 is a spiral strand (see, for example, Patent Document 1). By doing so, the gap 63 communicating with the outside is enlarged, and the closed cavity is eliminated. However, if all the strands 61 of the core strand group are spiral strands in this way, the elongation of the cord becomes larger than necessary, and the rigidity of the tire or the like is reduced.

  In addition, as shown in FIG. 7, in the cord 70 having a three-layer structure, the core strand group, the intermediate strand group, and the side strand group are each composed of a predetermined number of strands 71, 72, 73, and the central strand group Alternatively, it has a small helical comb different from the twist for twisting a part of the intermediate strands (in the illustrated example, three of the nine strands 72 of the intermediate strands are included in three strands). (The case where a spiral habit is provided is shown.)) What has been proposed has been proposed (see, for example, Patent Document 2). The cord 70 communicates with the outside between a strand 72 having a spiral bend (referred to as “spiral strand”) and a strand not provided with a spiral bevel (referred to as “non-spiral strand”). A gap 74 is formed and the rubber material enters. The strand 71 of the core strand group engages with any strand 72 of the intermediate strand group, and the strand 72 of the intermediate strand group engages with any strand 73 of the side strand group. Therefore, there is no degree of freedom in the cord longitudinal direction of the core strand group and the intermediate strand group, and no shift movement in the cord longitudinal direction occurs. However, in the conventional cords in which the spiral strands are provided in the core strand group or the partial strand of the intermediate strand group in this way, the portion surrounded by the non-spiral strands becomes a closed hollow portion, Does not penetrate rubber material.

  Therefore, as shown in FIG. 8, in the cord 80 having a three-layer structure, the core strand group, the intermediate strand group, and the side strand group each include a predetermined number of strands 81, 82, and 83. It is conceivable that all the strands 82 of the line group are spiral strands. By doing so, the gap 84 communicating with the outside is enlarged, and the closed cavity is eliminated. However, if all the strands 82 of the intermediate strand group are spiral strands as described above, the elongation of the cord becomes larger than necessary, and the rigidity of the tire or the like is lowered.

Japanese Utility Model Publication No. 4-60590 JP 2000-80578 A

  Therefore, it is a problem to obtain a steel cord for reinforcing rubber products having a bundle-twisted two-layer structure or a bundle-twisted three-layer structure with good rubber penetration and low load elongation.

The above-mentioned subject is a group of strands constituting an outer layer of a steel cord having a 1 × P (P = 8 to 13) bundle-twisted two-layer structure or a 1 × Q (Q = 16 to 19) bundle-twisted three-layer structure. A gap exists between at least some of the strands of the strands, and all strands of the strand group constituting the central layer in the bundle-twisted two-layer structure or the intermediate layer in the bundle-twisted three-layer structure are twisted together In addition to the habit for twisting, the pitch is smaller than that for twisting, and adjacent strands of the strands constituting the central layer or the intermediate layer are substantially parallel to the cord central axis. The portion where the difference between the twist angle of the strands of the strands constituting the central layer or the intermediate layer in contact with each other in parallel is large and the twist angle of the strands of the strands constituting the outer layer is It exists partially in a discontinuous arrangement in the direction and constitutes the central layer or the intermediate layer. Appearance of the strands of the strand group constituting the central layer or the intermediate layer at a location where the difference between the strand angle of the strands of the strand group formed and the twist angle of the strands of the strand group constituting the outer layer is large A cord twist calculated from a cord effective diameter (D) and a cord twist pitch (Pc) defined by a twist angle (α) of the wire and a diameter of a circle connecting the centers of the strands of the strands constituting the outer layer This can be solved by configuring so that the relationship with the angle (β) satisfies the following formula 1.
(Formula 1) 1.5 ° ≦ α−β ≦ 4.5 °

  This cord has a gap between at least some of the strands (side strands) of the strands (side strands) constituting the outer layer, and constitutes a central layer in a bundle-twisted two-layer structure All the strands of the strand group (core strand group) or the strand group (intermediate strand group) constituting the intermediate layer in the bundle-twisted three-layer structure have a smaller pitch than the twist for twisting. Thus, between the side strand group and the core strand group in the bundle-twisted two-layer structure, or between the intermediate strand group and the side strand group in the bundle-twisted three-layer structure, and between the intermediate strand group and the core strand There is no closed cavity between the group, and the rubber material that has entered through the gap between the side strands is the strand of the core strand group (core strand) and side strand in the bundle-twisted two-layer structure Between the strands of the intermediate strand group in a three-layer structure with a bundle twist. Entering between the intermediate strand group and Shinmotosen group via a gap. At that time, the adjacent strands of the strand group constituting the central layer in the bundle-twisted two-layer structure or the intermediate layer in the bundle-twisted three-layer structure are contacted in approximately parallel so that the strands are substantially parallel to the cord central axis. The location where the difference between the strand angle of the strands of the strand group constituting the central layer or the intermediate layer and the strand angle of the strands of the strand group constituting the outer layer is discontinuous in the longitudinal direction of the cord. By being partially present, the strands of the side strands are prevented from falling due to the uniform twist angles, and a rubber intrusion path is secured.

  In addition, this cord makes contact in approximately parallel so that adjacent strands of the strand group constituting the central layer in the bundle-twisted two-layer structure or the intermediate layer in the bundle-twisted three-layer structure are substantially parallel to the cord central axis. Since the portions are partially present in a discontinuous arrangement in the longitudinal direction of the cord, the elongation of the cord is suppressed.

  In particular, this cord has a twist angle of the strands of the strands constituting the central layer in the bundle-twisted two-layer structure or the intermediate layer in the bundle-twisted three-layer structure and the strands of the strands of the strands constituting the outer layer. The apparent twist angle (α) of the strands of the strands constituting the center layer in the bundle-twisted two-layer structure or the intermediate layer in the bundle-twisted three-layer structure, and the cord twist angle (where the difference from the corner becomes large) When the relationship with β) satisfies 1.5 ° ≦ α−β ≦ 4.5 °, both fatigue resistance and rubber penetration are ensured.

  When α-β exceeds 4.5 °, the apparent twist angle of the strands of the strands constituting the central layer in the bundle-twisted two-layer structure or the intermediate layer in the bundle-twisted three-layer structure becomes too large, and the outer layer The part of the group of strands (side strand group) that makes up the wire becomes smaller (close to point contact) and the fretting wear of that part (the strands rub against each other and wear) Phenomenon) and fatigue resistance decreases. In this case, the fatigue resistance is also reduced by a decrease in twist stability (disturbed twist). On the other hand, when α-β is smaller than 1.5 °, the twisted shape is not much different from the closed twist, the gap between the strands is reduced, and the rubber penetration is reduced.

  In the cord having the above-described configuration, the habit having a smaller pitch than the habit for twisting is preferably a habit obtained by pressing a strand after forming a helical habit on the strand. Even if a wire is passed between a pair of gears whose teeth have been processed into a desired shape, a small wrinkle can be obtained by bending the wire into a zigzag shape. The degree of work becomes greater than the part where there is not, stress remains in the bent part where the degree of work is large, and stress due to external force is added to this, so that the stress at the bent part becomes excessive and the fatigue resistance decreases. On the other hand, the wrinkle obtained by applying a pressurizing process after applying a helical wrinkle has a uniform degree of processing at any location, so that excessive stress does not act and it has excellent fatigue resistance. Become.

  In addition, the pitch P1 is P1 = 0.2Pc to 0.5Pc (where Pc is the cord twist pitch) and the wave height h is h = 0.2d to 1 when the pitch is smaller than the twist for twisting. .2d (where d is the wire diameter). If the pitch P1 is smaller than 0.2 Pc, excessive plastic deformation is applied to cause excessive stress at the time of soldering, so that the strands are easily broken and the productivity is lowered, and the pitch P1 is less than 0.5 Pc. If it is large, the tensile force will not be evenly applied, the twist stability will deteriorate, and the fatigue resistance will deteriorate. Also, if the wave height h is less than 0.2d, the gap between the wires becomes too small, and even if a rubber material with good fluidity is used, the rubber material can sufficiently penetrate into the interior during pressure vulcanization. If the wave height h is greater than 1.2 dmm, the twist stability is deteriorated and the fatigue resistance is deteriorated. Note that the values of the pitch P1 and the wave height h, which have a smaller pitch than the twists for twisting, coincide with those of the strands obtained by untwisting the cord.

  As described above, according to the present invention, it is possible to obtain a steel cord for reinforcing rubber products having a bundle-twisted two-layer structure or a bundle-twisted three-layer structure that has good rubber penetration, low low load elongation, and excellent fatigue resistance. Can do.

  Hereinafter, a steel cord for reinforcing rubber products according to an embodiment of the present invention (hereinafter referred to as “steel cord” or simply “cord”) will be described with reference to the drawings.

  FIG. 1A shows a cross-sectional structure of a steel cord having a 1 × 11 structure, which is an example of an embodiment of a 1 × P (P = 8 to 13) bundle-twisted two-layer structure. This cord (steel cord) 10 has a 1 × 11 bundle-twisted two-layer structure and is pressed after all three strands (core strands 11) arranged on the center side are provided with helical creases. It has an almost sinusoidal shape with a pitch smaller than the twist for twisting, arranges 8 strands (side strands 12) on the outside and twists them at once, and the bundle-twisted two-layer structure thus formed The cord is pressed from the direction orthogonal to the longitudinal direction of the cord, and is between at least some of the strands (side strands 12) of the strand group (side strand group) constituting the outer layer. While the gap 13 exists, all the strands (core strands 11) of the strand group (core strand group) constituting the core layer are twisted in a substantially two-dimensional wave shape separately from the twist for twisting. It has a habit with a smaller pitch and wave height than the habit for. This substantially two-dimensional wavy beak is obtained by adding a helical beak to the strand (core strand 11) and then pressing the strand, and is substantially sinusoidal in the state of the strand before twisting. is there.

  FIG. 1B shows a cross-sectional structure of a steel cord having a 1 × 16 structure, which is an example of an embodiment of a bundle-twisted three-layer structure of 1 × P (P = 16 to 19). This cord (steel cord) 20 is a 1 × 16 bundle-twisted three-layer structure with a single strand (core strand 21) as the center, and a small sine wave around it (for twisting) 5 strands (intermediate strands 22) having a pitch smaller than the habit are disposed, 10 strands (side strands 23) are disposed on the outer side (outermost), and twisted at once. The cord of the bundle-twisted three-layer structure formed in this way is pressed from the direction orthogonal to the longitudinal direction of the cord, and at least a part of the strand group (side strand group) constituting the outer layer ( A gap 24 exists between the side strands 23), and all the strands (intermediate strands 22) of the strand group (intermediate strand group) constituting the intermediate layer are twisted for twisting. Separately, it is almost two-dimensional wavy and has a smaller pitch and wave height than the twist for twisting. It has. This substantially two-dimensional wave-like wrinkle is a habit obtained by adding a helical wrinkle to an element wire (intermediate element wire 22) and then pressing it. In the state of the element wire before twisting, it is substantially sinusoidal. is there.

  The substantially sinusoidal habit before twisting of the core strand 11 or the intermediate strand 22 in these cords 10 and 20 is as shown in FIG. 2, and the pitch is from wave trough to trough or from mountain to crest. The wave height means the height (amplitude) h from the valley of the wave to the mountain. The core wire 11 or the intermediate strand 2 has a substantially two-dimensional wavy pitch P1 of P1 = 0.2Pc to 0.5Pc (where Pc is the cord twist pitch), and the wave height h is h = 0.2d to 1.2d (where d is the wire diameter). If the pitch P1 is smaller than 0.2 Pc, excessive plastic deformation is applied to cause excessive stress at the time of soldering, so that the strands are easily broken and the productivity is lowered, and the pitch P1 is less than 0.5 Pc. If it is large, the tensile force will not be evenly applied, the twist stability will deteriorate, and the fatigue resistance will deteriorate. Also, if the wave height h is less than 0.2d, the gap between the wires becomes too small, and even if a rubber material with good fluidity is used, the rubber material can sufficiently penetrate into the interior during pressure vulcanization. If the wave height h is greater than 1.2 dmm, the twist stability is deteriorated and the fatigue resistance is deteriorated. In addition, it is preferable that the strand diameter d is 0.15-0.40 mm. If the wire diameter d is less than 0.15 mm, the strength of the steel cord is reduced, and if it exceeds 0.40 mm, the flexibility is deteriorated. The cord twist pitch Pc is usually 8.0 to 18.0 mm.

  These cords 10 and 20 are, as shown in FIGS. 3 (a) and 3 (b), the strands of the core strand group (core strand 11) or the strands of the intermediate strand group (intermediate) The strands 22) are arranged in a discontinuous arrangement in the longitudinal direction of the cord and partially contact in parallel, and the twist angle (apparent) of the core strand 11 or the intermediate strand 22 at a location (range) S in contact with the parallel Is 0 (zero), and the difference between the strands of the strands (side strands 12, 23) of the strands (side strands) constituting the outer layer (not shown) is different from that of the strands (side strands 12, 23). The twist angle α in the non-parallel portion of the core strand 11 or the intermediate strand 22 is small in difference from the cord twist angle.

  And the core strand 11 or the intermediate strand 22 in these cords 10 and 20 has a difference with the twist angle (cord strand angle) of the side strands 12 and 23 of these core strand 11 or the intermediate strand 22. Calculated from the apparent twist angle α of the core strand 11 or the intermediate strand 22 at the larger portion, the cord effective diameter D defined by the diameter of the circle connecting the centers of the side strands 12 and 23, and the cord twist pitch Pc The cord twist angle β is 1.5 ° ≦ α−β ≦ 4.5 °.

The apparent twist angle α, the cord effective diameter D, and the cord twist angle β of the core strand 11 in the cord 10 (bundle-twisted two-layer structure) are as shown in FIGS. The apparent twist angle α is the maximum twist angle of the core strand 11 (see FIG. 4A), and the cord effective diameter D is the diameter of the circle connecting the centers of the side strands 12 (cord diameter). A−element wire diameter d) (see FIG. 4B), and the cord twist angle β is an angle calculated from the cord effective diameter D and the cord twist pitch P by β = tan ⁻¹ D / P. Yes (see FIG. 4C). The apparent twist angle α, the cord effective diameter D, and the cord twist angle β of the intermediate strand 22 in the cord 20 (bundle-twisted three-layer structure) are the same.

  The side strands 12 are arranged outside the plurality of core strands 11 (three in the example of FIG. 1) having a small sinusoidal shape as shown in FIG. When the cord is pressed from the direction perpendicular to the longitudinal direction of the cord, the plurality of core strands 11 are crushed with a portion having a predetermined twist angle α by periodically conforming with an interval in the longitudinal direction of the cord. It is possible to form a portion that is in contact with each other in parallel and has a twisted structure as shown in FIG. In addition, a plurality of (five in the example of FIG. 2) intermediate strands 22 having small sinusoidal wrinkles are arranged around the core strand 21 (core strand group), and on the outer side (outermost). When the side strands 23 are arranged and twisted at a time so that at least one of the intermediate strands 22 contacts the core strand 21 at almost all locations in the longitudinal direction of the cord, a plurality of intermediate strands are obtained. The line 22 can be formed into a part that is periodically adapted to the cord longitudinal direction with an interval in the cord longitudinal direction to become a predetermined twist angle α, and a part that is in a crushed shape and that is in contact with each other in parallel, as shown in FIG. A twist structure as shown is obtained.

  The pressing process for processing the helical beak into a substantially sinusoidal bend and the pressing process after the stranded wire processing can be performed by a known pressing apparatus in which a plurality of freely rotating rollers are arranged in a staggered manner. However, the pressing means is not limited to this.

  The cord 10 in FIG. 1 is a group of strands in which a rubber material that has entered from a gap 13 between strands (side strands 12) of a strand group (side strand group) constituting the outer layer constitutes a central layer. It enters the gap 14 formed between the side strand 12 and the strand (core strand 11) having a small two-dimensional wavy shape of the (core strand group). Moreover, since all the strands (core strands 11) of the core strand group have a small two-dimensional wave shape, this cord 10 is a cavity closed between the side strand group and the core strand group. The part does not exist. Therefore, the rubber material easily enters. Furthermore, the cord 10 has a core wire 11 having a substantially two-dimensional wave-like bevel in contact with the cord in the parallel direction in the longitudinal direction of the cord. it can. Further, in the cord 10, the adjacent core strands 11 are brought into contact with each other substantially in parallel, and the portion where the difference between the twist angle of the core strand 11 and the twist angle of the side strand is large is discontinuous in the longitudinal direction of the cord. Since this arrangement is partially present, the side wires 12 are prevented from falling due to the uniform twist angles, and a rubber material intrusion path is secured.

  Further, the cord 20 in FIG. 2 is a gap formed by the rubber material that has entered from the gap 24 between the side strands 23 between the intermediate strands 22 having a small two-dimensional wavy shape of the intermediate strand group. 25 to enter between the intermediate strand group and the core strand group. Moreover, since all the intermediate wires 22 have a small two-dimensional wavy shape, the cord 20 is provided between the intermediate wire group and the side wire group, and between the intermediate wire group and the core wire group. There is no closed cavity between the two. Therefore, the rubber material easily enters. The cord 20 is a portion where the intermediate strands 22 come into contact with each other in substantially parallel so as to be substantially parallel to the cord central axis, and the difference between the twist angle of the intermediate strand 22 and the twist angle of the side strand 23 becomes large. However, since it is partially present in a discontinuous arrangement in the longitudinal direction of the cord, the side strands 23 are prevented from falling due to uniform twist angles, and a rubber material intrusion path is secured. Further, in the cord 20, at least any one of the intermediate strands 22 is always in contact with at least one of the core strands 21 at almost all locations in the longitudinal direction of the cord. The side strands 23 are also partially engaged. Therefore, the intermediate strand group does not shift in the longitudinal direction of the cord, and the twist is stabilized.

  And these cords 10 and 20 are especially the core strand 11 or intermediate | middle in the location where the difference with the twist angle (cord twist angle) of the side strands 12 and 23 of the core strand 11 or the intermediate strand 22 becomes large. When the relationship between the apparent twist angle α of the strand 22 and the cord twist angle β satisfies 1.5 ° ≦ α−β ≦ 4.5 °, both fatigue resistance and rubber penetration are ensured. . When α-β exceeds 4.5 °, the apparent twist angle of the core strand 11 or the intermediate strand 22 becomes too large, and the contact portion with the side strand 12 becomes small (close to point contact). , The fretting wear of the part (a phenomenon in which the wires are worn by rubbing with each other) increases and fatigue resistance decreases. In this case, the fatigue resistance is also reduced by a decrease in twist stability (disturbed twist). On the other hand, when α-β is smaller than 1.5 °, the twisted shape is not much different from the closed twist, the gap between the strands is reduced, and the rubber penetration is reduced.

  Further, in these cords 10 and 20, if the pitch is smaller than the twist for twisting provided on the core strand 11 or the intermediate strand 22, press the strand after adding a spiral to the strand. The degree of work is uniform at any location, no excessive stress is applied, and the fatigue resistance is excellent.

  As an example, a steel wire having a diameter of 5.5 mm was repeatedly subjected to patenting and wire drawing, and then subjected to brass plating on the surface to obtain a strand having a wire diameter of 0.175 to 0.30 mm. 4 types of 1 × 9 bundle-twisted two-layer cords, 2 types of 1 × 11 bundle-twisted two-layer cords, 4 types of 1 × 16 bundle-twisted three-layer cords, Two types of cords with a 1 × 19 bundle-twisted three-layer structure are manufactured, and seven types of cords with a 1 × 9 bundle-twisted two-layer structure, which is a comparative example, are used with the same strands, and a bundle of 1 × 11 Two types of cords with a twisted two-layer structure, two types of cords with a 1 × 16 bundle-twisted three-layer structure, and two types of cords with a 1 × 19 bundle-twisted three-layer structure were manufactured. Also, a conventional example of a cord of a bundle twist structure in which the same strands are used and a small spiral comb is provided on one of the core strands or the intermediate strand (1 × 9 bundle twist two-layer structure, 1 × 11 bundle-twisted two-layer structure, 1 × 16 bundle-twisted three-layer structure, and 1 × 19 bundle-twisted three-layer structure, respectively, and a conventional example of a closed twisted cord (1 × 9 bundle-twisted two-layer structure) 1 × 11 bundle-twisted two-layer structure, 1 × 16 bundle-twisted three-layer structure, and 1 × 19 bundle-twisted three-layer structure). And the rubber penetration | invasion property and fatigue resistance of the code | cord | chord of an Example were evaluated compared with the comparative example and the prior art example.

  The 1 × 9 bundle-twisted two-layer structure cord (4 types) and the 1 × 11 bundle-twisted two-layer cord (two types) are three strands that form a core strand group ( Core strands) are processed into strands having a small sine wave-like weave that is a plane wave (having a smaller pitch than that for twisting) by applying pressing to each of the strands. A core strand having a small sine wave shape and a side strand arranged on the outside are twisted at the same direction and at the same pitch at a time, and the bundle-twisted two-layer cord thus formed is orthogonal to the cord longitudinal direction. In this case, the relationship between the apparent twist angle α and the cord twist angle β in the non-parallel portion of the core strand is 1.5 ° ≦ α−β ≦ 4.5 °. It is what I did.

  Similarly, the 1 × 16 bundle-twisted three-layer structure cord (4 types) and the 1 × 19 bundle-twisted three-layer cord (two types), which are the examples, have five intermediate strands. After each strand is attached with a helical bevel, it is processed into a strand having a small sinusoidal wave that is a plane wave (having a smaller pitch than the twist for twisting) by pressing. A bundle formed by arranging a plurality of strands (intermediate strands) having a small sine wave shape around the strands (core strands) and twisting them together with the side strands arranged outside. A cord having a twisted three-layer structure is pressed from a direction perpendicular to the longitudinal direction of the cord, and at that time, the relationship between the apparent twist angle α and the cord twist angle β in the non-parallel portion of the core strand is 1.5. It is set to satisfy the following condition: ° ≦ α−β ≦ 4.5 °.

  In addition, a 1 × 9 bundle-twisted two-layer structure cord (7 types) and a 1 × 11 bundle-twisted two-layer cord (two types), which are comparative examples, are three strands that form a core strand group. After each wire (core strand) has a helical comb, it is processed into a strand with a small sinusoidal wave (a pitch smaller than the twist for twisting) that is a plane wave by pressing. The core strands having a small sine wave shape and the side strands arranged on the outside are twisted at the same direction and at the same pitch at the same time, and thus the cord of the bundle-twisted two-layer structure formed in the cord longitudinal direction In this case, the relationship between the apparent twist angle α and the cord twist angle β in the non-parallel portion of the core strand is α-β <1.5 ° or α-β>. The angle is set to 4.5 °.

  Similarly, a 1 × 16 bundle-twisted three-layer structure cord (4 types) and a 1 × 19 bundle-twisted three-layer cord (two types), which are comparative examples, are composed of five intermediate strands. After each strand is attached with a helical bevel, it is processed into a strand having a small sinusoidal wave that is a plane wave (having a smaller pitch than the twist for twisting) by pressing. A bundle formed by arranging a plurality of strands (intermediate strands) having a small sine wave shape around the strands (core strands) and twisting them together with the side strands arranged outside. A cord having a twisted three-layer structure is pressed from a direction perpendicular to the longitudinal direction of the cord, and the relationship between the apparent twist angle α in the non-parallel portion of the core wire and the cord twist angle β is α-β <1.5 ° or α-β> 4.5 ° A.

  In any of these examples and comparative examples, the helical wrinkle is obtained by using a wrinkling device that rotates with the supplied strand as an axis (Japanese Patent Publication No. 63-63293). Granted. The comb shape was adjusted by the spacing of the tacking pins, the dimension of the tacking pins, and the number of rotations rotating around the element wire. Moreover, the pressing process which processes a helical comb into a substantially sinusoidal pattern and the pressing process after the stranded wire processing were performed by a known pressing device in which a plurality of freely rotating rollers are arranged in a staggered manner.

  And the rubber penetration property was observed by observing a certain length by embedding each cord in a rubber material under a tensile load of 2 kg, taking out the cord after pressure vulcanization, disassembling the cord, and observing a certain length. The ratio of the length of traces in contact with the rubber to the length was evaluated as a percentage. If this percentage value is 80 or more, rubber penetration is good.

  In addition, fatigue resistance is determined by covering the cord with rubber and bending the cord into a substantially U shape in a hunter fatigue test (the bending shape is such that a stress of 800 MPa is applied to the maximum curvature point of the cord). In the case of the conventional example of closed twisting (closed), the surface of the inner layer strand (core strand or intermediate strand) is observed and evaluated by the degree of fretting wear. Is shown as an index with 100 being 100. The larger the number, the better the fatigue resistance.

The evaluation results are shown in Table 1.

  From Table 1, 1 × 9 bundle-twisted two-layer structure, 1 × 11 bundle-twisted two-layer structure, 1 × 16 bundle-twisted three-layer structure, 1 × 19 bundle-twisted three-layer structure The cord of the example has good rubber penetration (80% or more), and of course compared to the conventional example (spiral habit) with a spiral prick as well as the closed twist conventional example (closed) Of course, the rubber penetration is much better, the fatigue resistance is better (over 100 index), and of course, compared to the conventional example (spiral habit) with a spiral habit, It can be seen that the fatigue resistance is superior to the conventional example (closed).

It is sectional drawing (a) of the steel cord of 1 * 11 bundle twist two-layer structure of embodiment of this invention, and sectional drawing (b) of the steel cord of 1 * 16 bundle twist three layer structure. It is explanatory drawing of the pitch and wave height of the substantially sinusoidal habit which concerns on embodiment of this invention. Explanatory drawing (a) of twist structure of central strand group of steel cord of 1 × 11 bundle-twisted two-layer structure of embodiment of the present invention and intermediate strand group of steel cord of 1 × 16 bundle-twisted three-layer structure It is explanatory drawing (b) of a twist structure. Explanatory drawing (a) of apparent twist angle α of core wire in steel cord of 1 × 11 bundle-twisted two-layer structure of embodiment of the present invention, explanatory drawing (b) of cord effective diameter D and cord twist angle β It is explanatory drawing (c). It is sectional drawing of the steel cord in which one strand of a core strand group has a helical habit different from the habit for twisting by the conventional 1x12 bundle twist 2 layer structure. It is sectional drawing of the code | cord | chord which has the helical habit different from the habit for twisting all the strands of the core strand group by the conventional 1 * 12 bundle twist 2 layer structure. FIG. 6 is a cross-sectional view of a steel cord having a conventional 1 × 24 bundle-twisted structure in which some strands of an intermediate layer have a spiral bend different from the bend for twisting. It is sectional drawing of the code | cord | chord which has the helical habit different from the habit for twisting all the strands of the intermediate | middle layer by the conventional 1x24 bundle twist structure.

Explanation of symbols

10, 20 cord (steel cord)
11, 21 Core strand 12, 23 Side strand 13, 24 Gap 22 Intermediate strand α Apparent twist angle β Cord twist angle

Claims (3)

A steel cord having a 1 × P (P = 8 to 13) bundle-twisted two-layer structure or a 1 × Q (Q = 16 to 19) bundle-twisted three-layer structure, and at least a group of strands constituting the outer layer A gap exists between some of the strands, and all strands of the strand group constituting the central layer in the bundle-twisted two-layer structure or the intermediate layer in the bundle-twisted three-layer structure are used for twisting. In addition to the habit, the pitch is smaller than the habit for twisting, and the adjacent strands of the strands constituting the central layer or the intermediate layer are substantially parallel to the cord central axis. The portion where the difference between the twist angle of the strands of the strands constituting the center layer or the intermediate layer in contact with the parallel layer and the strand angle of the strands of the strands constituting the outer layer increases in the longitudinal direction of the cord. Partially present in a discontinuous arrangement, constituting the central layer or intermediate layer The apparent twist of the strands of the strand group constituting the central layer or the intermediate layer at a location where the difference between the strand angle of the strands of the strand group and the strand angle of the strands of the strand group constituting the outer layer becomes large The cord twist angle (D) calculated from the effective diameter (D) defined by the angle (α) and the diameter of the circle connecting the centers of the strands of the strands constituting the outer layer and the cord twist pitch (Pc) ( A steel cord for reinforcing rubber products, characterized in that the relationship with β) satisfies the following formula 1.
(Formula 1) 1.5 ° ≦ α−β ≦ 4.5 ° The steel cord for reinforcing a rubber product according to claim 1, wherein the habit having a smaller pitch than the habit for twisting is a habit obtained by pressing a strand after forming a helical habit on the strands. The pitch smaller than the twist for twisting is such that the pitch P1 is P1 = 0.2 Pc to 0.5 Pc (where Pc is the cord twist pitch), and the wave height h is h = 0.2 d to 1. The steel cord for reinforcing rubber products according to claim 1 or 2, wherein the steel cord is 2d (where d is a wire diameter).

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