Steel cord, tires

Abstract

This steel cord comprises core filaments and an outer sheath filament disposed so as to surround the core filaments, wherein: the core filaments and the outer sheath filament have the same element wire diameter and the same twist pitch; and at least one of the core filaments is a corrugated filament which has a bent section and a non-bent section in the longitudinal direction thereof.

Description

[Technical field]

[0001] The present disclosure relates to a steel cord and a tire. [Background technology]

[0002] Patent Document 1 discloses a metal cord having a core wire and an outer wire arranged to surround the core wire. In the metal cord disclosed in Patent Document 1, the core wire and the outer wire have the same diameter, twisting direction, and twisting pitch, and the core wire is not preformed, while at least some of the outer wires are preformed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] US Patent Application Publication No. 2011 / 0099967 Summary of the Invention

[0004] The steel cord of the present disclosure has a core filament and an outer sheath filament arranged to surround the core filament, The core filament and the outer sheath filament have the same wire diameter and twist pitch, At least one of the core filaments is a wavy filament having a bent portion and a non-bent portion along the longitudinal direction. [Brief description of the drawings]

[0005] [Figure 1] FIG. 1 is a cross-sectional view of a steel cord according to one embodiment of the present disclosure taken along a plane perpendicular to the longitudinal direction. [Diagram 2] FIG. 2 is a cross-sectional view taken along a plane perpendicular to the longitudinal direction of a steel cord having the same structure as that shown in FIG. 1 except that the core filaments do not have wavy filaments. [Diagram 3]FIG. 3 is a cross-sectional view of a steel cord having a 3 / 8 structure according to one embodiment of the present disclosure, taken along a plane perpendicular to the longitudinal direction. [Figure 4] FIG. 4 is a side view of a steel cord according to one embodiment of the present disclosure. [Diagram 5] FIG. 5 is an explanatory diagram of a wavy filament in which bent portions and non-bent portions are repeatedly formed. [Figure 6] FIG. 6 is an explanatory diagram of a method for producing a wavy filament in which bent portions and non-bent portions are repeatedly formed. [Figure 7] FIG. 7 is a cross-sectional view of a tire according to one embodiment of the present disclosure. [Figure 8] FIG. 8 is a diagram showing a schematic diagram of the belt layer. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0006] [Problem that this disclosure aims to solve] As disclosed in Patent Document 1, a steel cord has been known which has a core wire and an outer wire arranged to surround the core wire, and in which the twist pitch of the core wire and the twist pitch of the outer wire are the same. A steel cord in which the twist pitch of the core wire and the twist pitch of the outer wire are the same has excellent productivity because the core wire and the outer wire can be twisted simultaneously.

[0007] However, from the viewpoint of improving the durability of tires, there is a demand for steel cords with high rubber permeability in order to suppress the intrusion of water and the like into the rubber of the tire.

[0008] Therefore, an object of the present disclosure is to provide a steel cord having a high degree of rubber penetration. [Effects of this disclosure] According to the present disclosure, it is possible to provide a steel cord with a high degree of rubber permeation.

[0009] [Description of the embodiments of the present disclosure] First, the embodiments of the present disclosure will be described. In the following description, the same or corresponding elements are denoted by the same reference numerals, and the same description thereof will not be repeated.

[0010] (1) A steel cord according to one embodiment of the present disclosure includes a core filament and an outer sheath filament arranged to surround the core filament, The core filament and the outer sheath filament have the same wire diameter and twist pitch, At least one of the core filaments is a wavy filament having a bent portion and a non-bent portion along the longitudinal direction.

[0011] By making the wire diameter of the core filament the same as that of the outer sheath filament, the same filament can be used as the core filament and the outer sheath filament, which makes it possible to reduce the number of types of filaments to be prepared when manufacturing a steel cord, thereby reducing costs and increasing productivity.

[0012] When the twist pitch of the core filaments and the twist pitch of the outer sheath filaments are the same, the core filaments and the outer sheath filaments can be twisted together to produce a steel cord, thereby improving the productivity of the steel cord.

[0013] However, when the core filaments and the outer sheath filaments have the same wire diameter and twist pitch, the resulting steel cord having a two-layer twist structure has a problem of low rubber penetration.

[0014] Therefore, in a steel cord according to an embodiment of the present disclosure, at least one of the core filaments is a wavy filament, and as a result, the steel cord according to an embodiment of the present disclosure can increase the distance between the outer sheath filaments and increase the rubber penetration degree, compared to a steel cord in which the core filaments do not include a wavy filament.

[0015] (2) The core filament has two of the wavy filaments arranged adjacent to each other, The two wavy filaments may have different wavy pitches.

[0016] When the corrugation pitches of two adjacent core filaments are different, the positions of the bent portions of the two adjacent core filaments in the longitudinal direction can be prevented from being aligned without adjusting the longitudinal positions of the two adjacent core filaments. As a result, the area of ​​the core can be made sufficiently large, and a sufficient gap can be formed between the outer sheath filaments. In addition, the rubber penetration rate can be particularly increased.

[0017] (3) The core filament has two of the wavy filaments arranged adjacent to each other, The two wavy filaments may have different wavy heights.

[0018] By configuring two adjacent wavy filaments to have different corrugation heights, even if the positions of the bends in the longitudinal direction of the adjacent wavy filaments are the same, the area of ​​the core can be increased and a sufficient gap can be formed between the outer sheath filaments, thereby making it possible to particularly increase the degree of rubber penetration. (4) All of the core filaments may be wavy filaments.

[0019] By making all of the core filaments of the steel cord wavy filaments, the distance between the outer sheath filaments can be particularly increased, thereby making it possible to particularly increase the degree of rubber penetration.

[0020] (5) The wavy filament may include portions that oscillate in a plurality of different directions.

[0021] By using a wavy filament including a portion that oscillates in a plurality of different directions as the core filament of the steel cord, even if the corrugation height is low, the distance between the outer sheath filaments can be made sufficient, and the rubber penetration degree of the steel cord can be particularly increased. By using a wavy filament including a portion that oscillates in a plurality of different directions as the core filament of the steel cord, the corrugation height required to achieve the desired rubber penetration degree can be reduced compared to the case of using a wavy filament that oscillates only in one direction. Therefore, the amount of processing required to make the wavy filament is suppressed, and the breaking load of the wavy filament can be increased.

[0022] (6) The core filament may have a brass plating film containing Cu and Zn on its surface.

[0023] Cu stands for copper and Zn stands for zinc.

[0024] By providing the core filament with a brass plating film containing Cu and Zn, when the steel cord is coated with rubber to form a tire, the adhesive strength between the core filament and the rubber is increased, resulting in a tire with particularly excellent durability.

[0025] (7) The brass plating film may further contain one or more elements selected from the group consisting of Co, Ni, and Fe.

[0026] Co stands for cobalt, Ni stands for nickel, and Fe stands for iron.

[0027] If the brass plating film further contains one or more elements selected from Co, Ni, and Fe, the adhesive strength between the core filament and the rubber can be further increased, and the durability of the tire can be further improved.

[0028] (8) It may be of 2 / 7 or 3 / 8 structure.

[0029] By making the steel cord have a 2 / 7 or 3 / 8 structure, the number of outer sheath filaments is close to the upper limit of the allowable number of core filaments, and therefore a steel cord with a high breaking load can be obtained. In addition, in the case of either of the above structures, the outer sheath filaments are arranged around the core filaments at a high density, and conventionally, the rubber penetration rate tends to be low. However, according to the steel cord according to one embodiment of the present disclosure, even if either of the above structures is used, the rubber penetration rate can be increased, and a particularly high effect can be exhibited.

[0030] (9) A tire comprising the steel cord according to any one of (1) to (8).

[0031] The steel cord according to one embodiment of the present disclosure has excellent rubber permeability, and therefore, the inside of the steel cord can be filled with rubber to suppress the penetration of water, etc. Therefore, a tire including such a steel cord can be made to have excellent durability.

[0032] Moreover, the steel cord according to one embodiment of the present disclosure has a flat cross section perpendicular to the longitudinal direction. The thickness of the belt layer can be selected so that the steel cords arranged in a row can be embedded in the rubber, and therefore the thickness of the belt layer can be reduced by making the cross section of the steel cord flat and reducing the thickness. Therefore, by using such a steel cord, the amount of rubber contained in the belt layer can be reduced compared to, for example, a case where a circular steel cord having the same cross-sectional area is used. As a result, the weight of the belt layer can be reduced, and the weight of the tire including the belt layer can also be reduced.

[0033] [Details of the embodiment of the present disclosure] Specific examples of a steel cord and a tire according to one embodiment of the present disclosure (hereinafter, referred to as the present embodiment) will be described below with reference to the drawings. Note that the present invention is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0034] [Steel cord] Hereinafter, the steel cord according to the present embodiment will be described with reference to Figs. (1) Structure of steel cord As shown in FIG. 1, a steel cord 10 according to this embodiment can have a core filament 11 and an outer sheath filament 12 arranged so as to surround the core filament 11.

[0035] That is, the steel cord 10 of this embodiment has a layered structure having a core 111 having a core filament 11, and an outer sheath 121 having an outer sheath filament 12 arranged around the core 111. The layered structure means that the filaments are arranged in layers and include a plurality of layers in a cross section perpendicular to the longitudinal direction of the steel cord. As shown in Fig. 1, the steel cord of this embodiment preferably has a two-layered structure in which the core 111 and the outer sheath 121 are each one layer.

[0036] Hereinafter, when the core filament 11 and the outer sheath filament 12 are referred to collectively without distinction, they may be simply referred to as filaments.

[0037] 1 shows an example of a 2 / 7 structure having two core filaments 11 and seven outer sheath filaments 12, but is not limited to this form. The numbers of the core filaments 11 and the outer sheath filaments 12 can be selected according to the characteristics required of the steel cord, such as the breaking load.

[0038] The steel cord of this embodiment is preferably, for example, the steel cord 10 having a 2 / 7 structure shown in FIG. 1, or the steel cord 30 having a 3 / 8 structure shown in FIG.

[0039] The N / M structure means that the number of core filaments 11 is N, the number of outer sheath filaments 12 is M, and the twist pitch and twist direction of the core filaments 11 and the outer sheath filaments 12 are the same, resulting in a two-layer twist structure. Therefore, the 3 / 8 structure means that there are three core filaments 11 and eight outer sheath filaments 12, as shown in FIG. 3.

[0040] By making the steel cord of this embodiment into a 2 / 7 structure or a 3 / 8 structure, the number of the outer sheath filaments 12 is close to the upper limit allowable for the number of the core filaments 11, and therefore a steel cord with a high breaking load can be obtained. In addition, in the case of either of the above structures, the outer sheath filaments 12 are arranged around the core filaments 11 at a high density, and conventionally, the rubber penetration rate tends to be low. However, according to the steel cord of this embodiment, even if either of the above structures is used, the rubber penetration rate can be increased, and a particularly high effect can be exhibited.

[0041] The cross section perpendicular to the longitudinal direction of the steel cord 10 of this embodiment may have, for example, a flat shape. L The length is not particularly limited, but is preferably, for example, 1.43 mm or more and 1.65 mm or less, and more preferably 1.45 mm or more and 1.60 mm or less.

[0042] The minor axis L of the steel cord 10 of this embodiment in a cross section perpendicular to the longitudinal direction S The length is not particularly limited, but is preferably, for example, 1.30 mm or more and 1.50 mm or less, and more preferably 1.32 mm or more and 1.45 mm or less.

[0043] The length of the major axis and the minor axis of the steel cord of the present embodiment are, for example, in the thickness direction, specifically, the minor axis L S It can also be adjusted by pressing along the direction. (2) Filament (2-1) Wire diameter The wire diameter D of the core filament 11 of the steel cord 10 of this embodiment 11 and the wire diameter D of the outer sheath filament 12 12 It is preferable that the diameter D of the core filament 11 is the same as that of the core filament 11. 11 and the wire diameter D of the outer sheath filament 12 12 By making the filaments the same, the same filaments can be used as the core filaments 11 and the outer sheath filaments 12. This makes it possible to reduce the number of types of filaments to be prepared when manufacturing a steel cord, thereby reducing costs and increasing productivity.

[0044] Core filament 11 wire diameter D 11 , and the wire diameter D of the outer sheath filament 12 12 are not limited, but are preferably 0.30 mm or more and 0.42 mm or less, and more preferably 0.35 mm or more and 0.42 mm or less. 11 , D 12 By making the wire diameter D 0.30 mm or more, the breaking load of the steel cord can be sufficiently increased. 11 , D 12 By making the filament thickness 0.42 mm or less, when a steel cord containing the filament is used in a tire, shock can be sufficiently absorbed and the ride comfort during driving can be improved.

[0045] Core filament 11 wire diameter D 11 and the wire diameter D of the outer sheath filament 12 12 Since each of the filaments has a certain tolerance in manufacturing, the wire diameters of the two filaments can be the same if they are within the tolerance range.

[0046] For example, the diameter D of the core filament 11 11 and the diameter of the outer sheath filament D 12 And, 0.92≦D 11 / D 12If the relationship is ≦1.08, it can be within the tolerance range. Therefore, if the above range is satisfied, the wire diameter D of the core filament 11 and the diameter of the outer sheath filament D 12 can be the same as (2-2) Filament twist pitch In addition, it is preferable that the twist pitch of the core filaments 11 and the twist pitch of the outer sheath filaments 12 are the same.

[0047] When the twist pitch of the core filaments 11 and the twist pitch of the outer sheath filaments 12 are the same, the core filaments 11 and the outer sheath filaments 12 can be twisted together to produce a steel cord, thereby improving the productivity of the steel cord.

[0048] The twist pitch means the length of one twist of the filaments. The length here means the length along the central axis of the steel cord.

[0049] Fig. 4 shows a side view of the steel cord 10 shown in Fig. 1. As also shown in Fig. 1, the steel cord 10 has seven outer sheath filaments 12A to 12G. Therefore, the outer sheath filaments 12A to 12G appear repeatedly in that order on the side surface of the steel cord 10.

[0050] As shown in FIG. 4, on the side of the steel cord 10, the distance between the same outer sheath filaments along the central axis CA, for example, between the outer sheath filaments 12A, is the twist pitch Pt of the outer sheath filaments 12.

[0051] Here, the twist pitch of the outer sheath filaments 12 has been described as an example, but the twist pitch of the core filaments 11 is the same.

[0052] In the steel cord of the present embodiment, the twist pitch of the outer sheath filaments and the core filaments is not particularly limited, but is preferably, for example, 10 mm or more and 30 mm or less, and more preferably 15 mm or more and 25 mm or less.

[0053] There is a certain tolerance in manufacturing between the twist pitch of the core filament 11 and the twist pitch of the outer sheath filament 12. Therefore, within the tolerance range, the twist pitch of both filaments can be the same.

[0054] In addition, it is preferable that the core filaments 11 and the outer sheath filaments 12 are twisted in the same direction. (2-3) Wavy filament By making the wire diameter and twist pitch of the core filament 11 and the outer sheath filament 12 the same as described above, the productivity of the steel cord can be improved. However, when the wire diameter and twist pitch of the core filament 11 and the outer sheath filament 12 are the same, there is a problem that the rubber penetration rate of the obtained steel cord having a two-layer twisted structure is low. From the viewpoint of improving the durability of tires, a steel cord with a high rubber penetration rate has been required to suppress the intrusion of water and the like into the rubber of the tire.

[0055] Therefore, in the steel cord 10 of the present embodiment, at least one of the core filaments 11 is preferably a corrugated filament having a bent portion and a non-bent portion along the longitudinal direction.

[0056] The details of the wavy filament will be described later, but as shown in FIG. 5, the wavy filament 40 has bent portions 41 and non-bent portions 42 repeatedly along the longitudinal direction, and has a shape with a wavy amplitude. For this reason, as shown in FIG. 1, when the core filament 11A of the steel cord 10 is a wavy filament, the position of the core filament 11A changes depending on the cross section when observed in multiple cross sections perpendicular to the longitudinal direction of the steel cord 10. As a result, the area of ​​the region surrounded by dotted line A, which is occupied by the core filament 11A, which is a wavy filament, becomes larger, and the area of ​​the core 111 surrounded by dotted line B including the core filament 11A also becomes larger. And, as the area of ​​the core 111 becomes larger, the distance L between the outer sheath filaments 12A and 12B arranged to surround the core 111 becomes shorter. d can be made longer.

[0057] The same can be said for the steel cord 30 having the 3 / 8 structure shown in FIG.

[0058] For comparison, Fig. 2 shows a cross section perpendicular to the longitudinal direction of a steel cord 20 in which both of the two core filaments 11A, 11B are straight filaments, not corrugated filaments. Comparing the steel cord 10 shown in Fig. 1 with the steel cord 20 shown in Fig. 2, it can be seen that the area of ​​the core 111 surrounded by the dotted line B in the steel cord 10 is larger than that in the steel cord 20. In addition, the distance L between the outer sheath filaments 12A, 12B in the steel cord 10 shown in Fig. 1 is shorter than that in the steel cord 20 shown in Fig. 2. d It can also be seen that the length has increased.

[0059] As described above, by making at least one of the core filaments 11 a wavy filament, the distance between the outer sheath filaments 12A, 12B can be increased and the degree of rubber penetration can be increased compared to when the core filament 11 does not include a wavy filament.

[0060] The number of wavy filaments in the steel cord of this embodiment is not particularly limited, and as described above, at least one of the core filaments 11 can be a wavy filament. All of the core filaments 11 in the steel cord of this embodiment can also be wavy filaments. By making all of the core filaments 11 in the steel cord of this embodiment wavy filaments, the distance between the outer sheath filaments 12 in particular can be increased, and the rubber penetration rate can be particularly increased.

[0061] When the core filament 11 has two wavy filaments arranged adjacent to each other, the two wavy filaments preferably have different corrugation pitches P, which will be described later. That is, when a plurality of filaments among the core filament 11 are wavy filaments and at least some of the wavy filaments are arranged adjacent to each other, it is preferable that the corrugation pitches P be different between adjacent wavy filaments.

[0062] When two adjacent wavy filaments have the same wavy pitch P, the positions of the bent portions of the adjacent wavy filaments in the longitudinal direction may coincide unless the positions of the adjacent wavy filaments in the longitudinal direction are adjusted. If the positions of the bent portions of the adjacent wavy filaments in the longitudinal direction coincide, the effect of increasing the area of ​​the core 111 is reduced, and the effect of increasing the rubber penetration rate may be suppressed.

[0063] On the other hand, when the corrugation pitches P of two adjacent wavy filaments are different, the positions of the bent portions of the two adjacent wavy filaments in the longitudinal direction can be prevented from coinciding with each other without adjusting the positions of the two adjacent wavy filaments in the longitudinal direction. As a result, the area of ​​the core 111 can be made sufficiently large, and a sufficient gap can be formed between the outer sheath filaments 12. In addition, the rubber penetration rate can be particularly increased.

[0064] The difference in the corrugation pitch P between two adjacent corrugated filaments is not particularly limited, but is preferably 1.5 mm or more, and more preferably 1.7 mm or more. By making the difference in the corrugation pitch P between adjacent corrugated filaments 1.5 mm or more, it is possible to prevent the positions of the bent portions in the longitudinal direction of adjacent corrugated filaments from coinciding with each other even if the longitudinal positions of the corrugated filaments are not adjusted during the manufacture of the steel cord. This allows the area of ​​the core 111 to be particularly large, and the rubber penetration rate to be particularly increased.

[0065] However, since it may be difficult to make the difference in the corrugation pitch P of adjacent wavy filaments greater than 5 mm, it is preferable that the difference in the corrugation pitch P of adjacent wavy filaments be 5 mm or less, and more preferably 4 mm or less.

[0066] Furthermore, when the wavy filament has two adjacently arranged wavy filaments, the two wavy filaments preferably have different corrugation heights H, which will be described later. That is, when a plurality of filaments among the core filaments 11 are wavy filaments and at least some of the wavy filaments are arranged adjacent to each other, it is preferable that the corrugation heights H be different between the adjacent wavy filaments.

[0067] By configuring the corrugation heights H of two adjacent corrugated filaments to be different, even if the positions of the bent portions in the longitudinal direction of the adjacent corrugated filaments are the same, the area of ​​the core 111 can be increased and a sufficient gap can be formed between the outer sheath filaments. In addition, the rubber penetration rate can be particularly increased.

[0068] The difference in corrugation height H between adjacent wavy filaments is not particularly limited, but is preferably 20% or more, more preferably 25% or more, of the wire diameter. By making the difference in corrugation height H between adjacent wavy filaments 20% or more of the wire diameter, the area of ​​the core 111 can be increased and the rubber penetration can be increased even if the positions of the bends in the longitudinal direction of adjacent wavy filaments are the same.

[0069] Although there is no particular upper limit to the difference in the corrugation height H between adjacent wavy filaments, the difference in the corrugation height H between adjacent wavy filaments is preferably 150% or less of the wire diameter, and more preferably 100% or less. By making the difference in the corrugation height H between adjacent wavy filaments 150% or less of the wire diameter, it is possible to prevent the outer diameter of the steel cord from becoming excessively large.

[0070] In the steel cord of the present embodiment, straight filaments without bends, rather than wavy filaments, can be used as the outer sheath filaments 12. That is, only one or more selected from the core filaments 11 can be wavy filaments, and the other filaments including the outer sheath filaments 12 can be straight filaments.

[0071] According to the study by the inventors of the present invention, when a wavy filament is used for the core filament 11, the number of wavy filaments required to achieve a desired rubber penetration degree can be reduced compared to when a wavy filament is used for the outer sheath filament 12. Therefore, the number of wavy filaments required when manufacturing a steel cord can be reduced, and the productivity of the steel cord can be improved.

[0072] In addition, when the core filament 11 is a wavy filament, the major axis L of the steel cord at a desired rubber penetration degree is smaller than when the outer sheath filament 12 is a wavy filament. L Or, minor axis L S The steel cord can be applied to, for example, the belt layer of a tire described later, and the thickness of the belt layer can be selected so that the steel cord can be embedded in the rubber of the belt layer. Specifically, for example, the thickness of the belt layer can be determined by adding a predetermined value that is determined in advance so that the steel cord can be embedded to the thickness of the steel cord. Therefore, the major axis L of the steel cord can be selected so that the thickness of the belt layer can be selected so that ... L Or, minor axis L SBy suppressing the thickness of the belt layer, the amount of rubber contained in the belt layer can be suppressed. As a result, the weight of the tire including the belt layer can be reduced, and the fuel efficiency of the vehicle equipped with the tire can be improved.

[0073] The details of the wavy filament will be described with reference to Figs. 5 and 6.

[0074] 5 shows an example of the configuration of the wavy filament 40. As described above, the wavy filament 40 has bent portions 41 and non-bent portions 42 alternately and repeatedly along the longitudinal direction.

[0075] FIG. 5 shows an example in which the bent portion 41 is bent at an angle close to 90 degrees, but the present invention is not limited to this form, and the bent portion 41 may be bent at an angle less than 90 degrees or more than 90 degrees.

[0076] The wavy filament can be formed, for example, as shown in Fig. 6, by arranging a plurality of preforms 51 and passing a straight filament 52 to be the wavy filament between the plurality of preforms 51 in the direction of the block arrow in the figure. By changing the arrangement, size, and shape of the preforms 51, the shape of the bent portion, the length of the non-bent portion, etc. can be selected. The preform 51 can have, for example, a pin type (cylindrical type) or a gear type shape.

[0077] The specific wave shape of the wavy filament is not particularly limited, however, the wave height H of the wavy filament is preferably 200% to 350% of the wire diameter of the wavy filament, and more preferably 220% to 320%.

[0078] The corrugation height H means the height from the plane S to the bent portion 41B on the side farther from the plane S when the corrugated filament 40 is placed on the plane S as shown in Fig. 5. When evaluating the corrugation height H, the corrugated filament is placed on the plane S so that the direction of the amplitude formed by the repetition of bent and non-bent portions in the part to be evaluated is perpendicular to the plane S.

[0079] By making the corrugation height H 200% or more of the wire diameter, when the steel cord is used as a core filament of a steel cord, a sufficient gap is formed between the outer sheath filaments, and the rubber penetration rate of the steel cord can be particularly increased.

[0080] By setting the corrugation height H to 350% or less of the wire diameter, the outer diameter of the steel cord can be prevented from becoming excessively large. In addition, by setting the corrugation height H to 350% or less of the wire diameter, the occurrence of flaring, which occurs when the filaments are untwisted and expanded when the steel cord is cut, can be prevented, which is preferable.

[0081] In the wavy filament, the corrugation pitch P, which is the repeating pitch between the bent portions and the non-bent portions, is not particularly limited, but is preferably, for example, 2.0 mm or more and 30.0 mm or less, and more preferably 3.0 mm or more and 15.0 mm or less.

[0082] The corrugation pitch means the distance between bent portions of the same shape, and refers to the length of the steel cord from a reference bent portion to the next adjacent bent portion. Therefore, in the example shown in Fig. 5, the corrugation pitch P means, for example, the distance from bent portion 41A to the next adjacent bent portion 41C.

[0083] By setting the corrugation pitch P to 2.0 mm or more, it is easy to form bent and non-bent parts in the filament and to control it accurately. Also, by setting the corrugation pitch to 30.0 mm or less, it is possible to manufacture the bent and non-bent parts with a relatively simple device, and the manufacturing cost can be suppressed.

[0084] In Fig. 5, an example of a wavy filament that oscillates only in one direction perpendicular to the X-axis direction, which is the longitudinal direction, specifically in the Y-axis direction, is shown, but the wavy filament of the steel cord of this embodiment is not limited to this form. The wavy filament used in the steel cord of this embodiment can be, for example, a wavy filament including a portion that oscillates along multiple different directions, specifically, a wavy filament including a portion that oscillates in multiple directions in a plane perpendicular to the longitudinal direction. Oscillating in multiple directions means including not only a portion that oscillates in, for example, the Y-axis direction perpendicular to the X-axis, which is the longitudinal direction of the wavy filament 40 in Fig. 5, but also a portion that oscillates in the Z-axis direction.

[0085] By using a wavy filament including a portion that oscillates in a plurality of different directions as the core filament of the steel cord, even if the corrugation height H is low, the distance between the outer sheath filaments 12 is sufficient, and the rubber penetration degree of the steel cord can be particularly increased. In addition, by using a wavy filament including a portion that oscillates in a plurality of different directions as the core filament of the steel cord, the corrugation height required to achieve the desired rubber penetration degree can be reduced compared to the case of using a wavy filament that oscillates only in one direction. Therefore, the amount of processing required to make the wavy filament is suppressed, and the breaking load of the wavy filament can be increased. (2-4) Filament material The material of the core filament of the steel cord of the present embodiment is not particularly limited, and may be, for example, a steel wire. The core filament of the steel cord of the present embodiment may also have a steel wire 13 and a plating film 14 disposed on the surface of the steel wire 13, as shown in, for example, the core filament 11B of FIG.

[0086] As the steel wire 13, a high carbon steel wire can be suitably used.

[0087] The plating film 14 is preferably a brass plating film having, for example, copper (Cu) and zinc (Zn) as metal components. The brass plating film may be composed of only Cu and Zn, but may also contain metal components other than Cu and Zn. The brass plating film may also further contain, for example, one or more elements selected from the group consisting of cobalt (Co), nickel (Ni), and iron (Fe) as metal components.

[0088] For this reason, like the core filament 11B shown in FIG. 1, the core filament of the steel cord of this embodiment can have a steel wire 13 and a plating film 14, which is a brass plating film containing Cu and Zn, arranged on the surface of the steel wire 13. The plating film 14 can further contain one or more elements selected from Co, Ni, and Fe. In FIG. 1, the boundary between the steel wire 13 and the plating film 14 is shown by a dotted line, but the composition may change continuously from the surface of the steel wire 13 toward the plating film 14, and the boundary between the two may not be clear. In FIG. 1, the plating film 14 is shown only on one core filament 11B, but all of the core filaments 11 of the steel cord 10 may have the plating film 14 on the surface of the steel wire 13 in the same way. In addition, the outer sheath filament 12 may also have the plating film 14 on the surface of the steel wire 13 in the same way. The same applies to the steel cord 30 of another configuration example shown in FIG. 3.

[0089] By providing the core filament with a brass plating film containing Cu and Zn, when the steel cord is coated with rubber to form a tire, the adhesive strength between the core filament and the rubber is increased, resulting in a tire with particularly excellent durability. Furthermore, by further including one or more elements selected from Co, Ni, and Fe in the brass plating film, the adhesive strength between the core filament and the rubber can be further increased, resulting in further improved durability of the tire.

[0090] 〔tire〕 The tire according to this embodiment will be described with reference to FIGS.

[0091] The tire of this embodiment may include the steel cord described above.

[0092] Fig. 7 shows a cross-sectional view of a tire 60 according to this embodiment taken along a plane perpendicular to the circumferential direction. Although Fig. 7 shows only a portion to the left of the center line (CL), the same structure extends to the right of the center line (CL) with the CL as an axis of symmetry.

[0093] As shown in FIG. 7, a tire 60 includes a tread portion 61, a sidewall portion 62, and a bead portion 63.

[0094] The tread portion 61 is a portion that comes into contact with the road surface. The bead portions 63 are provided on the inner diameter side of the tire 60 from the tread portion 61. The bead portions 63 are portions that come into contact with the rim of a vehicle wheel. The sidewall portions 62 connect the tread portion 61 and the bead portions 63. When the tread portion 61 receives an impact from the road surface, the sidewall portions 62 elastically deform to absorb the impact.

[0095] The tire 60 includes an inner liner 64 , a carcass 65 , a belt layer 66 , and a bead wire 67 .

[0096] The inner liner 64 is made of rubber and seals the space between the tire 60 and the wheel.

[0097] The carcass 65 forms the framework of the tire 60. The carcass 65 is made of organic fibers such as polyester, nylon, or rayon, or steel cords, and rubber.

[0098] The bead wire 67 is provided in the bead portion 63. The bead wire 67 receives a tensile force acting on the carcass.

[0099] The belt layer 66 tightens the carcass 65 to increase the rigidity of the tread portion 61. In the example shown in FIG.

[0100] Fig. 8 is a diagram showing a schematic diagram of one belt layer 66. Fig. 8 shows a cross-sectional view of the belt layer 66 taken along a plane perpendicular to the longitudinal direction of the belt layer 66, i.e., the circumferential direction of the tire 60.

[0101] As shown in Fig. 8, the belt layer 66 has a plurality of steel cords 71 ​​and rubber 72. The plurality of steel cords 71 ​​are arranged in parallel in a row. The steel cords 71 ​​may be the steel cords described above. The rubber 72 covers the steel cords 71, and the entire circumference of each steel cord 71 is covered with the rubber 72. The steel cords 71 ​​are embedded in the rubber 72.

[0102] The above-mentioned steel cord has excellent rubber permeability, and therefore, the inside of the steel cord can be filled with rubber to suppress the penetration of water, etc. Therefore, the tire of the present embodiment including the above-mentioned steel cord can be made to have excellent durability.

[0103] In addition, the above-mentioned steel cord has a flat cross section perpendicular to the longitudinal direction. The thickness of the belt layer can be selected so that the steel cords arranged in a row can be embedded in the rubber, so that the thickness of the belt layer can be reduced by making the cross section of the steel cord flat and reducing the thickness. Therefore, by using the above-mentioned steel cord, the amount of rubber contained in the belt layer can be reduced compared to, for example, a case in which a circular steel cord having the same cross-sectional area is used. As a result, the weight of the belt layer can be reduced, and the weight of the tire including the belt layer can also be reduced.

[0104] Although the embodiments have been described in detail above, the present invention is not limited to the specific embodiments, and various modifications and changes are possible within the scope of the claims. EXAMPLES

[0105] The present invention will be described below with reference to specific examples, but is not limited to these examples. (Evaluation method) (1) Evaluation method for steel cord The evaluation methods for the steel cords produced in the following experimental examples will be described. (1-1) Wire diameter The diameter of the filament was measured using a micrometer. (1-2) Cable outer diameter The steel cord to be evaluated was embedded in a transparent resin, and a sample was cut out so that a surface (cross section) perpendicular to the longitudinal direction of the steel cord was exposed.

[0106] Then, the minor axis L of the steel cord in the cross section is measured using a projector. S , and the major axis L L was measured. (1-3) Twist pitch The measurement was carried out by the tracing method of JIS G 3510 (1992). Specifically, a traceable thin paper was placed on the outer peripheral surface of the produced steel cord, and the trace of twisting of the outer sheath filaments was copied by rubbing the paper with a pencil. Then, from the obtained trace of twisting of the outer sheath filaments, the length of 5 pitches of the outer sheath filaments along the central axis of the steel cord was measured with a ruler, and the value divided by 5 was determined as the twist pitch of the outer sheath filaments.

[0107] The outer sheath filaments were untwisted to expose the core filaments, and the twist pitch of the core filaments was measured in the same manner. However, since the twist pitch of the outer sheath filaments and the twist pitch of the core filaments were the same in all of the following experimental examples, only one of the values ​​is shown as the evaluation result. (1-4) Rubber penetration First, the manufactured steel cords were arranged on a rubber sheet for tires at equal intervals, specifically, so that the distance between the steel cords was twice the length of the long axis of the steel cords, and then a rubber sheet was placed on top of the sheet. This resulted in a laminate of the rubber sheet and the steel cords, each having a rectangular parallelepiped shape and a total thickness of five times the short axis of the steel cords. The laminate of the rubber sheet and the steel cords was then vulcanized at 160°C for 18 minutes.

[0108] After cooling naturally, the steel cord was removed from the resulting steel cord / rubber composite with a cutter knife.

[0109] Then, two adjacent outer sheath filaments were removed from the taken-out steel cord. The ratio of the length of the rubber-covered portion to the observation length of 100 mm along the center line in the width direction of the region exposed by removing the two adjacent outer sheath filaments was calculated as a percentage to be the rubber penetration degree.

[0110] A higher rubber penetration value indicates better rubber penetration, and a rubber penetration value of 50% or more indicates sufficient performance for practical use.

[0111] The manufacturing conditions of the steel cord in each Experimental Example are explained below. Experimental Examples 1 to 19 are examples, and Experimental Examples 20 to 22 are comparative examples. [Experimental Example 1] (Steel cord) The steel cord was produced by the following procedure.

[0112] A copper layer and a zinc layer were formed on the surface of a steel filament by plating. The copper layer was plated using copper pyrophosphate as the plating solution at a current density of 22 A / dm 2 The plating time was 14 seconds. The zinc layer was formed using zinc sulfate as the plating solution and a current density of 20 A / dm 2 The treatment time was set to 7 seconds.

[0113] After the plating process, the plate was heat-treated by heating at 600°C for 9 seconds in an air atmosphere to diffuse the metal components and form a plating film.

[0114] The obtained filament base material on which the plating film was formed was subjected to wire drawing to obtain a filament having a wire diameter of 0.38 mm and a brass plating film on the surface of the steel wire.

[0115] The obtained filaments having the plating film were twisted together by a twisting machine to produce a steel cord of Experimental Example 1 having the 2 / 7 structure shown in Fig. 1. The 2 / 7 structure has already been explained, so an explanation will be omitted here. Note that filaments having the above-mentioned brass plating film and having the same wire diameter were used as the core filament 11 and the outer sheath filament 12, and the twist pitch and twist direction were also the same for the core filament 11 and the outer sheath filament 12.

[0116] When manufacturing the steel cord of the above-mentioned Experimental Example 1, one of the two core filaments 11 was a corrugated filament. The corrugated filament was a filament in which bent and non-bent portions were repeatedly formed along the longitudinal direction so that the corrugation height H was 0.95 mm (250% of the wire diameter) and the corrugation pitch P between the bent and non-bent portions was 4.3 mm. The remaining filament was a straight filament with no bent portions. Note that, in the other experimental examples described below, the filaments that were not corrugated among the core filaments 11 were straight filaments with no bent portions. In addition, all of the outer sheath filaments 12 were straight filaments with no bent portions.

[0117] The wavy filament used in this experimental example oscillates in one direction, like the wavy filament 40 shown in Fig. 5. In Table 1, the wavy filament oscillating in one direction used in this experimental example is referred to as "two-dimensional," and the wavy filament including portions oscillating in multiple different directions used in experimental examples 13 to 15 and 19 described below is referred to as "three-dimensional."

[0118] The rubber penetration rate was evaluated for the steel cord of Experimental Example 1. The results are shown in Table 1. [Experimental Examples 2 to 8] Steel cords were produced in the same manner as in Experimental Example 1, except that the corrugation pitch P and corrugation height H of the corrugated filaments were set to the values ​​shown in Table 1, and evaluations were carried out.

[0119] In each of the experimental examples, a steel cord having a 2 / 7 structure was manufactured, and one of the core filaments 11 was a wavy filament.

[0120] The evaluation results are shown in Table 1. [Experimental Examples 9 and 10] A steel cord was manufactured and evaluated in the same manner as in Experimental Example 1, except that both of the two core filaments were wavy filaments and the corrugation pitch P and corrugation height H of the wavy filaments were set to the values ​​shown in Table 1.

[0121] In this experimental example, a steel cord having a 2 / 7 structure was also produced.

[0122] In Experimental Example 9, the two wavy filaments each had a wavy height H of 0.95 mm, and the wavy pitches were 4.3 mm and 6.2 mm, respectively.

[0123] In Experimental Example 10, the two wavy filaments each had a wavy height H of 0.95 mm, and the wavy pitches were 4.3 mm and 8.3 mm, respectively.

[0124] The evaluation results are shown in Table 1. [Experimental Example 11] A steel cord was manufactured and evaluated in the same manner as in Experimental Example 1, except that both of the two core filaments were wavy filaments and the corrugation pitch P and corrugation height H of the wavy filaments were set to the values ​​shown in Table 1.

[0125] When twisting the filaments together, the positions of the bent parts of the two core filaments in the longitudinal direction were adjusted to be offset during production.

[0126] In this experimental example, a steel cord having a 2 / 7 structure was also produced.

[0127] The two wavy filaments each had a wavy height H of 0.95 mm and a wavy pitch of 4.3 mm. [Experimental Example 12] A steel cord was manufactured and evaluated in the same manner as in Experimental Example 1, except that both of the two core filaments were wavy filaments and the corrugation pitch P and corrugation height H of the wavy filaments were set to the values ​​shown in Table 1.

[0128] In this experimental example, a steel cord having a 2 / 7 structure was also produced.

[0129] The two wavy filaments had a wavy height H of 0.95 mm and 1.06 mm, respectively, and the wavy pitch was 4.3 mm for both.

[0130] The evaluation results are shown in Table 1. [Experimental Example 13] The corrugated filaments used had portions that oscillated in a plurality of different directions, and the corrugation pitch P and corrugation height H were set to the values ​​shown in Table 1. A steel cord was produced and evaluated in the same manner as in Experimental Example 1 except for the above points.

[0131] A steel cord having a 2 / 7 structure was produced, and one of the core filaments 11 was a wavy filament.

[0132] The evaluation results are shown in Table 1. [Experimental Examples 14 and 15] Both of the two core filaments were wavy filaments. The two wavy filaments used were wavy filaments including portions that oscillate along a plurality of different directions, and the corrugation pitch P and corrugation height H were set to the values ​​shown in Table 1. A steel cord was produced and evaluated in the same manner as in Experimental Example 1 except for the above points.

[0133] In this experimental example, a steel cord having a 2 / 7 structure was also produced.

[0134] In Experimental Example 14, the two wavy filaments each had a wavy height H of 1.06 mm and a wavy pitch P of 4.3 mm.

[0135] In Experimental Example 15, both of the two wavy filaments had a wavy height H of 0.85 mm and a wavy pitch P of 4.3 mm.

[0136] The evaluation results are shown in Table 1. [Experimental Example 16] A steel cord having the 3 / 8 structure shown in Fig. 3 was manufactured using the filaments having the brass plating film produced in Experimental Example 1. The 3 / 8 structure has already been explained, so an explanation will be omitted here. The core filament 11 and the outer sheath filament 12 had the same wire diameter, and filaments having the brass plating film were used, and the twist pitch and twist direction of the core filament 11 and the outer sheath filament 12 were also the same.

[0137] When manufacturing the steel cord, one of the three filaments of the core filament 11 was a corrugated filament. The corrugated filament was a filament in which bent and non-bent portions were repeatedly formed along the longitudinal direction so that the corrugation height H was 0.95 mm (250% of the wire diameter) and the corrugation pitch P between the bent and non-bent portions was 4.3 mm. The remaining two filaments were straight filaments with no bends. In addition, the outer sheath filaments 12 were all straight filaments with no bends.

[0138] The produced steel cord was evaluated for rubber penetration, and the results are shown in Table 1. [Experimental Examples 17 and 18] In Experimental Example 17, two of the three core filaments 11 were wavy filaments.

[0139] In Experimental Example 18, all of the three core filaments 11, i.e., all three filaments, were wavy filaments.

[0140] In Experimental Example 17, the two wavy filaments each had a wavy height H of 0.95 mm, and the wavy pitches were 4.3 mm and 6.2 mm, respectively.

[0141] In Experimental Example 18, the three wavy filaments all had a wavy height H of 0.95 mm, and the wavy pitches were 4.3 mm, 6.2 mm, and 8.1 mm, respectively.

[0142] Except for the above points, a steel cord was produced in the same manner as in Experimental Example 16, and was evaluated.

[0143] In each of the experimental examples, a steel cord having a 3 / 8 structure was manufactured.

[0144] The evaluation results are shown in Table 1. [Experimental Example 19] Of the three core filaments 11, one core filament was a corrugated filament. The corrugated filament included a portion that oscillates along a plurality of different directions, and the corrugation pitch P and corrugation height H were set to the values ​​shown in Table 1. Specifically, the corrugation height H was set to 0.95 mm, and the corrugation pitch P was set to 4.3 mm.

[0145] Except for the above points, a steel cord was produced in the same manner as in Experimental Example 16, and was evaluated.

[0146] In this experimental example, a steel cord having a 3 / 8 structure was also produced.

[0147] The evaluation results are shown in Table 1. [Experimental Example 20] The four outer sheath filaments were wavy filaments, and the corrugation pitch P and corrugation height H of the wavy filaments were set to the values ​​shown in Table 1. The wavy filaments and straight filaments not forming any bends were alternately arranged along the circumferential direction of the core 111. All of the core filaments 11 were straight filaments not forming any bends. A steel cord was manufactured and evaluated in the same manner as in Experimental Example 1, except for the above points.

[0148] In this experimental example, a steel cord having a 2 / 7 structure was manufactured.

[0149] The evaluation results are shown in Table 1. [Experimental Example 21] As the outer sheath filaments and the core filaments, straight filaments not forming any bent portions were used. In other words, no corrugated filaments were used, and a steel cord 20 having the structure shown in Fig. 2 was produced. Except for the above points, a steel cord was produced in the same manner as in Experimental Example 1, and evaluation was performed.

[0150] In this experimental example, a steel cord having a 2 / 7 structure was also produced. [Experimental Example 22] As the outer sheath filaments and the core filaments, straight filaments not forming any bent portions were used. A steel cord was produced in the same manner as in Experimental Example 16 except for the above points, and was evaluated.

[0151] In this experimental example, a steel cord having a 3 / 8 structure was manufactured.

[0152] The evaluation results are shown in Table 1.

[0153] [Table 1] According to the results shown in Table 1, in Experimental Examples 1 to 19, in which at least one of the core filaments was a wavy filament, the rubber penetration rate was 50% or more, confirming that steel cords with excellent rubber penetration rate were obtained.

[0154] In the steel cord of Example 20, the four outer filaments were wavy filaments, and therefore the rubber penetration rate was 50% or more. However, when comparing Example 20 with Example 4, although the rubber penetration rate was the same, it was confirmed that Example 20 required a larger number of wavy filaments (4) and was inferior in productivity to Example 4.

[0155] It was also confirmed that the steel cord of Example 20 had a larger outer cord diameter than the steel cords of the other examples.

[0156] It was confirmed that the steel cords of Experimental Examples 21 and 22, which do not contain wavy filaments, have significantly low rubber penetration rates of 40% and 45%, respectively. [Explanation of symbols]

[0157] 10, 20, 30 Steel cord 11, 11A, 11B core filament 111 cores 12, 12A~12G outer sheath filament 121 Outer sheath 13 Steel Wire 14 Plating film A, B dotted lines L L Major Diameter L S Short diameter D 11 , D 12 Wire diameter L d distance Pt twist pitch CA center axis 40 Wavy Filament 41, 41A, 41B, 41C bent part 42 Non-bending part H Wave height P Wave pitch S plane 51 Preform 52 Filament 60 Tires 61 Tread 62 Sidewall 63 Bead section 64 Inner Liner 65 Carcass 66 Belt Layer 67 Bead wire 71 Steel Cord 72 Rubber CL Center Line

Claims

1. A core filament and an outer sheath filament arranged to surround the core filament, The core filament and the outer sheath filament have the same wire diameter and twist pitch, At least one of the core filaments is a wavy filament having a bent portion and a non-bent portion along the longitudinal direction, The core filament has two of the wavy filaments arranged adjacent to each other, The two wavy filaments are steel cords having different wavy pitches.

2. A core filament and an outer sheath filament arranged to surround the core filament, The core filament and the outer sheath filament have the same wire diameter and twist pitch, At least one of the core filaments is a wavy filament having a bent portion and a non-bent portion along the longitudinal direction, The core filament has two of the wavy filaments arranged adjacent to each other, The two corrugated filaments are steel cords having different corrugation heights.

3. A core filament and an outer sheath filament arranged to surround the core filament, The core filament and the outer sheath filament have the same wire diameter and twist pitch, At least one of the core filaments is a wavy filament having a bent portion and a non-bent portion along the longitudinal direction, The steel cord includes a portion in which the wavy filament oscillates along a plurality of different directions.

4. The steel cord according to any one of claims 1 to 3, wherein all of the core filaments are the wavy filaments.

5. The steel cord according to any one of claims 1 to 4, wherein the core filament has a surface having a brass plating film containing Cu and Zn.

6. The steel cord according to claim 5, wherein the brass plating film further contains one or more elements selected from the group consisting of Co, Ni, and Fe.

7. The steel cord according to any one of claims 1 to 6, which has a 2 / 7 construction or a 3 / 8 construction.

8. A tire comprising the steel cord according to any one of claims 1 to 7.

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