Wire rope

Abstract

To provide a wire rope having excellent elongation resistance and flexural fatigue resistance even if a rope diameter is small.SOLUTION: A wire rope 1 of the invention has a double twisted structure constituted by twisting a plurality of strands 2B around one strand 2A. A strand 2 comprises: a core material 21 formed by twisting a plurality of element wires 21a, 21b; a first layer 22 formed by twisting the plurality of element wires 22a around the core material 21; and a second layer 23 formed by twisting the plurality of element wires 23a, 23b around the first layer 22. The plurality of element wires 23a, 23b of the second layer 23 are twisted in parallel with the plurality of element wires 22a of the first layer 22.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a wire rope. [Background technology]

[0002] For example, Patent Document 1 discloses multi-degree-of-freedom forceps as a medical instrument for performing medical procedures inside the human body. In the multi-degree-of-freedom forceps of Patent Document 1, a wire rope is used to transmit the operating force of an operating section to the forceps pieces, which are the operating section. The wire rope is routed between the operating section and the operating section of the multi-degree-of-freedom forceps via a pulley, which is a direction changing member. The forceps pieces are configured to open and close by the operating force transmitted by the wire rope, and to grasp an object of medical procedure.

[0003] In various applications where a large space for wiring the wire rope cannot be secured between the operating unit and the actuating unit, such as the above-mentioned medical instruments such as the multi-degree-of-freedom forceps of Patent Document 1, a large space for wiring the wire rope cannot be secured between the operating unit and the actuating unit. Therefore, a wire rope used in an application where a large space for wiring the wire rope cannot be secured must have an extremely small rope diameter, compared to an automobile wire rope used for, for example, an automobile parking brake. In various applications where a large space for wiring the wire rope cannot be secured, such as the above-mentioned medical instruments, not only is the wire rope required to have a small rope diameter, but it is also required to have elongation resistance and bending fatigue durability.

[0004] For example, in a medical instrument such as the multi-degree-of-freedom forceps of Patent Document 1, the operating force of the operating part, such as the gripping force of the forceps pieces, must be kept constant for a long period of time. Therefore, the wire rope is required to maintain stable operating force transmission (operating force responsiveness) with high accuracy for a long period of time. Generally, a wire rope will elongate slightly when subjected to a load in the axial direction of the wire rope. In order to achieve stable operating force transmission with high accuracy for a long period of time, it is necessary to keep this elongation as small as possible, and the wire rope is required to have excellent elongation resistance.

[0005] In addition, the pulley, which is a direction-changing member provided near the operating part, may also be formed in an extremely small size, for example, with a radius of curvature of several mm. The wire rope wound around the pulley formed in a small size is required to have excellent bending properties and excellent fatigue durability in a usage environment where the wire rope is bent with a small radius of curvature. In particular, since the wire rope needs to be routed in a very narrow device, it may be arranged at an angle to the extension direction of the pulley groove, and may come into contact with or ride over the side of the pulley groove. Therefore, the wire rope is required to have even higher bending fatigue durability than applications such as automobiles, in which the wire rope can be arranged parallel to the extension direction of the pulley groove. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2021-58403 [Patent Document 2] JP 2005-13296 A Summary of the Invention [Problem to be solved by the invention]

[0007] As a wire rope used in the above-mentioned medical instruments, for example, Patent Document 2 discloses a wire rope with a single-stranded structure with improved operation force transmission of rotational operation force. The wire rope disclosed in Patent Document 2 has excellent operation force transmission regarding rotational force, but high bending fatigue durability cannot be expected due to its single-stranded structure. In addition, in the field of wire ropes for automobiles, many attempts have been made to improve bending fatigue durability, but compared with the rope diameter of such wire ropes for automobiles and the pulley diameter of the pulley around which the wire rope is wound, the rope diameter and pulley diameter required for applications in which a large space for wiring the wire rope cannot be secured, such as medical instruments, are very small. For this reason, even if it is the same wire rope, the design of a wire rope for automobiles cannot be simply adopted for a wire rope used in an application in which a large space for wiring the wire rope cannot be secured.

[0008] An object of the present invention is to provide a wire rope which has excellent resistance to elongation and excellent resistance to bending fatigue even when the rope diameter is small. [Means for solving the problem]

[0009] The wire rope of the present invention is a wire rope having a multi-stranded structure formed by twisting multiple strands together into one strand, the strand comprising a core material formed of multiple strands twisted together, a first layer formed by twisting multiple strands together around the core material, and a second layer formed by twisting multiple strands together around the first layer, the multiple strands of the second layer being twisted in a parallel lay to the multiple strands of the first layer. Effect of the Invention

[0010] According to the present invention, it is possible to provide a wire rope that has excellent elongation resistance and excellent flex fatigue resistance even when the rope diameter is small. [Brief description of the drawings]

[0011] [Figure 1] 1 is a schematic perspective view of a medical instrument in which a wire rope according to an embodiment of the present invention is used. [Diagram 2] 1 is a cross-sectional view of a wire rope according to a first embodiment of the present invention. [Diagram 3] FIG. 4 is a cross-sectional view of a wire rope according to a second embodiment of the present invention. [Figure 4] FIG. 1 is a schematic diagram of a breaking load testing machine for evaluating the breaking load of a wire rope. [Diagram 5] FIG. 1 is a schematic diagram of a permanent elongation tester for evaluating the permanent elongation of a wire rope. [Figure 6] FIG. 2 is a schematic diagram of a flexural fatigue durability tester for evaluating the flexural fatigue durability of a wire rope. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, a wire rope according to a first embodiment and a second embodiment of the present invention will be described with reference to the attached drawings. However, each of the embodiments shown below is merely an example, and the wire rope of the present invention is not limited to the following embodiments. In addition, when describing matters common to the first embodiment and the second embodiment in this specification, the first embodiment and the second embodiment will be collectively referred to as the present embodiment. Furthermore, elements having the same function in the wire rope according to the first embodiment and the second embodiment will be described with the same reference numerals.

[0013] The wire rope 1 has one end and the other end, and is a long, thin member extending between the one end and the other end. The wire rope 1 can be used, for example, to be arranged between an operating unit and an actuation unit located away from the operating unit, and to transmit the operating force of the operating unit to the actuation unit to operate the actuation unit. In particular, the wire rope 1 of this embodiment has excellent bending fatigue durability as described later, and can be used as an operating wire rope that is wound around a direction-changing member having a curvature radius of less than 2.0 mm in the arrangement path between the operating unit and the actuation unit, and is particularly usable as an operating wire rope that is wound around a plurality of direction-changing members having a curvature radius of less than 2.0 mm and arranged in an S-shape. For example, as shown in FIG. 1, the wire rope 1 can be used as an operating wire rope that is arranged between an operating unit MD1 and an actuation unit MD2 of the medical instrument MD via a direction-changing member MD3 in a medical instrument MD such as forceps or a robot hand that is inserted into the human body to perform a medical procedure inside the human body. However, the wire rope 1 is not limited to medical devices MD, and can also be applied to other applications where a large space cannot be secured for routing the wire rope, and other applications where a large space can be secured for routing the wire rope.

[0014] 2 and 3, the wire rope 1 has a multi-twisted structure in which a plurality of side strands 2B are twisted around one core strand 2A (hereinafter, the core strand 2A and the side strands 2B are also collectively referred to as "strands 2"). In this embodiment, the wire rope 1 has a multi-twisted structure in which six side strands 2B are twisted around one core strand 2A. However, as long as the wire rope has a multi-twisted structure, the number of side strands twisted around one core strand is not particularly limited and can be changed as appropriate depending on the application in which the wire rope is used.

[0015] In this embodiment, the wire rope 1 has a structure in which a plurality of side strands 2B are twisted together with one core strand 2A by normal twisting. By twisting the wire rope 1 by normal twisting, the wires of the outermost layer of the wire rope 1 are approximately parallel to the direction in which the wire rope 1 extends. As a result, even if the wire rope 1 slides against a sliding object in the direction in which the wire rope 1 extends, the wires of the outermost layer of the wire rope 1 make line contact with the sliding object rather than point contact, so that damage to the wire rope 1 can be suppressed. Furthermore, by twisting the wire rope 1 by normal twisting, the twisting direction of the wires of the outermost layer of the side strands 2B is opposite to the twisting direction of the side strands 2B, so that the occurrence of twisting tendencies in the wire rope 1 can be suppressed. Therefore, when the wire rope 1 is arranged approximately parallel to the direction in which the groove of a direction-changing member such as a pulley extends, the wire rope 1 is prevented from sliding on the side wall of the groove of the direction-changing member due to the twisting tendencies. Therefore, damage to the wire rope 1 caused by sliding on the side wall of the groove of the direction-changing member can be suppressed. However, the wire rope is not limited to this embodiment, and may have a structure in which a plurality of side strands are twisted around one core strand by Lang twisting.

[0016] As shown in Fig. 2 and Fig. 3, the strand 2 constituting the wire rope 1 includes a core material 21 in which a plurality of wires are twisted together, a first layer 22 formed by twisting a plurality of wires around the core material 21, and a second layer 23 formed by twisting a plurality of wires around the first layer 22. In this embodiment, all the strands 2 (core strand 2A and a plurality of side strands 2B) constituting the same wire rope 1 have the same structure. However, even the strands constituting the same wire rope may have different structures as long as they can produce the effects described in this specification. For example, the wire rope may have a core strand having the structure shown in Fig. 2 and a side strand having the structure shown in Fig. 3, or vice versa.

[0017] The core material 21 is a member formed by twisting a plurality of wires together and disposed at the center of the strand 2. The core material 21 may be formed by twisting a plurality of wires together, and the configuration is not particularly limited. In this embodiment, as shown in Figs. 2 and 3, the core material 21 includes one core wire 21a and a plurality of side wires 21b twisted around the core wire 21a (hereinafter, the core wire 21a and the side wire 21b are also collectively referred to as "wires 21a, 21b"). The twist direction of the side wire 21b is not particularly limited, and either Z twist or S twist can be adopted. However, as described later, it is preferable that the twist direction of the side wire 21b is opposite to the twist direction of the plurality of wires in the first layer 22.

[0018] The wire diameter and number of the wires 21a, 21b of the core material 21 are not particularly limited, but it is preferable to set the wire diameter and number of the side wires 21b so that the wire diameter of the core wire 21a of the core material 21 is approximately equal to the wire diameter of the multiple wires of the first layer 22 (wire diameters of all the wires in the example of FIG. 2, and wire diameters of some of the wires in the example of FIG. 3). This allows wires of the same wire diameter to be used for the core wire 21a of the core material 21 and the wires of the first layer 22, so that the number of types of wires constituting the strand 2 can be reduced, and manufacturing costs can be reduced. For example, in the first embodiment, the core material 21 is formed by twisting seven side wires 21b having a wire diameter smaller than the wire diameter of the core wire 21a around one core wire 21a, as shown in FIG. 2. In the second embodiment, as shown in Fig. 3, the core material 21 is formed by twisting together one core wire 21a and six side wires 21b having a wire diameter equal to or slightly smaller than the wire diameter of the core wire 21a. The specific wire diameters of the wires 21a and 21b of the core material 21 are not particularly limited and can be appropriately selected according to the rope diameter of the wire rope 1. For example, when used in an application in which a large space cannot be secured for wiring the wire rope, such as a medical instrument MD, the rope diameter of the wire rope 1 is set to less than 1 mm, and in this case, the wire diameters of the core wire 21a and side wires 21b of the core material 21 are set in the ranges of 0.017 to 0.062 mm and 0.011 to 0.042 mm, respectively.

[0019] Although not particularly limited, the wires 21a, 21b of the core material 21 are preferably made of tungsten. By making the wires 21a, 21b of the core material 21 out of tungsten, the strength of the wire rope 1 is improved, and the elongation resistance and bending fatigue durability of the wire rope 1 are further improved, compared to when the wires are made out of steel or stainless steel.

[0020] The first layer 22 is a layer formed by twisting a plurality of wires around the core material 21 so as to cover the outer periphery of the core material 21. The first layer 22 may be formed by twisting a plurality of wires, and the configuration is not particularly limited. In the first embodiment, the first layer 22 is formed by a plurality of wires 22a (10 in the illustrated example) having the same wire diameter, as shown in FIG. 2. In the first embodiment, the wire diameter of the wire 22a constituting the first layer 22 is larger than the wire diameters of the wires 23a and 23b constituting the second layer 23. In the second embodiment, the first layer 22 has a Warrington shape in which wires 22b and 22c having different wire diameters are alternately arranged along the circumferential direction, as shown in FIG. 3. In other words, in the first layer 22, the wires 22b, which have a relatively large wire diameter, are arranged in the gap between two adjacent side wires 21b, 21b of the core material 21, and the wire 22c, which has a relatively small wire diameter, is arranged on one side wire 21b of the core material 21, so that the wires 22b and 22c are arranged alternately, forming a Warrington structure.

[0021] The twisting direction of the wires 22a, 22b, and 22c constituting the first layer 22 is not particularly limited, and either Z twist or S twist can be adopted. In this embodiment, the wires 22a, 22b, and 22c of the first layer 22 are cross-twisted with the side wires 21b of the core 21. That is, the twisting direction of the wires 22a, 22b, and 22c of the first layer 22 is opposite to the twisting direction of the side wires 21b of the core 21. This suppresses twisting of the strand 2 and thus the wire rope 1, and improves the bendability of the wire rope 1 by point contact between the wires 22a, 22b, and 22c of the first layer 22 and the side wires 21b of the core 21. However, the multiple wires 22a, 22b, 22c of the first layer 22 may be twisted with the multiple side wires 21b of the core material 21 in a parallel twist.

[0022] The wires 22a, 22b, 22c of the first layer 22 are preferably made of tungsten, although there is no particular limitation thereon. By making the wires 22a, 22b, 22c of the first layer 22 out of tungsten, the strength of the wire rope 1 is improved, and the elongation resistance and bending fatigue durability of the wire rope 1 are further improved, compared to when the wires are made out of steel or stainless steel. The specific wire diameters of the wires 22a, 22b, 22c of the first layer 22 are not particularly limited, and can be appropriately selected according to the rope diameter of the wire rope 1. For example, when the wire rope 1 is used in an application where a large space cannot be secured for routing the wire rope, such as a medical device MD, the rope diameter of the wire rope 1 is set to less than 1 mm, and in this case, the wire diameters of the wires 22a, 22b, 22c of the first layer 22 are set in the ranges of 0.017 to 0.062 mm, 0.014 to 0.051 mm, and 0.010 to 0.038 mm, respectively.

[0023] The second layer 23 is a layer formed by twisting a plurality of wires around the first layer 22 so as to cover the outer periphery of the first layer 22. The second layer 23 may be formed by twisting a plurality of wires, and the configuration is not particularly limited. In the first embodiment, the second layer 23 has a Warrington shape in which wires 23a, 23b having different wire diameters are alternately arranged along the circumferential direction as shown in FIG. 2. That is, in the second layer 23, the wires 23a and the wires 23b are alternately arranged one by one such that the wire 23a having a relatively large wire diameter is arranged in the gap between two adjacent wires 22a, 22a of the first layer 22, and the wire 23b having a relatively small wire diameter is arranged on one wire 22a of the first layer 22, forming a Warrington structure. When the strand 2 has such a Warrington structure, the bending fatigue durability of the wire rope 1 is further improved. In the second embodiment, the second layer 23 is formed of a plurality of wires 23c (12 in the illustrated example) having the same wire diameter, as shown in FIG. 3. In the second embodiment, the wire diameter of the wires 23c constituting the second layer 23 is larger than the wire diameter of the wires 22b, 22c constituting the first layer 22. The wire rope 1 can achieve excellent abrasion resistance by increasing the wire diameter of the wires in the outermost layer. The second layer 23 is formed by arranging each of the plurality of wires 23c in the gap between the wires 22b and 22c arranged alternately in the first layer 22. In the second embodiment, the strand 2 has a Warrington seal type structure together with the first layer 22 and the second layer 23, which further improves the bending fatigue durability of the wire rope 1.

[0024] The wires of the second layer 23 are twisted in a parallel manner with respect to the wires of the first layer 22. Specifically, in the first embodiment shown in FIG. 2, the wires 23a, 23b of the second layer 23 are twisted in a parallel manner with respect to the wires 22a of the first layer 22, and in the second embodiment shown in FIG. 3, the wires 23c of the second layer 23 are twisted in a parallel manner with respect to the wires 22b, 22c of the first layer 22. That is, the wires of the second layer 23 are twisted in the same twisting direction at the same pitch as the wires of the first layer 22. This allows the wire rope 1 to have excellent elongation resistance and bending fatigue durability even if the rope diameter is reduced. When the wires of the second layer are twisted in a cross-twist manner with respect to the wires of the first layer, the wires of the first layer and the wires of the second layer come into point contact with each other. In this case, when a tensile or bending force is applied to the wire rope, the wires of the first layer and the wires of the second layer bend relative to each other around the point contact. When a tensile force is applied to the wire rope, the wires are likely to bend relative to each other, causing a change in length of the wire rope, and when a bending force is applied to the wire rope, the wires are likely to bend relative to each other, causing breakage of the wires. Therefore, when the wires of the second layer are cross-laid with respect to the wires of the first layer, the wire rope cannot obtain excellent elongation resistance and bending fatigue durability. In contrast, in the first embodiment shown in FIG. 2, the wires 23a, 23b of the second layer 23 are parallel-laid with respect to the wires 22a of the first layer 22, causing line contact between the wires 22a of the first layer 22 and the wires 23a, 23b of the second layer 23. This prevents the wires 22a of the first layer 22 and the wires 23a, 23b of the second layer 23 from bending relative to each other. Similarly, in the second embodiment shown in Fig. 3, the wires 23c of the second layer 23 are twisted in parallel to the wires 22b, 22c of the first layer 22, so that the wires 22b, 22c of the first layer 22 and the wire 23c of the second layer 23 are in linear contact with each other. This prevents the wires 22b, 22c of the first layer 22 and the wire 23c of the second layer 23 from bending relative to each other. Therefore, the wire rope 1 can obtain excellent elongation resistance and bending fatigue durability.

[0025] The wires 23a, 23b, 23c of the second layer 23 are preferably made of tungsten, although there is no particular limitation thereon. By making the wires 23a, 23b, 23c of the second layer 23 out of tungsten, the strength of the wire rope 1 is improved, and the elongation resistance and bending fatigue durability of the wire rope 1 are further improved, compared to when the wires are made out of steel or stainless steel. The specific wire diameters of the wires 23a, 23b, 23c of the second layer 23 are not particularly limited, and can be appropriately selected depending on the rope diameter of the wire rope 1. For example, when the wire rope 1 is used in an application where a large space cannot be secured for routing the wire rope, such as a medical device MD, the rope diameter of the wire rope 1 is set to less than 1 mm, and in this case, the wire diameters of the wires 23a, 23b, 23c of the second layer 23 are set in the ranges of 0.015 to 0.056 mm, 0.016 to 0.057 mm, and 0.013 to 0.022 mm, respectively.

[0026] From the viewpoint of obtaining excellent bendability, the wire rope 1 preferably has a void ratio between the wires of the strand 2 of 10% or more, and more preferably has a void ratio of 12% or more. From the viewpoint of obtaining even better elongation resistance and bending fatigue durability, the wire rope 1 preferably has a void ratio between the wires of the strand 2 of 19% or less, and more preferably has a void ratio of 18.6% or less. The void ratio between the wires means the ratio of the area of ​​the gaps between the wires (areas within the circumscribing circle where no wires exist) to the area of ​​the circumscribing circle of the strand 2 in a cross section perpendicular to the extension direction of the strand 2. The lower the void ratio between the wires, the higher the density of the wires in the strand 2, and the higher the void ratio between the wires, the lower the density of the wires in the strand 2. The void ratio between the wires of the strand 2 can be adjusted by appropriately setting the wire diameter of the wires in the strand 2, the pitch ratio of the wires in the strand 2 (which varies depending on the twist angle), the gap between the wires in the outermost layer of the strand 2 and the circumscribing circle of the strand 2, and the like. For example, by increasing the twist angle of the wires, the cross-sectional shape of the wires in a cross section perpendicular to the axial direction of the strand 2 has a larger flattening ratio of an ellipse, so that the void ratio can be reduced. Increasing the twist angle of the wires increases the contact area per unit length between the wires of the strand 2, so that the area per unit length that receives the load acting on the wire rope 1 increases, improving the flexural fatigue durability. Conversely, decreasing the twist angle of the wires improves the elongation resistance of the wire rope 1. Therefore, by setting the twist angle of the wires within a predetermined range and setting the void ratio within a predetermined range, it is possible to obtain even better elongation resistance and flexural fatigue durability. Furthermore, by setting the wire diameter so that all of the wires in the outermost layer of strand 2 are in contact with the circumscribing circle of strand 2, it is possible to reduce the gap between the wires in the outermost layer of strand 2 and the circumscribing circle of strand 2, thereby reducing the void ratio. In this case, the unevenness of the surface of strand 2 is reduced, so that it is possible to suppress the occurrence of local loads between strands when they are twisted together, further improving bending fatigue durability.Therefore, by reducing the gap between the wires in the outermost layer of the strand 2 and the circumscribing circle of the strand 2 and thereby reducing the void ratio, it is possible to obtain even better bending fatigue durability.

[0027] As described above, the wire rope 1 has a multi-stranded structure formed by twisting a plurality of strands 2 (side strands 2B) around one strand 2 (core strand 2A). The strand 2 forming the wire rope 1 includes a core material 21 formed by twisting a plurality of element wires together, a first layer 22 formed by twisting a plurality of element wires around the core material 21, and a second layer 23 formed by twisting a plurality of element wires around the first layer 22. The plurality of element wires forming the second layer 23 are twisted in parallel with the plurality of element wires forming the first layer 22. With this configuration, the wire rope 1 can obtain excellent elongation resistance and bending fatigue durability even if the rope diameter is made small.

[0028] In addition to having the above configuration, the wire rope 1 is preferably configured such that the rope diameter of the wire rope 1 is less than 1 mm, the breaking load of the wire rope 1 is 250 N or more, the permanent elongation of the wire rope 1 when a tensile load of 100 N is applied to the wire rope 1 is less than 0.1%, and when the wire rope 1 wound in an S-shape around two pulleys with a diameter of 3.5 mm is pushed and pulled back and forth with a load of 30 N, the number of back and forth operations until the wire constituting the wire rope 1 is broken is 2000 or more. By having such a configuration, the wire rope 1 can obtain even better elongation resistance and bending fatigue durability.

[0029] The breaking load of the wire rope 1 is evaluated by a breaking load tester shown in FIG. 4, in which the wire rope 1 is wound around two pulleys PL, PL with both ends of the wire rope 1 fixed, and a load is applied between the pulleys PL, PL to widen the distance between the pulleys PL, PL, and the wire rope 1 is broken. The permanent elongation of the wire rope 1 is evaluated by a percentage increase (increased length / initial length×100(%)) from the initial length of the wire rope 1 when both ends of the wire rope 1 having an initial length are pulled with a load of 100 N and then the load is removed using a permanent elongation tester shown in FIG. 5. The bending fatigue durability of the wire rope 1 is evaluated by the number of reciprocating operations until the wire rope 1 is broken when the wire rope 1 is pushed and pulled with a load W of 30 N applied to one end of the wire rope 1 wound in an S-shape around two pulleys PL, PL with a diameter of 3.5 mm, using a bending fatigue durability tester shown in FIG. 6.

[0030] Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. Note that the above embodiment mainly describes the invention having the following configuration.

[0031] (1) A wire rope having a multi-strand structure in which a plurality of strands are twisted together into one strand, The strands are A core material in which a plurality of wires are twisted together; a first layer formed by twisting a plurality of wires around the core material; A second layer formed by twisting a plurality of wires around the first layer; Equipped with The plurality of wires in the second layer are twisted in a parallel manner relative to the plurality of wires in the first layer. Wire rope.

[0032] (2) The wire rope described in (1), which is an operating wire rope that is wound around a direction-changing member having a curvature radius of less than 2.0 mm.

[0033] (3) The wire rope according to (1) or (2), wherein the wire rope is an operating wire rope used in a medical instrument for performing medical procedures inside the human body, the operating part and the actuating part of the medical instrument being routed via a direction changing member between the operating part and the actuating part of the medical instrument.

[0034] (4) A wire rope as described in any one of (1) to (3), wherein either the first layer or the second layer has a Warrington shape in which wires having different wire diameters are arranged alternately along the circumferential direction.

[0035] (5) A wire rope according to any one of (1) to (4), wherein a wire diameter of the wires constituting one of the first layer and the second layer is larger than a wire diameter of the wires constituting the other of the first layer and the second layer.

[0036] (6) The wire rope according to any one of (1) to (5), wherein the plurality of strands are twisted together into the single strand by ordinary twisting.

[0037] (7) The core material includes one core wire and a plurality of side wires twisted around the core wire, The wire rope according to any one of (1) to (6), wherein the plurality of wires in the first layer are cross-laid with respect to the plurality of side wires of the core.

[0038] (8) The wire rope according to any one of (1) to (7), wherein the void ratio between the wires of the strand is 12% to 19%.

[0039] (9) A wire rope described in any one of (1) to (8), wherein the wire diameter and number of the side wires of the core material are set so that the wire diameter of the core wire of the core material is approximately equal to the wire diameter of the multiple wires in the first layer.

[0040] (10) The wire rope according to any one of (1) to (9), wherein each of the wires in the core, the first layer and the second layer is made of tungsten.

[0041] (11) The wire rope has a rope diameter of less than 1 mm; The breaking load of the wire rope is 250N or more, The permanent elongation of the wire rope when a tensile load of 100 N is applied to the wire rope is less than 0.1%, The wire rope according to any one of (1) to (10), wherein when the wire rope is wound in an S-shape around two pulleys having a diameter of 3.5 mm and is pushed and pulled back and forth with a load of 30 N, the number of back and forth operations until the wire constituting the wire rope is broken is 2000 or more. EXAMPLES

[0042] The effects obtained by the wire rope 1 of the present embodiment will be specifically described below with reference to examples and comparative examples. However, the wire rope of the present invention is not limited to these examples.

[0043] (Wire rope) A wire rope having a multi-stranded structure in which six strands were twisted together in a single strand by normal twisting was produced. The rope diameter of the produced wire rope was as shown in Table 1. The strands constituting the wire rope were those having a configuration corresponding to FIG. 2 (Examples 1, 3, 5, 7), those having a configuration corresponding to FIG. 3 (Examples 2, 4, 6, 8), those made by twisting together 37 strands having the same strand diameter (Comparative Example 1), and those made by twisting together 19 strands having the same strand diameter (Comparative Example 2). As the twisting method of the second layer relative to the first layer in each strand, parallel twisting (Examples 1 to 8) and cross twisting (Comparative Examples 1 to 2) were adopted. The strands constituting each strand were made of tungsten. The void ratio between the strands of the produced wire rope was calculated by the following formula and was as shown in Table 1.

[0044]

number

[0045] (Strength evaluation) The strength of the wire rope was evaluated by the breaking load of the wire rope. The breaking load of the wire rope was measured by using a breaking load tester shown in Fig. 4, winding the wire rope 1 around two pulleys PL, PL with both ends of the wire rope 1 fixed, applying a load between the pulleys PL, PL and widening the distance between the pulleys PL, PL, and measuring the load at which the wire constituting the wire rope 1 breaks. The strength of the wire rope was evaluated as follows: if the breaking load of the wire rope was 300N or more, "◎", if it was 250N or more but less than 300N, "○", if it was 200N or more but less than 250N, "△", and if it was less than 200N, "×".

[0046] As can be seen from Table 1, all of the wire ropes of Examples 1 to 8 having parallel-laid strands have a breaking load of 250 N or more, and in particular, the wire ropes of Examples 1 to 4, in which the void ratio between the wires of the strands is 19% or less, have a breaking load of 300 N or more. In contrast, the wire ropes of Comparative Examples 1 and 2, in which the strands are cross-laid and the void ratio between the wires of the strands exceeds 19%, have a breaking load of less than 300 N, and in particular, the wire rope of Comparative Example 1 has a breaking load of less than 250 N. This shows that the strength of the wire rope is improved by configuring the strands with parallel lay, and that the strength of the wire rope is further improved by setting the void ratio between the wires of the strands to 19% or less.

[0047] (Evaluation of stretch resistance) The elongation resistance of the wire rope was evaluated by the permanent elongation of the wire rope. The permanent elongation of the wire rope was evaluated by the percentage increase in the length of the wire rope 1 from its initial length (increased length / initial length x 100 (%)) when both ends of the wire rope 1 having an initial length were pulled with a load of 100 N and then the load was removed using a permanent elongation tester shown in Figure 5. The elongation resistance of the wire rope was evaluated as follows: "◎" when the permanent elongation of the wire rope was less than 0.08%, "○" when it was 0.08% or more and less than 0.10%, "△" when it was 0.10% or more and less than 0.15%, and "X" when it was 0.15% or more.

[0048] As can be seen from Table 1, the wire ropes of Examples 1 to 8, in which the wires of the second layer in each strand are parallel-laid relative to the wires of the first layer, have smaller permanent elongation and better elongation resistance than the wire ropes of Comparative Examples 1 and 2, in which the wires of the second layer in each strand are cross-laid relative to the wires of the first layer. This shows that the elongation resistance of the wire rope is improved by parallel-laid twisting the wires of the second layer relative to the wires of the first layer.

[0049] (Flexural fatigue durability evaluation) The flexural fatigue durability of the wire rope was evaluated by the number of reciprocating operations until the wires constituting the wire rope 1 were broken when the wire rope 1 was pushed and pulled with a load W of 30 N applied to one end of the wire rope 1 wound in an S-shape around two pulleys PL, PL with a diameter of 3.5 mm, using a flexural fatigue durability tester shown in Figure 6. The flexural fatigue durability of the wire rope was evaluated as follows: 2500 or more reciprocating operations were marked with "◎", 2000 or more but less than 2500 operations were marked with "○", 1500 or more but less than 2000 operations were marked with "△", and less than 1500 operations were marked with "X".

[0050] As can be seen from Table 1, the wire ropes of Examples 1 to 8, in which the wires of the second layer are parallel-laid relative to the wires of the first layer in each strand, have superior flexural fatigue durability compared to the wire ropes of Comparative Examples 1 and 2, in which the wires of the second layer are cross-laid relative to the wires of the first layer in each strand. This shows that the flexural fatigue durability of the wire rope is improved by parallel-laid relative to the wires of the first layer in each strand. Even with the same parallel lay, the wire ropes of Examples 1 to 4, in which the void ratio between the wires of the strands is 19% or less, have superior flexural fatigue durability compared to the wire ropes of Examples 5 to 8, in which the void ratio between the wires of the strands exceeds 19%. This shows that the flexural fatigue durability of the wire rope is further improved by setting the void ratio between the wires of the strands to 19% or less. In particular, the wire ropes of Comparative Examples 1 and 2, in which the void ratio between the wires of the strands is significantly greater than 19%, are inferior in bending fatigue durability to the wire ropes of Examples 1 to 8, which shows the same thing.

[0051] [Table 1] [Explanation of symbols]

[0052] 1 Wire rope 2 Strand 2A core strand 2B Side Strand 21 Heartwood 21a Core wire (plain wire) 21b Side wire (element wire) 22 1st layer 22a, 22b, 22c bare wire 23 2nd layer 23a, 23b, 23c bare wire MD Medical Instruments MD1 operation section MD2 Actuator MD3 Directional Change Member PL Pulley W Load

Claims

1. A wire rope having a multi-stranded structure in which a plurality of strands are twisted together into one strand, The strands are A core material in which a plurality of wires are twisted together; a first layer formed by twisting a plurality of wires around the core material; a second layer formed by twisting a plurality of wires around the first layer; Equipped with The plurality of wires in the second layer are twisted in a parallel manner relative to the plurality of wires in the first layer. Wire rope.

2. The wire rope is an operating wire rope wound around a direction changing member having a curvature radius of less than 2.0 mm.

2. The wire rope according to claim 1.

3. The wire rope is an operating wire rope that is used in a medical instrument for performing a medical procedure inside a human body, and is routed between an operating part and an actuation part of the medical instrument via a direction changing member.

3. The wire rope according to claim 1 or 2.

4. One of the first layer and the second layer has a Warrington shape in which wires having different wire diameters are alternately arranged along the circumferential direction.

3. The wire rope according to claim 1 or 2.

5. a wire diameter of the wire constituting one of the first layer and the second layer is larger than a wire diameter of the wire constituting the other of the first layer and the second layer; 3. The wire rope according to claim 1 or 2.

6. The plurality of strands are twisted together with the single strand by normal twisting.

3. The wire rope according to claim 1 or 2.

7. The core material includes one core wire and a plurality of side wires twisted around the core wire, The plurality of wires of the first layer are cross-stranded with respect to the plurality of side wires of the core material.

3. The wire rope according to claim 1 or 2.

8. The void ratio between the wires of the strand is 12% to 19%.

3. The wire rope according to claim 1 or 2.

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