COMPOSITE ELECTRIC WIRE AND METHOD FOR MANUFACTURING COMPOSITE ELECTRIC WIRE

Abstract

[Problem] To obtain a composite electric wire with high electrical conductivity and high plasticity.

[Means for Resolution] A conductive layer 3 is disposed around a central core wire 2 and an insulating coating layer 4 is provided around the conductive layer 3 in a composite electric wire having an outer diameter of approximately 500 μm. The core wire 2 is made of four middle wires 2a to 2d twisted together. Each of the middle wires 2a to 2d is made by twisting a strand made of 48 aramid fibers. As for the conductive layer 3, 12 copper wires 3a with a diameter of 80 μm are closely and spirally wound around the core wire 2 and the circumference of the copper wires 3a is shaped into a circle by tightening.

Claims

1. A composite electric wire comprising: a core wire made of a synthetic resin fiber; and a conductive layer provided around the core wire, wherein the conductive layer includes a plurality of conductive metal wires and a low melting point metal bonding adjacent wires of the conductive metal wire to each other, covering an outer surface of the conductive metal wire, and lower in melting point than the conductive metal wire, all the conductive metal wires are in close contact along a surface of the core wire either directly or via the low melting point metal, and the conductive layer gaplessly covers a circumference of the core wire.

2. The composite electric wire according to claim 1, wherein a coating layer made of a synthetic resin material surrounding the core wire is provided between the core wire and the conductive layer.

3. The composite electric wire according to claim 1, wherein the conductive layer is covered with an insulating coating layer made of a synthetic resin material.

4. The composite electric wire according to claim 1, wherein the conductive metal wire is spirally wound around the core wire.

5. The composite electric wire according to claim 1, wherein the conductive layer has a circular outer circumference.

6. The composite electric wire according to claim 1, wherein the conductive metal wire is a copper wire and the low melting point metal is tin.

7. A method for manufacturing a composite electric wire in which a conductive layer is provided around a core wire made of a synthetic resin fiber, the method comprising: a metal winding step of closely placing all of a plurality of conductive metal wires along a surface of the core wire; and a metal wire plating step of plating an outer surface with a low melting point metal by immersing the wound conductive metal wire in the molten low melting point metal, forming the conductive layer by bonding adjacent wires of the conductive metal wire to each other with the low melting point metal, and causing the conductive layer to gaplessly cover a circumference of the core wire.

8. The method for manufacturing a composite electric wire according to claim 7, comprising a coating step of forming a coating layer made of a synthetic resin material around the core wire before the metal wire winding step.

9. The method for manufacturing a composite electric wire according to claim 7, comprising an insulating coating step of coating a surface of the conductive layer with an insulating coating layer made of a synthetic resin material after the metal wire plating step.

10. The method for manufacturing a composite electric wire according to claim 9, comprising a metal wire cleaning step of cleaning the conductive metal wire after the metal wire winding step and before the metal wire plating step.

11. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIG. 1 is a cross-sectional view of a composite electric wire of Example 1.

[0012] FIG. 2 is an explanatory diagram of a manufacturing process of Example 1.

[0013] FIG. 3 is a cross-sectional view of a state where a copper wire is along a core wire.

[0014] FIG. 4 is a perspective view of the state where the copper wire is along the core wire.

[0015] FIG. 5 is a cross-sectional view of a state where the copper wire is shaped.

[0016] FIG. 6 is a cross-sectional of a state where the copper wire is covered with a tin layer.

[0017] FIG. 7 is a cross-sectional view of the composite electric wire that is yet to undergo a shaping step.

[0018] FIG. 8 is a cross-sectional view of a composite electric wire of Example 2.

[0019] FIG. 9 is an explanatory diagram of a manufacturing process of Example 2.

[0020] FIG. 10 is a perspective view of a state where a core wire is surrounded by a coating layer with a copper wire placed therealong.

[0021] FIG. 11 is a cross-sectional view of a state where the copper wire is shaped.

[0022] FIG. 12 is a cross-sectional view of a state where the copper wire is covered with a tin layer.

[0023] FIG. 13 is a cross-sectional view of the composite electric wire that is yet to undergo a shaping step.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

[0024] The invention will be described in detail based on the illustrated examples.

EXAMPLE 1

[0025] FIG. 1 is a cross-sectional view of a composite electric wire 1 according to Example 1, A conductive layer 3 made of a copper wire 3a and a tin layer 3b is disposed around a core wire 2 and an insulating coating layer 4 is provided around the conductive layer 3 to have flexibility as a whole.

[0026] The core wire 2 is made of, for example, four middle wires 2a to 2d twisted together. Each of the middle wires 2a to 2d is made by twisting a synthetic resin material such as a polymer strand made of 48 aramid fibers. The strands have a diameter of, for example, 12 μm. The diameter of the core wire 2 is approximately 200 μm. It should be noted that the aramid fiber is lightweight, has high strength, has high flexibility, and does not have electrical conductivity.

[0027] The conductive layer 3 includes a conductive metal wire that has a high melting point, examples of which include the copper wire (Cu: melting point 1085° C.) 3a, and a low melting point metal that bonds adjacent wires of the conductive metal wire to each other, covers the outer surface of the conductive metal wire, and is a metal lower in melting point than the conductive metal wire, examples of which include the tin (Sn: melting point 232° C.) layer 3b.

[0028] The copper wire 3a has a diameter of, for example, 80 μm, and 12 copper wires 3a are closely and spirally wound around the core wire 2 by a winding machine. Tin as a low melting point metal is melted and welded therearound, that is, the copper wire 3a is plated such that the circumference of the copper wire 3a is covered with the tin layer 3b and the adjacent wires are bonded to each other. It should be noted that the low melting point in the example is based on the temperature at which the low melting point metal melts in a plating tank to be described later.

[0029] The insulating coating layer 4 is formed of a soft synthetic resin material having electrical insulation, covers the upper layer of the conductive layer 3, and has a thickness of, for example, 50 μm. The diameter of the composite electric wire 1 including the insulating coating layer 4 is approximately 500 μm (0.5 mm).

[0030] FIG. 2 illustrates a process of manufacturing the composite electric wire 1. In a metal wire winding step A, the copper wire 3a having a diameter of 80 μm as a part of the conductive layer 3 is wound around the core wire 2 by a winding machine. As illustrated in FIGS. 3 and 4, the copper wire 3a is closely and spirally wound around the core wire 2.

[0031] Although the middle wires 2a to 2d in the core wire 2 are also loosely twisted in a spiral shape, the copper wire 3a is larger in spiral angle than the middle wires 2a to 2d. In addition, the direction of the spiral of the copper wire 3a is different from the direction of the spiral of the middle wires 2a to 2d and it is preferable that the directions of the spirals intersect with each other such that the copper wire 3a does not bite into the gap of the core wire 2. It should be noted that the copper wire 3a is robust when wound in a spiral shape although the copper wires 3a may be arranged along the longitudinal direction of the core wire 2.

[0032] In this manner, the surface of the core wire 2 with the copper wire 3a along the circumference thereof is shaped into a circle as a result of a metal wire shaping step B, in which a die or the like is used and the copper wire 3 a is tightened from the circumference thereof as illustrated in FIG. 5.

[0033] Subsequently, in a metal wire plating step C, the core wire 2 around which the copper wire 3a is wound is immersed during feeding into the plating tank in which tin (Sn) as a low melting point metal is melted. In the plating tank, the molten tin covers the surface of the copper wire 3a with a thickness of several micrometers and enters between the adjacent copper wires 3a, forms the tin layer 3b on outer surface of the copper wires 3a, and bonds the adjacent wires to each other. As a result of the metal wire plating step C, the copper wire 3a and the tin layer 3b are integrated, the tin layer 3b covers the outside of the copper wire 3a, and the conductive layer 3 in which the adjacent wires are bonded to each other is formed as illustrated in FIG. 6. The conductive layer 3 gaplessly covers the circumference of the core wire 2.

[0034] Further, the circumference of the conductive layer 3 is coated with the insulating coating layer 4 made of a synthetic resin material in an insulating coating step D, in which the core wire 2 with the conductive layer 3 is passed through a coating molding machine. The composite electric wire 1 illustrated in FIG. 1 is obtained as a result.

[0035] It should be noted that the composite electric wire 1 may include the core wire 2 and the conductive layer 3 with the insulating coating layer 4 not formed.

[0036] The metal wire winding step A, the metal wire shaping step B, the metal wire plating step C, and the insulating coating step D may be continuously carried out on the same production line. Alternatively, the next step may be carried out after one step is completed and the reel is wound once.

[0037] It should be noted that the composite electric wire 1 may be manufactured with the metal wire shaping step B omitted and through the metal wire plating step C and the insulating coating step 1) from the state of the cross-sectional view illustrated in FIG. 3 although the composite electric wire 1 is manufactured through the metal wire shaping step B for the copper wire 3a in Example 1. The composite electric wire 1 as illustrated in FIG. 7 is obtained in this case.

[0038] As described above, the conductive layer 3 of the composite electric wire 1 manufactured in Example 1 includes the tin layer 3b and the copper wires 3a, in which adjacent wires are bonded to each other with tin, and completely covers the circumference of the core wire 2.

[0039] When the insulating coating layer 4 is peeled off for crimping to a crimp connection terminal, the state illustrated in FIG. 6 occurs and the conductive layer 3 prevents the core wire 2 and the copper wire 3a from dispersing. In addition, the composite electric wire 1 has plasticity attributable to the copper wire 3a, and thus the composite electric wire 1 can be satisfactorily crimped by the crimping piece of the crimp connection terminal.

[0040] It should be noted that a conductive metal wire such as an aluminum wire can be used instead of the copper wire 3a in the conductive layer 3. In addition, solder (with a melting point of, for example, 180 to 220° C.) made of, for example, a tin-zinc alloy, which is also a low-melting metal, may be used instead of tin as a low melting point metal in which the copper wires 3a are bonded to each other.

EXAMPLE 2

[0041] 8 is a cross-sectional view of a composite electric wire 1′ according to Example 2. In the composite electric wire 1′, a coating layer 5 is provided around the core wire 2, the conductive layer 3 made of the copper wire 3a and the tin layer 3b is disposed outside the coating layer 5, and the insulating coating layer 4 is provided around the conductive layer 3.

[0042] Although the core wire 2 is similar in configuration to the core wire 2 of Example 1, the coating layer 5 is provided around the core wire 2, is made of, for example, a polyester-based resin, and has a thickness of several micrometers. In addition, the conductive layer 3 and the insulating coating layer 4 are similar in configuration to those of Example 1.

[0043] FIG. 9 is an explanatory diagram of a process of manufacturing the composite electric wire 1′. The process includes a coating step E of applying the coating layer 5 around the core wire 2, the metal wire winding step A of winding the copper wire 3a therearound, a metal wire shaping step B of shaping the outer diameter of the wound copper wire 3a into a circle, a metal wire cleaning step F of cleaning the copper wire 3a, the metal wire plating step B of forming the conductive layer 3 by plating the copper wire 3a with the tin layer 3b, and the insulating coating step D of coating the circumference of the conductive layer 3 with the insulating coating layer 4. It should be noted that the order of the metal wire shaping step B and the metal wire cleaning step F may be reversed.

[0044] In the coating step E, the coating layer 5 is applied around the core wire 2 by immersing the core wire 2 in a resin tank in which, for example, a polyester-based resin is melted. The coating layer 5 blocks flux agent infiltration into the core wire 2 in the metal wire cleaning step F to be described later.

[0045] As illustrated in FIG. 10, in the metal wire winding step A, 12 copper wires 3a are spirally wound around the coating layer 5 by a winding machine. In the next metal wire shaping step C, the surrounding copper wires 3a are tightened from the outside and the surface of the copper wires 3a is shaped into a circle as illustrated in FIG. 11.

[0046] Subsequently, in the metal wire cleaning step F, the copper wire 3a is pickled with a flux agent through a cleaning tank containing the flux agent made of a strong acid solution or the like such that plating easily adheres to the copper wire 3a in the next step. In this case, the flux agent does not infiltrate into the core wire 2 since the core wire 2 is covered with the coating layer 5.

[0047] Next, in the metal wire plating step C, the copper wire 3a is immersed during feeding into the plating tank in which tin (Sn) as a low melting point metal is melted. As illustrated in FIG. 12, the tin melted in the plating tank covers the surface of the copper wire 3a with a thickness of several micrometers and enters between the adjacent copper wires 3a to form the tin layer 3b on the outer surface of the copper wire 3a. In the metal wire plating step C, the copper wire 3a is satisfactorily plated with the tin layer 3b with oil, dirt, or the like removed from the copper wire 3a in the metal wire cleaning step F and the conductive layer 3 in which the adjacent copper wire 3a are bonded to each other is obtained. The conductive layer 3 gaplessly covers the circumference of the core wire 2.

[0048] In the metal wire plating step C, the melting point of the tin in the plating tank is 232° C. As a result, the melting point of the coating layer 5 in the case of using a polyester-based synthetic resin is approximately 250° C. and the coating layer 5 is hardly damaged by the molten tin.

[0049] Further, in the insulating coating step D, the electric wire provided with the conductive layer 3 is passed through a coating molding machine and the circumference of the conductive layer 3 is coated with the insulating coating layer 4 made of a synthetic resin material. The composite electric wire 1′ illustrated in FIG. 8 is obtained as a result.

[0050] It should be noted that the composite electric wire 1′ in Example 2 may be manufactured with the metal wire shaping step B omitted and through the metal wire cleaning step F, the metal wire plating step C, and the insulating coating step D.

REFERENCE SIGNS LIST

[0051] 1, 1′ Composite electric wire [0052] 2 Core wire [0053] 2a to 2d Middle wire [0054] 3a Copper wire [0055] 3b Tin layer [0056] 4 Insulating coating layer [0057] 5 Coating layer [0058] A Metal wire winding step [0059] B Metal wire shaping step [0060] C Metal wire plating step [0061] D Insulating coating step [0062] E Coating step [0063] F Metal wire cleaning step