JP2020181764A - Apparatus for manufacturing foamed wire, method for manufacturing foamed wire, and foamed wire - Google Patents

Abstract

To provide an apparatus for manufacturing a foamed wire capable of suppressing the scattering of dielectric constants in a longitudinal direction even if reducing a thickness of a foamed insulator, a method for manufacturing a foamed wire, and a foamed wire.SOLUTION: In an apparatus 1 for manufacturing a foamed wire which forms a foamed insulator 12 around an outer periphery of a center conductor 11 by extruding and foaming a resin 3 from an extrusion metal mold 2 having a mandrel 21, and a mouthpiece 22, the mouthpiece 22 has a taper part 22a formed into taper-like so that an inner peripheral surface 22b gradually outspreads at an extruding exit thereof in an extrusion direction as a foam-growing part, and a foam nucleus-generating part 23 constituted by forming a plurality of protrusions 23a or concavities 23b or both of them on the inner peripheral surface 22b of the taper part 22a and is constituted so as to extrude nuclei 13a of the foam by flow of the resin while generating the nuclei 13a of the foam by the foam nucleus-generating part 23, growing the nuclei 13a of the foam in accordance with lowering of a resin pressure at the taper part 22a, and form a foam 13 in the foamed insulator 12.SELECTED DRAWING: Figure 1

Description

The present invention relates to a foamed electric wire manufacturing apparatus, a foamed electric wire manufacturing method, and a foamed electric wire.

In recent years, as the performance of electronic devices has improved, the speed of signals transmitted to the electric wires used for them has also increased. As an electric wire for high-speed signal transmission, a foamed electric wire in which the dielectric constant of the insulator as a whole is lowered by containing air bubbles in the insulator and the transmission loss of a high-speed signal is suppressed is known.

Conventionally, when manufacturing a foamed electric wire, a foaming agent such as nitrogen or carbon dioxide and a foaming nucleating agent are supplied to the extruder together with a resin, and when the resin is discharged from the extruder and the pressure is released, the foaming nucleating agent is released. A foamed insulator was formed by generating bubbles around the core.

For example, in a probe cable used in an ultrasonic diagnostic apparatus, hundreds of foamed electric wires (coaxial cables) in which a foamed insulator, an outer conductor, and a sheath are sequentially formed around a central conductor are bundled into a cable. Therefore, it is desirable that the foamed electric wire used for the probe cable has a diameter as small as possible in order to improve the maneuverability.

As prior art document information related to the invention of this application, there is Patent Document 1.

Japanese Unexamined Patent Publication No. 2011-228604

In a small diameter foamed electric wire, it is necessary to reduce the thickness of the foamed insulator. However, in the conventional method using a foam nucleating agent, the position where bubbles are generated and the size of the bubbles become random. Therefore, especially when the foam insulator is thinned, the dielectric constant varies in the longitudinal direction. (That is, there is a problem that the variation in the characteristic impedance) becomes large and the transmission loss when transmitting a high-speed signal becomes large.

Therefore, according to the present invention, even when the thickness of the foamed insulator is reduced, a foamed electric wire manufacturing apparatus capable of suppressing variation in the dielectric constant in the longitudinal direction of the foamed insulator, a foamed electric wire manufacturing method, and foaming. The purpose is to provide electric wires.

An object of the present invention is to solve the above-mentioned problems in a foamed electric wire manufacturing apparatus for forming a foamed insulator on the outer periphery of a central conductor by extruding and foaming a resin from an extrusion die having a core and a base. The base has a bubble growth portion formed in a tapered shape whose inner peripheral surface gradually expands in the extrusion direction at its extrusion outlet, and a plurality of convex portions for generating bubble nuclei on the inner peripheral surface of the bubble growth portion. Alternatively, it has a bubble nucleation generation part formed by forming a recess or both, and while generating a bubble nuclei in the bubble nucleation generation part, the bubble nuclei are extruded by a resin flow, and the resin in the bubble growth part. Provided is an apparatus for manufacturing a foamed electric wire, which is configured to grow a nucleus of the bubble as the pressure decreases to form a bubble in the foamed insulator.

The present invention also relates to a method for manufacturing a foamed electric wire, which forms a foamed insulator on the outer periphery of a central conductor by extruding and foaming a resin from an extrusion die having a core and a mouthpiece, for the purpose of solving the above problems. The mouthpiece has a bubble growth portion formed in a tapered shape whose inner peripheral surface gradually expands in the extrusion direction at its extrusion outlet, and a plurality of bubble nuclei generation portions on the inner peripheral surface of the bubble growth portion. It has a bubble nucleation generation part formed by forming a convex portion, a concave portion, or both, and while generating a bubble nuclei in the bubble nucleation generation part, the bubble nuclei are extruded by a resin flow, and the bubble growth portion Provided is a method for manufacturing a foamed electric wire, which grows nuclei of the bubbles in accordance with a decrease in the resin pressure of the foamed insulator to form bubbles in the foamed insulator.

Further, for the purpose of solving the above problems, the present invention includes a central conductor and a foamed insulator having a thickness of 100 μm or less that covers the outer periphery of the center conductor, and the foamed insulator is provided with a foamed insulator in the longitudinal direction. Provided is a foamed electric wire in which bubbles are formed intermittently in a straight line along the line.

According to the present invention, even when the thickness of the foamed insulator is reduced, a foamed electric wire manufacturing apparatus capable of suppressing variation in the dielectric constant in the longitudinal direction of the foamed insulator, a foamed electric wire manufacturing method, and foaming. Electric wires can be provided.

(A) is a cross-sectional view of a foamed electric wire manufacturing apparatus according to an embodiment of the present invention, and (b) is an enlarged view of part A thereof. (A) is a perspective view showing the structure of the tip portion of the base portion, (b) is a side view thereof, and (c) is a schematic view when the tapered portion is expanded. (A) and (b) are explanatory views explaining bubble nucleation by a convex concave part. (A) is a cross-sectional view showing a cross section perpendicular to the longitudinal direction of the foamed electric wire according to the embodiment of the present invention, and (b) is a cross-sectional view taken along the line BB of (a). It is sectional drawing of the conventional foam electric wire. It is sectional drawing which shows the cross section perpendicular to the longitudinal direction of the foamed electric wire which concerns on other embodiment of this invention.

[Embodiment]
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

(Overall configuration of foamed wire manufacturing equipment)
FIG. 1 is a cross-sectional view of a foamed electric wire manufacturing apparatus according to the present embodiment. FIG. 2A is a perspective view showing the structure of the tip portion of the base portion, FIG. 2B is a side view thereof, and FIG. 2C is a schematic view when the tapered portion is expanded.

As shown in FIGS. 1 and 2, the foamed electric wire manufacturing apparatus 1 extrudes the resin 3 from the extrusion die 2 having the core metal 21 and the mouthpiece 22, and foams the resin 3 to form a foamed insulator 12 on the outer periphery of the central conductor 11. It is what forms.

The resin 3 put into the foamed electric wire manufacturing apparatus 1 is kneaded by a screw (not shown) and conveyed to the tip of the foamed electric wire manufacturing apparatus 1 provided with the base 22. The resin 3 is conveyed to the base 22 side while being melted by shearing heat or the like due to kneading of the screw. Gas (a foaming agent such as carbon dioxide or nitrogen) is injected into the molten resin 3, and the gas is dissolved in the resin 3 at high pressure. In the present embodiment, the resin 3 does not contain a foaming nucleating agent.

The central conductor 11 is pulled out from the core metal 21, and the resin 3 is pushed out from the base 22 together with the center conductor 11 drawn out from the core metal 21. At this time, the resin 3 extruded from the base 22 is released to the atmospheric pressure, so that the dissolved gas becomes a gas and bubbles grow. As a result, a foamed electric wire 10 having a foamed insulator 12 having bubbles 13 formed on the outer periphery of the central conductor 11 can be obtained.

(Explanation of bubble nucleation unit 23)
In the foamed electric wire manufacturing apparatus 1 according to the present embodiment, the base 22 has a tapered portion 22a as a bubble growth portion formed in a tapered shape in which the inner peripheral surface 22b gradually expands in the extrusion direction at the extrusion outlet. doing. Further, the base 22 has a bubble nucleation portion 23 formed by forming a plurality of convex portions 23a and / or concave portions 23b for bubble nucleation on the inner peripheral surface 22b of the tapered portion 22a.

As shown in FIG. 3A, by forming the convex portion 23a and the concave portion 23b as the bubble nucleation part 23 on the inner peripheral surface 22b of the tapered part 22a, the resin 3 is formed in the vicinity of the bubble nucleation part 23. The flow is disturbed and the resin pressure changes, and bubble nuclei 13a are generated from the interface (the surface of the convex portion 23a and the concave portion 23b) between the resin 3 and the inner peripheral surface 22b of the tapered portion 22a. As shown in FIG. 3B, the generated bubble nuclei 13a are extruded together with the resin 3 by the flow of the resin 3 while growing along the pressure gradient at the tapered portion 22a, and the bubbles in the foamed insulator 12 are formed. It becomes 13.

In this way, in the foamed electric wire manufacturing apparatus 1, the bubble nuclei 13a are generated by the bubble nucleation unit 23, and the bubble nuclei 13a are pushed out by the flow of the resin in accordance with the decrease in the resin pressure at the tapered portion 22a. It is configured to grow the nucleus 13a of the bubble to form the bubble 13 in the foamed insulator 12. As a result, the foamed insulator 12 can be formed by continuously generating the cell nuclei 13a in the bubble nucleation unit 23 without using the foaming nucleating agent.

In the present embodiment, the bubble nucleation unit 23 is configured by forming both the convex portion 23a and the concave portion 23b on the inner peripheral surface 22b of the tapered portion 22a. However, even if only the convex portion 23a or only the concave portion 23b is formed on the inner peripheral surface 22b of the tapered portion 22a, the nucleus 13a of the bubble can be generated. However, as compared with the case where only the convex portion 23a or only the concave portion 23b is formed, when both the convex portion 23a and the concave portion 23b are formed, the flow of the resin 3 is more likely to be disturbed, and the bubble core 13a is more likely to be formed. It is stable and easy to occur.

Further, by forming the bubble nucleation portion 23 so that the convex portion 23a and the concave portion 23b are adjacent to each other in the extrusion direction, the flow of the resin 3 is more likely to be disturbed, and the bubble nuclei 13a are generated more stably. It will be easier. In the present embodiment, the concave-convex portion 23c in which the convex portion 23a, the concave portion 23b, and the convex portion 23a are sequentially formed is formed on the inner peripheral surface 22b of the tapered portion 22a along the extrusion direction of the resin 3, and the concave-convex portion 23c is formed. Are formed over the circumferential direction of the inner peripheral surface 22b of the tapered portion 22a.

Each uneven portion 23c of the bubble nucleation unit 23 serves as a starting point for generating the bubble 13 (the position where the bubble nuclei 13a are generated). Therefore, it is desirable that the bubbles 13 are formed at substantially equal intervals in the circumferential direction of the inner peripheral surface 22b of the tapered portion 22a so that the bubbles 13 are evenly dispersed in the foamed insulator 12.

Further, here, in each uneven portion 23c, the convex portion 23a and the concave portion 23b are adjacent to each other, but the convex portion 23a and the concave portion 23b may be separated from each other. However, from the viewpoint of disturbing the flow of the resin 3 and stably generating the nucleus 13a of the bubbles, it is desirable that the convex portion 23a and the concave portion 23b are formed as close as possible to each other.

In the present embodiment, the convex portion 23a having a square columnar shape is formed and the concave portion 23b is formed so as to have a quadrangular shape in a plan view, but the shapes of the convex portion 23a and the concave portion 23b are not limited to this. For example, the shape may have rounded corners. However, in order to disturb the flow of the resin 3 and stably generate the nucleus 13a of the bubble, a shape that draws a gentle curve is not preferable, and it can be said that it is desirable to include an edge portion that rises or falls sharply. ..

Further, the sum of the height of the convex portion 23a from the inner peripheral surface 22b of the tapered portion 22a and the depth of the concave portion 23b from the inner peripheral surface 22b of the tapered portion 22a in the bubble nucleation portion 23 (hereinafter referred to as the uneven height). ) H is preferably 20 μm or more. This is because when the uneven height h is 20 μm or less, the generation of bubble nuclei 13a becomes unstable, which is not desirable.

Further, the uneven height h is preferably not more than half the thickness of the foamed insulator 12. This is because if the uneven height h exceeds half the thickness of the foamed insulator 12, problems such as the convex portion 23a coming into contact with the central conductor 11 may occur. For example, when the thickness of the foamed insulator 12 is 100 μm, the uneven height h is preferably 20 μm or more and 50 μm or less.

In the concave-convex portion 23c of the bubble nucleation portion 23, it is desirable that the length L1 of the convex portion 23a in the extrusion direction is larger than the length L2 of the concave portion 23b in the extrusion direction. This is because if the length L2 of the concave portion 23b is longer than the length L1 of the convex portion 23a, the generation of the bubble core 13a may become unstable.

It is desirable that the bubble nucleation portion 23 is formed in a portion where the opening of the base 22 is the narrowest, that is, as close as possible to the base end portion of the tapered portion 22a. This is because bubble nuclei 13a are generated in the process of releasing the pressure of the resin 3. For example, a bubble nucleation portion is generated at the tip of the tapered portion 22a in which the pressure of the resin 3 is substantially released. This is because even if 23 is formed, it becomes difficult to stably generate the nucleus 13a of the bubble.

In addition, in order to stably generate the nucleus 13a of the bubble, it is desirable that the fluidity (viscosity) of the resin 3 is as small as possible. For example, when a fluororesin such as PFA (perfluoroalkoxy alkane) or FEP (fluorinated ethylene / propylene hexafluoride copolymer) is used as the resin 3, the melt flow rate (MFR) of the resin 3 is 50 or more. It is desirable, and more preferably 70 or more.

(Manufacturing method of foamed electric wire)
In the method for manufacturing a foamed electric wire according to the present embodiment, the resin 3 is extruded and foamed from an extrusion die 2 having a core metal 21 and a base 22 by using the above-mentioned foamed electric wire manufacturing apparatus 1 to form a central conductor 11. This is a method of forming a foamed insulator 12 on the outer periphery.

That is, in the method for manufacturing a foamed electric wire according to the present embodiment, a bubble nucleation portion 23 formed by forming both a plurality of convex portions 23a or concave portions 23b is formed in the tapered portion 22a of the base 22 to form bubbles. While generating the bubble nuclei 13a in the nucleation section 23, the bubble nuclei 13a are pushed out by the flow of the resin, and the bubble nuclei 13a are grown in accordance with the decrease in the resin pressure in the tapered portion 22a as the bubble growth section. The bubbles 13 in the foam insulator 12 are formed.

As shown in FIG. 2 (c), the bubble nuclei 13a generated by the bubble nucleation unit 23 are sequentially extruded toward the outlet of the base 22, and continuously (intermittently) by the bubble nucleation unit 23. Nuclei 13a of bubbles are generated in. As a result, uniform and independent bubbles 13 are formed intermittently in a straight line along the longitudinal direction of the extruded foam insulator 12.

When a foam nucleating agent such as boron nitride is contained in the resin 3 extruded from the extrusion die 2, the foam nucleating agent is randomly used as a nucleus in addition to the bubble 13 in which the bubble nuclei 13a generated by the bubble nucleating unit 23 are grown. Bubbles 13 are generated in the foam insulator 12, and it becomes difficult to uniformly form the bubbles 13 in the foamed insulator 12. Therefore, in the method for manufacturing a foamed electric wire according to the present embodiment, the resin 3 extruded from the extrusion die 2 does not contain a foaming nucleating agent.

(Explanation of foamed electric wire 10)
FIG. 4A is a cross-sectional view showing a cross section perpendicular to the longitudinal direction of the foamed electric wire 10 according to the present embodiment, and FIG. 4B is a cross-sectional view taken along the line BB of FIG. 4A.

As shown in FIGS. 4A and 4B, the foamed electric wire 10 includes a central conductor 11 and a foamed insulator 12 having a thickness of 100 μm or less that covers the outer periphery of the center conductor 11, and the foamed insulator 12 has a thickness of 100 μm or less. In the above, bubbles 13 are intermittently formed in a straight line along the longitudinal direction.

The center conductor 11 may be a single wire conductor or a stranded wire conductor obtained by twisting a plurality of metal strands. Further, the single wire conductor may have a circular cross-sectional shape or a rectangular shape (that is, a flat conductor). In the present embodiment, the central conductor 11 is composed of a stranded conductor. By forming the central conductor 11 with a stranded wire conductor, durability against bending is improved, and when the foamed insulator 12 is formed, the resin 3 enters the gap between the metal strands, and the foamed insulator 12 and the center conductor are formed. Adhesion with 11 is improved. For example, when the central conductor 11 is a single wire conductor, air bubbles may be generated on the surface of the central conductor 11 and the central conductor 11 may float with respect to the foamed insulator 12, but the central conductor 11 is used. By using a stranded wire conductor, such a problem can be suppressed.

FIGS. 4A and 4B show a case where bubbles 13 are formed at equal intervals at four locations in the circumferential direction. The diameter (maximum diameter) of the bubbles 13 in the foamed insulator 12 is preferably 50% or more and 60% or less of the thickness of the foamed insulator 12, and is equidistantly spaced in the circumferential direction around the central conductor 11. It is more desirable that four or more bubbles 13 are formed. The diameter of the bubbles 13 in the foamed insulator 12 can be adjusted by the gas injection pressure, the discharge amount of the resin 3, and the like, and the number of bubbles 13 in the circumferential direction is the convex portion 23a and the concave portion 23b in the bubble nucleation unit 23. It can be adjusted by the number of.

In the present embodiment, since the resin 3 does not contain a foaming nucleating agent, the foaming insulator 12 also does not contain a foaming nucleating agent such as boron nitride.

Here, for reference, FIG. 5 shows a conventional foamed electric wire foamed with a foaming nucleating agent using a conventional foamed electric wire manufacturing apparatus having no bubble nucleation unit 23. In the conventional method, the foaming nucleating agent is used as a nucleus to generate and grow the bubbles 113, but since the foaming nucleating agent is randomly dispersed in the resin 3, the positions where the bubbles 113 are generated are random. Therefore, as shown in FIG. 5, in the conventional foamed electric wire 100, the positions and sizes of the bubbles 113 are random in the foamed insulator 112 provided on the outer periphery of the central conductor 111. Therefore, especially when the foamed insulator 112 is made thin, the variation in the dielectric constant (that is, the variation in the characteristic impedance) becomes large in the longitudinal direction, and the transmission loss when transmitting a high-speed signal becomes large. Reference numeral 111 in the figure is a central conductor of a conventional foamed electric wire.

On the other hand, in the foamed electric wire 10 according to the present embodiment, since the foamed insulator 12 has bubbles 13 intermittently formed in the longitudinal direction, even when the foamed insulator 112 is thinned. , The variation in the dielectric constant (that is, the variation in the characteristic impedance) in the longitudinal direction can be reduced, and the transmission loss when transmitting a high-speed signal can be reduced. That is, although the foamed electric wire 10 has a small diameter, the transmission loss when transmitting a high-speed signal is small.

(Other embodiments)
FIG. 6 is a cross-sectional view showing a cross section perpendicular to the longitudinal direction of the foamed electric wire according to another embodiment of the present invention. The foamed electric wire 10a shown in FIG. 6 is a so-called coaxial cable in which an outer conductor 41 and a sheath 42 are further provided on the outer periphery of the foamed insulator 12 of FIG.

As the outer conductor 41, a braided shield in which a plurality of metal wires are braided or a horizontal winding shield in which the metal wires are spirally wound can be used. Further, the outer conductor 41 may be formed by wrapping a metal foil or a metal tape having a metal layer formed on one surface of a resin film around the foam insulator 12. Further, as the outer conductor 41, metal plating formed by plating a metal such as copper can also be used.

According to the foamed electric wire 10a, even if the thickness of the foamed insulator 12 is reduced, the variation in the dielectric constant of the foamed insulator 12 (that is, the variation in the characteristic impedance) can be suppressed, so that a high-speed signal can be propagated. A coaxial cable with a small diameter can be realized while suppressing transmission loss.

The foamed electric wire 10a can be applied to a cable responsible for transmitting a large amount of data, for example, a probe cable used in an ultrasonic diagnostic apparatus. In the above-mentioned probe cable, hundreds of coaxial cables are bundled into a cable, and by using the foamed electric wire 10a as the coaxial cable, the entire probe cable can be reduced in diameter, easily bent, easy to handle, and small. It is possible to realize a probe cable that can propagate high-speed signals with transmission loss.

(Actions and effects of embodiments)
As described above, in the foamed electric wire manufacturing apparatus 1 according to the present embodiment, the base 22 serves as a bubble growth portion formed in a tapered shape in which the inner peripheral surface 22b gradually expands in the extrusion direction at the extrusion outlet. 22a, and the inner peripheral surface 22b of the tapered portion 22a has a bubble nucleation portion 23 formed by forming a plurality of convex portions 23a and / or concave portions 23b for bubble nucleation. While generating the bubble nuclei 13a in the generating portion 23, the bubble nuclei 13a are pushed out by the flow of the resin, and the bubble nuclei 13a are grown in accordance with the decrease in the resin pressure in the tapered portion 22a to be formed in the foam insulator 12. It is configured to form bubbles 13.

With this configuration, the bubble nucleation unit 23 can intermittently generate bubble nuclei 13a, and the bubbles 13 can be uniformly formed in the foam insulator 12 in the longitudinal direction of the foamed electric wire 10. Become. As a result, even when the thickness of the foamed insulator 12 is reduced to 100 μm or less, the variation in the dielectric constant in the longitudinal direction of the foamed insulator 12 is reduced, and the transmission loss when transmitting a high-speed signal is small. It becomes possible to manufacture the foamed electric wire 10.

Further, since the foaming nucleating agent is not used in the present embodiment, the variation in the dielectric constant caused by the foaming nucleating agent can be suppressed to be small, and the transmission loss when transmitting a high-speed signal can be further reduced. ..

Further, when the foam nucleating agent is used as in the conventional case, there is a risk that the bubbles become too large and cause insulation failure. Therefore, it is necessary to provide an exterior material (insulating tape or the like) on the outer periphery of the foam insulator 12. In the present embodiment, since bubbles having a substantially uniform size can be stably formed, it is not necessary to provide such an exterior material, which contributes to reduction of manufacturing cost.

(Summary of embodiments)
Next, the technical idea grasped from the above-described embodiment will be described with reference to the reference numerals and the like in the embodiment. However, the respective symbols and the like in the following description are not limited to the members and the like in which the components in the claims are specifically shown in the embodiment.

[1] Foaming that forms a foamed insulator (12) on the outer periphery of a central conductor (11) by extruding and foaming a resin (3) from an extrusion mold (2) having a core metal (21) and a mouthpiece (22). In the electric wire manufacturing apparatus (1), the mouthpiece (22) has a bubble growth portion (22a) formed in a tapered shape in which the inner peripheral surface (22b) gradually expands in the extrusion direction at the extrusion outlet. The inner peripheral surface (22b) of the bubble growth portion (22a) is provided with a bubble nucleation generation portion (23) formed by forming a plurality of convex portions (23a) and / or concave portions (23b) for bubble nucleation generation. Then, while generating the bubble nuclei (13a) in the bubble nucleation generation section (23), the bubble nuclei (13a) are pushed out by the flow of the resin, and the resin pressure in the bubble growth section (22a) is reduced. A foamed electric wire manufacturing apparatus (1) configured to grow the core (13a) of the bubble to form the bubble (13) in the foamed insulator (12).

[2] The bubble nucleation portion (23) is formed by forming both a convex portion (23a) and a concave portion (23b) on the inner peripheral surface (22b) of the bubble growth portion (22a) [1]. The foamed electric wire manufacturing apparatus (1).

[3] The foamed electric wire manufacturing apparatus according to [2], wherein the bubble nucleation unit (23) is formed so that a convex portion (23a) and a concave portion (23b) are adjacent to each other in the extrusion direction. 1).

[4] The height of the convex portion (23a) from the inner peripheral surface (22b) of the bubble growth portion (22a) and the depth of the concave portion (23b) from the inner peripheral surface (22b) of the bubble growth portion (22a). The foamed electric wire manufacturing apparatus (1) according to [2] or [3], wherein the sum of the sums is 20 μm or more.

[5] Any one of [1] to [4], wherein the bubble nucleation unit (23) is formed with a plurality of convex portions (23a) or concave portions (23b) at equal intervals in the circumferential direction. The foamed electric wire manufacturing apparatus according to (1).

[6] Foaming that forms a foamed insulator (12) on the outer periphery of a central conductor (11) by extruding and foaming a resin (3) from an extrusion mold (2) having a core metal (21) and a mouthpiece (22). In the method for manufacturing an electric wire, the mouthpiece (22) has a bubble growth portion (22a) formed in a tapered shape in which an inner peripheral surface (22b) gradually expands in the extrusion direction at its extrusion outlet, and the bubble growth The inner peripheral surface (22b) of the portion (22a) has a bubble nucleation generation portion (23) formed by forming a plurality of convex portions (23a) and / or concave portions (23b) for bubble nucleation generation. While generating bubble nuclei (13a) in the bubble nucleation generation section (23), the bubble nuclei (13a) are extruded by the flow of resin, and the bubbles match the decrease in resin pressure in the bubble growth section (22a). A method for manufacturing a foamed electric wire, which grows a core (13a) of the above-mentioned material to form bubbles (13) in the foamed insulator (12).

[7] The method for manufacturing a foamed electric wire according to [6], wherein the resin (3) extruded from the extruded die (2) does not contain a foaming nucleating agent.

[8] A central conductor (11) and a foamed insulator (12) having a thickness of 100 μm or less that covers the outer periphery of the central conductor (11) are provided, and the foamed insulator (12) is provided along the longitudinal direction. A foamed electric wire (10) in which bubbles (13) are intermittently formed in a straight line.

Although the embodiments of the present invention have been described above, the embodiments described above do not limit the invention according to the claims. It should also be noted that not all combinations of features described in the embodiments are essential to the means for solving the problems of the invention.

The present invention can be appropriately modified and implemented without departing from the spirit of the present invention. For example, in the above embodiment, a row of uneven portions 23c arranged in the circumferential direction is formed as the bubble nucleation generation portion 23, but a plurality of rows of uneven portions 23c may be provided in the extrusion direction. Further, the convex portion 23a and the concave portion 23b may be formed on the inner peripheral surface 22b of the tapered portion 22a over the entire surface.

1 ... Foamed wire manufacturing device 10 ... Foamed wire 11 ... Center conductor 12 ... Foamed insulator 13 ... Bubble 13a ... Bubble core 2 ... Extruded die 21 ... Core metal 22 ... Base 22a ... Tapered part (bubble growth part)
22b ... Inner peripheral surface 23 ... Bubble nucleation part 23a ... Convex part 23b ... Concave part 3 ... Resin

Claims (8)

In a foamed electric wire manufacturing apparatus for forming a foamed insulator on the outer periphery of a central conductor by extruding and foaming a resin from an extrusion die having a core and a base.
The mouthpiece has a bubble growth portion formed in a tapered shape whose inner peripheral surface gradually expands in the extrusion direction at its extrusion outlet.
The inner peripheral surface of the bubble nucleation portion has a bubble nucleation portion formed by forming a plurality of convex portions and / or concave portions for bubble nucleation.
While generating bubble nuclei in the bubble nucleation part, the bubble nuclei are pushed out by the flow of resin, and the bubble nuclei are grown in accordance with the decrease in resin pressure in the bubble growth part to grow the foamed insulator. It is configured to form bubbles inside,
Foamed wire manufacturing equipment. The bubble nucleation portion is formed by forming both a convex portion and a concave portion on the inner peripheral surface of the bubble growth portion.
The apparatus for manufacturing a foamed electric wire according to claim 1. The bubble nucleation portion is formed so that the convex portion and the concave portion are adjacent to each other in the extrusion direction.
The foamed electric wire manufacturing apparatus according to claim 2. The sum of the height of the convex portion from the inner peripheral surface of the bubble growth portion and the depth of the concave portion from the inner peripheral surface of the bubble growth portion is 20 μm or more.
The foamed electric wire manufacturing apparatus according to claim 2 or 3. The bubble nucleation portion is formed by forming a plurality of convex portions or concave portions at equal intervals in the circumferential direction.
The apparatus for manufacturing a foamed electric wire according to any one of claims 1 to 4. In a method for manufacturing a foamed electric wire, which forms a foamed insulator on the outer periphery of a central conductor by extruding and foaming a resin from an extrusion die having a core and a base.
The mouthpiece has a bubble growth portion formed in a tapered shape whose inner peripheral surface gradually expands in the extrusion direction at its extrusion outlet.
The inner peripheral surface of the bubble nucleation portion has a bubble nucleation portion formed by forming a plurality of convex portions and / or concave portions for bubble nucleation.
While generating bubble nuclei in the bubble nucleation part, the bubble nuclei are pushed out by the flow of resin, and the bubble nuclei are grown in accordance with the decrease in resin pressure in the bubble growth part to grow the foamed insulator. Form bubbles inside,
Manufacturing method of foamed electric wire. The resin extruded from the extrusion die does not contain a foam nucleating agent.
The method for manufacturing a foamed electric wire according to claim 6. With the center conductor
A foam insulator having a thickness of 100 μm or less that covers the outer periphery of the central conductor is provided.
Bubbles are intermittently formed in the foamed insulator in a straight line along the longitudinal direction.
Foamed wire.

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