JP2017220424A - Foam coaxial cable, manufacturing method therefor and multicore cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a foam coaxial cable without breaking air bubble and generating insulation breakage even with thin foam insulation having increased form degree and thickness of 0.1 mm or less, a manufacturing method therefor and a multicore cable using the foam coaxial cable.SOLUTION: A foam coaxial cable 10 has a center conductor 1 by twisting a plurality of conductors, a foam insulation layer 2 arranged on an outer periphery of the center conductor 1, an outside conductor 4 arranged on an outer periphery of the foam insulation layer 2 and an outermost coating layer 5 arranged on an outer periphery of the outside conductor 4, the foam insulation layer 2 has a foam degree of a first zone 21 by 1/2 of thickness in a side of the center conductor 1, which is higher than foam degree of a second zone 22 which is a remaining part other than the first zone 21.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a foamed coaxial cable, a method for manufacturing the same, and a multicore cable.

  Medical cables include probe cables (for example, for ultrasonic diagnosis), catheter cables, endoscope cables, and the like, and coaxial cables are used as signal lines. For example, there is an ultrasonic diagnostic probe cable in which 192 foamed coaxial cables are assembled and a sheath is provided on the outer periphery of the aggregate.

  As a coaxial cable built in such a medical cable, a coaxial cable having a foamed insulating layer formed by foam extrusion coating on the outer periphery of a center conductor has been conventionally known (for example, see Patent Documents 1 and 2). ). By having bubbles due to foaming, the capacitance of the insulating layer can be lowered.

  The medical cable is required to have a smaller diameter along with the downsizing of the medical device, and the coaxial cable tends to have a smaller diameter (see, for example, Patent Document 3).

  When the foam insulation layer is coated on the outer periphery of the center conductor by extrusion, make the foam size of the foam insulation layer as uniform as possible and the distribution as uniform as possible to stabilize the capacitance characteristics. Yes.

JP 2004-63369 A JP 2010-212185 A JP 2007-169687 A

  Increasing the foaming degree of the foamed insulation layer increases the number of bubbles or grows large bubbles. However, if a thin foamed insulator with a thickness of 0.1 mm or less is used, the bubbles may collapse immediately, or if severe, the insulation will break. There is a problem of causing. That is, it is difficult to reduce the diameter.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a foamed coaxial cable that does not cause air bubbles to be immediately crushed or cause insulation breakage even in a thin-walled foam insulator having a thickness of 0.1 mm or less with an increased degree of foaming, and a method for manufacturing the same. Another object is to provide a multi-core cable using the foamed coaxial cable.

  In order to achieve the above object, the present invention provides the following foamed coaxial cable, a method for manufacturing the same, and a multicore cable.

[1] A central conductor formed by twisting a plurality of conductors, a foamed insulating layer provided on the outer periphery of the central conductor, an external conductor provided on the outer periphery of the foamed insulating layer, and provided on the outer periphery of the external conductor The foamed insulating layer has a foaming degree of the first region up to half the thickness on the side of the central conductor, the remaining portion other than the first region A foamed coaxial cable having a higher degree of foaming than the area 2.
[2] The foamed coaxial cable according to [1], wherein the volume of bubbles in the first region is 50% or more of the volume of bubbles in the entire foamed insulating layer.
[3] The foamed coaxial cable according to [1], wherein the volume of bubbles in the first region is 60 to 80% of the volume of bubbles in the entire foamed insulating layer.
[4] The foamed coaxial cable according to any one of [1] to [3], wherein the foamed insulating layer is an extruded coating layer provided immediately above the center conductor.
[5] The foamed coaxial cable according to any one of [1] to [4], further including a skin layer made of a non-foamed insulator provided immediately above the foamed insulating layer.
[6] A step of extrusion-coating a foamed insulating layer on an outer periphery of a central conductor obtained by twisting a plurality of conductors through a die, and the extrusion-coating step is performed in the space formed in the die. A method for producing a foamed coaxial cable, comprising: foaming a foamed insulating layer; and foaming the foamed insulating layer at a discharge hole of the die from which the central conductor is discharged.
[7] The die includes a first resin flow path provided on the center side of the die and a second resin flow path provided outside the first resin flow path. The space is provided in a portion where the resin flowing through the first resin flow channel and the central conductor passing through the die are in contact with each other, and the flow channel width is larger than the flow channel width of the first resin flow channel. The method for producing a foamed coaxial cable according to [6], wherein the foamed coaxial cable is a wide space.
[8] A cable core including one or more foamed coaxial cables according to any one of [1] to [5], and a sheath provided on an outer periphery of the cable core. Multi-core cable.
[9] The multicore cable according to [8], which is a medical cable.

  According to the present invention, even in a thin foam insulator with a thickness of 0.1 mm or less with an increased degree of foaming, a foamed coaxial cable in which bubbles are not immediately crushed or insulation breakage, a method for manufacturing the same, and the method A multi-core cable using a foamed coaxial cable can be provided.

It is a cross-sectional view which shows the structure of the foaming coaxial cable which concerns on embodiment of this invention. It is a cross-sectional view which shows the structure of the die | dye used in the manufacturing process of the foaming coaxial cable which concerns on embodiment of this invention. It is a cross-sectional view which shows the structure of the multicore cable which concerns on embodiment of this invention.

[Foamed coaxial cable]
FIG. 1 is a cross-sectional view showing the structure of a foamed coaxial cable according to an embodiment of the present invention.

  A foamed coaxial cable 10 according to the embodiment of the present invention shown in FIG. 1 includes a center conductor 1 obtained by twisting a plurality of conductors, a foam insulation layer 2 provided on the outer periphery of the center conductor 1, and a foam insulation layer. The outer conductor 4 provided on the outer periphery of the outer conductor 4 and the outermost coating layer 5 provided on the outer periphery of the outer conductor 4, and the foamed insulating layer 2 has a first thickness up to half the thickness of the central conductor 1 side. The foaming degree of the region 21 is higher than the foaming degree of the second region 22 which is the remaining part other than the first region 21.

(Center conductor 1)
The center conductor 1 may be made of a single wire, but is preferably made of a stranded wire obtained by twisting a plurality of conductors from the viewpoint of increasing the porosity between the foamed insulating layer 2. The number of conductors to be twisted is not particularly limited, but is preferably 3 or 7 from the viewpoint of increasing the porosity with the foamed insulating layer 2. In FIG. 1, seven conductors are twisted together.

  The center conductor 1 is made of, for example, a copper alloy. Plating such as silver plating may be applied. The center conductor 1 preferably has a small diameter, specifically 42 to 50 AWG (American Wire Gauge), more preferably 46 to 50 AWG, and even more preferably 48 to 50 AWG.

(Foam insulation layer 2)
The foamed insulating layer 2 is preferably an extruded coating layer provided immediately above the central conductor 1. The foam insulating layer 2 is made of, for example, a fluororesin. As the fluororesin, for example, tetrafluoroethylene / ethylene copolymer (ETFE), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), and tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA) are suitable. .

  The foamed insulating layer 2 is foamed in the second region 22 in which the foaming degree (%) of the first region 21 up to half the thickness on the central conductor 1 side is the remaining portion other than the first region 21. Higher than degree (%). Here, the degree of foaming (%) refers to the proportion of bubbles in the area of the foamed insulating layer 2 in the cross section of the foamed coaxial cable 10. That is, for example, the degree of foaming (%) of the first region 21 up to half the thickness on the side of the central conductor 1 is the first degree of foaming insulating layer 2 up to half the thickness on the side of the central conductor 1. The ratio of the area of the bubbles existing in the first region 21 in the area of the region 21 (including the resin portion and the bubble portion). In the embodiment of the present invention, it is desirable that the foaming degree of the foamed insulating layer 2 satisfies the above relationship over the entire length of the foamed coaxial cable 10 in the longitudinal direction, but the present invention is not limited to this. For example, it is preferable that the above relationship is satisfied at x / 3 or more when the degree of foaming is measured at any plurality of locations (x) in the longitudinal direction of the foamed coaxial cable 10, and the above relationship is satisfied at x / 2 or more. It is more preferable that the above relationship is satisfied at 3x / 4 or more, and it is most preferable that the above relationship is satisfied at 4x / 5 or more (rounded up after the decimal point).

  Moreover, it is preferable that the volume of the bubble of the 1st area | region 21 is 50% or more of the volume of the bubble of the whole foaming insulating layer 2, and it is 60 to 80% of the volume of the bubble of the whole foaming insulating layer 2. More preferred. Here, confirmation of whether or not the above relationship is satisfied can be replaced by measuring the area of the bubble in the cross section of the foamed coaxial cable 10 and calculating the ratio of the area. That is, the ratio of the area of the bubbles in the first region 21 to the area of the bubbles in the entire foamed insulating layer 2 in the cross section of the foamed coaxial cable 10 is preferably 50% or more, and preferably 60 to 80%. More preferred. In the embodiment of the present invention, it is desirable that the above relationship is satisfied over the entire length of the foamed coaxial cable 10 in the longitudinal direction, but the present invention is not limited to this. For example, it is preferable that the relationship is satisfied at x / 3 or more when the area of the bubble is measured at any plurality of locations (x) in the longitudinal direction of the foamed coaxial cable 10, and the above relationship is satisfied at x / 2 or more. It is more preferable that the relationship is satisfied, it is more preferable that the above relationship is satisfied at 3x / 4 or more, and it is most preferable that the above relationship is satisfied at 4x / 5 or more (rounded up after the decimal point).

  The foaming degree (%) of the first region 21 and the foaming degree (%) of the second region 22 are not particularly limited as long as the above relationship is satisfied.

  The thickness of the foamed insulating layer 2 is preferably 0.1 mm or less for the purpose of reducing the diameter of the cable. Due to the foamed insulating layer 2 having the above configuration, even in a thin foamed insulator having a thickness of 0.1 mm or less with increased foaming, the foamed coaxial does not cause air bubbles to be crushed immediately or cause insulation breakage. A cable is obtained.

(Skin Layer 3)
The foamed coaxial cable 10 is preferably provided with a skin layer 3 made of a non-foamed insulator immediately above the foamed insulating layer 2.

  The skin layer 3 is preferably formed by winding a tape, for example, by winding a polyethylene terephthalate (PET) tape, a polyetherimide (PEI) tape or a polyimide (PI) tape with a hot melt adhesive layer. It is preferable that The hot melt adhesive layer is a layer made of a hot melt adhesive that can be bonded by thermocompression bonding. The tape is preferably wound so that there is a wrap portion. The thickness of the hot melt adhesive layer is, for example, 0.5 to 2 μm, and the thickness of the tape made of each substrate is, for example, 2 to 6 μm.

  The skin layer 3 may have a tube shape, and is formed, for example, by extruding a resin selected from a fluororesin, polyethylene (PE), and polypropylene (PP). As the fluororesin, for example, tetrafluoroethylene / ethylene copolymer (ETFE), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), and tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA) are suitable. is there. The thickness of the skin layer 3 by extrusion coating is preferably 8 to 30 μm.

(Outer conductor 4)
The outer conductor 4 is, for example, a tin-plated copper wire, a tin-plated copper alloy wire, a silver-plated copper wire, or a silver-plated copper alloy wire. A large number of these (for example, 30 to 60) are wound around the outer periphery of the skin layer 3 (a foam insulating layer 2 when the skin layer 3 is not provided) in a spiral shape at a predetermined pitch.

(Outermost coating layer 5)
The outermost coating layer 5 can be provided by winding a PET tape or by extrusion coating ETFE, FEP, PFA or the like.

(Use)
The foamed coaxial cable according to the embodiment of the present invention is suitable as a coaxial cable built in a multi-core cable such as a medical cable, but can also be applied to other cables.

[Method of manufacturing foamed coaxial cable]
FIG. 2 is a cross-sectional view showing the structure of a die used in the manufacturing process of the foamed coaxial cable according to the embodiment of the present invention.

  The method for manufacturing a foamed coaxial cable according to an embodiment of the present invention includes a step of extrusion-coating the foamed insulating layer 2 on the outer periphery of the center conductor 1 through the die 100, and the step of extrusion-coating includes the step of forming the die 100. The process includes foaming the foamed insulating layer 2 in the space 104 formed therein, and foaming the foamed insulating layer 2 in the discharge hole 100a of the die 100 from which the center conductor 1 is discharged.

  As a specific configuration example of the die 100, as shown in FIG. 2, the die 100 includes a nozzle 102 having a nozzle hole 102 a inserted in the center portion of the die holder 101, and a center portion side of the die 100. A first resin flow path 101a provided along the outer wall of the nozzle 102 and a second resin flow path 101b provided outside the first resin flow path 101a are provided.

  The first resin flow path 101a and the second resin flow path 101b are divided by the flow divider 103.

  The space 104 is provided in a portion where the first resin 111 flowing through the first resin flow path 101a and the central conductor 1 passing through the nozzle hole 102a are in contact with each other, and the flow path width of the first resin flow path 101a. It is a space whose flow path width is wider than that. Foaming occurs when the first resin 111 flows into the space 104. A portion formed by the first resin 111 constitutes a portion closer to the center conductor 1 in the foamed insulating layer 2.

  Thereafter, the first resin 111 flowing through the space 104 and the second resin 112 flowing through the second resin flow path 101b join together to generate foam when discharged from the discharge hole 100a of the die 100. Layer 2 is formed.

  The first resin 111 flowing through the first resin flow path 101a and the second resin 112 flowing through the second resin flow path 101b can use the materials described above, and they are different even if they are the same. It may be a thing. The first resin 111 preferably contains a larger amount of foaming agent than the second resin 112.

  After the foam insulating layer 2 is formed, the foamed coaxial cable 10 is manufactured by providing the skin layer 3, the outer conductor 4, and the outermost coating layer 5 on the outer periphery thereof by an ordinary method.

[Multi-core cable]
The multi-core cable according to the embodiment of the present invention includes a cable core including one or more foamed coaxial cables according to the above-described embodiment of the present invention, and a sheath provided on the outer periphery of the cable core. The multicore cable is, for example, a medical cable.

  FIG. 3 is a cross-sectional view showing the structure of a probe cable that is one of the medical cables as an example of the multicore cable according to the embodiment of the present invention.

  A plurality of foamed coaxial cables (foamed coaxial cable 10) according to the embodiment of the present invention are bundled (may be bundled and twisted) to form a coaxial cable unit 11, and a plurality of the coaxial cable units 11 (in FIG. 3). 7) are bundled with a bind tape 12 made of PTFE (polytetrafluoroethylene) or the like to form a cable core, and a shield layer 13 is formed by winding or braiding a plurality of metal wires such as silver-plated copper wires around the cable core. The probe cable 20 is obtained by providing a sheath 14 made of PFA, PVC (polyvinyl chloride) or the like around the shield layer 13. The coaxial cable unit 11 preferably has a coating layer on the outer periphery of the bundled foamed coaxial cables 10.

  The medical cables other than the probe cable, that is, the catheter cable and the endoscope cable, basically have the same structure as the probe cable except that the number of the foamed coaxial cables is different. In addition, in a catheter cable, a foamed coaxial cable may be comprised only by one. In addition, a power supply line and other signal lines may be included.

  In addition, this invention is not limited to the said embodiment, A various deformation | transformation implementation is possible.

10: Foamed coaxial cable 1: Center conductor, 2: Foam insulating layer, 2a: Bubble 3: Skin layer, 4: External conductor, 5: Outermost coating layer 21: First region, 22: Second region 20: Multi-core cable (probe cable), 11: coaxial cable unit 12: bind tape, 13: shield layer, 14: sheath 100: die, 100a: discharge hole, 101: die holder 101a: first resin flow path, 101b: first 2 resin flow paths 102: nozzle, 102a: nozzle hole, 103: flow divider, 104: space 111: first resin, 112: second resin

Claims (9)

A center conductor, a foam insulating layer provided on the outer periphery of the center conductor, an outer conductor provided on the outer periphery of the foam insulating layer, and an outermost coating layer provided on the outer periphery of the outer conductor;
In the foamed insulating layer, the foaming degree of the first region up to half the thickness on the central conductor side is higher than the foaming degree of the second region which is the remaining part other than the first region. Foamed coaxial cable characterized by   2. The foamed coaxial cable according to claim 1, wherein the volume of bubbles in the first region is 50% or more of the volume of bubbles in the entire foamed insulating layer.   2. The foamed coaxial cable according to claim 1, wherein the volume of bubbles in the first region is 60 to 80% of the volume of bubbles in the entire foamed insulating layer.   The foamed coaxial cable according to any one of claims 1 to 3, wherein the foamed insulating layer is an extruded coating layer provided immediately above the central conductor.   The foamed coaxial cable according to any one of claims 1 to 4, further comprising a skin layer made of a non-foamed insulator, provided immediately above the foamed insulating layer. Having a step of extruding a foam insulating layer on the outer periphery of the center conductor through a die,
The extrusion coating step includes a step of foaming the foamed insulating layer in a space formed in the die, and a step of foaming the foamed insulating layer at a discharge hole of the die from which the center conductor is discharged. A method for producing a foamed coaxial cable. The die includes a first resin flow path provided on the center side of the die, and a second resin flow path provided outside the first resin flow path,
The space is provided in a portion where the resin flowing through the first resin flow path and the central conductor passing through the die are in contact with each other, and the flow path width is larger than the flow path width of the first resin flow path. The method for manufacturing a foamed coaxial cable according to claim 6, wherein the space is a wide space.   A multi-core cable comprising: a cable core including one or more foamed coaxial cables according to any one of claims 1 to 5; and a sheath provided on an outer periphery of the cable core. The multi-core cable according to claim 8, wherein the multi-core cable is a medical cable.

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