JP2005116380A - Thin coaxial cable and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin coaxial cable which has an excellent and stable high frequency property. <P>SOLUTION: The coaxial cable 10 comprises a center conductor 12, an insulating coating layer 14, a shield conductor 16, and a protection coating layer 18. The center conductor 12 is constructed of a stranded wire (copper wire) of circular cross section. The coating layer 14 is formed so as to cover the outer circumference of the conductor 12 and has an annular portion 20 to cover the outer circumference of the conductor 12 and three column-shape portions 22 extending radially from the annular portion 20a to the outside diameter direction. The shield conductor 16 is formed of a hollow shape compression stranded wire. The compression stranded wire is formed in hollow-shape by arranging a plurality of element wires 26 of circular cross-section on the identical circumference and by stranding each element wire 26 in one direction and passing a crimping die. At this time, the element wires 26 are, at each part of the outer periphery mutually contacting, plastic deformed and stranded, thereby, become a stable structure (arch structure) which is tightly contacted in stone wall shape, and its shape is maintained without collapsing. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a thin coaxial cable having good and stable electrical characteristics and high frequency characteristics, and a method for manufacturing the same.

  Recently, coaxial cables are being used for antenna wiring of personal digital assistants, wiring for connecting an LCD and a CPU, etc. in response to an increase in information amount and high-speed transmission. In addition, with the miniaturization and thinning of information terminals and notebook computers, coaxial cables are also required to have high performance, small diameter, and low cost.

  In general, in order to obtain a coaxial cable with good high-frequency characteristics (low transmission loss and low delay time), the dielectric constant of the electrically insulating coating layer formed between the center conductor and the outer shield layer should be as small as possible. It is important to.

  If the characteristic impedance is 50Ω (constant value), for example, by reducing the dielectric constant, the inner diameter of the shield layer (the outer diameter of the cable) can be reduced if the center conductor diameter is the same. If the inner diameter (the outer diameter of the cable) is made constant, the center conductor diameter can be increased and the transmission loss can be reduced.

  Therefore, a low dielectric constant resin such as a fluorine resin or a polyolefin resin is often used for the insulating coating layer, and foaming is often performed in order to reduce the apparent dielectric constant.

  Also, in coaxial cables, shielding characteristics are also important, not only reducing the impact on the external environment, but also reducing the transmission loss by improving the shielding effect. For example, this is made up of stranded wires. If it is wound, the outer diameter of the shield conductor may not be uniform when bent, and the characteristic impedance may vary.

  Moreover, in order to reduce the dielectric constant of the insulating coating layer, it is necessary to increase the porosity and the foaming degree. However, if these are increased (50% or more), the strength of the insulating coating layer is reduced, and the stranded wire is reduced. If the shield conductor made of braided wire is covered, it is easily deformed, and as a result, the characteristic impedance varies.

  As a method for solving such a problem, for example, Patent Document 1 discloses a coaxial cable in which an insulating coating layer has a two-layer structure of an insulating layer and a skin layer, and only the insulating layer is made of foamed resin. Proposed.

However, the coaxial cable disclosed in Patent Document 1 has a technical problem described below.
JP 2000-48653 A

  That is, in the coaxial cable disclosed in Patent Document 1, since the insulating coating layer has a two-layer structure, the manufacturing apparatus becomes complicated and the cost increases. In general, the shield effect of a coaxial cable is higher for a shield conductor of a braided structure than for a shield conductor of a stranded wire structure, but the shield conductor of this structure has a problem that the braiding speed is low and the cost is increased. It was.

  The present invention has been made in view of such conventional problems, and an object of the present invention is to obtain a thin coaxial cable having a good and stable high-frequency characteristic and a method for producing the same without increasing the cost. And

  In order to achieve the above object, the present invention provides a thin coaxial cable comprising a central conductor, an insulating coating layer covering an outer periphery of the central conductor, and a shield conductor covering an outer periphery of the insulating coating layer. The conductor is composed of a compression stranded wire in which a plurality of strands are arranged along the outer periphery of the insulating coating layer, and a part of the outer periphery of the strands in contact with each other is plastically deformed to form a hollow shape. .

  According to the thin coaxial cable configured in this way, the compression stranded wires are formed in a hollow shape by plastic deformation of the outer circumferences of the strands that are in contact with each other. Since the stable structure (arch structure) in close contact with the stone wall shape is taken, the inside of the stranded wire is hollow.

  A thin coaxial cable is obtained by providing an insulation-coated conductor having the outer diameter of the center conductor covered with an insulation coating layer in such a compression stranded wire and having an outer dimension substantially the same as the hollow inner diameter. The coaxial cable with a simple structure has good shielding properties because the strands of compression stranded wires are in close contact with each other, and also has good flexibility because the strands are joined together but are not integrated Have

  A protective coating layer can be provided on the outer periphery of the shield conductor composed of compression stranded wires, and an electrically insulating thermoplastic resin can be used for the protective coating layer.

  In the small-diameter coaxial cable of the present invention, a stable hollow portion can be formed only with a compression stranded wire. Therefore, the shape of the insulation-coated conductor provided inside does not necessarily have to be a circle that contacts all the strands of the compression stranded wire. If the central conductor can be positioned at the center of the compression stranded wire, the shape thereof can be arbitrarily selected.

  Therefore, the insulating coating layer includes an annular portion that annularly covers the center conductor, and one or more columnar portions extending radially outward from the annular portion, and the compression stranded wire, The hollow part divided by the columnar part can be formed.

  The insulating coating layer includes an inner annular portion that covers an outer periphery of a central conductor, a plurality of connecting portions that extend outward from the inner annular portion, and an outer annular portion that connects the outer peripheral edges of the connecting portions. And the circumferential direction of the gap portion defined by the inner and outer annular portions can be divided by the connecting portion.

  In addition, a structure in which a hollow pipe is twisted around the center conductor, a structure in which an insulating (porous) tape is wound, or a structure in which insulating fibers are knitted may be used.

  The cross-sectional shape of the strand of the hollow compression stranded wire may be circular, rectangular, trapezoidal or the like. In the case of a circular shape, it is advantageous in terms of cost, but as the number increases, it may be difficult to maintain a hollow structure. In such a case, it is desirable to use a rectangular or trapezoidal shape.

  For the insulating coating layer, a low dielectric constant resin such as a fluorine resin, a polyolefin resin, a PEN (polyethylene naphthalate) resin, or an APO (cyclic polyolefin) resin excellent in dielectric constant and heat resistance can be used.

  In particular, in order to reduce loss characteristics, the insulating coating layer preferably has a hollow portion stably provided. In this case, the structure having the columnar portion described above is suitable. When providing the columnar part, it is desirable that the number is 2 to 4 and the hollowness is 50% or more.

  When the hollow ratio is 50% or less, the hollow effect is lowered. Further, the number of columnar portions may be eccentric with one, and even when the number is five or more, the eccentricity prevention effect does not change, and conversely, the hollowness decreases.

  Further, the present invention provides a method for manufacturing a small-diameter coaxial cable including a center conductor, an insulating coating layer, and a shield conductor, and an insulating coating layer is formed by extruding a synthetic resin on the outer periphery of the center conductor. A step of obtaining the insulated coated conductor, and arranging and introducing the insulated coated conductor into a central portion of a collective stranding machine such as a single twist machine via an alignment guide plate provided in front, and a plurality of strands Are arranged on the same circumference along the outer periphery of the insulating coating layer of the insulating coating conductor via the alignment guide plate, and then passed through a compression die attached to a concentrator of the collective stranding machine. However, by rotating the compression die, a part of the outer circumferences of the strands that are in contact with each other is plastically deformed to form a hollow compressed stranded wire continuously outside the insulating coated conductor. do it And a, and forming a serial shield conductor.

  In this manufacturing method, a protective coating layer can be formed of an electrically insulating synthetic resin on the outer periphery of the compression stranded wire after the shield conductor forming step.

  Generally, a stranded wire is manufactured with a single twist machine and a double twist machine. The same applies to the compression stranded wire used in the thin coaxial cable of the present invention, and a compression die is inserted during the twisting process to produce a hollow compression stranded wire.

  So, first, using a double twist machine, we tried to manufacture a coaxial cable by introducing an insulation coated conductor and a strand for compression stranded wire, but the insulation coated conductor was twisted together with the compression stranded wire, It has been found that a twist similar to that of a compression stranded wire is applied.

  In this case, when a twist is applied to the central conductor of the insulation-coated conductor, when the central conductor is a single wire, undulation occurs and the phenomenon of eccentricity occurs. In the case where the central conductor is a stranded wire, the strands were broken together with the eccentricity and the undulations of the strands. These phenomena affect the stability of the electrical characteristics and high-frequency characteristics of the coaxial cable.

  When a double twist machine is used, twisting is applied in two stages, but the compression die needs to be put in the first stage twisting process. This is because if this is put in the second stage, the variation in the length of the strands of the compression stranded wire cannot be absorbed.

  In the first-stage twisting process, the insulation-coated conductor is gripped by the compression twisted wire, and the second-stage twist is added, and the length of the compression-twisted wire in the longitudinal direction is shortened by the second-stage twisting. Since the coated conductor has a small diameter, it does not shrink as much, and a difference in length occurs. Based on this difference in compression length, undulation is generated in the insulation-coated conductor, and the strands of the compressed stranded wire are scattered, and the insulation-coated conductor is popped out at the time of cutting. Therefore, it is practically difficult to produce a long run by a production method using a double twist machine.

  The insulating coating layer includes an annular portion that covers the center conductor in an annular shape, and one or more columnar portions that extend radially outward from the annular portion, and is partitioned by a columnar portion between the compression strands. In the case of a structure that forms a hollow portion, since the twist pitch of the columnar portion and the pitch of the compression strand match, a part of the strands of the compression twisted wire falls between the columnar portions. .

  However, according to the manufacturing method of the thin coaxial cable according to the present invention configured as described above, since a single twist machine is used to twist in one step, there is a difference in length between the insulation-coated conductor and the compression stranded wire. Does not occur. For this reason, the central conductor does not have a backlash, and the insulation covered conductor does not protrude.

  The said insulation coating conductor can be supplied to the center part of the said compression die | dye, rotating in the same direction as the rotation direction of the said assembly stranding machine.

  According to this configuration, since the supply is performed while being rotated in the same direction as the rotating direction of the collective stranding machine, it is possible to prevent the insulation-coated conductor from being twisted, or to suppress it to such an extent that it does not affect even if it enters. Thus, the center conductor can be stably positioned at the center of the coaxial cable, and the characteristics can be stabilized and improved.

  Further, since the pitch of the compression stranded wire is different from the twist pitch of the insulating coated conductor, in the case of the insulating coating layer provided with the columnar portion, the strand of the compressed stranded wire does not fall between the columnar portions.

  The supply of the insulating coated conductor can be completely synchronized with the rotation of the collective stranding machine.

  According to this configuration, it is possible to prevent any twist from entering the insulating coated conductor. When the central conductor of the insulation-coated conductor is a single wire, waviness is particularly likely to occur, and it is necessary to rotate it completely synchronously.

  According to the coaxial cable and the method for manufacturing the same according to the present invention, a coaxial cable having good and stable high-frequency characteristics can be obtained.

  Hereinafter, preferred embodiments of the present invention will be described in detail based on examples.

  FIG. 1 shows a first embodiment of a thin coaxial cable 10 according to the present invention. The coaxial cable 10 shown in the figure includes a central conductor 12, an insulating coating layer 14, a shield conductor 16, and a protective coating layer 18.

  The center conductor 12 is comprised from the strand wire (copper wire) of a circular cross section, for example. The stranded wire may be a single copper wire. The insulating coating layer 14 is an electrically insulating layer formed so as to cover the outer periphery of the center conductor 12, and in the case of this embodiment, an annular portion 20 that covers the outer periphery of the center conductor 12, and the annular portion 20. And three columnar portions 22 extending radially in the radially outward direction.

  The insulating coating layer 14 is formed by extruding, for example, a fluorine-based resin such as PTFE, FEP, or PFA, or a synthetic resin such as APO (amorphous polyolefin) resin or PEN (polyethylene naphthalate) on the outer periphery of the center conductor 12. The annular portion 20 and the columnar portion 22 can be integrally formed at the same time.

  In the case of the present embodiment, the insulating coating layer 14 has three columnar portions 22 extending outward from the center, and each columnar portion 22 has a substantially cross-sectional shape that is tapered at the tip side. It is formed in a triangular shape.

  Each columnar portion 22 extends radially at equiangular intervals (120 °) in the cross section, and extends linearly along the longitudinal axis direction of the coaxial cable 10 while maintaining this interval. .

  The shield conductor 16 is provided so as to be in contact with the outer periphery of the columnar portion 22 of the insulating coating layer 14. The shield conductor 16 is partitioned in the circumferential direction by the columnar portion 22 inside the shield conductor 16, and the longitudinal direction of the small-diameter coaxial cable 10. Three gaps 24 that are continuous in the direction are provided.

In this case, three air gaps 24 are equally arranged in the circumferential direction with the center conductor 12 at the center, and in the cross section, the area ratio is relative to the area of the portion excluding the center conductor 12 and the shield conductor 16. It is desirable to occupy 50% or more.
In the present embodiment, the shield conductor 16 is formed of a hollow compression stranded wire. Such a compression stranded wire is formed in a hollow shape by arranging a plurality of strands 26 having a circular cross section on the same circumference and passing the compression dies while twisting each strand 26 in one direction. .

  At this time, the strands 26 are plastically deformed and part of the outer circumferences in contact with each other are twisted, so that they form a stable structure (arch structure) in close contact with the stone wall, The shape is maintained without breaking.

  The protective coating layer 18 is provided so as to cover the outer periphery of the shield conductor 16, but the protective coating layer 18 is not necessarily provided, but when it is provided, it is the same as the insulating coating layer 16. For example, a fluorine-based resin such as FEP or PFA, or a synthetic resin such as amorphous polyolefin resin or PEN (polyethylene naphthalate) can be formed by extrusion molding on the outer periphery of the shield conductor 16. Note that the outermost diameter of the coaxial cable 10 of the present embodiment can be 1 mm or less.

  According to the coaxial cable 10 configured as described above, the three gap portions 24 that are continuous in the longitudinal direction are provided inside the shield conductor 16, so that the dielectric constant (between the center conductor 12 and the shield conductor 16 ( Equivalent dielectric constant) can be reduced.

  Further, in the coaxial cable 10 of the present embodiment, the shield conductor 16 is composed of a compression stranded wire, and the stranded wire has good shielding characteristics because the strands 26 are in close contact with each other. Although the strands 26 are joined to each other, they are not integrated with each other, and therefore have good flexibility.

  FIG. 2 shows a second embodiment of a thin coaxial cable according to the present invention. The same or corresponding parts as those in the above embodiment are designated by the same reference numerals and the description thereof is omitted. Only the point will be described.

  Similar to the first embodiment, the small-diameter coaxial cable 10a shown in the figure includes a center conductor 12a, an insulating coating layer 14a, and a shield conductor 16a. In the case of the present embodiment, the central conductor 12a and the shield conductor 16a are substantially the same as in the first embodiment, and in particular, the shield conductor 16a is a compression twist composed of a plurality of strands 26a as in the first embodiment. Each of the strands 26a is composed of a wire, and a part of the outer periphery that is in contact with each other is plastically deformed, twisted, and in close contact with a stone wall shape to form a stable structure (arch structure) It has become.

  The insulating coating layer 14a is an electrically insulating layer formed so as to cover the outer periphery of the center conductor 12a. For example, the insulating coating layer 14a is a fluorine-based resin such as PTFE, FEP, or PFA, or APO (amorphous polyolefin) resin, PEN ( A synthetic resin such as polyethylene naphthalate is extruded on the outer periphery of the center conductor 12a in an annular shape.

  Even in the coaxial cable 10a configured as described above, the shield conductor 16a is formed of a compression stranded wire, and the strand wire 26a is in close contact with each other. Although the wires 26a are joined to each other, they are not integrated with each other, and thus have good flexibility.

  FIG. 3 shows a third embodiment of the thin coaxial cable according to the present invention. The same or corresponding parts as those in the above embodiment are designated by the same reference numerals and the description thereof is omitted. Only the point will be described.

  Similar to the first embodiment, the small-diameter coaxial cable 10b shown in the figure includes a center conductor 12b, an insulating coating layer 14b, and a shield conductor 16b. In the case of the present embodiment, the center conductor 12b and the shield conductor 16b are substantially the same as in the first embodiment, and in particular, the shield conductor 16b is a compression twist composed of a plurality of strands 26b as in the first embodiment. Each of the strands 26b is composed of a wire, and a part of the outer periphery that is in contact with each other is plastically deformed, twisted, and in close contact with a stone wall shape to form a stable structure (arch structure) It has become.

  The insulating coating layer 14b is formed by extrusion molding of a synthetic resin as in the first embodiment, and includes an inner annular portion 140b that covers the outer periphery of the center conductor 12b, and a plurality of couplings that extend outward from the inner annular portion 140b. Part 141b and outer annular part 142b for coupling the outer peripheral edge of connecting part 141b, and configured to divide the circumferential direction of gap 24b defined by inner and outer annular parts 140b and 142b by connecting part 142b. doing.

  In the case of the present embodiment, the connecting portion 141b is composed of three pieces, and the three connecting portions 141b extend radially outward from the center at equal angular intervals. In the third embodiment configured as described above, the same effects as those of the first embodiment can be obtained.

  FIG. 4 shows a fourth embodiment of a thin coaxial cable according to the present invention. The same or corresponding parts as those in the above embodiment are designated by the same reference numerals and the description thereof is omitted. Only the point will be described.

  Similar to the first embodiment, the small-diameter coaxial cable 10c shown in the figure includes a center conductor 12c, an insulating coating layer 14c, and a shield conductor 16c. In the case of the present embodiment, the center conductor 12c and the shield conductor 16c are substantially the same as in the first embodiment, and in particular, the shield conductor 16c is a compression twist composed of a plurality of strands 26c as in the first embodiment. Each of the strands 26c is composed of a wire, and a part of the outer periphery in contact with each other is plastically deformed, twisted, and in close contact with a stone wall shape to form a stable structure (arch structure) It has become.

  In this embodiment, the insulating coating layer 14c covering the outer periphery of the center conductor 12c is composed of five hollow pipes 140c, and these numbers of hollow pipes 140c are twisted around the outer periphery of the center conductor 12c. Has been established. In the fourth embodiment configured as described above, substantially the same effect as that of the first embodiment can be obtained.

  Next, the manufacturing method of the thin coaxial cable concerning this invention is demonstrated based on a specific Example.

Example 1

  Manufacturing method of coaxial cable 10 of Example 1 shown in FIG.

  The manufacturing method described below is a specific example when the coaxial cable 10 having the cross-sectional shape shown in FIG. 1 is manufactured. In this manufacturing method, first, the insulating coated conductor 30 having the cross-sectional shape shown in FIG. 5 is manufactured. The

  The insulation-coated conductor 30 is formed by twisting seven silver-plated copper wires each having a thickness of 0.068 mm as the central conductor 12, which is led to a crosshead die and passed through a nozzle having a predetermined shape. The insulating coating layer 14 is formed by extrusion coating of FEP resin (NP-100: trade name, manufactured by Daikin Industries, Ltd., relative dielectric constant 2.1) at an extrusion temperature of 350 ° C. while taking over at a rate of min. .

  In this case, cooling after coating was not particularly performed. The cross-sectional shape after the coating is a shape in which an annular portion 20 and three columnar portions 22 are provided on the outer periphery of the central conductor 12, and the (average) thickness of the columnar portions 22 is 0.06 mm, and the apex of the columnar portions 22. The ratio of the void portion occupied between the virtual circle having the outer diameter of 0.47 mm, the outer diameter of the central conductor 12 and the virtual circle connecting the apexes of the columnar portions 22 was 70%. The insulating coated conductor 30 produced as described above was wound around the core bobbin 32.

  Next, the formation process of the shield conductor 16 by the compression strand wire was performed using the single twist type collective strand wire machine 34 and the twist back machine 46. FIG. 6 is an explanatory view showing the state of processing at this time.

  The collective stranding machine 34 is provided with a swivel portion 38 provided with a compression die 36 at a leading end of the concentrator, a winding bobbin 40, and a traverse mechanism 42 of the winding bobbin 40, and in front of the compression die 36. An alignment guide plate 44 is provided.

  In the alignment guide plate 44, an insertion hole 44a of the insulating coated conductor 30 is formed in the center, and a plurality of insertion holes 44b of the element wire 26 are formed in the periphery thereof. In addition, a twister 46 is installed in front of the alignment guide plate 44, and the core bobbin 32 around which the insulation-coated conductor 30 is wound is attached to the twister 46.

  When forming the compression stranded wire on the outer periphery of the insulation coated conductor 30, as shown in FIG. 6, the insulation coated conductor 30 unwound from the core bobbin 32 is placed at the center of the compression die 36 via the alignment guide plate 44. The tip is fixed to the take-up bobbin 40 by being inserted.

  At the same time, the plurality of strands 26 are inserted into the outer periphery of the compression die 36 via the alignment guide plate 44. In this state, the collective stranding machine 34 is driven to turn the turning unit 38 in a predetermined direction.

  At this time, the insulating coated conductor 30 is supplied to the central portion of the alignment guide plate 44 while being rotated by the untwisting machine 46 in the same direction as the turning direction (twisting direction) of the turning portion 38 at a rotation speed of 700 rpm. .

  As the strand 26, 16 silver-plated copper wires having an outer diameter of 0.117 mm are used and arranged in an annular shape on the outer periphery of the alignment guide plate 44. The shield conductor 16 is formed by a compression twisted wire having an outer diameter of 0.70 mm and an inner diameter of 0.47 mm while being compressed by passing through a compression die 36 having a diameter of 0.69 mm and twisted at Pt 6.2 mm (700 rpm). did. The winding speed of the winding bobbin 40 was 4.4 m / min.

  The compression die 36 is provided with a taper from the entrance to the back side, and the strands 26 inserted into the compression die 36 move closer to each other as they move to the back side. By gradually plastically deforming and closely adhering to each other, by turning the swivel portion 38 in this state, twist is added, and such a form is continuously formed.

  Next, the obtained intermediate is guided to a crosshead die, and FEP resin (NP-100: trade name, manufactured by Daikin Industries) is coated with a thickness of 0.05 mm with a round die while taking it at a take-up speed of 15 m / min. Thus, the protective coating layer 18 was formed, and the coaxial cable 10 having a final outer diameter of 0.80 mm shown in FIG. 1 was obtained.

  When the obtained coaxial cable 10 was disassembled and the twist pitch of the insulating coating layer 14 was measured, it was found that there was no twist at all. Furthermore, as a result of investigating the degree of variation of the center conductor 12 in the longitudinal direction, there was no place where seven of the center conductors 12 were scattered.

  Moreover, even if it cut | disconnects as short as about 200 mm, the malfunction that the insulation coating conductor 30 protrudes did not generate | occur | produce. The obtained coaxial cable 10 was connected to a network analyzer, and high frequency characteristics were evaluated. The transmission loss value at a frequency of 3 GHz was 3.2 dB / m, and the VSWR was 1.1, showing good characteristics.

  In order to confirm the effect of the manufacturing method of this specific example, a coaxial cable was manufactured by the following procedure (comparative example).

Comparative Example 1

  An insulation coated conductor 30 was prepared and used in the same manner as in Example 1. Shielding with compression stranded wire was performed using a double twist type collective stranded wire machine. The insulation-coated conductor 30 was supplied from the creel stand as it is (without the untwisting machine 46) to the central portion of the alignment guide plate 44. Sixteen silver-plated copper wires having an outer diameter of 0.117 mm are fed out and arranged in an annular shape on the outer periphery of the compression die. The shield conductor 16 was formed with a compression strand having an outer diameter of 0.70 mm and an inner diameter of 0.47 mm while being compressed by passing through a compression die having a diameter of 0.69 mm and twisting at a Pt of 3.5 mm (700 rpm). The speed was 4.9 m / min.

  In addition, when the twist pitch (6.2 mm) is set similarly to the specific example 1 (speed 8.7 m / min), the compression die is allowed to pass at the time of the first stage twist, and the twist pitch at this time is 12.4 mm. Due to the long length, compression stranded wires could not be formed.

  Next, the obtained intermediate is guided to a crosshead die, and FEP resin (NP-100: trade name, manufactured by Daikin Industries) is coated with a thickness of 0.05 mm with a round die while taking it at a take-up speed of 15 m / min. Thus, a coaxial cable having a final outer diameter of 0.80 mm was obtained.

  When the obtained coaxial cable was disassembled and the twist pitch of the insulating coated conductor 30 was measured, it was found that a twist of about 3.5 mm pitch was included. Further, as a result of examining the degree of variation of the central conductor 12 in the longitudinal direction, the locations where the seven central conductors 12 were scattered were continuous.

  When this cable was cut to about 200 mm, the insulation coated conductor 30 and the length of the compression stranded wire were different, and the insulation coated conductor 30 sometimes protruded. As a result of connecting the obtained cable to a network analyzer and evaluating the high frequency characteristics, the transmission loss at a frequency of 3 GHz was 4.3 dB / m, and the VSWR was 1.3, which was inferior to that of Example 1.

Comparative Example 2

  An insulation coated conductor 30 was prepared and used in the same manner as in Example 1. Shielding with compression stranded wires was performed using a double twist type collective stranded wire machine and a rotation feeder.

  The insulating coated conductor 30 was supplied to the central portion of the alignment guide plate while rotating at 700 rpm in the same direction as the twisted direction of the compression stranded wire. Sixteen tin-plated copper wires having an outer diameter of 0.117 mm are fed out and arranged in an annular shape on the outer periphery of the alignment guide plate. The shield conductor 16 was formed with a compression strand having an outer diameter of 0.70 mm and an inner diameter of 0.47 mm while being compressed by passing through a compression die having a diameter of 0.69 mm and twisting at a Pt of 3.5 mm (700 rpm). The speed was 4.9 m / min.

  Next, the obtained intermediate is guided to a crosshead die, and FEP resin (NP-100: trade name, manufactured by Daikin Industries) is coated with a thickness of 0.05 mm with a round die while taking it at a take-up speed of 15 m / min. As a result, a coaxial cable having a final outer diameter of 0.80 mm as shown in FIG. 1 was obtained.

  The obtained coaxial cable was disassembled and the twist pitch of the insulating coating layer 14 was measured. As a result, there was a twisted portion, and the pitch was not stable. Furthermore, as a result of investigating the degree of variation of the center conductor 12 in the longitudinal direction, the locations where seven of the center conductors 12 were scattered were continuous. Moreover, when it cut | disconnects about 200 mm short, the insulation coating conductor 30 protruded, and the protrusion amount increased from the comparative example 1. FIG.

  The obtained cable was connected to a network analyzer to evaluate high frequency characteristics. The transmission loss value at a frequency of 3 GHz was 4.6 dB / m, and the VSWR was 1.35, which was inferior to that of the first specific example.

Example 2

  Manufacturing method of coaxial cable 10a of Example 2 shown in FIG.

  A stranded wire formed by twisting seven 0.055-mm silver-plated copper wires was used as the central conductor 12a. FEP resin (NP-100: trade name, manufactured by Daikin Industries, relative dielectric constant) at an extrusion temperature of 350 ° C. while guiding this to a crosshead die, passing through a round nozzle and taking it up at a take-up speed of 11 m / min. 2.1) was extruded to form an insulating layer coating layer 14a on the outer periphery of the central conductor 12, and a circular insulating coating conductor 30a having an outer diameter of 0.47 mm was obtained.

  Next, shield processing by compression stranded wire was performed in the same manner as in Example 1 except that the single twist type collective stranded wire machine 34 shown in FIG. 6 was used and the untwisting machine 46 was not used.

  In this case, the insulating coated conductor 30a was supplied to the central portion of the alignment guide plate 44 without rotating. Sixteen silver-plated copper wires (element wire 26 a) having an outer diameter of 0.117 mm are fed out and arranged in an annular shape on the outer periphery of the alignment guide plate 44. The shield conductor 16a was formed with a compression stranded wire having an outer diameter of 0.70 mm and an inner diameter of 0.47 mm while being compressed by passing through a compression die 36 having a diameter of 0.69 mm and being twisted at Pt 6.2 mm (700 rpm). The speed was 4.4 m / min.

  Next, the obtained cable is guided to a crosshead die, and FEP resin (NP-100: trade name, manufactured by Daikin Industries) is coated with a thickness of 0.05 mm with a round die while being drawn at a take-up speed of 15 m / min. A coaxial cable 10a having a final outer diameter of 0.80 mm having a cross-sectional structure shown in FIG.

  As a result of disassembling the obtained coaxial cable 10a and examining the degree of variation of the central conductor 12a in the longitudinal direction, there was no place where seven of the central conductors 12a were scattered. Further, the insulating coated conductor 30a did not protrude even when cut to about 200 mm. The obtained cable was connected to a network analyzer to evaluate high frequency characteristics. The transmission loss value at a frequency of 3 GHz was 4.3 dB / m, and the VSWR was 1.1.

  Next, the flexibility of the cable was evaluated by the following method. A cable cut to a length of 30 mm was placed on a frame with a spacing of 10 mm, a jig with a diameter of 2.9 mm was hooked and pulled downward at a speed of 10 mm / min, and the maximum load was measured. An outline of the measurement method is shown in FIG. As a result, the maximum load was about 90 g. It turned out that it showed sufficient flexibility without making a great difference from Comparative Example 3 to be described later, which is a horizontal winding shield of a general copper wire.

Comparative Example 3

  An insulation coated conductor 30a was prepared and used in the same manner as in Example 2. Next, using a single twist type collective stranding wire machine, 24 0.071 mm silver-plated copper wires are arranged on the outer periphery of the insulating coated conductor 30a, the pitch is 6.0 mm, a compression die is not used, and the speed is 4.4 m. Shielding was performed at a speed of / min.

  Next, the obtained cable is guided to a crosshead die, and FEP resin (NP-100: trade name, manufactured by Daikin Industries) is coated with a thickness of 0.05 mm with a round die while being drawn at a take-up speed of 15 m / min. A coaxial cable having a final outer diameter of 0.712 mm was obtained.

  The obtained cable was connected to a network analyzer to evaluate high frequency characteristics. The transmission loss value at a frequency of 3 GHz was 4.7 dB / m and the VSWR was 1.1, which was about 10% worse than the specific example 2. This seems to be because the crosstalk characteristic was deteriorated and the transmission loss was deteriorated because the shield was not a compression strand.

  Further, the flexibility of the cable was evaluated in the same manner as in Example 2. The maximum load was about 80 g.

  The thin coaxial cable according to the present invention and the manufacturing method thereof can be obtained without increasing the cost of a thin coaxial cable having good and stable high frequency characteristics, and can be effectively used for wiring of a portable terminal. it can.

It is sectional drawing which shows Example 1 of the small diameter coaxial cable concerning this invention. It is sectional drawing which shows Example 2 of the thin coaxial cable concerning this invention. It is sectional drawing which shows Example 3 of the small diameter coaxial cable concerning this invention. It is sectional drawing which shows Example 4 of the thin coaxial cable concerning this invention. It is sectional drawing which shows an example of the insulation coating conductor used with the manufacturing method of the thin coaxial cable concerning this invention. It is explanatory drawing of the single twist type collective stranding machine used with the manufacturing method of the thin coaxial cable concerning this invention. It is explanatory drawing of the flexibility measuring method of the small diameter coaxial cable concerning this invention.

Explanation of symbols

10, 10a, 10b, 10c Thin coaxial cable 12, 12a, 12b, 12c Center conductor 14, 14a, 14b, 14c Insulation coating layer 16, 16a, 16b, 16c Shield conductor 18 Protective coating layer

Claims (10)

In a thin coaxial cable comprising a center conductor, an insulating coating layer covering the outer periphery of the central conductor, and a shield conductor covering the outer periphery of the insulating coating layer,
The shield conductor is a compression stranded wire in which a plurality of strands are arranged along the outer periphery of the insulating coating layer, and a part of the outer periphery of the strands in contact with each other is plastically deformed to form a hollow shape. A small-diameter coaxial cable characterized by comprising.   The thin coaxial cable according to claim 1, wherein a protective coating layer is provided on an outer periphery of the shield conductor. The insulating coating layer includes an annular portion that annularly covers the center conductor, and one or more columnar portions that extend radially outward from the annular portion,
The small-diameter coaxial cable according to claim 1 or 2, wherein a hollow portion divided by the columnar portion is formed between the compression stranded wires. The insulating coating layer includes an inner annular portion that covers an outer periphery of a central conductor, a plurality of connecting portions that extend outward from the inner annular portion, and an outer annular portion that joins the outer peripheral edges of the connecting portions. Prepared,
3. The small-diameter coaxial cable according to claim 1, wherein a circumferential direction of a gap portion defined by the inner and outer annular portions is divided by the connecting portion.   5. The insulating coating layer according to claim 1, wherein a low dielectric constant resin such as fluorine resin, polyolefin resin, PEN (polyethylene naphthalate) resin, or APO (cyclic polyolefin) resin is used. Thin coaxial cable.   4. The thin coaxial cable according to claim 3, wherein the insulating coating layer has 2 to 4 columnar portions and a hollowness of 50% or more. In the manufacturing method of the small-diameter coaxial cable constituted by the center conductor, the insulating coating layer, and the shield conductor,
A step of obtaining an insulating coated conductor formed by extruding a synthetic resin and forming an insulating coating layer on the outer periphery of the central conductor;
The insulating coated conductor is arranged and introduced into the central portion of a collective stranding machine such as a single twist machine through an alignment guide plate provided in the front,
After arranging a plurality of strands equally on the same circumference along the outer periphery of the insulating coating layer of the insulating coating conductor via the alignment guide plate,
By rotating the compression die while passing the compression die attached to the concentrator of the assembly stranding machine, a part of the outer circumferences of the strands in contact with each other was plastically deformed to form a hollow shape. Forming the shield conductor by continuously forming a compression stranded wire on the outside of the insulation-coated conductor; and
A method for producing a thin coaxial cable, comprising:   8. The method of manufacturing a thin coaxial cable according to claim 7, wherein a protective coating layer is formed of an electrically insulating synthetic resin on the outer periphery of the compression stranded wire after the step of forming the shield conductor.   9. The method of manufacturing a small-diameter coaxial cable according to claim 7, wherein the insulation-coated conductor is supplied to the central portion of the compression die while being rotated in the same direction as the rotation direction of the collective stranding machine. .   The method for manufacturing a thin coaxial cable according to claim 9, wherein the supply of the insulation-coated conductor is completely synchronized with the rotation of the collective stranding machine.

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