WO2011007635A1

WO2011007635A1 - Hollow-core-body for transmission cable, manufacturing method thereof, and signal transmission cable

Info

Publication number: WO2011007635A1
Application number: PCT/JP2010/059898
Authority: WO
Inventors: 晴士田中; 繁宏松野; 雅也末守; 賢原田
Original assignee: 宇部日東化成株式会社
Priority date: 2009-07-15
Filing date: 2010-06-11
Publication date: 2011-01-20
Also published as: JP5255529B2; JP2011023205A

Abstract

Provided is a hollow-core-body for transmission cables, a manufacturing method thereof, and a signal transmission cable, wherein the degree of electrical hollowness is high, mechanical strength (especially side-pressure strength) is excellent, and production of the cable can be conducted with stability. An insulation sheathing body (2) is composed of an inner-circular section (2a), multiple rib sections (2b) extending radially from this inner-circular section (2a), and an outer-circular section (2c) that connects the outer ends of the rib sections (2b), and is also provided with three or more gap sections (2d) surrounded by the inner-circular section (2a), the outer-circular section (2c), and each of the rib sections (2b). The hollow core body (10, 11), which has the insulation sheathing body (2) installed around the circumference of an inner conductor (1, 3), has the thickness of the inner-circular section (2a) made to be in a range of 1-4% of the outer circumference of the insulation sheathing body, and also made to be thinner than the rib sections (2b) and the outer-circular section (2c).

Description

Hollow core body for transmission cable, manufacturing method thereof, and signal transmission cable

The present invention relates to a hollow core body used for various transmission cables such as a coaxial cable, a manufacturing method thereof, and a signal transmission cable using the core body. More specifically, the present invention relates to a technique for improving the mechanical strength of a hollow core body.

In recent years, with the increase in the speed of digital data transmission, a signal transmission cable having a smaller diameter, a higher transmission speed, and a low loss has been demanded. In particular, in a cable having a high operating frequency, the dielectric loss of an insulating portion (insulating covering) provided around the inner conductor greatly affects its characteristics. Thus, conventionally, coaxial cables have been proposed in which a dielectric loss is reduced by providing a gap in the insulating covering (see, for example, Patent Documents 1 to 3).

In these coaxial cables described in Patent Documents 1 to 3, a hollow core body having a gap continuous in the longitudinal direction is used. This hollow core body is a core body in which an insulating covering is formed of a foamable resin. Compared to the above, it is possible to realize a transmission cable having a high hollow ratio and good high-frequency electrical characteristics. Moreover, such a hollow core body can be formed by, for example, extruding a thermoplastic insulating resin having a small dielectric constant and tan δ around the inner conductor (see, for example, Patent Document 4). .

JP 2007-42400 A JP 2007-335393 A JP 2007-250235 A JP 2008-243720 A

However, the conventional techniques described above have the following problems. Conventional hollow core bodies include fluororesins such as PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer) and FEP (fluorinated ethylene propylene / tetrafluoroethylene / hexafluoropropylene copolymer). , Or PE (Polyethylene; Polyethylene) and other olefinic resins are used to form insulation coatings, but these resins generally have low mechanical strength (compression elastic modulus). Is easy to deform.

For this reason, even if a hollow core body having a uniform electrical property in the longitudinal direction is manufactured, in the subsequent cable manufacturing process, the core body is flattened or crushed. There is a problem that electrical characteristics such as attenuation and delay time may vary in the longitudinal direction.

In order to improve electrical characteristics such as high-frequency characteristics and delay time, it is preferable to increase the hollow ratio of the insulating coating, but if this is done, the thickness of each part constituting the insulating coating is reduced, and mechanical properties are reduced. The strength, particularly the lateral pressure strength, is reduced. For this reason, in the conventional hollow core body, in order to ensure mechanical strength, the hollow ratio of an insulation coating body must be suppressed, and there is a problem that sufficient electrical characteristics and small diameter cannot be obtained.

These problems can be solved by using a resin having a high mechanical strength such as APO (amorphous polyolefin) resin or TPX (polymethylpentene) resin and having a low dielectric constant and tan δ. None of the resins have good low-temperature (brittleness) characteristics, and are not suitable for forming an insulating coating.

On the other hand, when the structure without the inner annular portion is used as in the hollow core body described in Patent Document 3, the mechanical strength of the core body can be increased without reducing the hollowness ratio. Since the core body of a structure has few contact areas of an internal conductor and an insulation coating body, these adhesiveness is low and it is difficult to produce stably.

Therefore, the present invention provides a hollow core body for a transmission cable that has a high electrical hollowness ratio, is excellent in mechanical strength, particularly lateral pressure strength, and can be stably produced, a manufacturing method thereof, and a signal transmission cable. The main purpose.

A hollow core body for a transmission cable according to the present invention comprises an inner conductor, a thermoplastic resin, an inner annular portion covering the inner conductor, a plurality of rib portions extending radially from the inner annular portion, and the rib portions An insulating covering body configured by an outer annular portion connecting the outer ends, and the insulating covering body includes three or more void portions surrounded by the inner annular portion, the outer annular portion, and the rib portion. The thickness of the inner annular portion is 1 to 4% of the outer diameter of the insulating covering, and is thinner than the rib portion and the outer annular portion.
Here, the “thickness of the inner annular portion” in the present invention is the shortest distance from the surface of the inner conductor to the gap in the cross section perpendicular to the longitudinal direction of the hollow core body, and the measured value for each gap is an average. It is the value. In addition, the “thickness of the outer annular portion” is the shortest distance from the outer surface of the insulating covering to the gap in the cross section described above, and is a value obtained by averaging measured values for each gap. Furthermore, “the thickness of the rib portion” is the shortest distance between the adjacent gap portions across the rib portion in the cross section described above, and is a value obtained by averaging the measured values of each rib portion. In addition, the thickness of each of these parts can be measured from a micrograph obtained by photographing a cross section perpendicular to the longitudinal direction of the hollow core body by microscopic observation.
In the present invention, the thickness of the inner part that affects the electrical characteristics is thin, and the thickness of the outer part that has little effect on the electrical characteristics is thick, so the dielectric constant in the vicinity of the inner conductor is low, and Excellent mechanical strength of the core body such as compressive strength.

In this hollow core body, the thickness of the insulating covering may be increased in the order of the inner annular portion, the rib portion, and the outer annular portion.
On the other hand, the thickness of the outer annular portion can be, for example, 5 to 20% of the outer diameter of the insulating coating.
In addition, the ratio of the voids in the cross section perpendicular to the longitudinal direction is set to 20% or more, the equivalent dielectric constant is ε, and the relative dielectric constant of the thermoplastic resin constituting the insulating coating (particularly in the description below) unless, the dielectric constant of the thermoplastic resin, when the.) indicating "dielectric constant" and epsilon _0, may be an electrical hollow ratio P _e obtained by the following equation 1 in more than 45%.

Furthermore, the roundness of the outer annular portion can be, for example, 96% or more.
And as a thermoplastic resin which comprises the said insulation coating body, a fluorine resin or polyolefin resin can be used, for example.

In the method for manufacturing a hollow core body for a transmission cable according to the present invention, a center hole, an inner annular hole formed adjacent to the outer edge so as to surround the center hole, and a radial extension from the outer periphery of the inner annular hole are provided. Using a die comprising three or more linear holes wider than the inner annular hole, and an outer annular hole connecting the outer ends of the linear holes and wider than the inner annular hole; While inserting the inner conductor, the molten resin is extruded from the inner annular hole, the straight hole and the outer annular hole, and the inner annular part and a rib part extending radially from the inner annular part are provided around the inner conductor. A step of forming an insulating covering composed of an outer annular portion connecting the outer ends of the rib portion, and an inner annular portion, an outer annular portion, and a gap portion surrounded by the rib portion and continuous in the longitudinal direction. When forming the insulating covering, air for adjusting internal pressure is formed in the gap. Introduced.
In the present invention, the width of the inner annular hole for forming the inner annular portion is narrower than the linear hole forming the rib portion and the outer annular hole forming the outer annular portion, so that the periphery of the inner conductor In the insulating covering formed in (1), the thickness of the inner part that affects the electrical characteristics is thin, and the thickness of the outer part that has little influence on the electrical characteristics is thick. Thereby, a hollow core body having a high electrical hollow ratio and excellent mechanical strength, particularly lateral pressure strength, can be obtained. Moreover, since this hollow core body is provided with the inner annular part, it can be produced stably.
In this method of manufacturing a hollow core body, a die whose width is increased in the order of an inner annular hole, a straight hole, and an outer annular hole may be used.

The signal transmission cable according to the present invention uses the hollow core body described above.
In the present invention, a hollow core body having a thin inner portion that affects electrical characteristics and a small outer portion thickness that has little influence on electrical characteristics is used, so that deformation in the cable manufacturing process is prevented. It is suppressed.
The signal transmission cable may be a coaxial cable. In that case, a shield layer is provided around the hollow core body.

According to the present invention, since the inner annular portion is thinner than the rib portion and the outer annular portion, the electrical hollow ratio is high, the mechanical strength, particularly the lateral pressure strength is excellent, and the production is stable. A hollow core body can be realized.

(A) And (b) is sectional drawing which shows the structural example of the hollow core body which concerns on embodiment of this invention. It is sectional drawing which shows the other structural example of the hollow core body which concerns on embodiment of this invention. It is a figure which shows the structural example of the apparatus used when manufacturing the hollow core body which concerns on embodiment of this invention. It is sectional drawing which shows arrangement | positioning of each hole in the dice | dies 22 shown in FIG. It is sectional drawing which shows the shape of a sheath core die. It is an expanded sectional view of the tip part of a sheath core die. It is a figure which shows typically the method of cooling a core body with a heating-cooling pipe.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings. Note that the present invention is not limited to the embodiments described below.

The present inventor has conducted extensive experimental research to solve the above-mentioned problems, and has obtained the following knowledge. In a transmission cable such as a coaxial cable, when an electric current flows through an inner conductor, an electric field is formed around the inner conductor. The strength of the electric field increases as the distance from the inner conductor increases, and decreases as the distance from the inner conductor increases. Therefore, in such a transmission cable, in order to improve the electrical characteristics such as attenuation, delay time and characteristic impedance, the dielectric constant in the vicinity of the inner conductor may be reduced. What is necessary is just to make the dielectric constant of the insulation coating body provided in the small.

On the other hand, in the case of a hollow core body, the dielectric constant of the insulating coating can be adjusted by changing the hollow ratio. In such an insulator, the physical hollow ratio and the electrical (effective) hollow There is a difference in rate values. The electrical (effective) hollow ratio _Pe is defined as C (pF / m) for the capacitance of the hollow core body, D (m) for the outer diameter, and d (m) for the effective outer diameter of the inner conductor. At this time, it is a value calculated by the following mathematical formula 3 based on the equivalent (effective) dielectric constant ε obtained from the following mathematical formula 2 and the dielectric constant ε ₀ of the thermoplastic resin constituting the insulating coating.

For this reason, in the hollow core body, even if the physical hollow ratio is the same as the whole core body, if the hollow ratio in the vicinity of the inner conductor is different, the electrical hollow ratio shows different values, and the electrical characteristics Will also be different. Further, the inventor found that the dielectric constant (hollow ratio) of the outer part away from the inner conductor has little influence on the electrical characteristics compared to the dielectric constant (hollow ratio) of the part near the inner conductor, and is almost ignored. I also found that it was possible.

In other words, to affect the electrical properties of the hollow core member is electrically hollow ratio P _e, the higher its value, primarily physical hollow ratio of the internal conductor vicinity of the insulating jacket (porosity ) Should be high. Therefore, in the present invention, the thickness of each part of the insulating covering that has been conventionally formed with substantially the same thickness is reviewed, the inner annular part closest to the inner conductor is made thinner than the other parts, and the outer annular part, etc. The outer part of the core body is thickened.

First, the configuration of the hollow core body according to the embodiment of the present invention will be described. FIG.1 and FIG.2 is sectional drawing which shows the structural example of the hollow core body of this embodiment. As shown in FIGS. 1 (a) and 1 (b), the

hollow core bodies

10 and 11 of this embodiment are provided with three or more gap portions 2d continuous in the longitudinal direction around the

inner conductors

1 and 3. A body 2 is provided.

The internal conductors in the

hollow core bodies

10 and 11 may be composed of a single conductor such as the internal conductor 1 shown in FIG. 1A, but may have a plurality of internal conductors 3 such as the internal conductor 3 shown in FIG. The lead wire 3a may be used, or a twisted wire structure may be used. Furthermore, for the conductive wires constituting the

inner conductors

1 and 3, for example, copper wires, copper alloy wires excellent in strength and conductivity, or plated wires whose surfaces are plated with silver or the like can be used. It is not limited, It can select from various conducting wires suitably and can be used.

On the other hand, the insulating cover 2 includes an inner annular portion 2a that covers the

inner conductors

1 and 3, a plurality of rib portions 2b that extend radially from the inner annular body 2a, and an outer annular portion 2c that connects the outer ends of the rib portions 2b. It consists of and. In this insulating cover 2, the inner annular portion 2 a and the outer annular portion 2 c are formed substantially coaxially, and the rib portions 2 b are arranged at substantially equal intervals along the circumferential direction thereof. The spaces defined by the inner annular portion 2a, the outer annular portion 2c, and the rib portions 2b are respectively void portions 2d, and each void portion 2d is in the longitudinal direction (axial direction) of the

hollow core bodies

10 and 11. It is formed continuously.

Moreover, in this insulation coating 2, the thickness of the inner annular portion 2a is made thinner than that of the rib portion 2b and the outer annular portion 2c, and the hollow ratio of the portion closer to the

inner conductors

1 and 3 is made higher than before. . In other words, the insulating cover 2 has a thin inner portion that affects the electrical characteristics and a thick outer portion that has little influence on the electrical characteristics. Thereby, the dielectric constant in the vicinity of the

inner conductors

1 and 3 can be lowered without lowering the mechanical strength of the core body such as compressive strength.

In particular, when the thickness of the insulating covering 2 is increased in the order of the inner annular portion 2a, the rib portion 2b, and the outer annular portion 2c, while maintaining good mechanical strength that can withstand the load during cable manufacture, Electrical characteristics can be improved efficiently. In this case, for example, as in the core body 12 illustrated in FIG. 2, the thickness of the rib portion 2b may be configured to increase with increasing thickness. In addition, as in the core body shown in FIGS. 1B and 2, there are cases where the thickness of each part constituting the insulating covering 2 is not uniform, but in this case, the thickness of each part is “average thickness”. Compare with each other.

The thickness of the inner annular portion 2a is such that the

inner conductors

1 and 3 can be exposed by processing such as machining or laser processing at the end processing, and the insulating covering 2 can be stably formed. Although it may be as much as possible, it is preferably 1 to 4% of the outer diameter of the insulating cover 2. If the thickness of the inner annular portion 2a is set to be less than 1% of the outer diameter of the insulating cover 2, it becomes difficult to stably form the hollow core, or the

inner conductors

1, 3 and the insulating cover 2 The adhesiveness of the material is reduced. On the other hand, if the thickness of the inner annular portion 2a exceeds 4%, a sufficient electrical hollow ratio cannot be obtained, resulting in an increase in manufacturing cost.

On the other hand, the thickness of the outer annular portion 2c is preferably 5 to 20% of the outer diameter of the insulating cover 2. If the thickness of the outer annular portion 2c is less than 5% of the outer diameter of the insulating cover 2, sufficient lateral pressure strength may not be obtained, and if it exceeds 20%, the physical hollowness of the entire core body May be small and sufficient electrical characteristics may not be obtained.

Further, the roundness of the outer annular portion 2c is desirably 96% or more. Thereby, a hollow core body having uniform electrical characteristics in the longitudinal direction can be obtained. Here, the roundness rate is a value representing how close to a perfect circle, and can be obtained by the following Equation 4. In the following mathematical formula 4, D _max is the maximum value (longest diameter) of the outer diameter of the outer annular portion 2c, and D _min is the minimum value (shortest diameter) of the outer diameter of the outer annular portion 2c. Further, c is the center value of the outer diameter of the outer annular portion 2c, and is represented by c = ( _Dmax + _Dmin ) / 2.

In the

hollow core bodies

10 and 11 of the present embodiment, the ratio of the void portion 2d in the cross section perpendicular to the longitudinal direction of the insulating coating body 2, that is, the cross-sectional area hollow ratio in the insulating coating body 2 is 20% or more, and it is desirable electrical hollow ratio P _e obtained by the equation 3 is 45% or more. The cross-sectional area hollowness defined here corresponds to the physical hollowness described above. By setting each hollow ratio of the insulating coating 2 within this range, a hollow core body excellent in both mechanical strength and electrical characteristics can be obtained.

Furthermore, in the

hollow core bodies

10 and 11 shown in FIGS. 1 (a) and 1 (b), six rib portions 2b are provided and six gap portions 2d are formed, but the present invention is limited to this. Instead, the number of gaps 2d (the number of ribs 2b) may be three or more, and can be set as appropriate according to the required hollow ratio and mechanical characteristics. However, if the number of the gaps 2d (the number of the ribs 2b) exceeds 10, the physical hollow ratio becomes small and the electrical characteristics deteriorate, so the number of the gaps 2d (the number of the ribs 2b) is It is preferably 3 to 10, more preferably 4 to 8, and particularly preferably 6.

Such an insulating covering 2 can be integrally formed of a thermoplastic resin. Examples of the material include PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer), FEP (Fluorinated-Ethylene-Propylene), and PTFE (PolyTetraFluoroEthylene). Fluorine resins such as polytetrafluoroethylene; and olefin resins such as PE (Polyethylene; polyethylene) and PP (PolyPropylene; polypropylene).

Next, a method for manufacturing the hollow core body of the present embodiment will be described by taking as an example the case of manufacturing the hollow core body 10 shown in FIG. FIG. 3 is a diagram showing a configuration example of an apparatus used in the method for manufacturing a hollow core body of the present embodiment. FIG. 4 is a sectional view showing the arrangement of the holes in the die 22 used at that time. FIG. 5 is a cross-sectional view showing the shape of a sheath core die constituting the die 22, and FIG. 6 is an enlarged cross-sectional view of the tip portion thereof. 5 and 6 correspond to a cross-sectional view taken along line AA shown in FIG.

When the hollow core body 10 is manufactured, first, the insulating coating 2 made of a thermoplastic resin is formed around the inner conductor 1 by extrusion molding. Specifically, as shown in FIG. 3, the inner conductor 1 wound around a wire feeder (not shown) is drawn out by a take-up machine 20 and is extruded with a die 22 having the shape shown in FIG. Installed in the machine 21. And after covering the circumference | surroundings of the inner conductor 1 with the insulation coating body 2 which consists of the inner annular part 2a, the rib part 2b, and the outer annular part 2c, the cooling part 23 is allowed to pass through, and it takes in with the take-up machine 24, insulation insulation A hollow core body 10 including the body 2 can be manufactured.

As shown in FIG. 4, the die 22 used here includes a center hole 222a, an inner annular hole 222b formed adjacent to the outer edge so as to surround the center hole 222a, and an inner annular hole 222b. A linear hole 222c extending radially from the outer periphery and an outer annular hole 222d for connecting the outer ends of the linear hole 222c are provided. This die 22 can be configured, for example, by inserting a sheath core die 22a shown in FIG. 5 into a through hole provided in the round die 22b.

As shown in FIGS. 5 and 6, the sheath core die 22 a includes a disk-shaped flange 221 and a tip convex portion 222, and a pipe 223 is inserted and fitted to the shaft core. The pipe 223 forms a central hole 222a through which the inner conductor 1 is inserted. Further, an inner annular hole 222b is formed around the center hole 222a adjacent to the outer surface of the pipe 223, and three or more linear shapes extending radially outward from the outer periphery of the inner annular hole 222b. Holes 222c are provided at substantially equal angular intervals.

Further, a gap is provided between the outer surface of the tip convex portion 222 of the sheath core die 22a and the side surface of the through hole of the round die 22b, and this gap connects the outer ends of the linear holes 222c. It becomes the outer annular hole 222d. Furthermore, an air introduction hole 222e for introducing air for adjusting the internal pressure is provided in a portion surrounded by the inner annular portion 222b, the linear hole 222c, and the outer annular hole 222d, that is, a portion forming the gap portion 2d. It has been.

And in the die | dye 22 used in this embodiment, both the linear hole 222c and the outer annular hole 222d are formed wider than the inner annular hole 222b. Thereby, the insulation coating body 2 whose thickness of the inner annular part 2a is thinner than the rib part 2b and the outer annular part 2c can be formed. In addition, by increasing the width of each hole provided in the die 22 in the order of the inner annular hole, the straight hole, and the outer annular hole, the thickness of each part constituting the insulating cover 2 is changed to the inner annular part 2a, The thickness can be increased in the order of the rib portion 2b and the outer annular portion 2c.

When a hollow core body is formed using this die 22, the inner conductor 1 is inserted into the center hole 222a while rotating, non-rotating or rotating SZ, and air for adjusting internal pressure is introduced from the air introduction hole 222e. The molten resin may be extruded from the inner annular hole 222b, the straight hole 222c, and the outer annular hole 222d. As a result, the inner annular portion 2a is formed around the inner conductor 1 by the resin extruded from the inner annular hole 222b, and three or more ribs extending radially from the inner annular portion 2a by the resin extruded from each linear hole 222c. The portion 2b is formed, and the outer annular portion 2c that connects the outer ends of the rib portions 2b is formed by the resin extruded from the outer annular hole 222d.

In the manufacturing method of the present embodiment, air is introduced into the space surrounded by the inner annular portion 222b, the linear hole 222c, and the outer annular hole 222d, that is, the gap portion 2d, through the air introduction hole 222e. Therefore, a hollow core body in which the internal pressure of each gap 2d is uniform, the roundness is high, and the shape stability is excellent is obtained. The air for adjusting the internal pressure may be an air flow that naturally occurs as the internal conductor 1 is taken, but it is desirable to positively introduce the air for adjusting the internal pressure pressurized to a predetermined pressure. .

Thereafter, the core body after the extrusion molding is cooled, and the resin constituting the insulating coating body 2 is completely solidified. As a method of cooling the core body after the extrusion molding, a water cooling method, an air cooling method, cooling by a heating / cooling pipe, and the like can be mentioned, and these can be used in combination. For example, in the case of cooling the core body by a water cooling method, a cooling tank storing cold water is provided in the cooling unit 23, and the core body after extrusion molding is immersed in the cold water in the cooling tank, thereby insulating coating body The resin constituting 2 is cooled. Moreover, when cooling by an air cooling system, the cooling part 23 is provided with an air cooling nozzle, and the resin which comprises the insulation coating body 2 is cooled by injecting cold air from an air cooling nozzle toward the core body after extrusion molding.

On the other hand, when cooling by a heating / cooling tube, the cooling unit 23 is provided with a heating / cooling tube, and the core body after extrusion molding is lower than the melting point of the resin constituting the insulating covering 2 and from room temperature (25 ° C.). It is also passed through a heating and cooling pipe heated to an arbitrary high temperature. FIG. 7 is a diagram schematically showing a method of cooling the core body by the heating / cooling tube. The configuration of the heating / cooling tube 30 is not particularly limited as long as the temperature in the tube can be controlled. For example, as shown in FIG. 7, a heater for heating is provided around the iron sleeve, and the thermoelectric tube 30 is heated. What can control the temperature in an iron sleeve by

pair

31a, 31b can be used.

And the hollow core body 10 manufactured by the process mentioned above is sent to a winding machine (not shown) via the take-up machine 24, and is wound up. In the present embodiment, the case where the hollow core body 10 having the structure shown in FIG. 1A is manufactured has been described as an example, but the same applies to the hollow core body 11 having the structure shown in FIG. It can be manufactured by the method.

As described above in detail, in the hollow core body of the present embodiment, the thickness of the inner annular portion of the insulating coating that affects the electrical characteristics is reduced, and the thickness of the outer annular portion that has less influence on the electrical characteristics. Since the thickness is increased, a higher electrical hollowness can be obtained even if the physical hollowness is equivalent to the conventional one. As a result, it is possible to reduce the dielectric constant in the vicinity of the inner conductor without lowering the mechanical strength, particularly the lateral pressure strength, so that it is possible to realize a hollow core body excellent in both electrical characteristics and mechanical strength. it can. In addition, unlike the core body described in Patent Document 3, the insulation coating body of the hollow core body of the present embodiment has a configuration including an inner annular body, and thus is excellent in production stability.

Furthermore, the hollow core body of the present embodiment can be suitably used for a signal transmission cable such as a coaxial cable. For example, by providing a shield layer around it, both the mechanical strength and the electrical characteristics can be achieved. An excellent coaxial cable can be obtained. Examples of the shield layer provided around the hollow core body include a horizontal winding shield and a braided wire shield, and a known method such as a metal vapor deposition method or a method of winding a laminate tape is also applied. can do.

Hereinafter, the effects of the present invention will be described in detail with reference to examples and comparative examples of the present invention. In this embodiment, the hollow core body (Examples 1 to 3) in which the inner annular portion of the insulating coating is thinner than the rib portion and the outer annular portion, and the conventional hollow in which the thickness of each portion of the insulating coating is the same. Core bodies (Comparative Examples 1 to 3) were prepared, and their electrical characteristics and mechanical strength (side pressure performance) were evaluated. In each of the following examples and comparative examples, the effective outer diameter d (mm) of the inner conductor is 0.94 times the measured outer diameter (mm) in the case of seven stranded wires, and is not measured in the case of a single wire. The diameter.

In addition, the “side pressure performance” of each hollow core body in Examples and Comparative Examples was evaluated by the compressive strain rate measured by the method shown below. The compression strain rate was measured using a portal compression tester RTM250 (compression load cell 50N) manufactured by Orientec. At this time, a 30 mm × 30 mm steel precision surface plate with a flat surface is used as the compression jig, and this compression jig is fixed to the tip of the compression load cell, and the crosshead of the portal type compression tester described above is used. Mounted downward on the bottom.

On the other hand, the hollow core body to be measured was installed horizontally on the bottom surface plate (plane surface) of the portal compression tester. Thereafter, the crosshead was moved and pressurized with a compression jig in the vertical direction so that a predetermined load was applied to the hollow core body. Then, after pressurizing for 60 seconds with a predetermined load, an image from the upper end to the lower end of the hollow core body was taken with a microscope (VH-7000, manufactured by Keyence Corporation) with the load applied. The distance from the upper end to the lower end in the body compression direction was measured in units of 1/1000 mm.

Further, the compressive strain rate (%) of each hollow core body is determined by the distance D ₁ (mm) from the upper end to the lower end in the compression direction in the compressed state and the outer diameter D ₀ (mm) of the uncompressed portion. Based on the above, it was obtained from the following formula 5. In the present embodiment, the measurement is performed at three locations each for the case where the rib portion 2b is arranged in the compression direction and the case where the gap portion 2d is arranged in the compression direction. The “side pressure performance” was evaluated by the average value.

Example 1
The hollow core body of Example 1 has a structure including six gap portions 2d shown in FIG. 1B, and the inner conductor 3 is a tin-plated annealed copper twist using seven conductors 3a having a diameter of 0.127 mm. A wire (measured outer diameter: 0.390 mm, effective outer diameter d: 0.367 mm) was used. Then, the inner conductor 3 was passed downward through the center hole 222a of the crosshead die 22 shown in FIGS. 4 to 6, and the insulating cover 2 was formed around the inner conductor. At that time, the temperature of the die 22 was set to 350 ° C., and the wire was sent through the die at a speed of 15 m / min. Further, PFA resin 420HPJ (dielectric constant 2.1) manufactured by Mitsui DuPont Fluorochemical Co., Ltd. was used as the resin for forming the insulating coating 2.

Subsequently, the core body after extrusion molding was gradually cooled by air cooling in an atmosphere of about 25 ° C., and then cooled in a water cooling tank. At that time, the distance between the die 22 and the water surface of the water cooling tank was set to 70 mm. The hollow core body of Example 1 obtained in this way had an average outer diameter D of 0.99 mm and a roundness of 96%. The average outer diameter D of the hollow core body is measured by measuring a fluctuation range of about 50 m over the entire circumference using a rocking type measuring instrument LS7000 from Keyence Corporation. Asked.

Moreover, when the hollow core body of Example 1 was cut and the dimensions of each part in the cross section perpendicular to the longitudinal direction were measured, the thickness of the inner annular portion 2a was 0.030 mm (3.0% of the outer diameter D). The thickness of the rib portion 2b was 0.070 mm, and the thickness of the outer annular portion 2c was 0.150 mm (15% of the outer diameter D). And from these values, the ratio of the gap 2d in the cross section perpendicular to the longitudinal direction of the insulating covering 2, that is, the cross-sectional area hollow ratio in the insulating covering 2, was found to be 26.0%.

Furthermore, when the capacitance C of the hollow core body of Example 1 was measured by a capacitance monitor CP-09 manufactured by Takikawa Engineering Co., Ltd., it was 86.5 pF / m. And it calculates | requires using Formula 2 mentioned above from the electrostatic capacitance C (pF / m) of the hollow core body of this Example 1, outer diameter D (mm), and the effective outer diameter d (mm) of the internal conductor 3. FIG. equivalent (effective) dielectric constant epsilon was, based on the dielectric constant epsilon ₀ of PFA resin constituting the insulating coating material, electrical (effective) hollow ratio P _e calculated from equation 3 described above, in 50.3% there were.

On the other hand, when the compressive strain rate was measured by applying a compressive load of 9.81 N to the hollow core body of Example 1 based on the above-described side pressure performance test method, a good result of 6.5% was obtained. It was.

(Example 2)
The hollow core body of Example 2 has a structure including six gaps 2d shown in FIG. 1A, and the inner conductor 1 has a silver-plated annealed copper wire having a diameter of 0.513 mm (measured outer diameter: 0. 0). 513 mm) was used. Then, the inner conductor 1 was passed downward through the center hole 222a of the crosshead die 22 shown in FIGS. 4 to 6, and the insulating covering 2 was formed around the inner conductor. At that time, the temperature of the die 22 was set to 350 ° C., and the inside of the die was sent at a speed of 10 m / min. Further, PFA resin 420HPJ (dielectric constant 2.1) manufactured by Mitsui DuPont Fluorochemical Co., Ltd. was used as the resin for forming the insulating coating 2.

Subsequently, the core body after extrusion molding was gradually cooled by air cooling in an atmosphere of about 25 ° C., and then cooled in a water cooling tank. At that time, the distance between the die 22 and the water surface of the water cooling tank was set to 100 mm. The hollow core body of Example 2 obtained in this way had an average outer diameter D of 1.29 mm and a roundness of 97%.

Further, when the hollow core body of Example 2 was cut and the dimensions of each part in the cross section perpendicular to the longitudinal direction were measured, the thickness of the inner annular part 2a was 0.030 mm (2.3% of the outer diameter D). ), The thickness of the rib portion 2b was 0.051 mm, the thickness of the outer annular portion 2c was 0.090 mm (7.0% of the outer diameter D), and the cross-sectional area hollowness was 57.0%. Furthermore, when the electrostatic capacitance C of the hollow core body of Example 2 was measured by the same method as that of Example 1 described above, it was 77.2 pF / m. Then, using these values, the electrical (effective) hollow ratio P _e calculated based on the equation 2 described above was 74.4%.

Further, when a side pressure performance test was performed in the same manner as in Example 1 with a compressive load of 19.62 N, a good result was obtained with a compressive strain rate of 10.3%.

(Example 3)
The hollow core body of Example 3 has a structure including six gap portions 2d shown in FIG. 1A, and the inner conductor 1 has a silver-plated annealed copper wire having a diameter of 0.513 mm (measured outer diameter: 0. 0). 513 mm) was used. Then, the inner conductor 1 was passed downward through the center hole 222a of the crosshead die 22 shown in FIGS. 4 to 6, and the insulating covering 2 was formed around the inner conductor. At that time, the temperature of the die 22 was set to 350 ° C., and the inside of the die was sent at a speed of 10 m / min. Further, PFA resin 420HPJ (dielectric constant 2.1) manufactured by Mitsui DuPont Fluorochemical Co., Ltd. was used as the resin for forming the insulating coating 2.

Subsequently, the core body after extrusion molding was gradually cooled by air cooling in an atmosphere of about 25 ° C., and then cooled in a water cooling tank. At that time, the distance between the die 22 and the water surface of the water cooling tank was set to 100 mm. The hollow core body of Example 3 obtained in this way had an average outer diameter D of 1.29 mm and a roundness of 97%.

Moreover, when the hollow core body of Example 3 was cut and the dimensions of each part in the cross section perpendicular to the longitudinal direction were measured, the thickness of the inner annular portion 2a was 0.030 mm (2.3% of the outer diameter D). The rib portion 2b had a thickness of 0.075 mm, the outer annular portion 2c had a thickness of 0.075 mm (5.8% of the outer diameter D), and the cross-sectional area hollowness was 57.6%. Furthermore, when the electrostatic capacitance C of the hollow core body of Example 3 was measured by the same method as in Example 1 described above, it was 77.5 pF / m. Then, using these values, the electrical (effective) hollow ratio P _e calculated based on the equation 2 described above was 74.0%.

Further, when a side pressure performance test was conducted in the same manner as in Example 1 with a compressive load of 19.62 N, a good result was obtained with a compressive strain rate of 9.4%.

(Comparative Example 1)
Next, as Comparative Example 1, a hollow core body was manufactured using a crosshead die having the same widths of the inner annular hole, the linear hole, and the outer annular hole. The hollow core body of this comparative example 1 has a structure with six voids as in the case of the above-described embodiment 1, and the tin conductor annealed copper using seven conductors 3a having a diameter of 0.127 mm as the inner conductor. A stranded wire (measured outer diameter: 0.390 mm, effective outer diameter d: 0.367 mm) was used.

Then, this inner conductor was passed downward through the center hole of the die, and an insulating coating was formed around it. At that time, the temperature of the die was set to 350 ° C., and the wire was fed through the die at a speed of 15 m / min. Moreover, Mitsui DuPont Fluoro Chemical Co., Ltd. PFA resin 420HPJ (dielectric constant 2.1) was used for resin which forms an insulation coating body. Subsequently, the extruded core body was gradually cooled by air cooling in an atmosphere at about 25 ° C., and then water-cooled in a water cooling tank. At that time, the distance between the die and the water surface of the water cooling tank was set to 70 mm. The hollow core body of Comparative Example 1 thus obtained had an average outer diameter D of 0.99 mm and a roundness of 96%.

Further, when the hollow core body of Comparative Example 1 was cut and the dimensions of each part in the cross section perpendicular to the longitudinal direction were measured, the thickness of the inner annular part was 0.095 mm (9.6% of the outer diameter D), The rib portion had a thickness of 0.095 mm, the outer annular portion had a thickness of 0.095 mm (9.6% of the outer diameter D), and the cross-sectional area hollowness was 27.0%.

Furthermore, when the electrostatic capacity C of the hollow core body of Comparative Example 1 was measured by the same method as in Example 1, it was 90.1 pF / m. Then, using these values, the electrical (effective) hollow ratio P _e calculated based on the formula 2 mentioned above is 44.5%, the hollow core of the Comparative Example 1, the cross-sectional area hollow ratio Compared with the hollow core body of Example 1 having the same degree, the electrical hollowness was low.

On the other hand, when the hollow core body of Comparative Example 1 was subjected to a side pressure performance test under the same method and conditions as in Example 1 (compressive load: 9.81 N), the compressive strain rate was 12.3%. Thus, the hollow core body of Comparative Example 1 was significantly inferior in lateral pressure performance as compared with the hollow core body of Example 1.

(Comparative Example 2)
Next, as Comparative Example 2, a hollow core body was manufactured using a crosshead die having the same widths of the inner annular hole, the straight hole, and the outer annular hole. The hollow core body of Comparative Example 2 has a structure including six voids as in Example 2 described above, and the inner conductor has a silver-plated annealed copper wire having a diameter of 0.513 mm (measured outer diameter: 0). .513 mm) was used.

Then, this inner conductor was passed downward through the center hole of the die, and an insulating coating was formed around it. At that time, the temperature of the die was set to 350 ° C., and the wire was fed through the die at a speed of 10 m / min. Moreover, Mitsui DuPont Fluoro Chemical Co., Ltd. PFA resin 420HPJ (dielectric constant 2.1) was used for resin which forms an insulation coating body. Moreover, Mitsui DuPont Fluoro Chemical Co., Ltd. PFA resin 420HPJ (dielectric constant 2.1) was used for resin which forms an insulation coating body.

Subsequently, the core body after extrusion molding was gradually cooled by air cooling in an atmosphere of about 25 ° C., and then cooled in a water cooling tank. At that time, the distance between the die and the water surface of the water cooling tank was set to 100 mm. The hollow core body of Comparative Example 2 thus obtained had an average outer diameter D of 1.32 mm and a roundness of 97%.

Further, when the hollow core body of Comparative Example 2 was cut and the dimensions of each part in the cross section perpendicular to the longitudinal direction were measured, the thickness of the inner annular part was 0.068 mm (5.2% of the outer diameter D), The rib portion had a thickness of 0.068 mm, the outer annular portion had a thickness of 0.068 mm (5.2% of the outer diameter D), and the cross-sectional area hollowness was 56.9%.

Furthermore, the electrostatic capacity C of the hollow core body of Comparative Example 2 was measured by the same method as in Example 1, and it was 79.4 pF / m. Then, using these values, the electrical (effective) hollow ratio P _e calculated based on the formula 2 mentioned above is 68.1% hollow core of the Comparative Example 2, the cross-sectional area hollow ratio However, compared with the hollow core bodies of Examples 2 and 3 having the same degree, the electrical hollow ratio was low.

On the other hand, when the hollow core body of Comparative Example 2 was subjected to a side pressure performance test under the same method and conditions as in Examples 2 and 3 (compressive load: 19.62 N), the compressive strain rate was 11.3%. . Thus, the hollow core body of Comparative Example 2 was inferior in lateral pressure performance as compared with the hollow core bodies of Examples 2 and 3.

(Comparative Example 3)
Next, as Comparative Example 3, a hollow core body was manufactured using a crosshead die having the same widths of the inner annular hole, the straight hole, and the outer annular hole. The hollow core body of Comparative Example 3 has a structure including six voids as in Example 3 described above, and the inner conductor has a silver-plated annealed copper wire having a diameter of 0.513 mm (measured outer diameter: 0). .513 mm) was used.

Subsequently, the core body after extrusion molding was gradually cooled by air cooling in an atmosphere of about 25 ° C., and then cooled in a water cooling tank. At that time, the distance between the die and the water surface of the water cooling tank was set to 100 mm. The hollow core body of Comparative Example 2 thus obtained had an average outer diameter D of 1.30 mm and a roundness of 97%.

Moreover, when the hollow core body of Comparative Example 3 was cut and the dimensions of each part in the cross section perpendicular to the longitudinal direction were measured, the thickness of the inner annular part was 0.055 mm (4.2% of the outer diameter D), The rib portion had a thickness of 0.055 mm, the outer annular portion had a thickness of 0.055 mm (4.2% of the outer diameter D), and the cross-sectional area hollowness was 63.7%.

Furthermore, when the electrostatic capacitance C of the hollow core body of Comparative Example 2 was measured by the same method as in Example 1, it was 76.9 pF / m. Then, using these values, the electrical (effective) hollow ratio P _e calculated based on the formula 2 mentioned above is 73.9% hollow core of the Comparative Example 3, Example 2, Compared to the hollow core body 3, the electrical hollowness was the same level despite the high cross-sectional area hollowness.

On the other hand, when the side pressure performance test was conducted on the hollow core body of Comparative Example 3 under the same method and conditions as in Examples 2 and 3 (compressive load: 19.62 N), the compressive strain rate was 14.5%. . Thus, the hollow core body of Comparative Example 2 was significantly inferior in lateral pressure performance as compared with the hollow core bodies of Examples 2 and 3.

The above results are summarized in Table 1 below.

As shown in Table 1 above, the hollow core bodies of Examples 1 to 3 in which the inner annular portion is thinner than the rib portion and the outer annular portion and is 1 to 4% of the outer diameter of the insulating coating body, Compared to the hollow core bodies of Comparative Examples 1 to 3 in which the respective outer diameters correspond to each other, the electrical hollowness was high and the mechanical strength (side pressure performance) was excellent.

DESCRIPTION OF

SYMBOLS

1, 3 Inner conductor 2 Insulation covering body 2a Inner annular part 2b Rib part 2c Outer annular part 2d Space | gap

part 3a Conductor

10, 11, 12

Hollow core body

20, 24 Take-out machine 21 Extruder 22 Dice 22a Sheath core die 22b Round Die 23 Cooling part 30 Heating /

cooling pipe

31a, 31b Thermocouple 221 Flange 222 Tip convex part 222a Center hole 222b Inner ring hole 222c Straight hole 222d Outer ring hole 222e Air introduction hole 223 Pipe

Claims

An inner conductor,
An insulating covering made of a thermoplastic resin and comprising an inner annular portion covering the inner conductor, a plurality of rib portions extending radially from the inner annular portion, and an outer annular portion connecting the outer ends of the rib portions; Have
The insulating covering includes three or more voids surrounded by an inner annular part, an outer annular part and a rib part,
A hollow core body for a transmission cable, wherein the thickness of the inner annular portion is 1 to 4% of the outer diameter of the insulating covering and is thinner than the rib portion and the outer annular portion.
The hollow core body for a transmission cable according to claim 1, wherein the thickness of the insulating covering body increases in the order of an inner annular portion, a rib portion, and an outer annular portion.
The hollow core body for a transmission cable according to claim 1 or 2, wherein the thickness of the outer annular portion is 5 to 20% of the outer diameter of the insulating coating body.
When the ratio of the voids in the cross section perpendicular to the longitudinal direction is 20% or more, the equivalent dielectric constant is ε, and the relative dielectric constant of the thermoplastic resin constituting the insulating coating is ε 0 , the following formula ( hollow core body for the transmission cable according to any one of claims 1 to 3 electrically hollow ratio P e obtained by a) is 45% or more.
The hollow core body for a transmission cable according to any one of claims 1 to 4, wherein the roundness of the outer annular portion is 96% or more.
The hollow core body for a transmission cable according to any one of claims 1 to 5, wherein the thermoplastic resin constituting the insulating covering is a fluororesin or a polyolefin resin.
A central hole, an inner annular hole formed adjacent to the outer edge so as to surround the central hole, and three or more linear holes extending radially from the outer periphery of the inner annular hole and wider than the inner annular hole; And using a die comprising an outer annular hole connected between the outer ends of the linear holes and wider than the inner annular hole,
While inserting the inner conductor through the center hole, extruding the molten resin from the inner annular hole, the straight hole and the outer annular hole,
Around the inner conductor, an inner annular portion, a rib portion extending radially from the inner annular portion, an outer annular portion connecting the outer ends of the rib portion, the inner annular portion, the outer annular portion and the rib portion Having a step of forming an insulating covering that is surrounded by a continuous void in the longitudinal direction;
A method for producing a hollow core body for a transmission cable, wherein, when forming the insulating covering, air for adjusting internal pressure is introduced into the gap.
The method for manufacturing a hollow core body for a transmission cable according to claim 7, wherein a die having a wider width in the order of an inner annular hole, a straight hole, and an outer annular hole is used.
A signal transmission cable using the hollow core body according to any one of claims 1 to 6.
The signal transmission cable according to claim 9, wherein the signal transmission cable is a coaxial cable, and a shield layer is provided around the hollow core body.