JP6845193B2 - Manufacturing method of leaky coaxial cable and leaky coaxial cable - Google Patents

Description

The present invention relates to a leaky coaxial cable and a method for manufacturing a leaky coaxial cable corresponding to wide FM broadcasting, V-Low multimedia broadcasting, and the like.

With the end of analog television broadcasting in 2011, attempts to use the vacant frequency band have begun.

Specifically, as a countermeasure against difficult viewing of AM radio, for example, AM radio is rebroadcast in a wide FM broadcast in the 90 to 95 MHz band. Further, for mobile terminals such as smartphones and car navigation systems, for example, V-Low multimedia broadcasting in the 95 to 108 MHz band has been started.

For signal transmission of wide FM broadcasting and V-Low multimedia broadcasting, a leaky coaxial cable such as an LCX cable corresponding to these broadcasting frequency bands is used.

This leaky coaxial cable is often laid in a place that is easily affected by the outdoor natural environment (wind, earth echo, earthquake, etc.) assuming reception by transportation such as railroads and automobiles.

At the place where the cable is laid, stress such as bending or vibration is applied to the cable due to strong wind or ground resonance, for example. Leakage coaxial cable has a leak hole (hereinafter referred to as "slot") whose opening shape is determined so that a signal of a predetermined frequency leaks in the metal layer inside the cable. If the opening shape of the slot changes due to the influence of vibration generated by ground resonance or bending during laying, the wave source strength changes, the coupling loss changes, and the reception level of the transmission signal may decrease.

Japanese Unexamined Patent Publication No. 2008-166007 Japanese Unexamined Patent Publication No. 61-269810

As described above, in the case of the conventional technique, when stress such as bending or vibration is applied to the cable, there is a problem that the wave source strength changes, the coupling loss changes, and the reception level of the transmitted signal may decrease.
Furthermore, if the 95 to 108 MHz band (V-Low band) is additionally supported by the conventional leaky coaxial cable, the applicable frequency will be expanded, so that the pitch and shape of the slots formed in the outer conductor will be changed more than before. It is necessary to suppress fluctuations in the frequency of the leaked radio waves radiated and to have stable characteristics by eliminating variations in the radiation angle.

The present invention has been made to solve such a problem, and is resistant to bending and vibration generated by strong winds and ground resonance after cable laying, and can prevent the reception level of the transmitted signal from being lowered in the V-Low band. It is an object of the present invention to provide a leaky coaxial cable and a method for manufacturing a leaky coaxial cable corresponding to the above.

The leaky coaxial cable of the present invention is an internal conductor, an insulator provided around the internal conductor, and a tape-shaped member wavy in the longitudinal direction, which is wound around the insulator and provided in a predetermined frequency band. It is provided with an external conductor having a plurality of slots for leaking the signal of. The plurality of slots are arranged continuously at intervals in the longitudinal direction at an angle of + α with respect to the longitudinal direction in a certain direction, and the four first slots are arranged. It has four second slots that are line-symmetrical and are continuously arranged at an angle −α with respect to the longitudinal direction in a certain direction, and the outer conductor is provided with the plurality of slots. It has a metal layer wavy in a bellows shape and an insulating resin layer provided on the metal layer, and the wavy pitch is in the range of 1.4 mm or more and 3.5 mm or less, and the wavy depth is It is formed in a bellows shape so as to satisfy the condition of 0.14 <wave depth / wave pitch <0.35 in the range of 0.4 mm or more and 0.9 mm or less. A presser foot tape wound around the surface of the outer conductor with a constant tension so as to hold the outer conductor in order to maintain the bellows shape, and an insulating outer cover provided on the presser foot tape. A support member projecting from the jacket in the longitudinal direction is provided.

The method for manufacturing a leaky coaxial cable of the present invention includes a step of arranging an insulator around an internal conductor and a tape-shaped member wavy in the longitudinal direction, and has a plurality of slots for leaking signals in a predetermined frequency band. a method of manufacturing a leaky coaxial cable have a a step of providing wound outer conductor to the insulator, the plurality of slots in a predetermined direction at an angle + alpha relative to the longitudinal direction at intervals in the longitudinal direction It is line-symmetrical with respect to the four first slots that are tilted and continuously arranged, and the four first slots that are tilted and continuously arranged at an angle -α with respect to the longitudinal direction. A metal layer having four second slots and the outer conductor having the plurality of slots pierced and wavy in a bellows shape, and an insulating resin layer provided on the metal layer. consist of, and in the range corrugation pitch less 1.4mm or 3.5 mm, and a range corrugation depth of 0.4mm or more 0.9mm or less, 0.14 <corrugation depth / waves The step of forming the bellows shape so as to satisfy the condition of the attachment pitch <0.35, and winding the presser winding tape around the surface of the outer conductor with a constant tension so as to hold the outer conductor in order to maintain the bellows shape. It further includes a step of providing an insulating outer cover on the presser foot tape, and a step of providing a support member projecting from the outer cover in the longitudinal direction .

According to the present invention, a leaky coaxial cable corresponding to the V-Low band, which is resistant to bending and vibration generated by strong winds and ground resonance after cable laying and can prevent a decrease in the reception level of a transmitted signal, and a method for manufacturing the same. Can be provided.

It is a figure which shows the structure of the LCX cable of one Embodiment. It is sectional drawing of the LCX cable of FIG. It is a partially enlarged view of the metal tape of the LCX cable of FIG. It is a figure which shows the formation range of a slot in an LCX cable. It is a top view of a metal tape. It is sectional drawing of a metal tape. It is a figure (table) which shows the result of having evaluated VSWR, bending characteristic, connector / jig tool consistency by fixing the waving depth and changing the waving pitch. It is a figure (table) which shows the result of having evaluated VSWR, bending characteristic, connector / jig tool consistency by fixing the waving pitch and changing the waving depth.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing a configuration of an LCX cable according to an embodiment of the leaky coaxial cable of the present invention, FIG. 2 is a sectional view of the LCX cable of FIG. 1, and FIG. 3 is a portion of a metal tape of the LCX cable of FIG. It is an enlarged view.

The LCX cable is used in railway traffic and automobile traffic, and is, for example, a 43D size cable (insulator outer shape is about 43 mm, characteristic impedance is about 50 Ω). In the LCX cable, when a signal voltage is applied between the center conductor and the outer conductor, a current flows through each conductor, and the distribution state of the diversion changes due to the influence of the slots provided in the outer conductor. It is a communication cable that uses a mechanism that generates an electromagnetic field from. That is, the slot leaks a signal in a predetermined frequency band.

The LCX cable of the present embodiment corresponds to a predetermined frequency, for example, five frequency bands (bands) of 76 to 108, 140 to 160, 260 to 275, 335 to 430, and 450 to 470 MHz. The frequency band is determined by the opening area, number, tilt angle, period, etc., which are determined by the length and width of the slot. In particular, the slot opening area and tilt angle change the coupling loss and wave source intensity. The resonance frequency is changed to affect the voltage standing wave ratio (VSWR) of a specific frequency. The configuration will be described below.

As shown in FIGS. 1 and 2, the LCX cable 1 of this embodiment includes an inner conductor 2 formed of, for example, a hollow copper pipe as a central conductor, and an insulator provided around the inner conductor 2. As an outer conductor provided by winding a cordel string 4, a polyethylene pipe 3 (hereinafter referred to as "polyethylene pipe 3") and a glass tape 3a) on an insulator (outer glass tape 3a) in the circumferential direction. The metal tape 5, the presser winding tape 6 provided on the surface of the metal tape 5 so as to press the metal tape 5, the sheath 7 coated on the presser winding tape 6, and the sheath 7 in the longitudinal direction of the cable. It is provided with a supporting raised portion 8 as a supporting member projecting from the above.

The Kordel string 4 is a spacer spirally wound around the outer surface of the inner conductor 2. The polyethylene pipe 3 is an insulating tubular body (inner cover) provided at regular intervals via an inner conductor 2 and a Kordel string 4. The glass tape 3a is a heat-resistant member wound around the surface of the polyethylene pipe 3. In this example, the insulator is composed of the Kordel string 4, the polyethylene pipe 3, and the glass tape 3a, but the insulator may be composed of highly foamed polyethylene (abbreviated as highly foamed PE). Further, in this example, the glass tape 3a is used, but the glass tape 3a is not an essential element.

The metal tape 5 is a thin tape-shaped member having a two-layer structure of a metal layer and an insulating resin layer, which is corrugated in a bellows shape (see FIGS. 1 and 6). The presser foot tape 6 is a member for winding the metal tape 5 around the surface of the metal tape 5 with a constant tension to maintain the bellows shape of the metal tape 5. As the presser foot tape 6, a polyester tape having a thickness of, for example, about 0.025 mm to 0.1 mm is used.

The sheath 7 is a tubular insulating member (coating) having an outer diameter (cylinder diameter) of, for example, 20 mm or more and 54 mm or less. A non-halogen flame-retardant polyethylene material having a wall thickness of, for example, 1.5 to 3.0 mm is used for the sheath 7.
The supporting ridge 8 supports the entire cable including the sheath 7. A support wire 9 made of a stranded wire is provided as an inner core inside the support ridge portion 8.

As shown in FIG. 3, the metal tape 5 includes an aluminum tape 52 as a metal layer (a thin film-like (tape-like) member of metal) having a wall thickness of, for example, 0.18 to 0.22 mm, and the aluminum tape 52. A plastic tape 53 as an insulating resin layer having a wall thickness of, for example, 0.05 to 0.15 mm, which is laminated so as to provide a step serving as a stacking allowance 54 on both edges of the slot 52a bored in the aluminum tape 52. And have. Reference numeral C indicates the center position of the slot 52a. Although FIG. 3 shows only the slots 52a for a partially enlarged view, a plurality of slots 52b to 52h (see FIG. 5) are arranged in a row in the longitudinal direction.

That is, the metal tape 5 includes an aluminum tape 52 (metal layer) in which a plurality of slots 52a to 52h are bored and corrugated in a bellows shape, and a plastic tape 53 (insulating resin) provided on the aluminum tape 52. It is a tape-shaped member having a two-layer structure composed of layers). As the member constituting the insulating resin layer, for example, a laminated film or the like may be used in addition to the plastic tape 53.

As shown in FIG. 4, the slots 52a to 52h of the metal tape 5 have a center position C in a range of, for example, 45 ° to the left and right at a portion opposite to the upper portion where the supporting ridge portion 8 of the sheath 7 is provided. It is provided so as to be located in the range of 90 ° as a whole). That is, the slots 52a to 52h are arranged on the opposite side of the sheath 7 with respect to the support wire 9 provided on the sheath 7.

As shown in FIG. 5, the metal tape 5 has a plurality of (four in this example) slots 52a to 52d (referred to as first slots) that are inclined in a certain direction at intervals in the longitudinal direction B, and each of these slots 52a. A plurality of (4) slots 52e to 52h (referred to as second slots) arranged symmetrically (line-symmetrically) with the line 51 interposed therebetween are bored with respect to ~ 52d. The line 51 is a straight line in a direction (width direction) orthogonal to the longitudinal direction B of the metal tape 5.

As for the correspondence between the slots, the slot 52a and the slot 52e correspond, the slot 52b and the slot 52f correspond, the slot 52c and the slot 52g correspond, and the slot 52d and the slot 52h correspond.

Taking one slot in the first slot as an example, for example, the slot 52a is arranged so as to be inclined at an angle + α with respect to the longitudinal direction B. The same applies to the other first slots. For example, the slot 52e, which is one of the second slots, is arranged so as to be inclined at an angle −α with respect to the longitudinal direction B. The same applies to the slots of the other second slots.

As shown in FIG. 6, the metal tape 5 is provided with fine corrugated (bellows-shaped) wrinkles in order to relieve stress due to bending of the cable.

FIG. 6 shows the cross section (corrugated shape) of the wrinkles of the corrugated (bellows-shaped) of the metal tape 5, and the distance (interval) from the ridge to the ridge of the cross section (corrugated shape) is determined by the wave pitch S and the corrugated shape. When the height is the wavy height H, the thickness of the metal tape 5 is h, and the depth of the corrugated shape is the wavy depth Hh, the metal tape 5 has 0.14 <(Hh) /. It shall be formed so as to satisfy the condition (formula) of S <0.35. The wavy depth Hh is a value obtained by subtracting the thickness of the metal tape 5 from the wavy height H including the thickness of the metal tape 5.

On the metal tape 5, fine corrugated (bellows-like) wrinkles are formed, the wave pitch S is 1.4 mm or more and 3.6 mm or less, and the wave depth Hh is 0.4 mm or more and 1.0 mm or less. By forming in the range of 14 <(wave depth Hh) / wave pitch S <0.35, it is possible to obtain a predetermined cable characteristic while maintaining excellent flexibility.

Further, as described above, the outer diameter of the polyethylene pipe 3 (insulator) of the cable 1 used in this cable test is 43 mm, but even if the outer diameter of the polyethylene pipe 3 is different, the metal tape 5 is used. Fine corrugated (bellows-shaped) wrinkles, wavy pitch S1.4 mm or more and 3.5 mm or less, wavy depth H-h 0.4 mm or more and 0.9 mm or less, 0.14 <(H-h) / S <0 By forming it so as to satisfy the condition of .35, it has excellent flexibility for a cable of that size.

When a cable bending test was carried out on a cable 1 having an outer diameter of the polyethylene pipe 3 of, for example, 20 mm, it was confirmed that the cable 1 had excellent flexibility if the above conditions were satisfied.

Hereinafter, the performance of the LCX cable will be described with reference to FIGS. 7 and 8. FIG. 7 is a table showing the results of evaluating VSWR, bending characteristics, connector / jig / tool consistency by fixing the wave depth and changing the wave pitch, and FIG. 8 shows the result of fixing the wave pitch and changing the wave pitch. It is a table which shows the result of having evaluated VSWR, bending characteristic, connector / jig tool consistency by changing the value.

As one of the indexes for evaluating the performance of the coaxial cable, for example, there is a practical target (threshold value) of a voltage standing wave ratio "VSWR" of 1.5 or less.
The item "VSWR" in FIGS. 7 and 8 shows the result of VSWR evaluation based on the practical target (threshold value). VSWR1.0 represents an ideal state without reflection. In the VSWR evaluation, if the VSWR in each frequency band is all 1.5 or less, it is marked as a circle (◯), and if there is even one that exceeds 1.5, it is marked as a cross (x).

As one of the indexes for evaluating the performance of the coaxial cable, for example, there is a bending characteristic, and the item of "bending characteristic" in FIGS. 7 and 8 shows the result of evaluating the bending characteristic.
In the flexibility evaluation, after repeatedly bending the cable 1 in contact with the side surface of a cylindrical mandrel having a diameter 30 times the outer diameter of the cable, if the required characteristics of the LCX cable are not impaired, the circle (○) is impaired. It is marked as x (x).

As the workability of the coaxial cable, for example, there is an index of whether or not the consistency with the connector is easy, and the item of "connector / jig / tool consistency" in FIGS. 7 and 8 shows the result of evaluation of this. .. In the connector consistency evaluation, in the installation work of the existing connector, it is marked as a circle (○) if it can be mounted without any problem and if a special tool specific to the cable 1 is not used, and a cross (×) if it is damaged.

From the evaluation results of FIGS. 7 and 8 above, when the wave depth Hh is fixed to 0.5 mm, the wave pitch S is preferably in the range of 1.4 mm or more and 3.5 mm or less, and the wave is preferably waved. When the pitch S is fixed at 2.8 mm, it can be said that the wave depth Hh is preferably in the range of, for example, 0.4, 0.5, 0.7, 0.9 mm.

The cable 1 used in this cable evaluation test is a leaky coaxial cable compatible with wide FM broadcasting and V-Low multimedia broadcasting, but even if the corresponding frequency bands are different, the metal tape 5 is fine. The wrinkles of the corrugated (bellows shape) have a wavy pitch S in the range of 1.4 mm or more and 3.5 mm or less and a wavy depth HH in the range of 0.4 mm or more and 0.9 mm or less, and are 0.14. When the condition of <(wave depth Hh) / wave pitch S <0.35 is satisfied, the size has excellent consistency with the connector.

Here, a method of manufacturing the LCX cable will be described.
First, the inner conductor 2 of the hollow pipe is prepared. The Kordel string 4 is spirally wound around the prepared inner conductor 2. After that, the polyethylene pipe 3 is arranged at regular intervals via the inner conductor 2 and the Kordel string 4.

Subsequently, a glass tape 3a, which is a heat-resistant member, is wound around the surface of the polyethylene pipe 3. Further, a metal tape 5 having a plurality of slots 52a to 52h that leak signals in a predetermined frequency band is wound around the glass tape 3a in the circumferential direction.

The metal tape 5 has a wave pitch S of 1.4 mm or more and 3.5 mm or less, a wave depth Hh of 0.4 mm or more and 0.9 mm or less, and 0.14 <(wave depth H). -H) / Waves are formed in a bellows shape in the range of pitch S <0.35.
An example of such an operation is an example, and it is possible to change the operation in various ways by exchanging each step, adding a new step, or deleting a part of the steps.

As described above, according to the LCX cable of this embodiment, the cordel string 4 is spirally wound around the inner conductor 2, and the polyethylene pipe 3 is provided at regular intervals via the inner conductor 2 and the cordel string 4, and the polyethylene pipe 3 is provided. A glass tape 3a is wound around the surface of the cable, and the waving pitch S is set to 1.4 mm or more and 3.5 mm or less in the circumferential direction, and the waving depth H-h is set to 0.4 mm or more and 0.9 mm or less. By winding the metal tape 5 formed in a bellows shape in the range of .14 <(wave depth Hh) / wave pitch S <0.35 to form an LCX cable, strong winds and ground resonance can be generated after the cable is laid. It is possible to provide an LCX cable corresponding to the V-Low band, which is resistant to bending and vibration generated in the above and can prevent the reception level of the transmitted signal from being lowered.

Although the embodiment of the present invention has been described, this embodiment is shown as an example, and can be implemented in various other forms, and the components of the present invention are not deviated from the gist of the invention. It can be omitted, replaced, or changed.

1 ... LCX cable, 2 ... internal conductor, 3 ... polyethylene pipe, 3a ... glass tape, 4 ... cordel string, 5 ... metal tape, 6 ... tape, 7 ... sheath, 8 ... support ridge, 9 ... support wire, 52a-52h ... Slot, 53 ... Plastic tape, 54 ... Stacking allowance.

Claims (2)

With the inner conductor
An insulator provided around the inner conductor and
It is a tape-shaped member wavy in the longitudinal direction, is provided by being wound around the insulator, and includes an outer conductor having a plurality of slots for leaking signals in a predetermined frequency band.
The plurality of slots
Four first slots that are continuously arranged at an angle of + α with respect to the longitudinal direction at intervals in the longitudinal direction.
It has four second slots that are line-symmetrical with respect to the four first slots and are continuously arranged at an angle −α with respect to the longitudinal direction in a certain direction.
The outer conductor is
A metal layer in which the plurality of slots are bored and wavy in a bellows shape,
It has an insulating resin layer provided on the metal layer, and has an insulating resin layer.
In the range of wave pitch of 1.4 mm or more and 3.5 mm or less and wave depth of 0.4 mm or more and 0.9 mm or less, 0.14 <wave depth / wave pitch <0.35 is formed in a bellows shape so as to satisfy the condition,
In order to maintain the bellows shape, a presser foot tape wound around the surface of the outer conductor with a constant tension so as to press the outer conductor, and
An insulating outer cover provided on the presser foot tape and
A support member projecting from the jacket in the longitudinal direction and
Leaky coaxial cable characterized that you include a. The process of arranging an insulator around the inner conductor and
A tape-shaped member that is attached waves in the longitudinal direction, a method for producing a leaky coaxial cable have a a step of the outer conductor is provided by winding the insulating body having a plurality of slots leaking a signal of a predetermined frequency band ,
The plurality of slots
Four first slots that are continuously arranged at an angle of + α with respect to the longitudinal direction at intervals in the longitudinal direction.
It has four second slots that are line-symmetrical with respect to the four first slots and are continuously arranged at an angle −α with respect to the longitudinal direction in a certain direction.
The outer conductor is composed of a metal layer in which the plurality of slots are bored and corrugated in a bellows shape, and an insulating resin layer provided on the metal layer, and the corrugation pitch is 1.4 mm. Bellows so as to satisfy the condition of 0.14 <wave depth / wave pitch <0.35 in the range of 3.5 mm or more and the wave depth of 0.4 mm or more and 0.9 mm or less. The process of forming into a shape and
A step of wrapping a presser foot tape around the surface of the outer conductor with a constant tension so as to hold the outer conductor in order to maintain the bellows shape.
The process of providing an insulating coating on the presser foot tape and
A step of providing a support member projecting in the longitudinal direction on the jacket, and
A method of manufacturing a leaky coaxial cable, which further comprises.

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