JP7560517B2 - Outdoor Communication Cable - Google Patents

Description

The present invention relates to outdoor communication cables.

2. Description of the Related Art Communication cables such as LAN (Local Area Network) cables are used to connect various devices, such as between servers, between servers and switches, and between servers and personal computers, and in recent years there has been a demand for communication cables suitable for high-speed data communication.
Cables with various structures have been developed as such communication cables. For example, communication cables having a structure in which an inner sheath layer, a shielding layer, and an outer sheath layer are laminated in that order on the outside of a cable core containing multiple insulated wires have been put into practical use (Patent Document 1).

JP 2018-41568 A

In recent years, opportunities for high-speed data communication outdoors have increased, and there is a demand for communication cables that can withstand outdoor use. Outdoor communication cables are exposed to ultraviolet rays, rain, dust, etc., and therefore are required to have higher durability than indoor communication cables. For example, the JCS standard established by the Electric Cable Makers' Association states that the thickness of the outer sheath of outdoor communication cables should be approximately 1.5 mm.
Therefore, it is conceivable to simply increase the thickness of the sheath of the communication cable as described in the above-mentioned Patent Document 1. However, communication cables for outdoor use are required to have not only high durability but also the ability to be wound on a reel and unwound from a reel for portability and length adjustment. As described above, simply increasing the thickness of the sheath of an indoor communication cable tends to cause problems when winding the cable on a reel and unwound from a reel. In addition, such communication cables have a different diameter from conventional communication cables, which makes it difficult to connect them to general connectors.
SUMMARY OF THE PRESENTLY PREFERRED EMBODIMENTS Accordingly, a primary object of the present invention is to provide an outdoor communication cable that satisfies outdoor standards and can be easily wound onto and unwound from a reel.

In order to solve the above problem, according to one aspect of the present invention,
a cable core including a plurality of twisted pairs each formed by twisting two insulated wires together;
a first jacket layer covering an outer periphery of the cable core;
a second outer cover layer disposed adjacent to the first outer cover layer and covering an outer periphery of the first outer cover layer;
having
Each of the insulated wires includes a stranded conductor formed by stranding a plurality of wires together and an insulator that covers an outer periphery of the stranded conductor,
The Shore hardness of the second outer layer is higher than the Shore hardness of the first outer layer.
An outdoor communication cable is provided.

The outdoor communication cable of the present invention meets outdoor standards and can be easily wound onto and pulled out from the reel.

1 is a cross-sectional view of an outdoor communication cable according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing a schematic enlarged cross-sectional view of an insulated wire. FIG. 2 is a schematic diagram showing the state of an insulated wire of a twisted pair wire. FIG. 1 is a diagram illustrating a method for a left-right bending test. FIG. 1 is a diagram showing a schematic diagram of a U-bend test method. FIG. 1 is a diagram illustrating a method for a torsion test.

The following describes an outdoor communication cable according to a preferred embodiment of the present invention. The outdoor communication cable of this embodiment (hereinafter also simply referred to as a "communication cable") is a communication cable made up of a twisted pair cable for a so-called LAN (Local Area Network).

The communication cable of this embodiment may include other configurations as long as it has a cable core and a first and second outer sheath layer arranged around the cable core. Below, a communication cable 1 shown in FIG. 1 will be described, which mainly has a cable core 10, a winding 20, a shielding layer 30, a first outer sheath layer 40, and a second outer sheath layer 50.

The cable core 10 is composed of a plurality of (here, four) twisted pairs 8 and a cross insert 9 for isolating the plurality of twisted pairs 8 from one another.
As shown in Fig. 3, each twisted pair wire 8 has a structure in which a plurality of (here, two) insulated wires 6 are twisted together in a certain direction (the direction indicated by B in Fig. 3). Also, as shown in Fig. 1, the insulated wire 6 has a structure in which a conductor 2 is covered with an insulator 4. As shown in Fig. 2, the conductor 2 is made of a plurality of (here, 30) soft copper wires (strands 2a), and the insulator 4 is made of polyethylene resin. Also, the conductor 2 may be, for example, a non-compressed conductor in which a plurality of strands 2a are simply twisted together as shown in Fig. 2, or may be a compressed conductor in which a plurality of strands 2a are twisted together and then compressed into a desired shape.
The cross wire 9 is made of polyethylene resin. The cross wire 9 extends in the longitudinal direction of the communication cable 1 and separates the twisted pairs 8 in a non-contact state. The cross wire 9 is twisted along the longitudinal direction of the communication cable 1, and accordingly, the twisted pairs 8 are also twisted while being separated by the cross wire 9.

A winding 20 is provided around the cable core 10. The winding 20 is a member for maintaining a constant distance between the conductor 2 in the cable core 10 and the shielding layer 30. There are no particular limitations on the type of winding 20, but in this embodiment, the winding 20 is made of, for example, a high-density polyethylene tape or an extruded coating layer (inner coating layer).
When the winding 20 is made of a high-density polyethylene tape, the method of winding the high-density polyethylene tape is not particularly limited, and for example, the high-density polyethylene tape is wound horizontally along the length direction of the cable core 10. In this specification, "horizontal winding" means that a long tape is wound in a spiral shape along the length direction of the cable core 10, and the side edge of the tape is wound while overlapping the previously wound tape. The thickness and number of sheets of the high-density polyethylene tape are not particularly limited as long as they do not impair the object and effect of this embodiment.
On the other hand, when the winding 20 is composed of an extrusion coating layer arranged around the cable core 10, the winding 20 may be a layer extrusion-coated with polyethylene, and the thickness of the extrusion coating layer is preferably 0.2 mm or more and 0.4 mm or less. When the extrusion coating layer is formed, the distance between the cable core 10 and the shielding tape described below tends to be constant, and the high-frequency electrical characteristics of the communication cable 1 tend to be good. The Shore hardness (Shore D hardness) of the extrusion coating layer, measured using an indenter type D in accordance with JIS K7215 (Durometer hardness test method for plastics), is preferably 32 or more and 38 or less. When the extrusion coating layer has the Shore D hardness, the bending characteristics of the communication cable 1 become good.
In this specification, in the above-mentioned durometer hardness testing method, the Shore hardness when a type A indenter is used is referred to as "Shore A hardness" or "HDA", and the Shore hardness when a type D indenter is used is referred to as "Shore D hardness" or "HDD".

A shielding layer 30 is formed around the coil 20. The shielding layer 30 is composed of a shielding tape and a braided wire. The shielding tape is composed of, for example, an Al/PET tape in which aluminum foil (Al) is attached to a polyethylene terephthalate resin substrate (PET), and the shielding tape is wound horizontally along the length of the cable core 10, covering the outer circumference of the coil 20. On the other hand, the braided wire is composed of a tin-plated soft copper wire with an outer diameter of 0.1 mm.

A first outer jacket layer 40 and a second outer jacket layer 50 are disposed around the shielding layer 30. The first outer jacket layer 40 is a layer disposed so as to cover the above-mentioned shielding layer 30. The second outer jacket layer 50 is a layer disposed adjacent to the first outer jacket layer 40 so as to cover the first outer jacket layer 40. The second outer jacket layer 50 is the outermost layer of the communication cable 1. The first outer jacket layer 40 and the second outer jacket layer 50 function as layers for protecting the cable core 10 from impact, friction, ultraviolet rays, moisture, and the like applied to the communication cable 1 when used outdoors or indoors.
The materials of the first and second jacket layers 40 and 50 are appropriately selected depending on the application and usage environment of the communication cable 1, and are selected from, for example, polyvinyl chloride, polyethylene, etc. Furthermore, the materials of the first and second jacket layers 40 and 50 may be the same or different. The types of the first and second jacket layers 40 and 50 are appropriately selected depending on the desired hardness of each layer.
Specifically, the materials of the first and second jacket layers 40 and 50 are selected so that the Shore hardness of the second jacket layer 50 is higher than that of the first jacket layer 40. The Shore hardness of the first and second jacket layers 40 is determined by preparing sheets corresponding to the second and first jacket layers 50 and 40 of the communication cable 1, respectively, and measuring them in accordance with the above-mentioned JIS K7215 (Durometer hardness test method for plastics). The difference between the Shore hardness of the first and second jacket layers 40 (Shore hardness of the second jacket layer 50 - Shore hardness of the first jacket layer 40) is appropriately selected according to the desired performance of the communication cable 1. For example, when the Shore hardness of the first outer layer 40 and the Shore hardness of the second outer layer 50 are both measured using a type A indenter, the difference in Shore A hardness is preferably 10 to 30, more preferably 15 to 25. When the difference in Shore A hardness is within the above range, the hardness of the first outer layer 40 and the second outer layer 50 is likely to fall within an appropriate range. The specific Shore A hardness of the first outer layer 40 is preferably 60 to 80, more preferably 65 to 75. When the Shore A hardness of the first outer layer 40 is within this range, kinking is less likely to occur when the communication cable 1 is wound on or pulled out from the reel. On the other hand, the Shore A hardness of the second outer layer 50 may be higher than the Shore A hardness of the first outer layer 40, specifically, preferably 80 to 100, more preferably 85 to 95. When the Shore A hardness of the second outer jacket layer 50 is within this range, the communication cable 1 can be more easily wound onto and unwound from a reel.

The thicknesses of the first and second sheath layers 40 and 50 are appropriately selected depending on the application of the communication cable 1, but as described above, the JCS standard set by the Electric Cable Manufacturers' Association and the like state that the thickness of the sheath of a communication cable for outdoor use is about 1.5 mm. Therefore, it is preferable to set the total thickness of the first and second sheath layers 40 and 50 to about 1.5 mm. However, the thickness of the sheath (the total thickness of the first and second sheath layers 40 and 50) is much thicker than the thickness of a cable for indoor use. Therefore, it is preferable to adjust the thicknesses of the first and second sheath layers 40 and 50 so that the diameter of the communication cable 1 when the second sheath layer 50 is peeled off and the first sheath layer 40 is exposed is equivalent to the diameter of a general (indoor) communication cable. The specific thickness of the first sheath layer 40 is preferably about 0.5 mm from the viewpoint of connectivity with an RJ-45 connector. From the viewpoint of the JCS standard defined by the Electric Cable Manufacturers' Association, the specific thickness of the second outer sheath layer 50 is preferably about 1.0 mm. When the thicknesses of the first outer sheath layer 40 and the second outer sheath layer 50 are within this range, not only is it easier to connect to a connector as described above, but it also becomes easier to wind the cable onto a reel or pull it out, and it becomes easier to prevent kinking of the communication cable 1.
There are no particular limitations on the method for forming the first outer layer 40 and the second outer layer 50, and they can be formed by a known extrusion method.

(1) Preparation of Samples (1.1) Sample 1 (Comparative Example 1)
The conductor was a solid wire having an outer diameter of 0.565 mm. High-density polyethylene was prepared as an insulating resin, and extruded from a die of an extruder to cover the conductor with the insulating resin, thereby obtaining an insulated wire.
Thereafter, two insulated wires were twisted together to form a twisted pair wire. Next, a cross insert was prepared, and four pairs of twisted wires were arranged along the cross insert to form a cable core, which was then twisted at a predetermined pitch.
Next, a nonwoven fabric was prepared as a push winding material and was wound transversely around the cable core.
Furthermore, as a shielding layer, a shielding tape was prepared and wound crosswise in a forward winding manner, and further braided with a tin-plated soft copper wire having an outer diameter of 0.1 mm.
Polyethylene was prepared as the resin for the outer jacket layer, and this was extruded through the die of an extruder to form an outer jacket layer having a thickness of 1.5 mm around the shielding layer.
Separately, a sheet corresponding to the outer layer was prepared, and its Shore hardness was measured in accordance with JIS K7215 (a method for testing durometer hardness of plastics).

(1.2) Sample 2 (Comparative Example 2)
An outer cover layer having a thickness of 1.5 mm was formed around the shielding layer in the same manner as in Comparative Example 1, except that the material of the outer cover layer was changed to polyvinyl chloride.
Separately, a sheet corresponding to the outer layer was prepared, and its Shore hardness was measured in accordance with JIS K7215 (a method for testing durometer hardness of plastics), yielding a Shore A hardness (HDA) of 70.

(1.3) Sample 3 (Example)
A stranded conductor was prepared by stranding 30 soft copper wires (element wires) having an outer diameter of 0.08 mm in a predetermined direction. High-density polyethylene was prepared and extruded from a die of an extruder to cover the stranded conductor with an insulator, thereby obtaining an insulated wire.
Thereafter, two insulated wires were twisted together to form a twisted pair wire. Next, a cross insert was prepared, and four pairs of twisted wires were arranged along the cross insert to form a cable core, which was then twisted at a predetermined pitch.
Furthermore, polyethylene was prepared as an inner coating layer, and this was extruded through the die of an extruder to form an inner coating layer having a thickness of 0.3 mm around the cable core.
Next, a shielding tape was prepared as a shielding layer and was wound transversely around the inner sheath layer, and further braided with tin-plated soft copper wire having an outer diameter of 0.1 mm.
Furthermore, polyvinyl chloride was prepared as the resin for the first outer layer, and this was extruded through the die of an extruder to form a first outer layer having a thickness of 0.5 mm around the shielding layer.
Thereafter, polyvinyl chloride was prepared as the resin for the second outer layer, and this was extruded through the die of an extruder to form a second outer layer having a thickness of 1.0 mm around the first outer layer.
Separately, sheets corresponding to the first and second outer layers were prepared, and their Shore hardness was measured in accordance with JIS K7215 (Durometer hardness test method for plastics). As a result, the Shore A hardness (HDA) of the first outer layer was 70, and the Shore A hardness (HDA) of the second outer layer was 90.

(1.4) Sample 4 (Comparative Example 3)
A cable was prepared in the same manner as in Sample 2, except that the cable core to the shielding layer were prepared in the same manner as in Sample 3.

(2) Evaluation of Sample Characteristics (2.1) Handling Test Each sample (communication cable) having a length of about 50 m was wound on a commercially available reel for LAN and evaluated according to the following criteria.
◯: No bias or kinking occurred, and it was possible to wind the film evenly. △: No kinking occurred, but the film could not be wound evenly, and bias occurred. ×: No bias occurred, but kinking occurred.

(2.2) Processability test Each sample was connected to an RJ-45 connector to determine whether it was possible to connect. Sample 3 was connected to the connector after removing the second jacket layer. On the other hand, the other samples were connected to the connector without removing the jacket layer.
〇: It was possible to attach it to the connector using normal procedures. ×: It was not possible to attach it to the connector using normal procedures, or it was unstable even if it was attached.

(2.3) Flexural Properties The following three tests were carried out on the flexural properties of each sample, and the properties were evaluated according to the following criteria.
〇: Passed all three tests △: Passed one or two of the three tests ×: Failed all three tests

- Right-left bending test The method of the right-left bending test is shown in Figure 4. First, the end side of each sample (communication cable 1) was sandwiched between a pair of mandrels 111 (diameter 50 mm, R25) and a pair of vibration stoppers 112 of a bending test device, and a 500 g weight 113 was attached to the end. The sample was bent 90° to the left and right at a speed of 60 round trips per minute, using the part held by the pair of mandrels 111 as a fulcrum. Then, the number of times until at least one conductor broke was confirmed. The results were evaluated as follows.
Pass: No breaks even after 100,000 or more bends Fail: Breaks after less than 100,000 bends

U-Bend Test The method of the U-bend test is shown in FIG. 5. First, one end of the sample (communication cable 1) was fixed by the fixing portion 211, and the sample was bent into a U-shape (bending radius 50 mm). Then, the other end of the sample was reciprocated in parallel to the longitudinal direction of the sample with a stroke of 500 mm. The speed was 60 reciprocations/min. Then, the number of times until at least one conductor was broken was confirmed.
Pass: No breaks even after 2 million or more round trips Fail: Breaks after less than 2 million round trips

Twisting test The method of the twisting test is shown in FIG. 6. One end of the sample (communication cable 1) was fixed to a fixed part 312 of a twisting test device, and a 500 g weight 313 was attached to the end. Meanwhile, the other end of the sample was held by a twisting part 311 of the twisting test device. Then, the twisting part 311 was rotated ±200° left and right to twist the sample. The distance between the fixed part 312 and the twisting part 311 was 500 mm, and the speed was 60 reciprocations per minute. Then, the number of times until at least one conductor was broken was confirmed.
Pass: No breaks even after 500,000 or more round trips Fail: Breaks after less than 500,000 round trips

(2.4) Electrical Characteristics Test 100 m of each sample was prepared, and the return loss (RL), insertion loss (IL), near-end crosstalk attenuation (NEXT), etc. were measured using a general-purpose LAN cable automatic measuring device.

(2.5) Overall Evaluation Each sample (cable) was evaluated as follows based on the results of the three tests of handleability, processability, and bending properties described above.
〇: Passed all three tests △: Passed one or two of the three tests ×: Failed all three tests

(3) Summary As shown in Table 1 above, the communication cable (Sample No. 3) in which the insulated electric wire includes a twisted conductor, the outer jacket has a two-layer structure, and the Shore hardness of the outer second outer jacket layer is higher than that of the inner first outer jacket layer, all showed good results in terms of handleability, processability, and bending characteristics. It is believed that the moderate flexibility of the first outer jacket layer made it difficult for kinks to occur, and the relatively hard second outer jacket layer made it easy to wind the cable around a reel, which is why the handleability evaluation was ◯. Furthermore, since the outer jacket had a two-layer structure and only the second outer jacket layer was removed when attaching the connector, the processability was good. In addition, since the insulated electric wire includes a twisted conductor, it is believed that the strength of the insulated electric wire was increased and the bending characteristics were very excellent.
The cable of this example (Sample 3) satisfied the standard values for all of the electrical properties (RL, IL, and NEXT). The other cables (Samples 1, 2, and 4) also had the same standard values as Sample 3.

On the other hand, when the outer layer consisted of only one layer of PVC, it was difficult to connect to the connector, and workability was also reduced. It is believed that because the outer layer was too soft, it was prone to becoming unevenly wound around the reel (samples 2 and 4).

When the outer sheath layer consisted of only one layer of PE, it was easy to wind it onto a reel, but because the outer sheath layer was too hard, the cable was prone to kinking and was difficult to connect to a connector, which is thought to have reduced workability (Sample 1).

The outdoor communication cable of the present invention meets outdoor standards, can be easily wound onto a reel, and can be easily pulled out from the reel. It can also be easily connected to various connectors. Therefore, it can be used in a variety of fields as a communication cable that can be used outdoors.

REFERENCE SIGNS LIST 1 outdoor communication cable 2 conductor 2a wire 4 insulator 6 insulated electric wire 8 twisted pair wire 9 cross insert 10 cable core 20 winding 30 shielding layer 40 first outer sheath layer 50 second outer sheath layer 111 mandrel 112 anti-vibration 113 weight 211 fixed portion 311 twisted portion 312 fixed portion 313 weight

Claims (2)

a cable core including a plurality of twisted pairs each formed by twisting two insulated wires together;
a first jacket layer covering an outer periphery of the cable core;
a second outer cover layer disposed adjacent to the first outer cover layer and covering an outer periphery of the first outer cover layer;
having
Each of the insulated wires includes a stranded conductor formed by stranding a plurality of wires together and an insulator that covers an outer periphery of the stranded conductor,
The Shore hardness of the second outer layer is higher than the Shore hardness of the first outer layer,
The difference between the Shore A hardness of the second outer layer and the Shore A hardness of the first outer layer is 10 or more and 30 or less.
Outdoor communication cable. 2. The outdoor communication cable according to claim 1,
The Shore A hardness of the first outer layer is 60 or more and 80 or less,
The Shore A hardness of the second outer layer is 80 or more and 100 or less.
Outdoor communication cable.

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