Communication Cable

Abstract

A communication cable (1) includes: a twisted pair wire (5) in which twisted together are signal wires (2) each provided with an insulation layer (4) that covers a conductor (3); and an outer covering (7) that accommodates the twisted pair wire (5). The communication cable is characterized in that: the twisted pair wire (5) includes a pair of signal wires (2) and a pair of intervening wires (6); and the signal wires (2) and the intervening wires (6) are twisted together so as to be alternately arranged.

Description

[Technical field]

[0001] The present invention relates to a communications cable, and is particularly suitable for use in signal transmission paths for LANs that meet the standard values ​​of Category 6 and Category 6A, as well as for use in the moving parts of various industrial devices, such as robots including industrial robots and various service robots such as humanoids, and semiconductor manufacturing equipment. [Background technology]

[0002] LAN cables, which have a structure in which an outer sheath is provided around an assembly of multiple twisted-pair wires, are widely used as a representative communication cable. With the spread of communication devices and the accompanying increase in communication data volume, communication cables are required to have high-speed and large-capacity data transmission capabilities.

[0003] A standard called "category" is used to indicate the performance of LAN cables. The most commonly used LAN cables, in order of lowest performance, are Category 5, Category 5e, Category 6, Category 6A, and Category 7, and it is recommended to use LAN cables of Category 6 or higher in today's communication environments.

[0004] In addition, with the spread of IoT (Internet of Things), data communication functions are increasingly being installed in various industrial devices, such as industrial robots and semiconductor devices, and LAN cables are often used as the communication cables for these devices.

[0005] The structure of a typical Category 6 LAN cable (communication cable) is shown in Figure 8. Normally, communication cables 50 are constructed with an outer sheath 57 around the outer periphery of an assembly of four pairs of twisted wires 55, each consisting of two twisted signal wires 52, and Category 6 communication cables 50 often have a structure in which the four pairs of twisted wires 55 are assembled via a spacer with a cross-shaped cross section (cross spacer 58). The cross spacer 58 keeps the distance between the twisted wire pairs 55 at a certain value or more, thereby suppressing crosstalk attenuation that occurs when the twisted wire pairs 55 approach each other, and contributing to improved communication characteristics.

[0006] However, when a general communication cable 50 using the cross insert 58 is used for an industrial robot or semiconductor device, the following problems arise.

[0007] Industrial robots and semiconductor devices generally have moving parts such as rotating parts, bent parts, and U-shaped bent parts, and the communication cables used in these devices are subjected to loads such as bending as the devices move.

[0008] The cross insert 58 has poor flexibility due to its shape, so it is difficult for it to follow bending, and the amount of bending is often limited, and it is easily broken by the load caused by bending. If the cross insert 58 is broken, the twisted pairs 55 in the communication cable 50 will come close to each other, increasing crosstalk attenuation, and it may become impossible to obtain communication characteristics appropriate for the category.

[0009] LAN cables that comply with Category 6 using a method other than a cross insert are described in Patent Documents 1 and 2. The LAN cable described in Patent Document 1 satisfies the Category 6 standard without using an insert by changing the twist pitch of the twisted wire pairs that make up the LAN cable for each twisted wire pair. The LAN cable described in Patent Document 2 satisfies the Category 6 standard without using an insert by setting the twist angle of the twisted wire pairs that make up the LAN cable to a predetermined value.

[0010] However, the LAN cables described in Patent Documents 1 and 2 are silent about maintaining communication characteristics when bending occurs. In particular, in a LAN cable that does not use an insert, the twisted pairs that make up the LAN cable are always close to each other, and there is concern that the communication characteristics may deteriorate when the twisted pairs become abnormally close to each other due to bending.

[0011] In addition, when looking at the behavior of the twisted pair that makes up the LAN cable, the load caused by bending compresses the coating of the signal wires that make up the twisted pair, and the distance between the signal wires at the bend, especially the distance between the conductors that make up the signal wires, may vary. This variation in distance may cause the twisted pair's ability to suppress radiation of electromagnetic induction noise and its ability to shield against external electromagnetic induction noise to vary, which is also a factor in degrading communication characteristics. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] JP 2014-2837 A [Patent Document 2] JP 2001-155559 A Summary of the Invention [Problem to be solved by the invention]

[0013] As described above, conventional communication cables have poor bending resistance, and repeated bending makes it difficult to maintain communication characteristics.

[0014] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a communication cable that has excellent bending resistance and maintains its communication characteristics even when bent repeatedly. [Means for solving the problem]

[0015] The communication cable according to claim 1 is a twisted pair cable in which signal wires each having an insulating layer covering a conductor are twisted together. havingA twisted pair cable is characterized in that it has a pair of signal wires and a pair of intervening wires, and the signal wires and the intervening wires are twisted together so that they are arranged alternately.

[0016] The communication cable according to claim 1 is characterized in that an assembly wire made of a plurality of twisted-pair wires twisted together is covered with an outer sheath.

[0017] The communication cable described in claim 1 is characterized in that, when the twisted pair is viewed in cross section on a plane perpendicular to the longitudinal direction, a pair of signal wires that make up the twisted pair are in contact with each other.

[0018] The communication cable according to claim 1 is characterized in that the intervening wire is a monofilament.

[0019] The communication cable according to claim 2 is characterized in that a shielding layer is provided between the wire assembly and the outer sheath.

[0020] Claim 1 The described communication cable is characterized in that the outer diameter of the intervening wire is smaller than the outer diameter of the signal wire.

[0021] Claim 3 The described communication cable is characterized in that it satisfies the relationship of Equation 1 when the outer diameter of the intervening wire is defined as R1 and the outer diameter of the signal wire is defined as R2. TIFF0007640216000001.tif2053

[0022] Claim 1 The described communication cable is characterized in that, when the outer diameter of the intervening wire is defined as R1 and the outer diameter of the signal wire is defined as R2, the cable satisfies the relationship of Equation 2. TIFF0007640216000002.tif2034

[0023] Claim 3 The described communication cable is characterized in that, when the outer diameter of the intervening wire is defined as R1 and the outer diameter of the signal wire is defined as R2, the cable satisfies the relationship of Equation 3. TIFF0007640216000003.tif2071

[0024] Claim 4 The described communication cable is characterized in that the elongation of the intervening wires is equal to or greater than the elongation of the signal wires.

[0025] Claim 5 The described communication cable is characterized in that the elongation of the intervening wire is 10 times or more greater than the elongation of the signal wire.

[0026] Claim 6 The described communication cable is characterized in that the intervening wire is made of a material having a dynamic friction coefficient of 0.3 or less.

[0027] Claim 7 The described communication cable is characterized in that the intervening wire is made of a material whose static friction coefficient is less than or equal to its kinetic friction coefficient. Effect of the Invention

[0028] According to the present invention, compression of the coating of the signal wires constituting the twisted pair cable is suppressed, and a predetermined inter-conductor distance is maintained even when the cable is bent, thereby maintaining predetermined communication characteristics. [Brief description of the drawings]

[0029] [Figure 1] 1 is an explanatory diagram showing a reference example of the configuration of a communication cable according to the present invention; [Diagram 2] FIG. 1 is an explanatory diagram showing an example of a configuration of a communication cable according to the present invention. [Diagram 3] FIG. 3 is an explanatory diagram illustrating a twisted pair of the communication cable of FIG. 1 and FIG. 2. [Figure 4] 3 is an explanatory diagram showing the state in which twisted pairs of the communication cable in FIG. 2 are brought into close proximity. [Diagram 5] FIG. 2 is an explanatory diagram showing a test method for a bending resistance test. [Figure 6A] FIG. 2 is an explanatory diagram showing the communication cable propagation characteristics of the first embodiment. [Figure 6B] FIG. 2 is an explanatory diagram showing the communication cable propagation characteristics of the first embodiment. [Figure 7A] FIG. 11 is an explanatory diagram showing the communication cable propagation characteristics of the second embodiment. [Figure 7B] FIG. 11 is an explanatory diagram showing the communication cable propagation characteristics of the second embodiment. [Figure 8] FIG. 1 is an explanatory diagram showing the basic structure of a conventional communication cable having a cross insert. [Figure 9] FIG. 13 is an explanatory diagram of a conventional twisted pair wire having a structure in which only two signal wires are twisted together, and in which a shield layer is provided. [Figure 10] FIG. 1 is an explanatory diagram showing the basic structure of a conventional communication cable that does not have an intervening wire. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] Hereinafter, as an example of a communication cable according to the present invention, a basic configuration will be described with reference to the drawings. The communication cable 1 in FIG. 1 and the communication cable 1 in the third embodiment are reference examples of the present invention.

[0031] 1 is composed of a twisted pair 5 formed by twisting together a pair of signal wires 2 and a pair of intermediate wires 6, each having a structure in which a conductor 3 is covered with an insulating layer 4, and the twisted pair 5 is housed in an outer sheath 7. The communication cable 1 is particularly an example in which a shielding layer 8 is provided that collectively covers the signal wires 2 and intermediate wires 6 housed in the outer sheath 7 (however, a shielding layer is not essential for a communication cable).

[0032] 2 includes a twisted pair 15 formed by twisting together a pair of signal wires 12 and a pair of intermediate wires 16, each having a structure in which a conductor 13 is covered with an insulating layer 14, and an assembly wire formed by twisting together a plurality of twisted pairs 15 is housed in an outer sheath 17. The communication cable 10 is particularly an example in which a shield layer 18 is provided to cover the communication wires housed in the outer sheath 17 (however, the shield layer is not essential for communication cables). The communication cable 10 is particularly an example in which a tape layer 19 is provided between the shield layer 18 and the assembly wire (however, the tape layer is not essential for communication cables).

[0033] A characteristic feature of the present invention is that the twisted pair wires 5, 15 constituting the communication cable 1, 10 have a pair of signal wires 2, 12 and a pair of intermediate wires 6, 16, as shown in FIG. 3, and have a structure in which the signal wires 2, 12 and the intermediate wires 6, 16 are twisted together so that they are arranged alternately.

[0034] By twisting the signal wires 2, 12 and the intervening wires 6, 16 so that they are alternately arranged, when the twisted pair wires 5, 15 are bent as the communication cables 1, 10 are bent, particularly when they are bent along the line segment L in Fig. 3, part of the load that tries to compress the insulating layers 4, 14 is absorbed by the intervening wires 6, 16. This reduces the load applied to the insulating layers 4, 14 when they are bent, and suppresses compression of the insulating layers 4, 14.

[0035] Suppressing compression of the insulating layers 4, 14 reduces fluctuations in the distance between the conductors 3, 13 of the signal lines 2, 12 constituting the twisted pair 5, 15, and reduces fluctuations in the electromagnetic induction noise radiation suppression effect and external electromagnetic induction noise shielding effect of the twisted pair 5, 15. As a result, fluctuations in communication characteristics due to bending of the communication cables 1, 10 using the twisted pair 5, 15 are suppressed, contributing to maintaining specified communication characteristics.

[0036] Furthermore, since the intermediate wires 6, 16 absorb the load generated when the communication cables 1, 10 are bent, the load on the signal lines 2, 12 is reduced, and breakage of the conductors 3, 13 due to bending can also be suppressed.

[0037] In addition, twisting the intermediate wires 6, 16 together also has the effect of improving the bending resistance of the shield layers 8, 18, as described below.

[0038] Typically, when constructing the communication cables 1, 10, as shown in Figs. 1 and 2, a shield layer 8, 18 is often provided to collectively cover the signal wires housed in the jacket 7, 17.

[0039] As shown in FIG. 9, generally, when a shielding layer 68 is provided on a twisted pair wire 65 having a structure in which only two signal wires 62 are twisted together, there is a portion where the shielding layer 68 is provided in a substantially elliptical shape, and this portion has a cross-sectional shape with a major axis and a minor axis.

[0040] When a communication cable having a shield layer 68 with such a cross-sectional shape having a major axis and a minor axis is bent, the difference in dimensions between the major axis and the minor axis causes a bias in the load acting on the shield layer 68, and the load tends to concentrate in specific locations. For this reason, the shield layer 68 is likely to break starting from the location where the load is concentrated.

[0041] On the other hand, when the twisted pair wire 5 used in the present invention is provided with the shielding layer 8, its shape becomes close to a square as shown in Fig. 1, and the difference in dimensions between the major axis and the minor axis is largely eliminated. Therefore, the load generated in the shielding layer 8 when the communication cable 1 is bent is uniformly distributed, and breakage of the shielding layer 8 is suppressed. As a result, this contributes to improving the bending resistance of the communication cable 1.

[0042] Furthermore, the presence of the intervening wire 6 also contributes to making the communication cable 1 thinner, as will be described below.

[0043] 9, when a shield layer 68 is provided on a twisted pair 65 in which only the signal wires 62 are twisted together, the shield layer 68 is in close proximity to the signal wires 62, and two spaces are formed surrounded by the two signal wires 62 and the shield layer 68. On the other hand, when a shield layer 8 is provided on a twisted pair 5 in which an intervening wire 6 is also twisted together, the presence of the intervening wire 6 creates four spaces surrounded by the signal wire 2, the intervening wire 6, and the shield layer 8, in addition to the two spaces surrounded by the two signal wires 2 and the intervening wire 6.

[0044] The formed spaces act to reduce the effective dielectric constant of the twisted pair 5 surrounded by the shield layer 8, and the more spaces that are formed, the greater the reduction in the effective relative dielectric constant.

[0045] When setting the characteristic impedance of the twisted pair 5, the inter-conductor distance needs to be adjusted depending on the effective dielectric constant of the twisted pair 5. However, when the effective dielectric constant decreases, the inter-conductor distance required to set a predetermined characteristic impedance becomes shorter, so that the outer diameter of the signal line 2 can be made thinner, and as a result, the outer diameter of the twisted pair 5 can be made thinner.

[0046] In other words, the presence of the intervening wires 6 in the twisted pair wire 5 creates a lot of space, which significantly reduces the effective dielectric constant and allows the outer diameter to be made smaller than when the intervening wires 6 are not twisted, thereby contributing to the reduction in the diameter of the communication cable 1 using the twisted pair wires 5.

[0047] Additionally, since the signal attenuation due to dielectric loss is suppressed as the effective relative dielectric constant decreases, the presence of the intervening wire 6 also contributes to improving communication characteristics.

[0048] As described above, the twisted pair wire 15 in which the signal wires 12 and the intermediate wires 16 are alternately twisted together contributes to maintaining the communication characteristics even when the communication cable 10 is constructed using an assembly wire in which multiple twisted pair wires 15 are twisted together, as shown in FIG. 2.

[0049] In communication cable 10 having multiple twisted pairs 15 as shown in Figure 2, if the twisted pairs 15 are close to each other, crosstalk attenuation is likely to occur in which a signal transmitted through signal line 12 constituting one twisted pair 15 is transmitted to signal line 12 constituting the other twisted pair 15, and the communication characteristics of communication cable 10 are degraded due to crosstalk attenuation.

[0050] When the twist pitch of each twisted pair 15 constituting the communication cable 10 is set to a different value for each twisted pair 15, as long as the outer diameter circles of the twisted pairs 15 are close enough to touch as shown in Figure 4, no crosstalk attenuation that would significantly degrade the communication characteristics is observed, and the communication characteristics of the communication cable 10 are maintained.

[0051] However, as shown in FIG. 10, in a communication cable 70 having no intervening wire, when twisted pairs 75 are close enough to each other that the outer diameter circles of the twisted pairs 75 overlap, crosstalk attenuation increases, and it has been confirmed that communication characteristics deteriorate especially when one of the signal wires 72 constituting one twisted pair 75 enters the gap between the two signal wires 72 constituting the other twisted pair 75 and comes into contact with the two signal wires 72 constituting the other twisted pair 75.

[0052] In the present invention, by twisting the twisted pair 15 with the intermediate wire 16, abnormal proximity of the signal wires 12 that make up the twisted pair 15 is restricted, and crosstalk attenuation is suppressed, thereby maintaining the communication characteristics of the communication cable 10.

[0053] The twisted pair 15 of the communication cable 10 used in the present invention has a pair of signal wires 12 and a pair of intervening wires 16, and has a structure in which the signal wires 12 and the intervening wires 16 are twisted together so that they are arranged alternately. As a result, the twisted pair 15 does not enter the gap between the two signal wires 72 that constitute the other twisted pair 75 as shown in FIG. 10 and does not come into contact with the two signal wires 72 that constitute the other twisted pair 75, and the specified communication characteristics can be maintained.

[0054] The abnormal approach of the twisted pair 75 shown in FIG. 10 is likely to occur when the communication cable 70 is bent, so by twisting the twisted pair 15 with the intermediate wire 16, the deterioration of communication characteristics due to bending is suppressed.

[0055] In addition, since the interposer wire 16 is twisted with the signal wire 12 and exists within the outer sheath 17, the communication cable 10 of the present invention has superior bending resistance compared to the communication cable 50 that uses a cross interposer.

[0056] In addition, in the present invention, as shown in FIG. 3, it is preferable that the pair of signal wires 2, 12 constituting the twisted pair wires 5, 15 are twisted together so that the signal wires 2, 12 are in contact with each other when viewed in cross section.

[0057] Because the pair of signal wires 2, 12 that make up the twisted pair 5, 15 are in contact with each other, the electromagnetic induction noise radiation suppression effect and external electromagnetic induction noise shielding effect of the twisted pair 5, 15 due to the structure of the twisted pair 5, 15 are stabilized, contributing to maintaining communication characteristics.

[0058] In addition, in the present invention, it is preferable that the outer diameter of the intervening wires 6, 16 is smaller than the outer diameter of the signal wires 2, 12. By making the outer diameter of the intervening wires 6, 16 smaller than the outer diameter of the signal wires 2, 12, the intervening wires 6, 16 are prevented from interfering with the contact of the signal wires 2, 12 constituting the twisted pair wires 5, 15, and the outer diameter of the twisted pair wires 5, 15 is also reduced, contributing to a reduction in the diameter of the communication cables 1, 10.

[0059] The outer diameter of the intermediate wires 6 and 16 is R 1 , the outer diameter of the signal wires 2 and 12 is R 2 When the outer diameter R of the intermediate wire 6, 16 is defined as 1 is preferably in the range shown in the following formula 1.

[0060] TIFF0007640216000004.tif29110

[0061] Outer diameter R of the intervening wire 16 1 Since is within the range of formula 1, even if twisted pairs 15 are close to each other in communication cable 10 in which multiple twisted pairs 15 are twisted together, it is possible to prevent signal lines 12 constituting twisted pairs 15 from being close to each other to the extent that it would affect the communication characteristics, thereby contributing to maintaining the communication characteristics.

[0062] In addition, R 1 is preferably in the range shown in the following formula 2.

[0063] TIFF0007640216000005.tif2671

[0064] Outer diameter R of intervening wire 6, 16 1 Since the outer diameter R of the twisted pair wires 5 and 15 is within the range of the formula 2, the increase in the outer diameter R of the twisted pair wires 5 and 15 due to the presence of the intervening wires 6 and 16 is suppressed, which contributes to the reduction in the diameter of the communication cables 1 and 10. 1is near the upper limit value of Equation 2, twisted pairs 15 will have a circular shape overall, and the gaps between twisted pairs 15 will be reduced when outer sheath 17 is provided in communication cable 10 in which multiple twisted pairs 15 are twisted together. As a result, the positional relationship of twisted pairs 15 is less likely to be lost when communication cable 10 is bent, which contributes to maintaining the communication characteristics.

[0065] In summary, R which is particularly preferred in the present invention 1 The range is shown in the following formula 3.

[0066] TIFF0007640216000006.tif30147

[0067] Outer diameter R of intervening wire 6, 16 1 is within the range of Equation 3, it is possible to prevent the signal wires 2, 12 from coming close to each other to an extent that would affect the communication characteristics, and it is also possible to prevent an increase in the outer diameter of the twisted pair wires 5, 15 due to the presence of the intervening wires 6, 16, which contributes to achieving both the maintenance of communication characteristics and a reduction in diameter.

[0068] The intermediate wires 6, 16 used in the present invention are preferably made of a material with excellent sliding properties. By using the intermediate wires 6, 16 with excellent sliding properties, frictional resistance is reduced between the twisted pairs 5 and the inner peripheral surface of the outer jacket 7, and also between the twisted pairs 15 when multiple twisted pairs 15 are used, and the sliding of the twisted pairs 5, 15 that occurs when the communication cable 1, 10 is bent becomes smooth. As a result, the load generated in the twisted pairs 5, 15 is reduced, and breakage of the signal lines 2, 12 due to bending can be suppressed, which contributes to improving the bending resistance of the communication cable 1, 10.

[0069] In addition, in the case where the tape layer 19 or the noise-preventing shielding layers 8, 18 described later are provided between the twisted pair wires 5, 15 and the outer jackets 7, 17, the use of a material with excellent sliding properties for the intermediate wires 6, 16 suppresses damage due to wear of the tape layer 19 and the shielding layers 8, 18, which also contributes to maintaining the communication characteristics.

[0070] Specifically, it is preferable to use a material having a dynamic friction coefficient of 0.3 or less for the intermediate wires 6, 16. Examples of materials having a dynamic friction coefficient of 0.3 or less include fluororesin, polyethylene, and nylon 66.

[0071] It is more preferable to use a material whose static friction coefficient is equal to or less than the kinetic friction coefficient for the intermediate wires 6, 16. Although the static friction coefficient of general materials is greater than the kinetic friction coefficient, some sliding materials have a static friction coefficient equal to or less than the kinetic friction coefficient. By using such a material for the intermediate wires 6, 16, the sliding of the twisted pair wires 5, 15 that occurs when the communication cables 1, 10 are bent becomes smoother, which contributes to improving the bending resistance of the communication cables 1, 10.

[0072] In the present invention, the "material whose static friction coefficient is equal to or less than the kinetic friction coefficient" refers to a material that exhibits a property in which the static friction coefficient is equal to or less than the kinetic friction coefficient when two identical materials are brought into contact and slid against each other. The kinetic friction coefficient and static friction coefficient in the present invention are values ​​measured in accordance with JIS K 7125.

[0073] In addition, it is preferable that the elongation of the intervening wires 6, 16 is equal to or greater than the elongation of the signal wires 2, 12. By making the elongation of the intervening wires 6, 16 equal to or greater than the elongation of the signal wires 2, 12, breakage of the intervening wires 6, 16 when bent is suppressed, which contributes to maintaining the communication characteristics when the communication cables 1, 10 are bent.

[0074] It is more preferable that the elongation of the intermediate wires 6, 16 is 10 times or more that of the signal wires 2, 12. When the elongation of the intermediate wires 6, 16 is sufficiently greater than that of the signal wires 2, 12, the effect of preventing breakage of the intermediate wires 6, 16 when bent and the effect of maintaining communication characteristics are improved.

[0075] The intervening wires 6, 16 used in the present invention can be appropriately selected from monofilament and multifilament wires.

[0076] From the viewpoint of maintaining communication characteristics, it is preferable to use monofilament intermediate wires 6, 16 that are difficult to deform when bent. By using monofilament intermediate wires 6, 16 that are difficult to deform, compression of the insulating layers 4, 14 in the twisted pairs 5, 15 and, when multiple twisted pairs 15 are used, the approach of the twisted pairs 15 are also suppressed, which contributes to maintaining communication characteristics, and the monofilament intermediate wire 16 is preferable in that it has few surface irregularities and has excellent sliding properties.

[0077] A specific material for the intermediate wires 6, 16 that is particularly preferably used in the present invention is PTFE, a type of fluororesin. PTFE has a static friction coefficient equal to or less than the dynamic friction coefficient, and has excellent mechanical strength, such as high elongation. In addition, since PTFE has a small dielectric constant, transmission loss is suppressed when twisted with the signal wires 2, 12, which contributes to maintaining communication characteristics.

[0078] Other fluororesins such as PFA, FEP, and ETFE also have a static friction coefficient equal to or less than the dynamic friction coefficient, and also have high elongation and low dielectric constant, and therefore can be preferably used in the present invention.

[0079] From the viewpoint of maintaining the communication characteristics, the intermediate wires 6, 16 may have a porous structure or a hollow structure. Since the porous structure and the hollow structure contain air, they have a lower dielectric constant than the solid structure, which contributes to maintaining the communication characteristics, and also has excellent flexibility, which contributes to improving bending resistance.

[0080] As the porous structured intervening wires 6, 16, expanded PTFE, which is expanded during the manufacturing process to form a porous structure with nodes and fibrils, can be preferably used. Expanded PTFE has excellent mechanical strength against elongation, and can therefore be preferably used from the viewpoint of improving bending resistance.

[0081] The hollow structured intervening wires 6, 16 may be made of fluororesin extruded into a tube shape.

[0082] In addition, the intermediate wires 6, 16 having a low dielectric constant can be preferably used from the viewpoint of making the communication cables 1, 10 thinner.

[0083] One example of a communication cable is a LAN cable (communication cable 10) that uses four twisted pairs of wires. Conventional LAN cables have an outer diameter of about 5 to 7 mm, and cables with an outer diameter of 5 mm or less tend to be considered thin cables.

[0084] When the outer diameter of the LAN cable is set to 5 mm or less, the outer diameter of the twisted pair 15 is preferably set to 1 mm or less, and the effective relative dielectric constant must be sufficiently small to reduce the outer diameter of the twisted pair 15. By using an intervening wire 16 with a low dielectric constant and combining this with the effect of reducing the effective relative dielectric constant due to the presence of the space formed by the intervening wire 16, the effective relative dielectric constant of the twisted pair 15 can be sufficiently small.

[0085] In order to make the outer diameter of the twisted pair wire 15 1 mm or less, the intermediate wire 16 should be made of a material with a dielectric constant of 2.4 or less, and various types of fluororesin can be preferably used. Among the fluororesins, PTFE is particularly preferably used.

[0086] When constructing communication cable 10 using multiple twisted pairs 15, the twist direction of twisted pairs 15 may be the same for twisted pairs 15, or twisted pairs 15 with different twist directions may be combined.

[0087] From the viewpoint of maintaining communication characteristics, it is preferable to combine twisted pairs 15 with different twisting directions. By making the twisting directions of twisted pairs 15 different, the directions of the projections and recesses on the surface of twisted pairs 15 differ, and it is possible to prevent the outer diameter circles of twisted pairs 15 from coming too close to overlap.

[0088] In the present invention, the presence of the intervening wire 16 can prevent the outer diameter circles of the twisted wire pairs 15 from coming too close together and overlapping, so the present invention is particularly suitable for use in aligning the twisting direction of the twisted wire pairs 15.

[0089] The conductors 3, 13 used in the present invention can be appropriately selected from known conductors for electric wires and cables. From the viewpoint of resistance to bending and twisting, it is preferable to select a conductor having excellent resistance to bending and twisting.

[0090] The insulating layers 4, 14 used in the present invention can be appropriately selected from known insulating materials for electric wires and cables. From the viewpoint of bending resistance, fluororesins such as PTFE, PFA, FEP, and ETFE can be preferably used, as with the intermediate wires 6, 16.

[0091] In addition, the communication cables 1, 10 of the present invention can further improve bending resistance by combining the material of the intermediate wires 6, 16 that constitute the twisted pair wires 5, 15 with the material of the insulating layers 4, 14 used in the signal wires 2, 12.

[0092] One example is a mode in which the insulating layers 4, 14 are made of a material having a greater flexural modulus than the intervening wires 6, 16. Since the insulating layers 4, 14 have a greater flexural modulus than the intervening wires 6, 16, when the communication cable 1, 10 is bent, the intervening wires 6, 16 are more deformed than the insulating layers 4, 14. As a result, the load caused by bending is mainly absorbed by the intervening wires 6, 16, which contributes to preventing damage to the insulating layers 4, 14 and breakage of the conductors 3, 13.

[0093] Another example is a mode in which the insulating layers 4, 14 are made of a material having a smaller tensile modulus than the intervening wires 6, 16. When the communication cable 1, 10 is bent, a force is generated that pulls the twisted pair wires 5, 15 toward both sides of the bent portion. At this time, since the tensile modulus of the insulating layers 4, 14 is smaller than that of the intervening wires 6, 16, the insulating layers 4, 14 constituting the signal lines 2, 12 twisted together with the intervening wires 6, 16 are unlikely to be tensilely deformed until the intervening wires 6, 16 start to tensilely deform. In other words, the load due to tension is mainly absorbed by the intervening wires 6, 16, which contributes to suppressing damage to the insulating layers 4, 14 and breakage of the conductors 3, 13.

[0094] When using the PTFE intervening wires 6, 16 which are particularly preferably used in the present invention, a material which can be preferably used for the insulating layers 4, 14 is FEP which tends to have a higher flexural modulus and a lower tensile modulus than PTFE.

[0095] In addition, an embodiment in which the insulating layers 4, 14 and the intervening wires 6, 16 are made of the same material can also be preferably used. When the insulating layers 4, 14 and the intervening wires 6, 16 are made of the same material, the load generated in the signal lines 2, 12 and the intervening wires 6, 16 when the communication cable 1, 10 is bent is distributed approximately evenly between the signal lines 2, 12 and the intervening wires 6, 16, and thus the concentration of the load on the signal lines 2, 12 is suppressed, which contributes to suppressing damage to the insulating layers 4, 14 and breakage of the conductors 3, 13.

[0096] Examples of the configuration in which the insulating layers 4, 14 and the intervening wires 6, 16 are made of the same material include a configuration in which both use FEP, and a configuration in which both use PFA.

[0097] In the above description, insulated electric wires having conductors 3, 13 covered with insulating layers 4, 14 are used as the signal wires 2, 12. However, the structure of the signal wires 2, 12 is not limited to this, and known coaxial cables can also be used as the signal wires 2, 12.

[0098] The outer coverings 7 and 17 can be appropriately selected from known cable covering materials such as PVC and silicone rubber.

[0099] 2, a tape layer 19 for covering the twisted pair 15 and a shielding layer 18 for noise suppression may be provided between the twisted pair 15 and the jacket 17. Also, although the present invention is primarily intended to provide a communication cable with excellent communication characteristics without using a cross insert, a modified version using a cross insert may be adopted as necessary.

[0100] In the following, communication cables 1 and 10 each configured using one or four twisted pair wires 5 and 15 will be described as embodiments of the present invention. EXAMPLES

[0101] As shown in FIG. 2, the communication cable 10 of the first embodiment uses four twisted pairs 15, and the signal lines 12 and the intermediate lines 16 used in the twisted pairs 15 have a common design for each twisted pair 15.

[0102] The signal wire 12 was prepared by covering the outer circumference of the conductor 13 made of tin-plated soft copper wire with a diameter of 0.26 mm with FEP to form the insulating layer 14 with a thickness of 0.16 mm using an extrusion molding machine, resulting in an outer diameter of 0.58 mm. The elongation of the signal wire 12 was less than 10%.

[0103] A PTFE fiber having a diameter of 0.38 mm was prepared as the intermediate wire 16. The diameter of this intermediate wire 16 was approximately equal to the upper limit of the range shown in the above formula 2. The elongation of the intermediate wire 16 was 200% or more.

[0104] The twisted pair 15 has two signal wires 12 and two intermediate wires 16, and the signal wires 12 and the intermediate wires 16 are twisted together so that they are arranged alternately. The pitch is changed depending on the twisted pair 15, and four types of twisted pair 15 are prepared.

[0105] The twisting direction of the twisted pairs 15 was the same for all pairs. When the twisting of each pair of twisted pairs 15 was completed, the signal wires 12 were in contact with each other when viewed in cross section, and the outer diameter was 1.2 mm.

[0106] The four types of twisted pairs 15 thus prepared were twisted together to form an assembly wire. The twisting direction was opposite to that of the twisted pairs 15. The diameter of the twisted pairs 15 was 2.8 mm.

[0107] An aluminum-laminated PET (polyethylene terephthalate) tape was wound transversely around the outer periphery of the total twisted pair wires 15 as a tape layer 19 .

[0108] Next, the shield layer 18 is provided on the outer periphery of the tape layer 19. The shield layer 18 is a braided shield made up of 16 wire bundles, with each bundle consisting of eight shield wires pulled parallel to each other, and the shield wires are made of copper foil thread with an outer diameter of 0.08 mm.

[0109] Finally, an extrusion molding machine was used to cover the outer circumference of shield layer 18 with PVC (polyvinyl chloride) to a thickness of 0.4 mm to become outer sheath 17, completing communication cable 10 of Example 1. The outer diameter of communication cable 10 was finally 4 mm. EXAMPLES

[0110] The communication cable of Example 2 has the same structure as Example 1, and will be described with reference to Fig. 2. The communication cable 10 of Example 2 uses four twisted pairs 15, and the signal lines 12 and the intermediate lines 16 used in the twisted pairs 15 have a common design for each twisted pair 15.

[0111] The signal wire 12 was prepared by covering the outer circumference of a conductor 13 having an outer diameter of 0.24 mm, which was made by concentrically twisting seven tin-plated soft copper wires having a diameter of 0.08 mm, with FEP to a thickness of 0.095 mm, which would become an insulating layer 14, using an extrusion molding machine, to give an outer diameter of 0.43 mm. The elongation of the signal wire 12 was less than 10%.

[0112] A PTFE fiber having a diameter of 0.42 mm was prepared as the intermediate wire 16. The diameter of this intermediate wire 16 was approximately the same as the diameter of the signal wire 12, and was outside the range indicated by the above formula 2. The elongation of the intermediate wire 16 was 200% or more.

[0113] The twisted pair 15 has two signal wires 12 and two intermediate wires 16, and the signal wires 12 and the intermediate wires 16 are twisted together so that they are arranged alternately. The pitch is changed depending on the twisted pair 15, and four types of twisted pair 15 are prepared.

[0114] The twisting direction of the twisted pairs 15 was all the same. In addition, when the twisting of each twisted pair 15 was completed, the signal wires 12 were in contact with each other when viewed in cross section, and the outer diameter was 0.9 mm.

[0115] The four types of twisted pairs 15 thus prepared were twisted together to form an assembly wire. The twisting direction was opposite to that of the twisted pairs 15. The diameter of the twisted pairs 15 was 2.8 mm.

[0116] An aluminum-laminated PET (polyethylene terephthalate) tape was wound transversely around the outer periphery of the total twisted pair wires 15 as a tape layer 19 .

[0117] Next, the shield layer 18 is provided on the outer periphery of the tape layer 19. The shield layer 18 is a braided shield made up of 16 wire bundles, with each bundle consisting of eight shield wires pulled parallel to each other, and the shield wires are made of copper foil thread with an outer diameter of 0.08 mm.

[0118] Finally, an extrusion molding machine was used to cover the outer circumference of the shield layer 18 with PVC (polyvinyl chloride) to a thickness of 0.4 mm to become the outer jacket 17, thereby completing the communication cable 10 of Example 2. The outer diameter of the communication cable 10 was finally 4 mm. EXAMPLES

[0119] The communication cable 1 of the third embodiment uses only one twisted pair wire 5 as shown in FIG.

[0120] The signal wire 2 was prepared by covering the outer circumference of a conductor 3 made of a bunched strand of three 0.05 mm diameter tin-plated copper alloy wires twisted together with seven twisted strands, with an insulating layer 4 of FEP 0.15 mm thick, using an extrusion molding machine, to give an outer diameter of 0.58 mm. The elongation of the signal wire 2 was less than 10%.

[0121] A PTFE fiber having a diameter of 0.38 mm was prepared as the intermediate wire 6. The diameter of this intermediate wire 6 was approximately equal to the upper limit of the range shown in the above formula 2. The elongation of the intermediate wire 6 was 200% or more.

[0122] Two signal wires 2 and two intermediate wires 6 were twisted together so that the signal wires 2 and the intermediate wires 6 were arranged alternately to form a twisted pair wire 5. When the twisting was completed, the completed twisted pair wire 5 had the signal wires 2 in contact with each other when viewed in cross section, and had an outer diameter of 1.2 mm.

[0123] Next, a shield layer 8 is provided on the outer periphery of the signal wire 2 and the intermediate wire 6. The shield layer 8 is a braided shield made up of 24 wire bundles, with each bundle consisting of seven shield wires pulled parallel to each other, and the shield wires are made of copper foil thread with an outer diameter of 0.08 mm.

[0124] Finally, an extrusion molding machine was used to cover the outer circumference of the shield layer 8 with PVC (polyvinyl chloride) to become the outer jacket 7 with a thickness of 0.4 mm, thereby completing the communication cable 1 of Example 3. The outer diameter of the communication cable 1 was finally 2.3 mm.

[0125] [Comparative Example] As a comparative example of a communication cable for Example 3, a communication cable was prepared similarly to the communication cable of Example 3, except that the intervening wire 6 was omitted from the communication cable 1 of Example 3.

[0126] The transmission characteristics of the communication cables of the embodiment and the comparative example prepared as described above were compared before and after the bending resistance test. Note that, since there are differences in durability and evaluable items due to differences in dimensions and structures between the communication cables 10 of the embodiment 1 and 2, which are composed of multiple twisted pairs 15, and the communication cables of the embodiment 3 and the comparative example, which are composed of a single twisted pair 5, the test conditions and evaluation items were partially changed in consideration of this, as described in detail below.

[0127] [Transmission characteristic evaluation method for Examples 1 and 2] The NEXT (Near End Cross Talk) of the communication cable 10 was evaluated in accordance with a method conforming to TIA / EIA-568-B.2-1, and the transmission characteristics were evaluated based on the size of the minimum margin for NEXT required for Category 6A communication cables.

[0128] [Flexibility test method for Examples 1 and 2] The bending resistance of the communication cable 10 was evaluated using a bending test apparatus 100 shown in Fig. 5. The test conditions were as follows: a 1000 mm long communication cable 10, with its upper part fixed by a fixing part 101 and a load 103 of 500 g attached, was lightly clamped between mandrels 102 with a radius of 20 mm, and was bent 90 degrees to the left and right at a rate of 60 times per minute. Each bend of 90 degrees to the left and right counts as one bend, and the NEXT after 100,000 bends was measured and compared with the NEXT before bending.

[0129] The design and evaluation results of the communication cables 10 of Examples 1 and 2 are shown in Table 1, and NEXT of Examples 1 and 2 before and after the bending resistance test are shown in FIGS. 6A, 6B, 7A, and 7B, respectively.

[0130] [Table 1]

[0131] The communication cable 10 of Example 1 has a minimum margin of +8.9 dB relative to the standard value of Category 6A, and this value did not change even after the bending resistance test. From this, it can be said that the communication cable 10 of Example 1 is a communication cable with excellent bending resistance, which maintains its communication characteristics even after repeated bending.

[0132] The communication cable 10 of Example 2 had a minimum margin of +4.3 dB relative to the standard value for Category 6A, and this value decreased to +3.8 dB after the bending resistance test. From this, although the communication characteristics of the communication cable 10 of Example 2 deteriorate when repeatedly bent, since the margin for the required characteristics of Category 6A still exists, it can be said that the communication cable is a communication cable for Category 6A with practical bending resistance, and at the same time, it can be said that the communication cable has sufficient performance as a communication cable for Category 6.

[0133] From the results of Examples 1 and 2, it can be said that it is preferable in terms of communication characteristics and bending resistance to make the diameter of the intermediate wire 16 that constitutes the twisted pair wire 15 smaller than the diameter of the signal wire 12 based on the above formula 2, rather than making it approximately the same as the diameter of the signal wire 12.

[0134] [Method of evaluating transmission characteristics for Example 3 and Comparative Example] The transmission characteristics were evaluated based on the conductor resistance value of the signal wire 2 that constitutes the communication cable 1. The conductor resistance value was measured by contacting the conductors 3 of the two signal wires 2 that constitute the communication cable 1 at one end of the communication cable 1 that had been cut to a specified length, and by connecting the positive test lead of a tester to the conductor 3 of one signal wire 2 and the negative test lead to the conductor 3 of the other signal wire 2 at the other end of the communication cable 1. The measurements were performed at room temperature, and the transmission characteristics were evaluated. Note that the higher the conductor resistance value, the worse the transmission characteristics.

[0135] [Test method for bending resistance for Example 3 and Comparative Example] The bending resistance of the communication cable 1 of Example 3 was also evaluated using a bending resistance test device 100 shown in Fig. 5. The test conditions were as follows: the communication cable 1, 1000 mm long, fixed at the top by a fixing part 101 and with a load 103 of 100 g attached, was lightly clamped between mandrels 102 with a radius of 3 mm, and bent 90 degrees to the left and right at a rate of 90 times / min. Each bend of 90 degrees to the left and right was counted as one bend, and the change in the conductor resistance value with the increase in the number of bends was investigated and compared with the conductor resistance value before bending.

[0136] Table 2 shows the designs and evaluation results of the communication cables 1 of Example 3 and Comparative Example.

[0137] [Table 2]

[0138] The conductor resistance value of the communication cable 1 of Example 3 was 600 mΩ, a value that does not cause any inconvenience when used as a communication cable, and did not change when the number of bending times reached 16,000, but rose to 612 mΩ when the number of bending times reached 160,000. The increase was 2%, which is an increase that does not cause any particular inconvenience when used as a communication cable. In addition, no breaks were confirmed in the conductor 3 that constitutes the signal line 2.

[0139] On the other hand, the conductor resistance value of the communication cable of the comparative example was 600 mΩ before the bending resistance test, the same as that of Example 3, but when the number of bending times reached 16,000, it increased by more than 10% to 690 mΩ, and at the same time, breakage of the conductor was also confirmed. It is presumed that in the communication cable of the comparative example, breakage of the conductor progressed due to the load caused by bending, causing the conductor resistance value to increase, while in the communication cable 1 of Example 3, the intermediate wire 6 absorbed the load caused by bending, reducing the load on the conductor 3 and suppressing the progression of breakage.

[0140] From this, it can be said that the communication cable 1 of Example 3 is a communication cable with excellent bending resistance, in which the communication characteristics are maintained even after repeated bending.

[0141] As described above, the inventor has thoroughly studied the structure of communication cables and has found that sufficient communication characteristics for practical use can be obtained if compression of the coating of the signal wires in the twisted pair that makes up the communication cable is suppressed and if the signal wires that make up the twisted pair adjacent to the signal wires do not sag into the gaps between the signal wires.He has thus obtained a communication cable in which compression of the coating and sagging of the signal wires are suppressed and which also has improved durability against bending.

[0142] The communication cable of the present invention is expected to provide the following excellent effects. (1) Compression of the coating of the signal wires that make up the twisted pair cable is suppressed, and a specified inter-conductor distance is maintained even when the cable is bent, thereby maintaining specified communication characteristics. (2) It is possible to obtain the desired communication characteristics while minimizing the change in the outer diameter of the twisted pair wire, which contributes to making communication cables thinner. (3) When a communication cable is constructed using multiple twisted pairs of wires, it has excellent communication characteristics even without using a cross-shaped insert, and since there is no cross-shaped insert, it has improved bending resistance compared to a communication cable that uses a cross-shaped insert. (4) When a communication cable is constructed using multiple twisted pairs, abnormal proximity of the twisted pairs is suppressed, and the specified communication characteristics are maintained even if the communication cable is bent.

[0143] This application is based on Japanese Patent Application No. 2019-085722 filed on April 26, 2019. The entire specification, claims, and drawings of Japanese Patent Application No. 2019-085722 are incorporated herein by reference.

[0144] The present invention allows various embodiments and modifications without departing from the broad spirit and scope of the present invention. The above-described embodiments are for the purpose of explaining the present invention and do not limit the scope of the present invention. That is, the scope of the present invention is indicated by the claims, not the embodiments. Various modifications made within the scope of the claims and within the scope of the meaning of the invention equivalent thereto are considered to be within the scope of the present invention. [Industrial Applicability]

[0145] As described above, the communication cable of the present invention is suitable for use in the moving parts of various industrial devices such as robots, including industrial robots and various service robots such as humanoids, and semiconductor manufacturing equipment; however, its uses are not limited to these, and it can also be suitably used as a communication cable used for parts other than moving parts, or as a power cable for moving parts that does not involve communication. [Explanation of symbols]

[0146] 1. Communication cable 2. Signal line 3. Conductor 4. Insulation layer 5... Twisted pair wire 6...Intervening line 7...Outer cover 8. Shielding layer 10. Communication cable 12 Signal line 13 Conductor 14. Insulation layer 15... Twisted pair wire 16...intervening line 17... Outer cover 18. Shielding layer 19 Tape layer

Claims

1. A communication cable having a twisted pair wire formed by twisting together signal wires each having an insulating layer covering a conductor, and an assembly wire formed by twisting together a plurality of said twisted pair wires, the assembly wire being covered with an outer jacket, the twisted pair wire has a pair of the signal wires and a pair of the intermediate wires, the signal wires and the intermediate wires being twisted together so as to be arranged alternately; When the twisted pair is viewed in cross section along a plane perpendicular to the longitudinal direction, a pair of signal wires constituting the twisted pair are in contact with each other, The intermediate wire is a monofilament, and when the outer diameter of the intermediate wire is defined as R1 and the outer diameter of the signal wire is defined as R2, the communication cable satisfies the relationship of Equation 2.

2. 2. The communication cable according to claim 1, further comprising a shielding layer provided between the wire assembly and the outer sheath.

3. 3. The communication cable according to claim 1, wherein when the outer diameter of the intermediate wire is defined as R1 and the outer diameter of the signal wire is defined as R2, the relationship of Equation 3 is satisfied.

4. 4. The communication cable according to claim 1, wherein the elongation of the intervening wire is equal to or greater than the elongation of the signal wire.

5. 5. The communication cable according to claim 1, wherein the elongation of the intermediate wire is 10 times or more that of the signal wire.

6. 6. The communication cable according to claim 1, wherein the intermediate wire is made of a material having a dynamic friction coefficient of 0.3 or less.

7. 7. The communication cable according to claim 1, wherein the intermediate wire is made of a material whose static friction coefficient is equal to or less than its kinetic friction coefficient.

8. The communication cable according to any one of claims 1 to 7, characterized in that it is bent at a movable portion.

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