Composite Cable

Abstract

To provide a composite cable including a signal line and a power line put together into one.SOLUTION: A composite cable includes a stranded wire including a plurality of signal lines that are entwisted, a plurality of power lines of which number is more than that of the signal lines, and a sheath that covers the circumference of an aggregate including the stranded wire and the power lines that are entwisted altogether. The stranded wire is disposed separate from the power lines, opposite to the cable diameter direction. The power lines are disposed in an arc shape along the circumferential direction of the cable from a position opposed to the stranded wire.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a composite cable. [Background technology]

[0002] Conventionally, composite cables that combine a signal line for signal transmission and a power line for power supply are known. For example, Patent Document 1 discloses a composite cable in which a pair of signal lines is twisted together to form a twisted pair, and a cable core is formed by twisting a plurality of power lines together. The composite cable of Patent Document 1 is used, for example, as wiring for vehicles such as automobiles. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-47599 A Summary of the Invention [Problem to be solved by the invention]

[0004] Meanwhile, industrial robots such as robot arms used in factories are becoming smaller, and the servo motors and other parts used in industrial robots are also becoming smaller. Since it is difficult to connect multiple cables to a small servo motor, and the wiring space for cables in industrial robots tends to be narrow, there is a demand for a composite cable that combines a signal line and a power line into one cable to connect to a servo motor, instead of using a separate cable for power supply and a cable for signal transmission.

[0005] Therefore, an object of the present invention is to provide a composite cable in which a signal line and a power line are combined into a single cable. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems, the present invention provides a composite cable comprising: a twisted wire in which a plurality of signal wires are twisted together; a first power line unit formed by arranging a plurality of first power wires adjacent to each other in a circumferential direction of the cable; a second power line unit having an even number of second power wires; and a sheath that collectively covers an assembly in which the twisted wire, the plurality of first power wires, and the plurality of second power wires are twisted together, wherein the twisted wire and the first power line unit are arranged opposite each other in a diameter direction of the cable, and the second power line unit is configured such that an equal number of the second power wires are arranged opposite each other between the twisted wire and the first power line unit in the circumferential direction of the cable, and the rigidity of the first power line unit is between 1 and 1.5 times the rigidity of the twisted wire. Effect of the Invention

[0007] According to the present invention, it is possible to provide a composite cable in which a signal line and a power line are integrated into one cable. [Brief description of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view showing a cross section perpendicular to the longitudinal direction of a composite cable according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] [Embodiment Mode] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0010] FIG. 1 is a cross-sectional view showing a cross section perpendicular to the longitudinal direction of the composite cable according to the present embodiment. The composite cable 1 is a cable that combines a signal line for signal transmission and a power line for power supply, and is connected to, for example, a servo motor of an industrial robot and is used to transmit signals and supply power to the servo motor. The signal line is used, for example, to transmit signals in a frequency band of 1 MHz or more. The power line is used, for example, to supply a current of about several amperes. By transmitting or supplying such signals or currents between the servo motor and the movable part of the industrial robot, the movable part of the industrial robot is repeatedly moved and stopped at high speed. Note that the use of the composite cable 1 is not limited to this.

[0011] In addition, since industrial robots are used in factories, etc., it is expected that composite cables connected to servo motors of industrial robots will perform long-distance transmission, for example, up to about 100 m. Therefore, composite cables used for such purposes are required to have good electrical properties that enable long-distance transmission. For example, it is possible to increase the outer diameter of the composite cable to accommodate long-distance transmission, but in this case, bending resistance and twisting resistance decrease. Therefore, composite cables are required to enable long-distance transmission without increasing the outer diameter of the composite cable (for example, with an outer diameter of 9.0 mm or less), and to have excellent bending resistance and twisting resistance.

[0012] As shown in Fig. 1, the composite cable 1 includes a twisted pair wire 2 formed by twisting a pair of signal wires 21 as a twisted wire formed by twisting a plurality of signal wires 21 together, a first power line unit 3 formed by arranging a plurality of first power wires 31 adjacent to each other in the circumferential direction of the cable, a second power line unit 4 having an even number of second power wires 41, and a sheath 9 that collectively covers the periphery of an assembly (cable core) 5 formed by twisting the twisted pair wire 2, the plurality of first power wires 31, and the plurality of second power wires 41. Note that, in the composite cable 1 shown in Fig. 1, the twisted pair wire 2 formed by twisting a pair of signal wires 21 is used as the twisted wire, but is not limited thereto. The twisted wire may be, for example, a wire formed by twisting two or more signal wires 21 together, or a wire formed by twisting a plurality of twisted pair wires 2 formed by twisting a pair of signal wires 21 together.

[0013] The signal line 21 used in the twisted pair wire 2 has a signal line conductor 21a and a signal line insulator 21b that covers the signal line conductor 21a. The signal line conductor 21a is made of a twisted conductor in which multiple metal wires are twisted together. The signal line 21 used as the twisted pair wire 2 is more likely to receive stress when bent or twisted than the first power line 31 and the second power line 41 used without twisting, so higher bending resistance and twisting resistance are required. Therefore, in this embodiment, a composite twisted wire in which multiple child twisted wires in which multiple metal wires are twisted together are further twisted is used as the signal line conductor 21a. As the metal wire used in the signal line conductor 21a, a tin-plated soft copper wire with an outer diameter of 0.8 mm or less can be used. The number of metal wires used in the signal line conductor 21a is preferably 100 or more and less than the number of metal wires used in the first conductor 31a and the second conductor 41a. By using such a signal conductor 21a, it is possible to effectively improve the balance of the rigidity of the composite cable 1 and thereby improve the bending resistance and twisting resistance.

[0014] In order to realize good electrical characteristics that allow long-distance transmission, it is desirable to use a signal line insulator 21b having as low a dielectric constant as possible. In this embodiment, the signal line insulator 21b made of foamed propylene is used. In order to realize high bending resistance and twisting resistance, the tensile strength of the signal line insulator 21b is desirably 25 MPa or more, and the elongation is desirably 500% or more. Furthermore, in order to realize high bending resistance and twisting resistance, it is desirably formed so as to be thicker (for example, twice or more thicker) than the first insulator 31b and the second insulator 41b described later. The thickness of the signal line insulator 21b is, for example, 0.4 mm or more and 0.6 mm or less. Moreover, the outer diameter of the signal line 21 is larger than the outer diameter of the first power line 31 and the second power line 41 (for example, 1.3 times that of the first power line 31). The outer diameter of the signal line 21 is, for example, 2.0 mm or more and 2.4 mm or less.

[0015] A differential signal is transmitted through a pair of signal lines 21 constituting the twisted pair wire 2. This makes it less susceptible to external noise and enables stable signal transmission over a long distance, for example, 100 m. The characteristic impedance of the twisted pair wire 2 is, for example, 80Ω to 100Ω in the TDR method.

[0016] The first power line 31 constituting the first power line unit 3 has a first conductor 31a and a first insulator 31b covering the periphery of the first conductor 31a. The first conductor 31a is made of a stranded conductor formed by bundling a plurality of metal strands. As the metal strands used for the first conductor 31a, a tin-plated soft copper wire having an outer diameter of 0.8 mm or less can be used. The number of metal strands used for the first conductor 31a is preferably 100 or more. As the first insulator 31b, ETFE (tetrafluoroethylene-ethylene copolymer) that can withstand high voltage is used. Since the first insulator 31b is made of ETFE, it can be made thinner than the signal line insulator 21b of the signal line 21. Since the first insulator 31b is thinner, it can be made smaller in outer diameter than the signal line 21. Then, by making the outer diameter of the first power wire 31 smaller than that of the signal wire 21, the number of first power wires 31 can be made greater than the number of twisted pairs 2, and the rigidity of the first power wire unit 3 can be easily adjusted to be between 1 and 1.5 times the rigidity of the twisted pairs 2. That is, it becomes easier to adjust the rigidity balance of the composite cable 1 in the cable circumferential direction. The thickness of the first insulator 31b is, for example, 0.2 mm or more. The outer diameter of the first power wire 31 is, for example, 1.5 mm or more.

[0017] In this embodiment, the first power line unit 3 is disposed facing the twisted pair 2 in the cable diameter direction. The number of first power lines 31 constituting the first power line unit 3 is preferably greater than the number of signal lines 21 constituting the twisted pair 2. More specifically, the number of first power lines 31 is greater than one and less than four times the number of signal lines 21 (i.e., in the case of a twisted pair 2 in which a pair of signal lines 21 are twisted, the number is 3 to 8). In this embodiment, the first power line unit 3 is configured by arranging three first power lines 31 along the cable circumferential direction. The first power lines 31 adjacent to each other in the circumferential direction are in contact with each other. The three first power lines 31 are all configured to have the same outer diameter, material, etc.

[0018] The second power line 41 constituting the second power line unit 4 has a second conductor 41a and a second insulator 41b covering the periphery of the second conductor 41a. The second conductor 41a is made of a stranded conductor formed by bundling a plurality of metal strands. As the metal strands used for the second conductor 41a, a tin-plated soft copper wire having an outer diameter of 0.8 mm or less can be used. The number of metal strands used for the second conductor 41a is preferably 100 or more. As the second insulator 41b, ETFE (tetrafluoroethylene-ethylene copolymer) that can withstand high voltage is used. The tensile strength of the second insulator 41b is greater than the tensile strength of the signal line insulator 21b (here, the tensile strength of foamed polyethylene). The thickness of the second insulator 41b is, for example, 0.2 mm or more. Also, the outer diameter of the second power line 41 is, for example, 1.5 mm or more.

[0019] In this embodiment, the second power line unit 4 is configured by arranging an even number of second power wires 41 in opposition to each other at each position between the twisted pair wires 2 and the first power line unit 3 in the circumferential direction of the cable. In other words, the second power line unit 4 is configured by arranging the second power wires 41 so as to be plane-symmetrical with respect to a symmetry plane S that passes through the center of the cable and is along the opposing direction of the twisted pair wires 2 and the first power line unit 3 (however, some deviation due to manufacturing tolerances and the like is allowed). In order to be plane-symmetrical with respect to the symmetry plane S, the number of second power wires 41 is set to an even number.

[0020] In this embodiment, one second power wire 41 is disposed between each of the twisted pair wires 2 and the first power line unit 3 in the circumferential direction, and two second power wires 41 are used in total. The second power wire 41 is disposed so as to contact the twisted pair wires 2 and the first power line unit 31, respectively. The number of second power wires 41 constituting the second power line unit 4 is not limited to this, and for example, two second power wires 41 may be disposed between each of the twisted pair wires 2 and the first power line unit 3 in the circumferential direction, for a total of four second power wires 41. Here, the outer diameters of the first power wire 31 and the second power wire 41 are equal, but the outer diameters of the first power wire 31 and the second power wire 41 may be different. Also, here, all the second power wires 41 constituting the second power line unit 4 have the same configuration, but second power wires 41 with different configurations may be included. However, the second power wires 41 need to be disposed so as to be plane-symmetrical with respect to the symmetry plane S.

[0021] Thus, in this embodiment, the conductor configuration (composite twisted wire) of the signal wire 21 constituting the twisted pair wire 2 is different from the conductor configuration (collected twisted wire) of the first and second power line units 3 and 4. The outer diameter D1 of the twisted pair wire 2 is larger than the outer diameter of the first power line 31 and the outer diameter of the second power line 41. Furthermore, the outer diameter D1 of the twisted pair wire 2 is equal to or smaller than the length D2 of the entire first power line unit 3 in the direction perpendicular to the symmetry plane S (the opposing direction of the second power line 41, the left-right direction in FIG. 1). It is preferable that the first power line unit 3 opposing the twisted pair wire 2 is also arranged symmetrically with respect to the symmetry plane S. By setting the outer diameter D1 of the twisted pair wire 2 equal to or smaller than the length D2 of the entire first power line unit 3, it becomes easier to adjust the balance of rigidity in the cable circumferential direction of the composite cable 1 within a range in which the rigidity of the first power line unit 3 is 1 to 1.5 times the rigidity of the twisted pair wire 2.

[0022] In this embodiment, the assembly 5 is formed by twisting together the twisted pair wires 2, the first power line unit 3 consisting of three first power lines 31, the second power line unit 4 consisting of two second power lines 41, and the interposer 6. The interposer 6 serves to make the cable outer shape closer to a circular shape, and is made of a filament such as staple fiber yarn. Since the assembly 5 is formed by twisting the twisted pair wires 2 and the power lines 31, 41, the above-mentioned symmetry plane S becomes a plane that rotates according to the twisting of the assembly 5 as it moves in the longitudinal direction. In addition, the interposer 6 is preferably arranged between the twisted pair wires 2 and the first power line unit 3 so that the twisted pair wires 2 and the first power line unit 3 arranged opposite to each other in the cable diameter direction are separated from each other. By separating the twisted pair 2 and the first power line unit 3 in this manner, the rigidity of the composite cable 1 is well balanced, the arrangement of the twisted pair 2 and the first power line unit 3 is less likely to be disrupted by bending or twisting, and localized stress concentrations are less likely to occur.

[0023] A pressing and wrapping tape 7 is spirally wrapped around the assembly 5. As the pressing and wrapping tape 7, a tape-like member made of resin such as PTFE (polytetrafluoroethylene), nonwoven fabric, paper, or the like can be used.

[0024] A shield layer 8 is provided around the holding winding tape 7. A braided shield made of metal wires can be used as the shield layer 8. As the metal wires, it is more preferable to use copper alloy wires that have high resistance to bending and twisting. Although soft copper wires can also be used as the metal wires, in this case, it is preferable to use thin wires with a diameter of 0.08 to 0.12 mm. In addition, a part of the metal wires may be replaced with copper foil paper in which copper foil is spirally wound around a filament.

[0025] A drain wire 10 is provided between the holding winding tape 7 and the shield layer 8. The drain wire 10 serves to improve terminal processability by making slits in the shield layer 8 and the sheath 9 during terminal processing. For example, a annealed copper wire can be used as the drain wire 10. The annealed copper wire may have a tin plating on its surface.

[0026] The sheath 9 is for protecting the assembly 5 and the shield layer 8, and may be made of, for example, a PVC (polyvinyl chloride) resin composition or a urethane resin composition having excellent oil resistance. The thickness of the sheath 9 is, for example, 0.6 mm or more and 0.8 mm or less. The outer diameter of the sheath 9 (i.e., the outer diameter of the composite cable 1) is, for example, 9.0 mm or less. From the viewpoint of ease of routing, the outer diameter of the sheath 9 is preferably 8.6 mm or less.

[0027] Here, we consider the bending resistance and twisting resistance of the composite cable 1. In the composite cable 1, the signal wires 21 are twisted together to form the twisted pair wire 2 so that the composite cable 1 can be applied to long-distance transmission. Therefore, in the composite cable 1, the assembly 5 includes the twisted pair wire 2, and the first power line unit 3 opposing the twisted pair wire 2 is not twisted. In other words, in the composite cable 1, sufficient symmetry is not obtained in the opposing direction between the twisted pair wire 2 and the first power line unit 3. Therefore, when bending or twisting, stress may concentrate on the twisted pair wire 2 or the first power line 31, and sufficient resistance to bending and twisting may not be obtained. For example, if the rigidity of the twisted pair wire 2 is much higher than the rigidity of the first power line unit 3, stress may concentrate on the first power line 3 when bending or twisting, causing the first power line 3 to break early.

[0028] For example, it is possible to improve the symmetry of the composite cable 1 by twisting the first power line unit 3 arranged opposite the twisted pair 2, and to apply stress during bending, etc., approximately evenly to the twisted pair 2 and the first power line unit 3. In this case, however, the outer diameter of the composite cable 1 becomes large, and this large diameter may ultimately result in a decrease in bending resistance and twisting resistance.

[0029] Therefore, in this embodiment, the rigidity of the first power line unit 3 is set to be 1 to 1.5 times the rigidity of the twisted pair wire 2. This allows the rigidity of the twisted pair wire 2 and the first power line unit 3 to be balanced in the opposing direction, and stress during bending, etc., can be applied approximately evenly to the twisted pair wire 2 and the first power line unit 3, making it possible to improve bending resistance and twisting resistance without increasing the outer diameter of the composite cable 1. The rigidity balance in the direction perpendicular to the symmetry plane S is ensured by arranging the second power line 41 symmetrically with respect to the symmetry plane S.

[0030] Here, the rigidity of the twisted pair wire 2 is found by adding up the rigidities of the pair of signal wires 21 constituting the twisted pair wire 2, which are expressed by the following formula (1). (rigidity of signal line 21)=(conductor cross-sectional area of ​​signal line conductor 21a)×(tensile strength of signal line conductor 21a)+(cross-sectional area of ​​signal line insulator 21b)×(tensile strength of signal line insulator 21b) (1) For example, when soft copper wires are used as the metal wires of the signal line conductor 21a, the tensile strength of the signal line conductor 21a is, for example, about 220 MPa. When copper alloy wires are used as the metal wires of the signal line conductor 21a, the tensile strength of the signal line conductor 21a is, for example, about 850 MPa.

[0031] In addition, the rigidity of the first power line unit 3 is calculated by adding up the rigidities of each of the multiple first power lines 31 constituting the first power line 31, as expressed by the following formula (2). (rigidity of first power line 31)=(conductor cross-sectional area of ​​first conductor 31a)×(tensile strength of first conductor 31a)+(cross-sectional area of ​​first insulator 31b)×(tensile strength of first insulator 31b) (2)

[0032] As described above, in this embodiment, the rigidity of the first power line unit 3 is set to be equal to or greater than the rigidity of the twisted pair wire 2. This is because the first power line unit 3 is not twisted and the first power lines 31 can move freely relative to each other, and therefore the effect of the rigidity during bending, etc. may appear lower than the value obtained by adding up the rigidities of the first power lines 31 obtained by the above formula (2). The twisted pair wire 2 is twisted and the signal lines 21 cannot move freely relative to each other, and it is considered that the effect of the rigidity during bending, etc. is not reduced much. Therefore, in order to balance the effect of the actual rigidity during bending, etc., it is desirable to set the rigidity of the first power line unit 3 to be equal to or greater than the rigidity of the twisted pair wire 2 (1 to 1.5 times the rigidity of the twisted pair wire 2).

[0033] (Functions and Effects of the Embodiments) As described above, in the composite cable 1 of this embodiment, the twisted pair wire 2 and the first power line unit 3 are arranged opposite each other in the cable diameter direction, and the second power line unit 4 is configured by arranging an even number of second power wires 41 opposite each other between the twisted pair wire 2 and the first power line unit 3 in the cable circumferential direction, and the rigidity of the first power line unit 3 is set to be greater than or equal to 1 time and less than 1.5 times the rigidity of the twisted pair wire 2.

[0034] With this configuration, the composite cable 1 has a good balance of rigidity, and the arrangement of the twisted pair 2 and the power line units 3 and 4 is less likely to be distorted when repeatedly bent or twisted, and local stress concentration due to bending or twisting is less likely to occur. As a result, even if the first power line unit 3 is not twisted, the electric wires constituting the twisted pair 2 and the power line units 3 and 4 are less likely to break when repeatedly bent or twisted, and the bending resistance and twisting resistance can be improved while suppressing an increase in the diameter of the composite cable 1. In addition, in the composite cable 1, the signal wires 21 are twisted together and used as the twisted pair 2, so signal transmission over a long distance, for example, 100 m, can be stably performed, and a composite cable 1 suitable for signal transmission and power supply to servo motors of industrial robots used in factories, etc. can be realized.

[0035] (Summary of the embodiment) Next, the technical ideas grasped from the above-described embodiment will be described by using the reference numerals and the like in the embodiment. However, the reference numerals and the like in the following description do not limit the components in the claims to the members and the like specifically shown in the embodiment.

[0036] [1] A composite cable (1), comprising: a twisted wire in which a plurality of signal wires (21) are twisted together; a first power line unit (3) formed by arranging a plurality of first power wires (31) adjacent to each other in a circumferential direction of the cable; a second power line unit (4) having an even number of second power wires (41); and a sheath (9) that collectively covers the periphery of an assembly (5) in which the twisted wire, the plurality of first power wires (31) and the plurality of second power wires (41) are twisted together, wherein the twisted wire and the first power line unit (3) are arranged opposite each other in a diameter direction of the cable, and the second power line unit (4) is configured such that an equal number of the even number of second power wires (41) are arranged opposite each other between the twisted wire and the first power line unit (3) in the circumferential direction of the cable, and the rigidity of the first power line unit (3) is 1 to 1.5 times the rigidity of the twisted wire.

[0037] [2] The twisted wire is composed of a pair of the signal wires (21) twisted together to form a twisted pair wire (2), the signal wire (21) having a signal line conductor (21a) and a signal line insulator (21b) covering the periphery of the signal line conductor (21a), the first power supply wire (31) having a first conductor (31a) and a first insulator (31b) covering the periphery of the first conductor (31a), and the rigidity of the twisted pair wire (2) is calculated by adding up the rigidities of the signal wires (21) of the pair of signal wires (21) constituting the twisted pair wire (2) as expressed by the following formula: (Rigidity of signal line (21))=(conductor cross-sectional area of ​​signal line conductor (21a))×(tensile strength of signal line conductor (21a))+(cross-sectional area of ​​signal line insulator (21b))×(tensile strength of signal line insulator (21b)). The rigidity of the first power supply line unit (3) is calculated by adding up the rigidities of the first power supply lines (31) constituting the first power supply line unit (3) and expressed by the following formula: The composite cable (1) described in [1], (rigidity of first power supply line (31)) = (conductor cross-sectional area of ​​first conductor (31a)) × (tensile strength of first conductor (31a)) + (cross-sectional area of ​​first insulator (31b)) × (tensile strength of first insulator (31b)).

[0038] [3] The composite cable (1) described in [1] or [2], wherein the first power supply line unit (3) is configured by arranging three to eight of the first power supply wires (31) along the circumferential direction of the cable.

[0039] [4] The composite cable (1) according to any one of [1] to [3], wherein an outer diameter (D1) of the twisted pair wire (2) is equal to or less than a length (D2) of the entire first power line unit (3) in the opposing direction of the second power line.

[0040] [5] The composite cable (1) according to any one of [1] to [4], wherein an outer diameter of the twisted pair wire (2) is larger than an outer diameter of the first power wire (31) and an outer diameter of the second power wire (41).

[0041] Although the embodiments of the present invention have been described above, the invention according to the claims is not limited to the embodiments described above. It should be noted that not all of the combinations of features described in the embodiments are essential to the means for solving the problems of the invention. [Explanation of symbols]

[0042] 1...Composite cable 2...Twisted pair wire (twisted wire) 21...Signal line 21a...Signal line conductor 21b…Signal line insulator 3...First power line unit 31...1st power line 31a…First conductor 31b…First insulator 4...Second power line unit 41…Second power line 41a…Second conductor 41b...Second insulator 5…Aggregation 6…intervention 7…Press and wrap tape 8…Shield layer 9…Sheath 10…Drain wire

Claims

1. a twisted wire in which a plurality of signal wires are twisted together; a plurality of first power lines, the number of which is greater than the number of the plurality of signal lines; a sheath that collectively covers an assembly in which the stranded wire and the plurality of first power lines are twisted together; Equipped with the stranded wire is disposed opposite and spaced apart from the plurality of first power lines in a cable diameter direction, the first power supply wires are arranged in an arc shape along a circumferential direction of the cable from a position facing the twisted wire, an outer diameter of the stranded wire is larger than an outer diameter of each of the plurality of first power wires; Composite cable.

2. The twisted wire is arranged to pass through the center of the cable. The composite cable of claim 1 .

3. The power supply device includes a plurality of second power lines arranged between the plurality of first power lines and the twisted wire.

3. The composite cable according to claim 1 or 2.

4. When the plurality of signal lines are arranged in a diametrical direction of the cable, the stranded wire and the plurality of first power lines are not in contact with each other. A composite cable according to any one of claims 1 to 3.

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