JP7632571B2 - Composite Cable - Google Patents

Description

The present invention relates to a composite cable.

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 are twisted together to form a twisted pair wire and multiple power lines are twisted together to form a cable core. The composite cable of Patent Document 1 is used, for example, as wiring for vehicles such as automobiles.

JP 2020-47599 A

Incidentally, 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. Connecting multiple cables to small servo motors is difficult, and the wiring space for cables in industrial robots tends to be narrow. Therefore, 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, rather than using separate cables for power supply and signal transmission.

Therefore, the present invention aims to provide a composite cable that combines a signal line and a power line into a single cable.

The present invention aims to solve the above problems by providing a composite cable comprising a twisted wire in which multiple signal wires are twisted together, a first power line unit in which multiple first power lines are arranged adjacent to each other in the circumferential direction of the cable, a second power line unit having an even number of second power lines, and a sheath that collectively covers the periphery of an assembly in which the twisted wire, the multiple first power lines, and the multiple second power lines are twisted together, the twisted wire and the first power line unit being arranged opposite each other in the diametrical direction of the cable, and the second power line unit being configured such that an equal number of the even number of second power lines 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 1 to 1.5 times the rigidity of the twisted wire.

The present invention provides a composite cable that combines a signal line and a power line into a single cable.

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.

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

Figure 1 is a cross-sectional view showing a cross section perpendicular to the longitudinal direction of the composite cable according to this 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 used, for example, to be connected to a servo motor of an industrial robot and 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 and supplying such signals and currents between the servo motor and the moving part of the industrial robot, the moving 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.

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 transmissions, 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 transmissions. For example, it is possible to increase the outer diameter of the composite cable to accommodate long-distance transmissions, but in this case, the bending resistance and twisting resistance will decrease. Therefore, composite cables are required to enable long-distance transmissions without increasing the outer diameter of the composite cable (for example, with an outer diameter of the composite cable of 9.0 mm or less), and to have excellent bending resistance and twisting resistance.

As shown in FIG. 1, the composite cable 1 includes a twisted pair 2 in which a pair of signal wires 21 are twisted together as a twisted wire in which a plurality of signal wires 21 are twisted together, a first power line unit 3 in which a plurality of first power wires 31 are arranged 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 in which the twisted pair 2, the plurality of first power wires 31, and the plurality of second power wires 41 are twisted together. Note that in the composite cable 1 shown in FIG. 1, the twisted pair 2 in which a pair of signal wires 21 are twisted together is used as the twisted wire, but this is not limited to this. The twisted wire may be, for example, a twisted pair of two or more signal wires 21, or a twisted pair of twisted pair wires 2 in which a pair of signal wires 21 are twisted together.

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 be subjected to 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 for the signal line conductor 21a, a tin-plated soft copper wire with an outer diameter of 0.8 mm or less can be used. It is preferable that the number of metal wires used for the signal line conductor 21a is 100 or more and is less than the number of metal wires used for the first conductor 31a and the second conductor 41a. By using such a signal line conductor 21a, it is effective in improving the balance of rigidity of the composite cable 1 and improving bending resistance and twisting resistance.

In order to realize good electrical characteristics that enable long-distance transmission, it is desirable to use a signal line insulator 21b with 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 that the signal line insulator 21b is thicker (for example, twice as thick) 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. In addition, 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.

A differential signal is transmitted through the pair of signal lines 21 that make up the twisted pair wire 2. This makes it less susceptible to the effects of external noise, and enables stable signal transmission over long distances, such as 100 m. The characteristic impedance of the twisted pair wire 2 is, for example, 80 Ω to 100 Ω in the TDR method.

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 should be 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 is possible to make the thickness thinner than the signal line insulator 21b of the signal line 21. Since the thickness of the first insulator 31b is thin, it is possible to make the outer diameter of the first power line 31 smaller than the outer diameter of the signal line 21. By making the outer diameter of the first power wire 31 smaller than the outer diameter of the signal wire 21, the number of first power wires 31 can be made greater than the number of twisted pair wires 2, and the rigidity of the first power wire unit 3 can be easily adjusted to between 1 and 1.5 times the rigidity of the twisted pair wires 2. In other words, it is easy 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.

In this embodiment, the first power line unit 3 is arranged opposite the twisted pair 2 in the cable diameter direction. In addition, 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 1 and less than 4 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. In addition, the three first power lines 31 are all configured to have the same outer diameter, material, etc.

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 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 should be 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. The outer diameter of the second power line 41 is, for example, 1.5 mm or more.

In this embodiment, the second power line unit 4 is configured by arranging an even number of second power lines 41 in opposing positions between the twisted pair 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 lines 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 2 and the first power line unit 3 (however, some deviation due to manufacturing tolerances, etc. is allowed). In order to be plane-symmetrical with respect to the symmetry plane S, the number of second power lines 41 is an even number.

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

In this manner, 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. In addition, 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 making 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.

In this embodiment, the assembly 5 is formed by twisting together the twisted pair wire 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 wire 2 and the power lines 31 and 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 may be arranged between the twisted pair wire 2 and the first power line unit 3 so that the twisted pair wire 2 and the first power line unit 3, which are arranged opposite 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 way, 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.

A pressure winding tape 7 is wound in a spiral shape around the assembly 5. The pressure winding tape 7 can be a tape-like material made of resin such as PTFE (polytetrafluoroethylene), nonwoven fabric, paper, etc.

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. It is more preferable to use copper alloy wires as the metal wires, which have high resistance to bending and twisting. Soft copper wires can also be used as the metal wires, but in this case it is preferable to use thin wires with a diameter of 0.08 to 0.12 mm. In addition, part of the metal wires may be replaced with copper foil paper, which is a filamentary body wrapped in copper foil in a spiral shape.

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 workability by making cuts in the shield layer 8 and the sheath 9 during terminal processing. For example, a soft copper wire can be used as the drain wire 10. The soft copper wire may have a tin plating on its surface.

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 that has 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, it is preferable that the outer diameter of the sheath 9 is 8.6 mm or less.

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 twisted pair wire 2 is included in the assembly 5, 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 be concentrated 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 be concentrated on the first power line 3 when bending or twisting, and the first power line 3 may be broken early.

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 distribute the stress during bending, etc., approximately evenly between the twisted pair 2 and the first power line unit 3. However, in this case, the outer diameter of the composite cable 1 becomes large, and this large diameter may result in a decrease in bending resistance and twisting resistance.

In this embodiment, the rigidity of the first power line unit 3 is set to 1 to 1.5 times the rigidity of the twisted pair wire 2. This balances the rigidity of the twisted pair wire 2 and the first power line unit 3 in the opposing direction, making it possible to load stress during bending, etc., approximately evenly on the twisted pair wire 2 and the first power line unit 3, thereby improving 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.

Here, the rigidity of the twisted pair wire 2 is found by adding up the rigidities of the 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 strands of the signal line conductor 21a, the tensile strength of the signal line conductor 21a is, for example, about 220 MPa, and when copper alloy wires are used as the metal strands of the signal line conductor 21a, the tensile strength of the signal line conductor 21a is, for example, about 850 MPa.

In addition, the rigidity of the first power line unit 3 is calculated by adding up the rigidity 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)

In this manner, 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, so the effect of the rigidity during bending, etc. may be lower than the sum of 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 less likely to decrease. 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).

(Functions and Effects of the Embodiments)
As described above, in the composite cable 1 according to this embodiment, the twisted pair wires 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 wires 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 wires 2.

This configuration provides a good balance of the rigidity of the composite cable 1, 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 localized 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 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 preventing the composite cable 1 from becoming larger in diameter. 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 long distances of, 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.

(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.

[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) in which a plurality of first power lines (31) are arranged adjacent to each other in the circumferential direction of the cable, a second power line unit (4) having an even number of second power lines (41), and a sheath (9) that collectively covers the periphery of an assembly (5) in which the twisted wire, the plurality of first power lines (31), and the plurality of second power lines (41) are twisted together, the twisted wire and the first power line unit (3) are arranged opposite each other in the cable diameter direction, the second power line unit (4) is configured such that an equal number of the even number of second power lines (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.

[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 determined 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:
(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)). The composite cable (1) described in [1].

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

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

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

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 necessarily essential to the means for solving the problems of the invention.

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... first power line 31a... first conductor 31b... first insulator 4... second power line unit 41... second power line 41a... second conductor 41b... second insulator 5... assembly 6... interposer 7... pressure wrapping tape 8... shielding layer 9... sheath 10... drain wire

Claims (4)

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. The stranded wire is arranged to pass through the center of the cable.
The composite cable of claim 1 . a plurality of second power supply wires disposed between the plurality of first power supply wires and the twisted wire ;
3. The composite cable according to claim 1 or 2. 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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