Patent Grant
11049630
The present invention is based on Japanese Patent Application No. 2019-209310 filed on Nov. 20, 2019, the entire contents of which are incorporated herein by reference.
The present invention relates to a multicore cable.
In recent years, for a productivity enhancing measure, the market for collaborative robots or small articulated robots is expanding. As robot cables to be used in such a robot, a movable part cable designed to be wired in a movable part of that robot and a fixed part cable designed to connect that robot and a control device are used.
As the movable part cable, there is known a multicore cable, which is configured to include a bunched core composed of a plurality of electric wires laid together, a shielding layer composed of a braided shield and provided over a periphery of that bunched core, and a sheath provided over a periphery of that shielding layer. Such a multicore cable is used not only in a robot cable but also, for example, in an unsprung wiring in an automobile, or the like.
Note that Japanese Patent No. 6394721 has been disclosed as prior art document information relevant to the invention of the present application.
[Patent Document 1] Japanese Patent No. 6394721
In the above-described conventional multicore cable, when the multicore cable is repeatedly bent, between the braided shield being used in the shielding layer and respective constituent electrical insulating members of the plurality of electric wires constituting the bunched core, there occurs a lateral pressure friction, causing abrasion and subsequent local wearing away or the like of the electrical insulating members of the plurality of electric wires, leading to concern that a failure such as a deterioration in properties of the multicore cable, or a short circuit between respective constituent conductors of the plurality of electric wires constituting the bunched core and the shielding layer, or a wire break, or the like, may occur.
In view of the foregoing, it is an object of the present invention to provide a multicore cable that is designed to be resistant to the occurrence of a failure such as a wire break or the like when repeatedly bent.
For the purpose of solving the above-described problems, the present invention provides a multicore cable, comprising: a bunched core composed of a plurality of electric wires laid together, each including a conductor, and an electrical insulating member provided over a periphery of the conductor; an abrasion suppressing layer configured as a taping member helically wrapped around a periphery of the bunched core; a shielding layer composed of a braided shield provided over an outer periphery of the abrasion suppressing layer; and a sheath provided over a periphery of the shielding layer, wherein an opposite surface of the taping member of the abrasion suppressing layer to the bunched core and an opposite surface of the taping member of the abrasion suppressing layer to the shielding layer are composed of a fluoropolymer resin, with the taping member of the abrasion suppressing layer being non-adhesively lap wound in such a manner as to partially overlap itself in a width direction of that taping member.
Points of the Invention
According to the present invention, it is possible to provide the multicore cable that is designed to be resistant to the occurrence of a failure such as a wire break or the like when repeatedly bent.
[Embodiment]
An embodiment of the present invention will be described below in conjunction with the accompanying drawings.
As shown in
(Electric Wires 2)
The conductors 21 of the plurality of electric wires 2 are made of a composite stranded wire produced by using a plurality of child stranded wires each composed of a plurality of metal wires made of a copper or the like stranded together, and further stranding the plurality of child stranded wires together. The plurality of child stranded wires are each produced by bunched stranding of the plurality of metal wires together, and the conductors 21 of the plurality of electric wires 2 are each produced by concentric stranding of the plurality of child stranded wires together. By configuring the conductors 21 of the plurality of electric wires 2 by the composite stranding, the multicore cable 1 is made high in flexibility to thereby be able to facilitate the wiring of the multicore cable 1, and in addition, even when the multicore cable 1 is subjected to repeated bendings or torsions in a movable part, the multicore cable 1 becomes resistant to the occurrence of a wire break in the metal wires constituting the conductors 21 of the plurality of electric wires 2, and so the multicore cable 1 is enhanced in bending resistance and torsion resistance. In addition, by making the conductors 21 of the plurality of electric wires 2 from the above-described composite stranded wire, the conductors 21 of the plurality of electric wires 2 are effectively made resistant to the occurrence of a wire break or the like even when the multicore cable 1 is acted on by such a load as to jerk the multicore cable 1.
In order to sufficiently impart the bending resistance and the torsion resistance to the multicore cable 1, as the metal wires to be used in the conductors 21 of the plurality of electric wires 2, the metal wires having a tensile strength of not lower than 220 MPa and an elongation of not lower than 5% may be used. Further, in order to keep the attenuation in a long distance transmission small, the conductor cross-sectional areas of the conductors 21 of the plurality of electric wires 2 may be not smaller than 0.75 mm2. In the present embodiment, each of the conductors 21 of the three electric wires 2 can be constituted by the use of, for example, tin-plated soft copper wires having a wire diameter of 0.08 mm as the metal wires to be used in the conductors 21 of the three electric wires 2, and by the concentric stranding together of seven of the child stranded wires each composed of thirty of those tin-plated soft copper wires. At this point of time, the outer diameters of the conductors 21 of the three electric wires 2 are about 1.41 mm, and the conductor cross-sectional areas of the conductors 21 of the three electric wires 2 are about 1.04 mm2.
The electrical insulating members 22 of the plurality of electric wires 2 are formed in such a manner as to coat the peripheries of the conductors 21 of the plurality of electric wires 2 respectively. As the electrical insulating members 22 of the plurality of electric wires 2, it is possible to use, for example, the electrical insulating members having a single layer structure made of a PVC (polyvinyl chloride), a PE (polyethylene), an ETFE (tetrafluoroethylene-ethylene copolymer), an FEP (tetrafluoroethylene-hexafluoropropylene copolymer), or the like. Alternatively, as the electrical insulating members 22 of the plurality of electric wires 2, it is possible to use, for example, the electrical insulating members having a two-layer structure whose inner layer is made of a PVC (polyvinyl chloride) and whose outer layer is made of an ETFE (tetrafluoroethylene-ethylene copolymer), or a two-layer structure whose inner layer is made of a foamed polyethylene and whose outer layer is made of a non-foamed polyethylene.
Note that, when the transmission properties of a high frequency signal are enhanced (more specifically, for example, when a high frequency signal in a band of 10 MHz to 6 GHz is made resistant to being attenuated in a long distance transmission thereof), as the electrical insulating members 22 of the plurality of electric wires 2, it is desirable to use the electrical insulating members having as low a dielectric constant as possible. For example, as the electrical insulating members 22 of the plurality of electric wires 2, it is possible to use the electrical insulating members having a three-layer structure configured to include a non-solid extruded layer, which is provided on the outer peripheries of the conductors 21 of the plurality of electric wires 2 by tube extrusion using a non-foamed resin material having a low dielectric constant, a foamed layer, which is non-adhesively provided on the outer periphery of that non-solid extruded layer, and a non-foamed layer, which is adhesively provided on the outer periphery of that foamed layer. For the non-solid extruded layer, it is possible to use, for example, a fluoropolymer resin material made of an FEP (tetrafluoroethylene-hexafluoropropylene copolymer), a PFA (tetrafluoroethylene-perfluoroalkylvinyl ether copolymer), or the like. Further, for the foamed layer, a resin material having a lower melting point than that of the fluoropolymer resin material used in the non-solid extrusion layer may be used. For example, for the foamed layer, it is possible to use the resin material made of an irradiation crosslinked foamed polyethylene, or a foamed polypropylene, or the like. Further, the non-foamed layer may be made of the same resin material as that of the foamed layer. For example, for the non-foamed layer, it is possible to use the resin material made of a non-foamed polypropylene, or an irradiation crosslinked polyethylene, or the like.
(Bunched Core 3)
The bunched core 3 is constituted by laying the three electric wires 2 together. It should be noted, however, that the number of the electric wires 2 constituting the bunched core 3 is not limited to the above number. Further, although in the present embodiment, all of the plurality of electric wires 2 constituting the bunched core 3 have the same configurations, the configurations of the plurality of electric wires 2 are not limited to the foregoing, but, for example, it is possible to use the plurality of electric wires 2 being different from each other in the outer diameter or in the conductor cross-sectional area. Further, in order to make the outer shape of the multicore cable 1 close to a circular shape, the bunched core 3 may be configured in such a manner that a filling member is laid along with the plurality of electric wires 2. As the filling member, it is possible to use, for example, a thread-like shape body such as a staple fiber yarn or the like, or a linear shape body made of a polyethylene or the like.
(Abrasion Suppressing Layer 4)
The abrasion suppressing layer 4 is configured as a taping member 41 made of a fluoropolymer resin tape helically wrapped around a periphery of the bunched core 3. For example, providing the abrasion suppressing layer 4 by extrusion molding is also considered, but, in this case, the abrasion suppressing layer 4 is formed in a cylindrical shape, so the abrasion suppressing layer 4 becomes very hard and difficult to bend, leading to a lowering in the flexibility of the multicore cable 1. That is, in the present embodiment, in order to suppress the occurrence of a lowering in the flexibility of the multicore cable 1, and in order to, when repeatedly bending the multicore cable 1, suppress the occurrence of an abrasion in the electrical insulating members 22 of the plurality of electric wires 2 resulting from a lateral pressure abrasion caused between the shielding layer 5, which is composed of a plurality of metal wires, and those electrical insulating members 22 made of the electrically insulative resin material, the abrasion suppressing layer 4 is formed by helically wrapping the taping member 41 made of a fluoropolymer resin tape around the periphery of the bunched core 3. Note that, as shown in
As shown in
Further, it is desirable that the fluoropolymer resin tape to constitute the taping member 41 of the abrasion suppressing layer 4 includes two non-adhesive surfaces that are not adhered to the electrical insulating members 22 of the plurality of electric wires 2 constituting the bunched core 3, and to the shielding layer 5. Note that the “taping member made of a fluoropolymer resin tape” described herein refers to the taping member configured with a tape uniformly formed of a fluoropolymer resin. In addition, in order to achieve the above-described actions and advantageous effects of the taping member 41, it is desirable that the taping member 41 is lap wound around the outer periphery of the bunched core 3 in such a manner that the widths of the overlapped portions of the fluoropolymer resin tape to form the taping member 41 are not less than 0.3 times and not more than 0.5 times the width (for example, 15 mm to 35 mm) of that fluoropolymer resin tape.
When the multicore cable 1 is repeatedly bent (especially when the multicore cable 1 is acted on by such a load as to jerk the multicore cable 1), the multicore cable 1 is acted on by a lateral pressure, but, in the multicore cable 1 according to the present embodiment, since the above-described abrasion suppressing layer 4 is provided between the electrical insulating members 22 of the plurality of electric wires 2 constituting the bunched core 3 and the shielding layer 5, it is possible to suppress the occurrence of an abrasion in the electrical insulating members 22 of the plurality of electric wires 2 resulting from the electrical insulating members 22 of the plurality of electric wires 2 and the shielding layer 5 being rubbed against each other due to the lateral pressure. That is, by providing the abrasion suppressing layer 4 between the electrical insulating members 22 of the plurality of electric wires 2 constituting the bunched core 3 and the shielding layer 5, since the first surface of the abrasion suppressing layer 4 being brought into contact with the electrical insulating members 22 of the plurality of electric wires 2 and the second surface of the abrasion suppressing layer 4 being brought into contact with the shielding layer 5 are resistant to being abraded by the lateral pressure, it is possible to enhance the durability of the multicore cable 1 against being repeatedly bent, particularly the durability of the multicore cable 1 against being acted on by such a load as to jerk the multicore cable 1 (hereinafter, referred to as simply the durability of the multicore cable 1 against being jerked).
It is desired that, when the multicore cable 1 is bent or swung, or when the multicore cable 1 is moved in such a manner as to be jerked, in order for the shielding layer 5 to be able to move in such a manner as to slide relative to the abrasion suppressing layer 4, the two surfaces of the abrasion suppressing layer 4 are slippery (the coefficients of a friction on the two surfaces of the abrasion suppressing layer 4 are lower than the coefficients of the friction on the surfaces of the electrical insulating members 22 of the plurality of electric wires 2). Examples of the fluoropolymer resin tape to be used in the taping member 41 of the abrasion suppressing layer 4 include an ETFE (tetrafluoroethylene-ethylene copolymer) tape, a PTFE (polytetrafluoroethylene) tape, and the like. In the present embodiment, the taping member 41 of the abrasion suppressing layer 4 being made of the PTFE having not only a slippery surface but also a low dielectric constant is used.
The thickness of the taping member 41 of the abrasion suppressing layer 4 is preferably not less than 25 μm and not more than 150 μm. This is because, when the thickness of the taping member 41 of the abrasion suppressing layer 4 is not less than 25 μm, the taping member 41 becomes resistant to being fractured by being repeatedly abraded, or when the thickness of the taping member 41 of the abrasion suppressing layer 4 is not more than 150 μm, the abrasion suppressing layer 4 has such a hardness as to allow the multicore cable 1 to become resistant to being lowered in flexibility. In the present embodiment, for example, the taping member 41 made of the PTFE tape having a thickness of 100 μm can be used.
Although in the present embodiment, as shown in
(Shielding Layer 5)
The shielding layer 5 is the one designed for external noise shielding. In order to ensure the flexibility of the multicore cable 1, the shielding layer 5 being provided over the outer periphery of the abrasion suppressing layer 4 is composed of a braided shield with metal wires being braided together therein. In the present embodiment, the shielding layer 5 is constituted by laminating a plurality of layers of the braided shields on top of each other. Herein, a case in which the shielding layer 5 is constituted by laminating two layers of the braided shields on top of each other will be described, but the shielding layer 5 may be constituted by laminating three or more layers of the braided shields on top of each other. Hereinafter, a first one of the two layers of the braided shields, which is provided in an inner side of the shielding layer 5 in radial directions of the multicore cable 1, will be referred to as the inner braided shield 51, while a second one of the two layers of the braided shields, which is provided in an outer side of the shielding layer 5 in the radial directions of the multicore cable 1, will be referred to as the outer braided shield 52.
In the multicore cable 1 according to the present embodiment, an air layer 7 may be formed partially in the circumferential direction thereof between the shielding layer 5 (the inner braided shield 51 of the shielding layer 5) and the abrasion suppressing layer 4. In order to form the air layer 7, the inner diameter of the inner braided shield 51 may be configured in such a manner as to be larger than the outer diameter of the abrasion suppressing layer 4. In the present embodiment, the air layer 7 can be formed by, when forming the inner braided shield 51, arranging a rod-shaped spacer, which is built in, for example, a braid forming device, along the cable longitudinal direction of the multicore cable 1 on the outer periphery of the abrasion suppressing layer 4, braiding the metal wires together on that spacer to form the inner braided shield 51, and in turn sending the formed inner braided shields 51 out of the braid forming device in such a manner as to withdraw the formed inner braided shields 51 from the spacer. Note that, even when such a production method is not performed, micro gaps are formed in an uneven portion of the taping member 41 of the abrasion suppressing layer 4 (an uneven portion of the taping member 41 resulting from the partial overlapping of the taping member 41 in the width direction of the taping member 41) or between the metal wires of the inner braided shield 51 as well, but that such micro gaps are not included in the air layer 7 of the present invention. Further, the shape of the spacer is not limited to the above rod shape. The size of the air layer 7 refers to such a state that the shielding layer 5 is floating from the surface of the abrasion suppressing layer 4 to the sheath 6 side, within a range of the maximum distance from the surface of the abrasion suppressing layer 4 to the inner surface of the shielding layer 5 (the opposite surface of the shielding layer 5 to the surface of the abrasion suppressing layer 4) of not less than 5 μm and not more than 30 μm. The maximum distance is determined by measuring the maximum value of the distance in a straight line from the surface of the abrasion suppressing layer 4 to the inner surface of the shielding layer 5, when cutting the multicore cable 1 at a predetermined position thereon and subsequently observing the cable transverse cross section (the cable cross section perpendicular to the cable longitudinal direction of the multicore cable 1) of the cut portion of the multicore cable 1 using an optical microscope or an electron microscope.
By forming the air layer 7 between the shielding layer 5 (the inner braided shield 51 of the shielding layer 5) and the abrasion suppressing layer 4, the tightening of the abrasion suppressing layer 4 caused by the shielding layer 5 is suppressed, and so when the multicore cable 1 is bent, swung or jerked, the shielding layer 5 (the inner braided shield 51 of the shielding layer 5) and the abrasion suppressing layer 4 can easily be moved relative to each other in the longitudinal direction of the multicore cable 1, and the bending resistance of the multicore cable 1, the torsion resistance of the multicore cable 1, and the durability of the multicore cable 1 against being jerked can be enhanced.
The outer braided shield 52 of the shielding layer 5 is formed by braiding the metal wires together on the outer periphery of the inner braided shield 51 of the shielding layer 5, in the same manner as in a typical braided shield producing method. This is because, if an air layer is formed between the inner braided shield 51 and the outer braided shield 52 constituting the shielding layer 5, the contact resistance therebetween within the shielding layer 5 becomes high, leading to concern that a deterioration in the properties of the multicore cable 1 may occur.
In order to sufficiently impart the bending resistance and the torsion resistance to the multicore cable 1, the metal wires to be used in both the inner braided shield 51 and the outer braided shield 52 constituting the shielding layer 5 have a tensile strength of not lower than 340 MPa and an elongation of not lower than 5%. In the present embodiment, for example, as the metal wires to be used in both the inner braided shield 51 and the outer braided shield 52 constituting the shielding layer 5, the metal wires made of a tin-plated copper alloy having a wire diameter of 0.08 mm can be used. Further, the densities of both the inner braided shield 51 and the outer braided shield 52 are set at about 90%. Note that the metal wires to be used in both the inner braided shield 51 and the outer braided shield 52 may be of the same or different wire diameters.
In addition, in the present embodiment, the metal wires coated with a lubricant agent can be used in both the inner braided shield 51 and the outer braided shield 52 constituting the shielding layer 5. As the lubricant agent, for example, a liquid paraffin can be used. This allows the shielding layer 5 and the abrasion suppressing layer 4 to be more easily slid relative to each other, and so the bending resistance of the multicore cable 1, the torsion resistance of the multicore cable 1, and the durability of the multicore cable 1 against being jerked can be further enhanced.
Now, as shown in
(Sheath 6)
The sheath 6 is formed in such a manner as to cover the periphery of the shielding layer 5. As the sheath 6, for example, the sheath made of a PVC (polyvinyl chloride) or a urethane can be used. In the present embodiment, the sheath 6 made of the PVC is used. The sheath 6 is desirably formed by tube extrusion so that the shielding layer 5 can be moved within the sheath 6.
(Actions and Advantageous Effects of the Embodiment)
As described above, and shown in
(Modification)
Although in the above embodiment, all of the plurality of electric wires 2 constituting the bunched core 3 have the same configurations, the configurations of the plurality of electric wires 2 constituting the bunched core 3 may not be the same, so the specific configuration of the bunched core 3 is not particularly limited. For example, as in a multicore cable la shown in
The two power supply wires 2a and 2a are each being configured in such a manner that a constituent conductor 21a of each of those two power supply wires 2a and 2a is coated with a constituent electrical insulating member 22a of each of those two power supply wires 2a and 2a therearound, while the two signal wires 2b and 2b are each being configured in such a manner that a constituent conductor 21b of each of those two signal wires 2b and 2b is coated with a constituent electrical insulating member 22b of each of those two signal wires 2b and 2b therearound. The conductor sectional areas of the conductors 21a of the two power supply wires 2a and 2a are larger than the conductor sectional areas of the conductors 21b of the two signal wires 2b and 2b. Further, the outer diameters of the two power supply wires 2a and 2a are larger than the outer diameters of the two signal wires 2b and 2b.
Next, the technical ideas grasped from the above-described embodiments will be described with the aid of the reference characters and the like in the embodiments. It should be noted, however, that each of the reference characters and the like in the following descriptions is not to be construed as limiting the elements in the claims to the members and the like specifically shown in the embodiments.
[1] A multicore cable (1), comprising: a bunched core (3) composed of a plurality of electric wires (2) laid together, each including a conductor (21), and a electrical insulating member (22) provided over a periphery of the conductor (21); an abrasion suppressing layer (4) configured as a taping member (41) helically wrapped around a periphery of the bunched core (3); a shielding layer (5) composed of a braided shield provided over an outer periphery of the abrasion suppressing layer (4); and a sheath (6) provided over a periphery of the shielding layer (5), wherein an opposite surface of the taping member (41) of the abrasion suppressing layer (4) to the bunched core (3) and an opposite surface of the taping member (41) of the abrasion suppressing layer (4) to the shielding layer (5) are composed of a fluoropolymer resin, with the taping member (41) of the abrasion suppressing layer (4) being non-adhesively lap wound in such a manner as to partially overlap itself in a width direction of that taping member (41).
[2] The multicore cable (1) according to [1] above, wherein a wrapping direction of the taping member (41) of the abrasion suppressing layer (4) is the same as a lay direction of the bunched core (3).
[3] The multicore cable (1) according to [1] or [2] above, wherein a coefficient of a friction on the opposite surface of the taping member (41) of the abrasion suppressing layer (4) to the bunched core (3) and a coefficient of the friction on the opposite surface of the taping member (41) of the abrasion suppressing layer (4) to the shielding layer (5) are lower than coefficients of the friction on surfaces of the electrical insulating members (22) of the plurality of electric wires (2) constituting the bunched core (3).
[4] The multicore cable (1) according to any one of [1] to [3] above, wherein at least one of the plurality of electric wires (2) constituting the bunched core (3) is configured in such a manner that the conductor (21) thereof can be moved independently of the electrical insulating member (22) thereof.
[5] The multicore cable (1) according to any one of [1] to [4] above, further comprising an air layer formed partially in a circumferential direction thereof between the shielding layer (5) and the abrasion suppressing layer (4).
[6] The multicore cable (1) according to any one of [1] to [5] above, wherein the shielding layer (5) is composed of a plurality of layers of the braided shields laminated on top of each other in radial directions of the multicore cable (1), with a braiding angle of an innermost one (51) of the plurality of layers of the braided shields, which is provided in an innermost side of the shielding layer (5) in the radial directions of the multicore cable (1), being smaller than braiding angles of outer ones (52) of the plurality of layers of the braided shields, which are provided in an outer side of the shielding layer (5) relative to that innermost one (51) of the plurality of layers of the braided shields in the radial directions of the multicore cable (1).
[7] The multicore cable (1) according to any one of [1] to [6] above, wherein the shielding layer (5) is composed of a braided shield with metal wires braided together therein comprising a tensile strength of not lower than 340 MPa and an elongation of not lower than 5%.
[8] The multicore cable (1) according to [7] above, wherein the metal wires to be used in the shielding layer (5) are made of a tin-plated copper alloy.
[9] The multicore cable (1) according to [7] or [8] above, wherein the metal wires to be used in the shielding layer (5) are coated with a lubricant agent thereon.
[10] The multicore cable (1) according to any one of [1] to [9] above, wherein at least one of the plurality of electric wires (2) constituting the bunched core (3) comprises a conductor cross-sectional area of the conductor (21) thereof of not smaller than 0.75 mm2.
[11] The multicore cable (1) according to any one of [1] to [10] above, wherein the conductor (21) of at least one of the plurality of electric wires (2) constituting the bunched core (3) is made of a composite stranded wire produced by using a plurality of child stranded wires each composed of a plurality of metal wires stranded together, and further stranding the plurality of child stranded wires together.
Although the embodiments of the present invention have been described above, the above described embodiments are not to be construed as limiting the inventions according to the appended claims. Further, it should be noted that not all the combinations of the features described in the embodiments are indispensable to the means for solving the problem of the invention.
The present invention can be appropriately modified and implemented without departing from the spirit thereof.
Although the invention has been described with respect to the specific embodiments for complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art which fairly fall within the basic teaching herein set forth.
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