JPH037842Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a flat cable and aims to provide a flat cable that is highly flexible and has excellent repeated bending resistance.

A flat cable is a completely flat and thin cable in which a large number of conductors are enclosed in an insulating material parallel to each other at predetermined intervals, and is also called a tape wire, ribbon cable, flat cable, etc.

Generally, it is manufactured by sandwiching a group of conductors arranged in parallel between two sheets of insulating resin tape on a sanderch and joining them together using thermocompression bonding or adhesive. In addition, the conductors arranged in parallel are passed through the head of a resin extruder to insulate them as a whole. Conductors that have been individually insulated in advance are brought into contact with each other in parallel, and the coatings of adjacent conductors are bonded or fused together to integrate them as a whole. It can also be manufactured by a method such as arranging insulated conductors in parallel, using the parallel conductors as warp threads, and weaving the weft threads into a completely flat fabric (weaving type flat cable).

Flat cables can connect each conductor at once, making wiring work easier, faster, and more streamlined. It has the advantage that the wiring cable itself occupies a small space and the equipment can be made smaller, so it can be used for internal wiring of other electrical and electronic equipment such as computers, communication equipment, automatic machine tools, copying machines, facsimile machines, etc. It has been used as a wiring route, external wiring route, etc.

By the way, the electrical/electronic equipment mentioned above includes many movable parts, such as an information transfer mechanism, a recording mechanism, and a display mechanism, but the cables connected to these movable mechanisms are It must be sufficiently soft and flexible to follow movements with virtually no resistance, and it must have excellent repeated bending resistance that will not cause wire breakage problems over a long period of time even when subjected to intermittent repeated bending. is required. For example, a cable used for connection to a movable mechanism as in the above example is required to have a long bending life that can withstand severe repeated bending of 10 million times or more.

Because flat cables have a flat structure, they suffer less distortion when bent than so-called round cables, making it easier to obtain flexibility, making them suitable for applications where they are connected to movable mechanisms and subject to repeated bending. ing.

Also, among flat cables, those with twisted wires (for example, Dore-Flex, manufactured by Gore, USA) are more flexible and suitable for bending than those with individual conductors made of solid wires. However, even though it is a stranded conductor, its constituent wires are solid, so even though it is more flexible than a single wire conductor with the same cross-sectional area, it still has considerable bending resistance and restoring resistance. Therefore, even flat cables using stranded wires as internal conductors have a certain limit in their flexibility, and are often unsuitable for use with certain types of equipment. In addition, in the case of both solid and stranded wires, repeated bending causes hair-like cracks to deteriorate at the bent portion, which increases the electrical resistance of the wire and eventually results in broken wires (broken wires), resulting in a relatively short bending life. .

In terms of the bending life of flat cables,
If each conductor has a flat cross section than if the individual conductor has a round cross section, less distortion occurs during bending and the bending life is better. However, when the insulation coating is removed from the cable end for connection, the bending life of the flat conductor in that part becomes extremely short, compared to cables using round or square conductors with the same cross-sectional area. The overall width is wide, which impairs high-density mounting of conductors, and is susceptible to sharp bends.
There are drawbacks such as.

This proposal eliminates the various drawbacks of the conventional flat cables mentioned above, and provides a cable that is more flexible than the conventional cables and has excellent repeated bending resistance. The individual conductors 1 of A are wires 11 made of stretched porous polytetrafluoroethylene resin (PTFE) that is highly flexible, has high tensile strength, and is electrically conductive, specifically, conductive, for example. Stretched porous PTFE mixed with conductive filler such as carbon black to give conductivity
A conductive layer 12 is formed by using a monofilament yarn, a multifilament yarn, or a thin string-like material as a core material, and a conductive material tape 12 ₁ is spirally wound around the core material along its length (the third , 4)
A conductor group in which a plurality of conductors 1 are arranged in parallel is coated with an insulating material 2 made of fluorine-based resin, and the conductors are insulated and supported from each other.

The expanded porous PTFE used as the core wire 11 of the conductor 1 in this invention has a structure that is significantly different from commonly used chemical fibers, and its flesh is formed into a continuous porous structure. It exhibits high flexibility due to its porous structure, and also has high tensile strength due to stretching. The manufacturing method of this material was
This method is disclosed in Japanese Patent Laid-Open No. 18991 and Japanese Patent Application Laid-Open No. 1983-22881, and is summarized as follows.

That is, a suitable amount of a conductive material such as conductive carbon powder is added to a mixture of PTFE fine powder and a liquid lubricant (liquid hydrocarbon such as solvent naphtha, white oil, alcohol, petroleum ether, benzene, etc.).
A mixture containing metal powders such as copper, silver, aluminum, and nickel, metal oxides, and metal nitrides is preformed, and this preform is extruded and shaped into sheets, films, and tubes by rolling or other means.・Rod-shaped・
Form into the desired shape such as tape or string. After removing the liquid lubricant from the molded product (it is not necessary to remove it, but better results will be obtained), it is heated uniaxially or multiaxially in an unsintered state for about 1.5~1.
Stretch it 500 times. Through this stretching process, the flesh of the molded product becomes a continuous fine porous structure in which countless micronodules are interconnected by countless fine fibrils. Then, the stretched product is heat-set at a temperature of 327°C or lower, either as it is or while the stretched product is held down so as not to shrink due to heat, or at 327°C.
Sintering is carried out at a temperature higher than that. If the obtained product is originally string-like or thread-like, it can be used as it is as the core 11 of the conductor 1, and if it is a sheet-like product, it can be cut into a string-like or thread-like shape and used, or it can be made into a fiber-like material. Use by loosening and rolling or twisting into a string or string.

The above-mentioned conductive stretched porous PTFE strings or threads have extremely high heat resistance, are more flexible than general chemical fibers, and have a tensile strength of 10%.
It has a large weight of Kg/mm ² and hardly elongates in the longitudinal direction.

The conductive material tape 12 ₁ wound around the wire 11 to form the conductive layer 12 generally has a thickness of
Copper foil and other highly conductive metal foils with a thickness of about 0.01 to 0.1 m/m, foils plated with silver, tin, nickel, etc., synthetic resin films with metal vapor-deposited or metal foil laminated, etc. and cut into narrow tapes with an appropriate width, for example, about 0.2 to 2 m/m.

And conductive material tape 12 ₁ as described above,
A gap exists between the spirals along the length around the wire 11 made of conductive expanded porous PTFE,
Alternatively, the conductor 1 is made by winding each spiral while appropriately overlapping each other without any gaps. The conductor layer 12 may be formed by winding not only one layer but also two or more layers. Further, in this case, the winding direction may be reversed layer by layer as shown in the example in FIG.

A large number of the above-mentioned conductors 1 are arranged in parallel in the same manner as in the prior art, and the conductor group is sandwiched between two fluorine-based resin tapes on a sandwich strip, and an insulating coating 2 is provided by thermocompression bonding or adhesive. Alternatively, the insulating coating 2 of fluorine resin is provided by passing the parallel conductor group through the head of a resin extruder. Alternatively, the conductors 1, which have been individually insulated and coated with fluororesin, are brought into contact with each other in parallel, and the coatings of adjacent conductors are bonded or fused together to integrate them as a whole. Or the conductor 1 treated with the above insulation coating
A flat cable is obtained by arranging the cables in parallel and weaving them with weft threads.

That is, as described above, the conductor 1 is made of a conductive stretched porous material that is highly flexible and has high tensile strength.
When a flat cable is constructed using a PTFE wire 11 as a core and a conductive layer ₁₂ formed by winding a conductive material tape 121 spirally along its length around the core, (1) Individual The conductor 1 has a conductive layer 12 around the wire 11 made of conductive expanded porous PTFE, and a long conductive material tape with a length of at least 1.1 times the line length, usually at least twice the line length. Because it has a coil structure wound in a spiral, when a bending force is applied, the conductor layer 12 itself becomes extremely flexible in the same way as, for example, a curled cable of a telephone receiver or a flexible coil structure tube. In addition, the conductive expanded porous PTFE wire 11 specified as the core has an extremely low coefficient of friction (PTFE has an extremely low coefficient of friction compared to other synthetic resins), and the microfibers exhibit flexibility. It is extremely flexible and has excellent flexibility due to its special microfiber porous texture that can be freely displaced, and is easily bent by bending force. 12, and the flexibility of the conductor layer 12 is not inhibited.

Therefore, the flat cable A exhibits much better flexibility than conventional cables using single wire or stranded wire as the internal conductor, and has low bending resistance and restoring resistance.

(2) The conductor layer 12 has a highly flexible coil structure as described above, and has a conductive stretched porous core.
The wire 11 made of PTFE has high tensile strength and little elongation in the longitudinal direction of the conductor 1 as a whole, so the internal strain that occurs in the conductor 1 itself due to bending is small, and it has better durability than one using a single wire or stranded wire as a conductor. It is strong against repeated bending and has a long bending life.

(3) Compared to those using flat conductors as conductors,
Even if the coating is peeled off, the flexibility and repeated bending resistance of the exposed conductor 1 are maintained well over a long period of time, the packaging density of the conductor is increased, and it is resistant to sharp bending.

(4) The weight of the conductor 1 itself is less than 1/2 that of a single conductor wire or stranded wire of the same diameter, and therefore the overall weight of the cable is also lighter.

(5) Since the wire 11, which is the core of the conductor, is conductive, continuity is maintained even when the conductive material tape ₁₂₁ is cut due to repeated bending over a long period of time, resulting in extremely high durability. Becomes a conductor. Moreover, since the striations 11 themselves have conductivity,
For example, mistakes when connecting to a pressure welding type connector are reduced.

(6) As the insulation coating material 2, PTFE, PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), FEP (tetrafluoroethylene-hexafluoropropylene copolymer), ETFE (ethylene-tetrafluoroethylene When a flat cable is constructed using a fluorine-based synthetic resin such as
It maintains sufficient flexibility over a wide temperature range of about 200°C, does not deteriorate its electrical signal transmission characteristics, and has good low-temperature and high-temperature resistance. Since the inductivity has almost no frequency dependence, there is almost no pulse distortion during pulse transmission. The self-lubricating property of fluororesin allows for good slippage between it and the conductor, greatly increasing its flexibility. A flat cable with features such as good chemical resistance, high flexibility, and excellent repeated bending resistance can be obtained.

Note that if the conductor layer 12 is formed by winding two or more conductive material tapes 12 ₁ in multiple layers with the winding direction reversed for each layer, as shown in the example in FIG. , the twist of the conductor 1 is eliminated, and no distortion occurs in the cable when it is made into a cable. As a result, the cable is bent uniformly, so stress is not concentrated on a portion of the conductor 1, and the bending life is improved. Furthermore, since no twist remains in the conductor 1, the stress applied to the connection portion of the conductor 1 during connector connection is reduced, and disconnection is prevented. In addition, when forming the insulating coating 2, since there is no distortion (twisting) in the conductor 1, the coating will not peel off after being sandwiched between two resin tapes and integrated, and in the case of extruded coating. This also has the effect of reducing the difference in pitch between the lines of the conductor 1. In addition, since the conductor 1 has no twisting, there is no need to untwist it as would be the case when the conductor is twisted in layers in the same direction.Furthermore, when the tension is lost during the formation of the insulation coating 2, compared to the case in which the conductor is twisted in layers in the same direction, it is not necessary to straighten the twist. The conductor layer 12 is difficult to stretch and is easy to handle.

Further, the conductor layer 12 includes a plurality of conductive material tapes 12.
By wrapping ₁ in two or more layers, the conductor resistance is lower than that in the case of a single tape, and when some of the tapes are cut when connected to a pressure welding connector, However, the remaining tape ensures continuity and improves reliability. Additionally, each conductive material tape has a thickness of 0.01~0.1mm
Because it is so thin, its flexibility will not be lost when it is wrapped in layers.

Flat cable A has a shield layer made of metal foil, conductive resin layer (conductive PTFE, etc.) to the extent that the flexibility of the cable is not significantly impaired.
A jacket or the like may be attached to increase mechanical strength.

For the purpose of obtaining cable A with excellent heat resistance, for example, PTFE, stretched porous material is used as the insulation coating 2.
Since it is a fluorine-based resin such as PTFE, PFA, FEP, ETFE, or PVdF (polyvinylidene fluoride), it can be combined with the heat-resistant resin to create a cable with excellent heat resistance.

When a heat-resistant resin is used as the material for the insulating coating 2, either a pressure bonding method or an extrusion method is used depending on the physical properties of the resin. For example, in the case of PTFE, which is difficult to melt extrude, multiple conductors are arranged in a parallel spaced relationship via grooved guide rolls.
Then, between a pair of crimping rolls, the two sheets from above and below are
All you have to do is feed the PTFE tape, press it together, and bake it. In the case of meltable resins such as FEP and ETFE, the conductors arranged as described above are passed through the head of an extruder, and then the PTFE tape is melted. Coat with resin and cool to make a flat cable.

Example Conductor core 11... Contains graphite, diameter
A 0.27 mm unfired PTFE monofilament was heated to 320°C in heated air, stretched 6 times, and then stretched to 340°C in heated air for 1 time while applying tension to prevent shrinkage.
A conductive expanded porous PTFE monofilament with a diameter of 0.20 mm obtained by holding for a minute.

Conductive material tape 12 ₁ ...thickness 35μm, width 0.4mm
copper foil tape.

The copper foil tape 12 1 is wound 4 times along its length around the conductive expanded porous PTFE monofilament serving as the core ₁₁ at a pitch of 0.6 mm, with the winding direction reversed for each layer, and the diameter is 0.4 mm. A copper foil-wrapped conductor 1 was manufactured. This conductor 1 had no twists and did not need to be straightened.

10 of the above conductors 1 are arranged in parallel with each other with a conductor interval of 1.27 mm, and the parallel conductor group is sandwiched between two sheets of unfired PTFE tape with a thickness of 0.2 mm on a sandwich bench, and then it is placed between two grooved rolls. was passed through and integrated into the whole.

The cable is then immersed in molten salt at 390°C for 18 seconds while applying tension in the length direction to unfire it.
The conductor spacing is reduced by firing the PTFE tape.
I got a 1.27mm 10 flat cable.

Comparative Example In the above example, seven twisted silver-plated conductors with a diameter of 0.12 mm were used as conductor 1, and the other procedures were the same to obtain a PTFE-coated 10-core flat cable with the twisted conductor as the inner conductor. .

When the cable according to the present invention obtained in the above example and the cable of the comparative example were bent by hand and their flexibility was compared, the former showed much more flexibility, and was flexible and had less bending resistance and restoring resistance. It was hot.

Repeated bending resistance test Test method: As shown in Figure 5, a fixed plate 3 and a movable plate 4 positioned above it in parallel and driven in reciprocating motion.
A test piece cable A bent into a U-shape is interposed between the test piece cable A and both ends of the cable are fixed to the fixed plate 3 and the movable plate 4 with fasteners 31 and 41, respectively. Then, adjust the distance between the two plates 3 and 4 to connect the cable A.
The radius of the U-shaped bend is maintained at 25 mm, and the movable plate 4 is driven in reciprocating motion repeatedly at a cycle of 1 second and a stroke of 200 mm until the conductor of cable A is disconnected for at least 10 ⁶ seconds or more, that is, instantaneous. Check the number of times the conductor is bent until a disconnection phenomenon occurs (a crack or hair in the conductor becomes disconnected for a very short time due to bending. It is conductive when it is not bent).

Using the above test method, the cable according to the present invention obtained in the above example was tested for its repeated bending resistance, and as a result, no momentary disconnection phenomenon was observed even after 20 million bends. On the other hand, the cable obtained in the comparative example had an average of 2.56 million cycles.

That is, the cable according to the present invention has the flexibility of the conductor layer itself due to the coil-wound structure of the conductor layer 12 of each conductor 1, and the superiority of the wire 11 made of conductive expanded porous tetrafluoroethylene resin used as the core. This combination of flexibility and excellent low friction properties resulted in extremely excellent repeated bending resistance.

Furthermore, since the striations 11 are made of a fibrous material that is highly flexible and has high tensile strength and is electrically conductive, it is far less likely to be cut by bending than the electrically conductive material tape ₁₂₁ . Therefore, even when the conductive material tape 12 ₁ is broken due to repeated bending, the conductor 1 is maintained in a conductive state by the striations 11, dramatically increasing its life as a conductor and making the cable resistant to repeated bending. Becomes excellent in sex.

In addition, in the above embodiment, the insulation coating 2 of the cable is
Cables formed by extrusion using meltable resins such as PFE, FEP, EPE, and ETFE also have excellent flexibility and bending life similar to those obtained in the examples. It also had excellent low-temperature resistance, high-temperature resistance, and chemical resistance.

In addition, it is made of stretched porous conductive material with strong tensile strength.
When winding copper foil tape 12 ₁ in multiple layers along its length around a wire 11 made of PTFE, the winding direction of each layer is reversed as shown in the example in Fig. 4, and the resulting conductor In No. 1, there was no twist, there was no need to straighten the twist, and the bending resistance of the completed cable using this was the same as when the winding direction was the same.

[Brief explanation of drawings]

Figure 1 is a plan view of a part of the flat cable, Figure 2 is an enlarged cross-sectional view taken along the - line in Figure 1, Figure 3 is an enlarged front view of a part of the internal conductor, and Figure 4 is another example. The same figure as above and FIG. 5 are diagrams showing the procedure for repeated bending resistance test. A is a flat cable, 1 is a conductor, 11 is a conductor core made of conductive expanded porous PTFE, ₁₂ is a conductive material tape wrapped around the core, 12 is a conductor layer formed by the winding, 2 is insulation coating,
3 is the fixed plate of the bending tester, and 4 is the movable plate of the same.

Claims (1)

[Scope of utility model registration request] A conductor 1 is formed by forming a conductor layer 12 by spirally wrapping a conductive material tape 12 ₁ around the core wire 11 made of a conductive porous polytetrafluoroethylene resin. A plurality of conductors are arranged in parallel, and the conductor group is covered with an insulating material 2 made of fluorine resin.
A flat cable whose conductors are supported and insulated from each other.