JPH0126002Y2 - - 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 sandwich bench 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 and 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 moving parts, such as an information reading mechanism, a recording mechanism, and a display mechanism, but the cables connected to these movable mechanisms are affected by the movement of the mechanism. It must be sufficiently soft and flexible so that it can follow the wire virtually without resistance, and it must have excellent repeated bending resistance that will not cause disconnection troubles over a long period of time even when subjected to intermittent repeated bending. This 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, stranded cables (for example, Dore-Flex, manufactured by Gore, Inc., USA) are more flexible and suitable for bending than those in which the individual conductors are single 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. Each conductor 1 of A has a core wire 11 made of stretched porous polytetrafluoroethylene resin (PTFE), which is highly flexible and has a strong tensile strength, and a conductive material is arranged around it along its length. Tape 12 ₁ in two or more layers,
It is characterized in that the conductor layer 12 is formed by spirally winding each layer with the winding direction reversed (FIG. 3).

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 is disclosed in Japanese Patent Publication No. 18991/1982 and Japanese Patent Application Laid-open No. 22881/1989, and is roughly as follows.

That is, a mixture of PTFE fine powder and a liquid lubricant (liquid hydrocarbon such as solvent naphtha, white oil, alcohol, petroleum ether, benzene, etc.), or if desired, an appropriate amount of other materials such as conductive carbon powder, etc. A mixture containing organic and inorganic sub-compounds is preformed, and this preform is shaped into a desired shape such as a sheet, film, tube, rod, tape, string, etc. by extrusion, rolling, etc. Form into. After removing the liquid lubricant from the molded product (it is not necessary to remove it, but better results will be obtained if it is removed), it is heated approximately 1.5 to 1500 times uniaxially or multiaxially in an unsintered state. Stretched. 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.

Next, the stretched product is held as it is, or the stretched product is held down so as not to shrink due to heat.
Heat set at a temperature below 327°C or sintered at a temperature above 327°C. 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 stretched porous PTFE strings or filaments have extremely high heat resistance, are more flexible than general chemical fibers, and have a tensile strength of 10 kg/mm ²
It is large and hardly elongates in the longitudinal direction.

The conductive material tape 12 ₁ that is wound around the wire 11 to form the conductor 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.

Then, the conductive material tape 12 ₁ as described above is wound around the wire 11 along its length, with gaps between the spirals, or with the spirals appropriately overlapping each other without any gaps. Winding shall be done in two or more layers, with the winding direction being reversed for each layer.

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 sheets of insulating resin tape on a sandwich bench and insulated by thermocompression bonding or adhesive 2. Alternatively, the insulation coating 2 is provided by passing the parallel conductor group through the head of a resin extruder. Alternatively, the conductors 1 which have been individually insulated 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. Alternatively, a flat cable can be obtained by arranging insulated conductors 1 in parallel and weaving them with wefts.

That is, as described above, the conductor 1 is a stretched porous PTFE wire 11 that is highly flexible and has high tensile strength.
is used as a core, and conductive material tape ₁₂₁ is wound around the core in multiple layers along the longitudinal direction, and the winding direction of each layer is reversed to form a conductive layer 12.
(1) Each conductor 1 has a conductor layer 12 around the wire 11.
When a bending force is applied to the coil, the conductive material tape is wound spirally within the length of the line. Conductor layer 1
2 itself exhibits extremely excellent flexibility in the same way as, for example, the curled cable of a telephone receiver or a flexible coil structure tube, and the expanded porous PTFE wire 11 specified as the core has a high resistance to friction. The coefficient is extremely small (tetrafluoroethylene resin has an extremely small coefficient of friction compared to other synthetic resins),
It is extremely flexible and has excellent flexibility due to its special microfiber porous texture that allows microfibers to freely displace. The conductor layer 12 easily slips and slips between the conductor layer 12 and the conductor layer 12.
does not impede the flexibility of the

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

(2) As mentioned above, the conductor layer 12 has a highly flexible coil structure, and since the core wire 11 has high tensile strength and has little elongation in the longitudinal direction of the conductor 1 as a whole, the conductor 1 can be easily bent by bending. The internal strain generated in the conductor itself is small, and the conductor has stronger resistance to repeated bending and has a longer bending life than a conductor using a single wire or a stranded wire.

(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 conductor layer 12 is formed by winding the conductive material tape 12 ₁ layer by layer with the winding direction reversed, the conductor layer 12 is formed by winding the conductive material tape 12 1 layer by layer in the opposite direction. There is no twisting, and there is no distortion 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. Also, when forming the insulation coating 2, the conductor 1 is strained (twisted).
Since there is no coating, the coating will not peel off after being sandwiched between two resin tapes and integrated.
In the case of extrusion coating, there is also the effect that the difference in pitch between the lines of the conductor 1 is reduced. In addition, since the conductor 1 does not have any twisting, there is no need to untwist it as would be the case with conductor 1 that is twisted in layers in the same direction.Furthermore, even when tension is applied during the formation of insulation coating 2, it can be twisted in layers in the same direction. Compared to conductor layer 1
2 is difficult to stretch and easy to handle.

(6) The conductor layer 12 includes a plurality of conductive material tapes 12 ₁
Since the tapes are wrapped in layers, the conductor resistance is lower than that of a single tape, and even if some of the tapes are cut when connected to an insulation displacement connector, the remaining Reliability is also improved because the tape ensures continuity. 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.

In addition, a shield layer made of metal foil or a conductive resin layer (conductive PTFE, etc.) or a jacket for increasing mechanical strength should be added to the flat cable A to the extent that the flexibility of the cable is not significantly impaired. There is also.

For the purpose of obtaining cable A with excellent heat resistance, a fluorine-based resin such as PTFE, expanded porous PTFE, PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), FEP is used as the insulation coating 2.
(Tetrafluoroethylene-hexafluoropropylene copolymer),
ETFE (tetrafluoroethylene-ethylene copolymer),
Other heat-resistant resins such as PVdF (polyvinylidene fluoride) may be used. The wire 11 made of expanded porous PTFE used as the core of each conductor 1 is itself a material with excellent heat resistance, so by combining it with the heat resistant resin, it becomes 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.

As mentioned above, a stretched porous PTFE wire is used as the core 11 of the conductor 1, and PTFE/PTFE wire is used as the covering material 2.
If the flat cable is constructed using fluorine-based materials such as PFA, FEP, and EPE, -196 to
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 dielectric constant has almost no frequency dependence, there is almost no pulse rounding during pulse transmission. A flat cable with features such as good chemical resistance, high flexibility, and excellent repeated bending resistance can be obtained.

Example Conductor core 11...An unfired PTFE monofilament with a diameter of 0.27 mm was heated to 320°C in heated air, stretched 6 times, and held in heated air at 340°C for 1 minute while applying tension to prevent shrinkage. The diameter obtained by
0.20mm expanded porous PTFE monofilament.

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

The copper foil tape 1 is placed along the length around the expanded porous PTFE monofilament that is the core 11.
2 ₁ was wound four times at a pitch of 0.6 mm with the winding direction reversed for each layer to produce a copper foil-wound conductor 1 having a diameter of 0.4 mm. This conductor 1 had no twists and did not need to be straightened.

Arrange the 10 conductors 1 in parallel with each other with a conductor interval of 1.27 mm, sandwich the parallel conductor group between two sheets of unfired PTFE tape with a thickness of 0.2 mm on a sandwich bench, and then roll it between two grooved rolls. The space was passed through to integrate 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.
A 1.27mm 10-core flat cable was obtained.

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 internal 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 4, 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 inserted between the test piece cable A and both ends of the cable are fixed to the fixed plate 3 and the movable plate 4 using 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 repeatedly driven in reciprocating motion with 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, i.e. Check the number of times the conductor is bent until a momentary 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, which was 15 million times on average.

On the other hand, the cable obtained in the comparative example above has an average
It was 2.56 million times.

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 excellent flexibility of the wire 11 made of expanded porous polytetrafluoroethylene resin used as the core. The combination of flexibility and excellent low friction properties resulted in extremely excellent repeated bending resistance. Furthermore, since the conductor layer 12 has a coil-wound structure in which the conductive material tape 12 ₁ is made up of two or more layers and the winding direction is reversed for each layer,
Since the conductors 1 are not twisted and exhibit uniform flexibility, the bending life and flexibility of cables using these conductors 1 are improved. Furthermore, compared to conductive material tapes wound in layers in the same direction, the conductor layer 12 is less stretchable and does not twist, making it easier to handle, resulting in improved workability.

In addition, in the above embodiment, the insulation coating 2 of the cable is
Cables formed by extrusion using meltable resins such as PFA, 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.

[Brief explanation of the drawing]

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 shown in Figure 1, Figure 3 is an enlarged front view of a part of the internal conductor, and Figure 4 is the repeated bending resistance. A diagram showing the procedure for the trial examination. A is a flat cable, 1 is a conductor, 11 is a conductor core, 12 ₁ is a conductive material tape wrapped around the core,
12 is a conductor layer formed by winding two or more layers, 2 is an insulating coating, 3 is a fixed plate of the bending tester, and 4 is a movable plate thereof.

Claims (1)

[Claims for Utility Model Registration] (1) In a flat cable, each parallel conductor 1 is
A wire 11 made of stretched porous polytetrafluoroethylene resin is used as a core body, and two or more layers of conductive material tape 12 ₁ are wound around the wire 11 along the length thereof, with each layer being wound in the opposite direction. A flat cable is formed by winding the conductor layer 12 around the wire. (2) The flat cable according to claim (1) of the utility model registration, wherein the material of the insulation coating 2 of the flat cable is a fluororesin. (3) The flat cable according to claim 1 or 2 of the utility model registration claim, wherein the flat cable has a conductive layer on its outer surface.