JPH0578157B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of the Invention) The present invention relates to a novel heating element, and more particularly to a novel heating element that effectively generates heat by passing an electric current through a fiber bundle.

(Prior Art) It has been well known to generate heat by passing an electric current through a metal having an appropriate resistance value, such as a low resistance metal such as a nichrome wire. However, since these low-antibody golds lack ductility, they cannot be made into thin fibers, which are not flexible and stiff. On the other hand, metals that have excellent ductility and can be made into thin fibers always have a low resistance value (copper, aluminum, iron, etc.), so when current is passed through them, an excessive current flows, making them difficult to use as heating elements. For this reason, attempts have been made to create flexible heating elements similar to fibers.
For example, Utility Model Application No. 51-99829 and Utility Model Application No. 51-
Publication No. 115653 describes using a large number of stainless steel fibers cut into short lengths, arranging them in parallel and converging them to form a string, and stretching the fibers while correcting thick and thin unevenness, to use as a heating element. Short fibers made of synthetic resin such as polyamide and polyester are mixed with stainless steel fibers at a ratio of approximately 1:4.
A heating element is disclosed in which the stainless steel fibers are uniformly mixed at a ratio of 1,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000. However, since these heating elements are made by uniformly mixing stainless steel fibers and synthetic fibers and then pulling them together to form a blended yarn, it is difficult to achieve a uniform resistance value along the yarn axis. It could not be manufactured industrially. In other words, it is difficult to mix stainless steel fibers and synthetic fibers uniformly because their physical properties are significantly different, and in particular, their surface friction coefficients are different.
When the fibers are pulled together to make them thinner, the stainless steel fibers having a high friction coefficient gather together to form a lump, so it has been impossible to arrange the stainless steel fibers uniformly along the yarn axis direction. In particular, in order to equalize the contact points or number of contacts between stainless steel fibers, it is preferable to use long fiber lengths, but it is completely impossible to obtain a heating element using such long stainless steel fibers. It was hot.

(Objective of the Invention) The object of the present invention is to use ordinary metal fibers that easily become fibers, and by changing them into materials with appropriate resistance, the material is flexible and flexible, and a large current can flow through it. The present invention proposes a heating element that can provide an appropriate heat generation state without any difference.

(Structure and operation of the invention) That is, the present invention is a fiber bundle in which finite length discontinuous fibers having conductivity and finite length discontinuous fibers having no conductivity are mixed, The average fiber length of the continuous fibers is in the range of 100 to 800 mm, and the number of conductive discontinuous fibers in any cross section of the fiber bundle is on average 10 or more, and the fiber bundle is made to contain air. Convergence is imparted through processing, and
The heating element is characterized in that the conductive discontinuous fibers are brought into contact with each other.

The present invention will be explained in detail with reference to the figures. Figure 1A
indicates a conventional wire-like resistor such as nichrome wire. These resistors have an appropriate resistance value that generates a moderate amount of heat when current is passed through them. However, in order to make such a wire flexible, if you try to make it thinner and make it multi-layered, generally, such low-antibody alloys are not ductile and there is a limit to how thin they can be stretched, so it is difficult to make wires that are too thin like B. I can't. On the other hand, metals such as copper, aluminum, and iron have good ductility and can be made into thin, mulched fibers like C, but metals with good ductility are generally good electrical conductors with extremely low resistance, so If a current is passed through it, too much current will flow through it, making it difficult to use as a heating element.

On the other hand, D schematically shows the heat generating pair of the present invention, and the metal wires are all cut into short lengths by tearing them into strips, and none of them are continuous throughout. Therefore, in the conventional heating element, the current flows directly to the constituent metals as shown in E, whereas in the case of the heating element of the present invention, the current flows discontinuously, so the current always flows through the contact surfaces A, B, C, as shown in F. It flows through d and ho. However, since contact resistance occurs at the contact surface (due to the transfer of free electrons), the heating element as a whole has a larger resistance value than when current flows directly.

Therefore, even a material that is a good electrical conductor with a low resistance value has a resistance value similar to that of a high resistance alloy, and even when current is passed through it, an appropriate amount of heat is generated without causing an excessive current to flow. Therefore, common alloys with low resistance that can be stretched thin (copper, iron, aluminum, etc.) can also be made into heating elements, making it possible to create extremely soft and flexible heating elements that have never existed before. (FIG. 1 is a diagram explaining the structure of the heating element). Also, regarding how to make such a heating element, FIG. 2 is a diagram showing an example of a preferred process. In other words, 1 in Figure 2 G is a bundle of fine electrical conductors such as copper, steel, and aluminum formed into thin fibers, and as it is, the electrical resistance value is as low as 10 ^-5 to ^{10 -6} Ω-cm. Due to its resistance value, too much current flows through it, making it unusable as a heating element. When this is forcibly stretched between a pair of rotating rollers 2 and a pair of rollers 3 that rotate several times to several tens of times faster, as shown in Figure 2H, all of the constituent fibers are torn into pieces. , a collection of short fibers. Since they tend to fall apart as they are, they are fused together using a compressed air nozzle 4 or the like to form a fiber bundle. When a conductor is cut short to form discontinuous fibers like this, even if current is applied to it, it does not flow directly, but instead flows through contact resistance, so the resistance value increases from several to several tens of times the original value and generates heat. The resistance value can be changed within a range that is preferable for the body.
Therefore, in this case, in order to generate heat uniformly along the yarn axis, it is desirable that the contact resistance at various points does not change much, but this is due to the law of large numbers, as the number of contact points increases as the number of fibers increases. In this case, the average difference between the contact points at various locations is unexpectedly reduced, and temperature variations become virtually no problem in practice. In order to expect this, it is desirable to have at least 10 or more, preferably 25 or more constituent fibers in each part of the fiber bundle in order to average out the contact points. In addition, all the constituent fibers must be discontinuous fibers with a finite length, but if the fiber length is too short, the number of contact points per discontinuous fiber will decrease and become unstable. It is better to have a temperature of 100mm or more. By increasing the length in this way, contact with many fibers increases and stability is achieved. However, if the length is too long, the amount of components flowing directly through the fibers will increase, so even if it is long, the average
It is better to make it less than mm. In addition, in order to keep the fibers in proper contact, it is necessary to not only bundle the fibers together, but also to
As shown in 4 in FIG. 2, it is preferable to impart an appropriate conjugation state by twisting or twisting with a compressed air nozzle or the like.

Next, the present invention requires electrically insulating fibers to be composited with the electrically conductive discontinuous fibers. That is, by adding the insulating fibers, the chance of contact between the conductive fibers can be increased or decreased as appropriate, resulting in a preferable contact resistance, and a good heating element can be obtained. Furthermore, since the number of fibers forming the fiber bundle increases, the shape of the fiber bundle is kept stable even with a relatively small number of conductive fibers, and the resistance value is also stabilized. Of course, it goes without saying that features such as adding color by combining with fibers that have good dyeability, or improving the hard feel of metal by combining with flexible fibers or fibers that have a good feel, can also be used depending on the purpose. Nor. In order to expect these combined effects, it is particularly effective to mix insulating fibers in an amount of about 70 to 95% of the total, but it is not limited to this. In this way, by mixing it with insulating fibers, it is possible to create a heating element with an electrical resistance that is an order of magnitude higher. Such a composite fiber bundle can be made, for example, by a method as shown in the process diagram of FIG. That is, in addition to the conductive material 1, the electrically insulating continuous fiber bundle 5 is supplied to the roller 2 so as to be superimposed, and both are torn off together in the same manner as shown in FIG. By doing this, both fibers are mixed together at the same time as they are cut, forming a well-mixed composite fiber bundle.

Further, the conductive fibers used in these materials preferably have an electrical resistance value of the order of 10 ^-5 to ^{10 -6} Ω-cm. If the resistance value is higher than this, it will be difficult to draw it into a thin fiber. As a guideline for thinness, a diameter of 60 microns or less, preferably 16 microns or less is preferable because it has flexibility. As the material, it is convenient to use metals such as copper, aluminum, steel, etc. Among them, stainless steel is preferable because it does not oxidize even when it generates heat. Besides that,
Fiber plated with metal or polyacetylene,
A conductive polymer such as polypyrrole may also be used. In addition, when composited with electrically insulating fibers, if ordinary synthetic fibers, recycled fibers, or natural fibers are used as the insulating fibers, the electrical properties are much higher than that of conductive fibers, and any of them will meet the purpose. However, if wholly aromatic polyamide is used, favorable results can be obtained without deterioration or ignition even when the conductive fibers, which have high heat resistance, generate heat and the temperature rises. Heat-resistant polymer fibers such as polybenzimidazole, polyimide, and polyetheretherketone are also suitable. The apparent resistance value of the heating element made in this way is 10 ^-4 ~
It is desirable that the resistance be on the order of 10 ^-2 Ω-cm.
That is, if it is lower than the order of 10 ^-4 Ω-cm, too much current will flow, resulting in overheating, or a low voltage and current power source will be required, making control difficult. On the other hand, if the resistance is higher than 10 ^-2 Ω-cm, the current may be too low and the temperature may not rise sufficiently, or a high voltage may be applied to force the current to flow, increasing the danger.

In addition, with conventional heating elements in which metal powder or carbon powder is kneaded into polymers or coated on different surfaces, current cannot flow unless the powders stick to each other, so the heating element will not work unless the mixing ratio is increased considerably. ,
In the case of the present invention, it is in the form of long fibers, especially 100
This is especially true when the fiber length is as long as ~800 mm, but since the number of contact points increases significantly, it has the great advantage that even a small mixing ratio can become a heating element. For example, unless 50% or more of the powder is mixed in, a current sufficient to generate heat will not flow, but in the present invention, even with 5 to 30%, it is possible to flow the current necessary for generating heat in an extremely stable manner.

Example 1 Polymetaphenylene isophthalamide long fibers were added to a bundle of 1500 continuous steel fibers with a volume resistivity of the order of 10 ^-5 Ω-cm and stretched to a diameter of 8 microns. Approximately 12,000 bundles are layered and then torn 50 times in the process shown in Figure 3 to produce polymetal phenylene isophthalamide fibers (blending ratio 89%) with an average fiber length of approximately 310 mm, and an average fiber length of approximately 260 mm. of steel fiber (mixing ratio 11%),
A discontinuous fiber bundle having an average number of about 30 steel fibers was formed, and this was further passed through an air swirling nozzle having a pressure of 5 kg/cm ² to be bound and wound. The apparent volume resistivity at this time was on the order of 10 ^-3 Ω-cm. Next, this fiber bundle is woven into a plain woven fabric, and the relationship between the voltage (E) and the current flowing at that time (I) when an alternating current is passed from both ends of this woven fabric is shown in Figure 4, and the surface of the woven fabric at that time is shown. The relationship with temperature (T) is shown in Figure 5.
The resulting heating element is not only flexible but also has the same fluffy feel and bulkiness as conventional fibers, making it an unprecedented and revolutionary heating element that can be used in general clothing without any problems. Ta.

Example 2 Volume resistivity value is on the order of 10 ^-5 Ω-cm,
As in Example 1, a bundle of continuous steel fibers stretched to a diameter of 8 microns and a bundle of continuous polyester fibers with a single fiber denier of 2 de are fed in parallel to the process shown in Figure 3. Distance between rollers: 1000 mm, and the polyester fiber with an average fiber length of about 280 mm (blending ratio:
82.8%) and steel fibers (blending ratio: 17.2%) with an average fiber length of approximately 240 mm, and a fiber bundle with an average fiber length of approximately 280 mm.
A fiber bundle of polyester fibers (blending ratio: 70.6%) and steel fibers (blending ratio: 29.4%) with an average fiber length of about 240 mm was formed, and the fiber bundle was conjugated by passing it through an air swirling nozzle having a pressure of 3 kg/cm ² . It was wound as a blended yarn with yarn count: 10/1. 300T/M for the blended yarn
Heating element A (PET: 82.8%/SS: 17.2
%), and heating element B (PET: 70.6%/SS: 29.4
%) was obtained. A load was applied to the heating elements A and B, and the electrical resistance value (x10 ^-3 Ω·cm) was measured.
The results are shown in Figure 6. In both heating elements A and B, there was little change in the electrical resistance value due to the load weight, and it was confirmed that a stable electrical path was formed.

Comparative example 1 The fixed volume resistance value is on the order of 10 ^-5 Ω-cm,
The fiber length is 30 to 90, made from a bundle of continuous steel fibers stretched to a diameter of 8 microns.
mm short steel fiber bundles and single fiber bundles made of polyester with a single fiber denier of 2de and a fiber length of 64 to 89 mm are mixed in the drawing process of a normal spinning process, and then in two further drawing processes. The mixed fiber bundle is doubled (heavy), drafted (stretched) each time to mix the fibers in the mixed fiber bundle, and aligned in one direction, followed by a roving process →
In the spinning process, the fiber bundle is made thinner and the final
300T/M twist and yarn count: 10/1 heating element (PET: 90%/SS: 10%), and heating element D
(PET: 70%/SS: 30%) was obtained. The heating element C,
A load was applied to D and the associated electrical resistance value (x10 ^-3 Ω·cm) was measured. The results are also shown in FIG. In both heating elements C and D, the electrical resistance value changed greatly due to the load weight, and a stable electrical path was not formed.

(Effects of the invention) Due to its flexibility, such a heating element can be used in places where it is difficult to be rigid, where it is required to bend when pressed, where it is constantly moving, and where it can be used along uneven surfaces. Suitable for any place you want. In addition to the above-mentioned features, when a composite heating element is made, it has the following characteristics: it is soft to the touch, bulky, can be colored, and can be made into woven or knitted fabrics, which were difficult to achieve in the past.
100% clothing and interior items are also possible. For example, heaters that are used on the walls and floors of rooms to generate heat, heaters that warm toilet seats, heating furniture that covers the surface of a bed or chair and generates heat, and medical devices that are worn on a part of the body and heat locally. Its characteristics are demonstrated when used as base materials for various heating devices such as gloves, socks, belly wraps, vests, jackets, and pants-type clothing.

[Brief explanation of the drawing]

Fig. 1 is a diagram explaining the structure of the heating element, Fig. 2 is a diagram showing an example of the process for manufacturing the heating element of the present invention, and Fig. 3 is a diagram for manufacturing the heating element of another embodiment of the invention. FIG. 4 is a diagram showing the relationship between the voltage and current of the heating element according to the embodiment of the present invention, and FIG.
The figure is a diagram showing the relationship between voltage and surface temperature of a heating element according to an embodiment of the present invention. FIG. 6 is a diagram showing the relationship between load weight and electrical resistance value for a heating element according to an example of the present invention and a heating element according to a comparative example. D... Heating element, 1... Conductive fiber, 5
...Nonconductive fiber, A, B, C, D, H... Contact surface.

Claims (1)

[Claims] 1 A fiber bundle in which finite length discontinuous fibers having conductivity and finite length discontinuous fibers having no conductivity are drawn and mixed by a drafting method, and the average of the conductive discontinuous fibers is The fiber length is in the range of 100 to 800 mm, and the number of conductive discontinuous fibers in any cross section of the fiber bundle is on average 10 or more,
The fiber bundle is given convergence by air treatment, and the discontinuous fibers constituting the fiber bundle are mixed and intertwined, and the conductive discontinuous fibers stably maintain mutual contact points. A heating element characterized in that it is formed by forming a heating element.