JPH0425679B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to the structure of a flexible heating wire used in heating appliances and the like.

Conventional configuration and its problems Conventional heating wire with positive temperature coefficient of resistance (hereinafter referred to as
The PTC heating line (referred to as PTC heating line) was constructed as shown in FIG. 1, for example. In Fig. 1, 3 is a PTC heating layer, and a pair of parallel electrodes 2,
2' is wound spirally on the core yarns 1 and 1', and its outer surface is tubed with an insulator 4. In this configuration, it is possible to set a certain self-control temperature using the PTC curve of the PTC heating layer 3, but if the distance between the electrodes 2 and 2' becomes locally small due to external pressure, bending, twisting, etc.
If a conductive substance is mistakenly mixed into a part of the heating layer 3, the resistance value of the entire PTC heating wire will hardly change, and the current will concentrate in that part, causing local heating.
Arcing and furthermore, shoots occur between the electrodes 2 and 2', resulting in burns, flames, and other safety hazards. Regarding the short between electrodes 2 and 2', PTC
Since there is a large change in the current value flowing through the entire heating wire, it is possible to easily stop the energization using a current fuse, etc., although it is dangerous, but as mentioned above,
The resistance value of the entire PTC heating wire remains almost unchanged,
Even if the resistance value changes, it is still within the self-control resistance range of the PTC heating wire itself, and safety cannot be ensured if the current is concentrated locally.

Purpose of the invention The present invention solves the above-mentioned conventional problems.
The aim is to provide safe and reliable products.

Structure of the Invention In order to achieve the above object, the present invention provides a PTC heating layer between a pair of electrodes, and also arranges another conductor separately provided on at least one of the electrodes via a heat-melting electrical insulating layer. However, when the temperature of the PTC heating layer abnormally increases, the heat-melting electric insulating layer is melted to short-circuit the electrode and the conductor, thereby detecting an abnormality.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

As shown in FIG. 2, an electrode 2 and a conductor 6 are wound spirally on separately provided core threads 1 and 1', and on the conductor 6 is a thermofusible electrical insulating layer 5 made of nylon 12. is provided covering it. After providing an electrode 2' that pairs with the electrode 2 on top of it, a PTC heat generating layer 3 is covered as shown in FIG.
Then a jacket 4 is applied. In addition, in FIG. 3, the conductor 6 is coated with a heat-fusible electrical insulating layer 5, and this and one electrode 2' are twisted wires, and the other electrode 2' is a stranded wire.
At the same time, a PTC heat generating layer 3 and a jacket 4 are sequentially formed in the form of a parallel cable. When the temperature of the PTC heating layer 3 rises abnormally, the heat-fusible electrical insulating layer 5 melts, causing a short circuit between the electrode 2' and the conductor 6, and detecting the abnormal temperature rise. Suitable materials for the heat-melting electrical insulating layer 5 include crystalline thermoplastic polymers such as polyamide, polyester, polyolefin, and polyurethane. Polymer is 150-200
It has a melting point at °C and a low melt viscosity, making it ideal.

With the above configuration, sufficient safety can be ensured even against localized abnormal overheating. That is,
The distance between the electrodes 2 and 2' or the conductor 6 may become locally small due to external pressure, bending, twisting, etc., or the conductive material in the PTC heat generating layer 3 may be mixed in, or the electrode If the wire itself is broken or almost broken, or if the PTC heating layer is heated due to an external factor, this will lead to melting of the heat-melting electrical insulation layer 5, causing contact between the electrode 2' and the conductor 6, and causing an abnormality. It has the excellent feature of being able to prevent overheating and local overheating. Note that as shown in FIGS. 2 and 3, one electrode 2'
In addition to providing a conductor 6 coated with a heat-fusible electrical insulating layer 5, both electrodes 2, 2' may be provided with a conductor coated with a heat-fusible electrical insulating layer. Also
The PTC heating layer 3 is a polymer composition containing a particulate conductive agent mainly composed of carbon black.
For example, the resin used for this is polyethylene.
There are crystalline resins such as vinyl acetate copolymer, polyethylene-ethyl acrylate copolymer, polyolefin such as polyethylene and polypropylene, polyamide, polyvinylidene halide, and polyester, each of which has a sharp positive temperature coefficient near its crystal transformation point. shows. Also, the distance between the pair of electrodes 2 and 2' is 0.3~
The PTC heating layer 3 may be made of a composition having a high specific resistance, and PTC characteristics for self-temperature control can be easily obtained.

Effects of the Invention As described above, according to the present invention, the following effects can be obtained.

The distance between the electrodes may become locally small due to external pressure, bending, twisting, etc., a conductive substance may be mixed into the PTC heating layer, the electrodes themselves may be disconnected or almost disconnected, or even abnormalities may occur due to external factors. Local overheating, abnormal overheating, and overheating caused by arcing can be suppressed to below the thermal melting temperature, thereby improving safety.

[Brief explanation of drawings]

FIG. 1 is a front view showing a conventional structure, and a and b in FIGS. 2 and 3 are a front view and a side view, respectively, showing the structure of an embodiment of the present invention. 1, 1'... Core thread, 2, 2'... Electrode, 3...
PTC heating layer, 5...thermofusible electric insulating layer, 6...
…conductor.

Claims (1)

[Claims] 1. A positive temperature coefficient of resistance (hereinafter referred to as
In addition to providing a PTC heat generating layer having a PTC heat generating layer (abbreviated as PTC), another conductor separately provided on at least one of the electrodes via a heat-fusible electrical insulating layer is provided, so that when abnormal temperature rise of the PTC heat generating layer occurs, a PTC heat generating layer is provided. The flexible heating wire is configured such that when an abnormality is detected by melting the heat-melting electric insulating layer to short-circuit the electrode and the conductor. 2. The flexible heating wire according to claim 1, wherein the heat-melting electric insulating layer has a tubular shape, and a conductor is arranged on the inside and an electrode is arranged on the outside. 3. The flexible heating wire according to claim 1 or 2, wherein one of the pair of electrodes and another separately provided conductor are spirally wound around separate core threads. 4. The flexible heating wire according to claim 1, wherein the heat-melting electrical insulating layer is made of polyamide resin. 5. The flexible heating wire according to claim 1, wherein the PTC heating layer is made of a carbon-containing polyoffine polymer.