JPS61190886A - Thermosensitive planar heat generating body - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technology) The present invention relates to an improvement of a planar heating element equipped with a thermistor 8i used in wide-area heating devices such as electric carpets and Ti thermal sheets. ″ ・(Background technology) A film-shaped @thermal surface heating element is produced by drawing a heating line and a temperature detection line with resist ink on a metal foil such as aluminum with a thickness of about 20 microns attached to an insulating film, and then etching it. After forming the circuit, a thermosensitive resin film made of an ion-conductive plastic thermistor material made by adding an ion-conductive additive such as Kl (potassium iodide) to a resin such as nylon 12, which has low hygroscopicity, is laminated.
It is made by pasting another insulating film on top of it, which simplifies the manufacturing process.

■Even if the impedance of the thermosensitive resin film suddenly decreases at high temperatures, the thermosensitive resin hardly generates heat.

■Sensor function is maintained normally even if there is a conductive foreign substance in the thermosensitive resin.

Although it has been proposed in the past for the following reasons, it has not yet been put into practical use.

The reason for this is that the detection accuracy of the temperature-impedance characteristic of the thermosensitive resin film varies greatly depending on the atmospheric conditions used, especially the humidity. In other words, the causes are as follows: ■ The gap between the heating line of the heat-sensitive sheet heating element and the temperature detection line is usually about 1W, the thickness of the heat-sensitive resin film is about 50 microns, and the thickness of the insulating film is about 0.2 m. Become a fine structure.

■The B constant (thermistor constant) of a thermosensitive resin film that can be practically designed to have a large value is due to the fact that electron conductive materials have not yet been developed. Therefore, alternating current must be used for the applied voltage to extract the temperature detection signal in order to prevent polarization from occurring.

These problems are related to each other, and especially when the insulating film is used in an atmosphere where the surface is humid, electrodes are formed on the outer surface of the insulating film due to moisture, which generates capacitance and makes it difficult to accurately measure the temperature. It becomes impossible to detect.

Figure 4 schematically shows the above situation.
2 is a heating line and a temperature detection line formed on an insulating film 4, 3 is a thermosensitive resin film, 5 is an insulating film, A
C is an AC constant voltage source, and Zo is an impedance element for voltage detection, that is, between the heat generation line 1 and the temperature detection line 2! ! 21 For detection, an AC constant voltage source AC is connected via an impedance element Z0, and a signal voltage v0 corresponding to the change in impedance of the thermosensitive resin film 3 due to temperature is obtained from both ends of the impedance element Z0. . However, the original current path is a in the figure.
When water droplets W adhere to the surface of the insulating film 5, the conductivity of the surface of the insulating film 5 increases and acts like an electrode, and since the applied voltage is AC, the capacitor capacity increases. As a result, current also flows through the path b in the figure.

Figure 5 shows the relationship between the temperature of the heat-sensitive sheet heating element and the impedance in a 100Hz AC signal.
A indicates the value when dry, and B indicates the value in an atmosphere with a humidity of 90%. However, when the impedance decreases due to moisture, the temperature control circuit (not shown) determines that the temperature has increased, so it operates in the same way as when the temperature is high, even if the temperature has not actually increased, and generates heat. There were inconveniences such as stopping the power supply to the line and as a result, the temperature did not rise.

(Object of the Invention) The present invention has been proposed in view of the above points, and its object is to provide a heat-sensitive sheet heating element that is not affected by humidity atmospheric conditions.

(Disclosure of the Invention) The present invention will be described in detail below with reference to the drawings showing embodiments. Although we will explain a type of heat-sensitive sheet heating element in which the heat generation line also serves as one temperature detection line, it can be similarly applied to a type that has two temperature detection lines independent of the generator #1lIsIs. Needless to say.

FIG. 1 is a cross-sectional view of a heat-sensitive sheet heating element showing one embodiment of the present invention, and also schematically shows the configuration for temperature detection. In the figure, reference numerals 1 and 2 are a heat generation line and a temperature detection line made of metal foil formed on an insulating film 4 by etching or the like. Then, a thermosensitive resin film 3 such as a plastic thermistor is attached so as to be in contact with these, and another insulating film 5 is attached to the upper surface thereof. Furthermore, a conductive guard electrode 6 such as a metal foil is provided on the surface of the insulating film 5.

On the other hand, as for the electrical configuration for temperature detection, an alternating current constant voltage source AC as a sensor application power source is connected between the heat generation line 1 and the temperature detection line 2 via an impedance element z0, and a guard A voltage source 11i6 is connected to one end of an alternating current constant voltage source AC. In addition, in the case where there are two temperature detection lines in addition to the heat generation line, numbers 1 and 2 in the figure are the respective temperature detection lines.

Therefore, when the guard electrode 6 is left open, the fourth
Similar to the case where water droplets W adhere in the conventional configuration shown in the figure,
Fever! 1IIN! 11 and the temperature sensing wire 2 due to the capacitance of the capacitor, but in the present invention, the guard electrode 6 is connected to one end of the AC constant voltage source AC, and the temperature sensing wire 2 is connected to the guard electrode 6. Since f is set to have the same potential, no current flows between the guard electrode 6 and the temperature sensor 1i12, and only a current C flows between the guard electrode 6 and the heating line 1. That is, from the AC constant voltage source AC, the sum of the current C flowing due to the capacitor capacitance between the guard electrode 6 and the heat generating line 1, and the current a flowing between the temperature detection line 2 and the heat generating line S 1 following the temperature change. However, the original temperature detection current a flows through the impedance element Z0.
Therefore, the voltage signal v0 generated across the impedance element z0 is not affected by the surface condition of the insulating film 5.

FIG. 2 shows another embodiment of the present invention, in which instead of inserting an impedance element and extracting the temperature detection signal, a current transformer CT for sensor current detection is provided in the path of the current a, and the current transformer CT is installed in the path of the current a. I am trying to extract a proportional signal. Note that the other configurations are the same as in FIG. 1.

FIG. 3 shows the impedance characteristics of the planar heating element having the configuration shown in FIG. 1 or 2, and there is no □ change at all between the dry state and the moist state. Note that on the low temperature side, the absolute value of impedance is larger than the conventional one, but this is due to the fact that with the conventional configuration, the surface current of the insulating film was added to some extent even when measured under dry conditions. Because it's gone.

In addition, although the above-mentioned example showed the case where the guard electrode was provided on the outer surface of one of the insulating films, the guard electrodes may be provided on both sides of the insulating film in order to obtain a more complete effect. Moreover, there is no problem in providing another insulating film on the outside of the guard electrode, if necessary.

Furthermore, as the material for the guard electrode, metal foil is preferable from the viewpoint of conductivity, but if flexibility is a priority, it is also possible to use conductive plastic, non-woven fabric mixed with metal fibers, etc. be.

(Effects of the Invention) As described above, in the present invention, the heat generation line and the temperature detection line made of metal foil are wired almost in parallel on the same semi-solid surface, and the 41 heat generation circuits and the temperature detection line are wired in parallel. In a heat-sensitive sheet heating element formed by providing a heat-sensitive resin film with negative characteristics so as to be in contact with both sides and pasting an insulating film on both sides, a conductive guard electrode such as a metal foil is provided on at least one outer surface of the insulating film. The temperature detection signal is obtained by short-circuiting this guard electrode and one end of the sensor application power supply and detecting the sensor current flowing between the short-circuited side of the guard electrode and the sensor application power supply and one temperature detection line. (a) When used in electric carpets, etc., the set temperature will not drop in a high humidity atmosphere, making practical use possible.
Becomes Noh.

(Stomach) The manufacturing process is simpler than conventional heat-sensitive sheet heating elements.

(c) Even if the user accidentally spills water on the electric carpet, electricity is maintained, which speeds up the drying speed.

(d) Since the value of the sensor current is sufficiently smaller than that of conventional heat-sensitive sheet heating elements, the heat-sensitive resin itself generates almost no heat even if a localized high temperature occurs.

(e) Sensor short circuit will not occur even if conductive foreign matter gets mixed into the thermosensitive resin film.

(f) Even if the insulating film itself undergoes thermal deterioration, the sensor characteristics will not exceed the above.

(g) When the guard electrode is made of metal foil, a uniform heat-uniforming effect is produced to equalize heat generation.

(H) When the guard electrode is made of a moisture-permeable conductive plastic material or the like, a drop in impedance due to moisture absorption of the heat-sensitive resin material is almost no problem because the drying speed due to energization becomes faster.

There are other effects.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional configuration diagram showing one embodiment of the heat-sensitive sheet heating element of the present invention, FIG. 2 is a cross-sectional configuration diagram showing another embodiment, and FIG. 3 is a temperature diagram of the heat-sensitive sheet heating element of the present invention. - Impedance characteristic diagram, FIG. 4 is a schematic explanatory diagram of a conventional heat-sensitive sheet heating element and temperature detection, and FIG. 5 is a temperature-impedance characteristic diagram of the conventional heat-sensitive sheet heating element. 1... Heat generation line, 2... Temperature detection line,
3...fi M resin film, 4,5...
...Insulating film, 6-゛...Guard electrode, A
C: AC constant voltage source, ZO: impedance element, CT: laminar flow device for sensor current detection, W: water droplet, etc. Figure 4 Figure 5 Proceedings LE (spontaneous) April 9, 1985 1, Indication of the case 1985 Patent Application No. 29455 2, Name of the invention Heat-sensitive sheet heating element 3, Amendments made Relationship with the patent applicant name +583) Matsushita Electric Works Co., Ltd. 4, Agent
Person: 160 Address: 7F, 2nd Mizota Building, 7-5-10 Nishi-Shinjuku, Shinjuku-ku, Tokyo

Claims (1)

[Claims] A heating line and a temperature sensing line made of metal foil are wired almost in parallel on the same plane, a thermosensitive resin film with a negative characteristic is provided so as to be in contact with both the heating line and the temperature sensing line, and an insulating film is applied from both sides of the heating line. In the heat-sensitive sheet heating element, a conductive guard electrode such as metal foil is provided on the outer surface of at least one of the insulating films, and this guard electrode and one end of the sensor applied power source are short-circuited, and the guard electrode and the sensor A heat-sensitive sheet heating element characterized in that a temperature detection signal is obtained by detecting a sensor current flowing between a short-circuited side with an applied power source and one temperature detection line.