JP2000188172A - Planar heating element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a planar heating element capable of accurately performing normal temperature control and local abnormal heat generation. SOLUTION: In this planar hating element that generates heat by forming a film-like resistance-heating element 2 on one side of an insulating base material 1 and by carrying a current to it, a conductive film 6 having a positive resistance temperature coefficient is formed on the other side of the insulating base material 1, the detection of abnormal local heat generation of the resistance-heating element 2 is carried out by the use of the conductive film 6, and the temperature control of the resistance-heating element 2 is carried out by a temperature sensing element 7 other than the conductive film 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a planar heating element for heating a large area such as an electric carpet for home use and business use, floor heating, and the like.

[0002]

2. Description of the Related Art Conventionally, as a planar heating element used in an electric heating apparatus such as a carpet, a linear heating element such as a nichrome wire heater is mainly used as a heating heater. In the temperature detection using a linear heater, a method of winding a nickel wire or the like around the heater wire via an insulating coating is mainly used.

[0003] In addition, if the insulating coating between the heater wire and the inspection wire is made of a material that can be melted at a certain temperature, if abnormal heat generation occurs, the insulating coating is locally melted and the heater wire is detected. A system that detects the short circuit of the heat wire and cuts off the current is adopted.

In recent years, a sheet-like heating element in which an insulating base material is coated or printed with a silver-based or carbon-based resistance heating element has been developed. In these heating elements, a method of arranging a thermistor on the heater surface at various places to detect the temperature is used.

[0005]

In order to heat a large area uniformly, it is preferable to use a sheet heating element instead of a linear heating element such as a cord heater. However, a thermistor is used as a method for detecting the temperature of the sheet heating element. In order to detect the temperature of a wide area, a number of thermistors must be arranged and wired in various places. In addition, when abnormal heat is locally generated in a place where there is no thermistor, it cannot be detected.

For this purpose, it is conceivable to perform temperature detection and abnormal heat detection of the sheet heating element using one conductive film having a positive characteristic. However, in order to provide two functions with one conductive film. Has a problem that the TCR (temperature coefficient of resistance) of the conductive film must be switched according to the temperature, so that the resistance stability of the film is slightly unstable.

An object of the present invention is to provide a heating element capable of performing each detection more easily and accurately by detecting temperature detection for normal temperature control and abnormal heat generation detection using different detection means. Aim.

[0008]

According to the present invention, there is provided a thin film planar heating element (film heating element) in which an insulating substrate such as a PET (polyethylene terephthalate) film is coated or printed with a resistance heating element. Thermistors are installed at multiple locations to detect temperature for temperature control. Normally, the temperature of the sheet heating element does not greatly differ depending on the location. However, if heat radiation is deteriorated by placing an object on the upper surface of the sheet heating element, the temperature locally increases. Therefore, by providing a conductive film or a nickel wire having a positive resistance temperature characteristic so as to cover the entire heating element, the abnormal local temperature rise can be detected and fed back to the circuit.

By using a conductive film having a positive resistance temperature characteristic instead of the thermistor, a thinner heating element can be obtained.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a sectional view of a main part showing the configuration of the present embodiment. In FIG. 1, an insulating substrate 1 such as a pet film is screen-printed with a conductive paste on one side to form a resistance heating element 2, and electrodes are formed of silver paste or the like having a lower resistance value than the resistance heating element 2. The portions are printed to form auxiliary electrodes 3 and 3, and copper foils 4 and 4 with a conductive adhesive are adhered thereon as electrodes. The resistance heating element 2 is made of a material having little positive resistance-temperature characteristic, and can withstand long-term use even when a predetermined power supply voltage is applied.

On the back surface of the insulating base material 1, the resistance heating element 2
The conductive film 6 is formed in a size that covers the area. The conductive film 6 is formed by dispersing a conductive filler such as carbon black in a polyester resin, and exhibits a positive resistance-temperature characteristic in which the resistance value increases as the temperature increases. FIG. 3 shows the resistance temperature characteristics of the conductive film 6. When a high voltage such as a voltage applied to the resistance heating element 2 is applied to the conductive film 6, the conductive film 6 may be degraded in a long-term use. If it is, it will withstand long-term use with almost no deterioration.

Similarly to the resistance heating element 2, copper foils 4 and 4 are attached to the conductive film 6 by electrodes, and the resistance heating element 2 and the conductive film 6 are protected by a laminate film 5, respectively. ing. The thermistor 7 is provided on the laminate film 5 on the conductive film 6 side.

The resistance heating element 2 and the conductive film 6 are electrodes 4
Is connected to the controller 8 through the
Are also connected to the controller 8 to supply necessary voltages.

When it is desired to set the temperature of the resistance heating element 2 to the temperature T0, the power supply to the resistance heating element 2 is controlled by setting the indicated temperature of the thermistor 7 to T0, and the temperature of the heating element is maintained near T0. Is done. However, if thermistor 7
If the temperature rises locally (for example, 60 ° C. or more) due to factors such as poor heat radiation in a portion where no thermistor 7 is present,
However, the controller 8 detects an increase in the resistance of the conductive film 6 covering most of the heating element 2, detects an abnormality based on the increase in the resistance, and stops the energization. By doing so, local heat generation can be prevented.

That is, by using the thermistor 7 for normal temperature control and the conductive film 6 for local heat detection separately, it is possible to accurately and reliably perform temperature control and local abnormal heat detection. .

Next, a second embodiment will be described. As a temperature detecting means for controlling the temperature of the planar heating element 2 similar to that of the first embodiment, a nickel wire having a positive resistance temperature characteristic was uniformly wired on the insulating base 1 instead of the conductive film 6. Since it is not possible to cover the entire surface as in the first embodiment, it is not possible to cope with the prevention of local temperature overheating of a small area. Can respond.

Next, a third embodiment will be described. In the configuration of FIG. 1, a conductive film having a positive resistance-temperature characteristic is used as a temperature sensor for temperature control instead of the thermistor 7. As a result, the same effect as in the first embodiment could be obtained. The conductive film has different characteristics from the conductive film 6. When the conductive film 6 also serves as the thermistor 7, the operation becomes slightly unstable, but since the applied voltage is low, it can withstand long-term use.

A fourth embodiment will be described. Third
In the embodiment, a nickel wire is used as a temperature sensor for detecting abnormal heat generation instead of the conductive film 6. In this case, the same effect as in the first embodiment was obtained.

[0019]

According to the present invention, in a planar heating element,
To detect and prevent abnormal local heat generation in a large area efficiently with a thin structure by detecting temperature for normal temperature control with a thermistor and detecting abnormal heat generation using a conductive film. As a result, it is possible to reduce damage to the heating element and eliminate the risk of low-temperature burns.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a sheet heating element according to an embodiment of the present invention.

FIG. 2 is a schematic view of a back surface of the sheet heating element of FIG. 1;

FIG. 3 shows resistance-temperature characteristics of a conductive film for temperature detection.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulating base material 2 Resistance heating element 3 Auxiliary electrode 4 Metal foil electrode tape with conductive adhesive 5 Laminating film for overcoat 6 Conductive film for temperature detection 7 Thermistor 8 Temperature controller

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takashi Inoue 22-22, Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside (72) Inventor Takeshi Furukawa 22-22, Nagaikecho, Abeno-ku, Osaka-shi, Osaka F term in reference (reference) 3K058 AA13 BA02 CA23 CA58 CA62 CE13 CE19

Claims (2)

[Claims] 1. A sheet-like heating element which is provided with a film-like resistance heating element on one of the insulating base materials and generates heat by energizing the film-forming resistance heating element. A film is provided with a width substantially covering the resistance heating element, and abnormal local heat generation of the resistance heating element is detected by the conductive film, and the temperature control of the resistance heating element is performed at a different temperature from the conductive film. A planar heating element characterized in that it is performed by a sensing element. 2. The planar heating element according to claim 1, wherein a conductive film having a positive resistance temperature characteristic different from that of the conductive film is used as the temperature detecting element.