JP2981296B2 - Temperature control method of PTC heating element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a PT used mainly for floor heating devices such as electric carpets and electric floor heaters.
The present invention relates to a method for controlling the temperature of a C heating element.

[0002]

2. Description of the Related Art Conventionally, a self-heating type heating element comprising a pair of electrodes sandwiching a material having a large positive temperature coefficient of resistance has been used as a heating element of an electric carpet or an electric floor heater. In this heating element, uniform heat is generated as a whole by a current flowing between the pair of electrodes through a material having a positive and large temperature coefficient of resistance (hereinafter abbreviated as a PTC material). The control temperature of such a heating element is determined by the balance between the amount of heat generated by the current flowing through the PTC material and the amount of heat radiation from that portion.
At this time, for example, if a locally insulated portion occurs, the temperature of the portion increases, and the resistance value of the PTC material increases, so that the amount of heat output from the portion rapidly decreases, and the amount of heat generated by the heating element in the insulated portion decreases. It is self-controlled to a temperature where the amount of heat radiation is balanced. Therefore, even if a local heat-insulating portion occurs, the temperature does not become abnormally high, and portions other than the local heat-insulating portion are not affected by the heat-insulating portion at all.

[0003]

However, the control temperature of such a heating element is determined by the balance between the amount of heat generated by the current flowing through the PTC material and the amount of heat radiated from the portion. The control temperature fluctuates. In other words, in such a heating element, the higher the temperature, the larger the resistance value and the lower the heating value. Therefore, the lower the temperature of the heating element, the larger the heating value. Therefore, when the room temperature decreases, the amount of heat radiation from the heating element increases. In order to generate a calorific value that balances the amount of heat radiation, the temperature of the heating element necessarily drops.
Therefore, the self-control temperature of the heating element decreases as the room temperature decreases, and the self-control temperature increases as the room temperature increases.

The temperature resistance characteristic of the heating element that determines the self-control temperature of such a heating element is relatively unstable, and tends to vary at the time of manufacture or when the entire heating element is thermally insulated. Since the control temperature is always higher than the state where the heat insulation is not performed, if the heating element is left in such a state for a long time, the resistance temperature characteristic changes relatively quickly. If the direction of change is a change in the direction in which the resistance value increases, the self-control temperature changes low. If the change direction changes in a direction in which the resistance value decreases, the self-control temperature changes high, which is particularly dangerous. .

In such a heating element, PT
In order to make the voltage applied to the C material as uniform as possible in the length direction, the resistance value of the conductor electrode is made as small as possible. Even if the electrode is disconnected, the power supply voltage is applied almost uniformly between the plurality of electrodes.If the power supply is a 100 V commercial power supply, the disconnected end touches the counter electrode for some reason, There was a problem that there was a possibility that an arc was generated and the fire was caused, which was dangerous.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and an object of the present invention is to detect a temperature-voltage characteristic generated between both ends of an electrode constituting a heating element to thereby detect the heating element. By performing the temperature control of 1. 1. The temperature of the heating element can be controlled to a constant temperature without being affected by the external environment. 2. Even if the temperature resistance characteristic of the heating element slightly changes due to manufacturing variations, aging, etc., it can be controlled with a constant amount of generated electric power. 3. Can detect short-circuit and disconnection abnormality of the heating element. An object of the present invention is to provide a method of controlling the temperature of a PTC heating element that can control the temperature of the heating element to an arbitrary temperature.

[0007]

In order to achieve the above object, the present invention provides a heating element comprising a plurality of conductors arranged as electrodes facing each other, and a material having a positive temperature coefficient of resistance sandwiched between the electrodes. When a voltage is applied between the electrodes, a voltage generated at both ends of the electrodes is detected, and the supply of power is controlled so that the voltage having a temperature-voltage characteristic depending on temperature becomes a predetermined value. It is characterized in that the temperature is controlled to a constant temperature without being affected by an external temperature. In a temperature control method using the temperature-voltage characteristics of the electrodes of the PTC heating element, the temperature of the heating element is controlled to an arbitrary temperature. Also, PTC
In the temperature control method using the temperature-voltage characteristics of the electrodes of the heating element, a disconnection and a short-circuit failure of the electrodes of the heating element are detected, and the operation is stopped.
Further, in the temperature control method utilizing the temperature-voltage characteristics of the electrodes of the PTC heating element, the electrode resistance value Re of the heating element and the resistance value Rptc of the positive material between the electrodes are determined based on the lowest temperature at which the heating element is used. Sometimes Rptc / Re ratio is about 1/3
It is configured to be larger, to reliably detect disconnection and short circuit failure of the electrode, and to stop the operation.

[0008]

According to the above construction, in the present invention, the temperature of the heating element is controlled by detecting the temperature-voltage characteristics generated at both ends of the plurality of conductor electrodes opposed to each other via the PTC material. Any temperature can be controlled regardless of the self-control temperature. Further, disconnection and short-circuit abnormality of the electrode can be detected.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIGS. 8A to 8C show a schematic configuration of a heating element according to the present invention. In the figure, a heating element has a structure in which a space between a plurality of opposed electrodes 1 is filled with a PTC material 2 and the periphery thereof is covered with an insulating material 3. And
When a constant voltage is applied between these electrodes 1, the PTC
An electric current flows through the material 2 to generate heat. PT
As the temperature of the C material 2 increases, the resistance value of the PTC material 2 gradually increases, and conversely, the current decreases. Eventually, the temperature becomes stable at a temperature at which the heat generation amount and the heat radiation amount of the PTC material 2 become the same. This stable temperature is governed by the positive temperature resistance characteristic and the heat radiation characteristic of the PTC material 2.

FIG. 9 shows a method for connecting a heating element H according to the present invention to a commercial power supply E. When the terminals of a pair of electrodes 1 at one end of the heating element H are A and B, and the terminals of the electrode 1 corresponding to A and B at the other end of the heating element H are C and D, respectively, the terminals A and D are respectively By connecting to the commercial power source E, a voltage as uniform as possible can be applied to the PTC material 2 between the pair of electrodes 1 over the length direction of the heating element H.

FIG. 10 shows the temperature resistance characteristics of the resistance value (hereinafter abbreviated as Rptc) of the PTC material 2 between the pair of electrodes 1 when the length of the heating element H is 20 m. I have. This is a characteristic having a positive temperature resistance coefficient in which the resistance value increases as the temperature increases. In particular, the characteristic has a characteristic that the positive temperature resistance coefficient increases as the temperature increases.

FIG. 11 shows the temperature resistance characteristic of the electrode resistance value (hereinafter abbreviated as Re) of the pair of electrodes 1 when the length of the heating element H is 20 m. Since the electrode of the present embodiment is made of a copper alloy, unlike the characteristic of the resistance value Rptc of the PTC material 2, the resistance value changes little with temperature.

FIG. 12 shows an equivalent circuit when the heating element H shown in FIG. 9 is divided into n elements in the length direction. Re in the figure is the electrode resistance value of the electrode 1 of the heating element H,
Rptc is a resistance value of the PTC material 2 between the pair of electrodes 1.

FIG. 13 shows the temperature resistance characteristics of the resistance value Rptc of the PTC material 2 between the pair of electrodes 1 when the length of the heating element H shown in FIG. 10 is 20 m and FIG. The resistance-temperature characteristic between the terminals A and D of the heating element H obtained by substituting the temperature resistance characteristic of the electrode resistance value Re of the electrode 1 into the equivalent circuit of the heating element H shown in FIG. Is shown. Since the resistance value between the terminal A and the terminal D is a combined resistance value of Rptc and Re having a positive temperature resistance value characteristic, the resistance value always has a positive temperature resistance value characteristic. The resistance value between the terminal A and the terminal D is strongly affected by Rptc, which has a large change in resistance value due to temperature, and has a resistance-temperature characteristic that is relatively gentle near low temperatures and sharply increases near high temperatures. ing.

FIG. 14 shows a case where the terminals A and D of the heating element H shown in FIG. 9 are respectively connected to a commercial power supply E. The power supply voltage is 100 V, and the length of the heating element H is about 20 m. FIG. 14 is a diagram showing the relationship between the amount of heat generated by the heating element H and the temperature obtained by calculation using the temperature resistance characteristic between the terminals A and D of the heating element H shown in FIG. As described above, the amount of heat generated by the heating element H connected to the commercial power supply E decreases substantially uniformly as the temperature of the heating element H increases.

FIG. 15 shows a case where the terminals A and D of the heating element H shown in FIG. 9 are respectively connected to a commercial power supply E. The power supply voltage is 100 V, and the length of the heating element H is about 20 m. Between the two ends of the electrode 1 of the heating element H (between the terminals B and D)
Shows the relationship between the voltage (hereinafter, abbreviated as electrode voltage Vre) generated in the heating element H and the temperature of the heating element H. Similar to the above, the characteristics of the resistance element Rptc shown in FIG. 10 and the electrode resistance value Re shown in FIG. 11 are shown in the equivalent circuit of the heating element H shown in FIG. Is substituted, and a temperature-voltage characteristic generated between the terminal B and the terminal D when 100 V is applied between the terminal A and the terminal D is obtained by calculation. According to this characteristic, since the temperature of the heating element H and the electrode voltage Vre have a certain fixed relationship, the temperature characteristic of the electrode voltage Vre is detected and controlled to a certain value, so that the temperature of the heating element H is fixed to a certain value. It can be controlled to the value of.

FIG. 16 shows the relationship between the amount of heat generated by the heating element H and the temperature shown in FIG. 14 and the relationship between the electrode voltage Vre of the heating element H and the temperature shown in FIG. The relationship between the amount and the electrode voltage Vre is shown. According to this characteristic, the amount of heat generated by the heating element H and the electrode voltage Vre have a certain relationship. It should be noted here that the relationship between the amount of heat generated and the electrode voltage Vre is independent of the temperature of the heating element H. That is, by detecting the temperature characteristic of the electrode voltage Vre and controlling it to a certain value, the amount of heat generated by the heating element H can be controlled to a certain value. This means that the temperature resistance of the resistance between the terminals A and D of the heating element H shown in FIG.
Even if the PTC material 2 slightly changes due to aging or the like, the amount of heat generated by the heating element H can be controlled to a certain value regardless of the change.

[0018] In the above table, when the terminals A and D of the electrode 1 are connected to the commercial power source E in the heating element H shown in FIG. 9 to generate heat, the heating element length is 20 m, the commercial voltage is 100 V, and the heating element temperature is shown. At 60 ° C., when the pair of electrodes 1 is short-circuited at the center in the longitudinal direction of the heating element H, or when the electrode 1 is disconnected at the same part, the terminals B and the terminals at both ends of the electrode 1 of the heating element H D, the value of the electrode voltage Vre generated during the heating element H shown in FIG.
The value calculated using the equivalent circuit of FIG. When the electrode 1 is short-circuited or disconnected, the value of the electrode voltage Vre is considerably larger than in the case where it is not. Therefore, by detecting that the electrode voltage Vre has increased beyond a certain value, a short-circuit disconnection failure of the electrode 1 can be found.

FIG. 17 is a perspective view of an electric carpet using such a heating element H as a heat source. The heating elements H are wired at regular intervals so that the surface temperature of the electric carpet becomes uniform. Both ends of the heating element H are connected to the controller Ct.
At t, a power cord W for obtaining commercial power is provided.

FIG. 18 is a sectional view of the electric carpet shown in FIG. The heating element H is fixed to a uniform aluminum plate S made of aluminum foil having a thickness of about 9 μm with a wiring interval of about 40 mm to form a planar heating element. Further, a top cloth F and a back cloth R made of polyester fibers are adhered to the upper and lower surfaces of the sheet heating element, respectively, to form an electric carpet.

FIG. 1 is a block circuit diagram showing an embodiment of a method for controlling the temperature of a PTC heating element according to the first aspect of the present invention. A terminal A at one end and a terminal D at the other end of the heating element H are connected to a commercial power supply E via a power switch SW and a switch element Ry of a relay. Electrode 1 of heating element H
During this time, a commercial voltage is applied and a current flows through the PTC material 2 to generate Joule heat. At this time, a voltage is generated between both ends of the electrode 1 (terminal B-terminal C) according to the current flowing through the PTC material 2. The B terminal of the electrode 1 is connected to a rectifying / smoothing circuit 4 for rectifying and smoothing the AC voltage generated at the B terminal of the electrode 1 to DC, and is input to one input terminal of the comparator 5 as a temperature signal. I have.

The comparator 5 receives the DC voltage generated by the DC power supply circuit 6 and supplies it to the reference voltage circuit 7, and the reference voltage having a constant value is input to the other input terminal. The output of the comparator 5 is connected to a relay drive circuit 8, and when the temperature signal input to the comparator 5 falls below the reference voltage, drives the relay and turns off the switch element Ry of the relay. I am trying to do it. However, with such a circuit configuration alone, once the switch element Ry
Once the F is applied, the voltage generated at the end B of the electrode 1 of the heating element H is always 0, and the temperature signal of the comparator 5 is always lower than the reference voltage to be compared, so that the relay is permanently ON. No longer. Therefore, an OFF time timer circuit 9 is provided for forcibly turning on the relay once a predetermined time has elapsed after the output of the comparator 5 is detected and the relay is turned off. Therefore, the temperature of the heating element can be controlled to be constant without being affected by the outside.

FIG. 2 is a block circuit diagram showing an embodiment of a method for controlling the temperature of a PTC heating element according to the second aspect of the present invention. In the temperature control circuit of the PTC heating element shown in FIG. 1, the reference voltage that can be generated in the reference voltage circuit 7 is always a constant value. However, the temperature of the heating element H is
Since the reference voltage can be changed by changing the reference voltage, by providing a variable voltage circuit 10 that can generate an arbitrary voltage instead of the reference voltage circuit 7, the voltage generated by the variable voltage circuit 10 can be changed to generate heat. The body temperature can be controlled arbitrarily.

FIG. 3 is a diagram showing a case where a disconnection occurs at a point Oa Xm from the terminal A of the electrode 1a of the heating element H (length 20 m). The heating element H has two conductor electrodes 1a and 1b, and since the electrode 1a and the electrode 1b are the same, the temperature characteristics of the electrode resistance value Re are as shown in FIG. Also, the PTC material 2 between the electrode 1a and the electrode 1b
FIG. 10 shows the temperature resistance characteristic of the resistance value Rptc of FIG. The terminal A of the electrode 1a at one end of the heating element H and the terminal D of the electrode 1b at the other end are connected to 100 V of the commercial power supply E, respectively. When the temperature range in which the heating element H is normally used is set to 0 to 70 ° C., the terminal A, which is both terminals of the electrode 1a, is used.
It can be seen from FIG. 15 that the voltage generated between the terminal C and the terminal C and between the terminal B and the terminal D, which are both terminals of the electrode 1b, is 9 to 37V. Electrode 1b corresponding to Oa point of electrode 1a
Is defined as Ob. In terms of potential, the portion from the Oa point of the electrode 1a to the terminal C is only connected to the portion from the Ob point of the electrode 1b to the terminal D via the PTC material 2 facing the portion. About ２ of the voltage generated between the Ob point of the electrode 1b and the terminal D is induced in the portion from the Oa point of 1a to the terminal C.

Assuming that the potential of the terminal A of the heating element H is 100 V and the potential of the terminal D is 0 V, a maximum voltage of 37 V is generated between the terminal B and the terminal D in a normally used temperature zone. At this time, it is assumed that a disconnection has occurred in the electrode 1a and the terminal B
It is assumed that the voltage between the terminal D and the terminal D does not change from 37 V (actually, it always decreases in accordance with the position of the disconnection).
/2=18.5V only. Therefore, the voltage between the terminals A and C at both ends of the electrode 1a where the disconnection has occurred is 100-18.5V = 81.5V. Terminals A and C at both ends of electrode 1a when heating element H is normal
Is 9 to 37 V, it can be said that when the voltage between both terminals of the electrode 1 becomes 81.5 V or more, disconnection occurs in the electrode 1 a. When the disconnection occurs in the electrode 1b, the voltage between both terminals of the electrode 1b is set to 8 based on the same principle as described above.
It becomes 1.5V or more.

FIG. 4 shows a configuration similar to that of the heating element H shown in FIG.
FIG. 2A shows a diagram in which the electrode 1a and the electrode 1b are short-circuited.
In this case, most of the current flowing between the terminals A and D is
The electrode 1a from the terminal A to the short-circuit point Oa and the O of the electrode 1a
The current flows through the circuit composed of the electrode 1b from the point Ob on the electrode 1b corresponding to the point a to the terminal D. Here, since the electrode 1a and the electrode 1b have the same electrode resistance value Re, the length Lm of the heating element H and the short-circuit occurrence point Oa
Assuming that the length is Xm, the voltage Va-oa generated between the terminal A of the electrode 1a and the short-circuit occurrence point Oa is expressed by the following equation. Va-oa = (X / L) 100 [V] Since almost no current flows from the short-circuit occurrence point Oa to the terminal C, the voltage Va-oa generated between the terminal A and the short-circuit occurrence point Oa and the terminal A The voltage substantially coincides with the voltage between terminals C. Similarly, the terminal D of the electrode 1b and the short-circuit occurrence point Ob
Is generated by the following equation. Vob-d = ((L−X) / L) 100 [V] In the same manner as above, the voltage Vob-d generated between the terminal D and the short-circuit occurrence point 0b and the voltage between the terminal B and the terminal D Almost match. Here, considering the case of 0 <X <(1/2) L, it can be said that Va-oa <50 [V] Vob-d> 50 [V] from the formula and the formula. Or, similarly, when (1/2) L <X <L, it can be said that Va-oa> 50 [V] Vob-d <50 [V]. That is, in the heating element H, the electrode 1
a and the electrode 1b are short-circuited, one of the voltages across the electrode 1a must be 50V
That is all. To summarize the above, if it is detected that at least one of the voltage between the terminals A and C and the voltage between the terminals B and D of the heating element H has become 50 V or more, the heating element H Electrodes 1a and 1b generated on
Disconnection and short-circuit failure can be detected.

FIG. 5 is a block circuit diagram showing an embodiment of a method for controlling the temperature of a PTC heating element according to claim 3 of the present invention. The basic circuit block for controlling the temperature of the heating element H is the same as that shown in FIG. 2, and therefore the description thereof is omitted, and the basic principle of a circuit for detecting disconnection and short circuit of the electrode of the newly provided heating element H is described. Will be described. Heating element H
Are a pair of electrodes 1a and 1b, one terminal of the electrode 1a is A, the other terminal is C, one terminal of the electrode 1b is B, and the other terminal is D. Both ends of the electrode 1a of the heating element H are connected to a high voltage detection circuit 11a for detecting a voltage of 50 V or more, and both ends of the electrode 1b of the heating element H are similarly connected to a high voltage detection circuit 1 for detecting a voltage of 50 V or more.
1b. High voltage detection circuits 11a and 11
The output of b is input to the OR circuit 12. The output of the OR circuit 12 is input to the relay drive circuit 8, and if at least one of the two high voltage detection circuits 11a and 11b outputs an output, the output is input to the relay drive circuit 8. The operation is stopped by turning off the switch element Ry of the relay.

FIG. 6 shows a voltage Vre across the electrode 1 and a PTC material between the electrodes of the heating element H generated when a commercial voltage of 100 V is applied to the terminal A and the terminal D is grounded in the equivalent circuit of the heating element H shown in FIG. Ratio of resistance value and electrode resistance value Rptc / R
This shows the relationship with e. In the configuration shown in FIG. 5, when the voltage generated at the electrode 1a or the electrode 1b of the heating element H is 50 V or more, it is determined that either the disconnection or the short circuit has occurred at the electrodes 1a and 1b of the heating element H. Judge and stop the operation. However, when the ratio Rptc / Re between the inter-electrode PTC material resistance value and the electrode resistance value is smaller than 1/3, a voltage of 50 V or more is generated at the electrodes 1a and 1b. Even if the disconnection or short-circuit failure of 1b does not occur, the operation is mistakenly stopped. Therefore, in order to accurately detect the disconnection or short-circuit failure of the electrodes 1a and 1b in the configuration shown in FIG. 5, the resistance value of the inter-electrode PTC material and the electrode resistance value at the lowest temperature at which the heating element H is normally used. The ratio Rptc / Re is 1
It needs to be greater than / 3.

FIG. 7 shows the rate of change of the resistance value at a heating element temperature of 60.degree. C. when the heating element H is left in an atmosphere of 70.degree. The rate is shown by the solid line b. The rate of change of the heating element H left in an atmosphere of about 7200H and 70 ° C. is + 48%, which is large, whereas the rate of change of the heating element H left in an atmosphere of 60 ° C. is + 10%. Is small.

[0030]

As described above, according to the present invention, in a heating element in which a plurality of conductors are opposed to each other as electrodes and a material having a positive temperature coefficient of resistance is sandwiched between the electrodes, a voltage is applied between the electrodes. The temperature of the heating element is controlled by detecting a temperature-voltage characteristic generated at both ends of the electrode when the voltage is applied. The temperature of the heating element can be controlled to be constant without being affected by the external temperature. 2. The temperature of the heating element can be changed to any temperature according to the user's preference. 3. The operation can be stopped by detecting disconnection and short-circuit failure of the heating element. 4. Even when the temperature resistance value characteristics vary when the heating element is manufactured, or when the characteristics change due to aging or the like, the amount of heat generated can be controlled to be constant. 5. Even when the heating element is insulated, the temperature does not reach a certain temperature or higher, so that deterioration of the temperature resistance characteristic due to aging of the heating element can be reduced.

[Brief description of the drawings]

FIG. 1 is a block circuit diagram of an embodiment of a method for controlling a temperature of a PTC heating element.

FIG. 2 is a block circuit diagram of an embodiment of a method of controlling a temperature of a PTC heating element.

FIG. 3 is a diagram showing a case where disconnection occurs at a point Xm from an electrode terminal of a heating element.

FIG. 4 is a diagram illustrating a case where a short circuit occurs at a point Xm from an electrode terminal of a heating element.

FIG. 5 is a block circuit diagram of an embodiment of a temperature control method of a PTC heating element.

FIG. 6 is a diagram showing a relationship between a voltage between both ends of an electrode and a ratio between a PTC material resistance value between electrodes and an electrode resistance value.

FIG. 7 is a diagram showing a rate of change in resistance when a heating element is left in each atmosphere.

8 (a) to 8 (c) are schematic structural views of a heating element according to the present invention.

FIG. 9 is an explanatory diagram when the heating element according to the present invention is connected to a commercial power supply.

FIG. 10 is a diagram showing a temperature resistance characteristic of a resistance value of a PTC material between a pair of electrodes of a heating element.

FIG. 11 is a diagram showing temperature resistance characteristics of electrode resistance values of a pair of electrodes of a heating element.

FIG. 12 is a diagram showing an equivalent circuit when a heating element is divided into n elements in a length direction.

FIG. 13 is a diagram showing a temperature characteristic of a resistance value between a terminal A and a terminal D of a heating element.

FIG. 14 is a diagram showing the relationship between the amount of heat generated by a heating element and temperature.

FIG. 15 is a diagram showing a relationship between a voltage generated at both ends of an electrode of the heating element and a temperature of the heating element.

FIG. 16 is a diagram showing the relationship between the amount of heat generated by the heating element and the electrode voltage.

FIG. 17 is a perspective view of an electric carpet using a PTC heating element.

FIG. 18 is a cross-sectional configuration diagram of an electric carpet.

[Explanation of symbols]

 Reference Signs List 1 electrode 1a electrode 1b electrode 2 PTC material 3 insulating material 4 rectifying / smoothing circuit 5 comparator 6 DC power supply circuit 7 reference voltage circuit 8 relay drive circuit 9 OFF time timer circuit 10 variable voltage circuit 11a high voltage detection circuit 11b high voltage detection circuit 12 OR circuit A terminal B terminal C terminal Ct controller D terminal E Commercial power supply F Front cloth H Heating element R Back cloth Re Electrode resistance Rptc PTC material resistance Ry Switch element Vre Electrode voltage S Uniform aluminum plane SW SW power switch W Power cord

Claims (4)

(57) [Claims] 1. A heating element in which a plurality of conductors are opposed to each other as electrodes, and a material having a positive temperature coefficient of resistance is sandwiched between the electrodes. By detecting the generated voltage and controlling the power supply so that the voltage having the temperature-voltage characteristic depending on the temperature becomes a predetermined value, the temperature of the heating element can be kept at a constant temperature without being affected by the external temperature. A method for controlling the temperature of a PTC heating element, comprising: 2. A temperature control method using a temperature-voltage characteristic of an electrode of a PTC heating element according to claim 1, wherein the temperature of the heating element is controlled to an arbitrary temperature. Control method. 3. The temperature control method using the temperature-voltage characteristics of the electrodes of the PTC heating element according to claim 2, wherein the disconnection and short-circuit failure of the electrodes of the heating element are detected and the operation is stopped. A method for controlling the temperature of a PTC heating element, characterized in that: 4. A temperature control method using temperature-voltage characteristics of electrodes of a PTC heating element according to claim 3, wherein an electrode resistance value Re of the heating element and a resistance value Rptc of a positive material between the electrodes are determined. At the lowest temperature at which
The ptc / Re ratio is configured to be larger than approximately 1/3,
A method for controlling the temperature of a PTC heating element, wherein the operation is stopped by reliably detecting disconnection and short-circuit failure of an electrode.