JPH07118369B2 - Self temperature control heater - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a self-temperature controllable heater capable of adjusting output according to ambient temperature or heat radiation conditions.

[Problems to be Solved by Conventional Techniques and Inventions]

Generally, a heater that uses coil resistance of high resistance wire or weak resistance wire called nichrome wire continues to consume electric power corresponding to that voltage as long as the supplied voltage is constant.
A lot of energy is wasted. Furthermore, it is necessary to provide a temperature controller when it is necessary to maintain a constant temperature.

On the other hand, the self-temperature controllable heater uses a heating element having a PTC characteristic in which the resistance increases as the temperature of the heating element rises, and when the temperature reaches a preset temperature, the resistance of the heating element increases. However, it has a self-control function of limiting the output by itself and keeping a constant temperature.

The PTC characteristic is a positive temperature coefficient (positive thermistor), and as shown in FIG. 8, it means the function of a resistance element having a function of increasing the resistance as the temperature rises and gradually limiting the current. A heater having the resistance element as a heating element is a "self-temperature controllable heater".

Since the self-temperature controllable heater freely adjusts the output according to the ambient temperature or the heat radiation condition, the temperature is automatically adjusted even without the over-output prevention device. Therefore, the overlapping portion due to bending or the like, or the overlapping portion such as double winding or crossing of the tape-shaped heater is extremely convenient because the amount of heat generation is adjusted by the self-temperature control function.

The conventional self-temperature controllable heater uses a highly crystalline polymer compound as a base material and a resistor containing a large amount of conductive material such as carbon black, graphite or metal powder as a heating element, and the heating element is heated by the temperature rise. The current was controlled by the change in volume expansion and the rise and fall of the tunnel conduction effect of the conductive particles. The operating principle is as follows.

(A) At room temperature, electrons pass through the overlapping portions of the conductive particles dispersed in the polymer substrate due to the tunnel conduction effect to obtain conductivity.

(B) Since the polymer mixture that becomes conductive is a resistor, it generates heat when energized.

(C) When the temperature rises, the polymer base material expands and the overlapping conductive particles are separated from each other, so that the resistance gradually increases and the current stops flowing. When the electric current stops flowing, the temperature lowers, the polymer base material contracts, and the conductive particles approach each other, so that the electric current flows. A constant temperature is maintained by repeating this operation. That is, the heating element radiates a heat amount proportional to the temperature of the element itself, and reaches a parallel temperature at which the heat generation amount and the heat radiation amount are balanced.

In FIG. 10, a cross-sectional view of a conventional self-temperature controllable heater a is shown, and b is a heating element constructed by mixing carbon black, graphite or the like into a base material made of a polymer compound, c,
Reference numeral c is an electrode conductor integrally provided on both side edges of the heating element b, and d is an insulator covering them.

However, the above conventional self-temperature controllable heater has the following drawbacks.

(A) Since the structure of conductive carbon black is destroyed by shearing during processing, the resistance value is likely to change remarkably depending on processing conditions.

(B) Since graphite does not have a structure structure, it is less affected by processing. However, since graphite has larger particles than carbon black, there is a risk of causing electrical breakdown during energization.Furthermore, graphite has lower conductivity than carbon black, so it is necessary to mix in a large amount, so heat generation The body becomes hard and brittle, and is not suitable for applications requiring flexibility. Moreover, since it is brittle, it cannot be molded into a thin film.

(C) When the amount of the conductive substance mixed in increases, the difference in thermal expansion between the polymer base material and the conductive substance such as graphite increases, so that the gradient of the resistance value / temperature characteristic tends to decrease.
The self-temperature regulation function deteriorates.

(D) In the conventional product, a high temperature portion is likely to occur in the heating element b due to a local abnormally high heat when energized, and once the high temperature portion occurs, the high temperature portion spreads and spreads, and the temperature further rises. Finally, it reaches the melting point of the heating element or higher and causes a heat peak,
Accidents that burned out often occurred. It is considered that the cause of such localized high temperature portion is due to poor dispersion of the conductive material such as carbon black or graphite mixed in the polymer base material, that is, the imbalance of the local resistance of the heating element. It was difficult to completely disperse a conventional product in which a large amount of a conductive substance such as 50 to 100 parts by weight was mixed with 100 parts by weight of a polymer base material.

As shown in FIG. 9, when the high temperature part e is generated in a part of the heating element b, this heat peak is the current that should normally flow through the high temperature part e among the currents flowing between the electrode conductors c and c. ,
Since the high-temperature part e having a large resistance is bypassed to bypass the high-temperature part e, the current density around the high-temperature part e becomes high and the temperature rises sharply. In the figure, the portions of the parallel lines that are close to each other show such a bypass current. The frequency of occurrence of heat peaks increases as the distance between the electrodes c increases. That is, it is known that when the distance between the electrodes exceeds about 100 mm, a heat peak occurs in a short time after the start of energization. Therefore, in the past, the distance between the electrodes was
No self-temperature controllable heating element of 100 mm or more was obtained.

(E) Conventional self-temperature controllable heaters generally deteriorate rapidly with time and lack long-term stability. The cause is not clear, but it can be inferred as follows. That is, when a large amount of the conductive substance is mixed in, a spatial gap is generated due to poor dispersion of the conductive substance and imbalance in thermal expansion coefficient between the polymer base material and the conductive substance. Alternatively, it is conceivable that bubbles are generated due to moisture absorption or other chemical changes, and microscopic sparks are generated at the interface due to an increase in contact resistance to destroy the polymer composition or destroy the electrode.

As described above, since the distance between the electrodes cannot be increased, various inconveniences may occur during use. For example, when using it for freeze prevention of water pipes, etc., as shown in FIG. Furthermore, the self-temperature controllable heater a formed in a tape shape has to be wound in a spiral shape, which is very troublesome.

It is an object of the present invention to provide a self-temperature controllable heater that solves the above problems.

[Means for Solving the Problems]

In order to achieve the above-mentioned object, a base material composed of a polymer compound or a composite polymer compound such as plastic is added to 100 parts by weight of tetracyanoquinodimethane as an acceptor in a ratio of 2.5 to 10 parts by weight to the base material. A positive temperature which is obtained by dispersing and mixing 0 to 3 parts by weight of a nonionic active material or anionic active material as a donor, and adding 5 to 20 parts by weight of a conductive auxiliary agent such as carbon black. A heating element having coefficient characteristics is provided, and an electrode conductor is provided integrally with the heating element.

The heating element has a substantially circular cross section having a discontinuous portion at one location, and electrode conductors are provided integrally with the heating element on both side edges of the heating element.

Regarding the shape of the heating element, the heating element may be formed to have a rectangular cross section or an oblong shape, and the electrode conductors may be provided integrally with the heating element on both side edges of the heating element.

The heating element may be formed in a flat plate shape. In this case, the electrode conductors may be provided on both side edges of the heating element so as to be integrated with the heating element.

The heating element may be formed in a substantially circular cross section, and in this case,
One electrode conductor is provided on the central portion side in the cross section of the heating element, and the other electrode conductor is provided on the outer diameter side in the cross section of the heating element so as to be integrated with the heating element.

[Action]

Tetracyanoquinodimethane as an acceptor can generate holes and direct it to the PTC.
Donors generate free electrons or excite thermionic ions
Since (negative) type ion transmission is generated, the strength of PTC can be adjusted by adjusting the addition amount. That is, the equilibrium point between P (positive) and N (negative) at the set temperature is determined.

Further, carbon black or the like as an auxiliary agent can adjust the concentration of the conductive carrier. That is, the resistance value of the heating element can be adjusted by increasing or decreasing the amount of addition.

According to the self-temperature controllable heater of the second aspect, the entire shape is a tubular body having the fitting opening in the longitudinal direction. Therefore, if the fitting opening is expanded, this expansion is achieved. The heater can be attached to a water pipe or the like through the opened fitting opening, and the self-temperature controllable heater according to claim 3 can form a long strip. According to the self-temperature controllable heater of item 4, it can be made into a flat plate shape having a large area, and according to the self-temperature controllable heater of claim 5, it can be made into a wire / cable shape having a circular cross section. .

〔Example〕

An embodiment will be described with reference to the drawings. FIG. 1 shows a case where a self-temperature controllable heater 3 according to the present invention is formed in a substantially cylindrical shape, and 9 is a fitting provided in a longitudinal direction. It is an opening. Reference numeral 1 is a heating element, and the heating element 1 is formed in a substantially annular cross section having a discontinuous portion 2 at one location. 4, 4 are electrode conductors, and the electrode bodies 4, 4 are heating elements 1
Are provided integrally with the heating element 1 on both side edge portions 5, 5. The surface of the heating element 1 is covered with an insulator 7.

Thus, the heating element 1 is obtained by dispersing and mixing tetracyanoquinodimethane (hereinafter referred to as “TCNQ”) as an acceptor and a nonionic active material as a donor in a base material of a polymer compound such as plastic, and It is composed by adding a conductive auxiliary agent such as carbon black. The composition ratio is 100 parts by weight of the base material, the ratio of TCNQ is 3 parts by weight, and the ratio of the nonionic active material is 1 part by weight. The ratio of carbon black as a conductive additive is set to 8 parts by weight, and the ratio of graphite as a conductive additive is set to 8 parts by weight.

In the present invention, in order to increase the conductivity of the polymer compound, a method of increasing the mobility of conductive carriers is used, and TCNQ of an organometallic semiconductor is used as a charge transfer complex. Further, the polymer compound used as the base material is an insulator. The insulator is a dielectric, and when an electric field is applied to the insulator, it causes a polarization phenomenon and becomes a dielectric conductor. Furthermore, the ionic conductivity becomes dominant due to the activity of ionic impurities contained in the polymer. When the temperature rises, the activity of thermions becomes more active, and the resistance value gradually decreases, resulting in the so-called NTC (negative thermistor) phenomenon. Therefore, it is important to select a polymer compound having a low dipole efficiency as the base material.

Next, the experimental method and the result thereof will be described.

Experiment 1 The present invention was started when a PCN reaction as shown in FIG. 4 occurred when TCNQ was singly doped into a base material made of a polymer compound. TCNQ is a highly effective acceptor, and it is considered that holes were generated by doping this acceptor and exhibited PTC characteristics. Therefore, the experiment was started by first mixing TCNQ alone into the polymer base material, and adding 1 part by weight of TCNQ to 100 parts by weight of the polyolefin as the base material to prepare the heating element 1 for the experiment.
Then, the linear heater shown in FIG. 3 was prepared and used as sample 8. In FIG. 3, the heating element 1 is formed in a substantially circular cross section, and one electrode conductor 4 is provided on the center side (inner diameter side) in the cross section of the heating element 1 and the other electrode is formed. The conductor 4 is provided on the outer diameter side of the heating element 1 and integrated with the heating element 1. Reference numeral 7 is an insulator covering the outer peripheral surface of the electrode conductor 4 on the outer diameter side.

In the resistance test, the sample 8 is placed in a constant temperature bath and the change in resistance value (impedance) is measured while gradually raising the temperature from 20 ° C. As shown by the straight line A in Fig. 4, the resistance at 20 ° C is measured. The value was 7,000 KΩ.

Next, when the amount of TCNQ added was increased to 3 parts by weight,
As indicated by the straight line B in the figure, the resistance value at 20 ° C decreased to 2000 KΩ. However, in order for the heating element 1 of the sample 8 to function as a heater, the resistance value at 20 ° C. must be 100 KΩ or less. To do that, at least TCNQ
It becomes necessary to add 10 parts by weight. However, TCNQ is extremely expensive and costly, so it cannot be used in large quantities.

Experiment 2 After trial and error, such as using various active materials and conductive materials in combination with TCNQ, it was possible to break through the above wall by using the following ratios.

Base material (polyolefin) 100 parts by weight Acceptor (TCNQ) 3 parts by weight Donor (nonionic active material) 1 part by weight Conductive auxiliary material (carbon black) 8 parts by weight Conductive auxiliary material (graphite) ) ....... 8 parts by weight The heating element 1 having this blending ratio was formed into the linear heater shown in FIG. 3 in the same manner as in Experiment 1 to obtain a sample 8, and the resistance value due to the temperature change thereof was measured. As indicated by C in the figure, the resistance value at 20 ° C. was 20 KΩ.

The roles of various materials in this case are as follows.

TCNQ as an acceptor generates holes and directs them to PTC. The nonionic active material as a donor generates free electrons or excites thermal ions to generate N (negative) type ionic conduction.
Adjust the strength of the property. That is, as shown in FIG.
The equilibrium point of P (positive) and N (negative) is found at the desired set temperature T ° C. The conductive aids carbon black and graphite control the concentration of conductive carriers. That is,
The resistance value of the heating element 1 is adjusted by increasing or decreasing the addition amount. Importantly, even if 10 to 20 parts by weight of carbon black and graphite other than TCNQ is used, the conductivity that functions as a heating element cannot be obtained. By adding a very small amount of TCNQ as a nasal drug, the mobility of the conductive carrier is increased.

The composition ratio of each component of the heating element 1 is set as follows based on a large amount of experimental results thereafter. That is, 100
2.5 to 10 parts by weight of TCNQ, 0 to 3 parts by weight of nonionic activator as a donor, 5 to 20 parts by weight of carbon black as a conduction aid, and the same amount of conductivity aid per 100 parts by weight of the base material. Good results can be obtained even if graphite as an agent is set to 0 to 20 parts by weight and the amount is set within this range.

In the above experiment, a polyolefin-based polymer such as polyethylene or polypropylene was used as the base material, but other plastics, rubbers, or composite polymer compounds may be used. Although TCNQ was used as the acceptor and the nonionic active material was used as the donor in the charge transfer complex, it is also preferable to use the anionic active material instead of the nonionic active material. Regarding the conductive auxiliary agent that determines the concentration of the conductive carrier, it is desirable to use carbon black and graphite together, but carbon black alone may be used,
It is also preferable to use metal powder or the like instead of these.

The entire shape of the self-temperature controllable heater 3 according to the present invention is such that the fitting opening 9 is formed at one location in the circumferential direction as shown in FIG. It can be elastically attached to the pipe 10 such as a pipe with one touch to cover the outer peripheral portion, and can be removed with one touch. Regarding the overall shape, as shown in FIG. 5, it does not matter if it is formed into a substantially elliptical cross section. In this case, the heating element 1 is formed in a substantially elliptical cross section, and the electrode conductors 4,
4 are provided on both side edges 5, 5 of the heating element 1 integrally with the heating element 1. Of course, the heating element 1 may have another shape such as a rectangular cross section. Regarding the shape of the heating element 1,
As shown in the figure, a flat plate shape is also preferable. It should be noted that although not shown, a tape shape may be used.

Besides, for example, the shape shown in FIG. 3 used in the experiment may be formed.

The self-temperature controllable heater according to the present invention is used for industrial purposes such as heat retention or antifreezing of pipes and tanks, heating or heat retention of equipment, nursery beds, heat retention of livestock, agricultural greenhouses such as fermentation and brewing, and loading. It can be used for heat transfer such as heating, for household use such as antifreezing of water pipes and drainage pipes, floor heating, hot carpets, foot heaters, anchors, toilet bowls, and pets.

〔The invention's effect〕

Since the present invention is configured as described above, it has the effects described below.

Since TCNQ which is an organometallic charge transfer complex is used as the conductive carrier, the incorporation of carbon black or the like as an auxiliary agent achieves the functional purpose with a small amount (for example, 10 to 20 parts by weight). Therefore, since the heating element does not become hard and does not become brittle, the thickness (wall thickness) of this heater can be made relatively thin.

Since the amount of the conductive substance added is small, it is not adversely affected by the difference in thermal expansion between the base material and the conductive substance. Therefore, long-term stability can be expected.

Since the amount of the conductive substance added is small, there is no fear of microscopic spark generation at the interface, and long-term stability can be expected.

Since the amount of the conductive substance added is small and the charge transfer complex having a metallic property for electron transfer is used, there is no fear of heat peak due to poor dispersion as in the conventional case.

Particularly, according to the self-temperature controllable heater of the second aspect, it is possible to easily fit on the pipe such as a water pipe through the fitting opening 9 in the longitudinal direction, and the pipe covering work is extremely easy. Is.

Particularly, according to the self-temperature controllable heater of the third aspect, the entire shape is a rectangular cross section or a long ellipse shape, and the whole shape conventionally used is a rectangular cross section or a long ellipse shape. It has a wide range of uses.

Particularly, according to the self-temperature controllable heater of the fourth aspect, it is possible to form a wide heater having a distance between electrodes of more than 100 mm, and there is no fear of heat peak due to poor dispersion. High temperature part does not occur.

In particular, according to the self-temperature controllable heater of the fifth aspect, the entire shape is a circular cross section, and the heater that has been conventionally used is a circular cross section, which is versatile.

[Brief description of drawings]

FIG. 1 is an enlarged cross-sectional perspective view of an embodiment of a self-temperature controllable heater according to the present invention, FIG. 2 is an explanatory view of a method of use, FIG. 3 is an enlarged cross-sectional view of another embodiment, and FIG. FIG. 5 is a characteristic diagram showing experimental results, FIG. 5 is an enlarged transverse sectional view showing a modified example, FIG. 6 is an enlarged perspective view showing another embodiment, and FIG. 7 is an explanatory diagram for setting an equilibrium point of PTC strength. . FIG. 8 is a PTC characteristic diagram, FIG. 9 is an explanatory diagram showing a heat peak occurrence state, FIG. 10 is an enlarged cross-sectional view showing a conventional example, and FIG. 11 is a usage explanatory diagram. 1 ... Heating element, 2 ... Discontinuous portion, 4 ... Electrode conductor, 5 ...
… Side edges.

Claims (5)

[Claims] 1. A base material made of a polymer compound or a composite polymer compound such as plastic, and 100 parts by weight of tetracyanoquinodimethane as an acceptor in a ratio of 2.5 to 10 parts by weight to the base material is dispersed and mixed. And 0 to 3 parts by weight of a nonionic active material or anionic active material as a donor are dispersed and mixed, and 5 to 20 parts by weight of a conductive auxiliary agent such as carbon black is added to have a positive temperature coefficient characteristic. A self-temperature controllable heater comprising a heating element (1) and electrode conductors (4, 4) integrally provided with the heating element (1). 2. A heating element (1) is formed in a substantially circular cross section having a discontinuous portion (2) at one location, and electrode conductors (4, 4) are provided on both side edge portions (5, 5) of the heating element (1). The self-temperature controllable heater according to claim 1, wherein the self-temperature controllable heater is integrally formed with the heater and has an overall shape of a tubular body having a fitting opening 9 in the longitudinal direction. 3. A heating element 1 is formed in a rectangular or oblong cross section, and electrode conductors 4, 4 are provided on both side edges 5, 5 of the heating element 1 integrally with the heating element 1. The self-temperature controllable heater according to claim 1. 4. The heating element 1 is formed in a flat plate shape, and the electrode conductors 4, 4 are provided on both side edge portions 5, 5 of the heating element 1 integrally with the heating element 1. Self-temperature controllable heater. 5. The heating element 1 is formed in a substantially circular cross section, and one electrode conductor 4 is provided on the center side in the cross section of the heating element 1 while the other electrode conductor 4 is provided in the heating element 1. The self-temperature controllable heater according to claim 1, wherein the heater is integrated with the heating element 1 by being provided on the outer diameter side of the cross section of the heater.