JPH0722159A - Panel heater with ptc - Google Patents

Abstract

PURPOSE:To provide an RTC panel heater which presents a large steady output by using an extra heat radiating plate having large wall thickness besides the outside heat radiating plate, mounting an RTC thermistor thereunder, and thereby decreasing the rush current under the high voltage operation. CONSTITUTION:An outside heat radiating plate 5, an insulative sheet 6, and another heat radiating plate 7 having a larger wall thickness than the plate 5 are laminated, and thereto an RTC ceramic element 1 is attached, and a panel heater is assembled which is equipped in the under-part with a heat insulative material 8. In this manner, the structure includes extra heat radiating plate 7 having a large wall thickness while the distance between two electrodes 2a, 2b is specifically related to the voltage impressed, and thereby the rush current is greatly decreased under a high voltage condition, in particular when 200V is used, using an extraordinarily simple means, which should achieve an RTC panel heater capable of emitting a large steady output. The ceramic element 1 with electrodes 2a, 2b should preferably be arranged so that the condition V/d<=57 is met, where (d) represents the shortest distance between the two electrodes while V does the impressed voltage used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a PTC panel heater whose resistance value rapidly increases at a specific temperature, and particularly to reduce the inrush current when used under a high voltage and to produce a high output. The present invention relates to a PTC panel heater having a simple structure capable of performing.

[0002]

2. Description of the Related Art Conventionally, a means for utilizing a PTC element as a heat source has been often considered. As a PTC thermistor device of this type, for example, in Japanese Utility Model Application Laid-Open No. 55-136193, as shown in FIG. The surface temperature can be increased by forming the film directly on the heat sink. Further, in Japanese Utility Model Laid-Open No. 58-60903 and Japanese Utility Model Laid-Open No. 55-105904, as shown in FIG. 18, heat is radiated from the entire element surface between the electrodes 2 and 2 of the PTC element 1. To improve efficiency.

Further, in Japanese Utility Model Application Laid-Open No. 56-89188, as shown in FIG. 19, a pair of electrodes 2 and 2 are provided on the surface of one element 1 and an intermediate electrode is provided on the other surface to form an insulating adhesive. The rated output was increased by the method of joining with a chemical. In the figure, 3 is an insulating plate and 4 is an electrode plate.

On the other hand, a problem when using the PTC element is inrush current. In order to solve this problem, JP-A-55-97143 discloses that a PTC thermistor is connected in series with a negative characteristic thermistor. Japanese Patent Laid-Open No. 54-115445 describes joining an ohmic electrode and a non-ohmic electrode.
JP-A-49-27932 describes combining positive temperature coefficient thermistors having different Curie points. Further, JP-A-63-218184 describes the use of a phase temperature control device.

However, such a conventional technique has a problem that the circuit becomes complicated and the number of steps is increased. Particularly, in the case of the one disclosed in Japanese Patent Laid-Open No. 49-27932, when it is used for a panel heater or the like, there is a drawback that temperature variation occurs.

Further, the conditions examined by these solutions are all cases where a voltage of 100 V or less is applied,
In the 200V use environment, which tends to increase in the future,
It was a difficult method to deal with.

[0007]

Therefore, the problem to be solved by the present invention is to anticipate a future use environment,
Especially when using 200v, the inrush current can be greatly reduced by a very simple means and a large steady output can be obtained.
It is to provide a TC panel heater.

[0008]

The inventors of the present invention have conducted many trials and experiments in order to solve the above problems, and as a result, have adopted a structure in which a thick heat dissipation plate is combined, and the distance between different electrodes and the applied voltage. It has been found that it is possible to reduce the inrush current, especially under the conditions related to

That is, when the applied voltage used is V and the distance between different electrodes is d, the range of V / d ≦ 57 is satisfied. Furthermore, the insulating heat dissipation plate made of ceramics with high thermal conductivity and the PTC ceramics element are
It is characterized in that the effect can be enhanced by interposing electrodes and integrating them or by dividing them into one surface and providing counter electrodes.

As the ceramics having a high thermal conductivity, which compose the insulating heat dissipation plate, Al ₂ O ₃ , MgO, B are used.
60 mol% of one or more of N, AlN and SiC
The thing containing above can be used conveniently.

[0011]

When a PTC ceramic element with a distance between different electrodes is energized under a certain voltage, heating is promoted first from the central portion where heat dissipation is small. When the temperature of the PTC ceramics rises, the resistance value increases, so that the voltage is concentrated and the heating is further accelerated. Therefore, when the applied voltage is constant, the thinner the element thickness of the PTC ceramics is and the smaller the distance between the electrodes is, the more the time for reaching the maximum current is likely to be concentrated, and the maximum current is likely to be a large value.

When a voltage is usually applied to PTC ceramics, a current of I _max flows in a short time at the beginning of energization as shown in FIG. 3, and the current decreases with the lapse of time and settles at I _min . Although this characteristic can speed up the temperature rising characteristic, when a large total output is required for a panel heater or the like, the output and the number of installed sheets are limited. Therefore, it is considered desirable that I _max / I _min take a value of 1 or more.

[0013]

EXAMPLES The present invention will be specifically described below with reference to examples.

Example 1 2.5 × 3.5 × 4.5 × 5.5 × 5.5 × 5.5 × 15 × 25 mm having a Curie point of 110 ° C.
After applying Al paste to 5 types of PTC ceramic elements with different thickness and specific resistance of 7.5 mm, and drying, 65
By baking at 0 ° C. × 15 min, electrodes 2a and 2b as shown in FIG. 1 were formed. The resistance value of the PTC ceramic element 1 at 25 ° C. is 8 KΩ.

Further, as shown in FIG. 2, 240 mm square ×
1 mm thick Al plate 5, 100 mm square x 0.4 mm thick S
The PTC ceramics element 1 was attached to a laminate of an i insulating sheet 6 and an Al plate 7 of 90 mm square and 4 mm thickness, and a panel heater was attached with a rigid polyurethane foam heat insulating material 8 at the bottom. Furthermore, the electrodes 2 on both ends of the PTC ceramic element 1 in this panel heater are
A voltage of 200 V was applied to a and 2b, and time-current characteristics were measured. The results are shown in Table 1.

[0016]

[Table 1] As can be seen from Table 1, the distance between the electrodes 2a and 2b is 3.
When it is 5 mm, I _min / I _max is 0.80. That is, this is the result of the 200v experiment,
It can be seen that when the applied voltage / distance between electrodes is 5.7 or less, 20% current limiting is sufficient. Similar results were obtained at 100 v, and 20% of current limiting result was obtained at 1.8 mm.

[Embodiment 2] A PTC ceramic element of 15 × 25 × 2.5 mm having a Curie point of 110 ° C.
l paste was applied on both sides, and before drying, it was pressed against the alumina substrate 3 as shown in FIG. 4 and dried at the same time. After drying, it was baked at 650 ° C. for 15 minutes to obtain a heater unit having electrodes 2a and 2b as shown in FIG. The resistance value of the element at 25 ° C. was 8 KΩ. Further, as shown in FIG. 5, 240 mm square × 1 mm thick Al
The PTC ceramics element 1 was attached to a laminate of the plate 7 and an Al plate 5 of 90 mm square and 4 mm thickness, and a panel heater having a heat insulating material 8 of rigid polyurethane foam attached to the lower part was assembled. Furthermore, P in this panel heater
A voltage of 200 V was applied to the electrodes 2a and 2b of the TC ceramics element 1 and the time-current characteristics were measured. The results are shown in Table 3.

In the case of the second embodiment, I _min / I _max was 0.73, which was a slightly large value, because the insulating plate and the PTC thermistor were bonded via the electrode layer. .

Example 3 A PTC ceramic of 15 × 25 × 2.5 mm having a Curie point of 110 ° C. and an interelectrode distance (d) of 10 mm was coated with an Al paste in a shape as shown in FIG. After drying, 650 ℃ × 15min
And the electrodes 2a and 2c, 2 shown in FIG.
d was formed. In addition, 25 of PTC ceramics element 1
The resistance value at ° C was 7 KΩ. Further, as shown in FIG. 7, 240 mm square × 1 mm thick Al plate 5, 100 m
The PTC ceramics element 1 was attached to a laminate of an m-square × 0.4-mm-thick Si insulating sheet 6 and a 90 mm-square × 4-mm-thick Al plate 7, and a heat insulating material 8 of rigid polyurethane foam was attached to the lower part. The panel heater was assembled. Further, a voltage of 200 v was applied to the electrodes 2c and 2d of the PTC ceramics element 1 in this panel heater, and the time-current characteristics were measured.

In the case of Example 3, I _min / I _max was 0.98, which was a large value even though a high voltage of 200 v was applied. The steady-state current value also increased to 63 mA.

Example 4 An Al paste was applied to both sides of a PTC ceramic of 15 × 25 × 2.5 mm having a Curie point of 110 ° C., and the paste was dried before being dried as shown in FIGS.
As shown in (perspective view), the alumina substrate was pressed and simultaneously dried. After drying, baking was performed at 650 ° C. for 15 minutes to obtain a heater unit having a common electrode 2a as shown in FIGS. Further, as shown in FIG.
Assembling a panel heater in which the PTC ceramics element 1 is attached to a laminate of an 0 mm square × 1 mm thick Al plate 5 and a 90 mm square × 4 mm thick Al plate 7, and a rigid polyurethane foam heat insulating material 8 is attached to the lower part. It was The results are shown in Table 3.

In the case of Example 4, I _min / I _max is 1.0.
It was 0, and the steady-state current value was as large as 65 mA.

[Embodiment 5] As shown in FIG. 11, under the same conditions as in Embodiment 1, 240 mm square × 1 mm thick Al plates 5 and 1 are used.
An experiment was conducted under the same conditions as the heat dissipation plate in which the Si insulating sheets 6 of 00 mm square and 0.4 mm thickness were laminated. Table 2 shows a summary of the results.

[0024]

[Table 2] As can be seen from Table 2, compared to the results in Table 1, I _min
The value of / I _max is 0.80 when the distance between the electrodes is 5.5 mm. From this, it can be seen that the structure of the heat sink greatly affects the characteristics. Also, when the thickness of the PTC thermistor becomes thicker by about 5.5 mm, when a high voltage is applied, a temperature difference between the inside and the outside occurs, and cracks easily occur at the time of power input.
It was also confirmed that the life of the C thermistor was significantly reduced.

Comparative Example 1 As shown in FIG. 12, the same as Example 5 except that the heat dissipation plate was an Al plate 5 of 250 mm square × 1 mm thick. The results are shown in Table 3.

Comparative Example 2 As shown in FIG. 13, the same as Example 5 except that the heat dissipation plate was an Al plate 5 of 250 mm square × 4 mm thick.

Table 3 shows the results of the above Examples 2 and 4 and Comparative Examples 1 and 2.

[0028]

[Table 3] As can be seen from Table 3, the conventional electrode structure (both sides of the entire surface) as in Example 2 has a large inrush current and a small output in a steady state. Further, even in the case where the pair of electrodes was provided on the surface, the same results as in Example 2 were obtained as in Comparative Example 1. On the other hand, in Comparative Example 2, the inrush current was small (I _max was a steady current and I _min was an initial current), and the steady current was also a large value, and I _min / I _max was a good value of 0.96. .

However, the temperature rise near the surface takes 1.8 times as long as in Example 4, and the weight of the whole is large, which causes a problem of cost increase.

From the above results, the heat dissipation plate in which the external heat dissipation plate and the heat dissipation plate thicker than that are combined satisfies V (working applied voltage) / d (distance between electrodes) ≦ 57, and the maximum surface of the PTC thermistor. An element in which an electrode is formed so as to face with. Alternatively, an element in which one surface of a PTC thermistor is divided to provide a pair of counter electrodes.

By combining the above, it has become possible to provide a panel heater which suppresses an inrush current while securing a large output. In addition, these characteristics
Further improvement can be achieved by integrating the insulating film and the electrode film interposed between the heat sink and the PTC thermistor.

For the above-mentioned element, a PTC thermistor having electrodes having the structure shown in FIG. 6 was used.
Depending on the peripheral configuration, electrodes having the configurations shown in FIGS. 14 and 15 may be used, or the same effect can be obtained by using a cylindrical element as shown in FIG.

Although alumina is used for the insulating plate in the embodiment, it is not limited to this, but Mg0, BN, Al may be used.
Any material such as N, SiC having a high electrical resistivity and a high thermal conductivity may be used.

[0034]

As described above, according to the present invention,
Since the rush current is extremely small, the number of sheets can be set according to the steady output of the panel heater and other heat generating devices, and it becomes possible to heat a larger area than in the past, and the effect is extremely large.

[Brief description of drawings]

FIG. 1 is a perspective view of a PTC thermistor according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of a panel heater incorporating the PTC thermistor of the first embodiment.

FIG. 3 is a time-current characteristic diagram of a PTC thermistor.

FIG. 4 is a sectional view of a PTC thermistor according to a second embodiment of the present invention.

FIG. 5 is a sectional view of a panel heater incorporating a PTC thermistor of a second embodiment.

FIG. 6 is a perspective view of a PTC thermistor according to a third embodiment of the present invention.

FIG. 7 is a sectional view of a panel heater incorporating a PTC thermistor of a third embodiment.

FIG. 8 is a sectional view of a PTC thermistor according to a fourth embodiment of the present invention.

FIG. 9 is a perspective view of a fourth embodiment.

FIG. 10 is a sectional view of a panel heater incorporating a PTC thermistor of a fourth embodiment.

FIG. 11 is a sectional view of a panel heater incorporating a PTC thermistor of a fifth embodiment of the present invention.

12 is a sectional view of a panel heater incorporating a PTC thermistor of Comparative Example 1. FIG.

13 is a sectional view of a panel heater incorporating a PTC thermistor of Comparative Example 2. FIG.

FIG. 14 is a perspective view of another embodiment of the present invention.

FIG. 15 is a perspective view of another embodiment of the present invention.

FIG. 16 is a perspective view of another embodiment of the present invention.

FIG. 17 is a sectional view of a conventional example.

FIG. 18 is a perspective view of another conventional example.

FIG. 19 is a cross-sectional view of another conventional example.

[Explanation of symbols]

1 PTC thermistor, 2, 2a, 2b, 2c, 2d
Electrode film, 3 insulating plate, 4 electrode plate, 5 aluminum plate (4 mm thickness), 6 silicon sheet plate, 7 aluminum plate (1 mm thickness), 8 heat insulating material

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuo Ariki 2-20-31 Shimizu, Minami-ku, Fukuoka-shi, Fukuoka Japan Tungsten Co., Ltd.

Claims (4)

[Claims] 1. A panel heater using PTC, wherein an external heat dissipation plate and a heat dissipation plate thicker than the heat dissipation plate are combined, and a PTC thermistor is attached to the lower part thereof. 2. When the shortest distance between a pair of electrodes formed on the maximum surface of the PTC thermistor is d (mm) and the applied voltage used is V (v), V / d ≦ 57 (v / mm) is satisfied. The panel heater using the PTC according to claim 1, wherein the shortest distance d between the electrodes is such that the range is satisfied. 3. The panel heater using PTC according to claim 1, wherein the electrodes of the PTC thermistor are a pair of counter electrodes having one surface divided. 4. The panel heater using PTC according to claim 2, wherein the PTC thermistor and ceramics having high thermal conductivity are integrated via an electrode layer.