JPH0445352A - Warm air producing heater - Google Patents

Abstract

PURPOSE:To permit a high temperature warm air to be produced with a small rush current and improved thermal impact resistance by a method wherein heat radiation fins are provided on the electrodes holding therebetween an electrically conductive ceramic plate consisting mainly of SiC, voltage is applied across the electrodes and an air flow is supplied to the heat radiation fins to obtain warm air. CONSTITUTION:When DC electric source 4 is connected with current supply terminals 3c and 3d, a current flows through a ceramic plate 1 to heat it and the resulting heat is radiated from metal heat radiation structures 3a and 3b. Therefore, when this heater is fitted into a fan case 7 and an air flow is supplied by a motor fan consisting of a motor 5 and a fan 6 in the direction of the arrow A, the air is heated by heat radiation fins 3a and 3b and released in the direction of the arrow B. Moreover, since the ceramic plate 1 is small in variability of resistance value against temperature, a rush current is small at the start of current application. Also, since the heat conductivity is high and thermal expansion coefficient is low, the ceramic plate 1 is high in thermal impact resistance and excellent in heat conductivity to the heat radiation fins.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial Application Field The present invention relates to heaters for generating hot air mainly used in electrical appliances and the like.

(b) Conventional technology Conventionally, heaters for home hot air heating, FM, utensils, clothes dryers, etc. are plate-shaped PTC semiconductor heaters using barium titanate-based ceramics with metal radiator (aluminum fin) terminals. It is known that plates are bonded together (for example, Japanese Patent Publication No. 56-160786, Japanese Patent Publication No. 57-63).
790, Japanese Patent Publication No. 61-107682, and Japanese Patent Publication No. 58-42192).

(c) Problems to be Solved by the Invention However, conventional PTC (positive characteristic) heaters have a temperature above the Curie point due to their material properties, and this gives the heater an advantage of having a self-temperature control function. Furthermore, PTC heaters have the drawbacks of being unable to raise the temperature (not being able to generate high-temperature hot air) and having to flow a large current (rush current) immediately after applying a voltage. Because it uses barium-based ceramics, it has poor thermal shock resistance.
There was a problem in that it could not be used as a heater for heating and cooling because it cracked and cracked.

This invention was made taking these circumstances into consideration, so
Can generate high-temperature hot air, has small inrush current,
The company also provides heaters for generating hot air with excellent thermal shock resistance.

(D) Means for Solving the Problems The present invention includes a conductive ceramic plate mainly composed of SiC, electrodes that sandwich the ceramic plate, and heat dissipation fins provided on the electrodes, and between the electrodes. This is a heater for generating hot air, which is characterized in that hot air is obtained by applying a voltage and blowing air through radiation fins.

The conductive ceramic plate may be made of high-purity SiC ceramics, recrystallized SiC ceramics, SiC5iaN4 ceramics, or the like. Preferably, the electrode is a metallized layer formed by spraying aluminum, nickel, or the like onto the surface of a conductive ceramic plate.

(E) Function Conductive ceramics containing SiC as a main component have little change in resistance over a wide temperature range, and can be energized even in high temperature ranges. Therefore, high-temperature hot air can be obtained by applying a voltage to the conductive ceramic plate through the electrodes and blowing air through the radiation fins.

Furthermore, since the resistance value changes little with respect to temperature, inrush current can be extremely reduced. Furthermore, SiC ceramic has high conductivity and low coefficient of thermal expansion, so it has good thermal shock resistance and excellent heat conduction efficiency to the heat dissipation fins. Furthermore, since SiC itself is an inexpensive material, a low-cost heater can be obtained.

(f) Examples Hereinafter, the present invention will be described in detail based on examples shown in the drawings. This invention is not limited by this.

FIG. 1 is a perspective view of a heater showing an embodiment of the present invention;
FIG. 2 is an exploded explanatory view of FIG. 1. In these figures, 1 is a conductive ceramic plate mainly composed of SiC, 2 is
a and 2b are heat-resistant electrodes provided on the upper and lower surfaces of the ceramic plate 1, respectively; 3a and 3b are aluminum metal heat dissipation structures (aluminum fins) bonded and fixed to the surfaces of the electrodes 2a and 2b; 3c and 3d; are heat dissipation structures 3a and 3b
This is a power supply terminal provided at the end of the

In such a configuration, the AC power supply 4 connects the power supply terminals 3c,
When connected to 3D, the ceramic plate! A current flows through the ceramic plate 1, and the ceramic plate 1 generates heat. Then, the heat is radiated by the metal heat radiating structures 3a and 3b. Therefore, when this heater is housed inside the fan case 7 as shown in FIG.
L.

3b and is emitted in the direction of arrow B.

Therefore, in the configuration shown in FIG. 3, the air flow rate Q (a
The input power P (W), the ceramic plate surface temperature Ts ('C), and the blowing temperature Tb ('C) with respect to 3/5 inch) were actually measured. The results are shown in FIG. Note that the blowing temperature Tb is IOc++ from the front of the device as shown in Fig. 3.
This was measured at a distant point C.

Also, in this measurement, a conductive ceramic plate! were arranged in parallel as shown in Figure 2, and each of them
i C(70) S i sN-(30) made of ceramics, dimensions 42xxX 16xxX 3
It is an element with aX (thickness) and electrical resistance of 51Ω. moreover,
The bulk density of this ceramic is 2.18/am', the porosity is 30%, the bending strength is lOKg/xz", and the coefficient of thermal expansion is 4 x 10-@/"C1 thermal conductivity is 0.03ca.
l/c@・sec・℃. Further, the electrodes 2a and 2b are metallized layers (thickness 1oou@) formed on both sides of a conductive ceramic plate 1 by aluminum spraying. Furthermore, the metal heat dissipation structures 3m and 3b are made of aluminum corrugate (length 150xt, width !6zx, height 11
! l, fin pitch I JFJI, fin thickness 0.1z
+w) was used.

The characteristics shown in FIG. 4 are that when the airflow 1tQ is increased, the input P decreases slightly, and the surface temperature TS and the blowing temperature Tb of the conductive ceramic plate 1 decrease, but the ceramic plate 1 is as shown in FIG.
As shown in the figure, the volume resistivity hardly changes in the temperature range of 0 to 600°C, so the ceramic plate l is sufficiently energized even at high temperatures, and when heated with high-temperature hot air (e.g. 1.om''/intelligence in) can be obtained.

Furthermore, since the resistance value of the ceramic plate 1 changes little with respect to temperature, the inrush current at the start of energization is small. In addition, it has high thermal conductivity and low coefficient of thermal expansion, so it is resistant to thermal shock.
Excellent heat conduction to the radiation fins.

Also, in the above, a conductive ceramic plate! niS i
Although actual measurement results are shown using C(7G) S i *N4(30) ceramics, similar effects can be obtained using high purity SiC ceramics or recrystallized SiC ceramics.

Table 1 shows examples of physical properties of high-purity SIC ceramics.
(b) and (c) of FIG. 5 show the temperature change characteristics of the volume resistivity of ceramics 5C-850 and sc-sso in Table 1, respectively.

(G) Effects of the Invention According to the present invention, it is possible to generate hot air at a high temperature, and since the change in resistance with respect to temperature is relatively small, inrush current can be suppressed to a low level, and thermal shock resistance is improved. It is possible to provide a heater for generating hot air that can excellently withstand rapid heating and cooling and is inexpensive.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing one embodiment of the present invention, FIG. 2 is an exploded configuration explanatory diagram of FIG. 1, and FIG. 3 is a configuration explanatory diagram of a hot air heater to which the embodiment shown in FIG. 1 is applied. FIG. 4 is a graph showing the characteristics of the hot air heater shown in FIG. 3 with respect to air volume, and FIG. 5 is a graph showing the volume resistivity characteristics of various ceramic materials with respect to temperature. 1... Conductive ceramic plate, 2λ, 2b... Electrode, 3a, 3b... Metal heat dissipation structure, 3c, 3d.
...Power supply terminal.

Claims (1)

[Claims] 1. A conductive ceramic plate mainly composed of SiC, electrodes that sandwich the ceramic plate, and heat radiation fins provided on the electrodes, and a voltage is applied between the electrodes to ventilate the heat radiation fins. A heater for generating hot air, which is characterized by being able to generate hot air.