JPH0324754B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an infrared radiating device that improves both rapid heating properties and far-infrared radiation efficiency.

[Technical background of the invention and its problems]

Conventionally, methods of heating objects using infrared radiation have been known, but in recent years, it has been found that the longer the wavelength of infrared rays, the better the heating efficiency, and this has attracted attention.

In general, the following characteristics are required for far-infrared radiating devices.

(1) Emissivity is close to 1 in the far infrared region (wavelength 3 to 50μ).

(2) Excellent rapid heating properties.

(3) The infrared emitting substance must be thermally and chemically stable at a temperature of 500 to 700°C, which is suitable for radiation.

(4) Good adhesion between the support and the infrared emitting substance;
No peeling or cracking due to thermal shock.

(5) Strong against mechanical shock.

However, infrared light bulbs are known as conventional far-infrared radiation devices, and although they are excellent in rapid heating properties, on the other hand, the radiant energy ratio of far-infrared rays is small, so the heating effect is small. Furthermore, ceramic heating elements such as Tecorundum (trade name) are used exposed in the outside air, and although their rapid heating properties are second only to infrared light bulbs, their far-infrared emissivity is still insufficient. Furthermore, zircon-based (ZrO ₂・SiO ₂ ), silicon carbide-based (SiC), and lanthanum chromate-based materials are known as far-infrared emitting materials with thermal conductivity, and it is possible to construct an envelope using such materials. An infrared radiating device is conceivable, in which a heating element such as an iron-chromium wire is housed in the infrared radiating device. This material has the advantage of high emissivity of far-infrared rays, but on the other hand, not only is it inferior in rapid heating properties, but also it is difficult to form a long envelope with the zircon-based material. Furthermore, so-called thermal spray heaters are known in which these far-infrared emitting substances are sprayed onto the surface of a metal envelope, but these also have poor heating speed and are difficult to manufacture because they require surface treatment of the envelope. It's also complicated and expensive.

[Purpose of the invention]

An object of the present invention is to provide an infrared radiating device that has a high far-infrared emissivity and is excellent in rapid heating properties.

[Summary of the invention]

By forming a conductive far-infrared emitting ceramic heat-generating layer on the surface of the near-infrared transparent envelope housing the electric heating element so as to bridge both ends thereof, it is possible to form a conductive far-infrared emitting ceramic heat-generating layer on the surface of the near-infrared transparent envelope that houses the electric heating element. It is designed to heat up quickly when it is energized to generate heat at the same time.

[Embodiments of the invention]

The details of the invention will be explained by means of illustrated embodiments. The figure shows an example of a light bulb-shaped infrared radiation device to which the present invention is applied. 1 is a tubular envelope made of quartz glass; 2 and 2 are sealing portions formed by crushing and sealing both ends of the envelope 1; and 3 and 3 are molybdenum embedded in the sealing portions 2 and 2. The introduction foils 4, 4 are this introduction foil 3,
3 and an inner conductor wire introduced into the envelope 1;
is a tungsten coil heating element mounted between these inner conductors 4, 4, 6, 6... are anchors that support this heating element 5, and 7, 7 are connected to the introduction foils 3, 3 to seal the sealing part 2. , 2 is an outer conductor extending outside, 8 is the envelope 1
A conductive far-infrared emitting ceramic heating layer formed between both ends of the outer surface; 9 is an optical window exposing the surface of the envelope 1 in a slit shape along the longitudinal direction of the heating layer 8; Metal bands 11, 11 fastened to both ends of the heat generating layer 8, respectively, are electrical terminals that serve both to fasten the bands 10, 10 and to connect a power supply line (not shown).

The quartz glass has excellent weather resistance, is resistant to thermal shock, and also transmits light in a wide wavelength range from visible light to far infrared rays.

The heat generating layer 8 is made of conductive and far-infrared emissive ceramics with a thickness of 50 to 150 μ, such as lanthanum chromate (LaCrO ₃ ) or graphite-containing ceramics, and has appropriate electrical resistance and thermal and chemical stability. The thermal expansion coefficient is similar to that of the envelope material. And far infrared rays, for example 3 to 50μ
It has a characteristic of high emissivity of far infrared rays of m. To obtain the heat generating layer 8, for example, appropriate amounts of lanthanum alkoxide and chromium alkoxide may be mixed, applied to the surface of the envelope 1, and baked.

This infrared emitting device connects the outer conductors 7, 7 and the electrical terminals 11, 11 simultaneously to a power source. Then, both the heating element 5 and the heating element 8 are energized and generate heat, and their temperature increases rapidly. Therefore, most of the energy emitted by the heating element 5 is as near infrared rays (wavelength 0.8 to 3 μm).
Some of it is emitted as visible light or far infrared rays (wavelength 3 to 50 μm). These emitted lights pass through the envelope 1, most of which heats the heat generating layer 8, and some of which is emitted as is from the optical window 9. In this way, the heat generating layer 8 generates heat not only by itself but also by radiation from the heat generating element 5, so the temperature rises rapidly and the far infrared rays are fully radiated in a short period of time. Since the heat generating layer 8 emits far infrared rays well, in this example device, near infrared rays emitted from the optical window 9 and far infrared rays emitted from the heat generating layer 8 are mixed and emitted.

Next, the envelope 1 was made to have an outer diameter of 10.8 mm and a length of 172 mm, and a lanthanum chromate ceramic heat generating layer 8 with a thickness of 100 μm was formed thereon by the alkoxide method, and the proportion of the heat generating layer 8 on the surface of the envelope 1 was We obtained various prototypes with different temperatures and measured their emission spectra. The results are shown in FIG. In the figure, the horizontal axis shows the wavelength in μm, and the vertical axis shows the specific radiation intensity in % units with each peak as 100. Curve A shows the entire surface of the envelope 1 as a heating layer. Curve B shows the radiation spectrum with 80% coverage, curve C shows the radiation spectrum with 50% coverage, and curve D shows the comparative example with no heating layer provided. It can be seen from this figure that the higher the area covered by the heat generating layer, the higher the ratio of far infrared rays and the lower the ratio of near infrared rays.

Next, in the above prototype, the heat generating layer 8 is
A thermal spray heater in which lanthanum chromate was thermally sprayed on a metal envelope and an infrared light bulb with no heating layer provided on the quartz envelope 1 described above were obtained by taking a sample that occupies 80% of the surface and investigating the temperature rise after energization. The temperature rise characteristics of The test items all had the same input, and the temperature measurement points were the heat generating layer surface for the above-mentioned example device, the thermal spray layer surface for the thermal spray heater,
The infrared light bulb was placed on the surface of the envelope. This result is the 6th
As shown in the figure. In the figure, the horizontal axis shows the elapsed time from the start of energization in minutes, and the vertical axis shows the surface temperature in degrees Celsius.Curve A is the device of the above embodiment, curve B is the thermal spray heater, and curve D is the thermal spray heater. The temperature rise curves of the above infrared light bulbs are shown respectively. From the figure, it can be seen that the temperature rise of the device of this embodiment is the fastest, and the reached temperature is higher than that of the infrared light bulb. This is because most of the output of a light bulb is in the near infrared rays and passes through the envelope, so the surface temperature does not rise that high. This is because in addition to this, the heat generating layer 8 itself also generates heat.

Next, a heat generating layer 8 made of lanthanum chromate ceramics formed by the alkoxide method described above was subjected to a thermal test in consideration of the usage conditions.
The test involved applying alternating cold shocks at a high temperature of 600℃ and room temperature.As a result, no peeling or cracking was observed even after over 10,000 cycles of testing, and there were no problems with the product's lifespan.

In the above embodiments, the lanthanum chromate ceramic layer was formed by the alkoxide method because the ceramic layer can be formed at a relatively low temperature and the adhesion strength of the formed ceramic layer is high. In the present invention, the heat generating layer is not limited to lanthanum chromate, but it is necessary to have appropriate conductivity and high far-infrared emissivity, and any known method may be used to form the layer. , it is acceptable to emit some near-infrared rays.

Further, in the above embodiment, a part of the surface of the envelope was exposed, but in the present invention, the entire surface of the envelope may be covered with a heat-generating layer. The other portions may be coated with a non-conductive far-infrared emitting material. Furthermore, the heat generating layer only needs to bridge both ends of the envelope, and its shape may be linear or spiral.

Furthermore, the constituent material of the envelope in the present invention is not limited to the above-mentioned quartz glass, but may also be alumina ceramics, crystallized glass, corundum, etc. In short, any material that transmits near infrared rays (wavelength 0.8 to 3 μm) can be used. It is more preferable if it can transmit not only near infrared rays but also visible light and far infrared rays.

Furthermore, the present invention may have a structure in which the envelope is not sealed; for example, an aluminum-containing iron-chromium alloy coil heating element is housed in an alumina ceramic tubular envelope that is open at both ends, and the envelope is opened at both ends. It may be air-permeable closed and a conductive far-infrared ray emitting ceramic heating layer formed on the surface of the envelope. Furthermore, the envelope may be in the form of a straight tube or a curved tube.

〔Effect of the invention〕

In the infrared radiation device of the present invention, a conductive far-infrared ray emitting ceramic heating layer is provided on the surface of a near-infrared transparent tubular envelope housing an electric heating element so as to bridge both ends thereof, so that the heating layer is electrically It has the effect of both generating heat and emitting far-infrared rays, and has the advantage of efficiently emitting far-infrared rays and rising rapidly after energization.

[Brief explanation of the drawing]

Fig. 1 is a front view of an embodiment of the infrared radiating device of the present invention, Fig. 2 is a longitudinal cross-sectional view, Fig. 3 is a side view, Fig. 4 is a cross-sectional view, and Fig. 5 is a heat generation FIG. 6 is a graph showing the relationship between the layer coverage ratio and the radiation spectrum. Similarly, FIG. 6 is a graph showing the superiority of the present invention by comparing the rise time after energization with that of the conventional method. DESCRIPTION OF SYMBOLS 1... Envelope, 5... Electric heating element, 6... Anchor, 8... Conductive far-infrared emitting ceramic heating layer, 9... Optical window, 11... Electric terminal.

Claims (1)

[Scope of Claims] 1. A near-infrared transmitting tubular envelope, an electric heating element housed in the envelope, and a conductive element formed on the surface of the envelope by bridging both ends thereof. 1. An infrared radiation device comprising: a far-infrared radiation emitting ceramic heating layer; and electrical terminals provided at both ends of the heating layer. 2. The infrared radiation device according to claim 1, wherein the heat generating layer is made of lanthanum chromate ceramics. 3. The infrared radiation device according to claim 1 or 2, wherein the heat generating layer covers 50% to 80% of the surface of the envelope.