JPH01189885A - Infrared heater - Google Patents

Abstract

PURPOSE:To obtain the excellent radiation characteristic by forming an infrared radiation film made of a specific material on the surface of glass or quartz glass. CONSTITUTION:An infrared radiation film 1 is formed on the surface of glass 1 or quartz glass 2 and is heated by an electric resistor heating element 3 made of metal. The film 1 is the sintered body of a mixture made of polyborosiloxane and a metal oxide, the metal oxide is an oxide of the metal selected among metals belonging to groups IB, IIB, IIIB, IVB, VB, VIB, VIIB, IIA, IIIA, IVA, VA in the periodic table. When the film is formed with this material, the excellent radiation characteristic can be obtained, e.g., the wavelength dependency of the permeation and absorption of infrared rays is made homogeneous, the difference of generating sources is eliminated, mild and comfortable temperature feeling is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION The present invention relates to an infrared heater that can be used in household electric heaters and the like.

A conventional electric heater for space heating has a structure in which an electric resistance heating element (hereinafter referred to as a "resistance element") made of nichrome or tungsten is protected by a quartz glass tube. With this configuration, the resistor (temperature is about 10oO℃)
) emitted infrared rays partially pass through the quartz glass protection tube,
Also, some of it is absorbed by the quartz glass, and some of it becomes a loss due to convection or conduction. Furthermore, the infrared rays transmitted through the quartz glass heat the human body, etc., and the infrared rays absorbed by the quartz glass raise the temperature of the quartz glass, which is much lower in temperature than the resistor, but still reaches around 600 degrees Celsius.
Radiant light (infrared rays) from the quartz glass at this temperature also heats the human body. As mentioned above, the structure of the electric heater has not changed in particular in that the resistor is protected with quartz glass.

According to the above conventional configuration, there are two types of infrared rays used for heating. One is the infrared rays that have passed through the quartz glass (hereinafter referred to as transmitted light), and the other is the infrared rays that are secondarily generated from the quartz glass as the temperature of the quartz glass increases (hereinafter referred to as secondary radiation). There is a big difference in the infrared rays of the two dishes. The reason is explained below.

The first is the difference in energy intensity due to the difference in temperature of the source of the infrared rays. The transmitted light is infrared rays from the resistor at a temperature of about 1000°C, and the secondary radiation light is infrared rays from the quartz glass at a temperature of about 600°C.

Since the energy intensity of light is proportional to the fourth power of temperature, the difference between the two is obvious.

The second difference is due to the wavelength dependence of the infrared transmission and absorption characteristics of silica glass. Quartz glass has the property of transmitting most of the short wavelengths of infrared rays with a wavelength of about 5 μm as the boundary, and absorbing most of the long wavelengths. Of course, there are parts that reflect, but for the sake of clarity, we will explain them in terms of transmission and absorption below. Wien's displacement from the resistor at about 1000°C (relationship: T・λ, , x=o, 2asa)
, λmax is about 2μ, and a wide radiation light (hereinafter referred to as primary radiation light) is generated. In reality, the emissivity of the resistor must be used to account for the deviation from the black body. Although the primary radiation light has a continuous wavelength distribution, when it passes through quartz glass, most of the long wavelength light of about 5 μm or more is cut off. Therefore, the transmitted light has a wavelength of about 5 μm or less and has the strongest energy intensity (Vienna displacement), making the human body feel a painful heat. In addition, the energy intensity of secondary radiation from silica glass is weaker than that of transmitted light, and the wavelength distribution is approximately 5 μm or more, making the human body feel mild heat, but the intensity of transmitted light is overwhelming. Because it is so strong, the effect of secondary radiation appears to disappear.

As described above, according to the conventional configuration, differences in the sources of infrared rays affect the temperature range of the human body, and there is a problem in that the short wavelength infrared rays cause uncomfortable heat.

Means for Solving LL The above problems are largely due to the infrared transmission and absorption characteristics of quartz glass. Therefore, as a means to solve this problem, a coating with uniform wavelength dependence of infrared transmission and absorption is formed on the surface of glass or quartz glass, thereby eliminating differences in the sources of infrared rays. This allows you to escape from unpleasant heat and get a mild and comfortable feeling of warmth. Therefore, the structure is such that an infrared radiation coating is formed on the surface of glass or quartz glass, this is used as an infrared radiator, and the infrared ray radiator is heated with a metal electric resistance heating element. Furthermore, the infrared radiation coating is a sintered body of a mixture consisting of polyborosiloxane and a metal oxide, and the metal oxide is Is, Ia, ff1a, IV in the periodic table.
a, V day, VIB, VIB, IA, IA, lVA, VA
It is an oxide of a metal selected from the metals belonging to the group.

For production According to the above configuration, there are the following effects.

Since the surface of the infrared radiator is coated with a sintered body of polyborosiwaxane and metal oxide, the infrared transmission and absorption characteristics of glass or quartz glass can be seemingly eliminated. This eliminates the painful heat on the human body caused by transmitted light.This is because the coating temperature is approximately 600'C, which is much lower than the resistor.
Infrared transmission and absorption characteristics, in other words, high infrared transmittance and ability to generate infrared rays with high efficiency even at low temperatures.

Example It must be taken into consideration that the energy intensity of infrared radiation is proportional to the fourth power of temperature and that it depends on the emissivity of the object. When the temperature of the projector is high, the energy intensity is strong, but the human body feels uncomfortable. If the temperature is low, the energy intensity will be moderate, and the human body will feel mild and comfortable, but if the infrared transmittance is low, infrared rays will not be generated efficiently. In the configuration of the present invention, the emissivity of the infrared ray coating is high at α7 to 0.9 or more in the wavelength range of 2 μm to 30 μm, so infrared rays can be efficiently generated even at a temperature of about 600° C.

Hereinafter, the above-mentioned contents will be specifically explained regarding the operation of the typical heater according to the present invention. The following table shows the infrared transmittance and emissivity of quartz glass and the same transmittance and emissivity of the infrared radiation coating. Assume that the resistor is protected by a tubular quartz glass.

Let the intensity of infrared energy generated by the resistor be 0, and the intensity at the protective quartz glass temperature (T) is the cape, and when a film is formed on the quartz glass (temperature T') B
EIB 1□'. However, in both IT and lT, the blackbody has a temperature T
, T is the intensity generated at T. The actual energy intensity is multiplied by the emissivity (ε).

(ε×18) Expression B IQ >> I l/ (1) Equation 7 Since the difference between % and T is not large, I8 slope 18/ Considering Equation (2), the radiant energy of infrared rays as a heater is , In the case of only quartz glass, at a wavelength of 2 to 5 μm, B · 0.9XIQ (λ) + 0. I X I , (λ) (line 0.9 X I □ (λ)) (3) Formula Wavelength 5 to 30 μm
According to the configuration of the present invention, OXI□ (λ) + 0.7
(5) For wavelengths of 5 to 30 μm, 0XI()(λ)+o, e x I 8/(λ)(6
) From a comparison of equations (3) to (6), it is clear that there is a difference between the two due to the difference in structure; in the case of only silica glass, the term on the short wavelength side causes heat that is painful to the human body. . In contrast, according to the configuration of the present invention, I
Since it is expressed in terms of Tl, there is no direct influence of the heating element.
Provides a mild warming sensation.

An embodiment of the present invention will be described below.

First, a method for producing a mixture of polyborosiloxane and metal oxide for forming a film will be described.

Polyborosiloxane has the following structure: N-methyl-2
- A polymer that uses pyrrolidone (hereinafter referred to as NMP) as a true solvent.

(7) This polyborosiloxane (hereinafter referred to as pss I) is:
Since it has a phenyl group, it can be treated as an organic substance by being soluble in solvents, although it is limited at room temperature. If heated up to 600'C, phenyl groups are completely eliminated (
It becomes a ceramic consisting of st, e, and o. Ceramic material is porous and does not decompose even at about 1,000 tons, maintaining sufficient adhesion to the base material. Metal oxides are mixed with polyborosiloxane, which has these properties. For example, titanium yellow is used as a metal oxide.

Mixing was performed by stirring using ZrO2, Aj'203. Add an appropriate amount of a solvent such as toluene or xylene to ensure efficient dispersion. Of course P B 51
It also contains NMP, a true solvent.

Next, as for the method of forming a film, the mixture thus prepared is applied to a tubular quartz glass by a spray method, the solvent is evaporated and the phenyl group is cut off by heating, and the final a
Firing was performed at OO°C for 5 minutes. The film thickness was approximately 10 μm.

A heater using the film obtained by the above manufacturing method will be explained. A partial sectional view of the heater is shown in FIG. FIG. 1 (- is a conceptual cross-sectional view of the heater configuration, and (b) is an enlarged cross-sectional view of the coating part. In (a), the metal electric resistance heating element 3 is protected by the quartz glass 2, A coating 1 of the present invention is formed on the surface of a quartz glass 2. (b) is an enlarged view of the coating 1, showing a sintered part 4 of Pa5t and titanium yellow 5.
, Zr026.

Consists of Az2o37. The initial mixing ratio of PBS I and metal oxide can be varied over a fairly wide range in terms of weight ratio.

Fig. 2 is an infrared spectral radiation characteristic diagram of the coating according to this example. Fig. 3 shows an infrared spectral radiation characteristic diagram of quartz glass and stainless steel for reference. Measurements were made using a double beam method at a temperature of 500' C. It is clear from FIGS. 2 and 3 that the radiation characteristics of this example are excellent.

The emissivity will be explained below. The following equation holds true between the optical transmittance t of an object, the absorption coefficient, and the reflectance r.

t + a + r = 1 (
Equation 8) According to Kirchhoff's law, the emissivity ε and the absorption rate a are equal, so tε+r = 1 Equation (9) On the other hand, the refractive index n and reflectance r of an object have a relationship according to Fresnel's equation (however, for vertically incident light From this, it can be seen from equations (9) and (10) that if n is small, ε or t becomes large. In addition, as in the present invention, the medium (P
When particles (metal oxide) are dispersed in BSI (ceramized material), infrared rays are reflected on the coating surface, particle surface, and base material surface, as expected from Figure 1 (b). do. This is because infrared rays penetrate into the coating. At the coating surface, infrared rays are reflected into the air due to its refractive index, but infrared rays reflected from the particle surface or the base material surface are absorbed or reflected again by surrounding media and particles. The combination of these phenomena determines the emissivity ε when particles are dispersed in a medium. Therefore, it is preferable that the refractive index of the medium is low, and it is necessary to find the optimum conditions for the particles since they are affected by the degree of dispersion, blending amount, particle size, refractive index, etc. For example, for a material with a high refractive index, reducing the blending amount and increasing the distance between particles will increase ε; conversely, for a material with a low refractive index, increasing the blending amount and reducing the alternating layer between particles will increase ε. etc. are restricted by various conditions.

The coating structure according to the present invention can optimize the above conditions, and can be easily designed as a radiation coating.

As explained above, the heater using the coating of the present invention has excellent infrared radiation characteristics, but the heater was actually energized to evaluate the thermal sensation of the human body depending on the presence or absence of the coating.

As a result, the warm sensation with the film was milder than the conventional one without the film. FIGS. 4 and 5 show schematic diagrams of the heaters used in this evaluation. Further, even when the coated quartz glass was suddenly thrown into water from a 700'C furnace, the film did not peel off.

As described above, according to the present invention, an infrared heater with excellent radiation characteristics can be obtained. Due to its excellent radiation characteristics, loss of infrared rays other than radiation is also reduced.

Effects of the Invention As described above, the infrared heater of the present invention has effects such as being able to obtain a milder feeling of warmth that has not been seen before, and reducing loss of infrared rays.

[Brief explanation of the drawing]

FIG. 1 is a partial cross-sectional view of an infrared heater according to an embodiment of the present invention, FIG. 2 is an infrared spectral radiation characteristic diagram of the coating of the same infrared heater, and FIG. 3 is an infrared spectral radiation characteristic diagram of quartz glass and stainless steel. FIGS. 4 and 5 are schematic perspective views of the infrared heater on which thermal sensation evaluation was performed. 1... Coating, 2... Quartz glass, 3.
...Metal electric resistance heating element, 4 ... Ceramic polyborosiloxane, 5 ... Titanium yellow, 6 ... Zr02.7 ...・・・
Al2O3, 8...Heater, 9...Reflector, 10...Body exterior, 11...Reflector, 12...Body exterior . Name of agent: Patent attorney Toshio Nakao and 1 other person1
°゛Coating 2-Quartz power lath 3-Metal exhibition Electric base unit Figure 1 $2 Figure 3 Copy length (AI town

Claims (1)

[Claims] An infrared radiation coating is formed on the surface of glass or quartz glass, and an infrared radiation coating is provided to obtain radiant heat by heating with an electric resistance heating element, and the infrared radiation coating is a mixture whose main components are polyborosiloxane and metal oxide. It is a sintered body of
The metal oxides include IB, IIB, IIIB,
IVB, VB, VIB, VIIB, VIII, IIA, IIIA, IVA,
An infrared heater that is an oxide of at least one metal selected from metals belonging to Group VA.