JPH10284238A - Glass plate for electromagnetic cooking utensil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a temperature of a pot from the lower to the upper parts of a glass plate to be precisely measured using an infrared-ray sensor by forming an infrared-ray permeable infrared-ray permeation part at a part facing an infrared-ray sensor and covering the other part with a non-transparent part. SOLUTION: A glass plate 7 has an infrared-ray permeation part 2 at a part facing an infrared-ray sensor 5, and the other part is covered with a non- transparent layer 1. A body part 8 houses a magnetic generation coil 9 of an electromagnetic cooking utensil 3, an infrared-ray sensor 5 or the like. At the upper part of the body part 8, a control panel 80 displaying temperature information obtained from the infrared-ray sensor 5 is provided. A magnetic field is formed by a magnetic generation coil 9, and a joule heat of an inductive current is generated at a pot 6 with this magnetic field. With this heat, food 60 in the pot 6 is cooked. The temperature of the pot 6 is measured in contact with the lower face of the glass plate 7, and temperature control is performed by this detecting signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a glass plate used as a top plate of an electromagnetic cooker.

[0002]

2. Description of the Related Art An electromagnetic cooker has been widely used as a cooker for cooking by heating using electricity. As shown in FIG. 6, the electromagnetic cooker includes a main body 98 provided with a magnetic generating coil 99, and a glass plate 970 provided on an upper surface of the main body 98. A temperature sensor 94 for detecting the temperature of the pan 96 is provided inside the main body 98.
Is arranged. As the glass plate 970 for the electromagnetic cooker used here, white crystallized glass is used. As the temperature sensor 94, a contact-type thermistor-type temperature sensor mounted below the glass plate 970 is used.

[0003] The principle of cooking by the electromagnetic cooker 9 is that a magnetic field is formed by a magnetic generating coil 99, Joule heat of an induced current is generated in the pot 96 from the magnetic field, and the heat 960 in the pot 96 is generated by the heat. To cook. The temperature of the pot 96 is measured by bringing the temperature sensor 94 into contact with the lower surface of the glass plate 970, and the temperature is controlled by the detection signal. The temperature information obtained by the temperature sensor 94 is displayed on a control panel 980 above the main body 98.

[0004]

However, in the above-mentioned conventional glass plate for an electromagnetic cooker, the bottom 96 of the pot 96 is not provided.
An indirect measurement method is performed in which the heat of No. 1 is transmitted to a glass plate, the temperature of the glass plate is measured by a thermistor type temperature sensor, and the temperature of the pan is estimated. Therefore, it is difficult to accurately measure the temperature of the pot.

Therefore, as a solution to the above-mentioned conventional problems, first, as shown in FIG. 7, a hole 971 is made in the center of a glass plate 970, and a thermistor type temperature sensor 94 is provided in the hole 971. Is attached so as to contact the bottom 961 of the pan 96. The thermistor type temperature sensor 94 always protrudes from the glass plate 970, but is pushed down by its weight when the pot 96 is placed. The gap between the temperature sensor 94 and the hole 971 of the glass plate 97 is closed by a rubber seal 972. The temperature sensor 94 is used to directly contact the bottom 961 of the pan 96,
7, the temperature can be measured more accurately than the indirect measurement method in which the temperature is measured via the.

However, holes 971 are formed in the glass plate 970.
Opening reduces the mechanical strength of the glass plate 970. Further, since the thermistor type temperature sensor 95 protrudes from the glass plate 970, it becomes difficult to clean the surface of the glass plate 97. Further, the thermistor type temperature sensor 94 has a slow response to a temperature change, and it is difficult to measure the temperature of the pan immediately.

Second, as shown in FIG. 8, a method using an infrared sensor 95 as a temperature sensor for directly measuring the temperature of the bottom 961 of the pan 96 is described in Japanese Patent Application Laid-Open No. 3-184295. This method employs a non-contact method in which infrared rays generated from the pan 96 are captured and measured by an infrared sensor 95. The temperature of the pan 96 is measured by placing the infrared sensor 95 below the glass plate 975,
Temperature control is performed by this detection signal. Infrared sensor 95
Is displayed on the control panel 980 above the main body 98. In this non-contact method, the temperature of the bottom 961 of the pot 96 can be directly measured, so that the temperature of the bottom 961 of the pot 96 can be accurately measured. In addition, the infrared sensor 95 has a quick response to a temperature change, and can immediately measure the temperature of the pot. Since the glass plate 975 used here needs to transmit infrared rays emitted from the pan 96, transparent crystallized glass is used.

However, since the glass plate 975 is transparent, it not only has high infrared transmittance but also high visible light transmittance. For this reason, there is a problem that the internal device of the electromagnetic cooker 9 can be seen through.

In view of the above-mentioned conventional problems, the present invention can accurately measure the temperature of a pan above a glass plate using an infrared sensor, and has excellent concealment of internal equipment, It is an object of the present invention to provide a glass plate for an electromagnetic cooker which is also excellent in target strength.

[0010]

According to a first aspect of the present invention, there is provided a glass plate used as a top plate of an electromagnetic cooker for detecting a temperature of a body to be heated by an infrared sensor, wherein the glass plate has an infrared ray at a portion facing the infrared sensor. A glass plate for an electromagnetic cooker, having a transparent infrared transmitting portion, wherein the other portion of the infrared transmitting portion of the glass plate is covered with an opaque layer.

[0011] In the present invention, the glass plate has an infrared transmitting portion that transmits infrared light at a portion facing the infrared sensor. In the glass plate of the present invention, portions other than the infrared transmitting portion are covered with an opaque layer.
The infrared transmitting portion is not covered by the opaque layer. Therefore, the infrared transmitting part transmits most of the infrared light. Therefore, most of the infrared light emitted from the pan passes through the infrared transmitting portion and is captured by the infrared sensor provided below the infrared transmitting portion. Therefore, according to the present invention, the temperature of the pot bottom can be directly measured, so that the temperature is accurate and precise temperature control is possible.

An opaque layer is provided on the other portion of the infrared transmitting portion of the glass plate. For this reason, the internal devices of the electromagnetic cooker are not visible from the outside, and the internal concealment is excellent. Further, since the glass plate is made of transparent crystallized glass, it has excellent mechanical strength. The surface of the glass plate is
Because it is flat, the cleaning and cleaning properties of the glass plate are high.

The glass plate has a property of transmitting infrared rays, but may be opaque or transparent. On the other hand, the opaque layer is an opaque layer that does not transmit visible light, but may or may not transmit infrared light.

Preferably, a plurality of the infrared transmitting portions are provided on the glass plate. Thus, infrared rays emitted from the object to be heated such as a pan can be detected at a plurality of locations, and the temperature distribution of the entire object to be heated can be measured.

Preferably, the opaque layer is formed by printing and printing a raster paint or an inorganic pigment paint. Thereby, an opaque layer having high heat resistance can be formed.

A transparent crystallized glass is used as the glass plate. The crystallized glass, petalite _{Li 2 O · Al 2 O 3} · 8SiO 2, spodumene L
_{i 2 O · Al 2 O 3} · 4SiO 2, lithium carbonate Li ₂
CO ₃ , clay Al ₂ O ₃ .2SiO ₂ .2H ₂ O, soda feldspar Na ₂ O.Al ₂ O ₃ .6SiO ₂ , potassium feldspar K
₂ O.Al ₂ O ₃ .6SiO ₂ , magnesite MgCO
₃ , titanium oxide TiO ₂ , zirconium oxide ZrO ₂ ,
Raw materials such as diphosphorus pentoxide P ₂ O ₅ and arsenic oxide As ₂ O ₃ were melted at a high temperature of about 1700 ° C.
It is formed by roll forming or press forming at a temperature of 0 to 1500 ° C., and then gradually cooled in the same manner as ordinary glass.

Since no crystals are formed in the formed glass, the thermal expansion is as large as 4.0 to 5.0 × 10 ⁻⁶ / ° C. Therefore, next, the above-mentioned cooled glass is crystallized to have low expansion properties. The crystallization treatment is 650-80
At a temperature of 0 ℃ crystal nuclei, such as ZrO ₂ · TiO _2, ZrO ₂ is produced to a size of about 0.005 .mu.m, eight hundred and fifty to ninety
At a temperature of 0 ° C., around the above crystal nucleus, β-quartz SiO ₂ or β-eucryptite Li ₂ O.A
l ₂ O ₃ .2SiO ₂ crystals are formed with a size of about 0.1 μm.

The crystallized glass in which the β-quartz or β-eucryptite crystals are formed has a characteristic that these crystals are shrunk by a rise in temperature, and therefore, counteracts the expansion of the remaining portion of the glass other than the above crystals. Hardly expands. Moreover, the size of this crystal is about 0.1 μm, which is light visible to the human eye, that is, the wavelength of visible light (about 0.5 to
(0.7 μm), the refractive index between the crystal and the remaining portion becomes close, and the crystal becomes transparent without scattering light. Also, the infrared transmittance is high.

The opaque layer is formed, for example, by screen printing and printing a raster paint or an inorganic pigment paint as described above. Raster paints are precious metals, specifically gold (Au), platinum (Pt)
, Silver (Ag), rhodium (Rh), palladium (Pd)
Bismuth as the main component consisting of
Resin-based liquids of (Bi), iron (Fe), and silicon (Si) are used as raw materials. Ethylcellulose or nitrocellulose resins are added to these raw materials and mixed to form pastes having a viscosity that facilitates screen printing.

The inorganic pigment-based paint is Li ₂ O—Al
A low-expansion glass flux mainly composed of ₂ O ₃ —SiO ₂ —PbO—B ₂ O ₃ consisting of 10 to 60% by weight and an inorganic pigment of 40 to 90% by weight. I do.

A colorant can be added to the crystallized glass. Thereby, a desired color can be given to the crystallized glass. When a coloring agent is added, the crystallized glass must have such a property that at least its infrared transmitting portion can transmit infrared light. Further, it is preferable that the front and back surfaces of the glass core be flat without dimple processing or the like so that infrared rays can easily pass therethrough.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 An electromagnetic cooker according to an embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, the electromagnetic cooker 3 of the present embodiment has a main body 8 provided with a magnetic generating coil 9 and an infrared sensor 5, and a glass plate 7 provided as a top plate on the upper surface of the main body 8. ing. The glass plate 7 is made of crystallized glass that transmits infrared rays. An infrared sensor 5 for detecting the temperature of the pan 6 placed on the glass plate 7 is provided inside the main body 8.

As shown in FIGS. 2 and 3, the glass plate 7 has an infrared-transmitting infrared transmitting portion 2 at a portion facing the infrared sensor 5, and the other portions of the infrared transmitting portion 2 It is covered by an opaque layer 1. The glass plate 7 has zero thermal expansion and is transparent.

As shown in FIG. 1, the main body 8 is a case for housing the internal equipment of the electromagnetic cooker 3, specifically, the magnetic generating coil 9, the infrared sensor 5, and the like. Above the main body 8, a control panel 80 for displaying temperature information obtained by the infrared sensor 5 is provided.

The principle of heating cooking by the electromagnetic cooker 3 is that a magnetic field is formed by a magnetic generating coil 9 and the pan 6
Then, Joule heat of the induced current is generated, and the food 60 in the pan 6 is cooked by the heat. The temperature of the pan 6 is measured by bringing the infrared sensor 5 into contact with the lower surface of the glass plate 7,
Temperature control is performed by this detection signal.

Next, a method for manufacturing the above glass plate will be described. First, 4.5 wt% Li ₂ O, 65.5
Weight% SiO ₂ , 22.0 weight% Al ₂ O ₃ , 0.5 weight% Na ₂ O, 0.3 weight% K ₂ O, 0.5 weight% Mg
O, 2.0% by weight TiO ₂ , 2.5% by weight ZrO ₂ ,
A raw material powder having a composition of 1.0% by weight P ₂ O ₅ and 1.2% by weight As ₂ O ₃ was prepared. Then, the raw material powder is
It was melted at a high temperature of 700 ° C, roll-formed into a plate at a temperature of 1400 ° C, and then slowly cooled.

Next, this molded product is cut into a size of a top plate (250 mm × 250 mm) and cut at about 700 ° C.
Once at a temperature of ZrO ₂ · TiO ₂ , ZrO ₂
Then, at a temperature of about 850 ° C., β-quartz SiO ₂ or β-eucryptite L
An i ₂ O.Al ₂ O ₃ .2SiO ₂ crystal was generated to obtain a low-expansion transparent crystallized glass. The thickness of the crystallized glass was 4.0 mm.

Next, a light-shielding inorganic pigment-based paint was prepared. The inorganic pigment-based paint is a mixture of the following low-expansion glass flux and a green pigment which is an inorganic pigment. That is, the above-mentioned glass flux is obtained by mixing and melting glass raw materials, and then pulverizing them after cooling. Glass raw materials, main component _{Li 2 O-Al 2 O 3} -SiO 2 -
A PbO-B ₂ O ₃ -based, Li ₂ O of specifically 3.5 wt%, 15.0 wt% of Al ₂ O _3, 35.0 wt% of SiO _2, 40.0 wt% PbO, 4.0% by weight
Of B ₂ O _3, 1.5 wt% of TiO _2, becomes more and ZrO ₂ of 1.0 wt%. Glass raw material powders mixed to have these compositions were heated and melted at 1300 to 1450 ° C. The molten glass was poured into water, quenched, and solidified. The solidified product was finely pulverized in a ball mill by a wet method and dried. As a result, a glass flux having an average particle size of 3 to 5 μm was obtained.

The raw materials of the green pigment are mainly composed of 45.0% by weight Cr ₂ O ₃ , 15.0% by weight Co ₃ O ₄ , 30.0% by weight.
% Of ZnO, 5.0% by weight of Al ₂ O ₃ , and 5.0% by weight of SiO _2. These green pigment raw material powders were mixed. 900-10 mixed green pigment raw material powder
It was calcined at 00 ° C, pulverized, fired at 1200 to 1400 ° C, and further pulverized to obtain a green pigment having an average particle diameter of 1 to 4 µm.

Next, 30% by weight of the above-mentioned glass flux and 70% by weight of the above-mentioned green inorganic pigment were kneaded with 60% by weight of an acryl-based organic binder by means of an outer shell to form a paste. This paste for forming an opaque layer was diluted with an organic solvent such as butyl carbitol acetate to a viscosity that allowed easy printing.

Next, the above-mentioned paste for forming an opaque layer was screen-printed on the back surface of the transparent crystallized glass.
As shown in FIG. 3, the inorganic pigment-based paint was printed in a solid color on the central portion 70 of the glass plate 7 except for the infrared transmitting portion 2 which was not printed in a circular shape. Then,
At 800-850 ° C, preferably 820 ° C, the opaque layer was baked into crystallized glass. Thus, as shown in FIGS. 2 and 3, the back surface of the glass plate 7 made of transparent crystallized glass could be covered with the opaque layer 1 having a dark green color pattern. In the center 70 of the glass plate 7,
A circular infrared transmitting portion 2 was formed.

This green opaque layer 1 did not crack or peel off. The glass plate 7 made of crystallized glass is transparent and has almost no thermal expansion.
Met. Also. The opaque layer 1 was firmly fixed to the glass plate 7.

Next, the spectral transmittance of the infrared transmitting portion of the obtained glass plate was measured. The spectral transmittance was measured for the transmittance from visible light to infrared light (wavelength: 100 nm to 2500 nm). The result is shown in FIG.

The transmittance of visible light and the transmittance of infrared light of the infrared transmitting portion of the glass plate were measured.
500 nm was selected as a typical wavelength of visible light, and 1500 nm was selected as a typical wavelength of infrared light, and the light transmittance at these two points was measured. The results are shown in Table 1.

[0035]

[Table 1]

As can be seen from Table 1, the infrared transmitting portion of the glass plate of this example is a transparent crystallized glass itself, and thus has high transmittance for both visible light and infrared light. In addition, the infrared sensor 5 built in the electromagnetic cooker 3 of the present example was able to sufficiently capture infrared rays emitted from the pan 6 through the infrared transmission section 2, and was able to measure the temperature accurately.

From the above, it can be seen that the glass plate 7 of the present example has an infrared transmittance sufficient to accurately measure the temperature of the pan 6 with the infrared light captured by the infrared sensor 5 through the infrared transmitting portion 2.

Although a transparent crystallized glass is described in this example, a crystallized glass having a brown color as disclosed in Japanese Patent Application Laid-Open No. 62-182135 may be used. However, this colored glass has dimples on the back side, but this is not effective because the amount of infrared rays that penetrate straight is reduced, and the front and back sides must be flat plates.

Embodiment 2 In this embodiment, an opaque layer was formed by printing and printing a raster paint on the back surface of a glass plate. As in the case of the first embodiment, the raster paint has an infrared transmitting portion which is not printed in a circular shape at the center of the back surface of the glass plate.
The other portions were printed in a solid color.

Raster paints are gold (Au), palladium
(Pd), platinum (Pt), iron (Fe), silicon (
It is made into a paste by mixing these metal resins with Si) as a main component, adding a predetermined amount of synthetic resin, specifically nitrocellulose, and mixing. This raster paint was screen-printed and baked at 820 ° C. on the back surface of the glass plate made of the transparent crystallized glass used in the first embodiment.

As a result, on the back of the transparent crystallized glass,
(Circle in the center and no printing part) Black color was able to be added. In addition, an infrared transmitting portion that was not covered with the opaque layer was formed at the center of the glass plate. The opaque layer adhered firmly to the glass plate without cracking and without peeling.

Next, the spectral transmittance of the infrared transmitting portion of the obtained glass plate was measured in the same manner as in the first embodiment. The result is shown in FIG. In addition, visible light (500
nm) and infrared rays (1500 nm) were measured, and the results are shown in Table 1. From the above measurement results, it was found that the infrared transmitting portion of the glass plate of this example had high transmittance for both visible light and infrared light, and was enough to use an infrared sensor.

Comparative Example 1 In this example, as shown in FIG. 5, the entire back surface of a transparent glass plate 7 was coated with an opaque layer 1 made of an inorganic pigment paint. As the glass plate 7, the same one as in the first embodiment was used. As the inorganic pigment-based paint, the green inorganic pigment-based paint used in Example 1 was used. The inorganic pigment-based paint is printed on the surface of the glass plate 7 and 820
By baking at ℃, the opaque layer 1 was formed. Opaque layer 1
As shown in FIG. 5, was formed on the entire back surface of the glass plate 7 in a solid coating shape, and was also formed on the central portion 70 of the glass plate 7.

The obtained glass plate 7 had a dark green color all over its rear surface. Also, this green opaque layer 1 does not crack, does not peel off,
It was firmly fixed to the glass plate.

Next, the spectral transmittance of the central portion 70 of the obtained glass plate 7 was measured in the same manner as in the first embodiment. The spectral transmittance ranges from visible light to infrared light (wavelength 200 n
m to 2500 nm), and the results are shown in FIG. Further, similarly to the first embodiment, visible light (500 n
m) and infrared (1500 nm) transmittance were measured, and the results are shown in Table 1.

Since the glass plate 7 of Comparative Example 1 has its central portion 70 covered with the green opaque layer 1, the transmittance of both visible light and infrared light is low, and the infrared sensor 5 cannot be used. Was.

Comparative Example 2 In this example, the entire back surface of a transparent glass plate was coated with an opaque layer made of a raster paint. As the glass plate, the same crystallized glass as in the first embodiment was used. The opaque layer was formed by using the raster paint used in Embodiment 2 and printing it on the surface of a glass plate and baking it at 820 ° C. Raster paints are printed on the entire back surface of the glass plate in a solid color.
The center 70 is also printed (see FIG. 5).

The obtained glass plate had a dark black color all over its back surface. The green opaque layer adhered firmly to the glass plate without cracking or peeling.

Next, the spectral transmittance at the center of the obtained glass plate was measured in the same manner as in the first embodiment. The spectral transmittance ranges from visible light to infrared light (wavelength 200 nm to 2500 n
m), and the results are shown in FIG. Also,
The transmittances of visible light (500 nm) and infrared light (1500 nm) were measured in the same manner as in Example 1, and the results are shown in Table 1.

Since the glass plate of Comparative Example 2 had a central portion covered with a black raster-based opaque layer, the transmittance of both visible light and infrared light was slightly low, so that an infrared sensor could not be used. Was.

Comparative Example 3 In this example, crystallized glass that had been crystallized at 1100 ° C. was used as a glass plate. That is, the same composition as in Example 1 was melted, roll-formed, and cut, and then heated at a temperature of about 1100 ° C. to obtain β-spodumene Li ₂ O.
· A Al ₂ O ₃ · 4SiO ₂ crystals were generated, to obtain a crystallized glass.

Next, the spectral transmittance at the center of the obtained glass plate was measured in the same manner as in the first embodiment.
The spectral transmittance ranges from visible light to infrared light (wavelength 200 nm to 2
500 nm), and the results are shown in FIG. Further, similarly to the first embodiment, visible light (500 nm)
And infrared (1500 nm) transmittance were measured. The results are shown in Table 1.

The glass plate of Comparative Example 3 was made of crystallized glass having a white center at the center.
There was almost no transmittance for infrared light, and no infrared sensor could be used.

[0054]

According to the present invention, the temperature of the pan above the glass plate can be accurately measured from below the glass plate by using the infrared sensor, the concealment of the internal equipment is excellent, and the mechanical strength is high. Also, an excellent glass plate for an electromagnetic cooker can be provided.

[Brief description of the drawings]

FIG. 1 is an explanatory sectional view of an electromagnetic cooker according to a first embodiment.

FIG. 2 is a cross-sectional view of a glass plate for illustrating a positional relationship between an infrared transmitting portion and an infrared sensor in the first embodiment.

FIG. 3 is a back view of the glass plate in the first embodiment.

FIG. 4 is an explanatory diagram showing the spectral transmittance of the infrared transmitting portions of Embodiments 1 and 2 and Comparative Examples 1 to 3.

FIG. 5 is a cross-sectional view of a glass plate for illustrating a positional relationship between an infrared transmitting portion and an infrared sensor in Comparative Example 1.

FIG. 6 is an explanatory sectional view of a conventional electromagnetic cooker for measuring the temperature of a pot by an indirect measurement method.

FIG. 7 is an explanatory sectional view of a glass plate for an electromagnetic cooker for measuring a temperature of a pot by a direct contact method in a conventional example.

FIG. 8 is an explanatory cross-sectional view of a conventional electromagnetic cooker that measures the temperature of a pot using an infrared sensor.

[Explanation of symbols]

 1. . . 1. opaque layer; . . 2. infrared transmitting part, . . 4. Induction cooker, . . 5. infrared sensor, . . Pan, 7. . . Glass plate, 8. . . Body part, 9. . . Magnetic generating coil,

Claims (3)

[Claims] 1. A glass plate used as a top plate of an electromagnetic cooker for detecting the temperature of an object to be heated by an infrared sensor, wherein the glass plate has an infrared-transmitting infrared transmitting portion at a portion facing the infrared sensor. A glass plate for an electromagnetic cooker, wherein the other portion of the infrared transmitting portion of the glass plate is covered with an opaque layer. 2. The glass plate for an electromagnetic cooker according to claim 1, wherein a plurality of the infrared transmitting portions are provided on the glass plate. 3. The glass plate for an electromagnetic cooker according to claim 1, wherein the opaque layer is formed by printing and baking a raster paint or an inorganic pigment paint.