JP4989690B2 - Induction heating cooker - Google Patents

Description

  The present invention relates to an induction heating cooker, and in particular, detects infrared rays radiated from a cooking vessel with an infrared sensor, obtains the temperature of the cooking vessel based on the detected amount of infrared rays, and controls temperature during cooking. .

  The induction heating cooker is a cooker in which a heating coil is disposed below a top plate on which a cooking container is placed, and a heated object is heated in the cooking container by electromagnetic induction by passing a high-frequency current through the heating coil.

  As a conventional technique, for example, in a glass plate used as a top plate of an electromagnetic cooker that detects the temperature of an object to be heated by an infrared sensor, the glass plate is an infrared ray transmitting infrared ray transmitting portion facing the infrared sensor. And a glass plate for an electromagnetic cooker characterized in that the other part of the infrared transmitting portion of the glass plate is covered with an opaque layer (see, for example, Patent Document 1). .

Japanese Patent Laid-Open No. 10-284238 (Claim 1, FIG. 1)

  The above-mentioned glass plate for an electromagnetic cooker of Patent Document 1 has a problem regarding appearance that the inside of the heating coil and the like can be seen from the window when the cooking container is not placed on the glass plate.

  The present invention has been made to solve the above-described problems, and infrared rays emitted from a cooking container even when visible light is shielded so that internal components such as a heating coil cannot be seen from the upper part of the infrared sensor. An object of the present invention is to provide an induction heating cooker capable of maintaining the detection accuracy of temperature detection means for detecting temperature by receiving light.

An induction heating cooker according to the present invention includes a top plate on which a cooking vessel is placed and transmits infrared rays, a heating coil for induction heating the cooking vessel, and a cooking plate provided below the top plate, Based on an infrared sensor that receives infrared rays emitted from the container and passed through the top plate, temperature detection means for detecting the temperature of the cooking container based on at least the amount of infrared rays received by the infrared sensor, and a temperature detected by the temperature detection means and control means for controlling the electric power supplied to the heating coil, wherein and a light shielding member for shielding the visible light provided on the back surface or surface of the top plate, the upper part of the infrared sensor, the light shielding member is the amount is reduced by providing an infrared transmission region infrared radiation is transmitted from the cooking vessel, in the infrared transmission region, the The light-shielding material is provided in a dot shape so that the density of the light-shielding material at the center of the outer-line transmission region is smaller than the density of the light-shielding material at the periphery of the infrared transmission region, and the infrared transmission region The infrared transmittance at the center is higher than the infrared transmittance at the periphery of the infrared transmission region, and the infrared refractive index of the light shielding material in the infrared transmission region is ± 10% of the infrared refractive index of the top plate . Within the range .

  In the present invention, the inside of the induction heating cooker is made invisible from the upper part of the infrared sensor, and the infrared rays generated from other than the cooking container during induction heating are cut to maintain the accuracy of temperature detection for the cooking container. Can do.

It is a block diagram which shows the induction heating cooking appliance which concerns on Embodiment 1 of this invention. It is a figure which shows the infrared rays transmission area | region which concerns on Embodiment 1 of this invention. It is a figure which shows the infrared rays transmission area | region which concerns on Embodiment 1 of this invention. It is a figure which shows the infrared rays transmission area | region which concerns on Embodiment 1 of this invention. It is a figure which shows the structure of the light shielding area | region which concerns on Embodiment 2 of this invention. It is a diagram showing a boundary portion between the medium I of refractive index n ₁ and a medium II of the refractive index n _2. It is a graph which shows the incident angle dependence of the energy reflectivity of s-polarized light and p-polarized light concerning Embodiment 2 of this invention. It is a graph which shows the incident angle dependence of the energy reflectivity of p polarization | polarized-light which concerns on Embodiment 2 of this invention. It is a graph which shows the incident angle dependence of the energy reflectance of s-polarized light concerning Embodiment 2 of this invention.

Embodiment 1 FIG.
FIG. 1 is a block diagram showing an induction heating cooker 10 according to Embodiment 1 of the present invention.
The induction heating cooker 10 according to the first embodiment includes a heating coil 4 that induction-heats a cooking container 3 that heats and cooks an object to be heated, an inverter 9 that supplies high-frequency current to the heating coil 4, and a heating coil. 4 and a top plate 2 on which the cooking container 3 is placed.

  Further, an infrared sensor 5 that detects infrared rays emitted from the bottom surface of the cooking container 3 and a contact-type temperature sensor that contacts the lower surface of the top plate 2 and detects the bottom surface temperature of the cooking container 3 are provided below the top plate 2. 6, temperature detection means 8 a for deriving the temperature by the infrared sensor 5 and the contact temperature sensor 6, and control means 8 for controlling the inverter 9 in accordance with the output from the temperature detection means 8 a. The control means 8 has at least inverter control means 8b.

  Further, a light shielding material is provided on the lower surface of the top plate 2 so that infrared rays from other than the cooking container 3 do not enter the infrared sensor 5. Note that the light shielding material refers to a material that can suppress at least transmission of visible light. In Embodiment 1, an inorganic pigment or an inorganic pigment containing a glass component is used as the light shielding material.

As the inorganic pigment, for example, the following substances are used.
(1) The main components are 45.0 wt% Cr ₂ O ₃ , 15.0 wt% Co ₃ O ₄ , 30.0 wt% ZnO, 5.0 wt% Al ₂ O ₃ and 5. 0% by weight of the green pigment consisting of SiO _2.
(2) Chrome yellow, petal, titanium white, ultramarine, etc.
(3) Carbon black.
(4) Black body paint.

  The above-described light shielding material is provided on the entire lower surface of the top plate 2, and a region provided with the light shielding material is referred to as a light shielding region 7a. However, a part of the surface of the top plate 2 located above the infrared sensor 5 is configured to block visible light but easily transmit infrared light. That is, on the surface of the top plate 2 positioned above the infrared sensor 5, the light shielding material is thinly applied or printed, or the light shielding material is provided in a dot shape or sparsely. Thus, the area | region which reduced the quantity provided with a light-shielding material will be called the infrared rays transmission area | region 7b. Therefore, it can be said that the light shielding region 7a is a region of the entire lower surface of the top plate 2 provided with the light shielding material, excluding the infrared transmission region 7b.

  Next, the operation will be described. When the induction heating cooker 10 is turned on by the AC power source 1 and set to a predetermined temperature by the operation switch, electric power is supplied from the inverter 9 to the heating coil 4 under the control of the control means 8. When electric power is supplied to the heating coil 4, an induction magnetic field is generated in the heating coil 4, and the cooking container 3 on the top plate 2 is induction-heated. Due to this induction heating, the temperature of the cooking container 3 rises, and the object to be heated in the cooking container 3 is cooked.

  Here, the operation of the infrared sensor 5 will be described. When the temperature of the cooking vessel 3 rises, infrared rays corresponding to the temperature are emitted from the cooking vessel 3. The infrared sensor 5 is configured by a photodiode, a thermopile, or the like that can detect a wavelength of 2.5 μm or less, for example, and infrared rays that have passed through the top plate 2 are incident on the photodiode or the thermopile. Moreover, disturbance light such as sunlight or illumination may enter the infrared sensor 5 in addition to the infrared rays from the cooking container 3. For this reason, the infrared rays incident on the infrared sensor 5 from other than the cooking container 3 are blocked by the aforementioned light shielding material.

  With these configurations, in the first embodiment, only the infrared rays from the cooking container 3 are incident on the infrared sensor 5, converted into a voltage corresponding to the amount of infrared rays, and amplified. Based on the information from the infrared sensor 5 and the contact temperature sensor 6, the temperature detecting means 8a can detect the temperature of the cooking container 3 accurately. Thereby, the inverter control means 8b controls the inverter 9 correctly, controls the cooking vessel 3 so that it may become predetermined | prescribed temperature, and can cook a to-be-heated material deliciously.

  2, 3 and 4 are diagrams for explaining the infrared transmission region 7b according to the first embodiment. The infrared transmission region 7b in FIG. 2 has a higher infrared transmittance than the light shielding material provided in the light shielding region 7a, or is the same material as the light shielding material, but the layer is made thinner to increase the infrared transmittance. Is provided.

  Examples of the light shielding material applied to the lower surface of the top plate 2 include inorganic pigments or inorganic pigments containing glass components. The light shielding material is provided by printing or adhering to the light shielding region 7a on the top plate 2, and when the same material is used for the infrared transmitting region 7b, the amount of the light shielding material is reduced. In FIG. 2, the infrared transmission region 7 b may be configured to include a light shielding material so that the infrared transmittance gradually increases toward the center of the infrared sensor 5.

  The infrared transmission region 7b in FIG. 3 has a higher infrared transmittance than the light shielding material provided in the light shielding region 7a on the surface of the top plate 2 positioned above the infrared sensor 5, or the same material as the light shielding material. Is printed or adhered in a dot shape, and infrared rays and visible light are transmitted through the gaps between the dot-shaped light shielding materials. In FIG. 4, the dot of the light shielding material is sparse in the central portion of the infrared sensor 5, and the infrared transmittance is further increased in the central portion.

  Conventionally, there is no infrared transmission region 7b that facilitates the transmission of infrared rays, and when the cooking container 3 is not placed, the heating coil 4 can be seen from the outside, and the appearance of the induction heating cooker 10 deteriorates. was there. Therefore, by providing the infrared transmission region 7b as described above on the top plate 2 directly above the infrared sensor 5, the heating coil 4 is hardly visible from the outside. Furthermore, when the cooking vessel 3 is placed, the infrared transmission region 7b transmits infrared rays from the cooking vessel 3, so that it is possible to prevent the temperature detection accuracy from being lowered.

  In the first embodiment, the light shielding region 7a and the infrared transmission region 7b are provided on the back surface of the top plate 2. However, the same effect can be obtained even if the light shielding region 7a and the infrared ray transmitting region 7b are provided on the top plate 2. Moreover, the shape of the dot of the light shielding material is not limited to the square shown in FIG. 3 or FIG. 4, and can take any shape such as a circle, a triangle, a rhombus, a hexagon, or the like.

Embodiment 2. FIG.
FIG. 5 shows a configuration of the light shielding region 7 according to Embodiment 2 of the present invention. In FIG. 5, the light shielding region 7 is formed by coating a light shielding material on the lower surface of the top plate 2. Infrared light such as outside light incident from outside the cooking container 3 is cut by the light shielding material. However, infrared rays other than the cooking container 3 are not cut by 100%, but only a few tens of percent are cut.

  Here, in order to efficiently cut infrared rays other than the cooking vessel 3, the light reflectance at the boundary surface between the two substances will be considered using optical knowledge. If the infrared reflectance (energy reflectance) of the light shielding material coated on the top plate 2 is lowered, the phenomenon that the infrared rays are repeatedly reflected inside the top plate 2 (see the dotted arrow in FIG. 5) can be suppressed.

FIG. 6 is a diagram showing a boundary portion between the medium I having a refractive index n _{1 and} the medium II having a refractive index n ₂ . Consider how the infrared reflectance (energy reflectance) changes depending on the ratio of refractive indices n = n ₂ / n _{1 at} the interface between two different materials.
In FIG. 6, it is assumed that incident light is incident on the boundary surface with the medium II at an incident angle θ ₁ from the medium I side. At the boundary surface, incident light is divided into one that is reflected to the medium I side at a reflection angle θ ₁ and _one that is transmitted through the medium II at a refraction angle θ ₂ .

一般に、物質の表面では、光の反射は入射角と偏光によって大きく変わる。図６において、入射光の偏光（電場ベクトルＥ）が矢印と二重黒丸で表示されている。二重黒丸で表示した部分では、物質境界面（反射面）に平行、すなわち入射面に垂直に偏光した光となっている。自然光は様々な偏光を含んでいるが、それらの偏光は全て入射面に平行な成分（ｐ偏光）と垂直な成分（ｓ偏光）に分けることができ、光のエネルギー反射率については、この２つの偏光について議論すれば足りる。 In the above case, the law of refraction (Snell's law) is established by the following relational expression. That is,

In general, on the surface of a material, the reflection of light varies greatly depending on the incident angle and polarization. In FIG. 6, the polarization of the incident light (electric field vector E) is indicated by an arrow and a double black circle. In the portion indicated by the double black circle, the light is polarized parallel to the substance boundary surface (reflection surface), that is, perpendicular to the incident surface. Natural light includes various polarized light, and all of the polarized light can be divided into a component parallel to the incident surface (p-polarized light) and a component perpendicular to the incident surface (s-polarized light). It is enough to discuss two polarizations.

Ｅ ⊥ 入射面（ｓ偏光）の場合：

When n = n ₂ / n ₁ , the reflectance of p-polarized light and s-polarized light is expressed by the following formula from general optical knowledge. In the following equation, the parameter of the refraction angle θ ₂ is eliminated using Snell's law equation (1).
E // For incident plane (p-polarized light):

E 入射 For incident surface (s-polarized light):

In the above equations (2) and (3), there are two parameters n and θ ₁ . If the two parameters are changed simultaneously, the energy reflectance can be plotted only in a three-dimensional graph. Therefore, here, the incident angle θ ₁ and the energy when the ratio of the refractive indexes of the two media, that is, the value of n is fixed are fixed. Let us discuss the relationship of reflectance.

FIG. 7 shows the equation (2), that is, the energy reflectivity R _p of p-polarized light and the equation ( _n ) when the values of n = n ₂ / n ₁ are set to n = 1.5, n = 1.3, and n = 1.1, respectively. 3) That is, the energy reflectance R _s of s-polarized light is plotted on the graph with respect to the incident angle θ ₁ dependence. 8 separately shows the energy reflectance R _p of p-polarized light in FIG. 7, and FIG. 9 separately shows the energy reflectance R _s of s-polarized light in FIG.

In FIG. 7, the horizontal axis is the incident angle θ ₁ , and the angle is indicated by an arc degree method (radian). In the arc degree method, 180 ° is expressed as π radians, and the horizontal axis represents a range of 0 ° ≦ θ ₁ ≦ 90 °. The vertical axis indicates the energy reflectivity R of the incident light. This indicates how much incident light is reflected at the interface between the two substances.

Incidentally, when the energy reflectance R 1 is 1, all incident light is reflected at the boundary surface.
In FIG. 7, for example, in the case of the relationship between air and glass where n = 1.5, the energy reflectance of incident light at an incident angle of 0 ° is R _s = R _p = 0.04, which means that 4% incident light is incident on the glass surface. It means that it is reflected by.

  The first point that can be read from FIG. 7 to FIG. 9 is that the energy reflectance increases rapidly as the incident angle increases, that is, when incident light is incident on the boundary surface. The second point is that as the ratio of the refractive indices of the two media, that is, the value of n increases, the energy reflectivity of s-polarized light and p-polarized light at each incident angle increases.

  Furthermore, as a third point, it is also important that the energy reflectance of p-polarized light does not greatly depend on the value of n. Even if n = 1.5, n = 1.3, and n = 1.1, the energy reflectance of p-polarized light hardly changes. On the other hand, in the case of s-polarized light, when n = 1.5, n = 1.3, and n = 1.1, a significant difference appears in the change in energy reflectance.

Here, the difference in energy reflectance between s-polarized light and p-polarized light will be considered. As can be seen from FIG. 7, as the incident angle θ ₁ gradually increases, the s-polarized component has a higher energy reflectance than the p-polarized component. This indicates that “the light reflected by the boundary surface of the substance becomes light having a lot of s-polarized components”. Therefore, the s-polarized reflectance formula shown in formula (3) becomes important when considering the reflectance of light.

  The above consideration regarding the reflectance is applied to the second embodiment. A light shielding area 7 coated with a light shielding material is provided on the lower surface of the top plate 2, and infrared rays from outside the cooking container 3 such as outside light are cut by the light shielding material. However, it is not possible to cut 100%, and only tens of percent can cut infrared rays.

In view of the above, when the infrared refractive index of the top plate 2 is n ₁ and the infrared refractive index of the light shielding material is n ₂ , the infrared refractive index n ₂ of the light shielding material is approximately the infrared refractive index n ₁ of the top plate 2. By making it equal (that is, the value of n is made close to 1), infrared rays that are not cut by the light shielding material can be suppressed from being reflected inside the top plate 2.

  That is, if the infrared refractive index of the top plate 2 and the light shielding material are different, infrared reflection occurs at the boundary surface between them, and the infrared light is repeatedly reflected while being attenuated inside the top plate 2 as indicated by a dotted arrow in FIG. It will be. However, the infrared reflectance can be suppressed by setting the refractive indexes of both to substantially the same value (n is made close to 1), and infrared rays from other than the cooking container 3 reach the infrared sensor 5. The rate of detection is greatly reduced.

  In the second embodiment, it was experimentally found that the difference in refractive index between the two is preferably within 10%. Examples of the difference between the refractive index of the top plate 2 and the refractive index within 10% include an inorganic pigment containing a glass component, and the inorganic pigment is applied to the back surface of the top plate 2. In this case, most of the infrared rays other than the infrared rays emitted from the cooking vessel 3 pass through the light shielding material as they are, so that the influence of infrared rays other than the cooking vessel 3 on the infrared sensor 5 can be eliminated, and the temperature of the cooking vessel 3 is set correctly. Can be detected.

Embodiment 3 FIG.
In the third embodiment, the knowledge obtained in the second embodiment, that is, that the difference in the infrared refractive index between the top plate 2 and the light shielding material is within 10% is applied to the first embodiment. is there. In the first embodiment, the difference between the infrared refractive index of the light shielding material coated on the infrared transmission region 7b and the infrared refractive index of the top plate 2 is set to 10% or less, so that the infrared rays inside the top plate 2 are reduced. The reflectance can be suppressed, and the effect of increasing the amount of infrared light transmitted from the cooking container 3 and greatly reducing the rate at which infrared light from other than the cooking container 3 reaches the infrared sensor 5 is detected.

DESCRIPTION OF SYMBOLS 1 AC power supply, 2 Top plate, 3 Cooking container, 4 Heating coil, 5 Infrared sensor, 6 Contact-type temperature sensor, 7 Light shielding area, 7a Light shielding area, 7b Infrared transmission area, 8 Control means, 8a Temperature detection means, 8b Inverter Control means, 9 inverter, 10 induction heating cooker, θ ₁ incident angle, θ ₂ refractive angle, n ₁ refractive index, n ₂ refractive index, n Ratio of refractive index n ₁ and refractive index n ₂ .

Claims (1)

A top plate on which the cooking container is placed and which transmits infrared rays;
A heating coil for inductively heating the cooking vessel;
An infrared sensor that is provided below the top plate and receives infrared rays emitted from the cooking container and passed through the top plate;
Temperature detection means for detecting the temperature of the cooking container at least by the amount of infrared light received by the infrared sensor;
Control means for controlling power supplied to the heating coil based on the temperature detected by the temperature detection means;
A light shielding material for shielding visible light provided on the back surface or the front surface of the top plate,
Wherein the top of the infrared sensor, provided an infrared transmission region infrared radiation is transmitted from the cooking vessel is used the amount of the light shielding member is reduced,
In the infrared transmission region, the density of the light shielding material in the central portion of the infrared transmission region is smaller than the density of the light shielding material in the peripheral portion of the infrared transmission region, and the light shielding material is formed in a dot shape. Providing an infrared transmittance at a central portion of the infrared transmitting region higher than an infrared transmittance at a peripheral portion of the infrared transmitting region;
An induction heating cooker characterized in that an infrared refractive index of the light shielding material in the infrared transmission region is within a range of ± 10% of an infrared refractive index of the top plate.

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