JP2001145558A - Pan for rice cooker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pan for rice cookers where the heating efficiency of electromagnetic induction has been improved. SOLUTION: The pan for rice cookers is provided with a heat generation part that is electromagnetically induced and a heat transfer part 10 that is arranged in the heat generation part, the heat generation part is composed of a magnetic metal layer 11 and a non-magnetic metal layer 12, the non- magnetic metal layer 12 is arranged outside the magnetic metal layer 11 and at the same time is composed thinner than the magnetic metal layer 11, and the non-magnetic layer 12 is 0.1-2.0 times thicker than the thickness for obtaining the same skin electrical resistance value as that of iron.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic induction heating type rice cooker used for ordinary households and businesses.

[0002]

2. Description of the Related Art At present, an electromagnetic induction heating type rice cooker which is widely marketed generally has a magnetic field line generated when a high-frequency current is applied to a heating induction coil provided inside a main body. When entering the magnetic metal that can be heated by electromagnetic induction, an eddy current is generated in the magnetic metal, Joule heat is generated due to the electric resistance of the eddy current, and the pan generates heat, and this heat is applied to cooking rice. is there.

[0003] Here, a typical conventional electromagnetic induction heating type rice cooker pot has an inner surface covered with a fluororesin coating, and aluminum having good heat conductivity is arranged in a lower layer thereof.
And, on its outer surface, that is, on the outermost surface of the pot, a magnetic metal layer such as ferritic stainless steel, iron, permalloy is provided,
This magnetic metal layer is used as a heating section for electromagnetic induction heating.

[0004]

However, in the above-described conventional configuration, the heat generating portion of the pan is generally limited to a magnetic metal such as ferritic stainless steel, iron, and permalloy. Magnetic metal has not been applied to the heating section. Therefore, from the viewpoint of heat generation efficiency, the design is not always optimal. Further, when ferrite-based stainless steel, iron, permalloy, or the like is disposed in the outermost layer, the appearance color is limited to a silver-based color, which is a material color of a metal, so that the appearance does not change. Therefore, in order to improve the design, it is necessary to paint, etc., various anodized film colors of aluminum,
It has been difficult to bring out the beauty of the material itself, such as the color of the anodized film of titanium, the color of high-temperature oxidation, or the color of the copper material.

[0005]

In order to solve the above-mentioned problems, the present invention comprises a heat-generating portion that is electromagnetically induced, and a heat-transfer portion disposed inside the heat-generating portion. It is composed of a metal layer and a non-magnetic metal layer, wherein the non-magnetic metal layer is
It is arranged outside the magnetic metal layer and is configured to be thinner than the magnetic metal layer.

[0006]

According to the first aspect of the present invention, by reducing the thickness of the non-magnetic metal, its skin electric resistance increases, and the non-magnetic metal can effectively function as a heat generating portion by electromagnetic induction. .

[0007] According to the second aspect of the present invention, an electromagnetic induction heating pot having particularly good heat generation efficiency can be obtained.

According to the third aspect of the invention, the arrangement and thickness of the nonmagnetic metal layer can be easily controlled regardless of the shape of the pot.

According to the fourth aspect of the invention, in particular, various colors can be obtained by various anodic oxidations, and in the case of titanium, the same color can be obtained by high-temperature oxidation.
In addition, it is possible to produce a unique metallic color such as copper or an alloy thereof.

[0010]

(Embodiment 1) An embodiment of the present invention will be described below with reference to the drawings.

In general, when electromagnetic induction heating is performed, it is common to use a metal material having a high skin electric resistance value for a heating portion of a cooking pot for electromagnetic induction heating. For example, in the case of typical 430 stainless steel of ferritic stainless steel, 2
When a high-frequency current of 5 kHz is passed through the induction coil, the skin electric resistance value is 23.3 * 10-4Ω, and iron is 9.4 * 10-4.
It can be said that it is high and suitable for electromagnetic induction heating. On the other hand, 0.48 * 10-4Ω for aluminum and 0.39 * for copper
The material is low, such as 10-4, and is generally not suitable for electromagnetic induction heating. Therefore, when a magnetic field is applied to the non-magnetic metal, a repulsive magnetic field is generated in the non-magnetic metal and a repulsive current flows, and the magnetic field cannot pass through the non-magnetic metal.

However, when the thickness of these nonmagnetic metal layers is also reduced, the skin electric resistance eventually increases, and electromagnetic induction heating becomes possible. That is, when the nonmagnetic metal layer is sufficiently thin, the skin electric resistance increases, so that a repulsive magnetic field is hardly generated, and the magnetic field easily passes through the nonmagnetic metal. An eddy current is also generated in the stainless steel by the passed magnetic field, and both the non-magnetic metal layer and the magnetic metal layer such as stainless steel generate heat. The present invention utilizes this phenomenon, and by the combination of the non-magnetic metal layer and the magnetic metal layer, even if the non-magnetic metal is on the outer surface of the pot,
Heat is generated more efficiently than in the case of a single magnetic metal layer, and rice can be cooked.

Hereinafter, the details will be described. FIG.
Is a method of heating rice 9 by electromagnetic induction heating and cooking rice.
This is a rice cooker for 8L rice cooking, comprising an electromagnetic induction heating coil 1, a ferrite 2, a pot bottom temperature detection sensor 3, a heating control board 4, a board cooling fan 5, an operation section 6, a heating plate 7, a steam cap 8, and a pot 9. As a main component, rice and water are added to the pot in an appropriate amount, and then a rice cooking and warming step is executed. This step is executed by program control by a microcomputer.

The pan 9 is made of aluminum 10 having a thickness of 1 mm,
A ferrite stainless steel 1 which is obtained by press-molding a clad material made of ferrite stainless steel 11 having a thickness of 0.8 mm and copper 12 having a thickness of 5 μm, and which is a magnetic metal.
1 and copper 12, which is a non-magnetic metal, are a heating layer for electromagnetic induction heating. The inner surface of the pot is coated with a highly non-stick fluororesin coating 13 on aluminum, while the outer surface of the pot is provided with a transparent polyester-based protective coating 14 for protecting copper, thereby reducing the luster of the copper substrate. It has a configuration that can be maintained for a long time. Further, in this embodiment, ferrite stainless steel is used as the magnetic metal layer material of the pot, but the material is not limited to this, and any material that can be electromagnetically induced can be used.

In this embodiment, a high-frequency current of 25 kHz flows through the electromagnetic induction heating coil during rice cooking. At this time, lines of magnetic force generated by the induction coil are applied to the copper and ferrite stainless steel layers, which are induction heating portions of the pot. When entering, an eddy current is generated and the pot generates heat, and the heat causes a rice cooking process to be performed to cook the rice.

In this embodiment, a high-frequency current of 25 kHz is used. However, it is optional to change this frequency depending on the situation, and it is also possible to change the thickness of the nonmagnetic metal layer accordingly.

Further, by setting the thickness of the nonmagnetic metal layer of the electromagnetic induction heating portion to be 0.1 to 2.0 times the thickness at which the same skin electric resistance as that of iron can be obtained. The above-mentioned heat generation effect becomes more remarkable. Here, the thickness t of the non-magnetic metal for obtaining the same value as the skin electric resistance of iron can be derived by the following formula.

T = δ of non-magnetic metal * Rs of non-magnetic metal / Rs of iron where δ is skin depth, Rs is skin electrical resistance, δ
And Rs are represented by the following equations.

Δ = 5.03 * 103 * (ρ / μ / f) 1/2 Rs = ρ / δ = 1.99 * 10−4 * (μ * ρ * f) 1 /
2 Here, ρ is the specific resistance value of the material, μ is the magnetic permeability, and f is the frequency.

As described above, the skin electric resistance of iron is 25 k.
It is 9.4 * 10-4Ω in Hz. Now, 25kHz
Assuming that the electromagnetic induction heating type rice cooker is operated with the high frequency current of above, when aluminum is applied to the above equation, t = 28 μm,
T = 18 μm for copper and t = 586 μm for titanium, indicating that these materials can provide good electromagnetic induction heating like iron near this region. Therefore, in consideration of the frequency band to be used, the thickness of the nonmagnetic metal layer required to obtain the same value as the skin electrical resistance of iron is calculated, and the thickness of the nonmagnetic metal layer is 0.1 to 2 times the thickness. It is an object of the present invention to arrange a magnetic metal layer on the outer surface of the magnetic metal layer to obtain efficient heat generation.

In addition, by forming the nonmagnetic metal layer by plating, there is an advantage that the thickness can be changed relatively freely, and in addition, the thickness can be partially changed or the plating can be partially prevented so that As a result, the intensity of the electromagnetic induction heating is changed, and as a result, the heat convection in the pan can be changed.

The non-magnetic metal layer can be subjected to anodic oxide coating treatment, protective coating treatment, or both treatments, so that corrosion resistance can be improved, various colors can be obtained, and design can be improved. Can be enhanced.

Further, the pot of the electromagnetic induction heating type rice cooker of the present embodiment is made of a polyester-based clear coating in consideration of the fact that the outer layer of the electromagnetic induction heating portion is made of copper and is easily damaged and discolored. Although it has high durability while maintaining the beautiful base color of copper, this outer surface coating is not particularly limited to polyester, and furthermore, it has a multilayer coating to improve durability, There is no problem with using colored paints.

(Results of Comparative Experiment) The results of comparison between Example 1 and the conventional example are shown below. Here, as shown in FIG. 2, for an electromagnetic induction heating type rice cooker having a conventional typical configuration obtained by press-forming a clad material made of aluminum 10 having a thickness of 1 mm and ferritic stainless steel 11 having a thickness of 0.8 mm. Using the pot as a comparative example, the pot for rice cooker shown in Example 1 of the present invention and the eddy current calorific value at 25 kHz are compared. Here, it is assumed that all the components of the rice cooker other than the pot are the same. Example 1 having a nonmagnetic metal copper layer of 5 μm on the outer surface when a current generating 1000 W of heat was applied to a comparative example in which the heat generating layer of a rice cooker pot was composed of only ferritic stainless steel.
In this case, heat generation of about 1100 W is obtained, and heat generation increases by about 10%.

The total calorific value of the pot of the first embodiment is obtained by adding the calorific values of the copper and the ferritic stainless steel layer. However, as shown in FIG. 3, the thickness of the nonmagnetic layer copper changes. As the temperature increases, the total calorific value also changes. Under the conditions of this comparative experiment, the total calorific value reached a maximum value when the thickness of the copper was around 5 μm, and a higher calorific value was obtained than in the comparative example using ferritic stainless steel alone. This example utilizes this fact. And a 5 μm copper layer disposed on the outer surface of the ferritic stainless steel.

In the first embodiment, the condition that 5 μm copper generates heat most efficiently is obtained. However, the maximum heat generation is obtained depending on the type of non-magnetic metal, the frequency used, the inductance of the induction heating coil and the like. Since the thickness of the non-magnetic metal varies, it is necessary to select the thickness of the non-magnetic metal according to the situation.

In any case, as shown in the first embodiment,
The rice cooker pan of the present invention can perform the rice cooking process while obtaining a high calorific value while using a non-magnetic metal for the electromagnetic induction heating unit, and has a beautiful appearance utilizing the color of the metal material. It becomes possible to provide a pot for a heating rice cooker.

[0028]

As described above, it is possible to obtain good heat generation while using a non-magnetic metal for the electromagnetic induction heating portion, and to produce electromagnetically cooked rice with beautiful appearance utilizing the color of the metal material. It is possible to provide a dexterity pot.

[Brief description of the drawings]

FIG. 1 is a sectional view of a rice cooker in which a pot according to a first embodiment of the present invention is used.

FIG. 2 is a cross-sectional view of the cooking cooker pan.

FIG. 3 is a graph showing a transitional characteristic of a calorific value according to a change in a copper thickness of a cooking rice cooker.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electromagnetic heating induction coil 2 Ferrite 3 Bottom bottom temperature detection sensor 4 Heating control board 5 Substrate cooling fan 6 Operation part 7 Heating plate 8 Steam cap 9 Pan 10 Aluminum 11 Ferritic stainless steel 12 Copper 13 Fluoro resin coating 14 Polyester protection coating

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Atsushi Fujita 1006 Kadoma Kadoma, Osaka Pref. Matsushita Electric Industrial Co., Ltd. Term (reference) 4B055 AA02 AA09 BA22 BA57 CA09 CB16 FA01 FB02 FB05 FB06 FC06 FC07 FC08 FD03 FE02

Claims (4)

[Claims] 1. A heating device comprising: an electromagnetically induced heat generating portion; and a heat transfer portion disposed inside the heat generating portion, wherein the heat generating portion includes a magnetic metal layer and a non-magnetic metal layer; The rice cooker pan, wherein the layer is disposed outside the magnetic metal layer and is thinner than the magnetic metal layer. 2. The non-magnetic metal layer has a thickness of from 0.1 to 0.1 at which the same skin electric resistance as that of iron is obtained.
2. The rice cooker pot according to claim 1, wherein the ratio is 2.0 times. 3. The rice cooker pot according to claim 1, wherein the nonmagnetic metal layer is formed by plating. 4. The rice cooker pot according to claim 1, wherein the nonmagnetic metal layer is subjected to at least one of an anodic oxide film treatment and a protective coating treatment.