JP2010022448A - Rice cooker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rice cooker of electromagnetic induction heating type which has high heating property and excellent durability. <P>SOLUTION: The rice cooker comprises a pot 3 stored in a rice cooker body, an electromagnetic induction coil used as a heating means for heating the pot 3 by electromagnetic induction, and a lid for opening and closing upper opening parts of the rice cooker body and the pot 3. The pot 3 has an inner layer composed of a metal having good heat conductivity and an outer layer composed of a base which is formed of multilayer metal formed by stacking magnetic metal 6. Surface roughening treatment 9 is applied at least partially to the surface of the magnetic metal 6 and copper plating 8 is applied to the magnetic metal 6. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to an electromagnetic induction heating type rice cooker, and more particularly to a rice cooker obtained by improving a pot used for the rice cooker.

  2. Description of the Related Art Conventionally, rice cooker pots that are widely available to the general public are manufactured using aluminum, stainless steel, titanium, iron, copper, or a composite material laminated by combining these as a base material.

  In particular, in a pan used in an electromagnetic induction heating type rice cooker, a magnetic metal such as ferritic stainless steel is arranged on the outer layer of the pan base material, and aluminum is laminated on the inside thereof, or in some cases, stainless steel is further applied on the inner surface thereof. There are things that are stacked.

  As the characteristics of electromagnetic induction heat generation, magnetic materials such as ferritic stainless steel are often used for the outer layer of the pan because a highly magnetic material is more advantageous for heat generation due to electromagnetic induction, and for the inner layer of the pan High heat conductivity, that is, heat-conducting aluminum is frequently used for the purpose of quickly performing heat diffusion and uniformly heating the food.

  Furthermore, these metal pans adhere to the cooked food as it is, and in order to prevent this, a fluororesin coat is often treated on the inner surface to improve the non-adhesiveness to the cooked food. Yes.

  The fluororesin coat treated on the inner surface of the pan is usually one having a one-layer structure, or two or more layers, but good non-adhesiveness, high durability and good From the viewpoint of obtaining an appearance, it is preferable to use a fluororesin coat having two or more layers.

  In the pan of the electromagnetic induction heating type rice cooker, it has been mentioned as a conventional problem to further improve the heat generation, and as a means of improving the heat generation from the material surface of the pot, use a material having a high relative permeability, It is an effective means to use a material having a high specific resistance value.

  From these viewpoints, ferritic stainless steel such as SUS430 has been used as the magnetic metal for the heat generating layer of the pan. However, the nonmagnetic layer is treated on the outer surface of the magnetic metal layer to obtain higher heat generation. There was a case of trying (see, for example, Patent Document 1).

However, in these materials, the specific resistance value and relative permeability, which are factors that determine the electromagnetic induction heat generation characteristics, are variable factors during the molding process, but are stable as the material-specific factors after molding to the pan. However, there was a limit to improving the heat generation from the material side.
Japanese Patent Laid-Open No. 2001-14558

  The object of the present invention is to solve these conventional problems, and to improve the heat generation and durability of the pan of the electromagnetic induction heating rice cooker.

In order to achieve the above object, the present invention comprises a pan housed in a rice cooker body, heating means for heating the pan by electromagnetic induction, and a lid body for opening and closing the rice cooker body and the upper open part of the pan. The pan is composed of a multi-layer metal in which the inner layer is a heat conductive metal and the outer layer is laminated with a magnetic metal, and at least part of the surface of the magnetic metal is roughened. Then, a copper plating layer is applied.

  Thereby, the exothermic property and durability of a pan can be improved.

  Since the electromagnetic induction heating rice cooker of the present invention can enhance the heat generation of the pan used for it, it can realize efficient rice cooking and suppress deterioration of the plating layer due to heat generated during rice cooking, so it is durable Can also improve the performance.

  The present invention comprises a pan housed in a rice cooker body, heating means for heating the pan by electromagnetic induction, and a lid body for opening and closing the rice cooker body and the upper open part of the pan, The inner layer is made of a metal with good thermal conductivity and the outer layer is made of a multilayer metal with a magnetic metal laminated on it. The surface of this magnetic metal is subjected to roughening treatment and then copper plated. It has been treated.

  And the said surface roughening process set surface roughness Ra to 0.5 micrometer or more and 3.0 micrometers or less.

  More specifically, the base material is a multilayer metal such as a clad material obtained by joining a ferritic stainless steel, which is a magnetic metal having excellent electromagnetic induction heat generation properties, and a metal having good thermal conductivity such as aluminum, A roughening process is carried out so that the surface roughness Ra becomes 0.5 to 3 μm by shot blasting with alumina particles or the like on the outer surface of the pan obtained by molding this, that is, the surface of the magnetic metal layer. .

  Although it is effective that the part to be roughened is processed to a part facing a coil disposed in the electromagnetic induction heating rice cooker body, it can be processed to another part.

  However, care should be taken because the temperature detection may be shifted if processing is performed on the part where the temperature sensor for detecting the temperature of the electromagnetic induction heating rice cooker pan contacts.

  Next, a layer containing copper as a main component is provided on the surface of the roughened magnetic metal layer by plating. Preferably, the plating layer is in the range of 1 to 10 μm.

  In general, when performing electromagnetic induction heat generation, it is common to use a metal material having a high specific resistance value for the heat generating part of the pan. For example, it can be said that 430 stainless steel and iron, which are typical ferritic stainless steels, have high specific resistance values and are suitable for electromagnetic induction heat generation.

  On the other hand, non-magnetic metals such as aluminum and copper have a low specific resistance value and are usually unsuitable for electromagnetic induction heat generation.

  This is because when a magnetic field is applied to a non-magnetic metal, a repulsive magnetic field is generated in the non-magnetic metal, a repulsive current flows, the magnetic field cannot pass through the non-magnetic metal, and an efficient heat generation effect due to electromagnetic induction cannot be expected. It is.

  However, as these nonmagnetic metal layers are also made thinner, the skin resistance eventually increases and electromagnetic induction heat generation becomes possible. That is, if the non-magnetic metal layer is sufficiently thin, the skin resistance is increased, so that a repulsive magnetic field is hardly generated, and the magnetic field easily passes through the non-magnetic metal.

  The eddy current is also generated in the stainless steel due to the magnetic field passed therethrough, and both the nonmagnetic metal layer and the magnetic metal layer such as stainless steel generate heat.

  The present invention utilizes this phenomenon, and by combining the nonmagnetic metal layer and the magnetic metal layer, even when the nonmagnetic metal is on the outer surface of the pan, it is more efficient than a simple magnetic metal layer single layer. It generates heat and cooks rice.

  Incidentally, the oscillation frequency band used in a normal electromagnetic induction cooker is about 20 to 40 kHz. In this frequency band, the copper thickness is 1 to 10 μm, and this effect is remarkable.

  In addition, in the present embodiment, the surface roughness Ra is performed on the surface of the magnetic metal so that the surface roughness Ra is 0.5 to 3 μm. Since the resistance near the surface of the metal layer is improved, the heatability is further improved.

  In addition, you may process the fluorine resin coat for improving non-adhesiveness to the pot inner surface.

  According to this configuration, since the surface of the magnetic metal is roughened, the surface area that receives the magnetic force generated from the rice cooker body is increased and the electrical resistance is increased. As a result, the heat generation of the magnetic metal layer is improved. In addition, since a plating layer containing copper as a main component is provided on the outer surface of the magnetic metal layer, a cooking pot with higher heat generation can be obtained.

  The pan is formed by subjecting a disk-shaped multilayer metal base material, which has been subjected to a surface roughening treatment, to which a copper plating treatment layer has been applied, to the outer periphery on the copper plating treatment layer side.

  Although it is effective that the part to be roughened on the surface of the magnetic metal is processed to a part facing the electromagnetic induction coil, it is also possible to process to another part.

  However, note that if a rough surface treatment is applied to the part where the temperature sensor that detects the temperature of the pan comes into contact with the temperature sensor that detects the temperature of the pan, contact with the sensor may be disturbed and temperature detection may be shifted. Cost.

  In addition, press processing into a pan shape, at this time the portion corresponding to the side surface portion of the pan is strongly rubbed with the mold by press processing, so if the roughening treatment with strong unevenness is applied to this portion, Since production defects such as scratches also occur, it is desirable not to perform the surface roughening treatment on the portion corresponding to the side surface portion or to make the surface roughness Ra within 1.0 μm.

  Next, a layer containing copper as a main component is provided on the surface of the roughened magnetic metal layer by plating. Preferably, the plating layer is in the range of 1 to 10 μm.

  Circle material with copper as the main component produced through the above steps is formed into a predetermined pan shape by pressing, but the surface roughness caused by pressing is a polishing cloth, etc. Polishing and finishing to a mirror surface improves the appearance quality.

  After this, the inner surface of the pan can be processed with fluororesin, but since the fluororesin processing usually includes a process of processing at a high temperature around 400 ° C., the plating layer mainly composed of copper on the outer surface of the pan remains as a high temperature process. If it is passed, it will undergo oxidative degradation.

  Therefore, for example, a firing process is performed in a furnace in which the oxygen concentration is lowered in a nitrogen atmosphere or a reducing gas atmosphere.

  According to this configuration, since the surface of the magnetic metal is roughened, the surface area that receives the magnetic force generated from the rice cooker body is increased and the electrical resistance is increased. As a result, the heat generation of the magnetic metal layer is improved. In addition, since a plating layer mainly composed of copper is provided on the outer surface of the magnetic metal layer, it can be made a pan with higher heat generation, and a processing step for processing a material plated in advance on a circle material Can be simplified.

  Preferably, a heat resistant coating is applied to the outer surface of the copper plating layer.

  If the outer surface of the pan has a copper-based layer, the copper will undergo oxidative degradation due to the high temperature during rice cooking and the appearance will gradually deteriorate. A heat-resistant coating is processed.

  The plated layer mainly composed of copper has a copper-specific bronze color, but if it is desired to maintain this color in appearance, the heat-resistant coating needs to be treated with a clear coating.

  In addition, by adding fine particles such as carbide particles, ceramic particles, glass particles, and diamond particles to the heat resistant coating, it is possible to improve the wear resistance and suppress the wear of the coating.

  Furthermore, since the magnetic metal layer is roughened, the surface of the plating layer mainly composed of copper also has an appropriate roughness, and the heat-resistant coating has higher adhesion due to the anchor effect. Therefore, durability of the coating can be improved.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In addition, this invention is not limited by this Embodiment.

(Embodiment 1)
In FIG. 1, the rice cooker main body 1 includes a pan 3 that generates and heats electromagnetic induction by an electromagnetic induction coil 2, and a temperature detection sensor 4 is disposed to detect the temperature of the bottom of the pan 3. It is.

  The upper open portion of the rice cooker body 1 and the pan 3 is opened and closed by a lid 5.

  The electromagnetic induction coil 2 is disposed corresponding to the bottom of the pan 3 and below the outer periphery. Of course, the electromagnetic induction coil 2 at the bottom is provided so as to avoid the temperature detection sensor 4 and surround it.

  As shown in FIGS. 2 and 3, the pan 3 is formed by laminating a thermally conductive metal layer 7 made of aluminum having a thickness of 1.0 mm inside a magnetic metal layer 6 made of ferritic stainless steel having a thickness of 0.5 mm. A multi-layered metal is used as a base material.

  Then, the copper plating layer 8 is applied to the outer periphery of the magnetic metal layer 6. Prior to the plating process, the magnetic metal layer 6 side is subjected to a blasting process using alumina particles, and the surface roughness Ra is set. A roughened surface 9 having a thickness of about 2 μm was provided.

  In order to ensure adhesion between the magnetic metal layer 6 and the copper plating layer 8, it is desirable to form a nickel strike layer having a thickness of approximately 0.1 μm in a nickel chloride bath.

Thereafter, the copper plating layer 8 is formed in a copper sulfate bath, and the thickness of the copper plating layer 8 at this time is approximately 3 to 8 μm.

  The copper plating layer 8 is coated with a clear coat layer 10 mainly composed of a heat-resistant resin and subjected to a baking treatment at 180 ° C. for 15 minutes.

  In order to improve the wear resistance, glass particles 11 having an average particle diameter of 10 μm were added to the clear coat layer 10 so that the concentration in the coating film was 3% by weight.

  A two-layer fluororesin coat layer is formed on the surface of the thermally conductive metal layer 7 made of aluminum on the inner surface of the pan 3.

  That is, the surface of the thermally conductive metal layer 7 is sandblasted and adjusted so that the surface roughness Ra is 3 to 5 μm, and then the fluororesin, the adhesive component, the pigment, and the glittering material are applied as coating film components. The formed liquid primer coating was applied to a film thickness of about 10 μm after film formation and dried at 100 ° C. for 20 minutes.

  When the drying of the primer is completed and the substrate temperature is sufficiently lowered, a film coating of fluororesin powder containing no additives such as pigments and glittering materials as a top coat treatment is formed on the primer to a film thickness of 35 μm. Then, it was coated and fired at 400 ° C. for 15 minutes in a nitrogen atmosphere.

  The pan 3 is formed by laminating a magnetic metal layer 6 and a heat conductive metal layer 7 and processing the disk-shaped metal base 12 of FIG. 4 formed with a copper plating layer 8 and a fluororesin coating layer by pressing or the like. It is configured as follows.

  Here, the experiment was carried out using a laminated material of aluminum and ferritic stainless steel having the same thickness as that of the pan of the present embodiment as a base material and a pan having the same shape plated with copper on the outer surface thereof as a comparative example.

  When putting 1500 g of water at 20 ° C. into the pot of this embodiment and the pot of the comparative example and setting it in an electromagnetic induction heating type rice cooker, energizing continuously until the integrated power amount becomes 120 Wh at a voltage of 100 V, and the heating efficiency is measured. As shown in Table 1, the heating efficiency was improved by about 1.5%.

  This is an effect obtained as a result of the increase in the area subjected to the magnetic force and the change in the electrical resistance of the surface of the magnetic metal layer due to the roughening treatment applied to the outer surface of the pan of the present embodiment.

  Since the heat generation amount of the magnetic metal surface layer is larger as a characteristic of electromagnetic induction heat generation, efficient heat generation can be realized by roughening the surface layer and increasing the area where current flows. In combination with the plating layer, the effect was further improved, and as a result, the heating efficiency could be improved.

  Note that the surface roughness Ra of the roughened surface 9 was not significantly different in the range of 0.5 μm to 3.0 μm.

(Embodiment 2)
5 and 6 show the second embodiment, and the difference from the first embodiment is that the copper plating layer 8 is limited to the lower part of the outer periphery of the pan 3 and the bottom, that is, the part corresponding to the electromagnetic induction coil. In addition, the clear coat layer 10 is provided.

  Other configurations are the same as those of the first embodiment, and those of the first embodiment are used for specific description.

  Therefore, the copper plating layer 8 can be formed only in the central portion of the disk-shaped metal substrate 12, and this can be pressed to form the pan 3 as shown in FIG.

  As described above, the rice cooker according to the present invention performs the roughening treatment on the surface of the magnetic metal layer that constitutes the outer layer of the pan base material, and the copper plating layer is treated on the roughening treatment surface. Heat generation is possible and can be diverted to cooking pots other than cooking rice.

Sectional drawing of the rice cooker in Embodiment 1 of this invention. Partial enlarged sectional view of a pan used in the rice cooker The principal part expanded sectional view of the pan used for the rice cooker Perspective view of disk-shaped substrate before processing into pan Front view of the rice cooker pan of the present invention The perspective view of the disk-shaped base material before processing into the pan in Embodiment 2

Explanation of symbols

1 Rice cooker body 2 Heating means (electromagnetic induction coil)
3 Pan 5 Lid 6 Magnetic Metal Layer 7 Thermal Conductive Metal Layer 8 Copper Plating Layer 9 Roughening Surface 10 Clear Coat Layer

Claims (4)

A pan housed in the rice cooker body; heating means for generating heat by electromagnetic induction; and a lid body for opening and closing the rice cooker body and the upper open part of the pan. The base metal is composed of a multi-layer metal made of a conductive metal and a magnetic metal laminated on the outer layer. At least a part of the surface of the magnetic metal is subjected to a roughening treatment and a copper plating layer is applied. Cooker. 2. The rice cooker according to claim 1, wherein the surface roughness Ra is set to 0.5 μm or more and 3.0 μm or less. The rice cooker according to claim 1 or 2, wherein a pan is formed by drawing a disk-shaped multilayer metal base material having a copper plating treatment layer after roughening treatment so that the copper plating treatment layer side is the outer periphery. . The rice cooker according to any one of claims 1 to 3, wherein a heat-resistant coating is applied to the outer surface of the copper plating layer.

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