JP5145840B2 - Pot for electromagnetic induction heating - Google Patents

Description

  The present invention relates to an electromagnetic induction heating pan and an electromagnetic induction heating rice cooker provided with the same.

  Conventionally, this type of pan, which is widely available to the general public, is manufactured using aluminum, stainless steel, titanium, iron, or a combination of 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 formed on the inner surface thereof. There are some that are laminated.

  As a characteristic of electromagnetic induction heating, a magnetic material with higher magnetism is more advantageous for heat generation due to electromagnetic induction, so a magnetic metal such as ferritic stainless steel is often used for the outer layer of the pan. Aluminum having a high thermal conductivity is often used for the purpose of quickly heat-diffusing and heating the food uniformly.

  Furthermore, these metal rice cooker pans are usually treated with a fluororesin coat on the inner surface to prevent the sticking of cooked rice, which improves the non-stickiness of rice. Yes.

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

  In an electromagnetic induction heating type rice cooker, further improving the exothermic property of the pan is cited as a problem, and as a means of improving the exothermic property from the material side of the pan, a material with high magnetic permeability or a specific resistance is used. Use of a material having a high value is an effective means.

  From these viewpoints, ferritic stainless steel represented by SUS430, etc., has been often used as the magnetic metal in the heat generating layer of the electromagnetic induction heating pan. In addition, there were cases where iron alloys such as permalloy were used and cases where copper plating was applied to the outer surface of the magnetic metal layer.

  However, in these materials, the specific resistance value and the relative permeability, which are factors that determine the electromagnetic induction heating 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.

  In rice cookers, it is a big challenge to improve the taste of rice. In rice cooker pots, the thickness of the base material is increased in order to distribute heat uniformly, and the base material is laminated in multiple layers. There was an example to let you.

  However, from the viewpoint of improving the taste of cooked rice, it is also one of the important conditions to make the pan thicker or multi-layered to make the heat around uniform, but apart from that, It is also an important condition in terms of improving the taste that the heat generated in the magnetic metal layer is transferred to the pan without being lost.

For this reason, what provided the heat insulation layer in the pan outer surface is known (for example, refer patent documents 1 and 2).
JP-A-10-211091 JP-A-11-56599

  However, in the conventional configuration, it is difficult to improve the taste simply by providing a heat insulating layer on the outer surface of the pan, and in the form of the heat insulating layer, since the heat insulating layer contains a hollow member, the adhesion between the resins is low. The heat insulation layer was brittle and had low durability such as wear resistance.

The present invention solves the above-mentioned conventional problems, and provides a pan for electromagnetic induction heating and an electromagnetic induction heating type rice cooker that improve heat generation of the pan, prevent heat from being lost, and improve durability. For the purpose.

In order to solve the above-mentioned conventional problems, the pan for electromagnetic induction heating of the present invention has a multilayer metal as a base material, and the outermost layer metal of the base material is composed of a magnetic metal, and the surface of the magnetic metal has a rough surface. In addition, the outer surface has a heat-insulating coating and a protective coating that are heat-resistant resin coatings, and the heat-insulating coating has hollow glass beads that are fillers with low thermal conductivity in the coating. 30 to 60% by weight, further adding a fibrous substance or talc , and the film thickness of the heat insulating film increases as it becomes the upper part of the pan, and the thermal conductivity is The lower filler contains the lower layer more than the upper layer of the coating .

  As a result, the heat generation property of the magnetic metal layer can be improved, and the heat insulating film and the protective film make it difficult for heat to escape and the durability can be improved.

  Moreover, the electromagnetic induction heating type rice cooker of this invention accommodates this electromagnetic induction heating pan so that attachment or detachment is possible.

  As a result, the heat generation of the pan is improved, the heat is not easily released, and the durability is improved, so that the taste and handling of rice are improved.

  The electromagnetic induction heating pan and the electromagnetic induction heating rice cooker of the present invention improve the heat generation of the pan, make it difficult to release heat, and can improve durability, and the rice taste and handleability as a rice cooker Will improve.

In the first aspect of the present invention, a multilayer metal is used as a base, the outermost layer of the base is made of a magnetic metal, the surface of the magnetic metal is subjected to a roughening treatment, and a heat-resistant resin coating is formed on the outer surface. A heat-insulating film and a protective film, and the heat-insulating film contains 30 to 60% by weight of hollow glass beads, which are fillers with low thermal conductivity , and is a fibrous material. Add talc ,
And the film thickness of the said heat insulation film increases as it becomes the upper part of a pan, and the lower layer contains more filler than the film upper layer for the said heat conductivity to become low . As a result, the heat generation property of the magnetic metal layer can be improved, and the heat insulating film and the protective film make it difficult for heat to escape and the durability can be improved.

In addition , since the heat-insulating coating and protective coating are heat-resistant resin coatings, heat-resistant protective coatings such as fluorine resins, silicone resins, epoxy resins, and polyethersulfone resins can be applied to the outside of the pan by painting. It can be processed.

Moreover , the heat-resistant resin film which is a heat-insulating film and a protective film is provided with a heat-insulating film to which a filler having low thermal conductivity is added, so that heat from the pan can be made difficult to escape.

In addition , among the heat-insulating film and protective film, the film thickness of the heat-insulating film to which the filler having low thermal conductivity is added increases the film thickness toward the top of the pan. The heat conductivity is kept low by the configuration, and the heat stored in the upper part of the pan during cooking is contained, so that the heat is uniformly transmitted to the food.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment)
The figure shows an electromagnetic induction heating pan and an electromagnetic induction heating rice cooker in an embodiment of the present invention.

  1 and 2 show an electromagnetic induction heating type rice cooker, and the rice cooker body 1 detachably stores a pot 9 and opposes the bottom portion 15 and the lower side surface 13 of the pot 9 and electromagnetic induction heating. The coil 3 is provided, and the pan 9 is configured to be heated by electromagnetic induction heating. A ferrite 4 for preventing magnetism is provided outside the electromagnetic induction heating coil 3. In addition, the side part lower part 13 shows the site | part of the height from the pan lower end to about 1/3 of the total height, and the upper part becomes the side part 14 from it.

  The lid 2 covers the upper opening of the pan 9 so as to be freely opened and closed, and an inner lid 7 is detachably installed on the inner surface of the lid 2.

  The pan bottom temperature detection sensor 8 is provided to face the bottom center portion 16 of the pan 9 and detects the temperature of the pan 9, and its output is input to the heating control board 5. The heating control board 5 has a microcomputer, an inverter circuit that supplies a high-frequency current to the electromagnetic induction heating coil 3, operates while being cooled by the board cooling fan 10, and based on an input from the operation unit 6, It is comprised so that rice cooking and a heat retention process may be performed by the program control by a microcomputer. The rice cooker body 1 also includes a steam cap 11 and an electromagnetic induction heating coil 12 that heats the inner lid 7.

  Here, as shown in FIG. 3, the pan 9 is made of a clad material in which a ferrite stainless steel having a thickness of 0.5 mm is used as a magnetic metal layer 17 and an aluminum 18 having a thickness of 1.0 mm is joined thereto. The magnetic metal layer 17 side is the outer surface and is pressed into a pan shape.

  A surface of the aluminum 18 on the inner surface of the pan 9 is treated with a two-layer fluororesin coat 19. The treatment of the fluororesin coat 19 is as follows.

  After the base material is press-molded into a pan shape and washed, sand blasting is applied to the surface of the aluminum 18 on the inner surface of the pan, and the surface roughness Ra is adjusted to 3 to 5 μm. Thereafter, the fluororesin, the adhesive component, the pigment, A liquid primer coating containing a glittering material as a coating film component was applied to a film thickness of about 10 μm after film formation, and dried at 100 ° C. for 20 minutes.

And when drying of the primer is completed and the base material temperature is sufficiently lowered, the water level line display portion is printed by pad printing on the primer on the side surface portion of the pan using a color different from the color of the primer, As the lower top coat treatment, a fluororesin powder coating material containing no additives such as pigments and glittering materials was applied on the primer and the water level line display portion so as to have a film thickness of 35 μm after film formation. At this time, the fluororesin used was a mixed powder of PTFE: PFA = 2: 8, and this powder coating was applied, followed by baking at 380 ° C. for 20 minutes to form a film on the fluororesin coat 19.

  On the other hand, on the outer surface of the magnetic metal layer 17 constituting the outer layer of the pan base material, the roughened surface 20 is formed by adjusting the surface roughness Ra to 0.5 to 5 μm by shot blasting, and thereafter As shown in FIG. 4, an epoxy / silicone resin paint containing a filler 21 made of hollow glass beads having an average particle diameter of 30 μm as a filler having a low thermal conductivity is applied to the surface of the magnetic metal layer 17 as a first layer. The heat insulating coating 27 (FIG. 3) having a thermal conductivity of 1/100 or less of that of the magnetic metal layer 17 was applied. Further, a protective film 28 (also FIG. 3) which is a heat-resistant resin film is provided on the upper layer. For the purpose of improving the adhesion between the magnetic metal layer 17 and the epoxy / silicone resin paint containing the filler 21 that reduces the thermal conductivity, a thin film is formed between the roughened surface 20 of the magnetic metal layer 17. A primer layer may be provided. Since the heat-insulating coating 27 and the protective coating 28 are heat-resistant resin coatings, a heat-resistant protective coating such as a fluorine resin, a silicone resin, an epoxy resin, or a polyether sulfone resin is applied by panning. It can be processed on the outer surface.

  Moreover, the roughened surface 20 of a base material expands a surface area 1.05-2.0 times compared with the time of un-processing, and raises the electrical resistance and magnetic permeability of a surface part. That is, the surface area of the magnetic metal is increased by roughening the surface by blasting, but this increases the electrical resistance value of the magnetic metal surface layer, and at the same time, the blasting material is applied to the surface of the magnetic metal layer. Since the permeability of the magnetic metal is changed by the impact struck, the heat generation property of the magnetic metal layer is improved as a result.

  In the roughened surface 20, when the increase in the surface area is less than 1.05 times, no particular effect on the heat generation is seen, and when it is larger than 2.0 times, the roughness of the magnetic metal surface becomes too large, Since the surfaces of the heat insulating coating 27 and the protective coating 28 provided on the surface become rough, it is desirable that the range is 1.05 to 2.0 times.

  Specifically, a multilayer metal such as a clad material obtained by joining a heat-conductive metal such as aluminum and a ferritic stainless steel, which is a magnetic metal having excellent electromagnetic induction heating characteristics, is used as the base material of the pan 9. Then, the outer surface of the pan 9 obtained by molding this, that is, the surface of the magnetic metal layer 17 is roughened by shot blasting with alumina particles or the like so that the surface roughness Ra becomes 0.5 to 5 μm. To implement.

  Next, a heat insulating film 27 and a protective film 28 are formed on the surface of the roughened magnetic metal layer 17, but preferably the heat insulation has a thermal conductivity of 1/100 or less of the magnetic metal layer. The characteristic film 27 is provided. In addition, this heat insulation film 27 is provided even to the flange part 26 of the pan 9 in this Embodiment.

  When the base material is aluminum and ferritic stainless steel, the thermal conductivity of the ferritic stainless steel is about 26 W / m · k, and therefore, a heat insulating coating 27 of 0.26 W / m · k or less is provided. However, with respect to the thickness, it is preferable that the thickness is about 100 μm or more except for the portion where the pan bottom temperature detection sensor 8 abuts, and it is desirable to increase the thickness toward the upper portion of the pan.

  That is, the epoxy / silicone resin paint is coated after baking to have an average film thickness of 100 to 200 μm at the bottom 15, 400 to 550 μm at the side 14, and 200 to 300 μm at the bottom 13. In this case, the thickness of the bottom portion 15 is 1.8 to 5.5 times. The amount of hollow glass beads contained in the coating film is 50% by weight, and the thermal conductivity of this coating film is 0.05 W / m · k.

  According to this configuration, the thickness of the heat-insulating coating layer 27 containing the filler that reduces the thermal conductivity gradually increases from the bottom 15 of the pan 9 to the side, and the thermal conductivity is particularly low at the side 14. By suppressing the heat stored in the upper part of the pot during cooking, the heat is evenly transmitted to the rice and the taste can be improved. On the contrary, the heat insulation coating layer 27 containing the filler that reduces the thermal conductivity becomes thinner toward the side lower portion 13 and the bottom portion 15, but these portions are electromagnetic induction heating coils arranged inside the rice cooker body 1. 3 is a portion where the magnetic metal layer of the pan 9 generates heat and its peripheral portion, and the heat insulating coating layer 27 is heated by returning a too thick heat insulating coating 27 on the surface of this portion. Since uniform heating is inhibited, there is a strong possibility of adversely affecting the taste as a result, so that the film is made relatively thin.

  However, in the vicinity of the pan bottom, in particular, in the part that opposes the electromagnetic induction heating coil 3, when the film is made thinner than the above-described film thickness, the heat generated in the magnetic metal layer 17 is cooled by the air on the outer surface of the pan and heated. Therefore, it is not desirable to make the film thinner than this.

  It is important that the amount of hollow glass beads is 30 to 60% by weight in the coating film. However, when this concentration is reached, the amount of resin in the coating film is relatively small, and the coating film becomes uncoordinated and brittle. Therefore, it is possible to add about several percent by weight of potassium titanate fiber or talc into the paint to improve the unity of the resin.

  Since the epoxy / silicone resin layer containing the hollow glass beads as the filler 21 has a low thermal conductivity, the resin layer is applied to the bottom center portion 16 where the pan bottom temperature detection sensor 8 provided in the rice cooker body 1 contacts. In this case, the temperature could not be detected sufficiently so that it was not painted.

  Next, an epoxy / silicone resin paint is applied to the upper layer of the first layer 22 as the second layer 23. In addition to the resin component and the pigment as the main components, this paint adds phenol carbide particles 24 having an average particle size of 50 μm. It is contained as particles.

  The second layer 23 was coated on the entire outer surface of the pan so as to have a thickness of about 40 to 120 μm after film formation. However, since the added phenol carbide particles 24 have an average particle size of 50 μm, the pan bottom temperature detection sensor 8 is applied. When the bottom center portion 16 in contact with the pan is coated, good contact between the pan bottom temperature detection sensor 8 and the pan 9 is hindered, and the temperature detection may be disturbed. 16 was not painted.

  The phenol carbide particles 24 have high hardness, and when added to the coating film, the wear resistance of the coating film can be greatly improved, and the apparent hardness of the coating film can be improved. Further, the second layer 23 acts as a protective coating 28 for the first layer 22 and can suppress abrasion during actual use or damage caused when the pan 9 is struck against another object.

  The concentration of the phenol carbide particles 24 in the coating film is desirably 10 to 40% by weight. However, when the concentration is less than 10% by weight, it is difficult to obtain an effect such as an improvement in wear resistance. This is because the surface of the film becomes excessively rough.

  In the present embodiment, the phenol carbide particles 24 are used as the additive, but glass particles, ceramic particles such as silicon carbide and alumina, diamond particles, and the like can also be used as the additive.

These materials are also high in Mohs hardness, withstand high temperatures, and are highly stable against various chemicals, so they are added to the protective coating 28 of the pan 9 exposed to high temperatures during cooking and various seasonings. Therefore, it is a suitable material for improving the wear resistance. The heat-resistant resin film that is the protective film 28 may have a multilayer structure of two or more layers. In the case of one layer, the additive is added to the layer, and in the case of two or more layers, the additive is added to at least one of the outermost layer and the outermost layer.

  Next, an epoxy / silicone resin paint containing a black pigment is applied to the bottom center portion 16 where the pan bottom temperature detection sensor 8 comes into contact and its periphery so as to have a thickness of about 20 μm after film formation. If it is similar to the color tone of, you can maintain a uniform color tone of the entire outer surface of the pan.

  After that, as the third layer 25, a silicone-based transparent coating was applied to the entire outer surface of the pan so as to have a film thickness of about 20 μm, and mica and aluminum flakes were added to the coating as a glittering material. In addition, since it is a silicone-based paint and has excellent non-adhesiveness, there is an advantage that dirt hardly adheres in actual use.

  In the present embodiment, the first layer 22, the second layer 23, the coating of the bottom center portion 16 in contact with the pan bottom temperature detection sensor 8, and the third layer 25 are coated on the outer surface of the pan in this order. The layer 22 is a heat insulating film 27, and the second layer 23 and the third layer 25 are a protective film 28 of the heat insulating film 27.

  These coatings may be continuous coating at appropriate intervals, or may be provided with a drying time of about 100 ° C. for 10 minutes after each coating, but finally at 200 to 250 ° C. for 15 to 30 minutes. Firing was performed to form an outer coating. Needless to say, these coating conditions can be changed depending on what kind of resin is used.

  Here, the pan 9 of the present embodiment and the comparative example pan of the same shape, which is based on a matching material of aluminum and ferritic stainless steel of the same thickness and whose outer surface is not subjected to any treatment A comparative experiment was performed.

  When 1 L of water is put in the pan of this embodiment and the pan of the comparative example and placed on an electromagnetic induction heating cooker and operated at 100 V, the generated power is improved by about 5% as shown in (Table 1). However, this is the effect obtained as a result of the increase in the area subjected to magnetic force due to the roughening treatment applied to the outer surface of the pan of the present embodiment, and the change in the electrical resistance and permeability of the surface of the magnetic metal layer. It is.

  As the surface layer portion of the magnetic metal has a larger calorific value as a characteristic of electromagnetic induction heating, in particular, it is possible to realize efficient heat generation by roughening the surface layer and increasing the current flowing area, As a result, water could be boiled faster.

  Next, (Table 2) shows the taste results when cooking rice in the pan in the present embodiment and the pan (Comparative Examples 2 to 7) in which the film thickness configuration of the first layer 22 was changed.

  In (Table 2), it shows the result of the rice when the pot for 5.5 go rice cooking is put in the rice cooker body 1 and 3 go rice is cooked normally. In the taste determination, ◎ means that the taste has improved significantly over the standard, ○ means that the taste has improved over the standard, Δ means a taste at the same level as the standard, and X means below the standard.

  The taste is determined by comprehensively judging the taste, aroma, stickiness, hardness, bulging degree, etc. of the cooked rice.

  In Comparative Examples 2 to 8, the addition amount and particle size of the hollow glass beads that are the filler 21 of the first layer 22 are all the same as in the present embodiment.

  As shown in (Table 2), in comparison with the present embodiment, in the case where the film thickness or the balance of the film thickness is changed, the taste better than the standard is not obtained in any case.

  From the above results, it can be seen that in order to obtain a good taste, the heat-insulating coating 27 having a low thermal conductivity must be made to have an appropriate thickness depending on the portion of the pan, and the thickness is generally the film in the present embodiment. Although it is a thickness, as a result of verification, as shown in (Table 3), this thickness slightly changes depending on the thermal conductivity of the first layer 22.

  In any case, in order to obtain a good taste, the film thickness of the heat insulating coating 27 containing the filler 21 that lowers the thermal conductivity is set to be relatively thin at the bottom 15, and as it becomes the top of the pan It is important that the thickness of the side surface portion 14 be increased by 1.8 times or more compared to the thickness of the bottom portion 15, but it should not exceed 5.5 times at the maximum.

  As described above, the electromagnetic induction heating pan in the present embodiment is subjected to roughening treatment on the surface of the magnetic metal, and as a result of expanding the surface area to receive the generated magnetic force, the heat generation of the magnetic metal layer is improved, By providing the heat insulating coating 27 and the protective coating 28 on the outer surface of the magnetic metal layer, it is difficult for heat to escape and the durability can be improved.

  In addition, the electromagnetic induction heating rice cooker in the present embodiment is detachably accommodated with this electromagnetic induction heating pan, so that the heat generation of the pan is improved, heat is not easily released, and durability is high. This increases the taste and handling of rice.

  The heat-resistant resin film as the heat-insulating film 27 and the protective film 28 has a multi-layer structure, and at least one of the lower layers other than the outermost layer is added with a filler that lowers the thermal conductivity. It is also possible to make the heat insulating film 27 and to make the heat insulating film 27 to which this filler is added thicker than normal coating.

  More specifically, the heat-insulating coating 27 to which a filler for decreasing the thermal conductivity is added is preferably the first layer provided immediately above the roughened surface of the magnetic metal layer, and the first layer is hollow. It contains more fillers, such as glass beads or porous carbon particles, that reduce the thermal conductivity than the upper layer of the second layer or more, and is thickened.

  In the case of hollow glass beads, the first layer on the surface of the magnetic metal is a layer containing 30 to 60% by weight of an average particle size of 10 to 80 μm and a specific gravity of 0.05 to 0.5 g / ml in the coating film. It is desirable to provide a thickness of 100 μm or more, and it is desirable to increase the film thickness toward the top of the pan.

  If the hollow glass beads are less than 30% by weight, the performance of sufficiently confining heat in the pan is not exhibited, and if it exceeds 60% by weight, the coating film is brittle and does not have a function as a coating. % Is desirable.

  In particular, when the first layer contains a large amount of a hollow filler, it is necessary to provide the protective coating 28 that protects the first layer in the second layer or more. It is desirable to reduce or not add to the proportion of filler that reduces thermal conductivity. This is because the purpose of improving the strength and protecting the first layer from abrasion and impact is higher than the purpose of lowering the thermal conductivity in the upper layer part than the second layer.

  As described above, the pot for electromagnetic induction heating according to the present invention can be used as a pot for various induction heating cookers because the heat generation of the pot is improved, heat is not easily released, and durability can be improved. can do. Moreover, since the taste and handleability of rice are improved as an electromagnetic induction heating type rice cooker, it can be applied to electromagnetic induction heating type rice cookers in general.

Sectional drawing of the rice cooker in embodiment of this invention Cutaway cross-sectional view of the same rice cooker pot Enlarged sectional view of part A in FIG. Expanded cross-sectional view of the base material of the rice cooker pot

DESCRIPTION OF SYMBOLS 1 Rice cooker main body 3 Electromagnetic induction heating coil 8 Pan bottom temperature detection sensor 13 Side lower part 14 Side part 15 Bottom part 16 Bottom center part 17 Magnetic metal layer 18 Aluminum 19 Fluorine resin coat 20 Roughening surface 21 Filler 22 1st layer 23 2nd layer 25 3rd layer 27 Insulating coating 28 Protective coating

Claims (1)

A multi-layer metal is used as a base material, and the outermost metal layer of the base material is composed of a magnetic metal, and the surface of the magnetic metal is subjected to a roughening treatment. A protective coating, wherein the heat-insulating coating contains 30-60% by weight of hollow glass beads which are fillers with low thermal conductivity , and further contains a fibrous substance or talc ; and The film thickness of the heat insulating film increases as it becomes the upper part of the pan, and the lowering of the thermal conductivity is that the lower layer contains more of the lower layer than the upper layer of the film. A pot for electromagnetic induction heating.