JP2539914B2 - Cooker for microwave oven - Google Patents

Description

TECHNICAL FIELD The present invention relates to a microwave oven cooker, and more particularly to a microwave oven cooker having a microwave shielding lid with an insulating layer for preventing dielectric breakdown.

"Prior art" There are 2 items to use when cooking food in the microwave.
They are roughly classified into species.

One is that the container itself is hardly affected by microwaves and does not generate heat, and examples thereof include containers made of heat-resistant glass and containers made of plastics such as polypropylene and polycarbonate. These have only a function as a container.

The other one has a ferroelectric substance such as ferrite (Fe ₃ O ₄ ), and this ferroelectric substance is dielectrically heated by microwaves and has a function of heating the food by the heat. Examples of this are those disclosed in JP-A Nos. 60-223919 and 61-138028.

[Problems to be solved by the invention] Among the conventional utensils of this type, the latter is cooked with heat due to heat transfer from a microwave-heated dielectric, but is also heated by microwaves. For this reason, it was not possible to successfully cook a cooked product that had a property of being liquid before cooking and solidifying after cooking, and a property of easily absorbing microwaves.

Typical examples include fried egg, omelet, pancake, and okonomiyaki, which often boil and scatter during cooking, and become deformed compared to those cooked in a frying pan or the like. In addition, meat, hamburgers, etc. also contracted by heating with microwaves, and taste was always inferior to that in frying pan cooking.

On the other hand, the present inventors previously provided a microwave reflective or absorptive lid to cover the cooking surface from microwaves as described in Japanese Patent Application No. 63-84319. We devised to eliminate direct microwave irradiation.

However, in the invention of Japanese Utility Model Application No. 63-84319, between the microwave reflecting lid, that is, the metal lid and the metal dish, that is, the portion of the fluorine resin coating on the upper surface of the metal dish causes dielectric breakdown and sparks occur. There was a problem of damaging the fluororesin coating, the metal plate, and the lid.

In view of the above, the present invention was developed to solve such problems.

MEANS FOR SOLVING THE PROBLEMS That is, the present invention provides a metal dish having a fluorine resin coating on the upper surface thereof and a heating layer on the lower surface thereof which is heated by dielectric heating by microwaves, and the surface side of the metal dish is covered for cooking. An insulating layer having a microwave-reflecting lid for shielding an object from microwaves, and having a thickness of 3 mm or less at a portion which becomes a contact interface between the lid and the fluorine resin coating on the upper surface of the metal dish on the lid side. A cooking device for a microwave oven, characterized by being provided with.

Note that at least the following are included as the embodiments of the present invention.

B. A microwave oven cooker with an insulation layer thickness of 0.5 mm or less that prevents insulation breakdown.

The invention is described in detail below with reference to exemplary drawings,
However, the present invention is not limited to these examples.

As a result of intensive studies in consideration of such conventional problems, the present inventors prevent dielectric breakdown of a thickness of 3 mm or less at the contact interface between the microwave reflective lid and the fluororesin coating on the upper surface of the metal dish. It has been found that the provision of the insulating layer makes it possible to prevent the destruction due to the spark without significantly losing the microwave shielding property, and has completed the present invention.

1 (a) and 1 (b) are specific examples of the present invention. A fluororesin coating (6) is provided on the surface of the metal dish (1) so as to prevent the food from sticking during cooking.
A calorific value (2) is provided on the lower surface of the metal dish (1), and is configured to have an appropriate amount and composition.

The amount of heat generated (2) is dielectrically heated by microwaves, and the heat is transmitted to the metal dish (1) to heat the food on the fluororesin coating (6). At this time, the microwave shielding lid (4) is configured so that microwaves hardly enter the space where the food is present. Here, since (6) between the lid (4) and the metal dish (1) is a fluororesin coating, that is, an insulator, dielectric breakdown is likely to occur between (4)-(6)-(1), To prevent this, an insulating layer (5) is provided to prevent dielectric breakdown.

In FIG. 1, (3) is the coating, for example, silicone rubber coating, and (t) is the thickness of the thickness of the insulating layer for preventing dielectric breakdown.

"Function" The material of the microwave-reflective lid is selected from metals such as aluminum, aluminum alloys, iron, stainless steel, and copper, but it is a composite of plastic, glass, etc. with a metal plate, foil, etc. Good. Further, since the purpose is to shield microwaves, a mesh or a perforated plate may be used instead of a flat plate, and the diameter of the mesh or the holes may be any size that shields microwaves.

When the lid is formed in this way, the food that is trying to reach the food on the cooking surface from the front side of the metal dish is reflected by the lid, and the microwaves that wrap around to the back side of the metal dish are mainly on the back side of the metal dish. It will be absorbed by the absorber.

At this time, the metal portion of the lid and the metal dish are electrically charged because they are insulated by the fluororesin coating film, and therefore discharge occurs if there is a defect in the fluororesin coating film or if there is a particularly thin layer portion. .

Even if such a defect does not exist, since the fluororesin film is usually as thin as 15-40 .mu.m, a phenomenon (dielectric breakdown) in which the fluororesin film, which is an insulating layer, is destroyed and discharged is likely to occur.

This phenomenon is more likely to occur when the metal has protrusions or flaws, or when there is an air layer at the metal-insulator-metal interface.

Since such a state is likely to occur during cooking, an insulating layer capable of withstanding dielectric breakdown is provided at the contact portion of the lid with the cooking surface in order to avoid dielectric breakdown.

Any material may be used as long as it is an insulating material, such as rubber materials such as silicone rubber and fluororubber, fluororesins such as PTFE and FEP,
It is selected from a wide range of polyimide-based insulating varnishes, ceramics, etc., but the criteria for selection are required to be suitable for use in foods and to have excellent heat resistance. Further, it is desirable that it has good moldability and is rich in strength and toughness.

Structurally, if the thickness of the insulating layer that prevents such dielectric breakdown is too thick, microwaves penetrate from that portion, and the microwave shielding effect that is the initial purpose is weakened, which is not preferable.

FIG. 2 shows the result of an experiment conducted to find the upper limit of the thickness of the insulating layer that prevents dielectric breakdown. As shown in Fig. 2 (a), only the fluororesin coating (6) (about 20μ) is provided on the aluminum dish (1) to create a structure without a heating layer, and a heating element on the cooking surface. (8) was provided, the thickness of the insulating layer (5) for preventing dielectric breakdown was changed, and the temperature rise of the heating element on the cooking surface was measured. The results are shown in the graph of FIG. 2 (b), and it is considered that the higher the temperature rise, the more microwave leakage.

From this result, the thickness is 3 mm or less, preferably 0.5 mm or less. Further, since the lower limit of the thickness depends on the dielectric breakdown strength and the mechanical strength, it is necessary to design each material individually.

In this way, as a result of providing the microwave shielding cover and the insulating layer for preventing dielectric breakdown, the microwaves directly absorbed by the cooked food become very small even if they are directly absorbed, and the cooked food No sudden temperature rise. Then, under this condition, the microwave absorbed by the microwave absorber changes into heat, and the metal plate is heated by the heat conduction from below, resulting in the same cooking form as when baking in a heated frying pan. The cooked food on the surface cooks well.

And it becomes possible to use this device stably without causing dielectric breakdown.

"Examples" The present invention will be further described with reference to the following examples.

Example 1: Electrochemical etching is applied to the surface of an aluminum plate having an outer diameter of φ200 mm and a thickness of 0.8 mm to form fine irregularities, and a tetrafluoroethylene resin dispersion liquid is applied to the surface and baked at 380 ° C for 20 minutes. I went. Press molding was carried out with the surface coated with the tetrafluoroethylene resin as the upper surface to obtain an aluminum dish having an inner diameter of about 170 mm.

After applying a primer to the lower surface of this aluminum dish and baking it, Fe ₃ O ₄ (Ferrite D manufactured by Dowa Iron Powder Co., Ltd.
Silicone rubber (KE552BU manufactured by Shin-Etsu Chemical Co., Ltd.) containing 70% of DM-31, purity of about 95%, particle size of 200 μm or less) was molded into a diameter of 145 mm and a thickness of 0.5 mm as a heating layer, and the edge of the plate and aluminum plate 1.0mm thick silicone rubber (KE552
BU) was molded as a coating, a part of the coating was molded into a leg with a height of about 15 mm, press vulcanization was performed with a mold, and secondary vulcanization was performed after demolding to obtain a cooker body.

Next, from an aluminum plate with a thickness of about 0.7 mm, a diameter of 170 mm
A lid (4) with a height of about 35 mm is molded, and the lid has a thickness of 0.5 mm.
The silicone rubber packing (5) was formed into a shape as shown in FIG.

After putting the raw egg on the cooker body, cover it with a lid, and cover it with a microwave oven (High Cooker RE manufactured by Sharp Corporation).
When heated at -130, output of 500W) for 4 minutes, a fried egg with the same browning as the one baked in a frying pan was cooked up nicely. Dielectric breakdown (spark) did not occur either.

Example 2: A cooker main body and an aluminum lid were prepared in exactly the same manner as in Example 1, and a PTFE adhesive tape (thickness: 0.3 mm) was attached to the edge of the lid. The fried egg was cooked in a microwave oven, and fried egg with good browning was obtained. Dielectric breakdown did not occur either.

Example 3: A fried egg was cooked in the same manner as in Example 1 except that a PFE packing having a thickness of 2 mm was used, and the fried egg was similarly burnt. Dielectric breakdown did not occur either.

"Effects of the Invention" As described above, the cooker of the present invention has a structure in which a metal dish having a heating element that is dielectrically heated by microwaves, a microwave shielding metal lid, and an insulating layer that prevents dielectric breakdown are combined. Since the food is cooked mainly by the heat from the plate, it is possible to cook food that is not heated rapidly by microwaves in a microwave oven, and it is possible to use it stably without dielectric breakdown. Became.

[Brief description of drawings]

FIG. 1 is a cross-sectional view (FIG. (A)) of an example of the cooking device of the present invention and an enlarged view (FIG. (B)) of a portion of an insulating layer that prevents dielectric breakdown. FIG. 2 shows the results of an experiment conducted to find the upper limit of the thickness of the insulating layer that prevents dielectric breakdown. FIG. 2A shows the experimental method, and FIG. 2B shows the experimental result. It is the graph shown. FIG. 3 is for explaining the embodiment of the present invention, and is a cross-sectional view of an example in which an insulating layer for preventing dielectric breakdown is formed as a lid packing. (1) ... Metal dish, (2) ... Heating layer, (3) ... Coating, (4) ... Microwave shielding lid, (5) ... Insulation layer for preventing dielectric breakdown, (6) ) …… Fluorine resin coating,
(T) ... Thickness of the insulating layer that prevents dielectric breakdown.

Claims (1)

(57) [Claims] 1. A metal dish having a fluorine resin coating on the upper surface thereof and a heat generating layer on the lower surface thereof which is dielectrically heated by a micro liquid, and a microwave for covering the cooked material from microwaves by covering the surface side of the metal dish. A reflective lid is provided, and a thickness of 3 mm is provided on the lid side, which is a contact interface between the lid and the fluororesin coating on the upper surface of the metal dish.
A cooking device for a microwave oven, which is provided with an insulating layer for preventing the following dielectric breakdown.