JPH02309129A - Cooking appliance for electronic oven - Google Patents

Abstract

PURPOSE:To make it possible to cook a cooking material unfit for rapid heating by a microwave, by an electronic oven, and to prevent occurrence of dielectric breakdown by combining a metal plate having a heater heated dielectrically by the microwave, a metal cover for shielding the microwave and a dielectric breakdown preventing layer together. CONSTITUTION:A metal plate 1 on the surface of which a fluoroplastic film 6 is provided and to which a cooking material does not adhere in cooking has a heating layer 2 provided on the lower surface thereof. The heating layer 2 is heated dielectrically by a microwave, the heat thereof is propagated to the metal plate 1 and thereby the cooking material on the fluoroplastic film 6 is heated. On the occasion, the microwave is hardly allowed to enter a space wherein the cooking material is placed, by a cover 4 for shielding the microwave. Since the substance 6 provided between the cover 4 and the metal plate 1 is the fluoroplastic film, i.e. an insulating substance, in this constitution, dielectric breakdown tends to occur between 4 and 6 and between 6 and 1. In order to prevent said breakdown, a dielectric breakdown preventing layer 5 is provided. Thereby the breakdown due to a spark can be prevented without losing a shielding property against the microwave in a large degree.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a microwave oven cooker, and more particularly to a microwave oven cooker having a dielectric breakdown prevention layer on the lid for shielding microwaves.

``Prior Art'' Utensils used when cooking food in a microwave oven are roughly divided into two types.

One is that the utensils themselves are hardly affected by microwaves and do not generate heat, such as utensils made of heat-resistant glass, utensils made of plastics such as polypropylene, polycarbonate, etc. These serve only as containers.

The other one has a ferroelectric material such as ferrite (Fe, 04), and this ferroelectric material is dielectrically heated by microwaves.
It has the function of heating the food with that heat. Examples of this include JP-A-60-223919 and JP-A-61-1.
There is one shown in Publication No. 38028.

``Sequence of tasks to be solved by the invention'' Among the conventional utensils of this type, the latter was capable of browning cooking by heat transfer from a dielectric material heated by microwaves.
At the same time, it is also heated by microwaves, so it has been difficult to cook foods that are liquid before cooking and solidify after cooking, and which tend to absorb microwaves.

Typical examples include fried eggs, tamagoyaki, pancakes, and okonomiyaki, which often bump and scatter during cooking.
The result will be deformed compared to those cooked in a frying pan or the like. In addition, swords, hamburgers, etc. also shrink when heated by microwaves, making them taste inferior to those cooked in a frying pan.

On the other hand, the present inventors have previously proposed
As described in No. 9, we have devised a method to eliminate direct irradiation of microwaves by providing a microwave reflective or absorbent lid that covers the cooking surface to shield the food from microwaves.

However, in the invention of Utility Model Application No. 63-84319, dielectric breakdown occurred between the microwave reflective lid, that is, the metal lid and the metal part, that is, the portion of the fluororesin coating on the top surface of the metal dish, causing sparks. Fluororesin coating, metal parts,
There was a problem with the lid being damaged.

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

"Means for Solving the Problems" That is, the present invention provides a metal part having a fluororesin coating on the upper surface and a heat generating layer dielectrically heated by microwaves on the lower surface;
A microwave-reflective lid is provided on the surface side of the metal part to shield the food to be cooked from microwaves, and a thickness is provided on the lid side at the part that becomes the contact interface between the lid and the fluororesin coating on the top surface of the metal plate. 3
This is a microwave cooking device characterized by providing a dielectric breakdown prevention layer of IIIl11 or less.

Note that the embodiments of the present invention include at least the following.

■ A microwave cooker in which the thickness of the insulation breakdown prevention layer is 0.5 mm or less.

The invention will be explained in detail below with reference to illustrative drawings, but the invention is not limited to these examples only.

The inventors of the present invention have taken into consideration these conventional problems and, as a result of intensive studies, have created a dielectric breakdown prevention layer with a thickness of 3i or less at the contact interface between the microwave reflective lid and the fluororesin coating on the top surface of the metal dish. It was discovered that damage caused by sparks can be prevented without significantly reducing microwave shielding properties, and the present invention has been completed.

Figures 1(a) and 1(b) show a specific example of the present invention. (1
) is provided with a fluororesin coating (6) to prevent food from sticking during cooking. Metal part (
A heat generating layer (2) is provided on the lower surface of the heat generating layer (1), and is configured in an appropriate amount and composition.

The heating layer (2) is dielectrically heated by microwaves, and the heat is transmitted to the metal part (1) to heat the food on the fluororesin coating (6). At this time, the microwave shielding lid (4) is configured so that almost no microwaves enter the space where the food is to be cooked. Here, the lid (4) and the metal part (
Since (6) between 1) is a fluororesin coating, that is, an insulator, dielectric breakdown easily occurs between (4)-(6)-(1), and to prevent this, a dielectric breakdown prevention layer ( 5) is provided.

In FIG. 1, (3) is the thickness of the coating, such as a silicone foam coating, and (t) is the thickness of the dielectric breakdown prevention layer.

``Function'' The material for the microwave reflective lid is selected from metals such as aluminum, aluminum alloy, iron, stainless steel, and copper, but it is not a material made of plastic, glass, etc. combined with a gold plate or foil. It's okay. Also, microwave 8
Since the purpose is to shield, it is not necessarily a flat plate, but may be a mesh or a perforated plate, as long as the diameter of the mesh or hole is large enough to shield microwaves.

When the lid is formed in this way, anything that attempts to reach the food on the cooking surface from the surface side of the metal part is reflected by the lid.
The microwaves that have passed around to the back side of the metal part are mainly absorbed by the absorber on the back side of the metal part.

At this time, the metal parts of the lid are insulated by the fluororesin coating, so each is in a charged state, so if there is a defect in the fluororesin coating or there is a particularly thin layer, discharge will occur. .

Further, even without such defects, since the fluororesin coating is usually as thin as 15 to 40 microns, a phenomenon in which the fluororesin coating, which is an insulating layer, is destroyed and electrical discharge occurs is likely to occur (dielectric breakdown).

This phenomenon is more likely to occur when the metal has protrusions or scratches or when there is an air layer at the interface between the metal and the insulator.

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

The material can be selected from a wide range of materials, such as silicone rubber, fluorocarbon rubber, fluoroplastics such as PTFE, FEP, polyimide insulating varnish, ceramics, etc., as long as it is an insulator. It is required to be suitable for food use and to have high heat resistance. In addition, it is desirable that the material has good moldability and is rich in strength and toughness.

Structurally, if the thickness of such a dielectric breakdown prevention layer is too thick, microwaves will penetrate through that part, which is undesirable since the microwave shielding effect, which was the initial objective, will be weakened.

FIG. 2 shows the results of an experiment conducted to determine the upper limit of the thickness of the dielectric breakdown prevention layer. As shown in Figure 2 (a), a fluororesin coating (6) (
(approximately 20μ) to create a structure without a heat generating layer,
A heating element (8) was provided on the cooking surface, the thickness of the insulation breakdown prevention layer (5) was varied, 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 thought that the higher the temperature rise, the more microwaves leak.

From this result, the thickness is 3ffiI11 or less, preferably 0
．． A period of 5 minutes or less is suitable. Furthermore, since the lower limit of the thickness depends on dielectric breakdown strength and mechanical strength, it is necessary to design each material individually.

In this way, as a result of providing a microwave shielding lid and a dielectric breakdown prevention layer, the microwaves that are directly absorbed by the food to be cooked are only slightly absorbed, if at all, and the temperature of the food to be cooked increases rapidly. does not occur. In this situation, the microwaves absorbed by the microwave absorber turn into heat,
As a result of the metal utensil being heated by heat conduction from below, the food cooked on the cooking surface is cooked well, similar to cooking in a hot frying pan.

This makes it possible to use this mold stably without causing dielectric breakdown.

"Example" The present invention will be further explained below with reference to Examples.

Example 1: The surface of an aluminum plate with an outer diameter of 200 m and a thickness of 0.8 mm was electrochemically etched to form fine irregularities, and a tetrafluoroethylene resin dispersion was applied to the surface.
Baking was performed for 0 minutes.

Press molding was performed with the tetrafluoroethylene resin coated side facing upward to obtain an aluminum plate with an inner thickness of approximately 1170 m.

After applying a primer to the bottom surface of this aluminum plate and baking it, Fe304 (ferrite DDM-31 manufactured by Dowa Iron Powder Industries Co., Ltd., purity approximately 95%, particle size 200 μm or less) is applied.
silicone rubber containing 7Q% (KE5 manufactured by Shin-Etsu Chemical Co., Ltd.)
52 B[J) as the heat generating layer, diameter $145+++m
, molded to a thickness of 0.5mm, and on top of it and around the edges of the aluminum plate, silicone rubber of a thickness of 1.0mm (KE552 B) was molded.
U) is molded as a coating, a part of the coating is molded into a leg with a height of approximately 15 cm, press vulcanization is performed in a mold, and after demolding, 2
Next vulcanization was performed to obtain a cooking device main body.

Next, an aluminum plate with a thickness of about 0.7mm? ffi
A lid (4) with a diameter of 170 mm and a height of approximately 351,111 ff+ was molded, and a silicone rubber backing (5) with a thickness of 0.5 mm was formed on the edge of the lid as shown in FIG.

Place a raw egg on top of the cooker, cover it with a lid, and heat it in the microwave (Sharp Co., Ltd.).
-130, output 500W) for 4 minutes, 7
The fried egg was baked beautifully, with the same brown marks as those baked in Raiban.

No dielectric breakdown (spark) occurred.

Example 2: A cooker body and an aluminum lid were made in exactly the same manner as in Example 1, and a PTFE adhesive tape (
A thickness of 0.3 van ) was attached.

A fried egg was cooked in a microwave oven, and a well-brown fried egg was obtained. No dielectric breakdown occurred.

Example 3: A cooker was obtained in exactly the same manner as in Example 1, except that a PFA backing with a thickness of 2 mm was used, and a fried egg was cooked.A fried egg with brown marks was similarly obtained. No dielectric breakdown occurred.

``Effects of the Invention'' As described above, the cooking device of the present invention has a structure that combines a metal container with a heating element that is dielectrically heated by microwaves, a metal lid that shields microwaves, and a dielectric breakdown prevention layer. Since the food is baked by the heat from the dish, it is possible to cook food in the microwave that does not require rapid heating by microwaves, and it can be used stably without causing dielectric breakdown. It became.

[Brief explanation of drawings]

FIG. 1 is a sectional view (Figure (a)) of an example of the cooking device of the present invention and an enlarged view (Figure (b)) of the dielectric breakdown prevention layer portion thereof. Figure 2 shows the results of an experiment conducted to determine the upper limit of the thickness of the dielectric breakdown prevention layer. Figure (a) shows the experimental method, and Figure (b) is a graph showing the experimental results. It is. FIG. 3 is for detailed explanation of the present invention,
FIG. 2 is a cross-sectional view of an example in which a dielectric breakdown prevention layer is formed as a backing for a lid. (1)...Rice plate, (2)...Heating layer, (3)...
・Coating, (4)...Microwave shielding lid, (5)・
...Dielectric breakdown prevention layer, (6)...Fluororesin coating, (1
)...Thickness of the insulation breakdown prevention layer.

Claims (1)

[Claims] (1) A metal plate with a fluororesin coating on the top surface and a heating layer dielectrically heated by microwaves on the bottom surface, and a microwave reflector that covers the surface of the metal plate to shield the food from microwaves. What is claimed is: 1. A microwave cooker comprising: a lid; and a dielectric breakdown prevention layer having a thickness of 3 mm or less is provided on the lid side at a contact interface between the lid and the fluororesin coating on the upper surface of the metal dish.