JPH0618047A - Microwave oven - Google Patents

Abstract

PURPOSE:To improve the efficiency of an oven by a method wherein a base sheet formed of a ceramics material is coated with a glaze containing no alkali metal. CONSTITUTION:A food on a turn table 3 installed in an oven chamber 2 of a microwave oven 1 is irradiated with microwaves to effect heating cooking. The turn table 3 is formed such that a base sheet is formed of a substance prepared by burning a pottery stone ceramics material (containing no alkali component) having a low dielectric loss and a frit glaze containing no alkali metal, such as Na, K, and Li, is applied on the base sheet to bring a surface in a dense state. This constitution enables execution of heating in a short time even when a heat loss is low and a food load amount is low, also enables reduction of the occurrence of a fluctuation in oven load efficiency, and improves the heating efficiency of a food.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave oven for cooking food by microwave.

[0002]

2. Description of the Related Art Conventionally, materials such as a turntable, a tray, and a food container used as a food placing table in an oven of a microwave oven are made of glass, plastics, ceramics, or the like, which have heat resistance, thermal shock resistance, and low resistance. The one that satisfies the dielectric heat loss is adopted.

The glass material is called borosilicate glass, and its component is, for example, SiO ₂
80%, Al ₂ O ₃ 2%, B ₂ O ₃ 13%, Na
It is composed of ₂ O at a rate of 4%, and the electrical characteristics are as follows: dielectric constant (ε) is 2.45 GHz, 20 ° C. 4.6, dielectric loss tangent (tan δ) is 2.45 GHz, 20 ° C. 007
4 (for example, manufactured by Nippon Electric Glass Co., Ltd.).

[0004] Further, although those made of plastic are hardly used at present, although they have been used in the past, unsaturated polyester was used as the thermosetting resin and styrene-modified polyphenylene oxide was used as the thermoplastic resin.

Further, as the ceramic material, alumina-based or cordierite-based materials are used.

[0006]

When microwaves are supplied to a closed space in an oven during food heating by a microwave oven, most of the microwaves are used for heating foods, but other microwaves are transmitted. The turntable and the like are heated by being reflected by the magnetron which is the source and being absorbed by the turntable, the tray and the container.

The rate of heating other than food (heat loss) is large when the weight of food is 300 g or less (general food load). It becomes 10% or more, and it becomes more than that for turntables made of plastics and ceramics. This is due to the electrical characteristics of the material of the turntable (product of dielectric constant ε and dielectric loss tangent δ). Therefore, the above-mentioned heat loss increases as the load amount decreases, and such a characteristic is a disadvantage peculiar to the microwave oven which cannot be found in other heating devices.

The present invention has been made in view of the above circumstances and provides a microwave oven using a food placing table and a food container which has a small heat loss, improves the heating efficiency of foods, and has a good design. The purpose is to provide.

[0009]

In order to achieve the above object, the present invention relates to a first aspect of the present invention, wherein a substrate made of a ceramic material is provided with a glaze that does not contain alkali metals, and a food placing table or container is provided. Is used. The above glaze containing no alkali metals is preferably a mixture of quartz powder. A second aspect of the present invention is that a food placing table or container is used in which a substrate made of a ceramic material is provided with a glaze in which a glaze material containing no alkali metals is mixed with lithium. Further, it is preferable that the substrate made of the above ceramic material also does not contain alkali metals.

[0010]

The food on the mounting table and the food in the container according to the first aspect of the invention are efficiently heated by the microwave in a short time.
In particular, even if the food load is small, the heating time is short. Further, by applying a glaze containing no alkali metal mixed with quartz powder to a substrate made of low dielectric heat loss ceramics such as cordierite and mullite, heat loss becomes smaller than that of borosilicate glass.

The food of the second invention is also efficiently heated in a short time, and especially for foods having a small food load, the heating time is short. Further, by using a glaze mixed with lithium, a low dielectric loss is maintained and a gloss effective for design is obtained.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the first invention will be described with reference to the drawings. FIG. 1 shows a front perspective view of a microwave oven equipped with a food placing table (showing a turntable) according to the present invention when a door is opened, and a turntable 3 installed in an oven chamber 2 of the microwave oven 1 is installed. The food is cooked by irradiating it with microwaves from a magnetron (not shown).

The turntable 3 has a substrate made of porcelain-based ceramic material (containing no alkali component) having a low dielectric loss having the composition shown in Table 1 and fired at 1200 ° C. In addition, the frit glaze containing no alkali component shown in Table 2 [alkali metal (Na, K,
A glaze that does not contain Li) or the like] is applied to bring the surface into a dense state.

[Table 1]

[Table 2]

Table 3 shows an example of composition composition of a glaze obtained by mixing quartz powder with the glaze material of Table 2 (mixing quartz powder corresponding to the reduction of lead oxide and magnesia). It is intended to further reduce the dielectric heat loss as compared with.

[Table 3]

Table 4 shows the dielectric constant ε and the dielectric loss tangent t when the ratio of the quartz powder mixed in the glaze shown in Table 2 is changed.
It shows the value of an δ, and shows that the heat loss (ε × tan δ) decreases as the mixing ratio of the quartz powder increases.

[Table 4]

As described above, the turntable 3 uses a ceramic ceramic material (alkali-free ceramic material), which has heat resistance and mechanical strength necessary for a microwave oven and has a low dielectric heat loss, as a substrate. The non-alkali frit glaze or the alkali-free frit glaze mixed with quartz powder is applied to reduce the heat loss value.

Table 5 shows the saturation temperature when a turntable having a diameter of 270 mm installed in a microwave oven having a power output of 1200 W (rated) is heated for 30 minutes without load (heating is stopped for 40 seconds after heating for 5 minutes). It shows that the turntable according to the present invention has a lower saturation temperature than the conventional one and that the heat loss is small.

[Table 5]

FIG. 2 shows the reduction of the change in oven efficiency due to the change in the load amount in the turntable 3 according to the present invention. The horizontal axis is the water load amount measured by the microwave output, and the vertical axis is the 2000 cc water load. The output fluctuation rate when the output at time is 100% is shown. A curve A shows the microwave output state in the oven in the case of the conventional glass turntable, and a curve B shows the microwave output in the oven of the same size in the case of the turntable 3 according to the present invention (mixed with quartz powder in Table 3). It shows the state, about 180
It can be seen that the microwave output is improved by about 7% when the water load is cc, and the mixing of the quartz powder reduces the dielectric constant ε and the dielectric loss tangent tan δ, thus improving the oven efficiency.

Next, an embodiment of the food placing table, container, etc. according to the second invention will be explained (the turntable shown in FIG. 1 will be explained). The present invention provides the food placing table, container, etc. (shown for the turntable) of the first invention,
The heating efficiency is improved even when the heat loss is small and the load is small, but because we use an alkali-free glaze, we noticed that the gloss is very small and the design is inferior, and we improved it. is there.

That is, the turntable 3 according to the present invention is
A porcelain-based ceramic material (containing no alkaline component) having a low dielectric loss and having the composition shown in Table 1 above was fired at 1200 ° C. to obtain a substrate. Then, this substrate was glazed with the Li-free alkali-free frit glaze shown in Table 6 (corresponding to the reduced amount of borax in Table 2 mixed with oxidized lithium).

[Table 6]

Table 7 shows the values of the dielectric constant ε and the dielectric loss tangent tan δ of the turntable 3 of the present invention and the conventional turntable to which the glaze shown in Table 6 is applied, and the heat loss is the same as that of the first invention. It shows that it is decreasing like the turntable.

[Table 7]

Table 8 shows the saturation temperature when a turntable having a diameter of 270 mm installed in a microwave oven of 1200 W output (rated) is heated for 30 minutes without load (heating is repeated for 40 seconds after heating for 5 minutes). It shows that the turntable according to the present invention has a lower saturation temperature and a smaller heat loss than the conventional one.

[Table 8]

Also in the turntable 3 of the present invention, as in the case of the first invention shown in FIG.
At the water load of c, the microwave output is improved by about 7%, and the oven efficiency is improved.

Thus, the turntable 3 of the second invention is
Is effective in terms of design with good gloss while retaining reduction of heat loss.

[0025]

【The invention's effect】

(A) In the first aspect of the invention, the food placing table or the food container used in the microwave oven is glazed with a non-alkali glaze or a non-alkali glaze mixed with quartz powder on a substrate made of a ceramic material. Even if the food load is small and the food load is small, heating can be performed in a short time, and fluctuations in oven load efficiency can be reduced. (B) In the second invention, the food placing table or the food container used in the microwave oven is glazed with an alkali-free glaze in which a substrate made of a ceramic material is mixed with lithium. Therefore, the oven is similar to the first invention. It is possible to reduce fluctuations in load efficiency, and it is also excellent in design with good gloss.

[Brief description of drawings]

FIG. 1 is a front perspective view of a microwave oven to which a food placement table (turntable) of the present invention is applied in an open state.

FIG. 2 is a characteristic diagram showing a microwave output ratio of the turntable of the present invention and the turntable of the conventional example.

[Explanation of symbols]

 1 Microwave 2 Oven 3 Turntable (food table)

Claims (4)

[Claims] 1. A microwave oven using a food placing table, a container or the like, characterized in that a glaze containing no alkali metals is applied to a substrate made of a ceramic material. 2. The microwave oven according to claim 1, wherein the glaze containing no alkali metal contains quartz powder. 3. A microwave oven using a food placing table, a container, or the like, characterized in that a substrate made of a ceramic material is coated with a glaze obtained by mixing a glaze material containing no alkali metal with lithium. 4. The microwave oven according to claim 1, wherein the substrate made of the ceramic material is made of a material containing no alkali metals.