JP2006262921A - Highly efficient container for microwave oven - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase the heat generation of a matter to be heated in a container without heating the container by increasing the dielectric constant of the container 1 to be used for heating in a microwave oven, thereby improving the impeadance matching with an incident microwave 6. <P>SOLUTION: The dielectric constant of the container 1 can be increased by dispersing and mixing metallic powder 2, which is not an electromagnetic wave absorber, in the material of the container 1 by a proper ratio and molding the mixture, thereby improving the matching of the incident microwaves 6 with the matter to be heated. Consequently, the reflection of the microwaves 6 on the container 1 is reduced, and microwave intensity in the matter in the container is increased to increase the heat generation of the matter.. Thus, the mert of the microwave oven, which heats the matter directly without heating the container, is made multipliable. Thius, the heating efficiency of the matter is improved, and also a heating period is shortened, energy is saved and the service life of a microwave generator is extended. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a technique for improving the heating efficiency of tableware or containers used for heating or cooking beverages, foods, and the like using microwave power, such as a microwave oven.

The feature of microwave microwave heating is that the object to be heated, such as food, is directly heated rather than the container. However, since the microwave is an electromagnetic wave, if the impedance matching, which is a non-reflective condition from the object to be heated, is poor, the ratio of the power reflected by the container or the like becomes larger than the power entering the inside of the object to be heated. As a result, multiple reflections are made extremely many times. For this reason, the microwave oven itself is unnecessarily heated, and the heating time of the object to be heated is longer than necessary.

Specifically, in the case of glass, plastics and ceramics that have been widely used conventionally, the relative dielectric constant of the container itself is about 3.0 to 6.0. On the other hand, the object to be heated in the container usually contains a lot of moisture, and its relative dielectric constant is between about 10.0 and 80.0 depending on the water content. It was difficult.

For example, if the relative dielectric constant is 72.0 when the main component is water, the relative dielectric constant is ideally close to 8.8 and the thickness is ideal for perfect microwave microwave matching (non-reflection). A container of about 10.2 mm is required. Microwave absorption is small and a material having such a high relative dielectric constant is inexpensive and difficult to obtain, and microwave matching has been improved by increasing the thickness of the container exclusively. However, this thickness also has a limit from a practical viewpoint, and a great improvement effect cannot be obtained. In addition, if the reflection due to mismatching is large, there is a drawback that the life of the microwave generator is shortened.

In addition, in order to improve the heatability of the object to be heated, attempts have been made to heat the container itself by mixing an electromagnetic wave absorber such as a carbon component or ferrite that absorbs electromagnetic waves into the container itself (the following). Patent Documents 1 and 2). However, since this heats the container itself, it is inferior in thermal efficiency to the object to be heated compared to the characteristics of the microwave oven that generates heat, and it is extremely difficult to control the temperature of the container that is not metal and generates heat. . Also, they do not take into account microwave matching.
JP 7-1116058 A JP 2004-35105 A

The object of the present invention is to provide means for improving the relative dielectric constant of a container without changing the material of the conventional container so much and without heating the container with microwaves, thereby This is to achieve impedance matching between the microwave and the object to be heated.

As shown in the sectional view of the container 1 of the embodiment shown in FIG. 1, the means of the present invention for solving this problem is formed by dispersing and mixing metal powder 2 that is not an electromagnetic wave absorber in the material of the container 1. It is to be. The relative permittivity obtained when the metal powder 2 is mixed in three volume ratios with respect to the relative permittivity of the container material before the metal powder 2 is mixed is shown in FIG. FIG. 2 shows that a relative dielectric constant of 9.0 or more can be obtained, for example, by mixing about 26% of the metal powder 2 by volume with a container material having a relative dielectric constant of 4.0.

In this way, since the relative dielectric constant of the container can be controlled by the ratio of mixing the metal powder 2 into the material of the container 1, impedance matching between the microwave and the object to be heated is possible, and the microwave power is applied. It can be absorbed to the maximum extent by the heated object. Further, since this method uses metal powder 2 that is not an electromagnetic wave absorber, it does not absorb microwaves and does not cause the container 1 itself to generate heat.

Fig. 3 shows the condition of the object to be heated (assuming that the relative permittivity is 72 and the loss factor is 0.06) when the thickness of the circular and rectangular cups with the same cross-sectional area is 10 mm and the relative permittivity is changed. The result of simulating the relative calorific value was shown. From FIG. 3, it can be seen that when the relative dielectric constant of the container is set to a value of about 8.0 to 12.0, the heating value of the object to be heated is doubled compared to the case of the conventional container having a relative dielectric constant of around 4.0. .

In FIG. 3 described above, the object to be heated in the cup has a high relative dielectric constant like water. Various ingredients are used in an actual microwave oven or the like. Therefore, when the relative permittivity is 10.0 and the thickness is 10 mm, the calorific value of the object to be heated when the relative permittivity of the object to be heated in this container 1 is changed is calculated in either case. It was also confirmed that it increased from the conventional container (relative dielectric constant 3.6).

FIG. 4 shows the distribution of the microwave intensity on the line passing through the center of the rectangular cup, with the reference value of the intensity of the microwave 6 incident from the side in FIG. 1 being 1.0. From FIG. 4, it can be seen that the incident microwave 6 is partially reflected by the cup, so that a standing wave of intensity (maximum and minimum ratio of undulating intensity) stands in front of it. It can be seen that the standing wave is small because the reflection is small in the cup of the present invention. Moreover, it turns out that the to-be-heated object in a cup has a microwave intensity more than twice the conventional one. This indicates that the heating value of the object to be heated in the cup of the present invention is more than doubled.

The microwave 6 incident from above the container 1 is covered with a lid 4 having a thickness of 2.0 to 4.0 mm in consideration of the air layer 5. The metal powder 2 is also mixed into the material of the lid 4 by about 10% to 20% by weight to increase the relative dielectric constant. This idea can be applied regardless of the shape of the container 1. Further, with respect to the variation in the thickness of the air layer 5, the air layer 5 can be substantially eliminated by making the lid 4 a drop lid that enters the container 1. The mixing ratio of the metal powder in the case of this drop lid is the same as that when the microwave is incident from the side.

The method for improving the dielectric constant of the container according to the present invention can use conventional inexpensive glass, plastic or ceramic container materials and inexpensive metal powder, and does not involve a chemical reaction. In addition to improving the heating efficiency of the object to be heated, the heating time can be shortened, the energy can be saved, and the life of the microwave generator can be extended. The economic effect is very high.

The best embodiment of the present invention is slightly different depending on the shape and size of the container. However, in the case of the microwave 6 incident from the side as shown in FIG. 1, the thickness is 8 mm to 12 mm and the relative dielectric constant is The thing around 10.0 can obtain good impedance matching for many types of objects to be heated, and the microwave power consumption (that is, the amount of generated heat) by the objects to be heated can be made the maximum.

In order to realize the best container 1 described above, when the material is glass or ceramics, aluminum powder is mixed and molded at a weight ratio of 10.0% to 26.0% depending on the type of glass / ceramics. In the case of copper powder, the ratio by weight is about three times that of aluminum powder.

If the material is porcelain or has a relatively large relative dielectric constant, aluminum powder is mixed at a weight ratio of 5.0% to 20.0% depending on the type of the material. In the case of copper powder, the ratio by weight is about three times that of aluminum powder.

In FIG. 1, when the microwave 6 is incident from above the container 1, the aluminum metal powder 2 at a rate of 10% to 20% depending on the thickness of the air layer 5 on the water 3 to be heated. By using the lid 4 in which the water is dispersed, the heat generation amount of the water 3 can be similarly increased. Further, when the air layer 5 is substantially eliminated by using a drop lid, the same as when the microwave 6 is incident from the side.

FIG. 1 is a cross-sectional view of a container 1 according to an embodiment of the present invention, in which about 26.0% by weight of aluminum metal powder 2 is mixed in glass or earthenware to obtain a relative dielectric constant of about 10.0, and the thickness of the container 1 When the thickness is set to 8.6 mm, the power consumption of the microwave 6 incident from the lateral direction can be doubled as compared with the conventional container even for various objects to be heated. The lid 4 has an air layer 5 of 10.0 mm and aluminum metal powder 2 mixed by about 14.0% by weight to a thickness of 3.2 mm.

The idea of impedance matching for the container 1 of the present invention is not limited to a microwave oven, but also applies to a general microwave heating container. Further, since the material of the present invention is inexpensive, it has a high economic effect.

Sectional drawing of the cup container 1 at the time of putting the water 3 of the Example of this invention. A graph of relative permittivity obtained when metal powder 2 is dispersed in the material of container 1. The graph of the calorific value of the water 3 in the cup when the relative permittivity of the cup container 1 is changed. The comparison figure of the conventional cup and the cup of this invention of the microwave intensity distribution in the inside and outside of the cup container 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Container 2 Metal powder 3 Water to be heated 4 Container lid 5 Air layer 6 Incident microwave

Claims (4)

In a container or the like used for heating by microwaves, a container or a lid thereof, wherein metal or metal oxide metal powder that is not an electromagnetic wave absorber is dispersed and molded in a material such as a container. 2. The container according to claim 1, wherein the material of the container or the like is paper, glass, plastic, or ceramic. In Claim 1, the metal of the metal powder is aluminum, gold, silver, copper, brass, zinc, tin or an alloy containing them, or an oxide thereof, and the mixing weight ratio of the powder is 2% or more. And the container or its lid | cover of Claim 1 or Claim 2 which is 80% or less. 4. The container according to claim 1, wherein the container has a thickness of 1 mm or more and 16 mm or less.

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