JP2004294056A - Microwave heater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To favorably heat a material to be heated such as food with microwaves while the food is wrapped with superheated steam. <P>SOLUTION: This microwave heater includes: a heating chamber 13 storing the material to be heated; a steam generating means 15 for supplying the superheated steam to the heating chamber; a superheated steam keeping means 22 for preventing lowering of temperature of the superheated steam in the heating chamber; and a microwave generating means 14 for applying microwaves to the material to be heated. By this configuration, the material to be heated is directly placed on the superheated steam keeping means 22, whereby endothermic energy is effectively transmitted to the material to be heated through a heating plate, thereby overcoming the disadvantage of uneven heating due to the existence of standing wave specific to the microwave. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a heating device using microwaves for heating various foods and other objects to be heated quickly and while maintaining good quality.

  Conventionally, as this type of heating device, for example, a food thawing type cooking furnace described in Japanese Patent Publication No. 55-51541 has been known. FIG. 5 shows the configuration, in which a stirrer 3 is provided on a ceiling 2 in a freely sealable furnace 1, and a magnetron irradiation unit 4 is disposed near the stirrer. The furnace 1 has a detachable food placing shelf 5 under which a liquid tray 6 for water, oil or the like is arranged, and a heater 7 for gas, electric heating or the like is provided below the tray. By the combination of the magnetron irradiating unit 4 and the liquid-introducing dish 6 with the heater 7, heating by magnetron irradiation from above and steam heating by boiling water from below can be used together.

  With this configuration, when heating food, a combination of internal heating by magnetron irradiation and steam heating by steam can be selected according to the menu type. In addition, it is described that since steam is generated, it can be used as a bread and cake processor in all steps of thawing frozen cakes and frozen cakes and baking fermentation.

  However, in such a conventional heating apparatus, when water is poured into the liquid-introducing dish, the water vapor does not exceed the boiling point (100 ° C. at normal pressure), and the water is supplied to the heating chamber only at such saturation. It is steam below temperature. Such steam will wet the food surface. In particular, when the food is frozen, significant dew condensation occurs on the surface of the food before it is thawed. For this reason, thawing a frozen bread or the like can prevent the food from drying, but the skin that is originally desired to be crispy becomes sticky and the touch feeling is greatly impaired.

  The present invention is intended to solve such a conventional problem, and a system capable of wrapping an object to be heated such as food with superheated steam and generating superheated steam in order to satisfactorily heat various objects to be heated by microwaves. It is intended to realize.

  Further, the present invention realizes a configuration in which the generated superheated steam can be kept as superheated steam so that the temperature does not become lower than the saturation temperature in the heating chamber.

  Further, the present invention realizes a configuration in which an object to be heated can be heated by effectively using superheated steam.

  In order to achieve the object of the present invention, a heating chamber for accommodating an object to be heated, steam generating means capable of supplying steam to the heating chamber, and superheated steam in the heating chamber for preventing a decrease in the temperature of the superheated steam Maintaining means, and microwave generating means for irradiating microwaves to the object to be heated, wherein the superheated steam maintaining means is formed of a radio wave absorber which absorbs microwaves and generates heat, and is heated by side wall rails in the heating chamber. It has a configuration to be arranged at an optimum position according to the type and shape of the object, and by directly placing the object to be heated on the superheated steam maintaining means, the absorbed energy is applied to the object to be heated as a hot plate. The structure is such that the space for filling the superheated steam can be made variable by effectively conducting the heat and heating can be performed efficiently.

  The microwave heating device of the present invention can easily generate superheated steam by the superheated steam maintaining means. Further, by directly placing the object to be heated on the superheated steam maintaining means, the absorbed energy is effectively transmitted to the object to be heated as a hot plate, and the heating based on the existence of the standing wave peculiar to the microwave. Unevenness can be improved.

  Further, by installing and removing the superheated steam maintaining means at an appropriate position in the heating chamber in accordance with the type, shape, and quantity of the object to be heated, the space filled with the superheated steam can be changed, and heating can be performed efficiently and in a short time.

  The present invention can easily generate superheated steam with the above-described configuration.

  Further, the superheated steam supplied to the heating chamber is kept as the superheated steam so as not to be lower than the saturation temperature. In addition, it absorbs microwaves and raises the temperature, exerts a hot plate effect, and prevents a decrease in the temperature of superheated steam. Similarly, a partition wall coated or molded with a radio wave absorber such as ferrite, or an electric heat source provided in a heating chamber also exerts a hot plate effect and prevents a decrease in the temperature of superheated steam.

  Further, the superheated steam can be effectively used in accordance with the object to be heated. At least the superheated steam maintaining means provided on the upper surface of the heating chamber prevents dew condensation on the ceiling surface of the superheated steam guided to the heating chamber and the drop of the superheated steam onto the object to be heated, thereby preventing the quality of the object to be heated from deteriorating. . Alternatively, at least the superheated steam maintaining means provided on the lower surface of the heating chamber, by placing the object to be heated directly on the superheated steam maintaining means, effectively transmits the absorbed energy to the object to be heated as a hot plate, Heating unevenness based on the existence of a standing wave unique to microwaves can be improved. Further, by attaching and detaching the superheated steam maintaining means at an appropriate position in the heating chamber in accordance with the object to be heated, the space filled with the superheated steam can be varied, and the heating can be efficiently performed in a short time. Further, at least the superheated steam maintaining means having a through hole provided on the lower surface of the heating chamber can be heated again when the guided superheated steam passes through the through hole, re-evaporated, and returned to the superheated steam. .

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 2 is an external view of the microwave heating apparatus according to the present invention. A door 9 is supported on the front surface of the main body 8 so as to be openable and closable, and closes an opening of a heating chamber in which food is stored. The operation panel 10 is provided with a heating command key 11, and codes entered in one or several digits affect the heating method, such as the type and quantity of food, storage temperature (freezing or chilled storage), and heating completion temperature. It is associated with a given factor, and this is instructed to a control unit described later. A water supply tank 12 is detachably provided on the right side of the main body.

  FIG. 1 is a front sectional view of a heating chamber showing an embodiment of the present invention. A heating chamber 13 has a magnetron 14 which is a microwave generating means for irradiating microwaves, and a steam generator 15 which is a steam generating means. Are combined.

  The steam generator 15 includes a boiler 16 made of a non-magnetic material such as heat-resistant glass or ceramic, a ferromagnetic porous heater 17 built in the boiler 16, and an inverter coil 18 for supplying power to the non-contact boiler from outside the boiler. Water is dropped from the water supply tank 12 to the boiler 16 via a water supply pump 19. The inverter coil 18 is supplied with a high-frequency voltage by an inverter power supply 20 and directly heats the ferromagnetic porous heater 17 by induction heating, so that there is no loss due to heat conduction and the temperature quickly rises to 100 ° C. or higher. The temperature and the amount of water supply are freely controlled by the control unit 21, and superheated steam can be easily generated.

  By the way, even if the superheated steam is supplied to the heating chamber, if the heating chamber is cold, the temperature of the steam drops sharply and falls below the saturation temperature. It is very difficult to remain superheated steam in the heating room. Therefore, in the present invention, a heating partition 22 serving as superheated steam maintaining means is provided on the upper and lower surfaces of the heating chamber 13. This is configured to be detachably mounted on the side wall rail 23, and to raise or re-evaporate the superheated steam supplied into the heating chamber to prevent the superheated steam from dropping below the saturation temperature. There are several embodiments of the specific configuration of the superheated steam maintaining means.

  First, a description will be given of an embodiment in which the superheated steam maintaining means is formed of a partition made of a porous material such as a ceramic capable of absorbing moisture. When a plate with unglazed thickness is used as the temperature raising partition, a part of the superheated steam led to the heating chamber is absorbed by this. Then, it is heated again by the microwave and re-evaporated. At this time, the steam inside the ceramic expands rapidly, the internal pressure increases, and the boiling point can reach 100 ° C. or higher. That is, even if dew condensation occurs on the surface of the temperature-raising partition, it can be returned to superheated steam again. If glaze is applied to the side of the heating partition that does not face the object to be heated, that is, the ceiling side and the floor side, the reheated superheated steam blows out only to the object to be heated, and the steam is used without loss. Can be. It is also advantageous in increasing the internal pressure.

  Next, a description will be given of an embodiment in which the superheated steam maintaining means is formed of a partition containing fibrous material such as paper or cloth capable of absorbing moisture. This also absorbs a part of the superheated steam guided to the heating chamber and heats again by microwaves to re-evaporate, similarly to the above configuration. Although the internal pressure does not increase as in the case of ceramics, since the steam can be efficiently absorbed, it is possible to reliably prevent the dew condensation water from falling from the ceiling onto the object to be heated.

  Further, the superheated vapor maintaining means may be formed by a partition wall made of a water-repellent dielectric, for example, crystallized glass or ceramic having both surfaces glazed. Although it cannot absorb and re-evaporate the steam, it is heated by the microwaves and becomes a hot plate to raise the temperature of the superheated steam guided to the heating chamber.

  Further, the superheated steam maintaining means may be formed by a partition wall coated or molded with a radio wave absorber such as ferrite which absorbs microwaves and generates heat. Although it is not possible to absorb and re-evaporate the steam, it is efficiently heated by the microwaves, and the temperature of the superheated steam guided to the heating chamber as a hot plate is raised. Further, since the microwaves are considerably absorbed, the microwaves reaching the object to be heated are reduced, and there is an effect of reducing uneven heating.

  Finally, an example in which the superheated steam maintaining means is formed by an electric heat source provided in a heating chamber will be described. In this method, the present invention is applied to a heating device known as a microwave oven, and the temperature of superheated steam is increased by an electric heat source provided in a heating chamber.

  The control unit 21 decodes the heating command code input from the heating command key 11 and reads the designated heating condition from the memory 24. As the heating conditions, control data of the steam generator 15, that is, input control data to the inverter coil 18, data indicating water supply control to the water supply pump 19, and data indicating power supply conditions to the magnetron 14 are stored. . These data may be control values in the form of time-series data of each block, or may be a certain mathematical expression. In the case of a mathematical expression, the control unit 21 calculates this to obtain time-series data, and based on the time-series data, controls the input to the inverter coil 18, controls the amount of water supplied to the water supply pump 19, and supplies power to the magnetron 14. To control the temperature and amount of the superheated steam introduced into the heating chamber 13 according to the progress of the heating, and the temperature of the food so as to be a predetermined value.

  The object to be heated 25 is placed on a placing plate 26 having a through hole. The mounting plate 26 has legs so as not to contact the heating partition 22 on the lower surface. The heating wall 22 on the upper surface can be freely disposed at three positions in the illustrated example by a plurality of side wall rails 23. With such a configuration, by arranging the temperature-raising partition 22 on the upper surface at an optimum position according to the type and shape of the object to be heated, the space filled with the superheated steam can be limited to a small size, and the object to be heated 25 can be more efficiently. Can be heated.

  FIG. 3 is a diagram showing the temperature of superheated steam in the heating chamber during heating and the supply state of microwaves in the present invention. In FIG. 7A, the irradiation of the microwave is stopped during the rising period R until the heating chamber reaches 120 ° C. This is effective for heating foods that are likely to have uneven heating due to a mixture of different materials such as reheating of steamed food such as sweet potatoes or a frozen lunch box.

  To briefly describe the superheated steam, the superheated steam refers to steam at a temperature equal to or higher than the saturation temperature under a certain pressure. For example, the steam refers to steam at 100 ° C. or higher at normal pressure (1 atm). When heating an object to be heated containing moisture such as food with such superheated steam, it has the ability to evaporate water from the object to be heated until the temperature of the superheated steam drops to 100 ° C. or less, and even when a dry object is heated. Never wet your opponent. And since it has high heat energy, heat exchange is effectively performed on the surface of the object to be heated. Superheated steam has just begun to be used in industry as a drying means in fields such as food processing.

  On the other hand, in microwave heating, it is well known that microwaves penetrate deeply into an object to be heated and simultaneously heat the inside and outside of the object to be heated. However, since the heating chamber is a kind of cavity resonator for microwaves, a standing wave is generated, and when the planar heating pattern is viewed, places where the electric field intensity is strong and places where the electric field strength is weak appear alternately. This is the cause of the so-called uneven heating characteristic of the microwave oven.

  Here, the present invention pays attention to the large thermal energy of the superheated steam, and also pays attention to the property that the object to be heated is not wetted. That is, according to the heating pattern of FIG. 3A, the superheated steam quickly wraps around the freezing platter, for example, and begins to thaw the surface evenly. On the other hand, microwaves, by their nature, are easy to enter from the four corners of a lunch box and conversely it is difficult to raise the temperature in the center. , The microwave concentrates at that location. However, in the present invention, with the help of the superheated steam, the thawing center of the frozen lunch box remains undisturbed as in the four corners. Once they begin to melt, the concentration of microwaves at the four corners is reduced.

  This effect can be obtained even with ordinary saturated steam. However, if the steam is saturated, condensation forms quickly on the surface of the frozen lunch box, and wets the surface more and more as heating progresses. A slightly moistened hamburger or hamburger can improve performance, but it can be a problem for grilled fish. And above all, rice is deadly if the dew drops. The superheated steam instantly boiles the water contained in the food, so that the surface is not wetted, and in this regard, the workmanship of cooking has been dramatically improved.

  FIG. 2B shows an example in which the temperature of the steam is changed while the heating chamber is being heated. The first half is switched to a moderately humid state of about 60 ° C., and the second half is switched to a superheated steam of 120 ° C. at a stretch. The configuration is such that microwaves are also sequentially reduced. This is effective for heating foods that require a crispy surface, such as frozen pans and fries. That is, while preventing food from drying with thin steam below the saturation temperature in the first half, heating unevenness due to microwaves is slightly alleviated, and the surface is dried at once with superheated steam in the second half.

  The temperature of the steam in the first half is optimally selected according to the food. Good results were obtained in the experiment at a temperature of about 60 ° C. for the frozen pan and a little higher at about 80 ° C. for the fry. In addition, in reheating steamed foods such as suimai and meatballs, a good result was obtained by allowing the food to absorb a large amount of water with saturated steam at 100 ° C.

  FIG. 4 is a front sectional view of a heating chamber showing another embodiment. In this embodiment, two magnetrons 14 are provided on the ceiling and the bottom of the heating chamber. This vertical power supply is a practical technique widely used in commercial microwave ovens, and a high output can be obtained while maintaining a good electric field distribution. The object to be heated 25 is placed directly on the heating partition 22 on the bottom surface, not on the placing plate. A through hole 27 is formed in the temperature raising partition on the bottom surface, and superheated steam is discharged from the steam generator 15 to the bottom surface of the heating chamber 13.

  In such a configuration, the temperature rise partition wall 22 on the bottom surface absorbs microwaves and rises in temperature, and the heat is directly transmitted to the object to be heated, so that heating efficiency is good. Further, since the superheated steam is discharged to the bottom surface of the heating chamber, there is no fear of touching the erroneously discharged high-temperature superheated steam when the door is opened after the heating is completed and the object to be heated is taken out. The superheated steam introduced into the heating chamber is effectively heated when passing through the through-hole 27 of the temperature-raising partition wall 22 to prevent the temperature from lowering. In addition, the superheated steam maintaining means having at least the through hole provided on the lower surface of the heating chamber can be heated again when the guided overheated steam passes through the through hole, re-evaporated, and returned to the superheated steam. .

  The temperature raising partition, which is the superheated steam maintaining means, is provided above and below the heating chamber in any of the embodiments of FIGS. 1 and 3, but may be provided only on the upper surface of the heating chamber, or on the contrary, It may be provided only on the lower surface of the chamber. In short, as long as sufficient heat can be applied to the superheated steam introduced into the heating chamber, only one of them may be used, and the installation location may be the side wall or the rear wall. It is also conceivable to employ a configuration in which the five surfaces excluding the door are heat-raising partitions. Alternatively, it is possible to make the doors vulnerable to the temperature-raising partitions by eliminating the windows.

  In the present embodiment, a configuration in which heating is performed according to a heating method input from the input unit and in accordance with a predetermined heating condition in the storage unit without a detection unit such as a sensor is described. Detecting means for measuring the environment and feeding back the power supply to the steam generator may be provided. Such a detecting means includes a temperature detecting means and a humidity detecting means.

  The steam generator is not limited to those described in the present embodiment, and any steam generator that can generate superheated steam can be used. For example, a configuration in which an ultrasonic vibrator is provided in a boiler, fine water droplets are generated, and heated by a heat source to generate superheated steam is also conceivable.

Front sectional view of a heating chamber showing one embodiment of the present invention. External view of the heating device (A) Diagram showing one embodiment of the heating sequence (b) Diagram showing another embodiment of the heating sequence Front sectional view of a heating chamber showing another embodiment of the present invention. Front sectional view of the heating chamber of a conventional food thawing type cooking furnace

Explanation of reference numerals

13 heating room 14 magnetron (microwave generating means)
15 steam generator (steam generating means)
22 Heating bulkhead (superheated steam maintaining means)

Claims (2)

A heating chamber for accommodating the object to be heated, steam generating means capable of supplying steam to the heating chamber, superheated steam maintaining means in the heating chamber for preventing the temperature of the superheated steam from decreasing, and microwave heating the object to be heated. Microwave generating means for irradiating microwaves, the superheated steam maintaining means is formed of a radio wave absorber which absorbs microwaves and generates heat, and is optimally adapted to the type and shape of an object to be heated by a side wall rail in a heating chamber. A space to fill the superheated steam while effectively transferring the absorbed energy as a hot plate to the heated object by directly placing the heated object on the superheated steam maintaining means. The microwave heating device is configured to be able to change the temperature and heat efficiently. A heating chamber for accommodating the object to be heated, steam generating means capable of supplying steam to the heating chamber, superheated steam maintaining means in the heating chamber for preventing the temperature of the superheated steam from decreasing, and microwave heating the object to be heated. Microwave generating means for irradiating microwaves, the superheated steam maintaining means is formed of a radio wave absorber which absorbs microwaves and generates heat, and is optimally adapted to the type and shape of an object to be heated by a side wall rail in a heating chamber. Having a through hole in the superheated steam maintaining means, supplying superheated steam from the steam generating means below the superheated steam maintaining means so as to pass through the through hole, and A microwave heating apparatus configured to place an object to be heated above the superheated steam maintaining means.

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