EP2728966B1

EP2728966B1 - High-frequency heating cooker

Info

Publication number: EP2728966B1
Application number: EP13190765.1A
Authority: EP
Inventors: Satomi Uchiyama
Original assignee: Panasonic Holdings Corp
Current assignee: Panasonic Holdings Corp
Priority date: 2012-10-30
Filing date: 2013-10-30
Publication date: 2024-06-26
Anticipated expiration: 2033-10-30
Also published as: EP2728966A1; JP6089224B2; CN103791529A; JP2014088984A

Description

TECHNICAL FIELD

The present invention relates to a high-frequency heating cooker for dielectric heating an object to be heated.

BACKGROUND ART

A typical microwave heating device as a high-frequency heating cooker of this kind is a microwave oven for directly heating an object to be heated, i.e., a food. Accordingly, the microwave oven is an easy-to-use device necessary for living that does not require any pot or pan. In recent years, new products are put into practical use, in which a heating chamber shape has been improved in the level of convenience such that a space for accommodating a food or foods has a flat bottom surface and a width dimension of 400 mm or more, which is greater than a depth dimension, to widely lay and heat the foods.
Also, with the multifunctionality of the microwave ovens, those having a "grilling" function or a "steaming (cooking with steam)" function appear in the market, in addition to the conventional "heating" and "microwave-cooking" functions to high-frequency heat the foods by radiating microwaves to the foods.
In the "heating" and "microwave-cooking" functions, a high-frequency heating treatment is conducted with the foods placed on a bottom wall of the heating chamber. That is, microwaves generated by a high-frequency generating device or a magnetron are radiated from an exciting portion through a waveguide so that the foods may be heated by dielectric heating.
In the case of the "grilling" in which the foods are cooked in a manner analogous to direct heating, the foods (for example, fishes, hamburgers, gratins or the like) are laid on a cooking dish that is supported by supports provided on right and left side walls of the heating chamber so that upper portions of the foods may be heated by a heater located above the foods and bottom portions of the foods may be heated by the cooking dish that has been increased in temperature by microwaves radiated from below the cooking dish.
Also, the "steaming" is a method of heating the foods using a latent heat of water vapor (539 calories per gram) generated by boiling water. In this method, a steamed food (for example, a steamed egg hotchpotch, a steamed bread or the like) is cooked using a steam cooker called a steamer or steaming basket. The steaming is characterized in that a cooked food is kept from drying out because it is heated with moisture added thereto for uniform cooking.
In conventional microwave ovens not having any steam generator that generates water vapor, a method of heating a food in a manner analogous to the steaming with the use of only high-frequency heating is widely employed. This method is known as "microwave steaming" and applied to, for example, chickens or clams steamed with Japanese liquor or sake. In the conventional "microwave steaming", moisture (sake in this case) added to the food is heated to generate water vapor during cooking. Nowadays, silicon-based containers of various shapes are frequently used as containers for microwave steaming.
The high-frequency heating has the advantage of requiring a shorter cooking time but is disadvantageous in that uneven heating is likely to occur and overheating often dries out or hardens the food. In Chinese dumplings such as jiao-zis or shao-mais or steamed Chinese breads, ingredients are wrapped with a starchy skin essentially made of wheat flour and, hence, the conventional high-frequency heating with the use of microwaves encounters a difficulty in finishing them in a moist, smooth, fluffy and soft state as if they have been steamed with the steamer.
For the reasons set forth above, a microwave oven suited for the steaming has been proposed, in which a food or foods are not directly heated by microwaves, but water prepared within a heating chamber in advance is heated by microwaves and the food is subsequently heated and cooked with the use of water vapor generated (see, for example, Patent Document 1). Such a conventional microwave oven is provided with a steaming utensil having a water tray, a food plate disposed above the water tray, and a lid that covers a space around the food placed on the food plate. A heating element for generating heat upon absorption of microwaves is disposed on the reverse side of the water tray. The food plate is made of a material that does not allow transmission of the microwaves and has holes of a size that allows transmission of steam. The lid is made of a material that does not allow transmission of the microwaves.
Another microwave oven has been proposed, in which a steaming and baking utensil is used during cooking to heat a food or foods accommodated in a heating chamber using water vapor and microwaves and to brown a bottom surface of the food via a cooking dish (see, for example, Patent Document 2). This conventional microwave oven is provided with a water vapor generator disposed outside the heating chamber and a heating element held in close contact with the cooking dish to generate heat by absorption of the microwaves. After the food placed on the cooking dish has been placed within the heating chamber, the bottom surface of the food held in contact with the cooking dish is browned by heating the heating element of the cooking dish with the microwaves to increase the surface temperature of the cooking dish while water vapor generated by the water vapor generator is being introduced into the heating chamber to heat the food.
The steaming and baking utensil as disclosed in Patent Document 2 is of a construction in which a steam vent is formed in a wall of the heating chamber to allow water vapor generated by the water vapor generator to be ejected therethrough and a steam inlet is formed in a lid to introduce water vapor, which has been ejected from the steam vent, into the steaming and baking utensil so that the water vapor supplied from the water vapor generator may be introduced into the steaming and baking utensil via the steam inlet.
However, in the conventional steaming utensil as disclosed in Patent Document 1, water in the water tray is heated by microwaves, but because the food is covered with the lid and the food plate each made of a material that does not allow transmission of the microwaves, the food cannot be directly heated by the microwaves. Also, because water stored in the water tray is heated and boiled by the microwaves, it takes time before water vapor is generated.
Further, the steaming utensil as disclosed in Patent Document 1 is dedicated for steaming and not intended for steaming and baking in which the surface of the food is browned. Because of this, the food plate is not heated even if the microwaves are radiated, thus making it impossible to steam and bake the food to brown the surface of the food held in contact with the food plate.
In the steaming and baking utensil as disclosed in Patent Document 2, the lid having the steam inlet to introduce water vapor must be placed on the food before heating. Accordingly, the state of the food during heating cannot be visually checked and, upon completion of the heating, the steaming and baking utensil is first taken out from the heating chamber and the lid is subsequently removed, thus resulting in a non-user-friendly utensil.
Also, because the steaming and baking utensil is accommodated with the heating chamber with the lid placed thereon, there are restrictions in area of the utensil that can be placed on the cooking dish and in height of the food and, hence, a large food cannot be accommodated in the utensil, thus posing a problem that nothing but only low foods can be heated.
Further, because the food placed on the cooking dish is covered with the metallic lid, the food cannot be directly heated with the microwaves.
EP 1 741 986 A1 describes a cooking apparatus and cooking method which when an object to be heated is heated using steam, sets the atmospheric temperature of the interior of the heating chamber quickly and accurately at a temperature suitable for cooking to thereby cook the object to be heated with uniform steam heating. In this respect, it is described a cooking apparatus for supplying steam to a heating chamber storing an object to be heated to thereby heat the object to be heated, which comprises steam supply means for supplying steam to the heating chamber, a fan for stirring up the steam supplied to the interior of the heating chamber, and temperature control means, by driving and rotating the fan, for controlling the atmospheric temperature of the interior of the heating chamber to be lower than the temperature of the steam supplied.
EP 1 767 860 A1 describes a method of operating an oven and controlling the introduction of conventional heat, microwave energy and steam to achieve optimal cooking results. The oven includes a heating system, a microwave system and a steam system. A control panel is provide for inputting data to a controller. The oven operates according to a method which includes first inputting information regarding food type and at least one additional parameter. The duration of a first cooking step and a second cooking step are then calculated. Steam is introduced into the oven cavity during the first cooking step while operating the heating system to heat the oven cavity to an oven set point temperature. After the first cooking step, the microwave system is energized for a first portion of the second cooking step while maintaining the oven cavity at the oven set point temperature. The heating system is deenergized at the end of the second cooking step. The one additional parameter is preferably a data input corresponding to the weight and/or size of the food item. The controller determines an overall cooking period and the duration of the first cooking step is a fraction or percentage of the overall cooking period where the fraction or percentage of the overall cooking period is controlled according to the input food type.
EP 1 458 220 A1 describes a high frequency heating apparatus having a high frequency generating portion and a steam generating portion for generating steam into a heating chamber for accommodating a thing to be heated and serving to supply at least one of a high frequency and steam into the heating chamber, thereby heating the thing to heated, includes a pan which serves to mount the thing to be heated thereon and is provided to be upward removable apart from a bottom face of the heating chamber at a predetermined interval, thereby dividing the space in the heating chamber, steam delivery means for supplying the steam generated by the steam generating portion into the upper space positioned above the pan, and preheating means for raising the temperature in the heating chamber.
US-6,040,564 A describes a microwave heating apparatus and microwave heating method to heat a food or other object to be heated favorably by means of microwaves while enclosing the food with superheated steam. The apparatus comprises a heating chamber in which an object to be heated is put, steam generating means for supplying superheated steam to the heating chamber, superheated steam maintaining means provided in the heating chamber to prevent the temperature of the superheated steam from lowering, and microwave generating means for irradiating the object with microwaves, whereby the object placed in the heating chamber is heated in superheated steam with microwaves, so that the food is efficiently heated from inside and outside and the food is not wetted.

Patent Document 1: JP 4033778 B
Patent Document 2: JP 2011-241987 A
Patent Document 3: EP 1 741 986 A1
Patent Document 4: EP 1 767 860 A1
Patent Document 5: EP 1 458 220 A1
Patent Document 6: US-6,040,564 A

SUMMARY OF THE INVENTION

The invention is defined by the subject-matter of independent claim 1. The dependent claims are directed to advantageous embodiments.

ADVANTAGES OF THE INVENTION

Advantageously, it is provided a high-frequency heating cooker capable of quickly and easily obtaining a delicious steamed food or steamed and baked food with a favorable finish by effectively controlling supply of water vapor and microwaves using a cooking dish that does not require a lid.
Advantageously, it is provided a high-frequency heating cooker which comprises:

a heating chamber for accommodating an object to be heated therein;
a microwave generator which generates microwaves to be supplied into the heating chamber;
a plurality of support portions provided on right and left side walls of the heating chamber opposed to each other;
a cooking dish detachably supported on the support portions to vertically partition the heating chamber;
a high-frequency heating element mounted to a bottom surface of the cooking dish;
an exciting portion which radiates the microwaves generated by the microwave generator to a space inside the heating chamber below the cooking dish;
a water vapor generator;
a water vapor vent open to a space inside the heating chamber above the cooking dish to allow the water vapor generated by the water vapor generator to be ejected into the heating chamber;
an operating portion for inputting information associated with a heating treatment of the object to be heated;
a controller which controls a heating operation with respect to the object to be heated based on the information associated with the heating treatment inputted by the operating portion;
when the information associated with the heating treatment inputted by the operating portion is information associated with cooking with steam, the controller controls so as to steam the object to be heated by conducting a first heating treatment, in which the water vapor generator is driven to supply water vapor into the heating chamber via the water vapor vent to heat the object to be heated placed on the cooking dish with the water vapor, and a second heating treatment in which after the first heating treatment, the microwave generator is driven to heat the high-frequency heating element and the object to be heated placed on the cooking dish with microwaves.

The high-frequency heating cooker according to the present disclosures can provide a high-frequency heating cooker capable of quickly and easily obtaining a delicious steamed food or steamed and baked food with a favorable finish by effectively controlling supply of water vapor and microwaves using a cooking dish that does not require a lid.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a perspective view of a high-frequency heating cooker according to a first embodiment of the present invention with a door opened.
Fig. 2 is a perspective view of the high-frequency heating cooker of Fig. 1 as viewed from a steam generator side with an outer casing removed.
Fig. 3 is a perspective view of the high-frequency heating cooker of Fig. 2 with the door opened.
Fig. 4 is a cross-sectional view of the high-frequency heating cooker of Fig. 1 taken in a front-back direction (a direction from a front portion of the high-frequency heating cooker towards the back of a heating chamber).
Fig. 5 is a functional block diagram of the high-frequency heating cooker of Fig. 1.
Fig. 6 depicts illustrations indicating temperature changes in the heating chamber and those of an object to be heated during steaming when the cooker of Fig. 1 was used.
Fig. 7 depicts illustrations indicating temperature changes in the heating chamber and those of an object to be heated during steaming and baking when a high-frequency heating cooker according to a second embodiment of the present invention was used.

DESCRIPTION OF examples

The first example is directed to a high-frequency heating cooker comprising:

a heating chamber for accommodating an object to be heated therein;
a microwave generator which generates microwaves to be supplied into the heating chamber;
a plurality of support portions provided on right and left side walls of the heating chamber opposed to each other;
a cooking dish detachably supported on the support portions to vertically partition the heating chamber;
a high-frequency heating element mounted to a bottom surface of the cooking dish;
an exciting portion which radiates the microwaves generated by the microwave generator to a space inside the heating chamber below the cooking dish;
a water vapor generator;
a water vapor vent open to a space inside the heating chamber above the cooking dish to allow the water vapor generated by the water vapor generator to be ejected into the heating chamber;
an operating portion for inputting information associated with a heating treatment of the object to be heated, and
a controller which controls a heating operation with respect to the object to be heated based on the information associated with the heating treatment inputted by the operating portion, wherein
when the information associated with the heating treatment inputted by the operating portion is information associated with cooking with steam, the controller controls so as to steam the object to be heated by conducting a first heating treatment, in which the water vapor generator is driven to supply water vapor into the heating chamber via the water vapor vent to heat the object to be heated placed on the cooking dish with the water vapor, and a second heating treatment in which after the first heating treatment, the microwave generator is driven to heat the high-frequency heating element and the object to be heated placed on the cooking dish with microwaves.

By this configuration, in the first heating treatment, the object to be heated is heated from the surface with the water vapor to thereby reduce drying of the surface of the object to be heated to retain the surface in a moist state. In the subsequent second heating treatment, because the microwaves are propagated into the space filled with the water vapor, the distribution of the microwaves is uniformed and, accordingly, the temperature of the object to be heated can be uniformly increased, thus resulting in a reduction in cooking time.
Also, because the cooking dish is heated with the microwaves, heating of the object to be heated from a bottom surface is promoted, thereby making it possible to promote a temperature increase of the bottom surface of the object to be heated, which is in contact with the cooking dish and not in direct contact with the water vapor and accordingly difficult to increase in temperature, as compared with an upper surface of the object to be heated that is exposed to the water vapor. Accordingly, a temperature difference between the inside and outside of the object to be heated is reduced and the entire object to be heated is enclosed by an environment of uniform temperature, thus making it possible to prepare a steamed food with a favorable finish in a short period of time.
In the high-frequency heating cooker of the first example, the second example is characterized in that when the information associated with the heating treatment inputted by the operating portion is information associated with steaming and baking, the controller controls so as to steam and bake the object to be heated by conducting, after the first heating treatment and the second heating treatment, a third heating treatment in which the drive of the microwave generator is continued to continuously heat the high-frequency heating element and the object to be heated placed on the cooking dish with the microwaves to evaporate water stored in the cooking dish, and then the drive of the microwave generator is further continued to increase a temperature of the cooking dish over 100°C to brown a bottom surface of the object to be heated.
By this configuration, the third heating treatment is conducted after the first and second heating treatments to evaporate water stored in the cooking dish and increase the temperature of the cooking dish over 100°C, thus making it possible to bake the bottom surface of the object to be heated until it is crispy.
In the high-frequency heating cooker of the first or second example the third example is characterized in that even in the second heating treatment, the drive of the water generator is continued to heat the object to be heated placed on the cooking dish with the water vapor and the microwaves.
By this configuration, in the second heating treatment, the object to be heated can be uniformly and quickly steamed with the water vapor and the microwaves with an atmosphere around the object to be heated retained in a state filled with the water vapor.
In the high-frequency heating cooker of any one of the first through third examples, the fourth example is characterized in that the cooking dish is made of a material that does not allow transmission of the microwaves.
This configuration allows the microwaves to enter the object to be heated placed on the cooking dish from a void space between a wall surface of the heating chamber and the cooking dish to directly heat the object to be heated with the microwaves, thereby enabling direct heating with an appropriate amount of microwaves. Also, the high-frequency heating element mounted to the outer bottom surface of the cooking dish effectively absorbs the microwaves to rapidly generate heat, which is in turn efficiently conducted to the cooking dish.
In the high-frequency heating cooker of any one of the first through fourth examples, the fifth example is characterized in that the exciting portion comprises a rotational antenna having a directivity in a specific radial direction.
This configuration allows the microwaves radiated into the heating chamber to be concentrated on the heating element mounted to the outer bottom surface of the cooking dish or radiated so that many microwaves may reach an upper side of the cooking dish via a void space, thereby making it possible to effectively control the radiation direction of the microwaves depending on the object to be heated.
in the high-frequency heating cooker of any one of the first through fifth examples, the sixth example further comprises a radiant heat supply portion disposed above the heating chamber to heat the object to be heated with heat radiation different from the microwaves.
By this configuration, an upper wall of the heating chamber can be preheated for prevention of dew condensation on the upper wall and further an upper surface of the object to be heated can be browned.
In the high-frequency heating cooker of any one of the first through sixth examples, the seventh example further comprises a convective heat supply portion for generating convective heat that is supplied into the heating chamber.
By this configuration, all walls of the heating chamber can be preheated for prevention of dew condensation on all the walls and further the object to be heated can be baked with convective heat after supply of the water vapor into the heating chamber has been reduced.
In the high-frequency heating cooker of any one of the first through seventh examples, the eighth example further comprises a circulating fan which agitates and circulates a gas inside the heating chamber.
By this configuration, the density of the water vapor or the temperature in the heating chamber can be uniformed by agitating the water vapor that permeates the heating chamber.
In the high-frequency heating cooker of any one of the first through eighth examples, the ninth example further comprises a temperature detector which detects a temperature inside the heating chamber, wherein the controller controls the microwave generator and the water vapor generator based on a temperature detected by the temperature detector, and/or the controller controls any one or more of the radiant heat supply portion, the convective heat supply portion and the circulating fan based on a temperature detected by the temperature detector.
This configuration allows control of the heating means to be switched at the optimum timing during heating and, hence, even if heating conditions such as, for example, the amount of the object to be heated, the temperature at the start of cooking, and the like change, favorable cooking can be conducted to appropriately accommodate such changes.
Embodiments of the present invention are explained hereinafter with reference to the drawings, but the present invention is not limited by the embodiments.

(Embodiment 1)

Fig. 1 is a perspective view of a high-frequency heating cooker according to a first embodiment of the present invention with a door opened, Fig. 2 is a perspective view of the high-frequency heating cooker according to the first embodiment of the present invention as viewed from a steam generator side with an outer casing removed, and Fig. 3 is a perspective view of the high-frequency heating cooker of Fig. 2 with the door opened.
As shown in Figs. 1 to 3, a high-frequency heating cooker has a main body 1 and a heating chamber 2 defined in the main body 1 to form a heating space. The heating chamber 2 has an external appearance generally in the form of a rectangular parallelepiped and is provided with a door 3 employed as an opening and closing wall through which an object to be heated is taken in and out of the heating chamber 2. By this configuration, radiated microwaves are substantially confined within the heating chamber 2. An operating portion or panel 4 is provided on the front side of the main body 1 of the high-frequency heating cooker and, for example, on the side (right side) of the door 3. The operating panel 4 is provided with a start switch 5a for ordering the start of a heating treatment, a cancelling switch 5b for ordering completion of the heating treatment, an indicator 5c, a dial 5d for selecting an automatic cooking program prepared in advance or for manual manipulation, and the like. A high-frequency (microwaves) exciting potion 7 for radiating microwaves into the heating chamber 2 is provided generally at a central portion of a bottom wall 6 (below a closure member 11).
A magnetron 8 is employed as a high-frequency generator to generate microwaves that are radiated into the heating chamber 2. The microwaves radiated from the magnetron 8 pass through a waveguide 9 before they are introduced to the exciting portion 7. The waveguide 9 is of a rotary drive type to radiate the microwaves into the heating chamber 2 and, by this configuration, the exciting portion 7 acts as a radiation antenna having a directivity in a specific radial direction in a rotational trajectory circle. Also, an output shaft of a motor 10 employed as a drive portion for rotationally driving the radiation antenna is inserted into and mounted to a connecting shaft of the radiation antenna of the exciting portion 7.
The radiation antenna has a directivity in a specific radial direction in a rotational position thereof and the direction in which the microwaves are strongly radiated can be controlled by controlling the rotational position. As the radiation antenna having such a directivity, a single rotational antenna may be used or otherwise a plurality of rotational antennas may be used.
The closure member 11 is disposed immediately above the radiation antenna, i.e., the exciting portion 7. The closure member 11 is made of a ceramic- or glass-based low-loss dielectric material in the form of a plate that can allow microwaves to easily transmit therethrough.
Three pairs of support portions including upper support portions 16a, 16b, middle support portions 17a, 17b and lower support portions 18a, 18b are provided on a right side wall 12 and a left side wall 13 of the heating chamber 2 to support a cooking dish 15 having an outer bottom surface to which a high-frequency heating element 14 has been mounted.
As shown in Fig. 4, a radiant heat supply portion 19 is provided on an upper side within the heating chamber 2. The radiant heat supply portion 19 is one of heating means to heat an object to be heated by making use of heat radiation different from microwaves. A convective heat supply portion 21 is provided outside a rear wall 20 of the heating chamber 2. The convective heat supply portion 21 generates convective heat to supply it into the heating chamber 2. A circulating fan 22 is mounted on the rear wall 20 to agitate and circulate a gas within the heating chamber 2.
A water tank 23 for accommodating water therein to generate water vapor is disposed below the closure member 11 and the water within the water tank 23 is sent to a water vapor generator 24 disposed outside the left side wall 13 of the heating chamber 2 by a pump motor. The water sent to the water vapor generator 24 is heated and turned into water vapor and increased in volume. The water vapor is then ejected into the heating chamber 2 from a water vapor vent 26 through a water vapor guide pipe 25 and eventually fed into the heating chamber 2. The water vapor vent 26 is formed in the left side wall 13 of the heating chamber 2 so as to open to a space within the heating chamber 2 above the cooking dish 15 supported by the upper support portions 16a, 16b.
Fig. 5 depicts a functional block diagram of the high-frequency heating cooker according to the first embodiment of the present invention. As shown in Fig. 5, a controller 27 outputs a control signal based on information that has been inputted by a user using an operating portion on the operating panel 4 mounted to the main body 1 of the high-frequency heating cooker. The water vapor generator 24, the magnetron 8, the radiant heat supply portion 19 and the convective heat supply portion 21 are controlled based on the control signal outputted from the controller 27. The main body 1 of the high-frequency heating cooker is also provided with a temperature detector 28 to detect the temperature inside the heating chamber 2 (for example, the temperature of a heating region above the cooking dish 15). Temperature information of the heating region detected by the temperature detector 28 is inputted to the controller 27 and, based on such temperature information, the heating means of the water vapor generator 24, that of the magnetron 8, that of the radiant heat supply portion 19 and that of the convective heat supply portion 21 are controlled. Instead of this, the heating means of at least one of the water vapor generator 24, the magnetron 8, the radiant heat supply portion 19 and the convective heat supply portion 21 may be controlled based on the temperature information.
The operation and function of the high-frequency heating cooker of the above-described construction according to the first embodiment are explained hereinafter.
Handmade shao-mais (which are one kind of Chinese dumplings) as an object to be heated are first placed on the metallic cooking dish 15 having the high-frequency heating element 14 mounted to the outer bottom surface thereof and the cooking dish 15 is subsequently supported on the upper support portions 16a, 16b of the heating chamber 2. An item "handmade shao-mai" listed in an automatic cooking program is then selected using the dial 5d provided on the operating panel 4. When the start switch 5a is turned on, the controller 27 controls the water vapor generator 24 to generate water vapor based on a control program (control sequence) stored in advance. The water vapor so generated is then ejected from the water vapor vent 26 via the water vapor guide pipe 25 and supplied into the heating chamber 2. At this moment, the cooking dish 15 vertically partitions the heating chamber 2 into two compartments such that an upper compartment, i.e., a heating region (heating space) above the cooking dish 15 may be about one third of the entire heating chamber 2.
As a result, the heating region above the cooking dish 15 is filled with the supplied water vapor in about two minutes. Further, when the water vapor is continuously supplied, the temperature of the heating region continues to increase and the density of saturated water vapor increases until the temperature of the heating region reaches about 100°C. The object to be heated is heated from the surface by latent heat of the water vapor and the temperature thereof increases with time. At the same time, the water vapor condenses on the surface of the object to be heated and turns into dew condensation water as if a film of hot water has been formed on the surface. In a high-temperature environment and in the presence of water, starchy skins of the shao-mais are heated until it is completely gelatinized so as to be transparent and radiant and have a smooth texture. Heating the object to be heated with the use of water vapor and not microwaves is a first heating treatment.
On the other hand, the temperature of a central portion of the object to be heated or that of a bottom portion of the object that is not directly held in contact with steam increases more slowly than that of the surface of the object.
Also, the water vapor ejected in the heating region above the cooking dish 15 causes uneven heating in varying degrees. A power source for driving the magnetron 8 is therefore controlled to generate microwaves, which are then introduced into the waveguide 9 and radiated into the heating chamber 2 from the radiation antenna of the exciting portion 7.
The high-frequency heating element 14 mounted to the outer bottom surface of the cooking dish 15 absorbs part of the radiated microwaves and generates heat, and the bottom surface of the object to be heated is heated by conductive heat. The conductive heat also acts to heat water condensed in the cooking dish 15 and evaporate it again.
By making use of the directivity of the exciting portion 7, i.e., the radiation antenna, the rotational position of the radiation antenna is controlled so that the radiated microwaves may reach the heating region above the cooking dish 15 as many as possible through void spaces between the cooking dish 15 and inner surfaces of the right side wall 12, the left side wall 13 and the rear wall 20 of the heating chamber 2 and a void space between the cooking dish 15 and the door 3. Having reached the heating region above the cooking dish 15, the microwaves directly heat the object having much moisture on the surface thereof. The microwaves also heat and evaporate dew condensation water stored in the cooking dish 15. The upper heating region partitioned by the cooking dish 15 is filled with high-density water vapor and the propagation of microwaves through a space filled with water vapor makes the microwave distribution uniform, thus making it possible to uniformly heat the object to be heated using the microwaves that have entered the heating region through the void spaces. The rotational position of the radiation antenna or the exciting portion 7 is controlled by the controller 27 depending on a case where the radiational directivity of microwaves towards the high-frequency heating element 14 of the cooking dish 15 is strengthened or a case where the amount of microwaves that can reach the heating region above the cooking dish 15 is increased.
After completion of the first heating treatment, heating the object to be heated in the above-described manner, in which the object to be heated is indirectly heated by the microwaves via the cooking dish 15 and directly heated by the microwaves that have entered the heating region above the cooking dish 15, is a second heating treatment. In the second heating treatment, the object to be heated is heated by the microwaves by bringing the water vapor generator 24 to a stop (by stopping supplying water vapor). The second heating treatment is not limited to such a case, but in the second heating treatment, the object to be heated may be heated by the water vapor and the microwaves by continuing the drive of the water vapor generator 24 to continuously heat the object to be heated with the use of the water vapor. In this case, the heating of the object to be heated can be further promoted in the second heating treatment with the object encircled by the high-density water vapor.
Fig. 6 depicts temperature changes with time when steaming was conducted. Handmade shao-mais were employed as the object to be heated and placed on the cooking dish 15, which was in turn supported on the upper supporting portions 16a, 16b of the heating chamber 2. In Fig. 6, Example 1 is a case where the shao-mais were cooked with steam by conducting the first heating treatment and the second heating treatment, while Comparative Example 1 is a case where the shao-mais were cooked with steam using only water vapor and not microwaves. In Fig 6, (A) indicates changes in internal temperature of the shao-mai (food temperature 1), (B) indicates changes in bottom temperature of the shao-mai (food temperature 2), (C) indicates changes in temperature of the cooking dish 15, and (D) indicates changes in temperature of the heating chamber (heating region above the cooking dish 15). In Fig. 6 thick lines indicate Example 1 and thin lines indicate Comparative Example 1. The temperature changes during microwave-cooking were measured using a fiber-optic thermometer.
In Example 1, the shao-mais were heated with only water vapor in the first heating treatment, which was then switched to the second heating treatment, in which the shao-mais were heated with only microwaves, by stopping supply of the water vapor after eight minutes from the start of heating. On the other hand, in Comparative Example 1, the heating treatment was conducted with only water vapor by continuously supplying the water vapor from the start of heating.
As shown in Fig. 6(D), in both Example 1 and Comparative Example 1, the temperature of the heating chamber reaches about 100°C, but Fig. 6(C) reveals that in Example 1, when the first heating treatment is switched to the microwave-heating (second heating treatment) after the heating chamber has been fully filled with the water vapor, the cooking dish 15 rapidly generates heat and the temperature thereof increases to efficiently increase the bottom temperature of the shao-mai (see Fig. 6(B), food temperature 2).
Accordingly, in Example 1 in comparison with Comparative Example 1, after the surfaces of the shao-mais have been gelatinized by heating the shao-mais with the water vapor in the first heating treatment, it is further heated with the microwaves in the second heating treatment, thereby making it possible to reduce the heating time and conduct favorable cooking (steaming) without any temperature variations.

(Embodiment 2)

A high-frequency heating cooker according to a second embodiment of the present invention is explained hereinafter. Because the high-frequency heating cooker according to this second embodiment differs in the control sequence of the controller 27 from the high-frequency heating cooker according to the first embodiment referred to above and other configurations are the same, the following explanation is made focusing on different points.
Jiao-zis (which are another kind of Chinese dumplings) employed as an object to be heated are first placed on the metallic cooking dish 15 having the high-frequency heating element 14 mounted to the outer bottom surface thereof and the cooking dish 15 is subsequently supported on the upper support portions 16a, 16b of the heating chamber 2. An item "steamed and baked jiao-zi" listed in an automatic cooking program is then selected using the dial 5d provided on the operating panel 4. When the start switch 5a is turned on, the controller 27 runs a control program (control sequence) stored in advance. More specifically, the controller 27 controls the water vapor generator 24 to generate water vapor, which is then ejected from the water vapor vent 26 via the water vapor guide pipe 25 and supplied into the heating chamber 2. At this moment, the cooking dish 15 vertically partitions the heating chamber 2 into two compartments such that the heating region above the cooking dish 15 may be about one third of the entire heating chamber 2.
As a result, the heating region above the cooking dish 15 is filled with the supplied water vapor in about two minutes. Further, when the water vapor is continuously supplied, the temperature of the heating region continues to increase and the density of saturated water vapor increases until the temperature of the heating region reaches about 100°C. The object to be heated is heated from the surface by latent heat of the water vapor and the temperature thereof increases with time. At the same time, the water vapor condenses on the surface of the object to be heated and turns into dew condensation water as if a film of hot water has been formed on the surface. In a high-temperature environment and in the presence of water, starchy skins of the jiao-zis are heated until they are completely gelatinized so as to be transparent and radiant and have a smooth texture. The first heating treatment is conducted in this way without the use of microwaves.
On the other hand, the temperature of a central portion of the object to be heated or that of a bottom portion of the object that is not in contact with steam is lower than the surface temperature and, hence, the heating treatment with the use of only water vapor cannot burn or brown the bottom surfaces of the jiao-zis. Also, uneven heating occurs in varying degrees depending on the position where the jiao-zis are placed.
When the power source for driving the magnetron 8 is controlled to generate microwaves from the magnetron 8, the microwaves are guided via the waveguide 9 and radiated into the heating chamber 2 from the exciting portion 7, i.e., the radiation antenna.
In this event, by making use of the directivity of the exciting portion 7 or the radiation antenna, the rotational position of the radiation antenna is controlled so that the microwaves may be radiated towards the high-frequency heating element 14 mounted to the bottom surface of the cooking dish 15 as many as possible. As a result, the high-frequency heating element 14 rapidly generates heat and increases the temperature of the cooking dish 15 up to about 100°C to heat the object to be heated via the cooking dish 15 and, at the same time, the object to be heated is also heated with the microwaves that have entered the heating region above the cooking dish 15 (second heating treatment).
Thereafter, water condensed and stored in the cooking dish 15 evaporates actively and when the cooking dish 15 has been emptied of water, the temperature of the cooking dish 15 increases again and reaches a hundred and several tens of degrees C after a few minutes. In this way, the bottom surface of the object to be heated in contact with the cooking dish 15 is heated and browned so as to have a fragrant flavor as if it is steamed and baked on an iron plate or frying pan (third heating treatment).
Although part of the microwaves enter the heating region above the cooking dish 15, this heating region is filled with high-density water vapor and, hence, the distribution of the microwaves that have entered the heating region is uniformed, thereby making it possible to promote uniform heating of the object to be heated and evaporate extra moisture adhering to the object surface or dew condensation water stored in the cooking dish 15 again.
Fig. 7 depicts temperature changes of the inside of a jiao-zi (jiao-zi 1), a bottom portion of the jiao-zi (jiao-zi 2), the cooking dish 15 and the heating chamber 2 (heating region above the cooking dish 15) in Example 2, in which the jiao-zis were steamed and baked by conducting the first to third heating treatments in the second embodiment referred to above.
In the steaming and baking according to the second embodiment, the object to be heated is heated with water vapor at the beginning of the heating (first heating treatment) and then heated with microwaves after six minutes (second heating treatment). When the temperature in the heating chamber 2 reaches about 100°C and the heating chamber 2 is filled with the water vapor, the steam-heating is switched to the microwave-heating whereby the temperature of the cooking dish 15, which has not been heated up to 100°C, rapidly increases and reaches about 100°C. The microwave-heating is further continued, but the temperature of the cooking dish 15 is maintained at about 100°C while water stored in the cooking dish 15 still exists. When the cooking dish 15 is emptied of water upon evaporation, the temperature of the cooking dish 15 increases again and reaches a hundred and several tens of degrees C (third heating treatment). By doing so, the bottom surfaces of the jiao-zis can be browned.
Accordingly, by first heating the object to be heated with water vapor to gelatinize the surface thereof and by subsequently heating it with microwaves, upper skins of the jiao-zis are moisturized and steamed softly and bottom surfaces of the jiao-zis are browned. In this way, favorable steaming and baking can be completed in a short period of time.

(Embodiment 3)

A high-frequency heating cooker according to a third embodiment of the present invention is explained hereinafter. Because the high-frequency heating cooker according to this third embodiment differs in the control sequence of the controller 27 or the like from the high-frequency heating cooker according to the first embodiment referred to above and other configurations are the same, the following explanation is made focusing on different points.
A sizable lump of meat (pork) employed as an object to be heated is first placed on the cooking dish 15 having the high-frequency heating element 14 mounted to the outer bottom surface thereof and the cooking dish 15 is subsequently supported on the middle support portions 17a, 17b of the heating chamber 2. An item "steamed pork" listed in an automatic cooking program is then selected using the dial 5d provided on the operating panel 4. When the start switch 5a is turned on, the controller 27 runs a control program stored in advance. More specifically, the controller 27 controls the water vapor generator 24 to generate water vapor, which is then ejected from the water vapor vent 26 via the water vapor guide pipe 25 and supplied into the heating chamber 2, thereby initiating the heating treatment of the object to be heated with water vapor (first heating treatment). At this moment, the cooking dish 15 vertically partitions the heating chamber 2 into two compartments such that the heating region above the cooking dish 15 may be about half of the entire heating chamber 2.
As a result, the heating region above the cooking dish 15 is filled with the supplied water vapor in about three minutes. If the lump of pork is heated with only water vapor, it requires several tens of minutes before the internal temperature thereof reaches 75°C or more at which it can be eaten. When the heating region above the cooking dish 15 is filled with the water vapor, supply of microwaves is started with a reduction in the amount of supply of the water vapor so that the inside and outside of the object to be heated may be efficiently heated by continuously and simultaneously supplying the water vapor and the microwaves (second heating treatment). In this way, the temperature of the heating region continues to increase and the density of saturated water vapor gradually increases until the temperature of the heating region reaches about 100°C and, at the same time, the water vapor is present around the object to be heated at a high density, thus making it possible to uniform the distribution of the microwaves that have entered the heating region to uniformly heat the object to be heated.

(Embodiment 4)

A high-frequency heating cooker according to a fourth embodiment of the present invention is explained hereinafter. Because the high-frequency heating cooker according to this fourth embodiment differs in the control sequence of the controller 27 from the high-frequency heating cooker according to the first embodiment referred to above and other configurations are the same, the following explanation is made focusing on different points.
A fish employed as an object to be heated is first placed on the cooking dish 15 having the high-frequency heating element 14 mounted to the outer bottom surface thereof and the cooking dish 15 is subsequently supported on the upper support portions 16a, 16b of the heating chamber 2. An item "steamed and baked fish" listed in an automatic cooking program is then selected using the dial 5d provided on the operating panel 4. When the start switch 5a is turned on, the controller 27 runs a control program stored in advance. More specifically, the controller 27 controls the water vapor generator 24 to generate water vapor, which is then ejected from the water vapor vent 26 via the water vapor guide pipe 25 and supplied into the heating chamber 2, thereby initiating a heating treatment of the object to be heated with water vapor (first heating treatment). When a predetermined period of time has elapsed after the start of the first heating treatment, the controller 27 controls the power source for driving the magnetron 8 to generate microwaves, which are then introduced into the water vapor guide pipe 25 and radiated into the heating chamber 2 from the exciting portion 7 or the radiation antenna. The microwaves so radiated into the heating chamber 2 heat the high-frequency heating element 14 mounted to the outer bottom surface of the cooking dish 15 to heat the object to be heated via the cooking dish 15 and, at the same time, part of the microwaves enter the heating region above the cooking dish 15 to directly heat the object to be heated (second heating treatment).
in this event, by making use of the directivity of the exciting portion 7 or the radiation antenna, the rotational position of the radiation antenna is controlled so that the microwaves may be radiated towards the high-frequency heating element 14 mounted to the outer bottom surface of the cooking dish 15 as many as possible. As a result, the cooking dish 15 rapidly generates heat and increases the temperature of the cooking dish 15 over, for example, about 100°C to heat and brown a bottom surface of the fish (third heating treatment).
Also, the controller 27 controls the radiant heat supply portion 19 provided above the heating chamber 2 to radiationally heat an upper surface of the fish. By steaming the fish softly and browning the upper surface thereof well, a steamed and baked fish having a soft texture and a fragrant flavor can be obtained.

(Embodiment 5)

A high-frequency heating cooker according to a fifth embodiment of the present invention is explained hereinafter. Because the high-frequency heating cooker according to this fifth embodiment differs in the control sequence of the controller 27 from the high-frequency heating cooker according to the first embodiment referred to above and other configurations are the same, the following explanation is made focusing on different points.
An egg hotchpotch employed as an object to be heated is first placed on the cooking dish 15 having the high-frequency heating element 14 mounted to the outer bottom surface thereof and the cooking dish 15 is subsequently supported on the middle support portions 17a, 17b of the heating chamber 2. An item "steamed egg hotchpotch" listed in an automatic cooking program is then selected using the dial 5d provided on the operating panel 4. When the start switch 5a is turned on, the controller 27 runs a control program stored in advance. Specifically, the controller 27 controls the radiant heat supply portion 19 to preheat an upper surface of the heating chamber 2.
The controller 27 further controls the convective heat supply portion 21 and the circulating fan 22 to preheat the entire heating chamber 2. Preheating the heating chamber 2 can restrain water vapor from condensing on inner wall surfaces of the heating chamber 2 and on the cooking dish 15 to efficiently heat the object to be heated with the supplied water vapor. The object contained in a vessel such as the egg hotchpotch is not damaged even if it is heated with convective heat or radiant heat in a short period of time. When the preheating is completed at a temperature suited to heat the egg hotchpotch, the controller 27 controls the water vapor generator 24 to generate water vapor, which is then ejected from the water vapor vent 26 via the water vapor guide pipe 25 and supplied into the heating chamber 2, thereby initiating the heating treatment of the object to be heated with water vapor (first heating treatment).
At this moment, the cooking dish 15 vertically partitions the heating chamber 2 into two compartments such that the heating region above the cooking dish 15 may be about half of the entire heating chamber 2. As a result, the heating region above the cooking dish 15 is filled with the supplied water vapor in about three minutes. When the heating region is filled with the water vapor, supply of microwaves is started with a reduction in the amount of supply of the water vapor so that the egg hotchpotch may be efficiently heated from the inside and outside by continuously and simultaneously supplying the water vapor and the microwaves (second heating treatment). Because the upper heating region partitioned by the cooking dish 15 is filled with high-density water vapor, the distribution of the microwaves that have entered the heating region is uniformed, thus making it possible to uniformly heat the object to be heated.
Also, if the circulating fan 22 is appropriately controlled to agitate the water vapor within the heating chamber 2, a temperature difference between upper and lower portions of the egg hotchpotch or uneven heating, which may be due to the places where a plurality of egg hotchpotches are placed, is improved, thus resulting in more uniform heating.
As described above, after the heating chamber 2 has been preheated using the radiant heat supply portion 19 and the convective heat supply portion 21, the object to be heated is heated with the water vapor and the microwaves, thereby making it possible to reduce the heating time and favorably cook the egg hotchpotch without any temperature variations. Also, because the object to be heated can be heated with a reduction in the amount of water vapor, not only can the volume of the water tank 23 be reduced, but the amount of dew condensation water remaining in the heating chamber 2 can be also reduced.
Further, if an egg liquid in the steamed egg hotchpotch reaches about 85°C or more, bubbling may occur to impair a smooth texture and, hence, a favorable finish can be obtained by controlling the heating region at a constant temperature using the temperature detector 28.

(Embodiment 6)

A high-frequency heating cooker according to a sixth embodiment of the present invention is explained hereinafter. Because the high-frequency heating cooker according to this sixth embodiment differs in the control sequence of the controller 27 from the high-frequency heating cooker according to the first embodiment referred to above and other configurations are the same, the following explanation is made focusing on different points.
Handmade shao-mais employed as an object to be heated are first placed on the metallic cooking dish 15 having the high-frequency heating element 14 mounted to the outer bottom surface thereof and the cooking dish 15 is subsequently supported on the upper support portions 16a, 16b of the heating chamber 2. An item "handmade shao-mai" listed in an automatic cooking program is then selected using the dial 5d provided on the operating panel 4. When the start switch 5a is turned on, the controller 27 runs a control program stored in advance. More specifically, the controller 27 controls the water vapor generator 24 to generate water vapor, which is then ejected from the water vapor vent 26 via the water vapor guide pipe 25 and supplied into the heating chamber 2, thereby initiating a heating treatment of the object to be heated with water vapor (first heating treatment). At this moment, the cooking dish 15 vertically partitions the heating chamber 2 into two compartments such that the heating region above the cooking dish 15 may be about one third of the entire heating chamber 2. As a result, the heating region above the cooking dish 15 is filled with the supplied water vapor in about two minutes.
Further, when the water vapor is continuously supplied, the temperature of the heating region continues to increase and the density of saturated water vapor increases until the temperature of the heating region reaches about 100°C. When the temperature detector 28 detects that the temperature of the heating region has reached about 100°C, the power source for driving the magnetron 8 is controlled to generate microwaves and supply of the water vapor is stopped. In this way, the heating means is switched to subsequently heat the object to be heated with the microwaves (second heating treatment). Even if the object to be heated is substantial in amount or even if the temperature of a surrounding environment is low and, accordingly, the temperature in the heating chamber increases slowly, the heating style can be switched to the microwave-heating after the temperature detector 28 has detected that the temperature in the heating chamber has reached about 100°C, thus making it possible to obtain a stable finish that is unlikely to be affected by the amount of the object to be heated or the temperature of the surrounding environment.
Further, in a cold environment, the control may be such that the cooking dish 15 is first heated to avoid dew condensation by detecting that the temperature in the heating chamber at the start of heating is lower than a given level using the temperature detector 28 and by controlling the rotational antenna to radiate the microwaves towards the cooking dish 15 so as to focus the microwaves on the cooking dish 15, and water vapor is subsequently supplied to heat the food.
Any combination of the various embodiments referred to above can produce respective effects.
As described above, the high-frequency heating cooker according to the present invention can efficiently and uniformly heat the entire object to be heated with a reduction in time by combining cooking with water vapor (first heating treatment) with high-frequency heating with microwaves (second heating treatment). Further, because the amount and timing of supply of the microwaves are changed depending on cooking methods, a wide range of cooking is possible using the same cooking dish and without using different cooking dishes. The high-frequency heating cooker according to the present invention is also effective in reducing the amount of water to be used and the amount of dew condensation water remaining in the heating chamber and effectively utilized in the field associated with high-frequency heating cookers for dielectric heating an object to be heated.

Explanation of reference numerals

1: main body of a high-frequency heating cooker
2: heating chamber
3: door
4: operating panel
5a: start switch
5b: cancelling switch
5c: indicator
5d: dial
6: bottom wall
7: exciting portion
8: magnetron
9: waveguide
10: motor
11: closure member
12: right side wall
13: left side wall
14: high-frequency heating element
15: cooking dish
16a, 16b: upper support portion
17a, 17b: middle support portion
18a, 18b: lower support portion
19: radiant heat supply portion
20: rear wall
21: convective heat supply portion
22: circulating fan
23: water tank
24: water vapor generator
25: water vapor guide pipe
26: water vapor vent
27: controller
28: temperature detector

Claims

A high-frequency heating cooker comprising:
a heating chamber (2) configured to accommodate an object to be heated therein;

a microwave generator (8) configured to generate microwaves to be supplied into the heating chamber (2);

a plurality of support portions (16a, 16b; 17a, 17b; 18a, 18b) provided on right and left side walls of the heating chamber (2) opposed to each other;

a cooking dish (15) detachably supported on the support portions (16a, 16b; 17a, 17b; 18a, 18b) to vertically partition the heating chamber (2), wherein the cooked dish(15) is configured to store dew condensation water;

a high-frequency heating element (14) mounted to a bottom surface of the cooking dish (15), the high-frequency heating element (14) being configured to absorb the supplied microwaves thereby generating heat;

an exciting portion (7) configured to radiate the microwaves generated by the microwave generator (8) to a space inside the heating chamber (2) below the cooking dish (15);

a water vapor generator (24) disposed outside the heating chamber;

a water vapor vent (26) open to a space inside the heating chamber (2) above the cooking dish (15) to allow the water vapor generated by the water vapor generator (24) to be ejected through a water vapor guide pipe into the heating chamber (2), the water vapor vent being provided on a side wall of the heating chamber;

an operating portion configured to input information associated with a heating treatment of the object to be heated;

a controller (27) configured to control a heating operation with respect to the object to be heated based on the information associated with the heating treatment inputted by the operating portion;

characterized in that

when the information associated with the heating treatment inputted by the operating portion is information associated with steaming and baking, the controller (27) is configured to control so as to heat the object to be heated by conducting:
a first heating treatment, in which the water vapor generator (24) is driven to supply water vapor into the heating chamber (2) via the water vapor vent (26) to fill a heating space above the cooking dish with the supplied water vapor and to heat the object to be heated placed on the cooking dish (15) with the use of the water vapor and not microwaves,

a second heating treatment in which after the first heating treatment, the microwave generator (8) is driven to heat the high-frequency heating element (14) and the object to be heated placed on the cooking dish (15) with microwaves, and

after the first heating treatment and the second heating treatment, a third heating treatment in which the drive of the microwave generator (8) is continued to continuously heat the high-frequency heating element (14) and the object to be heated placed on the cooking dish (15) with the microwaves to evaporate water stored in the cooking dish (15), and then the drive of the microwave generator (8) is further continued to increase a temperature of the cooking dish (15) over 100°C to brown a bottom surface of the object to be heated,

wherein even in the second heating treatment, the drive of the water generator is continued to heat the object to be heated placed on the cooking dish (15) with the water vapor and the microwaves.
The high-frequency heating cooker according to claim 1, wherein the cooking dish (15) is made of a material that does not allow transmission of the microwaves.
The high-frequency heating cooker according to claim 1 or 2, wherein the exciting portion (7) comprises a rotational antenna having a directivity in a specific radial direction.
The high-frequency heating cooker according to any one of claims 1 to 3, further comprising a radiant heat supply portion disposed above the heating chamber (2) to heat the object to be heated with heat radiation different from the microwaves.
The high-frequency heating cooker according to any one of claims 1 to 4, further comprising a convective heat supply portion for generating convective heat that is supplied into the heating chamber (2).
The high-frequency heating cooker according to any one of claims 1 to 5, further comprising a circulating fan which agitates and circulates a gas inside the heating chamber (2).
The high-frequency heating cooker according to any one of claims 1 to 6, further comprising a temperature detector (28) which detects a temperature inside the heating chamber (2), wherein the controller (27) controls the microwave generator (8) and the water vapor generator (24) based on a temperature detected by the temperature detector (28).