ELECTROMAGNETIC WAVE HEATING DEVICE

To realize a reduction in size of an electromagnetic wave heating system that utilizes water vapor. The electromagnetic wave heating system comprises a heat chamber having a first wall surface and a second wall surface different from the first wall surface, in which an object is placed to be heated, a flat antenna arranged on the first wall surface of the heat chamber and configured to emit an electromagnetic wave so as to heat an object inside the heating chamber, a discharger arranged on the second wall surface and configured to generate a discharge plasma by occurring a high voltage through a resonation structure of the electromagnetic wave, and an oscillator formed by a semiconductor element and configured to output the electromagnetic wave, and it is configured that the electromagnetic wave outputted from the oscillator is supplied into the flat antenna and the discharger.

TECHNICAL FIELD

The present invention relates to an electromagnetic wave heating system such as a microwave oven, and specifically relates to an electromagnetic wave heating system that heats food by using an array antenna for emitting an electromagnetic wave such as microwave and a discharger.

BACKGROUND ART

In these days, the microwave oven that uses the microwave generation device by using semiconductor element instead of magnetron has been considered (for example, referring to Patent Document 1).

Moreover, recently, the cooking heater that performs to cook with superheated steam, has been developed and put into commercial reality. For example, in Patent Document 2, water stored in tank is heated up by the heater so as to generate boiling water vapor, the water vapor is delivered to the heating room by the fan, and also delivered to the second heater for generating the superheated steam by superheating the water vapor. The superheated steam generated by the second heater is also delivered to the heating room, and the heat cooking is performed by using the water vapor and the superheated steam.

PRIOR ART DOCUMENTS

Patent Document 2: Unexamined patent application publication No. 2009-92376

SUMARRY OF INVENTION

Problem to be Solved by Invention

In Patent Document 2, the large sized fan for delivering the water vapor to the heating room, the pump for supplying water in tank into the heater, and two heaters, are required, and therefore, it is difficult to downsize the heat cooker for performing to heat by utilizing the water vapor.

The present invention is made from the above viewpoints.

An electromagnetic wave heating system of the present invention comprises a heat chamber having a first wall surface and a second wall surface different from the first wall surface, in which an object is placed to be heated, a flat antenna arranged on the first wall surface of the heat chamber and configured to emit an electromagnetic wave so as to heat an object inside the heat chamber, a discharger arranged on the second wall surface and configured to generate a discharge plasma by occurring a high voltage through a resonation structure of the electromagnetic wave, and an oscillator formed by a semiconductor element and configured to output the electromagnetic wave, and it is configured that the electromagnetic wave outputted from the oscillator is supplied into the flat antenna and the discharger.

EFFECT OF INVENTION

An electromagnetic wave heating system of the present invention can be utilized for cooking such as food prepared with eggs that requires accurate and precise heat control, since heating by a low temperature plasma as well as normal electromagnetic wave heating can be performed. Moreover, the low temperature plasma is generated by using a discharger provided with an electromagnetic wave resonation structure, and therefore, a flat antenna for electromagnetic wave heating and an oscillator can be commonalized. Accordingly, the heating by the low temperature plasma can be performed without enlarging in size the electromagnetic wave heating system.

EMBODIMENTS FOR IMPLEMENTING THE INVENTION

In below, embodiments of the present invention are described in details based on figures. Note that, following embodiments are essentially preferable examples, and the scope of the present invention, the application, or the use is not intended to be limited.

First Embodiment

Referring toFIG. 1, a microwave oven10that is one example of an electromagnetic wave heating system of the present invention, comprises a heat chamber2for storing an object therein, flat antennas1A to1C arranged respectively on left, right wall surfaces and bottom surface of the heat chamber2, a discharger3, an oscillator7configured to generate a microwave, a switcher4configured to switch a supply destination of microwave inputted from the oscillator7, a controller5configured to control the oscillator7and the switcher4, and a coaxial line6that connects the switcher4with the respective flat antennas1.

Referring toFIG. 2, regarding the respective flat antennas1, sixteen small sized antennas11A to11P are arranged by four column×four row in an array manner. Each small sized antenna11is arranged so as to become equal in distance from/to the switcher4.

Referring toFIG. 3, the flat antenna1is formed by a first substrate12on the front surface side and a second substrate13on the back surface side.

The first substrate12is a substrate made of, for example, ceramics with insulation characteristics, and sixteen metal patterns formed in spiral manner are formed on the surface thereof. Each metal pattern functions as a small size antenna11.

The second substrate13on the back surface includes a power feed point14formed at base configured to receive a microwave supply from the switcher4. Further, the metal pattern for delivering microwave starting from the power feed point14to respective small antennas11is formed on the surface.

Each small sized antenna11is formed spirally at the center of a power receiving end11ainputted of the microwave, and formed such that a distance from the power receiving end11ato an opening end11bbecomes approximately ¼ wavelength of microwave. Moreover, a through hole is formed at the position of the power receiving end11aof each small sized antenna11of the first substrate12. A via is filled with in the through hole, and the metal pattern of the first substrate12is connected to the metal pattern of the second substrate13through the via.

Arrangement is performed such that the distance from the power feed point14to each power receiving end11aof the corresponding antenna11in total number of sixteen, becomes equal. Accordingly, the sixteen antennas simultaneously becomes “ON” or “OFF” based on an output pattern from the oscillator3in principle since microwave in same phase is supplied into each of the sixteen antennas.

Referring toFIG. 4, the structure of a discharger3is explained in details. The discharger3comprises an input part3aconfigured to receive microwave from the coaxial line6, a coupling part3bconfigured to attain an impedance matching between the coaxial line and the discharger3, and a resonation part3cconfigured to resonate microwave by a microwave resonation structure. A discharge electrode36is arranged at the distal end of the resonation part3c.A conductive characteristic casing31thereinside stores respective members.

Microwave inputted from an input terminal32of the input part3ais transmitted into the coupling part3bby a first center electrode33. A dielectric material39asuch as ceramics is provided between the first center electrode33and the casing31.

The coupling part3bis a part that attains an impedance matching between the coaxial line (for example, having 50Ω impedance) and the resonation part3c(about 10Ω for example at microwave frequency band). A second center electrode34is formed in cylindrical manner provided with a bottom part at the resonation/discharge part3cside, and the cylindrical part surrounds the first center electrode33. The stick type first center electrode33opposes to the inner wall of the cylindrical second center electrode34, and the microwave from the first center electrode33is transmitted to the second center electrode34by capacitively-coupling at the opposing part. The dielectric material39bmade of ceramics and etc. is filled with at the cylindrical part of the second center electrode34, and the dielectric material39cmade of ceramics is also provided between the second center electrode34and the casing31. A desired impedance matching can be attained by designing suitably length of these members and distance between members.

A third center electrode35of the resonation/discharge part3cis connected to the second center electrode34, and the microwave of the second center electrode34is transmitted into the third center electrode35. The length of the third center electrode35is set to be approximately ¼ wavelength of microwave substantially. If it is designed such that a node of microwave is set at a position between the third center electrode35and the second center electrode34, an anti-node of microwave becomes positioned at the distal end of the third center electrode35, specifically at the discharge electrode36, and as the result, the potential becomes largest. The dielectric material39d,ceramics, is partially filled with between the third center electrode35and the casing31. Here, it is better to fill ceramics with from the viewpoint of mechanical strength securing for the discharger3; however, if the potential, so called Q factor of the discharger3is aimed to be enhanced, it is better not to fill ceramics with. Accordingly, these “trade-off” are taken into account, and the ceramics is partially filled with at the discharger3.

According to the discharger3, when the microwave lkW is supplied from the input part3a,some tons KV of high voltage occurs between the discharge electrode36and the casing31, and the discharge is caused between the discharge electrode36and the casing31. Since the discharge plasma can be generated by the discharge, food heat cooking by the low temperature plasma can be achieved by utilizing the discharger3to the microwave oven10.

Note that, the discharger3uses a microwave resonation structure, and therefore, discharging in series can be performed. Since the discharger3differs in this point from many types of dischargers such as spark plug that has no choice but to perform intermittent discharge, it can be said that the discharger3is suitable for the heat cooker such as microwave oven.

Moreover, the discharger3causes high voltage by using microwave generated in the oscillator7. The oscillator7also functions as a power source of microwave irradiated from the flat antenna1. Accordingly, both low temperature plasma generation and microwave heating can be achieved only by one oscillator7.

Second Embodiment

In replace of the above discharger3, an injector/discharger40illustrated inFIG. 5can also be used. The injector/discharger40comprises an injection pipe42, an annular protrusion41provided at the tip end of the injection pipe42, and a cylindrical member43that surrounds the injection pipe42. The injection pipe42injects the water vapor from an injection port42aprovided at the tip part. The microwave resonation structure is formed at an outside of the injection pipe42, and as well as the discharger3, the microwave from the oscillator7is boosted. A microwave resonation circuit formed on the surface of the injection pipe42is designed so as to be the wavelength becomes ¼ wavelength of microwave in length and such that the anti-node of microwave is positioned at a part provided with the annular protrusion41. Then, when microwave with a predetermined power or above is fed from the oscillator7to the injector/discharger40, the potential difference between the annular protrusion41and the cylindrical member43is increased, and the breakdown (discharge) occurs there.

By using together the injector/discharger40and the above flat antenna1, the below cooking way is considered. Firstly, the temperatures of food and the heat chamber on which the food is put, are warmed up by microwave heating. Under th situation, heating suitable for eggs and dairy products that requires, for example, a delicate heat control can be performed by injecting the water vapor from the injection pipe42and further generating the discharge plasma.

INDUSTRIAL APPLICABILITY

As explained as above, the present invention is effective to an electromagnetic wave heating system such as a microwave oven.