JP2002246167A - High-frequency heating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-frequency heating device for heating an object to be heated, such as foods, by utilizing microwaves, which are capable of heating the object uniformly and efficiently. SOLUTION: A means for generating microwaves is provided with a microwave transmitter 1 for varying a frequency, an amplifier 2 for amplifying signals of the transmitter 1, and a state-detecting means 5 for detecting the heating condition of the object to be heated. The state-detecting means 5 detects the condition of the object to be heated, and the frequency of the microwave transmitter 1 is adjusted by the microwave transmitter 1, so that the microwave distribution can be varied within an accommodating chamber 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency heating apparatus for heating food or the like using microwaves, and more particularly to a microwave oven for home use.

[0002]

2. Description of the Related Art As shown in FIG. 4, a conventional high-frequency heating apparatus uses a magnetron as microwave generating means and is driven by an inverter.

The inverter includes a rectifier circuit for rectifying commercial power, a filter circuit for reducing noise, and a
It is composed of a high-frequency switching circuit operating at kHz, a resonance / boosting circuit for reducing the switching loss of the switching device and boosting the voltage, and a rectifying circuit for rectifying the boosted high-voltage AC voltage.

In order to operate the magnetron, it is necessary to apply a high DC voltage between the anode and the cathode of the magnetron. For this reason, the inverter supplies a DC voltage of about -4 kV to the magnetron. As a result, the magnetron oscillates at a frequency of 2.45 GHz. This frequency is determined by the structure of the magnetron and can only be transmitted at a single frequency.

[0005] A magnetron can only oscillate at a single frequency, but its spectrum has a certain width. 5 is a characteristic diagram showing the spectrum of the output of the magnetron, the horizontal axis represents the frequency, the vertical axis represents the intensity of the spectrum. This spectrum has a width of about 40 MHz centered at 2450 MHz.

[0006] This spectrum is not fixed, and varies depending on the electrical matching between the object to be heated and the magnetron. Further, a magnet is used in the magnetron, and the spectrum changes during operation due to the temperature characteristics of the magnet.

[0007]

However, in the above-described conventional high-frequency heating apparatus, since the magnetron is used, the operating frequency cannot be fixed due to the state of electrical matching with the object to be heated and the temperature characteristics. , It is not possible to specify the microwave distribution in the storage that stores the object to be heated,
There is a problem that the object to be heated cannot be sufficiently heated uniformly.

[0008]

In order to solve the above-mentioned problems, the present invention provides a method for generating a microwave by using an electric matching state between a microwave generating means and an object to be heated or a temperature characteristic of the microwave generating means. The configuration is such that the frequency does not change, and the frequency of the microwave can be arbitrarily adjusted.

According to the above invention, since the frequency can be arbitrarily determined, the microwave distribution in the storage can be freely controlled, and uniform heating or efficient heating of the object to be heated can be achieved. A child can be realized.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A high-frequency heating apparatus according to a first aspect of the present invention has a microwave transmitter capable of changing a frequency in a means for generating a microwave, and an amplifier for amplifying a signal from the transmitter.

Then, by adjusting the frequency of the microwave transmitter, the microwave distribution in the storage can be freely changed.

According to a second aspect of the present invention, there is provided a high-frequency heating apparatus comprising: a microwave generator capable of changing a frequency in a means for generating a microwave; an amplifier for amplifying a signal from the transmitter;
State detecting means for detecting a heating state of the object to be heated.

[0013] The state detecting means detects the heating state of the object to be heated, and adjusts the frequency of the microwave transmitter based on the information, whereby the microwave distribution in the storage can be changed.

According to a third aspect of the present invention, there is provided a high-frequency heating apparatus having state detecting means for detecting a temperature of an object to be heated.

[0015] Since the frequency of the microwave transmitter is set by the information of the state detecting means for detecting the temperature, the microwave distribution in the storage can be made an appropriate distribution suitable for uniform heating.

A high-frequency heating apparatus according to a fourth aspect of the present invention has a state detecting means for detecting the temperature of the amplifier.

[0017] Since the frequency of the microwave transmitter is set by the information of the state detecting means for detecting the temperature, the microwave distribution in the storage can be made a distribution suitable for efficient heating.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a block diagram of a high-frequency heating apparatus according to Embodiment 1 of the present invention. 1 is a transmitter, 2 is an amplifier, 3 is a waveguide means, and 4 is a storage. The transmitter is a microwave oven, the frequency of which is allowed to use 2.4G
A signal of 2.5 GHz is generated from Hz. Amplifier 2
Amplifies the signal of the transmitter 1 by receiving power supply from a power supply, and uses a class A, class B, or class C amplifier circuit using a semiconductor element. Since microwaves are used for heating purposes, waveform distortion is not a problem, and it is advantageous to use particularly efficient class C amplification. Semiconductor devices include FETs using gallium arsenide and HEMTs using SiC, which is attracting attention as a new semiconductor material. As described above, by using the microwave generating means using the semiconductor element, the oscillation frequency does not change due to the temperature characteristic unlike the magnetron.

The high-power microwave amplified by the amplifier 2 is guided to the storage 4 by the waveguide means 3. A waveguide or a coaxial cable can be used for the waveguide unit 3. The microwave guided to the storage 4 by the waveguide unit 3 is applied to an object to be heated in the storage 4.

The electrical matching between the amplifier 3 and the object to be heated is affected by the impedance of the waveguide means 3, the dielectric constant of the object to be heated, the impedance determined by the shape, the impedance of the housing 4, and the like. Since the microwave frequency is determined by the transmitter 1, the microwave of a specific frequency can be output without being affected by the matching between the amplifier 3 and the object to be heated.

An infrared sensor is mounted in the storage 4 as the state detecting means 5. This infrared sensor is composed of a plurality of infrared detecting elements, and the temperature distribution is clarified by detecting the temperature of the place where the object to be heated in the storage 4 is placed in a matrix. This state detecting means 5
, The signal frequency of the transmitter 1 is determined. That is, based on the detected temperature distribution information, the frequency of the transmitter 1 is adjusted so that a high temperature portion is irradiated with a weak microwave and a low temperature portion is irradiated with a strong microwave. I do.

FIG. 2 is a microwave distribution diagram showing the result of simulating the distribution of microwaves in the storage box 4, which is indicated by an isoelectric field curve connecting points of the isoelectric field. (A) to (e) of the drawing are the results of a simulation in which the frequency of the microwave is changed, and it can be seen that the distribution of the microwave changes depending on the frequency. Therefore, the microwave distribution desired by the information of the state detection means 5 is obtained,
By setting the frequency appropriately, uniform heating of the object to be heated can be realized.

(Embodiment 2) FIG. 3 is a block diagram of a high-frequency heating apparatus according to Embodiment 2 of the present invention.

The present embodiment is different from the first embodiment in that the state detecting means 6 comprises a temperature detecting element for detecting the temperature of the semiconductor element constituting the amplifier 2.

The components having the same reference numerals as in the first embodiment have the same structure, and a description thereof will be omitted.

Next, the operation and operation will be described. As described above, the electrical matching between the amplifier 2 and the object to be heated is determined by the impedance of the waveguide means 3, the dielectric constant and the shape of the object to be heated. The impedance is determined by the impedance, the impedance of the storage case 4, and the like. However, when the matching is not achieved, the loss of the semiconductor element increases, and the temperature thereof significantly increases. If the matching is not achieved, the energy of the microwave absorbed by the object to be heated is small, so that efficient heating is not performed. Therefore, the temperature of the semiconductor element is detected, and the signal frequency of the transmitter 1 is changed based on this information.
If the frequency of the microwave changes, the impedance changes, so that the electrical matching state between the amplifier 2 and the object to be heated can be changed. Therefore, by setting the frequency such that the temperature of the semiconductor element is minimized, the most suitable electrical matching between the amplifier 2 and the object to be heated can be achieved. Thereby, the most efficient heating can be performed.

[0028]

As described above, according to the high-frequency heating apparatus of the present invention, the means for generating microwaves has a microwave transmitter whose frequency can be varied, and an amplifier for amplifying the signal of the transmitter. Therefore, there is an effect that the microwave distribution in the storage can be freely changed by adjusting the frequency of the microwave transmitter.

[Brief description of the drawings]

FIG. 1 is a block diagram of a high-frequency heating device according to a first embodiment of the present invention.

FIG. 2 is a microwave distribution diagram in a storage of the high-frequency heating device.

FIG. 3 is a block diagram of a high-frequency heating device according to a second embodiment of the present invention.

FIG. 4 is a circuit block diagram of a conventional high-frequency heating device.

FIG. 5 is a characteristic diagram showing a spectrum of a magnetron used in a conventional high-frequency heating device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 transmitter 2 amplifier 3 waveguide means 4 storage 5, 6 state detection means

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) H05B 6/64 H05B 6/64 G 6/66 6/66 C (72) Inventor Yuji Nakabayashi Yuji Kadoma, Kadoma City, Osaka 1006 Matsushita Electric Industrial Co., Ltd. BB01 EB13 EB14 3L086 CB01 CB05 CB16 CC08 DA05 DA12

Claims (4)

[Claims] A transmitter having a variable oscillation frequency; an amplifier for amplifying a signal from the transmitter; a storage for storing an object to be heated by microwaves generated by the amplifier; And a waveguide means for guiding the output of (1) to the storage housing the object to be heated. 2. The high-frequency heating apparatus according to claim 1, wherein a frequency of the transmitter is set according to a state of the object to be heated detected by a state detecting means for detecting a heating state of the object to be heated. 3. The high-frequency heating apparatus according to claim 2, wherein the state detecting means detects a temperature of the object to be heated. 4. The high-frequency heating apparatus according to claim 2, wherein the state detecting means detects the temperature of the amplifier.