JPH0574561A - High frequency heating device - Google Patents

Abstract

(57) [Summary] [Object] The present invention aims to uniformly heat an object to be heated by allowing high-frequency energy to be introduced into the heating chamber even if the height of the heating chamber is reduced to 120 mm or less. To do. [Structure] The heating chamber 1 is formed in a cubic shape with a height of 120 mm or less, and a microwave frequency generated by the high frequency generator 7 is set to 5.8 GHz.

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 device for cooking an object to be heated by dielectric heating.

[0002]

2. Description of the Related Art A high-frequency heating device has evolved from a single-function type in which only dielectric heating by microwaves is used to a multi-function type in which an electric heating device is built in. Fine cooking is becoming possible. FIG. 3 shows a conventional multi-functional high-frequency heating device. In the figure, AC power from a commercial AC power supply is converted by a power supply circuit 3 into power necessary for driving a magnetron 2 which is a high frequency generator. Microwaves generated from the magnetron 2 are radiated into the heating chamber 10 through the waveguide 4 and dielectrically heat the object 8 to be heated on the turntable 5 rotating at a low speed. 6
Is a heater for electric heating used for fish cooking.

In the conventional high-frequency heating apparatus, the multi-function cooking is realized under such a structure, but it has been desired to make the heating chamber 10 thinner for the following reasons. That is, the shape of the heating chamber 10 is large relative to the size of the object to be heated 8 and the heat loss of the heating chamber 10 itself cannot be ignored, and when radiant heating is performed by the heater 6 for electric heating, the heater 6 is not heated. The distance to the object 8 is large, and the heating efficiency of the heater 6 is poor. In addition to this, in consideration of future in-vehicle mounting of a high-frequency heating device, the heating chamber 10 needs to be thinner. On the other hand, as to whether the height of the conventional heating chamber 10 should be simply lowered, the following problems arise in terms of microwave heating.

A high-frequency heating device widely used for consumer use has a microwave frequency of I.S. S. M. 2.45G which is one of the frequency bands (for industrial, scientific and medical use)
Hz is used. By the way, the heating chamber 10 is considered as a rectangular parallelepiped resonator, and is heated at a resonance frequency determined by the resonator shape as shown in the following equation.

F (Hz) = [1/2 (ε · μ) ^1/2 ] · [(m / W) ² + (n / D) ² + (p / H) ² ] ^1/2 where: W, D, and H are the width, depth, and height (unit: mm) of the heating chamber 10, and ε and μ are the dielectric constants of the medium in the heating chamber 10,
Permeability. m, n, and p are the numbers of changes in the electromagnetic field in each direction, and indicate the order of the resonance mode (zero or a positive integer).

As an example of a conventional high-frequency heating apparatus, consider a heating chamber size of W = 285 mm, D = 284 mm, H = 193 mm. Considering that the rotation of the turntable 5 changes the impedance of the heating chamber 10 and the oscillation frequency of the magnetron 2 also changes within ± 20 MHz from the center frequency, in this case, 2.45 GHz.
The resonance frequency and the resonance mode within ± 20 MHz centering around are as shown in FIG. The numbers in parentheses in the figure indicate the order of the resonance mode. On the other hand, when the height is lowered, the number of resonance modes in proximity to each other is reduced, or the resonance modes do not exist. FIG. 5 shows the resonance frequency and the resonance mode when H = 81 mm, but there is only one resonance mode within ± 20 MHz.

It is better that there are a large number of resonance modes even with the same fluctuating frequency width. That is, since any one of the plurality of modes is in resonance or in a state close to resonance, high-frequency energy is easily guided to the heating chamber 10 even if the oscillation frequency changes. Moreover, since the number of changes m, n, p of the electromagnetic field differs for each resonance mode, the distribution of the electromagnetic field in the heating chamber 10 constantly changes, which is effective for uniform heating. Generally, it is considered preferable that there are three or more modes near the center frequency and on the low frequency side and the high frequency side.

In the heating chamber 10 of H = 81 mm, there is only one resonance mode in the 2.45 GHz band as shown in FIG. 5, and when the oscillation frequency of the magnetron 2 is far from the resonance frequency, high frequency energy is generated in the heating chamber 10. It becomes difficult to enter. Moreover, since the electromagnetic field distribution is fixed, uniform heating is difficult. Dimension example of the above width and depth W = 285mm, D =
In the case of 284 mm, there is no resonance mode below H = 62 mm. Further, when H = 62 mm or more and 120 mm or less, the number of resonance modes is 2.45 GHz ± 20 MHz, and there are only two resonance modes at maximum, which is insufficient in terms of uniform heating.

[0009]

In the conventional high-frequency heating device, since the heating chamber is made thin, if the height is set to 120 mm or less, uniform heating is difficult at a microwave frequency of 2.45 GHz and heating unevenness is large. Become. The height is 62
If the thickness is reduced to less than mm, there is a problem that high frequency energy cannot enter the heating chamber.

Therefore, according to the present invention, the height of the heating chamber is set to 120.
An object of the present invention is to provide a high-frequency heating device that can guide high-frequency energy into the heating chamber even if it is thinned to less than mm, and can uniformly heat an object to be heated.

[0011]

In order to solve the above problems, the present invention is a high frequency heating apparatus for heating an object to be heated housed in a heating chamber with microwaves generated by a high frequency generating apparatus. The gist is that the chamber is formed in a rectangular parallelepiped shape having a height of 120 mm or less, and the frequency of the microwave generated by the high frequency generator is set to 5.8 GHz.

[0012]

In the case of a thin rectangular parallelepiped heating chamber with a height of 120 mm or less, the resonance mode determined by the dimensions of the heating chamber is 2.45G.
There are more 5.8 GHz than Hz. Therefore, even if the oscillation frequency of the high frequency generator changes due to the impedance change of the heating chamber, the high frequency energy is easily guided to the heating chamber, and the object to be heated can be uniformly heated.

[0013]

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

It is to be noted that, in FIG. 1, the same or equivalent parts as the devices and members in FIG. 3 are designated by the same reference numerals as those described above, and the duplicated description will be omitted.

In this embodiment, the heating chamber 1 has the same width and depth as the conventional one, W = 285 mm and D = 284 mm, but has a height H = 81 mm and is formed in a thin rectangular parallelepiped shape. The oscillation frequency of the magnetron 7, which is a high frequency generator, is set to 5.8 GHz.

FIG. 2 shows the resonance frequency and the resonance mode for the shape of the heating chamber 1 as described above. For comparison, the frequency variation width of the magnetron 7 is set to ± 20 MHz as in the case of 2.45 GHz. Conventional 2.45
At GHz ± 20 MHz, there was only one resonance mode number as shown in FIG. 5, whereas at 5.8 GHz ±
It exists in good balance on the high frequency side. As a result, even if the oscillating frequency of the magnetron changes, it is not difficult for high-frequency energy to enter the heating chamber 1. Also,
As can be seen from comparison with FIG. 5, since the order of each resonance mode is high, that is, the number of changes in the electromagnetic field in one direction is large,
More uniform heating can be expected than 2.45 GHz ± 20 MHZ. At 5.8 GHz ± 20 MHz, heating chamber 1
Since there are three or more modes up to H = 26 mm, it is not necessary to limit the height to 81 mm as in this embodiment.

[0017]

As described above, according to the present invention,
The frequency of the microwave generated by the high frequency generator is set to 5.
Since it is set to 8 GHz, even if the height of the heating chamber is reduced to 120 mm or less, the number of resonance modes in the heating chamber increases and high-frequency energy can be introduced into the heating chamber, and the object to be heated is uniformly heated. You can

[Brief description of drawings]

FIG. 1 is a perspective view showing a configuration of an embodiment of a high-frequency heating device according to the present invention.

FIG. 2 is 5.8 GHz determined from the shape of the heating chamber of this embodiment.
It is a figure which shows the resonance frequency and resonance mode of a band.

FIG. 3 is a perspective view showing a configuration of a conventional high-frequency heating device.

FIG. 4 is 2.45 GHz determined from the shape of the heating chamber of the conventional example.
It is a figure which shows the resonance frequency and resonance mode of a band.

FIG. 5 is a diagram showing a resonance frequency and a resonance mode in a 2.45 GHz band determined by the shape of the heating chamber when the heating chamber is made thin.

[Explanation of symbols]

 1 Heating chamber 7 Magnetron (high frequency generator) 8 Object to be heated

Claims (1)

[Claims] 1. A high-frequency heating device for heating an object to be heated housed in a heating chamber with microwaves generated by a high-frequency generator, wherein the heating chamber is formed in a rectangular parallelepiped shape having a height of 120 mm or less,
The high frequency heating device is characterized in that the frequency of the microwave generated by the high frequency generator is set to 5.8 GHz.