JPS6332235B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high-frequency heating device that performs dielectric heating in a cavity resonator using high-frequency electromagnetic waves.

Conventional methods for uniformly heating the heated object in a cavity resonator of high-frequency electromagnetic waves, that is, inside the heating chamber, include the stirrer method, which stirs the high-frequency electromagnetic waves, the turntable method, in which the heated object is placed on a rotary table and rotated, and the high-frequency electromagnetic wave method. There is a rotating antenna method that rotates a radiator, that is, a rotating antenna. Among these, the rotating antenna method occupies the least space in the heating chamber, so the effective heating chamber size is large, so it is often used especially in compact home microwave ovens. However, the rotary antenna method is much heavier in size and shape than other methods, and there are many patents related to the rotary antenna. However, if the dimensions of the heating chamber change or the position of the rotation axis of the rotary antenna changes, the shape and dimensions of the rotary antenna will change significantly, so not only the shape but also the dimensions are very important factors. Even with the same shape, if the dimensions change by a quarter of the oscillation wavelength of the high-frequency electromagnetic waves, the heating distribution in the heating chamber as well as the output of the high-frequency oscillator have the disadvantage that the characteristics change to the extent that they are completely reversed.

In the rotating antenna system, the present invention does not radiate radio waves from the antenna corresponding to the rotation axis, and propagates the radio waves to the tip of the rotating antenna without radiating them into the heating chamber, and radiates a vertical electric field only from the tip of the antenna. The purpose is to make the electric field distribution within the heating chamber uniform.

An embodiment of the present invention will be described below based on the drawings.

In FIG. 1, a household microwave oven with a heater plate is shown. Two heater plates 2 are provided on the upper part of the main body 1, and can be used for boiling food.
Two control knobs A3 on the main body 1 control and adjust the power of the heater plate 2, respectively. Also heating chamber 4
Heater heating and high-frequency heating inside are adjusted using a control knob B5. A front opening of the heating chamber 4 is provided with a door 6 for taking food in and out.

In FIG. 2, a heater plate 2 made of a heat-resistant dielectric material is provided on the upper part of the main body 1, and cooking can be performed using a plate heater 7. Heating chamber 4
Oven heaters 8 and 9 are installed on the top and bottom of the
is installed, allowing indoor oven heating or additional heating for browning. A heat-resistant heat insulating material 11 is provided around the outside of the wall surface 10 of the heating chamber 4 to prevent heat radiation to the outside.

On the other hand, high-frequency electromagnetic waves from the magnetron 12 are transmitted through a tapered waveguide 13 to the motor 1.
The rotational force of the heating chamber 4 is transmitted by the belt 15 and is fed into the heating chamber 4 by the rotating rotary antenna 16 .

In FIG. 3, high-frequency electromagnetic waves are radiated from the rotating antenna 16 rotating inside the heating chamber 4. Depending on the dimensions of the heating chamber 4, the dimension l of the rotating antenna 16 on the heating chamber 4 side, which corresponds to the rotation axis. If ₁ is too long, electromagnetic waves will be radiated from this rotating antenna 16, and the electromagnetic waves will not propagate to the tip of the rotating antenna 16. Furthermore, if the propagation impedance of the antennas A17 and B18 perpendicular to the rotating antenna 16 is high, they will radiate into the heating chamber 14, and the radio waves will not propagate to the tip of the antenna A17. Therefore, in order to lower the propagation impedance, the width dimensions of antenna A17 and antenna B18 are made larger than the distance between the heating chamber 4 wall and antenna A17 and antenna B18, that is, the dimension l ₁ , thereby lowering the propagation impedance of radio waves and heating No radiation is emitted into room 4. However, a small amount of radio waves are radiated into the heating chamber 4. This is because the electric fields E ₁ 19 and E ₂ 20 of the antenna A 17 and the antenna B 18 are oriented in opposite directions, so they cancel each other out and do not substantially propagate into the heating chamber 4 . Note that the distance between the heating chamber 4 wall and antenna A17 and antenna B18, that is,
The shorter l ₁ is, the less radio waves will reach the rotating shaft.
The number of radio waves radiated vertically downward from the rotation axis decreases, but if l ₁ is one-eighth wavelength or less, the number of radio waves radiated is small and does not affect heating.

Then, the inside of the heating chamber 4 is excited only by the difference in length between the antenna A17 and the antenna B18. Therefore, by making the difference in length between antenna A17 and antenna B18 approximately one-fourth of the high-frequency electromagnetic wave, an electric field in the opposite direction will not occur in the part with the difference in length, so that radio waves can be radiated from the tip of the antenna most efficiently. be done. Further, since the antenna A17 is bent at a substantially right angle, radio waves are radiated into the heating chamber 4 by the vertical electric field E ₃ 21. When the heating chamber 4 is excited by the vertical electric field E ₃ 21, an electric field perpendicular to the heating chamber 4 is excited. This vertical electric field is not easily affected by loads that mainly have a plane perpendicular to the direction of the electric field (such as food), that is, flat loads, so loads of various shapes can be heated with flat loads. However, everything is heated evenly. However, for loads placed in containers such as pots (loads that mainly have a length in the same direction as the vertical electric field), the vertical electric field is affected, but the need for uniform heating is greater than that of the former load. It seems that there are not many.

FIG. 4 shows another embodiment of the invention.

In FIG. 4, if there is a metal bulge 23 for attaching the sealing plate 22 in the heating chamber 4, a screw 24 for attaching the waveguide 20 and the heating chamber 4, etc., the wall of the heating chamber 4 is substantially Since the antennas bulge downward, the antennas A17 and B18 are bent appropriately in order to improve the propagation of radio waves from the antennas A17 and B18, that is, to keep the distance _l1 constant.

As described above, the present invention provides the following effects.

(1) Since the radio waves propagate to the tip of the antenna without reflection, the distribution performance when rotating is significantly improved.

(2) Since the distribution is made uniform only by a rotating vertical electric field, the uniformity of the distribution does not change much with changes in load.

(3) Since the horizontal electric fields cancel each other out, there is almost no horizontal electric field that adversely affects the distribution.

(4) There is little change in the characteristic impedance (propagation impedance) of the rotating antenna part, that is, the coupling part between the waveguide and the heating chamber, and the characteristic impedance (propagation impedance) of the horizontal antenna.
There is little reflection of radio waves between these areas.

(5) Since antennas A and B can be constructed from simple flat plates, they can be constructed easily and inexpensively.

(6) Since there is no radio wave radiation compared to a rotating antenna that corresponds to the rotation axis, the rotation effect of a rotating antenna is very large.

[Brief explanation of the drawing]

FIG. 1 is an external perspective view of a high-frequency heating device that is an embodiment of the present invention, and FIG. 2 is a side sectional view of the same device.
3 is an enlarged sectional view of the main part of FIG. 2, and FIG. 4 is an enlarged sectional view of the main part of another embodiment of the present invention. 4... Heating chamber, 12... High frequency oscillator, 13... Waveguide, 16... Rotating antenna, 17... Antenna A, 1
8...Antenna B.

Claims (1)

[Claims] 1. A heating chamber that stores an object to be heated, a high-frequency oscillator that oscillates high-frequency electromagnetic waves in the heating chamber, a waveguide that propagates the high-frequency electromagnetic waves of the high-frequency oscillator, and a rotating device that communicates the waveguide and the heating chamber. a freely rotating antenna; on the side of the heating chamber of the rotating antenna, an antenna A and an antenna B extending in a direction substantially perpendicular to the rotation axis and on both sides of the rotation axis; antenna A
The difference in length between antenna A and antenna B is approximately one-fourth of the high-frequency electromagnetic wave, the tip of antenna A is bent at a substantially right angle to a length within one-quarter wavelength, and the width of antenna A and antenna B is The high frequency heating device has dimensions larger than the distance between the heating chamber wall and the antenna A and the antenna B.