JPS6258597A - High frequency heater - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an improvement in heating unevenness reducing means for a high frequency heating device.

2. Prior Art Japanese Patent Publication No. 7583/1983 proposes to provide a magnetron approximately at the center of the upper surface of the heating chamber, and to provide a stirrer blade directly below the output antenna of the magnetron. In this conventional example, unless there is a sufficient distance between the stirrer blade and the output antenna tip, sparks may occur near the output antenna tip and damage the magnetron.

However, recently, the need for lighter, thinner, shorter and smaller devices has become stronger, and it has become necessary to provide a high-frequency heating device that reduces idle space and has a compact external dimension. Since it is necessary to take a sufficient amount of space and widen the idle space between the stirrer blades and the top surface of the heating chamber,
It has become impossible to meet the above needs.

Problems to be Solved by the Invention When attempting to reduce the idle space between the top surface of the heating chamber and the stirrer blades, sparks occur between the two star blades and the tip of the output antenna of the magnetron.

There is a risk of damage to the magnetron.

Means to solve the problem: Install it opposite to the output antenna of the magnetron, □
The long side is larger than 1/2 of the wavelength used, approximately at the center.

A rotating antenna made of a flat metal plate having a substantially rectangular radiation opening whose short side is larger than 1/4 of the wavelength used is provided, and a cutout is provided around the antenna.

Effect By configuring as described above, no spark will be generated even if the output antenna tip is brought close to the rotating antenna or even if the output antenna tip penetrates the radiation port of the full rotation antenna, so the contact between the two rotation antenna and the top surface of the heating chamber will be reduced. Idle space can be reduced.

Embodiment The structure and operation of a high-frequency heating device according to an embodiment of the present invention will be explained with reference to all the drawings.

In Fig. 3, 1 is a heating chamber that stores the object to be heated, 2 is a magnetron that generates high frequency energy, and heating chamber 1
It is attached directly to the top surface 6 of the. B is the output antenna of magnetron 2.

Reference numeral 4 denotes a rotating antenna that combines with the electromagnetic field radiated from the output antenna 3 and re-radiates it, and is located approximately in the upper center of the heating chamber 1. A vane 5 is made of a dielectric material that transmits high frequencies. An antenna cover 7 supports and covers the rotating antenna 4, and is made of a dielectric material that is transparent to high frequencies. 8
is an air outlet consisting of a large number of small holes, and is provided to introduce air from an air blower fan 9 for cooling the magnetron 2 into the heating chamber 1. 10 is a motor for fully rotating the blower fan 9. Reference numeral 11 indicates the air from the blower fan 9 to the heating chamber 1.
It is a wind control plate that makes it easier to get inside. 12 is the rear of the outer box, 1
This is the top of the outer box. 14 is a front flange of the heating chamber 1, 15 is an operation panel attached to this front flange, 16
is a door provided at the entrance of the heating chamber 1 so as to be openable and closable.

FIG. 1 is an enlarged view showing the mounting structure of the rotary antenna 4 in FIG. 3. A fixed shaft 17 provided on the antenna cover 7 rotatably supports a rotary shaft 18 of the rotary antenna 4.

The rotating shaft 18 is formed of a dielectric material that transmits high frequency waves, and a part of the rotating shaft 18 extends to form a cylindrical portion 19 that surrounds the tip of the output antenna 3. A cylindrical portion 19 is formed on the outer periphery of the cylindrical portion 19 and is integrated with the blade 5. The horizontal plate 24 is fixed. The rotating antenna 4 is attached to the horizontal plate 24 by protrusions 2° at several locations. The rotating shaft 18 and the cylindrical portion 19 are integrally formed through a connecting surface 21 facing the tip of the output antenna.

At the joint portion between the cylindrical portion 19 and the horizontal plate 24, a protruding portion 22 is provided on the cylindrical portion 19 side, and a rising portion 23 is provided on the horizontal plate 24 side. The protruding portion 22 is used to position the horizontal plate 24 when the horizontal plate 24 is fully press-fitted into the cylindrical portion 19, and the rising portion 2 is such that the horizontal plate 24 and the cylindrical portion 19 are at right angles to each other. The aim is to minimize the entire slope of 24. Reference numeral 25 denotes a low-friction coating made of fluororesin or the like, which is added to reduce friction between the tip of the rotating shaft 18 and the antenna cover 7.

Figure 2 shows the ratio-rotating antenna 4 seen from the direction of the AB arrow in Figure 1.
This shows the positional relationship between the output antenna 3 and the output antenna 3. In FIG. 2, only those made of metal are shown. The rotating antenna 4 is composed of a metal flat plate having a substantially rectangular radiation hole 26 in the center. Long side 2 of radiation port 26
The dimension X of 7 is larger than 1/2 of the wavelength used by the magnetron 2, and the dimension y of the short side 28 is larger than 1/4 of the wavelength used. That is, the radiation aperture 26 has a size comparable to the cross section of a waveguide that transmits the TE10 mode electromagnetic field. An output antenna 3 is located approximately in the center of the radiation port 26, and a rotary antenna 4 rotates around the entire output antenna 3.

Numeral 29 is a small hole into which the protruding piece 20 is inserted, and is used to connect the horizontal plate 24, which is integrated with the two blades 5, and the rotating antenna 4. Reference numeral 30 denotes a notch provided around the rotating antenna 4, which increases the change in impedance of the heating chamber 1 as seen from the magnetron 2.

Next, the effects of the embodiment configured as described above will be explained. A part of the high-frequency energy radiated from the output antenna 3 of the magnetron 2 is radiated downward from the antenna cover 7 from the radiation port 26 at the center of the one-rotation antenna 4, and the rest is radiated from the rotary antenna 4 and the upper surface 6 of the heating chamber 1. After passing between the two, it is radiated from around the rotating antenna 4 to below the antenna cover 7. In other words, the high frequency energy radiated from the output antenna 6 is radiated from the center and periphery of the rotating antenna 4, so the positional relationship between the tip of the output antenna B and the radiation port 26 is determined by the external dimensions of the rotating antenna 4 and the radiation port 2.
By relatively adjusting the dimensions of the heating chamber 1, the object to be heated placed in the heating chamber 1 can be heated from the periphery and center of the object and can be heated uniformly. Furthermore, the rotating antenna 4.

Since the blades 5 are rotated by applying air from the cooling fan 9 to the blades 5, the direction of the electric field radiated from the radiation port 26 changes from time to time, allowing more uniform heating.

The sizes of the long side 27 and short side 28 of the radiation port 6 are selected in the same way as the cross-sectional dimensions that allow transmission of the fundamental mode TE10 of a waveguide normally used for high power, so that the output antenna 3 can transmit radiation 06. Even if the output antenna 3 and the rotary antenna 4 are brought close to each other by penetrating through the heating chamber 1, the heating chamber 1 is in a raw firing state without the object to be heated inside.

It has been experimentally confirmed that no spark is generated between the output antenna 4 and the rotating antenna 4.

Furthermore, the notch 30 increases the temporal change in specific impedance seen from the magnetron 2.

Abnormal heating of the anode of the magnetron 2 can be prevented, and uneven heating can also be reduced.

Effects of the Invention As described above, according to the present invention, a waveguide is installed opposite to the output antenna of a magnetron, is approximately centered on the output antenna, and has a cross-sectional size that allows transmission of the fundamental mode TE10 of a waveguide used for high power. Since a rotating antenna having a similar radiation opening is provided, no spark is generated even if the output antenna passes through the radiation opening. Therefore, the positional relationship between the output antenna and the rotary antenna can be freely selected, and the idle space between the two-rotation antenna and the upper surface of the heating chamber can be reduced.

The entire high frequency heating device can be made completely compact.

Furthermore, there is a circular cutout around the one-rotation antenna.
Prevents abnormal heating of the magnetron anode.

It can also reduce uneven heating.

[Brief explanation of the drawing]

FIG. 1 is an enlarged view of the main parts showing the structure of the installation of the rotating antenna 4 in the high-frequency heating device according to an embodiment of the present invention.
Figure 2 shows the output antenna 6 seen from the direction of arrow AB in Figure 1.
FIG. 3 is a schematic cross-sectional view of a main part of the high-frequency heating device of the present invention. 1... Heating chamber, 2... Magnetron. 3...Output antenna, 4...Rotating antenna. 6...Top surface, 26...Radiation port. 27...long side, 28...short side. 30...notch.

Claims (1)

[Claims] A magnetron (2) is directly attached to the top surface (6) of the heating chamber (1) that stores the object to be heated, and this magnetron (2)
The long side (27) is larger than 1/2 of the wavelength to be used, and the short side (27) is installed opposite to the output antenna (3) of
8) is a substantially rectangular radiation aperture (2
A high-frequency heating device characterized in that a rotary antenna (4) made of a flat metal plate having a diameter of 6) is provided, and a notch (30) is provided around the rotary antenna (4).