JPH0744065B2 - High frequency heating device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement in heating unevenness reducing means of a high-frequency heating device.

2. Description of the Related Art Japanese Patent Publication No. 52-7583 proposes that a magnetron is provided substantially in the center of the upper surface of a heating chamber, and a stirrer blade is provided just below the output antenna of the magnetron. In this conventional example, if the distance between the stirrer blade and the tip of the output antenna is not sufficient, a spark may be generated near the tip of the output antenna and the magnetron may be damaged. However, recently, the needs for light, thin, short, and small sizes have increased, and it has become necessary to provide a high-frequency heating device having a reduced outer space and a compact outer size.

In the conventional example, in order to prevent sparks, the distance between the stirrer blade and the tip of the output antenna must be sufficient, and the idle space between the stirrer blade and the upper surface of the heating chamber must be widened.
I have become unable to handle the above needs.

Problems to be Solved by the Invention If an attempt is made to reduce the idle space between the upper surface of the heating chamber and the stirrer blade, sparks may occur between the stirrer blade and the tip of the output antenna of the magnetron, which may damage the magnetron. It is a point.

Means for solving the problem A magnetron was directly attached to the upper surface of the heating chamber, and a flat plate-shaped rotating antenna integrally formed from a single metal flat plate so that the output antenna of this magnetron was approximately the center of the heating chamber was installed. It is installed in parallel with the upper surface, and its rotating antenna is
The long side is larger than 1/2 of the used wavelength, and the short side is 1/4 of the used wavelength.
A larger substantially rectangular radiation port is provided so that the output antenna is substantially at the center, and a notch is provided on the peripheral edge of the rotating antenna at a position symmetrical with respect to the output antenna.

With the above configuration, the space sandwiched by the rotating antenna and the upper surface of the heating chamber facing each other is formed as a line or radial line that radially transmits high-frequency energy about the output antenna of the magnetron as a center. At the same time, since the substantially rectangular radiation port of the rotating antenna corresponds to the TE ₁₀ mode of the waveguide, the reflection between the output antenna and the rotating antenna is reduced, and the standing wave is suppressed. Even if the distance between the antenna and the upper surface of the heating chamber is shortened to bring the output antenna and the metal edge of the inner periphery of the radiation hole of the rotating antenna closer to each other, or even if the tip of the output antenna is penetrated into the radiation hole of the rotating antenna, a spark is generated Without this, it becomes possible to radiate high-frequency energy not only from the radiation port of the rotating antenna but also from the outside.
At the same time, the distance between the rotary antenna and the upper surface of the heating chamber can be shortened, so that the idle space can be reduced.

EXAMPLE The configuration and operation of the high-frequency heating apparatus according to an example of the present invention will be described with reference to the drawings.

In FIG. 3, reference numeral 1 is a heating chamber for accommodating an object to be heated, and 2 is a magnetron for generating high frequency energy, which is directly attached to an upper surface 6 of the heating chamber. Reference numeral 3 is an output antenna of the magnetron 2. Reference numeral 4 denotes a rotary antenna which is coupled with an electromagnetic field radiated from the output antenna 3 and re-radiates, with the output antenna 3 of the magnetron 2 being substantially at the center and the heating chamber 1
And is substantially parallel to the upper surface 6 of the. Reference numeral 5 is a blade made of a high frequency transparent dielectric. Reference numeral 7 denotes an antenna cover for pointing and covering the rotary antenna 4, which is made of a high frequency transparent dielectric. Reference numeral 8 denotes a blower port formed of a large number of small holes, which is provided so that the wind from a blower fan 9 for cooling the magnetron 2 can be introduced into the heating chamber 1. Reference numeral 10 is a motor for rotating the blower fan 9. Reference numeral 11 denotes a wind control plate that makes it easier for the air from the blower fan 9 to enter the heating chamber 1.
12 is the rear surface of the outer box and 13 is the upper surface of the outer box. 14 is heating chamber 1
Is a front flange, 15 is an operation panel attached to the front flange, and 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 a mounting structure of the rotary antenna 4 of FIG. Fixed shaft 17 provided on this antenna cover 7
Supports the rotating shaft 18 of the rotating antenna 4 rotatably.
The rotary shaft 18 is made of a high frequency transparent dielectric,
A tubular portion 19 is formed by extending a part of 18 to surround the tip of the output antenna 3, and a horizontal plate 24 integrated with the blade 5 is fixed to the outer periphery of the tubular portion 19. The rotary antenna 4 is attached by several protruding pieces 20 provided on the horizontal plate 24. The rotating shaft 18 and the tubular portion 19 are integrally configured via a connecting surface 21 facing the tip of the output antenna 3. In the connecting portion of the tubular portion 19 and the horizontal plate 24, a protruding portion 22 is provided on the tubular portion 19 side, and a rising portion 23 is provided on the horizontal plate 24 side. The projecting portion 22 serves to position the horizontal plate 24 when the horizontal plate 24 is joined to the tubular portion 19 by press fitting, and the rising portion 23
The horizontal plate 24 and the tubular portion 19 form a right angle with each other, and the inclination of the horizontal plate 24 is minimized. 25 is the rotating shaft 18
This washer is made of a fluororesin and has a small amount of friction, which is attached to reduce the friction between the tip of the and the antenna cover 7.

FIG. 2 shows the positional relationship between the rotary antenna 4 and the output antenna 3 as seen from the direction of the arrow AB in FIG. In FIG. 2, only those made of metal are shown. The rotating antenna 4 is a flat plate-shaped antenna integrally formed from a single metal flat plate, and has a substantially rectangular radiation port 26 in the center.
Is equipped with. The dimension x of the long side 27 of the radiation port 26 is larger than 1/2 of the operating wavelength of the magnetron 2, and the dimension y of the short side 28 thereof is larger than 1/4 of the operating wavelength. That is, the radiation port 26 is about the size of the cross section of the waveguide that transmits the TE ₁₀ mode electromagnetic field. The output antenna 3 is located substantially in the center of the radiation port 26, and the rotating antenna 4 rotates around the output antenna 3. Reference numeral 29 is a small hole into which the protruding piece 20 is inserted, and is used to connect the horizontal plate 24 integrated with the blade 5 and the rotary antenna 4. Reference numeral 30 is a notch provided with the output antenna 3 as a substantially symmetrical center in order to adjust the radiation position of high-frequency energy from the periphery of the rotary antenna 4 and reduce uneven heating.

Next, the function and effect of the embodiment configured as described above will be described. A part of the high frequency energy radiated from the output antenna 3 of the magnetron 2 is radiated toward the lower side of the antenna cover 7 from the radiation port 26 opened equivalently to the rectangular waveguide in the center of the rotating antenna 4, and the rest. Is a radial antenna transmission line formed between the rotating antenna 4 and the upper surface 6 of the heating chamber 1, that is, a radial line type transmission line.
Is radiated from around the antenna to below the antenna cover 7. That is, since the high frequency energy radiated from the output antenna 3 is radiated from the center and the periphery of the rotary antenna 4, the positional relationship between the tip of the output antenna 3 and the radiation port 26, the outer dimensions of the rotary antenna 4 and the dimensions of the radiation port 26. It is possible to uniformly heat the object to be heated installed in the heating chamber 1 from both the peripheral portion and the central portion by relatively adjusting. Further, since the wind from the cooling fan 9 hits the blades 5 to rotate the rotary antenna 4, the direction of the electric field radiated from the radiation port 26 and the periphery of the rotary antenna 4 having the cutout 30 are radiated. The direction of the generated electric field changes momentarily, and more uniform heating is possible. Also, the radiation port 26 and the cutout 30
By providing the output antenna 3 so as to be symmetrical and substantially at the center, stable performance can be obtained with less rotational shake.

The sizes of the long side 27 and the short side 28 of the radiation port 26 are selected in the same manner as the cross-sectional dimensions that can transmit the fundamental mode TE _{10 of the} waveguide that is normally used for high power, and the rotating antenna 4 and the heating antenna 4 are heated. Since a radial line, which is a kind of radial transmission line, is formed between the upper surfaces of the chamber 1, the output antenna 3 and the rotating antenna 4
The reflection between the two is reduced and the standing wave is suppressed, and the output antenna 3 and the metal edge of the inner peripheral edge of the radiation port of the rotating antenna 4 are brought closer to each other, and the output antenna 3 penetrates the radiation port 26. Even if the output antenna 3 and the rotating antenna 4 are brought close to each other and the object to be heated is not placed in the heating chamber 1 and is in an air-fired state, the output antenna 3 and the rotating antenna 4 are
It has been experimentally confirmed that no sparks occur between and.

EFFECTS OF THE INVENTION As described above, according to the present invention, the reflection between the output antenna and the rotating antenna is reduced, the generation of standing waves is suppressed, and the inner peripheral edge metal end of the radiation port of the rotating antenna and the output antenna are separated. Even if they are brought close to each other or if the tip of the output antenna is further penetrated through the radiation port, no spark is generated, and high-frequency energy can be radiated from the radiation port of the rotating antenna and around the rotating antenna. Therefore, the vertical positional relationship between the output antenna and the rotary antenna can be freely selected, and the idle space between the rotary antenna and the upper surface of the heating chamber can be reduced, and the high-frequency heating device can be made compact as a whole.

Further, by providing the notch for adjusting the high-frequency energy radiation position around the rotary antenna at a symmetrical position with the output antenna as the center, rotational shake is reduced and stable performance is obtained. In addition, since the rotating antenna has a flat plate shape, it can be easily manufactured from a single metal flat plate by punching, which has an economical ripple effect.

[Brief description of drawings]

FIG. 1 is an enlarged view of a main part showing a mounting structure of a rotary antenna 4 in a high frequency heating apparatus according to an embodiment of the present invention.
FIG. 2 is a diagram showing the relationship between the output antenna 3 and the rotary antenna 4 as seen from the direction of the arrow AB in FIG. 1, and FIG. 3 is a schematic cross-sectional view of the main parts 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… radiating port, 27… long side, 28
… Short side, 30… cutout.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-51-134949 (JP, A) Actual development 60-88497 (JP, U) Actual public 53-31469 (JP, Y2)

Claims (1)

[Claims] 1. A magnetron (2) is directly attached to an upper surface (6) of a heating chamber (1) for accommodating an object to be heated, and an output antenna (3) of the magnetron (2) is a center of a sheet of metal. A flat plate-shaped rotary antenna (4) integrally formed from a flat plate is installed in parallel with the upper surface (6) of the heating chamber (1), and is extended to the rotary antenna (4) about the output antenna (3) as a center. The side (27) is larger than 1/2 of the used wavelength and the short side (28) is larger than 1/4 of the used wavelength.
A high-frequency heating apparatus, characterized in that the rotary antenna (4) is provided with a cutout (30) having the output antenna (3) as a center of symmetry.