JPS6332236B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high frequency heating device of a type that uses a rotating antenna to supply radio waves into a heating chamber.

Conventionally, when a rotary antenna is used in a type of high-frequency heating device that uses an electric heater in combination, the temperature inside the refrigerator becomes extremely high. A high heat-resistant dielectric material was used.

However, since ceramic has a much higher dielectric constant than air (air has a dielectric constant of about 1, ceramic has a dielectric constant of about 5), a sudden change in impedance occurs at the boundary between air and ceramic, and therefore, the impedance changes in this vicinity. The reflection of radio waves increases. On the other hand, near the antenna inside the waveguide and the coupling hole between the heating chamber and the rotating antenna, there is a very high electric field, so if a large reflection of radio waves occurs near these areas for the reasons mentioned above, it will become even more extreme. Local electric field concentration occurs, and a discharge phenomenon called sparking is particularly likely to occur during operation under light loads.

A specific conventional example is shown in FIG. The oscillated radio waves pass through the waveguide 4 and are irradiated into the heating chamber 2 by the rotating antenna 5. The rotating antenna 5 consists of a vertical part 7 which is a rotation axis and a horizontal part 8.
A rotary drive shaft 9 is connected to the tip. Reference numeral 11 denotes a sealing plate for sealing the coupling hole of the waveguide 4 and the heating chamber 2, which also serves as a bearing for pivotally supporting the rotating antenna 5, and is made of a dielectric material such as ceramic.

In this conventional structure, as described above, a sudden impedance change occurs at the boundary line of the sealing plate near the coupling hole, and a very large radio wave reflection occurs against the incoming radio wave. Therefore, the standing ratio in this vicinity becomes very high, and a locally abnormally high electric field is generated, which makes it easy for sparks to occur in that area, especially during light load operation. This phenomenon becomes more pronounced as the difference between the dielectric constant of the material of the sealing plate and that of air increases.

If such sparks occur continuously during use, not only will the user be surprised, but the resulting high heat will damage the antenna, waveguide, etc.

The present invention improves the shape of the sealing plate at the coupling hole between the waveguide, the heating chamber, and the rotating antenna.
It is an object of the present invention to provide a high-frequency heating device that prevents sudden impedance changes near an antenna and has stable performance that does not generate sparks or the like.

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

In Figure 1, 1 is the main body, inside which is the heating chamber 2.
There is. Radio waves oscillated by the high-frequency oscillator 3 pass through a waveguide 4 and are irradiated into the heating chamber 2 by a rotating antenna 5 (hereinafter referred to as an antenna). Reference numeral 6 denotes a door that allows the front opening of the heating chamber 2 to be opened and closed. The antenna 5 consists of a vertical part 7 which is a rotating shaft and a horizontal part 8. A rotary drive shaft 9 made of a dielectric material is connected to the tip of the vertical part 7, and this is connected to an opening in the upper wall of the waveguide 4. It passes through and is connected to the motor 10. A sealing plate 11 serves as a bearing for pivotally supporting the antenna 5 and seals a coupling hole between the waveguide 4 and the heating chamber 2, and is made of a dielectric material such as ceramic.

FIG. 3 shows details of the sealing plate 11. Sealing plate 1
1 is a substantially truncated cone-shaped portion that protrudes into the waveguide 4 so as to cover the vertical portion of the antenna 5, and is thin at the tip and becomes thicker toward the coupling hole of the waveguide 4. 11a. In this way, by making a part of the sealing plate 11 protrude into the waveguide and forming it into a tapered shape with a thinner tip and a thicker base, impedance changes at the boundary line between the air and the sealing plate 11 can be prevented. This is done gradually to minimize radio wave reflection in this area. This eliminates local abnormal electric field concentration, so abnormal operations such as sparks will not occur even when operating under light or no load. Furthermore, since the conventional sealing plate 11 shown in FIG. 1 has a small contact area with the vertical portion 7 of the antenna 5, the antenna 5 must be rotatably supported at two points, including the opening provided in the upper wall of the waveguide 4. However, if the opening of the waveguide 4 and the opening of the sealing plate were misaligned due to variations, there was a problem that the antenna 5 would tilt or become extremely difficult to rotate. Since the sealing plate of the present invention shown in the figure has a sufficiently large contact area with the vertical part of the antenna 5, the rotation axis is required only by the sealing plate 11, so that
Therefore, there is no problem of difficulty in rotating or tilting due to variations.

As explained above, according to the present invention, it is possible to prevent sudden impedance changes in the vicinity of the antenna with a simple structure, prevent sparks from occurring even under light load or no load, and improve antenna tilt and rotation problems due to variations. At the same time, it is possible to provide an excellent high-frequency heating device with stable quality and performance.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of a main part showing a rotating antenna portion of a conventional high-frequency heating device, Fig. 2 is a side cross-sectional view of a high-frequency heating device that is an embodiment of the present invention, and Fig. 3 is a rotating antenna portion of the same device. FIG. 2... Heating chamber, 3... High frequency oscillator, 4... Waveguide, 5... Rotating antenna, 11... Sealing plate, 1
1a... truncated cone shaped part.

Claims (1)

[Scope of Claims] 1. A heating chamber, a high-frequency oscillator, a waveguide, a rotating antenna that couples the waveguide and the heating chamber in a high-frequency manner, and a coupling port of the rotating antenna to the heating chamber sealed. , and a sealing plate serving as a rotational bearing of the rotary antenna, the sealing plate being formed of a dielectric material and having a tapered cross section with a tapered tip and a protrusion into the waveguide. heating device. 2. The high-frequency heating device according to claim 1, wherein the protruding portion of the sealing plate into the waveguide has a substantially truncated conical shape.