JPS6047712B2 - High frequency heating device - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a high-frequency heating device that uses a rotating antenna to supply high-frequency energy from a high-frequency oscillator to a heating chamber. The present invention solves the conventional manufacturing problems of rotating antennas used in heating devices, and at the same time prevents sparks at the tip of the antenna, thereby providing an inexpensive and highly reliable rotating antenna.

In the case of conventional high-frequency heating devices that are equipped with an electric heater and also have a burn-out self-cleaning function, the temperature inside the refrigerator becomes extremely high, so the rotary drive shaft of the rotating antenna is made of a highly heat-resistant dielectric material such as ceramic. materials used. However, as is well known, ceramic is extremely hard and easily broken, so it has been extremely difficult to connect it to a metal antenna in a reliable and inexpensive manner from the perspective of mass production. A method that has been proposed and partially implemented in the past is to cut female or male threads in both the ceramic rotary drive shaft and the antenna, respectively, and connect them using these. 2. Part of the surface of the ceramic shaft is metallized,
Connect to the antenna by brazing.

3. Small holes on both sides of the ceramic shaft and antenna.
Drill and insert a rivet or pin into this hole using a rivet or the like.

In case 1, the shrinkage of ceramic during the firing process is very large, so it is difficult to maintain the precision of the screws, resulting in very high costs. The drawback was that the series of steps was quite expensive.

In the case of No. 3, the cost is relatively low, but there are quality problems such as the insulators breaking or cracking due to the impact during crimping.

On the other hand, since the electric field near the tip of the antenna is very high, there is a problem that sparks occur near the tip of the antenna when the open circuit is operated with dry firing or radial load and the standing wave ratio becomes very large. Ta. Therefore, the present invention solves the above-mentioned conventional problems with a simple configuration and provides an inexpensive and reliable rotating antenna. An embodiment of the present invention will be described below with reference to the accompanying drawings.

In FIG. 1, 1 is the main body of the high-frequency heating device, 2 is a heating chamber formed in the main body, 3 is a door that allows the front opening of the heating chamber 2 to be opened and closed, 4 is a high-frequency oscillator, and 5 is a high-frequency oscillator 4. A waveguide 6 transmits the high frequency energy generated by the waveguide to a joint with the heating chamber 2, and 6 is a rotating antenna that supplies the high frequency energy transmitted by the waveguide 5 into the heating chamber, and is connected to a motor 7 which is a driving source. It is connected to a drive shaft 8 made of a dielectric material such as ceramic.

Reference numeral 11 is an electric heater for making grilled food possible.

As shown in FIG. 2, the rotary antenna is composed of an antenna main body part 9 and an auxiliary part 10.

In Figure a, a slit is cut in the axial direction at the tip of the vertical part of the antenna main body 9, and a pair of protrusions are provided in the part of the wall perpendicular to the slit from the outside to the inside. There is. In Figure b, the rotary drive shaft 8 made of ceramic has a hole perpendicular to the axial direction, and when the drive shaft is inserted into the antenna body 9, the tip opens due to the slit provided in the antenna body, and the shaft rotates smoothly. The drive shaft can be inserted, and the hole in the drive shaft and the projection provided on the antenna body are fitted and fixed. The antenna body 9 is made of stainless steel, but since it requires bending into an L-shape, it has been smoothed to facilitate this process, so it has less springiness. Therefore, after inserting the drive shaft 8, the tip is slightly expanded as shown in FIG. 2b. Next, as shown in figure c, when the antenna auxiliary part 10 is covered from the bottom of the antenna body and pushed up to the tip, the inner diameter of the antenna auxiliary part is made almost equal to the outer diameter of the main body. The expanse of the tip of the main body is then narrowed to ensure that the drive shaft and the antenna main body are in contact with each other.

Thereafter, by processing the antenna body 9 and the auxiliary part 10 by brazing or the like, a reliable electrical connection can be obtained.
Finally, bend the antenna body into an L-shape as shown in Figure 2d to complete the process.

Incidentally, when the antenna auxiliary part and the antenna main body are connected by spot welding, a structure as shown in FIG. 3 can be obtained. However, in this case, it is necessary to spot weld the tip of the antenna body after squeezing it out using another jig or the like. When an antenna is made using the method described above, the drive shaft can be simply a straight bar, so it is much simpler than the conventional threaded type, and there is no need to metalize the ceramic surface, so the cost is reduced. In addition, the antenna and drive shaft are fixed by splitting the antenna tip, inserting the drive shaft, and then squeezing the antenna tip using the antenna auxiliary part without applying impact. There is no need to worry about cracks, etc.

(Ceramics are weak against impact, but strong against compressive force.) Furthermore, the antenna auxiliary part attached to the tip of the antenna body has a larger diameter than the antenna body, and its tip is rounded, making it easier to use the antenna. Since a gap is maintained between the tip of the auxiliary part and the drive shaft, the problem of sparks occurring from the tip of the antenna along the surface of the drive shaft and the upper wall of the waveguide can be solved.

(The drive shaft is made of a dielectric material, and since electric lines of force tend to concentrate in the dielectric part, sparks are likely to occur if the tip of the antenna is in contact with or very close to the drive shaft surface.) ) Also, a slight change in the dimensions inside the antenna's waveguide has a very large effect on the operating point of the high-frequency oscillator, but if the configuration shown in Figure 2b remains, for example, the inside of the antenna's waveguide will The dimensions include both the variation in the pitch between the two holes drilled in the drive shaft and the variation in the dimension from the tip of the antenna to the protrusion, so there is a relatively large variation in dimensions, but as shown in Figure c. With this method, when covering the antenna auxiliary part, you can use a jig to match the dimensions between the hole on the drive shaft and the tip of the antenna auxiliary part, so the width of variation can be narrowed, and the operating point of the high frequency oscillator can also be adjusted. It can be kept within the ideal range.

Furthermore, by enlarging the tip of the antenna, the antenna itself can have broadband frequency characteristics, and can exhibit stable antenna function even in the face of frequency fluctuations and variations. As explained above, the present invention provides a highly reliable rotating antenna that has a simple configuration, is inexpensive, has good workability, has good dimensional accuracy, does not cause sparks during operation, and has improved frequency characteristics. can be provided.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of a high-frequency heating device showing an embodiment of the present invention, and FIGS. 2 a to 2 d are a cross-sectional view and a side view of a rotating antenna of the same essential part. 4...High frequency oscillator, 5... Waveguide,
6...Rotating antenna, 7...Motor, 8...Drive shaft, 9...Antenna body,
10... Antenna auxiliary part.

Claims (1)

[Scope of Claims] 1. A heating chamber, a high-frequency oscillator that supplies high-frequency energy into the heating chamber, a waveguide that transmits the high-frequency electromagnetic waves oscillated by the high-frequency oscillator, and the high-frequency electromagnetic waves transmitted by the waveguide. It consists of a rotating antenna that radiates into a heating chamber, and a plurality of slits are provided in parallel to the axial direction near the tip in the waveguide of the rotating antenna, and at any point on the circumference of the part where the slits are located. A high-frequency heating device characterized in that at least one protrusion is provided from the outside toward the shaft center, and the antenna and the rotational drive shaft are integrally joined via the protrusion. 2. The tip of the antenna is bent approximately at right angles to the axial direction at the slit part, and an antenna auxiliary part having a diameter larger than the diameter of the antenna is joined to the bent part by welding, brazing, etc. A high-frequency heating device according to claim 1. 3. An antenna auxiliary part having two diameters, one of which has an inner diameter approximately equal to the outer diameter of the antenna and the other outer diameter which is larger than the outer diameter of the antenna, is placed near the joint between the antenna and the drive shaft at the tip of the antenna. A high-frequency heating device according to claim 1, characterized in that: