JPS5983393A - 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 the Invention The present invention relates to a configuration for efficiently radiating high frequency energy generated from a high frequency oscillator in a high frequency heating device into a heating chamber.

Conventional configurations and their problems Conventionally, in power feeding systems that couple a waveguide and a heating chamber at high frequencies, the waveguides used are generally rectangular in shape due to impedance matching and ease of processing. is often used.

Moreover, the TE1o mode occupies most of the excitation modes of the waveguide in terms of space and economy.

When inserting a high-frequency oscillator antenna into the above waveguide and emitting high-frequency energy, we measured the excitation mode and found that TE
Although the waveguide is excited in the 1o mode, the standing waves within the waveguide are not necessarily constant. However, the calculated values and actual measurements do not necessarily match and show different values, and there is a slight deviation in the excitation state between the antenna section of the high frequency oscillator and the coupling rod, and complete excitation is not possible. Therefore, in order to correct this deviation, we corrected it by adjusting the flange dimensions of the waveguide, and also installed an impedance matching bare hand called an iris inside the waveguide.
Impedance matching was performed between the heating chamber and the waveguide.

However, when using the method described in section 2 above, the impedance of the waveguide is basically matched to the impedance of the heating chamber, which inevitably results in a high frequency imbalance, the waveguide becomes hot, and a single output is lost. This is the cause of the decline. It has also been found that if impedance matching is achieved by reducing the dimension a' between the connecting rod 5 and the waveguide 4 by approximately /2, the operating point of the high frequency oscillator will change greatly with a small dimensional error.

FIG. 1 shows the basic configuration of a high-frequency heating device. 1 is a heating chamber that stores the object to be heated; 2 is a high-frequency oscillator that emits high-frequency energy; 3 is an antenna that radiates high-frequency energy; and 4 is a guide that propagates the high-frequency energy radiated from the antenna to the heating chamber side. The wave tube 6 consists of a coupling rod that couples the waveguide 4 and the heating chamber 1 in a high frequency manner.

Figure 2 shows the waveguide configuration in a conventional example, Figure 3 A is a cross-sectional view, the opening in the figure shows the calculated standing wave ratio in the waveguide, and the figure C shows the standing wave in the waveguide. This shows the actual measured value of the ratio. The mouth standing wave ratio is indicated by the sleeve.

Phrases: tube wavelength, λ: free space wavelength, λ. :The cutoff wavelength or cutoff wavelength of the waveguide is twice the width a of the waveguide 4 in the TE1o mode, so it is expressed by the following equation.

If the value is calculated from the theoretical value of λ, then the antenna 3 of the high frequency oscillator 2
shows the highest high-frequency voltage because it emits high-frequency energy. Therefore, the back flange dimension of the waveguide 4 coming from there is such that the high frequency voltage peaks at the antenna 3 and the current is 0, so if you easily guess, the dimension between the antenna 3 and the back flange bA, /4, it is possible to short-circuit in terms of high frequency, and the distance between the antenna 3, which radiates the high frequency energy obtained from the high frequency oscillator into the waveguide 4, the waveguide 4 and the heating chamber 1 is Dielectrically coupled. The distance between the coupling rods 6 is determined by the fact that both the antenna 3 and the coupling rod 5 are excited at high frequency and electric field strength, so the electric field strength is the maximum for both.
Therefore, as mentioned in the previous section, in the waveguide 4 used, the internal wavelength λ is determined by the width C dimension. You can ask for. Its internal wavelength λ. %, exactly %λ. Theoretically, it can be easily determined that the antenna 3 and the coupling rod 5 should be coupled at positions that are an integral multiple of .

However, in reality, it does not follow the theoretical value, and in fact, the waveguide width C dimension is such that the excitation mode in the waveguide 4 is the TE1o mode, both in terms of space and economically as described in the previous section. Adopt. If the same mode is adopted, the waveguide width C dimension will inevitably be 122.2 mm for a high frequency of 2450 mm.
The range is limited to 61.1 mm. If we consider that the waveguide width is limited to 90 mm, the resulting wavelength within the guide will be 166.4 mm from the previous equation. In other words, from the theoretical value, the barafuruff 9b dimension is &/4 and 41.6m.
It can be seen that the dimension between the antenna 3 and the coupling rod 5 should also be 41.6n (n=integer). However, if the back flange dimension is 41.6 mm, the impedance matching between the heating chamber and the inside as seen from the antenna 3 cannot be achieved well.
Radio waves do not enter the heating chamber 1 easily, resulting in poor output.

FIG. 4 shows a standard waveguide, and one flange of the waveguide is short due to the 5 dimensions, and one side is called a non-reflection terminator 6. When high-frequency energy is emitted from the antenna 3, it combines those with no reflected waves to produce a high-frequency output, and in this case, the measured value of the high-frequency output is shown when the back flange dimensions are arbitrarily changed. In other words, the characteristics of a general high-frequency oscillator are that the back flange size is about 20mm, or the size is &j: 20mm + n 9/2 (n - integer), or that it can effectively emit high-frequency energy. This could be easily confirmed experimentally.

The same experiment shows that it is best to set the back flange dimension to 20 mm.

In Fig. 3, the back flange dimension l) is set to the optimum dimension 20+mn determined by the experiment described in the previous section, and the distance between the antenna 3 and the coupling rod 6 is determined depending on the waveguide 4 used. The determined tube wavelength is λ/2!
If it is set to an integral multiple of i (3λg/2 in the experiment) and the impedance is matched with the heating chamber 1, the dimensions of the connecting rod 5 and the short flange al will be approximately A y... It ends up becoming. In this state, when high-frequency energy is oscillated and the standing wave inside the waveguide 4 is measured, a disturbed standing wave that is quite different from the theoretical standing wave (shown in the figure) as shown in Figure C is obtained. It shows. Even if high-frequency energy is supplied to the heating chamber 1 in this state, the energy loss will be large, leading to insufficient output, and the waveguide 4 will also become extremely hot. In other words, although the high-frequency oscillator 2 is outputting output, the coupling between the waveguide 4 and the coupling rod 6 and between the coupling rod 5 and the heating chamber 1 is poor, and the high-frequency energy is not radiated efficiently. , resulting in insufficient output or abnormal heating of the waveguide 4. For this reason, the voltage standing wave ratio (V, S, W, 'R) in the waveguide 4 also shows a high value, and for this reason, the waveguide 4 and the heating chamber 1 are inductively coupled by the coupling rod 5. In the case of the power feeding method, if high frequency energy is emitted in the heating chamber 1 in a state close to dry firing, the high frequency energy will naturally be radiated into the heating chamber 1, but if there is no load inside the heating chamber 1, A portion of the same energy also returns into the waveguide 4. In the same situation, the waveguide 4
As a result, the voltage standing wave ratio generated within the high-frequency heating device increases, eventually breaking the insulation between the coupling rod 5 and the waveguide 4, and eventually causing a spark (discharge phenomenon) that can be fatal to the high-frequency heating device.

OBJECT OF THE INVENTION The present invention solves the above-mentioned conventional drawbacks, and aims to efficiently feed high-frequency energy generated from a high-frequency oscillator into the heating chamber, thereby more efficiently heating the object to be heated, and reducing sparks during dry firing, etc. (Discharge phenomenon) is also aimed at creating a power supply configuration that is less likely to occur.

Structure of the Invention In order to achieve the above object, the present invention sets the distance between the antenna 3 and the back flange to 20 mm in a certain rectangular waveguide in which the TE1o mode is established.
The purpose is to set the distance p dimension between the antenna 3 and the coupling rod 5 to a dimension different from the theoretical value dimension.

The theoretical value of the same dimensions is nAg/2, as stated in the previous section.
(n - integer), but the same size range is 2n
/4/4 where λy>P>2(n-1)λg. If the same dimension pt is set and in that state the impedance of the heating chamber as seen from the antenna is matched, the dimension between the coupling rod and the short flange can be matched.

If the dimensions are the same, the dimensions will be close to the theoretical value in terms of high frequency as shown in the previous section, and if high frequency energy is oscillated in this state, there will be some supply loss, but the loss of high frequency energy will not be as high as shown in the previous section. - It is easy to use and does not cause a lack of output.

Also, abnormal heating of the waveguide itself is eliminated.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

^ The opening in Figure 3 mentioned in II is the theoretical standing wave ratio in "Calculation" 2. The standing wave ratio (c) is the actually measured standing wave ratio as described in the previous section. Comparing the difference between the two standing wave ratios and 7., they differ simply because a is the theoretical value and / is the dimension when the impedance is matched in the case in the previous section. Furthermore, the antenna 3 of the high-rise λ wave oscillator 2 generates a difference d-d'=e between d and d', which is g/4 for the first time.

As you can see, the disturbance of the standing wave in Figure 3 C is caused by the coupling rod 5.
There is a lot of disturbance nearby. In other words, it can be seen that the root of the difference between the theoretical value and the actual value is the difference in dimension e.

By setting the dimension p between the antenna 3 and the coupling rod 6 to be smaller than the theoretical value by the dimension e, it is thought that the various defects and impedance matching described above will also be approximately the same as the theoretical value.

FIG. 5 shows an embodiment of the present invention, in which the antenna 3 and the coupling rod 5
By setting the dimension between the This is a measurement of waves. In this case, the connecting rod 6 and short flange dimension a' when impedance matching can be achieved.
had a dimension of λg/4≧a>2g78, showing a value almost close to the theoretical value.

Effects of the Invention As described above, according to the present invention, the supply loss of high frequency energy into the heating chamber can be minimized.1. It was possible to effectively radiate it into the heating chamber. Moreover, the phenomenon of overheating of the waveguide itself has also disappeared. Also, the operating point of the high frequency oscillator will not show large changes due to variations in the dimensions of each part, and the variations in output will also be suppressed.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of the main part of a conventional high-frequency heating device, and Fig. 2 is a partially cutaway perspective view of the main part. Figure 3A is a side cross-sectional view of the waveguide section, and Figure 3C is a characteristic diagram showing the voltage standing wave ratio.
Figure 4A is a sectional view of the main part of a conventional standard waveguide, the opening of the figure is a characteristic diagram showing the relationship between the back flange dimensions of the waveguide and high frequency output, and Figure 5A is an embodiment of the present invention. 1 is a side cross-sectional view of a waveguide portion of a high-frequency heating device, and the opening of the figure is a characteristic diagram showing actually measured values of voltage standing wave ratio. 1... Heating chamber, 2... High frequency oscillator,
3...Antenna, 4...Waveguide, 5.
...Coupling rod, a... Width of waveguide, b...
...Back flange dimension, C... Width dimension, S... Inner pipe wavelength, P... Antenna 3
and the connecting rod 5. Name of agent: Patent attorney Toshio Nakao and 1 other person
1 Illustration number (c) 2 Illustration goo! %-'y:, 1 Written amendment to procedure (March/6, 1988, Director General of the Patent Office 1 Display of the case 1986 Patent Application No. 193013 2 Name of the invention High-frequency heating device 3 Person making the amendment Relationship to the incident Patent application Address 1006 Kadoma, Kadoma City, Osaka Name Name
(582) Matsushita Electric Industrial Co., Ltd. Representative Yama
Toshihiko Shimo 4 Agent 571 Address 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (1)

[Claims] a heating chamber for storing an object to be heated; a high-frequency oscillator for supplying high-frequency waves into the heating chamber; an antenna for radiating high-frequency energy obtained from the high-frequency oscillator; It is equipped with a waveguide that propagates toward the chamber side, and a coupling rod made of a rotatable metal body that couples the waveguide and the heating chamber at high frequency, and the distance P between the coupling rod and the antenna is 2 n. Ay/4
) P)2(n-1)su/4. (where n is an integer).