JPS5916713B2 - High frequency heating device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high-frequency heating device that prevents frequency components other than the fundamental wave from being transmitted into a heating chamber by imparting frequency selectivity to a waveguide section.

A high-frequency heating device with a closed structure has a door for taking in and out the heated object, and in order to ensure safety, this door must be provided with a structure to prevent radio wave leakage.

In the conventional technology, the radio wave leakage prevention structure is provided for the fundamental wave with the highest power level, so the leakage prevention effect is not sufficient for frequencies other than the fundamental wave. Furthermore, if a leakage prevention structure that is effective over a wide band is to be adopted, the structure must be complicated and large. In order to improve this point, we created a structure in which the radio waves from the high-frequency oscillator are transmitted to the heating chamber through a waveguide, and by inserting multiple conductor plates into the waveguide, only the fundamental wave of the high-frequency oscillator is transmitted. Although there is a known technique for constructing a resonant circuit that selectively passes through the conductor, there are still technical difficulties in implementing it because the spacing between multiple conductive plates must be precisely determined. Stay tuned. 15 The present invention has been made in view of the above-mentioned drawbacks and has been improved by configuring a resonant circuit in the waveguide that selectively passes only the fundamental wave of the high-frequency oscillator, thereby creating a structure for preventing radio wave leakage in the heating chamber door. This provides a structure that not only simplifies the process but also makes it easier to insert the resonant circuit into the waveguide (by more than 20V).

One or more conductor plates with multiple holes or multiple cuts in the waveguide to transmit only the fundamental wave to the heating chamber and block other noise frequencies from propagating. is parallel to the electric field of the fundamental wave, or is inserted in the waveguide axis direction at an angle. In addition, since even one conductor plate is sufficiently effective, the number of parts in the circuit can be reduced, and the dimensional accuracy of the conductor plate can be easily achieved by punching with a press, etc. , it is possible to easily and accurately determine the resonant frequency of the conductor plate that operates as a resonant blade circuit. Embodiments of the present invention will be described with reference to the accompanying drawings.

In Fig. 1, 1 is a heating chamber, 2 is a heating chamber door, 3 is a waveguide, 4 is a coupling hole between the heating chamber and the waveguide, 355 is a magnetron antenna, 6 is a magnetron, and T is inserted into the waveguide. This is a conductor plate made of aluminum. Figure 2 is an example of a pattern of a conductor plate that is connected to a waveguide.

Figure 2 a shows the one with a rectangular hole, Figure 2 shows b
2 has an oval hole in it, and c in Figure 2 has a cut in the conductor plate. To explain its operating characteristics using a in Fig. 2 as an example, when this conductor plate is inserted into the waveguide as shown in Fig. 3, the width portions of ω1, ω2, and ω3 in a in Fig. 2 are acts as an inductive element in circuit terms, and the hole portion acts as a capacitive element, so that the entire conductor plate constitutes a resonant circuit, and the second
When the length of the holes Tl and t2 in the tube axis direction in a of the figure is λ7, the wavelength in the waveguide of the fundamental wave of the high frequency oscillator is λ7,
By selecting approximately λy/2, only the fundamental wave can be passed. Also, B, . The operation of c is similarly explained.

Further, although FIG. 2 only shows the case where there are two holes or cuts in the conductor, the same operation can be performed even if there is one hole or notch, or if there are three or more holes. Fig. 3 shows the case where the conductor plate is inserted into the waveguide, but in order to actually insert and fix the conductor plate into the waveguide, the steps shown in A, .
As shown in b, bent portions may be attached to the top and bottom of the conductor plate, and these portions and the waveguide wall may be fixed with fasteners such as screws.

Furthermore, it goes without saying that spot welding may be used instead of fasteners to secure the waveguide to the wall of the waveguide tube, or spot welding and fasteners may be used in combination. Another method of mounting is as shown in Figure 4c, where the conductor plate is molded from an elastic material, one end is spot-sliding or fixed with a fastener, and the other end is attached to the waveguide wall using its elasticity. There is also a way to keep it in contact with the
In the above embodiment, only one conductor plate is inserted, but by inserting multiple conductor plates as shown in Fig. 5, the equivalent electrical length of the conductor plate can be changed and impedance matching can be achieved. It can be used for. Further, the length of the conductor plate in the tube axis direction can be reduced, and the resonant circuit can be configured smaller. However, for the purpose of simply passing only the fundamental wave, a single conductor plate is sufficient to achieve the purpose.

As explained above, the present invention configures a resonant circuit that allows only the fundamental wave to pass by inserting a conductor plate having a plurality of holes or a plurality of cuts in the axial direction of the waveguide. This simplifies the structure for preventing radio wave leakage in the door. Instead of configuring a resonant circuit using multiple conductor plates, the resonant circuit is created by making multiple holes or cuts in one conductor plate. Since the structure can be simplified, and the resonant frequency can be determined by the pattern rather than the spacing of the conductor plates, the resonant frequency can be determined easily and accurately.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of a high-frequency heater showing an embodiment of the present invention, and FIG. 2 shows three patterns of conductive plates arranged in a waveguide. Figure 3 shows a waveguide with conductor plates arranged in this way. a
is a side view, b is a plan view, and c is a front view taken in section along BA-A'. FIG. 4 shows a specific method for attaching the conductor plate to the waveguide. FIG. 5 shows an example in which two conductor plates are inserted into the waveguide. 1...Heating chamber,
2... Heating chamber door, 3... Waveguide, 5... Magnetron antenna, 6... Magnetron, r... Conductor plate, 8... Fastener.

Claims (1)

[Claims] 1. In a high-frequency heating device that transmits radio waves from a high-frequency oscillator to a heating chamber through a waveguide, one or more conductor plates with multiple holes or multiple cuts are placed inside the waveguide of the high-frequency oscillator. By inserting the conductor plate in the axial direction of the waveguide tube parallel to or inclined to the electric field of the fundamental wave, and by bringing both ends of the conductor plate into contact with the waveguide wall, a resonant circuit in which the conductor plates are electromagnetically coupled is created. A high-frequency heating device characterized in that frequency components other than the fundamental wave of the high-frequency oscillator are reflected to the high-frequency oscillator side, and only the fundamental wave is sent into the heating chamber.