JPS602756B2 - High frequency heating device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high frequency heating device having a heating chamber, and in particular,
The purpose is to effectively suppress radio wave leakage from the vicinity of the heating chamber entrance with a simple structure.

Conventionally, as a structure for suppressing this type of radio wave leakage, it is known to provide a so-called choke structure consisting of a resonant cavity with an input/4 length (input is the effective wavelength of the leaked radio waves) around the entrance of the heating chamber.

However, since such a choke structure requires a considerable cavity volume, it has the disadvantage that, for example, when it is provided in a door for opening and closing a heating chamber entrance, the door thickness becomes large. The present invention has been made in view of these drawbacks, and includes arranging a dielectric resonator structure having a resonance dimension relationship with leakage radio waves in the radio wave leakage path around the closing of the heating chamber, and using the structure in a plurality of TE modes. According to the present invention, radio wave leakage can be effectively suppressed without using a conventional choke structure, and the dielectric resonator device according to the present invention is Even when the structure is provided on the door, the thickness of the door does not increase.

In the electromagnetic body resonator described above, a dielectric body is disposed within the radio wave propagation path, and if its shape is set in relation to the resonance dimensions of the radio waves, the dielectric body itself acts as a resonator.

This principle itself is already known in the field of microwave communication technology, but unlike communication technology that handles weak microwave energy, it is used to prevent radio wave leakage in high-frequency heating equipment that handles strong microwave energy. It has not yet been recognized that dielectric resonators work effectively.
The novel concept of the present invention is that a dielectric resonator is applied to prevent radio wave leakage in a high-frequency heating device, and the radio wave leakage prevention effect can be achieved in place of the conventional choke structure.

On the other hand, a dielectric resonator resonates in either the TE mode or the TM mode, and it has been found that the TE mode is suitable for preventing radio wave leakage in a high frequency heating device.

That is, in the case of the TM mode, the resonant frequency of the dielectric resonator changes greatly as the door is opened, and therefore prevention of radio wave leakage becomes incomplete. The reason for the large change in the resonance frequency in the TM mode is not clear, but in this mode, the lines of electric force in the resonance state exist outside the resonator. When the distance between the metal door wall and the main body wall changes and the conductor arrangement near the dielectric resonator changes, it is thought that the electric lines of force will be particularly affected and the resonant frequency will change.
In E mode, the lines of electric force are confined and swayed inside the resonator, so it can be inferred that there is little change in the resonant frequency due to opening and closing of the door. Figures 1 and 2 show a microwave oven as an example device, where 1 is a heating chamber, 2 is a metal body that spatially limits the heating chamber, and 3 is a rectangular closure in front of the heating chamber 1 that opens and closes. This is the door that opens. The door 3 includes a metal door frame 4 having a central see-through window, and a metal see-through plate 40 fixed to the center see-through window of the door frame and having a large number of see-through holes. Although the door 3 is omitted in the figure, it has a hinge on its right end side,
The left end side rotates around the hinge.

FIG. 1 shows the door in the open state, and FIG. 2 shows the door in the slightly opened state. When the door is closed, the flat part 4a of the door frame 4
faces the front surface 2a of the main body 2, and therefore a radio wave leakage path is formed in this facing portion, and the dielectric resonator structure 5, which is a feature of the present invention, is disposed in the path. Although only a portion is shown in the figure, this arrangement is the same all around the rectangular entrance of the heating chamber 1. The dielectric resonator mechanism 5 has a plurality of individual dielectric resonators 5a, 5a, . It is.

Specifically, each dragon body resonator 5a has a height A, a width B, and a length C.
The heating chamber is made up of rectangular parallelepiped-shaped electrical body plates, which are arranged at regular intervals so that the length direction thereof coincides with the direction perpendicular to the opening edge direction of the heating chamber, that is, the X direction in the figure. What is important is that the dimensions A, B, and C of the dielectric resonator are determined so that the dielectric resonator resonates in the TE mode against leakage radio waves. FIG. 3 shows the distribution of electric lines of force 6 and magnetic lines of force 7 in the TEm6 mode resonance state of the TE mode type dielectric resonator 5a having height, width B, and length C, and as is clear from the figure, If the magnetic field of the propagating radio wave has a component in the composite direction of the magnetic lines of force 7 in the resonance mode, that is, in the width direction of the resonator (Y direction in the figure), the leaked radio wave will be resonantly coupled to the dielectric resonator 5a. The traveling energy of the shinobi is greatly attenuated.
Also, the electric lines of force 6 in the resonance mode' are the dielectric resonator 5a.
A closed loop is formed in the internal vertical plane, and therefore, according to image theory, even if the conductor plate 8 is inserted in a horizontal plane at half the height of the resonator 5a, the lines of electric force 6 intersect perpendicularly to the conductor, so its distribution is Therefore, when the dielectric resonator 5a is installed on the conductor plate 8, the height of the resonator only needs to be half A. 2) In the dielectric resonator 5a of this embodiment, the door frame flat portion 4a corresponds to the conductor plate 8, and resonates in the TEo,6 mode, so that the leakage radio waves are directed toward the heating chamber entrance edge, that is, in the figure. If the magnetic field components match in the middle Y direction, such leakage radio waves will be greatly attenuated by the presence of the resonator 5a and will not be able to reach the outside.

The electromagnetic body resonator 5a is formed of a compact body mainly composed of barium titanate with a specific electrical constant S of 90, and each dimension is A=7.5 ribs, 8=6 ribs. , C=11.5 willow, and its attachment is carried out by metallizing the back surface of the resonator in advance and soldering or brazing the back surface to the flat portion 4a of the door frame. Further, the arrangement interval 1 of the dielectric resonators 5a, 5a, .
For example, let the distance between the two points be 10.5 willows. 4 and 5 show other embodiments in which the arrangement state of the dielectric resonators 5a is changed, and when expressed in the coordinate system shown in FIG. 2, in the case of FIG. 4, each resonator 5a are arranged with their length directions alternately in the are doing.

At this time, the arrangement interval 1 of the resonators expressed by the inter-plane distance in FIGS. 4 and 5 is assumed to be 2 and 3, respectively. In these cases, in addition to leaked radio waves having a magnetic field component in the Y direction, leaked radio waves having a magnetic field component in the x direction are also attenuated, resulting in a more reliable radio wave leakage prevention effect. As is clear from the above explanation, according to the present invention, radio wave leakage can be effectively suppressed with a very simple structure in which a plurality of TE mode dielectric resonators are arranged, and the conventional choke structure is not required. Therefore, the door thickness can be made thinner.

It goes without saying that the present invention can be used in combination with the conventional deterrent structure, and the same effect can be obtained even if the dielectric resonator mechanism is provided on the main body side.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of the lozenge portion of an embodiment of the present invention, FIG. 2 is a perspective view thereof, FIG. 3 is a perspective view showing the resonant state of the resonator, and FIG.
This figure and FIG. 6 are plan views showing a dielectric resonator arrangement in another embodiment. 5a...Mysterious electric resonator. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1. In a high-frequency heating device in which a dielectric resonator structure having a resonance dimension for leakage radio waves is arranged in a radio wave leakage path around the opening of the heating chamber, the dielectric resonator structure has a plurality of T.
A high-frequency heating device comprising an E-mode dielectric resonator.