JPS6047715B2 - High frequency heating device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high-frequency heating device, and more particularly, to a high-frequency heating device that effectively suppresses leakage radio waves from a radio wave leakage path around an opening of a heating chamber using a TE mode dielectric resonator.

Conventionally, leakage radio waves in this type of device have been suppressed by a radio wave leakage prevention structure in which a choke groove with a length of λ/4 is arranged in the radio wave leakage path, where the wavelength of the leakage radio wave is λ. This has the disadvantage that it requires a considerable cavity volume and therefore the preventive structure becomes large.

Therefore, in the field of microwave communication technology, it has been proposed to suppress the leakage of radio waves from the heating chamber by disposing a well-known dielectric resonator in the radio wave leakage path. In such a case, the dimensions of the radio wave leakage prevention structure depend on the dimensions of the dielectric resonator, but the dimensions of the dielectric resonator are determined by the wavelength of the radio wave to be blocked and the relative dielectric constant Eγ of the resonator, and the resonance In order to reduce the size of the device, it is necessary to use a material with a high dielectric constant.

However, as the dielectric constant Eγ increases, the price of the resonator material generally increases. Therefore, the present invention aims to provide a structure that uses a low-cost resonator with a low permittivity and can reduce its dimensions.The present invention will be described in detail below using an example. .

FIGS. 1 and 2 show essential parts of an embodiment of the present invention,
1 is a main body of the high-frequency heating device; 2 is a heating chamber disposed within the main body 1 and has an opening 3; 4 is a front plate of the main body disposed around the opening 3; and 5 is one end of the front plate 4. There is a door which is pivoted on one side (not shown) and which opens and closes the opening 3 rotatably in the direction of the arrow in FIG. It consists of a body 6 and a punching plate 7 which is attached to the inner edge of the door frame 6 and allows the inside of the heating chamber 2 to be seen through.

The door frame 6 has a frame-shaped flat part Ba whose back surface faces the front plate 4 in parallel when the door is closed and which runs along the four sides of the front plate 4, and the outer edge of the flat part Ba is placed on the side of the front plate 4, that is, at the front plate 4 side. The flat part Ba is composed of a bent part 8b bent perpendicularly to the Y direction in FIG. )
At least the back surface Ba', 8 of the bent part 8b and the inclined part 8c
b' and 8c' have metal surfaces. Further, the flat portion Ba), the bent portion 8b, and the inclined portion 8c form a circumferential groove 9 along the four sides of the door frame 6. Reference numeral 10 denotes a frame-shaped metal radio wave passage wall whose surface closely faces the front plate 4 when the door is closed, and whose inner edges are fixed to the four sides of the end of the inclined portion 8c to cover a part of the circumferential groove 9. When the wavelength of the leaked radio wave is λ, the passage 10 formed by the passage wall 10 and the front plate 4
The length of a in the radio wave leakage direction (Z direction in FIG. 2) is λ/4 or more from the heating chamber wall 2a.

11 covers the remaining portion of the circumferential groove 9 that is not covered by the passage wall 10, and connects the four sides of the curved contact portion 8b and the passage wall 10 so that the surface thereof closely faces the front plate 4 when the door is closed. The frame-shaped low dielectric cover 12 fixed between the four sides of the outer edge is metallized on two orthogonal sides, one side of the metallized surface is the flat part back surface 8a'', and the other side is the bent part back surface 8b''. The dielectric resonators 12 are arranged on each side of the circumferential groove 9 at regular intervals in the direction of that side (the X direction in FIG. 2). There is.

FIG. 3 shows the distribution of electric lines of force 13 and magnetic lines of force 14 in the TEO, δ mode resonance state of the TE mode dielectric resonator 12 having a height of 2 A 1 width B 1 length.

As is clear from the figure, the lines of electric force 13 in the resonance mode
forms a closed loop within the vertical plane inside the dielectric resonator 12, and therefore, according to image theory, the first and second loops are formed in the horizontal plane of half the height and the vertical plane of half the length of the dielectric resonator 12, respectively. Even if the second conductor plates 15 and 16 are inserted, the lines of electric force 13 intersect perpendicularly to the first and second conductor plates 15 and 16, respectively, so that there is no effect on the distribution thereof. In other words, when two orthogonal surfaces of the dielectric resonator 12 are fixedly installed on a conductive plate. In this case, the height of the dielectric resonator 12 may be half A, and the length C may be half. Furthermore, if the magnetic field of the radio waves propagating from the direction of the arrow in FIG. 3 has a component in the direction in which the lines of magnetic force 14 are combined in the resonance mode, the leaked radio waves will be resonantly coupled to the dielectric resonator 12. Its traveling energy is greatly attenuated.
The dielectric resonator 12 of the above embodiment is made of a dielectric material whose main component is barium titanate and has a relative dielectric constant εγ of 90, and its dimensions are as follows: the length a in the X direction in FIG. 2 is 6wn. ．． The length b in the Y direction is 7.5, and the length c in the Z direction is 5.75.

Further, the conductor plates 15 and 16 in FIG. 3 are metal surfaces on the flat back surface 8a'' and the bent back surface 8b'' of the door frame 6. Therefore, the dielectric resonator 12 of this embodiment is suitable.
It resonates in the 1δ mode, and if the leakage radio wave from the Z direction in Figure 2 has magnetic flux in the X direction in the diagram, the leakage radio wave will be resonantly coupled with the dielectric resonator, and its traveling energy will be is greatly attenuated.

In the above embodiment, a rectangular parallelepiped dielectric resonator 12 as shown in FIG. The other surface 19 is attached to the back surface 8b'' of the bent portion, and the other surface 19 is attached to the back surface 8a of the flat portion.
The effect remains the same even if brazing is applied to the heating chamber 2.
The high frequency waves emitted within the heating chamber 2 exist in various standing wave modes due to the starch fan, turntable, heated object, etc. (not shown) inside the heating chamber 2. When the wavelength of the high frequency waves is λ, It was confirmed that the only mode at the time when the radio wave travels more than λ/4 in the parallel plate in the direction of propagation is the parallel plate mode. That is, the passage 10a composed of the front plate 4 and the radio wave passage wall 10 in the above embodiment exhibits the same effect as the parallel flat plate described above. Therefore, the high frequency waves existing in various modes in the heating chamber 2 are also transferred to the passage 10a.
After passing, it becomes a constant parallel plate mode. In addition, the above passage 10
Since the fundamental frequency of the high frequency oscillated from the high frequency heating device (not shown) in the above embodiment is 2450 MHz, the length of a in the radio wave leakage direction (Z direction in FIG. 2) is approximately 114 times 3 cm of the wavelength. And so. Furthermore, in this embodiment, the arrangement interval 1 of the dielectric resonators 12 is 30? , and the gap G between the main body front plate 4 and the door frame flat part 8a when the door is opened is 1.
0.5T! It was set as Rln. The leakage radio wave in the parallel plate mode has a magnetic field that coincides with the side direction of the circumferential groove 9, that is, the X direction in FIG.

Therefore, the leakage radio waves are effectively coupled resonantly with the dielectric resonator 12 and are greatly attenuated. As is clear from the above explanation, the radio wave leakage prevention structure of the high frequency heating device of the present invention can effectively cause leakage radio waves to resonate with the dielectric resonator arranged within the structure, so it is sufficient to prevent radio wave leakage. effect, and its size is also reduced.

In the above embodiment, the radio wave leakage prevention structure is placed on the door side, but the effect is the same even if the structure is placed on the main body side.

[Brief explanation of the drawing]

FIG. 1 is an enlarged cross-sectional view of the main part of an embodiment of the present invention, FIG. 2 is a perspective view of the main part of the same embodiment, FIG. 3 is a perspective view showing the resonance state of a dielectric resonator, and FIG. FIG. 7 is a perspective view showing another dielectric resonator in an embodiment of the invention. 1...High frequency heating device main body, 2...Heating chamber, 12...■mode dielectric resonator.

Claims (1)

[Claims] 1. In a high-frequency heating device in which a plurality of TE mode dielectric resonators having a resonance dimension relationship with the leaked radio waves are arranged in the radio wave leakage path around the opening of the heating chamber, when the wavelength of the leaked radio waves is λ, the above radio wave leakage path is At least λ from one end on the heating chamber side
A high-frequency heating device characterized in that two orthogonal surfaces of each of the dielectric resonators are fixed to metal surfaces in the radio wave leakage path separated by a length of /4.