JPS6325477B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a radio wave seal for a consumer high frequency heating device, commonly called a microwave oven.

Microwave ovens are widely used to heat and cook objects using high-frequency energy, but radio waves leak to the outside through the gap between the heating chamber and the door (hereinafter referred to as the radio wave passage). .
In recent years, society's awareness of the effects of radio wave leakage on the human body has increased, and in order to suppress the amount of radio wave leakage below an acceptable range, radio wave passages are equipped with a radio wave leakage prevention mechanism (hereinafter referred to as a radio wave seal). There is.

A commonly known radio wave seal is the Chiyoke seal.

The radio wave seal is a short-circuit at the entrance of the radio wave passage by taking the quarter wavelength of the high frequency source that uses both the dimension from the entrance of the radio wave passage to the radio wave resonant groove and the length of the radio wave resonant groove. and performs an ideal radio wave seal function.

In addition, recent microwave ovens use a stirrer fan or the like to disturb the electric field in order to improve heating efficiency, so the chiyoke seal alone cannot perform the radio wave sealing function in the complicated direction of radio wave propagation. Therefore, there are also radio wave seals that have slits with a periodic structure in the radio wave passage or radio wave resonance groove to restrict the direction of radio wave propagation.

Furthermore, it is well known that a dielectric material is loaded in the radio wave resonant groove to reduce the length of the radio wave resonant groove and thereby to achieve compactness.

As mentioned above, it is necessary for conventional radio seals that the dimensions from the entrance of the radio wave passage to the radio wave resonant groove and the dimensions of the radio wave resonant groove are both 1/4 wavelength, and there is a natural limit to how compact the radio wave seal can be made. .

In addition, when slits are made in the radio wave passage, the radio wave seal part including the slit is covered with a low dielectric cover from the viewpoint of preventing food residue from adhering to it and aesthetics. The only thing that happens is the thickness, which makes it easier for radio waves to pass through. In addition, the design of radio wave seals also has the drawback of requiring a long development period due to qualitative experiments.

The present invention provides a structure in which a part of the radio wave path is short-circuited at a T-branch, a parallel plate line is used from the entrance of the radio wave path to the T-branch opening, and the T-branch part has a configuration in which parallel transmission lines are periodically arranged, or a T-branch. The parallel transmission lines on the heating chamber side of the opposing parallel transmission lines are flattened to form a cyclostrip line, and the microstrip line is arranged periodically from the T-branch opening to the end of the radio wave path. The present invention provides a radio wave sealing device for a high frequency heating device, which aims to make the radio wave sealing mechanism more compact and improve the radio wave sealing performance by configuring it with a loop line.

Below, before explaining the present invention using drawings, the characteristics of the present invention will be described. One of the three characteristics of the T-branch circuit is that "One port out of the three ports of the T-branch circuit By short-circuiting at an appropriate location, no power is transmitted between the other two ports.
By periodically arranging parallel transmission lines in the section, sufficient radio wave sealing performance can be achieved even in complicated radio wave propagation directions.

In addition, when making radio wave stickers more compact,
The impedance at the entrance of the radio wave passage can be reduced by simply making the length from the entrance of the radio wave passage to the radio wave resonant groove and the length of the radio wave resonance groove both 1/4 wavelength (ideally The idea is not to introduce a method of quantitatively analyzing the energy of a radio wave path system that reduces the amount of radio wave leakage itself by replacing all radio wave paths with T-branches with impedance.

This energy quantitative analysis method assumes an impedance Z _L at the end of a radio wave path in which parallel transmission lines are periodically arranged. The reason for introducing this impedance Z _L is the idea that when radio waves leak to the outside space through the radio wave path, energy is consumed at the impedance Z _L. Since the radio wave path has a certain finite gap, the impedance Z _L necessarily has a certain finite value. Conventionally, this impedance Z _L is Z _L = 0
I was only able to think qualitatively about reducing the impedance at the entrance to the radio wave path.

By the way, reducing the amount of radio wave leakage based on this energy quantitative analysis method is equivalent to reducing the energy consumed by Z _L. Therefore, the characteristics of the T-branch circuit as described above are used to reduce the energy consumed by Z _L.

Moreover, according to this energy quantitative analysis method,
We also discovered that the amount of radio wave leakage can be reduced by having a wavelength smaller than the conventional one-quarter wavelength from the entrance of the radio wave passage to the T-branch opening, making it possible to create a compact radio wave sealing device with excellent radio wave sealing performance.

Furthermore, in this energy quantitative analysis method, the radio wave path is considered as a parallel transmission line, but from the entrance of the radio wave path
Parallel plate line configuration up to the branch opening, T
It was experimentally confirmed that the amount of radio wave leakage does not change even in a configuration in which a microstrip line is formed by flattening the parallel transmission lines on the heating chamber side of the parallel transmission lines facing each other in the branch section. This means that
In other words, from the radio channel entrance to the T-branch opening,
Since it is composed of parallel flat plates, there is no need for a low dielectric cover, and there is no need to consider the thickness of the cover for the gap between the heating chamber and the door, and the amount of transmitted radio waves can be reduced accordingly.

This will be explained below using the drawings.

FIG. 1 shows a conventional microwave oven slit York seal. If the radio waves propagate to the outside from the entrance 6 of the radio wave passage 5 formed by the heating chamber main body wall 2 and door 3, in the case of a York seal,
By making the dimensions from the entrance of the radio wave passage to the radio wave resonance groove entrance 7 and the radio wave resonance groove 8 both 1/4 wavelength, an ideal radio wave seal is constructed, and by arranging the slits periodically as shown in 9. It has excellent radio wave sealing properties even for complex radio wave propagation.

FIG. 2 shows a radio wave seal portion showing an embodiment of the present invention. In FIG. 2, the dielectric material is omitted. Based on the energy quantitative analysis method, the distance from the radio wave path entrance 6' to the T-branch entrance 10 is 10 mm, which is shorter than a quarter wavelength, and is composed of parallel flat plates.

The T-branch portion and the T-branch portion are parallel transmission lines 11
are arranged periodically, and the transmission line from the T-branch opening 10 to the vicinity of the terminal end 4' of the radio wave path 5' is partially connected with a 3 mm transmission line in order to prevent variations.

FIG. 3 is a sectional view of the radio wave seal portion when a dielectric is loaded. A dielectric material 14 is loaded from the T-branch opening 10 to the T-branch termination 12 and from the T-branch opening 10 to the radio wave path termination 4'.

In the above configuration, the radio waves that are about to leak to the outside through the radio wave path 5' are 6'-
Furthermore, the area from the radio wave passage entrance 6' to the T-branch opening 10 is a parallel plate configuration, and the heating chamber wall surface 2' and the door wall surface 3' form a close contact state and try to transmit. You can narrow down the amount of radio waves.

And from the radio wave passage entrance 6' to the T branch opening 10
It was previously confirmed that radio wave sealing performance was better when the wavelength was smaller than a quarter wavelength, and by loading a dielectric material into the T-branch, a compact radio wave seal was made possible. Furthermore, even for complex radio wave propagation, since the parallel transmission lines are arranged periodically, the propagation in the arrangement direction is restricted.

Note that this is not limited to one embodiment of the present invention, and as another embodiment, as shown in FIG.
It was experimentally confirmed that the radio wave sealing performance did not change even if the heating chamber side of the parallel transmission lines facing each other at the branch part was configured as a flat plate line.

As described above, the present invention provides a part of the radio wave path with a T-branch portion, and periodically arranges the T-branch portion and the T-branch opening to the end of the radio wave path with parallel transmission lines, and from the entrance of the radio wave path to the T-branch opening is a parallel flat plate. The line configuration enables a compact radio wave seal and provides the following effects.

(1) The radio wave seal mechanism can be designed theoretically instead of designing the mechanism for an experimental radio wave seal as in the past, and the design period can be shortened.

(2) Compact radio wave seals are possible.

(3) Since the parallel transmission lines near the end of the radio wave path are continuous, variations in the transmission lines are eliminated.

(4) It is easier to manufacture than configuring all radio wave paths as parallel transmission lines.

(5) A door with a smart appearance can be created, and it can be made lighter by reducing the amount of materials used.

(6) Part of the dielectric cover can be reduced.

(7) Mechanical strength of the transmission line near the end of the radio wave path;
And since the dimensional accuracy of manufacturing can be maintained, the radio wave seal characteristics are stable.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional perspective view showing a conventional slit-formed chiyoke seal, Fig. 2 is a cross-sectional perspective view showing an embodiment of the present invention, Fig. 3 is a cross-sectional view of a radio wave seal mechanism loaded with a dielectric, and Fig. 4. FIG. 2 is a cross-sectional perspective view of another embodiment of the present invention. 1, 1'...Heating chamber, 3, 3'...Door, 5,
5'...Radio wave passage, 10...T branch opening, 12
...T-branch end, 4,4'...Radio wave path end, 1
1...Parallel transmission line, 13...Parallel plate line, 1
4...Dielectric material.

Claims (1)

[Scope of Claims] 1. A T-branch having a heating chamber into which an object to be heated is placed and a door that can be opened and closed through which the object to be heated is taken in and taken out, the radio wave path formed by the heating chamber and the door being short-circuited at the end. From the opening of the T-branch path to the end of the short-circuit surface and from the T-branch opening to the end of the radio wave path, a periodic transmission line configuration is taken in the direction around the door, and from the entrance of the radio wave path to the end of the short circuit surface, The radio wave seal device has a parallel plate line configuration up to the branch opening, and its dimensions are smaller than a quarter wavelength. 2. The radio wave sealing device according to claim 1, wherein a dielectric material is loaded in the radio wave path constituting the T-branch.