JPS599897A - Radio wave sealing device - 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 The present invention relates to a radio wave seal for a consumer high frequency heating device, commonly called a microwave oven, and to a method for loading a dielectric therein.

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

A generally well-known radio wave sticker is a chalk sticker.

A choke seal is a device that prevents the entrance of the radio wave path from being short-circuited by setting the dimensions from the entrance of the radio wave path to the radio wave resonant groove and the dimensions of the radio wave resonant groove to be a quarter of the wavelength of the high frequency source being used. It becomes equivalent to and performs an ideal radio wave seal function.

Furthermore, it is well known that a dielectric material is loaded in the radio wave resonant groove to reduce the dimensions of the radio wave resonant groove and thereby to make the groove more compact.

In the case of choke seals, it is necessary 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 was a limit to how compact the radio wave seal could be. .

However, when loading a dielectric material, there is a disadvantage that the wavelength compression ratio is affected by the air layer, and the permittivity changes, etc., and the optimal radio wave ring design has been experimentally performed for dielectric loading. However, the design period for the radio wave seal mechanism was time-consuming.The present invention theoretically makes the radio wave seal mechanism more compact by periodically arranging parallel transmission lines whose radio wave paths are partially short-circuited with T-branches. The present invention provides a radio wave sealing device that aims to prevent changes in the permittivity of the dielectric material due to the air layer in this portion by injection molding a method of loading a dielectric material into the T-branch portion. be.

Before explaining the following using drawings, the theoretical design for compacting the radio wave seal mechanism will be described.

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 constructing a microstrip line in which parallel transmission lines are periodically arranged up to the end of the radio wave path. Hereinafter, 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 [01 out of the 3 ports of the T-branch circuit] Note that power is not transmitted between the other two boats with parallel transmission lines arranged periodically by short-circuiting them at certain positions, and it becomes more complicated when parallel transmission lines are arranged periodically in one part of the radio wave path as described above. It exhibits sufficient radio wave sealing performance even in the radio wave propagation direction.

Also, regarding making radio wave stickers more compact.

As seen in conventional choke seals, the impedance at the entrance to the radio wave path is reduced by simply making the length from the entrance to the radio wave path to the radio wave resonant groove and the length of the radio wave resonant groove both 1/4 wavelength (ideal). Instead of using the concept of "short-circuited" (in a short-circuit state), we introduced a method of analyzing a radio wave path system with a constant amount of energy by replacing all radio wave paths with T-branches with impedances and reducing the amount of radio wave leakage itself.

This constant energy analysis method assumes an impedance equal to Z at the end of a radio wave path in which parallel transmission lines are periodically arranged. Introducing this ZL impedance is
The idea is that when radio waves leak into the external space through a radio wave path, energy is consumed due to impedance ZL. The radio wave path must have a certain finite gap, Z
The impedance L always has a certain finite value.

Conventionally, this impedance Zb was considered to be ZL: 0, and the only qualitative way of thinking was to simply reduce the impedance at the entrance of the radio wave path.By the way, based on this constant energy analysis method, the radio wave Reducing the amount of leakage is equivalent to reducing the energy consumed by ZL. Therefore, the characteristics of the T-branch circuit described above are used to reduce the energy consumed by the ZL.

Moreover, according to this constant energy analysis method, we discovered that the distance from the entrance of the radio wave path to the T-branch opening can be smaller than the conventional 1/4 wavelength, thereby reducing the amount of radio wave leakage.
A compact radio wave sealing device with excellent radio wave sealing performance has been made possible.Now, when the dielectric material 8 with a thickness of t in Fig. 1 is inserted into the T-junction 4, some air space 9 will be generated even if the dimensional accuracy is improved. . Accordingly, the dielectric constant of the T-branch portion changes based on the following idea. That is, the dielectric portion and the air layer portion are regarded as a series capacitor and form an equivalent dielectric constant Eeff. Its general formula can be expressed as: Here, h is the T-branch opening dimension,
t is the thickness of the dielectric, d is the thickness of the air layer, and Er is the dielectric constant of the dielectric - Eo is the dielectric constant of the air layer.

Figure 2 shows the dielectric (Er4, 1) t = 2.9
This is data for calculating the dielectric constant from the single wavelength compression ratio by inserting mm into the T-branch (opening size 3.1 mm).

Calculating from the measured value, Be f f = 3.2 is close to Er-5.2 even in the theoretical value.

However, in this method of inserting a dielectric, the dielectric constant changes slightly due to the air layer, which is a troublesome problem when designing a radio wave sealing mechanism.

Therefore, as shown in FIG.
The dielectric material 8 is poured into the T-branch portion 4 and manufactured integrally. As a result, only the dielectric material 8 is formed in the T-branch portion 4 narrowed by the parallel transmission line, and no air layer is formed. Therefore, the T-branch portion 4 can also be theoretically made more compact due to the wavelength compression effect solely due to the dielectric constant of the dielectric.

FIG. 4 shows a radio wave seal portion made by injection molding according to the present invention. From the entrance 6 of the radio wave path 3 to the opening 7'' of the T branch 4, the T
By loading a dielectric material into the branch part, we were able to make this part more compact.

As described above, in the present invention, the radio wave path formed by the heating chamber and the door is periodically arranged with T-branch parallel transmission lines whose ends are short-circuited, and the dimension from the radio wave path entrance to the T-branch opening is less than 1/4 wavelength. A compact radio wave sealing device can be realized by loading a small and T-branched dielectric material by injection molding, and the following effects can be obtained.

(1) Manufacture is easy because there is no change in dielectric constant due to the air layer.

(2) The dielectric material does not fall out.

(3) The radio wave seal mechanism can be designed theoretically and easily, and the development period can be shortened.

(4) No variation occurs in parallel transmission lines.

(5) The strength of the radio wave seal portion can be maintained. (6) The radio wave seal characteristics can be kept stable.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view showing the case where a dielectric is inserted into the T-junction, Figure 2 is actual measurement data showing the isometric permittivity due to the influence of the air layer in Figure 1, and Figure 3 is FIG. 4 is a cross-sectional perspective view of the radio wave seal portion according to the present invention, which shows filling of the T-branch with dielectric material by injection molding according to the present invention. 1... Heating chamber, 2... Door, 3...
...Radio wave path, 4...T branch transmission line, 6
... Radio wave passage entrance, 7 ... T-branch opening, 8 ... Dielectric material. Name of agent: Patent attorney Toshio Nakao and 1 other person 2nd
(T minutes Tenshu p・cho 5ku) 45F Fig. 3 Fig. 4

Claims (1)

[Claims] It has a heating chamber in which the object to be heated is placed and a door that can be opened and closed to take the object in and out. They are arranged periodically, and the dimension from the entrance of the radio wave path to the T-branch opening is smaller than a quarter wavelength, and the T-branch part is loaded with a dielectric material, and the loading method is injection molding. Radio wave seal device 8