JPH0135480B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to the structure of a radio wave leakage attenuation groove around the opening of a heating chamber of a high-frequency heating device equipped with a heating chamber and a door.

Conventional technology In conventional high-frequency heating devices, the attenuation groove for preventing radio wave leakage around the opening of the heating chamber is either built into the door or installed in a sash that opposes the outer circumferential surface of the door, as disclosed in Japanese Patent Application Laid-Open No. 113834/1983. The sash was equipped with a radio wave attenuation groove.

Problems to be Solved by the Invention However, in such a high-frequency heating device in which a radio wave attenuation groove is included in the door, the plate surrounding the opening at the front of the heating chamber becomes large due to the radio wave attenuation groove, making it difficult to make the device more compact. There were limits to what could be done.

Furthermore, in the high-frequency heating device as disclosed in Japanese Patent Application Laid-open No. 50-113834, food particles and the like scatter and adhere to the opening of the radio wave attenuation groove, causing sparks and making cleaning difficult. . In addition, since the slit is provided in one space, the long side of the slit needs to be about 1/4 wavelength of the radio wave used, which not only limits the dimensions of the sash design, but also reduces the thickness of the door itself. This required a wavelength of about 1/4 of the radio waves used, which was a problem in making compact equipment and was not economical.

The present invention solves these conventional problems, and makes effective use of the sash (decorative board) around the door, which is necessary for design, to create a compact device, and also to prevent radio waves leaking when the door is opened. The purpose of the present invention is to provide a structure that has a stable leakage prevention effect.

Means for Solving the Problems In order to achieve the above object, the high frequency heating device of the present invention includes a heating chamber, a door provided at the opening of the heating chamber so as to be openable and closable, and a peripheral plate of the opening of the heating chamber. , a metal decorative plate fixed to the front surface of the peripheral plate so as to form a space with a spatial dimension of 1/4 wavelength or less from the peripheral plate, and a space formed by the peripheral plate and the decorative plate. a partition fitting that partitions the radio wave attenuation groove into two spaces; the decorative board protrudes from the peripheral board so as to be approximately at the same height as the door when closed; An opening is formed in a portion that is perpendicular to the plate and faces the door when closed, and the partition fitting has a U-shaped cross section with both ends fixed to the peripheral plate, and has periodic slits. and the slit surface faces at least the opening of the radio wave attenuation groove.

Effect Since the heating cooker of the present invention has the above-described configuration, the sash (decorative board) required for design is effectively used, and the radio wave attenuation groove, which is a space that can be formed by the sash (decorative board), is connected to the partition metal fitting. By dividing the space into two spaces with This has the effect that radio wave leakage can be prevented without any modification, and the radio wave leakage prevention effect can be expected without increasing the external dimensions of the device.

Embodiment Hereinafter, an embodiment of the present invention will be described based on the drawings.

As shown in FIG. 1 and subsequent figures, a door 2 is provided at the front opening of the heating chamber 1 so as to be openable and closable.

An operation panel 4 is provided near the door 2 on the front surface of the main body 3, and an upper sash 5, a lower sash 6, and a left sash 7 are provided around the door 2.

Inside the heating chamber 1, there are a magnetron 8 that oscillates and supplies radio waves, an upper heater 9, a lower heater 10, a table 12 for placing food 11, and the like.

Next, the radio wave leakage groove, which is the gist of the present invention, will be described.

In the upper sash 5, a decorative plate 15 and a partition fitting 16 having a U-shaped cross section are attached to the upper end portion 14 of the front opening peripheral plate 13 of the heating chamber 1. Then, a radio wave attenuation groove is formed in the decorative board 15, and the space is partitioned into two spaces by the partition fitting 16.
7 is formed.

Thickness of the space formed by the partition fittings 16 (horizontal distance L from the opening peripheral plate 13 in FIG. 3)
is set below one-quarter wavelength of the radio waves used. (This is a result obtained experimentally.) Furthermore, openings C and D for leakage radio waves to enter are provided in the two spaces (sections A and B in FIG. 3). A slit is provided in the opening D of the space B formed by the partition fitting 16.

The radio waves leaking from the heating chamber 1 are subject to the following regulations before they leak outside. That is, if we consider the transmission system by dividing it into the following regions, it appears that these transmission systems constitute two E branch circuits by connecting parallel plates with different characteristic impedances and propagation constants in series. If the spatial dimension from the peripheral plate of the opening of the partitioning metal fitting 16 that forms the partitioning part 17 is kept within a dimension of 1/4 wavelength or less, the partitioning part 17 will generate higher-order modes, and the high band frequency with respect to the fundamental frequency will be reduced. Due to its blocking characteristics, it can be used alone as a damping groove with a large shielding effect. (This is an experimental result.) Note that the generated higher-order modes are drastically reduced in a short period, and the higher-order modes generated in the area outside this groove are attenuated. It's a place.

A space that is a damping groove provided in two flat plates, the flat plate of the door 2 and the flat plate of the front opening peripheral plate 13, and the part of the sash 5 that extends at right angles to face the front opening peripheral plate 13. This is a flat plate transmission circuit consisting of a space "A" and a space "B" and having a discontinuous portion at an opening D between the space "A" and the space "B" which are damping grooves. When the radio waves that have passed through the region reach the region, the electric field is disturbed due to the discontinuity and a harmonic mode is generated. This mode applies to door 2 and front opening peripheral plate 13.
The smaller the gap, the more rapid the attenuation. In addition, for the fundamental wave of leakage radio waves that passed through the area, since the area part has two grooves (space "A" and space "B"), two stages of filters with band rejection characteristics are connected. It can be considered as a thing.

That is, if the area is considered as an E branch circuit, its equivalent circuit will be as shown in FIG. In the figure, numerals 2 and 3 indicate the tip short-circuit impedances viewed from the entrance of the groove, respectively. Each distribution constant is uniquely determined by the geometric dimensions, and radio waves passing through this constant pass through the area and are radiated into space (characteristic impedance 1). In order to reduce leakage radio waves, the geometric dimensions should be selected so that the impedance of the entire system from the oven side is as small as possible in the frequency range where it can change. For example, a household microwave oven (reference frequency 2450MHz, 500W output)
If 275 c.c. of water is required, the dimensions were chosen using a simple experimental approach: the overlapping dimension of the opposing flat plates in the area was 30 mm;
WB=20mm, WA=5mm, LB=25mm, LA=5
mm, in _the X ₁ =
When the gap between the door 2 and the main body (front opening peripheral plate 13) is 2 mm, measurements are taken at a location 50 mm away from the microwave oven main body, where radio wave leakage is greatest.
It can be reduced to 0.4m W/cm ² or less.

Next, the effect of the partition fitting 16 on preventing leakage of radio waves will be described.

Since the partition fitting 16 has a slit groove as shown in FIG. 5 in the D portion, the traveling direction of the radio wave is regulated by the slit groove in the X direction (direction perpendicular to the paper surface).

When the radio waves leaking from the gap between the heating chamber 1, the opening, and the door 2 pass through the area, it acts as a type of bypass capacitor with a capacitance corresponding to the planar contact between the door 2 and the plate surrounding the opening. Therefore, among the radio wave traveling directions X, Y, and Z, the Z direction is the door 2.
and is regulated by the opening surrounding plate. Moreover, this planar contact portion is considered to be a parallel plate line. Since the capacitance of this parallel plate line is proportional to the gap of the parallel plates, the capacitance 4 becomes larger as the gap of the planar contact portion is smaller, and the radio wave sealing effect increases. Then, after passing through the area, enter the area. Since the radio waves that entered space B in the area have been regulated in the Z direction in the area, they are approximately in the X and Y directions. At that time, in the slit part of dimension X ₁ ,
The radio wave enters in the Y direction, and also penetrates space B and enters space A. In this case, the plane part of the _X2 portion and the outer peripheral part of the door 2 are considered to be a parallel plate track. This parallel plate line is similar to the area capacity 4, and is proportional to the distance between the plane part of _the This increases the radio wave seal effect. In addition, the radio waves in the X direction of the slit part with dimension X ₁ and _the capacitances 5, 6, 7,
8 etc., it can be expressed as a resonant circuit 9, 10 of capacitance and inductance. Also, the dimensions
At the end face where _{the plane part of dimension X 2 transitions} to _the slit part of dimension
14 becomes larger, which means that even if the inductance components 11 and 12 are made smaller by that amount, resonance can be achieved at a specific frequency.

In other words, the presence of the slit groove in the partition fitting 16 that forms the partition between the space "A" and the space "B" provides a sufficient effect of preventing radio wave leakage even if the door 2 does not have a chiyoke groove. .

The present invention is characterized in that the area where the door 2 is installed is a radio wave transmission system formed by a sash 5 extending from the main body at right angles to the periphery of the door 2. In other words, when the radio waves that cannot be blocked by the filter reach the curved portion 18 of the region, this curve still has a disturbing effect on the radio waves, and the generation of higher-order modes is observed here as well. The amount of radio waves leaking to the door will be even smaller, and since there are attenuation grooves and a decorative plate 15 installed around the door 2,
As the door 2 is opened, the damping effect becomes even better. Also, as another point, since the attenuation groove is formed in the decorative plate 15 which has a design meaning, the opening needs to be covered with a chiyoke cover 19 made of a polymeric material with low dielectric loss. . Further, the shape and size of the upper sash 5 are influenced by the design, but this can be handled by changing the thickness, material, etc. of the yoke cover. Furthermore, if this is insufficient, it is also possible to construct it with a radio wave absorber.

Next, the mounting configuration will be described.

A partition fitting 16 is inserted into the hole 20 at the tip of the decorative board 15.
Insert the L-shaped protrusion 21 at the tip of the partition fitting 16
Slide the hook-shaped L-shaped portion 22 at the tip of the heating chamber into the hole 23 of the heating chamber opening peripheral plate 13.

Furthermore, the cheese cover 19 is slid in from the side, and the heating chamber opening peripheral plate 13
are fastened together with a screw 24 at the upper end.

5 and 6 show a state in which slits are made in the partition portion.

Effects of the Invention As explained above, the present invention can provide blocking characteristics for a wide band of frequencies, so it has stable blocking ability even when the oscillation frequency fluctuates.

In addition, it has a large radio wave disturbance effect, and because it is installed around the door at right angles to the main body (heating chamber opening peripheral plate), it exhibits a stable shielding effect against changes in the gap size between the door and the main body. Therefore, it is easy to take measures against leakage when the door is opened, and since there are no moving parts in the shielding mechanism, it is stable even when used for a long time. Furthermore, foreign objects such as spoons and forks are difficult to get caught in, and even if they are caught, it is difficult to deform.

In addition, since it is constructed with a sash that is necessary for design, new damping grooves can be added to the door as in Japanese Patent Application Laid-open No. 48-10648, and heating chamber openings can be added as in Japanese Utility Model Publication No. 55-4239. It can be installed in the surrounding area, or
The effect of the damping groove is increased with a simpler structure compared to the one-space groove structure having an opening surface and a slit on the facing surface of the outer periphery of the door, as disclosed in Japanese Patent No. 113834.
The combined use of a radio wave absorber has great economic effects, such as giving greater freedom in design.

[Brief explanation of drawings]

Fig. 1 is a perspective view of a high-frequency heating device showing an embodiment of the present invention with the door open, Fig. 2 is a longitudinal sectional view of the same, and Figs. 3 and 4 are enlarged sectional views of section A in Fig. 2. , FIGS. 5 and 6 are perspective views of a partition fitting with slits formed therein, FIG. 7 is an exploded perspective view of a decorative board, a partition fitting, and a tie-yoke cover, and FIG. 8 is an equivalent circuit diagram of a tie-yoke groove. 1...Heating chamber, 2...Door, 3...Main body, 5...
... Upper sash, 15 ... Decorative board, 16 ... Partition fittings, 17 ... Partition part, 18 ... Bend part, 19 ...
Chiyoke cover.

Claims (1)

[Scope of Claims] 1. A heating chamber, a door provided at the opening of the heating chamber so as to be openable and closable, a peripheral plate of the opening of the heating chamber, and a front surface of the peripheral plate having a spatial dimension larger than the peripheral plate. 1/
A metal decorative plate fixed to form a space of four wavelengths or less, and a partition fitting that partitions a radio wave attenuation groove, which is a space formed by the peripheral plate and the decorative plate, into two spaces. , the decorative board protrudes from the peripheral board so as to be approximately at the same height as the door when closed, and a portion of the decorative board is perpendicular to the peripheral board and faces the door when closed. forms an opening, the partition fitting has a substantially U-shaped cross section with both ends fixed to the peripheral plate, and periodically forms slits,
The high frequency heating device is configured such that the slit surface faces at least the opening of the radio wave attenuation groove. 2. The high-frequency heating device according to claim 1, wherein the opening of the radio wave attenuation groove is made of a polymer material with low dielectric loss or a radio wave absorber.