JPS628917B2 - - 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 in which a TE mode dielectric resonator is arranged in a radio wave leakage path around an opening of a heating chamber.

In recent years, in the field of microwave communication technology, it has been proposed to place a well-known dielectric resonator in the radio wave leakage path around the opening of the heating chamber in place of the conventional chiyoke groove to suppress radio wave leakage from the heating chamber. The reason for this is that if the dielectric resonator is arranged in a door, for example, it is expected that the door will be thinner than a door in which a conventional chiyoke groove is arranged.

However, in the field of microwave communication technology, dielectric resonators are mostly developed and applied as band-pass filters and band-stop filters, so even if they are used to suppress radio waves, the frequency band of radio waves that can be suppressed is extremely narrow.

However, in high-frequency heating equipment, the fundamental wave oscillated in the heating chamber is 2450MHz, and the fundamental wave varies up to ±50MHz depending on the load (starvation fan, turntable, heated object, etc.) in the heating chamber.
Change. Therefore, even if a dielectric resonator is arranged in the radio wave leakage path of the high frequency heating device to suppress the leakage radio waves, a sufficient effect cannot be obtained.

The present invention has been made in view of the above points.

FIG. 1 shows an embodiment of the present invention, in which 1 is a high-frequency heating device main body, 2 is arranged inside the main body 1, and an opening 3
4 is a metal main body front plate arranged around the opening 34 of the heating chamber 2; 5 is pivotally supported on one side of the front plate 4, and is rotatable in the direction of the arrow in the figure. This is a door that opens and closes the opening 3, and the door 5 is fixed to a metal door frame 6 provided along the side of the front plate 44 and four inner edges of the door frame 6 when the door is closed, and is fixed to the heating chamber 2. It consists of a punching plate 7 whose interior can be seen through. The door frame 6 has a frame-shaped flat portion 6a whose surface faces parallel to the periphery of the front plate 44 when the door is closed.
, a bent part 6b formed by bending the outer edge of the flat part 6a perpendicularly to the main body 1 side, and an inclined part 6c formed by bending the inner edge of the flat part 6a at an angle in the bending direction of the bent part 6b, Flat part 6a, bent part 6b
and the front plate 44 from the inclined part 6c when the door is closed.
A circumferential groove 8 is formed along the side. Reference numeral 9 indicates the end of the bent portion 6b and the inclined portion 6 to cover the periphery of the circumferential groove 8.
A low dielectric cover 10 is fixed to the c end, and 10 is a TE mode dielectric resonator arranged at regular intervals within the four sides of the circumferential groove 8, and the dielectric resonator 10 is metallized on one side. The metallized surface is fixed to the surface of the flat portion 6a by brazing.

The present inventor has proposed an arrangement structure of the TE mode dielectric resonator in the high-frequency heating device shown in FIG. We conducted various experiments in an attempt to obtain this.

FIG. 2 shows one experimental apparatus used by the present inventor, where 11 is a first metal flat plate, and 12 is the metal flat plate 1.
This is a TE mode dielectric resonator brazed on the surface of 1 at regular intervals 1. Further, there is a second metal flat plate (not shown) that faces parallel to the surface of the first metal flat plate, and forms a radio wave path together with the first metal flat plate 11.

In the apparatus shown in FIG. 2, a radio wave with a frequency f ₀ is oscillated into the apparatus from the direction of the arrow in the figure, and the frequency characteristics of the dielectric resonators 12 are examined by changing the interval l between the dielectric resonators 12. Ta. As a result, when only one dielectric resonator 12 was arranged in the parallel plate, the frequency characteristics were steep as shown by the solid line A in FIG. 3, but as shown in FIG. When a plurality of them were arranged, a gentle frequency characteristic was obtained as shown by the dotted line B in FIG. Furthermore, the fact that the frequency characteristics become gentler is the same as that the frequency band B at a certain degree of attenuation α is also broadened.

However, simply arranging the dielectric resonators 12 at regular intervals l does not provide the above frequency characteristics. In other words _, according to experiments conducted by the present inventor, when the interval becomes more than a certain value l ₁ , the frequency characteristic curve becomes steep as shown in FIG. 4
As shown in the figure, the resonance frequency band B ₃ at the damping degree α
deviates from the oscillation frequency f ₀ . Therefore, if l ₁ or more and l ₂ or less, desired frequency characteristics cannot be obtained.

Here, the frequency of the high frequency oscillated into the heating chamber of the high frequency heating device is 2450MHz, and at this time l ₁ , l ₂
It was confirmed through experiments by the present inventor that the values of are 30 mm and 15 mm, respectively. As an example, in the device shown in Figure 2, the relative dielectric constant is 90, and its dimensions are 11.5 mm in the radio wave propagation direction, 7.5 mm in the parallel plate spacing direction, and 7.5 mm in the dielectric resonator arrangement direction. length 6mm
A TE mode dielectric resonator whose main component is barium titanate is used, and the dielectric resonator is
The above parallel plate spacing G is adjusted so that it resonates at 2450MHz.
FIG. 5 shows the relationship between the spacing l between the dielectric resonators and the resonant frequency bandwidth B at an attenuation of -10 dB when the dielectric resonator is set to 10.5 mm. In addition, the above attenuation degree -
10 dB was used as a standard because it is comparable to the degree of attenuation of conventional chiyoke grooves. Further, the above-mentioned attenuation degree is a relative value with reference to when there is no load at all in the cooking chamber.

As is clear from FIG. 5, when the distance 1 becomes 30 mm or more, the resonance frequency bandwidth B rapidly decreases. Furthermore, when the intermediate width l in Fig. 5 is 10 mm, the resonance frequency bandwidth B is quite wide, but this appears to be shifted from the oscillation frequency (2450MHz) as shown in Fig. 4. It has no effect.

It is also known that the frequency characteristics of a dielectric resonator become gentler as the surface of the dielectric resonator that couples with the magnetic field of the radio wave is wider. In other words, in a dielectric resonator that couples with radio waves of the same frequency, the lower the dielectric constant, the larger the resonance dimension that resonates with the radio wave, and the larger the surface area of the dielectric resonator that couples with the magnetic field of the radio wave, which improves the frequency characteristics. improves.

From the above points, in this example, the relative dielectric constant εr is 36, the length in the vertical direction (X direction in the figure) of the front plate 4 in FIG. 25 TE mode dielectric resonators whose main component is barium titanate with a length of 9.3 mm in the Y direction and 17.6 mm in the radio wave leakage direction (Z direction in the figure).
Arranged at intervals of mm, the front plate 4 and the flat part 6 when the door is closed.
The distance from a was set to 14 mm.

At this time, the attenuation frequency bandwidth at the leakage radio wave attenuation level of −10 dB is centered around 2450 MHz.
It is about 100MHz.

As is clear from the above, according to the present invention, leakage radio waves can be effectively suppressed by using a TE mode dielectric resonator even if the frequency of the leakage radio waves changes depending on the load condition in the cooking chamber. In this embodiment, the dielectric resonator is placed on the door side, but the same effect can be obtained even if the dielectric resonator is placed on the main body side.

[Brief explanation of the drawing]

FIG. 1 is an enlarged cross-sectional view of essential parts of an embodiment of the present invention;
Figure 2 is a plan view of the experimental equipment used in the present invention;
4 is a graph showing the relationship between frequency and attenuation degree, and FIG. 5 is a graph showing the relationship between dielectric resonator spacing and resonance frequency bandwidth. 2... Heating chamber, 10... TE mode dielectric resonator.

Claims (1)

[Claims] 1. In a high-frequency heating device in which a plurality of dielectric resonators are arranged in a radio wave leakage path around the heating chamber opening,
A high-frequency heating device characterized in that TE mode dielectric resonators are arranged along the periphery of the opening 4 at intervals of 15 to 30 mm.