JPS6148234B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high frequency heating device, particularly a waveguide device.

Conventional waveguides for microwave ovens and the like rarely have a tapered shape, and are mostly rectangular parallelepiped sheet metal products. This is because tapered waveguides have a complicated shape, so the mold cost is higher than that of general rectangular parallelepiped waveguides, and they have not been adopted due to manufacturing time and costs. However, this tapered waveguide has the characteristic that the height can be lowered, making it possible to downsize the entire device and, by extension, the entire appliance.In recent years, there has been an increasing demand for complex cookers with multiple functions. At the same time, it has been desired to realize a tapered waveguide that is easy to manufacture and safe.

An object of the present invention is to realize a waveguide that is easy to manufacture and inexpensive while maintaining the safety of a tapered waveguide, and to reduce the size and cost of the device.

Another object of the present invention is to create a waveguide in a shape that can be manufactured by simple sheet metal processing without drawing, reducing the burden of mold costs for manufacturing the waveguide, and reducing the cost. It is to be manufactured in

In order to achieve the above object, the present invention has a slit having a width of 1/10 or less of the wavelength of a high frequency wave in the continuous portion of each of the plurality of planes constituting the E plane parallel to the electric field in the tapered waveguide. By providing this slit, it is no longer necessary to use a drawing die to fabricate the tapered waveguide, which greatly simplifies the process and significantly improves mass productivity.

The operating principle of the present invention will be explained based on FIG.

In the figure, a rectangular waveguide 1 with a rectangular cross-sectional shape is shown.
This shows the flow of wall current in TE ₁₀ mode.
The plane perpendicular to the electric field inside the rectangular waveguide 1 that produces this TE ₁₀ mode is called the H-plane 2.
Also, the plane parallel to the electric field is called E-plane 3. The wall current I of this waveguide 1 flows as shown by the arrow. Therefore, in this waveguide 1, even if narrow slits A4 and slits B5 are formed parallel to the wall current I, the internal electric field is not affected at all. Therefore, there is almost no radio wave leakage from these slits A4 and B5. Conversely, the slit C6 and the slit D7 are perpendicular to the wall current I.
affects the internal electric field, so the amount of radio wave leakage becomes extremely large. Therefore, by providing the slits A4 and B5, a rectangular tapered waveguide can be manufactured without using drawing processing such as simple bending or punching.

An embodiment of the present invention will be described below based on the drawings.

FIG. 2 shows a household microwave oven with a heater plate. Two heater plates 9 are provided on the upper part of the main body 8, and can be used for boiling food.
Two control knobs A10 of the main body 8 control and adjust the power of the heater plate 9, respectively. Further, heater heating and high frequency heating in the heating chamber 11 are adjusted by a control knob B12. A front opening of the heating chamber 11 is provided with a door 13 for taking food in and out.

In FIG. 3, a heater plate 9 made of a heat-resistant dielectric material is provided on the upper part of the main body 8, and cooking can be performed using a plate heater 14. An oven heater 1 is installed on the top and bottom of the heating chamber 11.
5 and 16 are provided, and indoor oven heating or browning heating is possible. A heat-resistant heat insulating material 18 is provided around the outside of the wall surface 17 of the heating chamber 11 to prevent heat radiation to the outside.

On the other hand, the high-frequency electromagnetic waves from the magnetron 19 pass through the tapered waveguide 20 to the motor 2.
The rotational force of 1 is transmitted by the belt 22 and is fed into the heating chamber 11 by the rotating rotary antenna 23 .

In FIG. 4, the detailed shape of the tapered waveguide 20 will be explained. The shape of the tapered waveguide 20 is a rectangular waveguide, and has an E plane 24 parallel to the electric field inside the rectangular waveguide and an H plane 25 perpendicular to the electric field. It consists of an E1 surface 26 and rectangular E2 surfaces 27 and E3 surfaces 28 on both sides thereof. Narrow slits 29 and 30 are cut from top to bottom in the continuous portion between the E1 surface 26 and the E2 surface 27 and the continuous portion between the E1 surface 26 and the E3 surface 28, respectively. Wall current I of tapered waveguide 20
flows along the wall as shown by the arrow. At this time
All E on E1 side 26, E2 side 27 and E3 side 28
Since only the wall current I parallel to the slits 29, 30 flows in the plane, the slits 29, 30
It has been confirmed that the slits 30 have no effect on the internal electric field, and that almost no leakage of radio waves from the slits 29 and 30 occurs.

The width of the slits 29 and 30 is the same as that of the waveguide 2.
Although it depends on the magnitude of 0, in commonly used home and commercial microwave ovens, radio wave leakage can be suppressed to a level that does not cause any actual damage if the wavelength is one-tenth or less of the wavelength of high-frequency electromagnetic waves. If it is desirably 1/20th or less (approximately 6 mm), the leakage is normally 0.5 mW or less and there is no problem at all.

In this way, a slit 2 is formed in the tapered waveguide 20.
9 and 30, in sheet metal production of the tapered waveguide 20, there is no need for an expensive drawing die that takes a long time to manufacture, and a relatively inexpensive outline cutting die and bending die can be used. It can be produced by just Therefore, mass production can be carried out in a shorter period of time and at lower cost.

If an adhesive tape-like substance that prevents air flow is applied to the slits 29 and 30 described above, not only will foreign matter such as dirt and dust not enter the tapered waveguide 20, but the waveguide 20 Surrounding hot air does not flow directly to the antenna 31 of the magnetron 19, allowing stable operation of the magnetron 19 and improving durability.

As described above, according to the present invention, the following effects can be obtained.

1 By providing a slit in the tapered waveguide, sheet metal processing is facilitated, processing can be performed without using a drawing die, and manufacturing costs including die costs can be significantly reduced. .

2. Not only is manufacturing easier, but the slits are carved in the E plane parallel to the electric field in the same direction as the wall current flows, so there is no negative effect on the high frequencies in the waveguide, and radio wave leakage does not cause any real damage. can be kept within a range that does not occur.

3 It has become easier to use tapered waveguides, so if you want to lower the height of the device, you can make it more compact by using a tapered waveguide, which has a very large effect on complex cooking devices, etc. Become.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the operating principle of the present invention, Fig. 2 is an external perspective view of a microwave oven with an electric stove which is an embodiment of the present invention, Fig. 3 is a front sectional view of the microwave oven, and Fig. 4 is the same. It is an external perspective view of the taper-shaped waveguide of a range. 11... Heating chamber, 19... Magnetron (high frequency oscillator), 20... Tapered waveguide, 24,2
6, 27, 28...E side, 25...H side, 29,
30...Slit, I...Wall current.

Claims (1)

[Claims of Claims] 1. A heating chamber for storing food, a high-frequency oscillator for feeding high-frequency power into the heating chamber, and a tapered waveguide having a rectangular cross section for coupling the high-frequency oscillator and the heating chamber. , the tapered waveguide has an H plane perpendicular to the electric field in the tapered waveguide and an E plane parallel to the electric field, and the E plane has a plurality of consecutive surfaces including at least one tapered surface. The high frequency heating device further comprises forming a slit in the continuous portion between the surfaces in the same direction as the flow direction of the generated wall current and having a width of one-tenth or less of the wavelength of the high frequency wave. 2. The high frequency heating device according to claim 1, wherein the slit is closed with a tape-like substance having adhesive properties.