JPH01118028A - Microwave oven - Google Patents

Abstract

PURPOSE:To enable an effective radiowave leak preventing capacity even when the total width of first, second, and third, grooves is reduced to one fourth of a fundamental wavelength and to reduce the size of a radiowave leak preventing means part, by a method wherein the second groove formed in a depth shallower than those of the first and third grooves is formed in the midway between the first and third grooves having depth being one fourth of a fundamental wavelength of high frequency. CONSTITUTION:A first groove 11, a second groove 12 located in the intermediate, and a third groove 13, which are opened on the inner wall surface side of a door body 2, are formed in a peripheral part 2a of the door body 2 in a manner to be positioned adjacent to and in juxtaposition with each other. The first groove 11 and the third groove 13 are formed in a depth l1 being a fundamental wavelength (lambda)/4 of high frequency and the same depth, and the second groove 12 is formed in a depth l2 being as shallow as approximately 85% of the depths l1 of the first and third grooves 11 and 13. Through the action of the intermediate second groove 12, effective radiowave leakage preventing capacity is provided even if the total groove width of the first, second, and third grooves 11, 12, and 13 is set to lambda/4 or less to reduce the size of a radiowave leakage preventing means part, and since the oven can be of a ferriteless construction, its cost can be reduced.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a microwave oven, and particularly to the structure of a radio wave leakage prevention means portion.

(Prior Art) Generally, a microwave oven is provided with a heating chamber within a main body 1, as shown in FIG. 3, and a door body 2 that can be opened and closed is provided at the opening of the heating chamber. An output antenna of a magnetron (not shown) that excavates high-frequency waves faces the heating chamber, and the high-frequency waves are irradiated into the heating chamber by this magnetron. As the high frequency, 2450 MHz microwave is usually used. The peripheral edge 2a of the door body 2 is provided with radio wave leakage prevention means for the high frequency waves.

FIG. 4 shows a first conventional example of a radio wave leakage prevention means portion in such a microwave oven. In the same figure, 3
is a heating chamber, 4 is an open (heating chamber) front plate, and when the fundamental wavelength of the high frequency wave irradiated to the heating chamber 3 is λ, λ is applied to the peripheral edge 2a of the door 2 facing the oven front plate 4. A single choke groove 5 having a groove width of /4 is formed. The frequency of the high frequency is usually 2450 MHz as mentioned above.
Therefore, the fundamental wavelength is λ-122 mm, and therefore λ/4h30.5 mm. Further, a ferrite 7 is supported on the choke force bar 6, and the combination of the choke groove 5 and the ferrite door constitutes radio wave leakage prevention means.

In this way, in the first conventional example, since the single choke groove 5 cannot sufficiently satisfy the safety standards against radio wave leakage, the ferrite 7 is combined with the single choke groove 5 to constitute the radio wave leakage prevention means. .

However, if the ferrite 7 is used in common, the structure of the relatively expensive ferrite and the door body 2 becomes complicated and the number of manufacturing steps increases, resulting in high costs.

Figure 5 shows a second ferrite-less structure to deal with this problem.
Conventional examples are shown (Japanese Patent Publications No. 50-34777 and 50-34780).

In this conventional example, a first groove 8 and a second groove 9 having a depth of λ/4 are arranged side by side at a required interval so as to open toward the inner wall surface of the door body 2. There is.

Figure 6 shows g51 in such a radio wave leakage prevention structure.
The total width L2 from the outer wall of the groove 8 to the outer wall of the second groove 9
The graph shows the change characteristics of radio wave leakage. From this characteristic, the total width L2 to effectively prevent radio wave leakage is approximately 4
0mm1. : Set. As mentioned above, in a normal microwave oven, 274 stitches are 30.5 mm, so the total width L2 including the first and second 8.9 mm in the second conventional example is λ
/4 is set to approximately 1.3 times.

As described above, the second conventional example has 6 effective radio wave leakage prevention capabilities without ferrite, but the problem is that the overall width L2 is relatively large and the radio wave leakage prevention means becomes large. was there.

(5?Problems that Akira attempts to solve) In the first conventional example in which ferrite is shared, the ferrite is relatively expensive, and the structure of the door body becomes complicated, which increases the number of steps. However, there was a problem in that the cost was high.

In addition, in the second conventional example without ferrite, the first,
There is a problem in that the total width including the second groove becomes relatively large, and the portion of the radio wave leakage prevention means becomes large.

This invention was made based on the above circumstances, and an object thereof is to provide a microwave oven equipped with a radio wave leakage prevention means that is ferrite-less, has excellent radio wave leakage prevention ability, and can be constructed in a small size at low cost. purpose.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention provides a door body that can be opened and opened at the opening of the heating chamber, and a peripheral part of the door body has the following features: As a means for preventing leakage of radio waves, a groove is formed in the inner wall of the door, and the groove is connected to an intermediate second groove and the second groove.
The first groove and the third groove are arranged in parallel on both sides of the groove, and the first groove and the third groove have a wavelength approximately 4 times the fundamental wavelength of the high frequency wave irradiated to the heating chamber. The depth of the second groove is formed to be shallower than the first and third grooves by a required depth, and the total groove width of the first, second, and third grooves is The gist is that the wavelength is one-fourth or less of the fundamental wavelength.

(Function) A second groove is formed between the first groove and the third groove, which have a depth of one-fourth of the wavelength of the high-frequency wave, and is shallower than both grooves by a depth of Y2. is provided, and due to the action of this intermediate groove, an effective radio wave leakage prevention ability can be obtained even if the overall groove width of the first, second, and third grooves is one-quarter or less of the fundamental wavelength. Therefore, the size of the radio wave leakage prevention means can be reduced.

(Example) Hereinafter, an example of the present invention will be described based on FIGS. 1 and 2.

In FIG. 1, parts that are the same as or equivalent to those in FIG. 4 are designated by the same reference numerals, and redundant explanation will be omitted.

First, to explain the structure of the radio wave leakage prevention means in this embodiment, a first groove 11 opened on the inner wall side of the door body 2 in the peripheral part 2a of the door body 2, and a second groove 12 in the middle. and a third groove 13 are arranged adjacently in parallel. first groove 1
The depth Ml of the first and third grooves 13 is approximately λ/4, which is the same depth, and the depth u2 of the second groove 12 is the same as that of the first and third grooves 11 and 13. For Sa11, as described later,
It is shallowly formed to a required depth of about 85% of that.

That is, as mentioned above, the frequency of irradiation to the heating chamber 3 is 2/150 Ml-1z, and the fundamental wavelength λ base is 122 mm.
At this time, the depth 11 of the first and third grooves 11.13 is approximately 30.5 mm, and the depth fL2 of the second groove 12 is approximately 26 mm.

The overall groove width L1 of the first, second, and third grooves 11, 12, and 13 is set to λ/4 or less, for example, about 24 mm.

FIG. 2 is a characteristic diagram showing the experimental results of the relationship between the depth IL2 of the second groove 12 and the amount of radio wave leakage when the overall groove width L1 is used as a parameter. From this experimental result, when the total groove width L+ -24 mm and the depth 2 of the second groove 12 = 26 mm, that is, the depth fL2 of the second groove 12 is
, the depth history of the third groove 11.13 + (h30°5mm
), it was confirmed that leakage radio waves are significantly attenuated when the value is as small as 85%.

This experimental value is achieved with good reproducibility and is based on the depth ul of the first, second, and third joint grooves 11, 12, and 13 described above.
, 12 and the multiple values of the overall groove width L1 are set based on the above experimental facts.

The radio wave leakage prevention means in the microwave oven of this example is as follows:
Since the configuration is as described above, the intermediate second full 12
Due to the action of the first, second and third grooves 11.12.13
Even if the entire groove width is made smaller than λ/4, an effective radio wave leakage prevention ability can be obtained, and since it can be made ferriteless, costs can be reduced.

The experimental values shown in Fig. 2 are an example, and the depths 1, 2, and the overall groove width L1 of the joint grooves 11, 12, and 13 are based on the experimental values shown in the figure. If the value is close to this value, practical radio wave reduction can be obtained.

[Effects of the Invention] As explained above, according to the present invention, there is a groove between the first groove and the third groove having a depth of one-fourth of the fundamental wavelength of the high frequency. Since we provided a second groove that was shallower than the required depth, the action of this middle groove would cause the first groove to
Even if the overall groove width of the second and third grooves is one-fourth or less of the fundamental wavelength, effective radio wave leakage prevention ability can be obtained, and the radio wave leakage prevention means can be miniaturized. In addition to this, there is an advantage that it can be made ferriteless and cost reduction can be achieved.

[BRIEF DESCRIPTION OF THE DRAWINGS] Fig. 1 is a longitudinal sectional view showing the radio wave leakage prevention means in an embodiment of the microwave oven according to the present invention, and Fig. 2 shows the overall groove width of the radio wave leakage prevention means. A characteristic diagram showing the relationship between the depth of the second groove and radio wave leakage ω when ω is taken as a parameter, Fig. 3 is a perspective view showing an example of a microwave oven, and Fig. 4 shows radio wave leakage prevention in the first conventional example. FIG. 5 is a vertical cross-sectional view showing the radio wave leakage prevention means portion in the second conventional example, and FIG. 6 is a full width including the first and second grooves in the second conventional example. It is a characteristic diagram showing the relationship between and the radio wave leakage value. 2: Door body, 2a: Periphery of door body, 3: Heating chamber, 11: First groove, 12: Second groove, 13
: Third groove.

Claims (1)

[Scope of Claims] A door body that can be opened and closed is provided at the opening of the heating chamber, and a groove that opens on the inner wall side of the door body is recessed in the periphery of the door body as a means for preventing leakage of radio waves. The groove is composed of an intermediate second groove and a first groove and a third groove that are arranged in parallel adjacent to both sides of the second groove, and the first groove and the third groove are arranged in parallel on both sides of the second groove. The depth of the groove is approximately one quarter of the fundamental wavelength of the high frequency wave irradiated to the heating chamber, and the depth of the second groove is formed to be shallower than the first and third grooves by a required depth, A microwave oven characterized in that a total groove width of the first, second, and third grooves is one-fourth or less of the fundamental wavelength.