KR20030069081A - Choke structure of the door in high frequency heating apparatus - Google Patents

Abstract

The present invention provides a choke structure of a door of a high frequency heating apparatus that can reduce leakage electromagnetic waves to the outside by a simple configuration and is easy to process, and includes a plurality of slits 12 on each of the peripheral portions of the door 2 of the high frequency heating apparatus. A choke structure (1) having a plurality of chokes (6, 7) divided into a), the choke structure (1), each of the width L in the longitudinal direction of the choke (6) of the four corners of the door (2) It was set as any one of 3/16 or more, 5/16 or less, 7/32 or more, 9/32 or less, or 1/4 of wavelength (lambda) of a use frequency.

Description

CHOKE STRUCTURE OF THE DOOR IN HIGH FREQUENCY HEATING APPARATUS}

The present invention relates to a choke structure of a door of a high frequency heating device.

For a conventional door choke structure for preventing radio wave leakage of a door in a microwave oven, for example, a slit such as "waveform leakage prevention device for a microwave oven" (wave leakage prevention by a periodic structure) (National Technical Report Vol 22. No2) The choke structure provided is shown. Fig. 5 shows the relationship between the pitch of the choke width in the longitudinal direction and the leakage power density shown in this document. According to Fig. 5, the leakage power density is decreased by making the slit a short pitch in the longitudinal direction. . Therefore, it is understood that it is better to provide a short pitch as far as the slit can be in the longitudinal direction with respect to radio wave leakage.

However, in the above-described conventional choke structure, electromagnetic waves may be reduced by shortening the slit pitch, but in reality, even if the slit pitch is shortened, leakage electromagnetic waves from the four corners of the door serving as the opening cannot be reduced. There is a problem that the relationship between the width and the leakage power density is unclear.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a choke structure of a door of a high frequency heating device which can reduce leakage electromagnetic waves to the outside by a simple configuration and is easy to process.

1 is a rear view of a microwave oven door according to Embodiment 1 of the present invention;

2 is an enlarged view of the choke structure of the microwave oven door according to the first embodiment of the present invention;

Fig. 3 is a relation diagram of the width in the longitudinal direction of the choke of the four corner portions of the microwave oven door according to the first embodiment of the present invention and the magnitude of the leakage power density;

Fig. 4 is a relation diagram of the magnitude of the leakage power density by the distance between the door and the heater of the microwave oven according to the first embodiment of the present invention;

Fig. 5 is a diagram comparing the relationship between the pitch of the choke width in the longitudinal direction and the leakage power density of the choke of the microwave oven door according to the second embodiment of the present invention;

Fig. 6 is a relation diagram of the pitch of the choke width in the longitudinal direction of the conventional microwave door choke and the leakage power density.

Explanation of symbols for the main parts of the drawings

1: choke structure 2: door

4: periphery of the heating chamber 5: four corners

6: choke of the four corners 7: choke

12: slit

The choke structure of the door of the high frequency heating device according to the present invention includes a choke structure having a plurality of chokes divided into a plurality of slits on each of the periphery portions of the door of the high frequency heating device, wherein the choke structure includes the choke of the four corners of the door. The width in the full length direction is set to 3/16 or more and 5/16 or less of the wavelength? Of the use frequency, respectively.

In addition, a choke structure having a plurality of chokes divided into a plurality of slits on each of the periphery of the door of the high-frequency heating device, the choke structure, the width of the choke only longitudinal direction of the four corners of the door, respectively, the wavelength of the use frequency 7/32 or more and 9/32 or less of (lambda).

In addition, a choke structure having a plurality of chokes divided into a plurality of slits on each of the periphery of the door of the high-frequency heating device, the choke structure, the width of the choke only longitudinal direction of the four corners of the door, respectively, the wavelength of the use frequency 1/4 of λ.

Further, a choke structure having a plurality of chokes divided into a plurality of slits on each of the periphery of the door of the high frequency heating device, the choke structure, at least the width in the longitudinal direction of the choke of the four corners of the door, respectively, It is set as 1/4 or more and 5/16 or less of wavelength (lambda).

(Example 1)

1 is a rear view of a microwave oven door according to a first embodiment of the present invention, FIG. 2 is an enlarged view of the choke structure of FIG. 1, and FIG. 3 is a relationship between the width in the longitudinal direction of the choke of the four corners of the door and the magnitude of the leakage power density. Fig. 4 is a relationship diagram between the width in the longitudinal direction of the choke of the four corner portions of the door and the magnitude of the leakage power density when the distance between the door and the heater is changed.

1 and 2, reference numeral 2 denotes a choke structure having a plurality of chokes divided into a plurality of slits 12, each of which is provided at a door of a microwave oven, and a reference numeral 1 denotes four peripheral portions of the door 2; Reference numeral 5 denotes four corners of the door 2 to be an opening (of the choke structure 1), reference numeral 6 denotes four chokes of the four corner portions 5, and reference numeral 7 denotes four corner portions 5 A choke other than the choke 6 in Fig. 4 is the periphery of the heater, and the reference numeral 8 is the choke groove.

In the conventional choke structure, since the leaked electromagnetic waves from the four corners of the door 2 tend to go out, in the configuration shown in Figs. 1 and 2, the widths of all the chokes of the choke structure 1 in the longitudinal direction are not changed. Only the chokes 6 (8 locations) of the four corner parts 5 of (2) changed the width | variety L of the longitudinal direction to various widths, and the magnitude | size of the leakage power density was adjusted.

First, the use frequency is 2.45 GHz, which is the use frequency of the microwave oven, and 3λ / 16 (about 23 mm), 7λ / 32 (about 26.8 mm), λ / 4 (about 31 mm), The magnitude | size of the leakage power density in the case of setting it as 9 (lambda) / 32 (about 34 mm) and 5 (lambda) / 16 (about 38 mm) was measured.

This result is shown in FIG. The magnitude of the power density is a comparison value when the standard of leakage power density is 5 mW / cm 2 or less at a position 5 cm apart when the standard of the leakage power density is slightly opened after the operation of the microwave oven and just before the stop of operation. It is indicated by.

In Fig. 3, the magnitude of the leakage power density is close to zero when λ / 4, and becomes large when λ / 4 or less, or more, and 0.4, 7λ / 32, or less, 2/5 or less of the standard value when 3λ / 16 or more and 5/16 or less. In the above-mentioned 9 (lambda) / 32 or less, it was 0.2 or less of 1/5 of the standard value.

In this way, the widths of the chokes 6 of the choke structure 1 are not changed in the longitudinal direction, and only the chokes 6 of the four corner portions 5 of the door 2 have the width in the longitudinal direction as described above. The specification of power density could be fully satisfied.

The general choke structure is a waveguide in which the choke groove 8 is short-circuited with respect to the electromagnetic wave traveling in the A direction shown in Fig. 2, so that the impedance seen from the incidence portion of the choke groove 8 is Z = -jZ _c tanβr (r: Line length, β: phase constant (2π / λ), and Z _c : impedance of the waveguide.

The principle of the choke structure is based on the principle of reflecting electromagnetic waves traveling in the A direction with the impedance of ∞ by setting the depth of the choke groove 8 to λ / 4.

In addition, as for electromagnetic waves traveling in the B direction, as described in the above-mentioned document "Anti-electromagnetic wave leakage prevention apparatus for microwave ovens" (propagation leakage prevention by periodic structure) (National Technical Report Vol 22.No2), by providing a slit in the choke structure It is said that leakage of electromagnetic waves can be prevented.

The present invention is an invention for the choke 6 serving as an opening of four corner portions of a door portion that has not been considered in the past.

Here, the operation of the choke 6 will be described. When the choke 6 of the four corners of the door 2 is considered to be a waveguide of the terminal opening of the electromagnetic wave traveling in the longitudinal direction, the impedance seen from the slit 12 is

Z = -jZ _c cotβr

Where r is the length of the track

β: phase constant (2π / λ)

Z _c : Impedance of waveguide

When the choke width is close to? / 4, the impedance is close to zero, which is the same as that of the waveguide that is short-circuited. As a result, the electromagnetic waves propagating in the longitudinal direction are reflected by the chokes 6 at the four corners, so that electromagnetic waves leaking from the four corners of the door 2 are reduced, resulting in an efficient choke structure.

As described above, the width L of the chokes 6 (8 locations) of the four corner portions 5 serving as the openings of the choke structure 1 of the door 2 is 3λ / 16 or more and 5λ / 16 or less of the use frequency. It is preferable that it is set to the length of (about 23 mm-38 mm at 2.45 GHz of a microwave oven). More preferably, it is about 26.8 mm-34 mm), and it is most preferable to set it as (lambda) / 4 (about 31 mm).

Next, when the clearance gap between the door 2 and the periphery part 4 of a heating furnace is 1 mm and 1.5 mm, the longitudinal direction of the chokes 6 (8 places) of the four corner parts 5 of the door 2 is carried out. The leakage power density when the width L was set to 2.45 GHz, which is the use frequency of the microwave, and was set to 1/8 (about 15.5 mm) and 1/4 (about 31 mm) of the wavelength? . As a result, as shown in Fig. 4, when the width of the choke is λ / 8 and λ / 4, there is no significant difference in the state in which the door is opened 1 mm, but the leakage power density when the 1.5 mm is opened is λ. When it is set to / 4, it can be reduced to approximately 1/3 of λ / 8. For this reason, the width | variety L of the longitudinal direction of the choke 6 of the four corner parts 5 of the door 2 is set as the clearance of the operating frequency of a microwave oven, so that the clearance gap 4 of the door 2 and the heater is large. The effect of making it about 1/4 (about 31 mm) of wavelength (lambda) is large.

As mentioned above, the width | variety of the longitudinal direction of all the chokes 5 and 7 of the choke structure 1 does not make all the constant ranges, but the longitudinal direction of the choke 6 of the four corner parts 5 of the door 2 is carried out. By setting the width of the to within a certain range, it is possible to reduce the leakage electromagnetic waves to the outside by a simple configuration.

In addition, since the width L in the longitudinal direction of the choke 6 at the four corners may be set within a predetermined range, the machining precision does not need to be high, and the machining can be easily performed.

(Example 2)

In Example 1, although the choke structure of the microwave oven door made the width of the choke of the four corners of a door the longitudinal direction constant, this embodiment made the width | variety of the length direction of all the chokes constant length.

In FIG. 1 of Embodiment 1, the width L in the longitudinal direction is determined with respect to the wavelength? Of the use frequency for both the choke 6 at the four corners of the door and the choke 7 other than the choke 6. (lambda) / 4 or more and 5 (lambda) / 16 or less.

As a result, in each choke structure 1 of the door 2, the impedance of the slit portion 12 is higher than zero with respect to the electromagnetic waves traveling in the longitudinal direction by close to the shorted waveguide with an impedance of zero. It progresses without leaking from the slit part 12, and becomes an efficient choke structure, and the leakage of electromagnetic waves becomes low by making the width | variety of the longitudinal direction of the choke 6 of four corners constant.

In addition, as shown in Fig. 5, the conventional example reduces the leakage power density by shortening the pitch, but unlike the conventional example, as shown by the thick line in Fig. 6, it is considered that there is a suitable pitch around? / 4. Therefore, it is preferable to set the width L of the chokes 6 and 7 to a length of 3 lambda / 16 or more and 5 lambda / 16 or less of the use frequency (approximately 23 mm to 38 mm at the use frequency of the microwave of 2.45 GHz). More preferably, it is most preferable to set it as 7 (lambda) / 32 or more and 9 (lambda) / 32 or less (about 26.8 mm-34 mm), and (lambda) / 4 (about 31 mm).

As mentioned above, since the width | variety of the longitudinal direction of the chokes 6 and 7 may be set in a fixed range, it is not necessary to make processing precision high, and it can make processing easy, and can reduce the leakage electromagnetic wave to the outside. .

In the present embodiment, the widths of the chokes 6 and 7 are all made to be constant lengths, but at least one of the chokes 6 and at least one of the chokes 7 is not the whole width. It may be a constant length.

In addition, although the choke structure of the microwave oven door was shown in Example 1, 2, you may apply to the leakage prevention of the electromagnetic wave of the door of a high frequency heating apparatus, or other high frequency apparatus.

As described above, according to the present invention, each of the periphery of the door of the high-frequency heating device is provided with a choke structure having a plurality of chokes divided into a plurality of slits, wherein the choke structure includes only the chokes of the four corners of the door in the longitudinal direction. Since the width is set to 1/4 or more and 5/16 or less, respectively, of the wavelength? Of the use frequency, leakage electromagnetic waves to the outside can be reduced by a simple configuration.

In addition, the machining precision does not need to be high, and the machining can be easily performed.

In addition, a choke structure having a plurality of chokes divided into a plurality of slits on each of the periphery of the door of the high-frequency heating device, the choke structure, the width of the choke only longitudinal direction of the four corners of the door, respectively, the wavelength of the use frequency Since it is set to 7/32 or more and 9/32 or less of (lambda), the leakage electromagnetic wave to the outside can be reduced more by simple structure.

In addition, a choke structure having a plurality of chokes divided into a plurality of slits on each of the periphery of the door of the high-frequency heating device, the choke structure, the width of the choke only longitudinal direction of the four corners of the door, respectively, the wavelength of the use frequency Since it is set to 1/4 of λ, leakage electromagnetic waves to the outside can be further reduced by a simple configuration.

Further, a choke structure having a plurality of chokes divided into a plurality of slits on each of the periphery of the door of the high frequency heating device, the choke structure, at least the width in the longitudinal direction of the choke of the four corners of the door, respectively, Since it is set to 1/4 or more and 5/16 or less of wavelength (lambda), the leakage electromagnetic wave to the outside can be reduced more easily by a simple structure.

In addition, the machining precision does not need to be high, and the machining can be easily performed.

Claims (3)

A choke structure having a plurality of chokes divided into a plurality of slits in each of the peripheral portions of the door of the high frequency heating device, The choke structure is a choke structure of a door of a high frequency heating apparatus, wherein the width of the choke only length direction of the four corners of the door is set to 3/16 or more and 5/16 or less of the wavelength? Of the use frequency, respectively. A choke structure having a plurality of chokes divided into a plurality of slits in each of the peripheral portions of the door of the high frequency heating device, The choke structure is a choke structure of a door of a high frequency heating device, wherein the width of the choke only length direction of the four corners of the door is set to 7/32 or more and 9/32 or less of a wavelength? A choke structure having a plurality of chokes divided into a plurality of slits in each of the peripheral portions of the door of the high frequency heating device, The choke structure is a choke structure of a door of a high frequency heating device, characterized in that at least four widths of the choke in the four corners of the door are set to 1/4 or more and 5/16 or less of a wavelength?