JPS59230291A - Radio wave sealing device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a radio wave sealing device for shielding high frequency radio waves.

Structure of Conventional Example and Its Problems A conventional radio wave sealing device of this type will be described in two pages, taking as an example a microwave oven that dielectrically heats food using high frequency waves. A microwave oven is equipped with a heating chamber that stores food and heats it using high-frequency waves, and a door that can open and close the opening of the heating chamber for entering and exiting the food.
When opening the door to take out or take out food, a radio wave seal is installed to prevent high-frequency electromagnetic waves inside the heating chamber from leaking outside and causing harm to the human body.

As a conventional example, US Pat. No. 3,182,164 is shown in FIG. In FIG. 1, reference numeral 1 denotes a heating chamber of a microwave oven, and a door 4 having a handle 3 that covers an opening 2 of the heating chamber 1 so as to be openable and closable is provided. A hollow choke part 6 having a gap 6 opened toward the heating chamber 1 is formed at the peripheral edge of the door 4. The depth 7 of this choke portion 6 is designed to be substantially one-fourth of the wavelength of the high frequency wave used. In this case, the thickness of s4 is also a quarter wavelength. In other words, the frequency of the electromagnetic waves conventionally used in microwave ovens is 246(]1, so the quarter wavelength is approximately 30 mn.In order to make the choke part 3 of this length face the page 6, the heating The thickness 9 of the peripheral edge 8 formed in the opening 2 of the refrigerator 1 has a value larger than a quarter wavelength.

Therefore, the effective size of the opening 2 of the heating chamber 1 is the peripheral edge 8
It's just a little smaller.

Next, as another conventional example, U.S. Patent No. 2.500,6
No. 76 is shown in Figures 2a and b. Example (7) also shows the configuration of a microwave oven, in which high frequency waves obtained by oscillation of a magnetron 10 are supplied to a heating chamber 11 to cook food 12 by electromagnetic induction. This heating cabinet 1
The first opening 13 is provided with a door 14 that covers the opening 13 so as to be openable and closable. A groove-shaped choke portion 16 is also formed at the peripheral edge of the door 14, and this choke portion 16 prevents high frequency waves from leaking to the outside. This choke part 1
The depth 16 of 6 is also designed with a quarter wavelength of the frequency used. Therefore, the effective size of the opening 13 is slightly smaller than the heating chamber 11, as in FIG.

As mentioned above, the conventional choke part is based on the technical concept of JP-A-59-2 which attenuates high frequencies by having a depth of 1/4 wavelength.
30291(2).

That is, let the characteristic impedance of the choke part be Zo and the depth be L, and when the terminal end is short-circuited, the impedance at the choke part opening is zIN, 2πL Z I N = j Z otan (,,) (λ0 is free space wavelength).

The choke-type radio wave attenuation means selects the depth L of the choke part to be 1/4 wavelength.
=Zotan(1) =o.

It is based on the principle of achieving

If the choke part is filled with a dielectric material (relative permittivity εr), the wavelength λ' of the radio wave is compressed to λlL:tλ0/. In this case, the depth L' of the choke part is L'
Breasts/Misfortune It is short at 6 pages. However, there is no difference in setting L'=L'/4, and in the choke method, the depth cannot be made substantially smaller than 1/4 wavelength, and there is a limit to the miniaturization of the choke part. In recent years, the development of solid-state oscillators has progressed, and the era of practical use has arrived. Microwave ovens are no exception; traditional magnetron oscillators are being replaced by solid-state oscillators.

The advantages of solid-state oscillators in microwave ovens are as follows.

0) The drive voltage of a magnetron is about 3KV, while the drive voltage of a solid-state oscillator using a transistor etc. is about 40KV.
The voltage may be 0V or less, and in reality, about 40V is used.

Therefore, since the power supply voltage is low, it is safe for the human body, and even if there is a leak, electric shock accidents are unlikely to occur.

Therefore, it is possible to make it earthless, and it is also possible to develop a portable system.

(2) The lifespan of a magnetron is about 5,000 hours (Page 6), whereas the solid-state oscillator has a long lifespan of about 10 times longer.

(3) While the oscillation frequency of a magnetron is fixed, the oscillation frequency of a solid-state oscillator can be varied, for example, within a range of 13 skins above and below for a 916 rhinoceros. Therefore, by automatically tracking the frequency based on the size of the load (food to be cooked), the resonance frequency changes and high efficiency operation can be obtained. According to the experiment, 246o±5
By automatically tracking the frequency within 0 fusion, it was possible to improve the practical load efficiency by about 60 to so% compared to a fixed frequency.

(4) Solid-state oscillators could become cheaper than magnetrons in the future due to mass production.

In addition, the ISM frequency (Industrial) is currently internationally allocated for high-frequency cooking.

5 scientific, medical) is 5
880J 2450 stones.

915J 400& etc., and must not be used in any way. The current magnetron is 24 as mentioned above.
It is oscillated at 60 @, but if it is oscillated at the same frequency of 2450 & Ik with a solid-state oscillator, sufficient 7V output power will not be obtained and the power will be insufficient.

Therefore, in order to obtain the desired output power, it is necessary to select a lower frequency; for example, 9161 is suitable. However, since this frequency is about 1/2.7 of the conventional frequency, the wavelength is on the contrary about 2.7 times, and the quarter wavelength is about 80 mm.

Therefore, if 916° f. is selected as the frequency of the microwave oven, the thickness of the choke part explained in Figs. This has the disadvantage that it becomes extremely small, making it extremely difficult to put it into practical use.

On the other hand, the advantages of changing the oscillation frequency from 2450m to 9151m are as follows.

1. Because the wavelength has become longer, radio waves can penetrate deep into the food, making it possible to speed up the cooking process. For example, in order to bring the center of a piece of meat with a diameter of 12 (-g) to about 60°C, it took more than 6° with a 2450 J eoow, but it took less than 60 minutes with a 915 J 300 W.

2. The cause of uneven tanning is standing waves, and the standing wave pitch is correlated with wavelength. When using 915■, the pitch of the standing waves is large and uneven cooking is less noticeable on the cooked food.

Therefore, the disadvantage of changing the operating frequency of the microwave oven to 916 Hz is that the radio wave sealing means becomes larger.

Note that as one means for reducing the thickness of the choke portion, there is a configuration in which the choke portion is filled with a dielectric material. According to this configuration, the dielectric constant of the choke part increases, so the choke part can be made smaller than a quarter wavelength, and moreover, the choke part can be made smaller than a quarter wavelength.
It has the same effect as a wavelength choke section. However, since the dielectric material is expensive, the price of the entire microwave oven is also high, and the manufacturing time and cost are high, which has hindered its practical use.

The principle of the conventional example will be theoretically explained below.

The choke method is based on the well-known quarter-wavelength impedance conversion principle. That is, the characteristic impedance of the choke groove is Zoc, the depth of the groove is 9 pages to, the characteristic impedance of the leakage path 1 from the heating chamber to the choke groove is Zop, the length of the leakage path 17 is tp,
When the wavelength used is λ, the choke groove 1 is
The short circuit impedance (Zc=O) at the bottom C of 8 is at the opening B of the choke groove 18, and is Z B = j Z o ctan
-T-l, becomes. 19 is a heating chamber of the microwave oven λ, and 20 is a door. Here l. By choosing −1, it can be converted to IZBI=■. By selecting the impedance ZB of this opening B as the impedance principle C when viewed at the line starting point A, it can be converted to l Zp, l = o. The short-circuit condition at the bottom C of the choke groove 18 appears at the starting point of the line by skillfully utilizing the quarter-wavelength impedance conversion principle, thereby making it practical as a radio wave sealing device.

A dielectric material with a permittivity of ε is used in the leakage path 17 and the choke groove 18.
By loading, the wavelength λ' becomes 1/Pτ of the free space wave 10 page length λ, but a similar effect can be obtained by using the quarter wavelength (PI3) impedance principle.

OBJECTS OF THE INVENTION The present invention provides a radio wave sealing device in which the size of the choke portion does not increase even if the oscillation frequency is lowered.

Structure of the Invention The present invention is a radio wave seal using a new impedance conversion principle, in which each of the leakage path and groove has a characteristic impedance discontinuity configuration, resulting in a shape smaller than the size equivalent to a quarter wavelength. It is something.

DESCRIPTION OF EMBODIMENTS The present invention provides, for example, at least two grooves in at least one of the main body or the door of a microwave oven, and the shape of the grooves is such that the characteristic impedance on the short circuit side is larger than that on the open hole side. However, it is characterized in that the groove depth from the open end to the shorted end is less than a quarter wavelength.

The basic idea that enables the miniaturization of 11 pages is as follows.

The characteristic impedance and length phase constant of the groove opening are Zol
, 11. Let it be β1. The characteristic impedance and length phase constant of the groove short-circuit part are Zo2 + 12 + β2, and the distance (groove depth) from the open end of the groove to the short-circuit end 1 is l (t
total), it becomes 1(total)-A1-12.

Under the above conditions, the impedance Z at the opening end of the groove is (however, = Z02/zo1), which can be easily derived by calculation, but in the conventional example, it is
z=Zo+, which corresponds to β1-β2 (ie, =1). Therefore, the impedance Z' is calculated from equation 1 = Zo1tan (β1'1+β2A2) = Zo1tan
(β1-1total) (2) By setting ltotal to S, the impedance was inverted.

On the other hand, according to the configuration of the present invention, the characteristic impedance Z02>ZO4 from the constitutional requirements, so the value of the ratio of the characteristic impedances in equation 1 is necessarily larger than 1. In order to make the impedance Z infinite, the denominator of equation 1 needs to be zero, so 1-Ktanβ1'1・tanβ2'
2 only needs to be satisfied, and even if the dimensions 11° and 12 are reduced by the amount that the characteristic impedance ratio is larger than 1, impedance inversion similar to the conventional one can be achieved.

The idea of making the characteristic impedance discontinuous is as follows.

The present invention has a structure in which conductor plates having a width a are arranged in a groove portion of a sealing device with one end serving as a ground conductor and spaced apart by a gap dimension.

In detail, the width on the groove opening side is 81, the gap is bl, and the effective dielectric is ε. ff, and the width on the groove short-circuit side is a2 and the gap is β.
2, the ratio K of characteristic impedance is calculated using the following formula, and by setting the value on page 13 to be greater than 1, an attempt is made to make the characteristic impedance discontinuous.

The details of the embodiment will be explained based on the drawings.

FIG. 4 is a perspective view of a microwave oven, in which a door 22 having a patching plate 21 is attached to a main body covered with a main body cover 23. FIG. The main body is provided with an operation panel 24 and a door handle 25.
is attached to the door above.

FIG. 5 shows a sectional view taken along the line A--A in FIG. 4, and FIG. 6 shows a perspective view of FIG.

6, the radio waves from the heating chamber 26 are transmitted to the main body 2.
3 and the door 22 to the outside.

A recess 27' extending toward the periphery of the main body is formed in the door at a position facing the main body member. The tip of the recess forms a bent portion 28 .

Also, when assembled, the opening side of the groove 27 is B.

The short circuit side will be called C.

One wall surface constituting the groove 27 has a line width of 147.
- A plurality of conductor plates 29-a and 29-b, each having a diameter larger than the short-circuit part line width a2 and having a bent part at the tip on the side of the opening, are arranged at a pitch P in the longitudinal direction of the groove in the common part 30. It is composed of a conductor plate wall member 31 arranged thereon.

The cover 32 of the groove 27 is made of a microwave-transmissive low-loss dielectric material, and is inserted and fixed into a hole 33 provided in the door 22.

The conductor plate wall member 31 is fixed by means such as welding near the bent portion 28 of the door 22 in such a direction that the opening groove width b1 is smaller than the short circuit groove width b2. .

Effects of the Invention In addition to being able to downsize the radio wave sealing device, the invention has the following effects.

(1) Since there is only one groove, stable sealing performance is achieved even when the gap between the main body and the door changes.

(With multiple grooves, interference between the grooves often causes instability.) (1) The folded part of the door is the connecting member 16 between the door and the
It can be used as a surface to attach pages to.

(11) Since the folded portion of the door is shorter than the depth of the groove, material is saved, and the door can move smoothly when opening and closing.

(liD Since one groove is formed in the entire recessed part of the door, the groove width dimension b2 can be secured to fill the recessed part, so a compact sealing groove with a high Q can be realized.

(IV) The overall strength of the door is strong because of the bending part.

(V) Since the conductor plate wall member has a common part, the strength of the part is relatively maintained even before it is fixed to the door.

[Brief explanation of the drawing]

Fig. 1, Fig. 2 a, b, and Fig. 3 are cross-sectional views showing conventional radio wave devices, Fig. 4 is a perspective view of a microwave oven, and Fig. 6 is a cross-sectional view of a radio wave sealing device according to an embodiment of the present invention. Figure 6a,
b is an enlarged perspective view of the same main part. 27... groove, 27'... recess, 28.
...Folded portion at the tip of the recess, B...Opening portion of the groove, C...Short circuit portion of the groove, 29-a, 29-b
...Conductor plate, 30...Common part, 31.
...Conductor plate wall member. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure θ Figure 2 Figure 3 C Figure 4 4 Figure 5 Figure 6 Procedural amendment document July 77, 1988 Patent application No. 102040 1988 2 Name of the invention Radio wave seal device 3 Amend Relationship with the patent case Patent application Person address 1006 Oaza Kadoma, Kadoma City, Osaka Name (582) Representative of Matsushita Electric Industrial Co., Ltd.
Toshihiko Yamashita 4 Agent 571 Address 1006 Oaza Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. Detailed description of the invention in the specification subject to amendment 5 (Go112 type) Brief description of drawings in the specification Includes 2 drawings with an explanation. 6. Contents of the amendment (1) The following sentence will be inserted next to "It will be measured" on page 12, line 11 of the specification. [The present invention performs impedance inversion in a less than λ/4 line, rather than in the λ/4 line historically used in the field of radio wave sealing. In order to make this principle easier to understand, a part of the analysis results are shown in FIG. In FIG. 4, a groove having an opening B with a short-circuited tip C is provided in a part of a transmission line with the A end as an excitation source and the D end open. The width of the groove on the short circuit side is twice that on the open hole side. When point A is excited under the same conditions and the groove depth lT is changed, the electric field in the transmission line changes as a, b, c, and D
The radio wave does not reach the end in case b, that is, when the groove depth eT is about 8% of a quarter wavelength (less than λ/4 line), and even if the groove is long, it is short. Even if (a%C'), radio waves leak more than in b. This is 11=
112=(IT/2−λ/1o, 2.=b2/b1=
Confirmation 3 \-7 can be done by substituting 2 total 2/btanβ41・tanβ12. (2) On page 13, line 4 of the same page, insert the legal text after ``I am trying my best.'' “In actual application, the groove cover space (TO
Pl) and bends often provide a reinforcing space (lxl). In these cases, compared to the case where the principle is explained, the radio waves are disturbed and the calculated dimensions are slightly deviated. The details of the deviation are shown below. When 10210 dimensions are set to 211ff and 4X1 is set to 5~
An example is shown in which there are 6 fights. Figure 5 is an example of a 916 MHz sealing device and is the TOP1.
This shows the relationship in which the groove depth lT changes with the dimensions of . TOPl
If you increase the size of 1 to 3, the IT will be 1 to 6 questions deeper. Figure 6 is an example of a 2450 MHz sealing device.
The relationship is shown in which the depth 4T of the groove changes with the reinforcing space 1'X1) while fixing OP1=2πm. space l x 1 to 2
~ By making it 6 fights, the depth of the groove 7T will be 1 to 3 birds deeper. (3) Correct and edit "Figure 4" in lines 6 and 10 of page 13 to "Figure 7". (4) Correct “Figure 1, Figure 5” in lines 10, 11, and 12 of page 13 to “Figure 8.” (5) Page 13, lines 10 and 12, “Figure 6”
Correct it to "Figure 9". (6) "Figure 4 is..." on page 15, lines 15 to 17 will be corrected as follows. "Fig. 4 a, b, c are electric field analysis diagrams of the groove portion in the present invention, Fig. 5 a% b, c are sectional views, side views, and characteristic diagrams of the device at 915MH2. Fig. 6 a, b, c are 246oMH
7 is a perspective view of a general microwave oven, FIG. 8 is a sectional view of a radio wave sealing device in an embodiment of the present invention, and FIGS. 9 a and b is an enlarged perspective view of the same main part. (7) The drawing numbers of Figures 4, 6, and 6 have been corrected to Figures 7, 8, and 9 as shown in red on the attached sheet, and Figures 4 and 5 are as shown in the attached sheet. , add Figure 6. Figure 4 and Z Riku/＾ν Number F γ GeoreOIL-1211-cho 443-

Claims (1)

[Claims] A main body having an opening to which radio waves are supplied is provided, a door is provided to cover the opening of the main body so as to be openable and closable, and a tip shorter than the depth of the groove is provided on at least one of the parts facing the main main door of the main body. A conductor plate wall member having a common part in which a plurality of conductor plates are arranged, each having four parts with bent parts, the line width of the opening part being larger than the line width of the short circuit part, and having the bent part at the tip on the side of the opening part. A radio wave sealing device comprising: a conductor plate wall member fixed to the bent portion near the tip of the recess in a direction such that the opening groove width is smaller than the short circuit groove width.