KR20050032424A - Shielding apparatus for electro-magnetic wave of electric oven - Google Patents

Abstract

An electromagnetic wave shielding device of a high frequency heating cooker is provided to insulate various incident angle electromagnetic waves efficiently by adjusting length of a slot between an inductance plate and a capacity plate according to incident wave angle. An LC filter unit(110) is installed in a circumference of a door frame(101) opposed to an upper wall of an oven perpendicularly bent from a front plate of a cavity in an electromagnetic wave shielding device, and composed of a reflecting plate(111) extended in the door frame to the upper wall of the door, an inductance plate(112) and a capacity plate(113) bent and formed of inverse L-shape between the reflecting plate and the door frame and slots(114) arranged periodically and formed from the capacity plate to the inductance plate. The inductance plate is connected to the capacity plate in series with capacity or inductance impedance.

Description

Shielding apparatus for electro-magnetic wave of electric oven

In the present invention, in the heating cooking apparatus, an electromagnetic wave shield of a high-frequency heating apparatus, in particular, by applying an LC filter for shielding electromagnetic waves leaking out from the cavity to improve the change in the shielding performance according to the angle of the incident wave Relates to a device.

In general, a microwave oven puts food on a rotating tray, and a high frequency generated from a magnetron is irradiated into the cavity so that food is cooked by the high frequency and the upper and lower surfaces of the cavity as well as the high frequency microwave. It is divided into a multi-functional microwave oven that installs a heater to cook dishes such as a grill and an oven.

Such a multi-functional microwave oven (hereinafter referred to as an electric oven) is usually cooked at a high temperature of about 100 to 300 ° C. when cooking an oven, so that a heat dissipating door is installed at the front of the oven chamber so that heat during cooking is not emitted to the outside. do. That is, when cooking, cooking is performed with the door closed, and before and after cooking, food is stored and taken out with the door open.

As such, the apparatus for heating the dielectric using microwaves (microwave oven, electric oven, over the range, etc.) is composed of a cavity 10 and a door 11 to trap the electromagnetic wave as shown in FIG. . Since these devices have a very high frequency power, if not properly blocked, it will seriously damage life and electronic devices including people around them. Therefore, the junction of the cavity 10 and the door 11 for proper blocking of harmful electromagnetic waves. A filter is installed on the surface to block harmful electromagnetic waves.

To this end, the cross-sectional view of the cavity and the door are combined as an example, as shown in FIG. As shown in FIG. 2, the inner joining surface 21a of the end 21 of the door 21 coupled to the front surface of the cavity 20 is formed in an “L” shape and is mainly applied to an electric oven.

3 and 4 are a perspective view and a side cross-sectional view showing a conventional electromagnetic shielding device.

Referring to FIGS. 3 and 4, the shield choke part 31 is installed on the inner circumferential surface of the door frame 30 coupled to the cavity front surface 40 to shield electromagnetic waves leaking from the inside of the cavity to the outside.

The shield choke portion 31 has a short plate 32 formed horizontally extending at an inner end of the door frame 30, and is bent in a direction perpendicular to the short surface 32 and has a period of λ / 4. And a shield choke 33 for shielding high frequency energy leaking outward from the cavity. Here, the shield choke 33 is bent vertically to the short surface 32, the choke top surface 33 facing the oven top wall 41, and the slot (slot or slit) having a predetermined period on the choke top surface 33 It consists of 34.

This shielding structure is basically a structure in which the choke top surface 33 has a λ / 4 choke structure on the short surface 32, and the impedance of λ / 4 choke is inserted between the lines. Such a shielding structure may represent an equivalent circuit as shown in FIG.

In general, λ / 4 choke causes an inversion of impedance each time the length of the line is reached. In other words, the impedance changes from zero to open and from open to zero every λ / 4. The equivalent circuit shows the equivalent impedance of Fig. 4B. Therefore, as shown in FIG. 4B, when the length of the line becomes λ / 4 and the impedance becomes infinite, the line is opened, so the output Pout becomes zero.

In other words, the electromagnetic wave incident from the electromagnetic source (magnetron) into the cavity is resonated in a specific mode in the cavity, and these various modes determine the angle of incidence into the oven door. Shielding electromagnetic waves with varying angles of incidence is difficult to achieve with a simple structure of λ / 4 chokes.

In order to improve this performance problem, a periodic slot 34 is formed in the choke top surface 33. The periodic slot 34 is designed to effectively shield electromagnetic waves incident at any incident angle.

However, the change in performance according to the incident angle of the incident wave is very affected by the length of the slot 34 to be formed. Accordingly, the λ / 4 choke used in the oven has a problem in that a slot portion cannot be formed at the portion of the short surface 32 exposed to the cavity of the oven for the user's cleanability. This restriction is a factor that weakens the shielding characteristics for electromagnetic waves incident at various angles of incidence on the shielding choke.

In addition, such a conventional choke structure is a current structure designed to have a small change in the performance of the shield choke portion 31 against the fluctuation of the cap between the door frame 30 and the front plate 40, that is, the shield choke portion 31 The advantages of the structure located inside the cavity are not fully utilized. That is, because the choke itself is a structure in which the characteristic itself does not change much with the distance from the oven upper wall 41.

Therefore, the structure considering the environmental conditions at the high temperature of the oven and the cleaning properties of the consumer, but is not a good structure.

The present invention has been made to solve the above-mentioned problems, the high frequency heating device which can effectively shield the electromagnetic wave of any angle incident to the filter by using the LC series filter structure of the electromagnetic shield installed inside the door Its purpose is to provide an electromagnetic shielding device.

Another object of the present invention is to form an inductive plate and a capacitive plate bent between the inner side of the door frame and the reflecting plate, and to form a slot arranged at regular intervals between the two plates, thereby inducing capacities and sides of the upper side It is an object of the present invention to provide an electromagnetic shielding device of a high frequency heating device that functions as a castle.

It is still another object of the present invention to provide an electromagnetic shielding device of a high frequency heating apparatus in which an inductive plate and a capacitive plate installed between a reflecting plate and a door frame can be installed in an "a" structure or its reverse structure. have.

Still another object of the present invention is to form a slot arranged in the inductive plate and the capacitive plate to a depth corresponding to the upper portion of the inductive plate in the capacitive plate, so that the length of the slot can be adjusted according to the angle of the incident wave It is an object of the present invention to provide an electromagnetic shield of a high frequency heating device.

Electromagnetic shielding device of the high frequency heating device according to the present invention for achieving the above object,

In the electromagnetic shielding device is installed on the inner outer peripheral surface of the door frame that is matched to the front of the cavity, to shield the electromagnetic wave flowing out from the inside of the cavity,

A reflecting plate opposed to the cavity on the inner side of the door frame and extending to the upper wall of the door, an inductive plate and a capacitive plate that is bent between the extending plate and the door frame to have an "a" shape, and are arranged at regular intervals; It characterized in that it comprises an LC filter consisting of a slot formed from the capacitive plate to the top of the inductive plate.

Preferably, the capacitive plate is formed between the capacitive plate and the door upper wall so that the capacitive plate functions as the capacitive plate, and the inductive plate is formed between the inductive plate and the door frame to function as the inductive plate. In addition, the capacitive and inductive properties are characterized in that connected in series with each other.

Preferably, the inductive plate and the capacitive plate are installed between the reflecting plate and the door frame in an inverted "a" shape.

Hereinafter, with reference to the accompanying drawings as follows.

9 is a perspective view showing the electromagnetic wave shielding device of the door according to an embodiment of the present invention.

Referring to FIG. 9, a capacitance plate and an inductance impedance in series between the reflecting plate 111 extending inside the door frame 101 and the reflecting plate 111 and the door frame 101 are provided in series. A choke side 112 and a capacitive plate 113 bent into a shape of "a"; It consists of a slot 114 formed periodically from the capacitive plate 113 to the top of the choke side 112.

That is, the slot 114 extends from the capacitive plate 113 to the upper end of the inductive plate 112 and is processed into a "￢" shape.

Referring to the accompanying drawings, the electromagnetic wave blocking device of the door according to the embodiment of the present invention configured as described above is as follows.

5 and 6, the LC filter unit 110 is installed on the inner circumferential surface of the door frame 101 facing the oven upper wall 121 that is bent vertically from the cavity front plate 120, thereby allowing the interior of the cavity. Blocks the electromagnetic waves exiting to the outside of the door.

The LC filter unit 110 is provided with a reflecting plate 111 is extended to the outside of the viewing window 102 installed on the inner surface of the door frame 101, the reflecting plate on the inner vertical surface (101b) of the door frame 101. An inductive plate 112 protrudes from the 111, and a capacitive plate 113 bent from the inductive plate 112 toward the reflecting plate 111 is installed, and the inductive plate 113 and the capacitive layer are formed. The plate 114 is formed with a slot 114 having a predetermined period, the slot 114 is processed into a "￢" shape from the capacitive plate 113 to the top of the inductive plate 112.

Here, the inductive plate 112 protrudes vertically from the frame bottom surface 101b which is a vertical position of the door frame 101, and is spaced apart from the inner surface 101a of the door frame 101 by a predetermined distance. Here, the support frame may be separately installed with a predetermined shape at the lower end so that the inductive plate 112 may protrude vertically from the frame.

At this time, the oven upper wall 121 at the position facing the capacitive plate 113 is spaced apart by a predetermined distance d1, and a capacitor is generated in the space. In other words, the capacitive plate 113 functions as a capacitance, and the capacitor is inversely proportional to the distance d1 between the two plates 113 and 121 and is proportional to the area of the capacitive plate 113 which is the capacitive plate. Done.

In addition, it has a value of inductance in the space d2 between the inductive plate 112 and the door frame inner surface 101b.

Then, the current flowing through the oven top wall 121 flows through a capacitor formed between the oven top wall 121 and the capacitive plate 113 as a displacement current, and into the inductive plate 112. It flows in the form of electrical current. Therefore, the inductive plate 112 operates inductively, and has a different inductance value depending on its structure.

Capacitive and inductive properties are formed in series through the capacitive plate 113 and the inductive plate 112, and are illustrated by the slots 114 formed in the capacitive plate 113 and the inductive plate 112. As shown in 6 (b), the LC filter is arranged periodically.

As described above, the LC filter unit 110 shields the leakage of electromagnetic waves by using the principle of series resonance between two lines. The LC filter unit 110 has a capacitive capacitor C and an inductive inductance L between the two lines. ) Is connected in series, and when the values of these two elements (LC) are tuned to the oscillation frequency of the electromagnetic wave source to be used, the circuit is resonant and the impedance between the two lines becomes zero. ), All the electromagnetic waves traveling between the two lines are reflected.

The structure of the LC filter unit 110 is periodically arranged by the slot 114 is formed along the inner outer periphery of the cavity door, each structure arranged periodically is due to the current flowing in the inductive plate 112 It is designed to be coupled to each other through the magnetic field region formed around it, but the amount is very small. In other words, coupling between adjacent structures is very small, allowing them to act independently of one another.

The LC filter structure can easily adjust the performance (resonance frequency or characteristic factor) of the filter, which is advantageous in design and can freely adjust the length of the slit, thereby improving the change in shielding performance according to the angle of the incident wave. It becomes possible.

 7 is another embodiment of the present invention.

Referring to FIG. 7, the LC filter unit 210 may have a reflector 211 extending from an inner circumferential surface of the door frame 201 in contact with a cavity, and may be formed in a ““ ”shape between the door frame and the reflector. A curved inductive plate 212 and a capacitive plate 213 and a slot 214 formed on the inductive plate 212 above the capacitive plate 213 and arranged at regular intervals.

Referring to FIG. 7, an inductive plate 212 is installed on the inner circumferential surface of the door frame 201 after being spaced apart from the inner surface of the reflecting plate 211 and the inner surface of the door frame 201, and the inductive plate 212 is provided. The capacitive plate 213 is bent from the side toward the outer door. That is, it has the reverse structure of FIG.

In this case, the LC filter unit 210 has an inductance formed between the inductive plate 212 and the reflecting plate 211, and the capacitive plate 213 has a capacitive property formed between a door upper wall (not shown). The inductance allows the inductive plate 212 to operate inductively, and the capacitive plate 213 functions capacitively, inversely proportional to the distance between the two plates (i.e., d1) and proportionally to the area of the capacitive plate. do. These capacitive plates and inductive plates are arranged periodically by periodic slots 214, and each of the periodically arranged structures are mutually coupled through magnetic field regions formed around them due to the current flowing in the inductive plates, The amount is designed to be very small. That is, by making the coupling between the adjacent structures very small, they work independently of each other.

In addition, the reflector plate (111,211) is located in the oven cavity side to open the door and the consumer has the same cleaning convenience as before.

As described above, according to the electromagnetic wave shielding device of the high frequency heating apparatus according to the present invention, it has an incident angle characteristic superior to that of the conventional λ / 4 choke, and it is effective to effectively shield electromagnetic waves of any angle incident on the filter. .

Conventional shielding devices using λ / 4 chokes require a distance of 1/4 of the wavelength of use, thus limiting the compactness of the door, but the LC filter of the present invention controls the capacitive and inductive plates. Tuning is possible, which is advantageous for making a compact door.

In addition, since the length of the slot can be freely adjusted, there is an effect of improving the change in the shielding performance according to the angle of the incident wave.

In addition, since the reflector is installed toward the oven cavity, when the door is opened and the consumer cleans, it has the same convenience of cleaning as before.

1 is a schematic configuration diagram of an electronic heating cooker.

Figure 2 is a perspective view showing the electromagnetic shielding structure of the door of the conventional heating cooker.

Figure 3 is a perspective view showing a conventional electromagnetic shielding device.

Figure 4 is a side cross-sectional view showing a conventional electromagnetic shielding device.

5 is a perspective view of a radio wave shielding device for a door according to an exemplary embodiment of the present invention.

5 is a side cross-sectional view and a circuit diagram of an electromagnetic shielding apparatus according to an embodiment of the present invention.

7 is a perspective view showing an electromagnetic shielding apparatus according to another embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

101,201 ... door frame 102 ... reflection window

110,210..LC Filter 111,211 ... Reflector

112,212 Inductive Plate 113,213 Capacitive Plate

114,214 ... slot 120 ... front

121.Oven top wall

Claims (3)

In the electromagnetic shielding device is installed on the inner outer peripheral surface of the door frame that is matched to the front of the cavity, to shield the electromagnetic wave flowing out from the inside of the cavity, A reflecting plate opposed to the cavity on the inner side of the door frame and extending to the upper wall of the door, an inductive plate and a capacitive plate that is bent between the extending plate and the door frame to have an "a" shape, and are arranged at regular intervals; Electromagnetic shielding device of the high-frequency heating device comprising a slot formed from the capacitive plate to the top of the inductive plate. The method of claim 1, Capacitive is formed between the capacitive plate and the upper door of the door to function as capacitive, inductive is formed between the inductive plate and the door frame, the inductive plate functions as inductive, and the capacitive and inductive are mutually Electromagnetic shielding device of a high frequency heating device, characterized in that the operation in series. The method of claim 1, The inductive plate and the capacitive plate are inverted "a" shape of the electromagnetic shielding device of the high frequency heating apparatus, characterized in that installed between the reflecting plate and the door frame.