KR960006604B1 - High frequency wave sealing device for microwave oven - Google Patents

Abstract

The apparatus comprises an inside panel in contact with a front plate of the oven; a short side formed by bending in a horizontal direction to one end of the inside panel; a first shielding means for shielding high frequency energy in the "X" direction, leaking to outside of the heating room; an outside panel of which one edge is bent in a vertical downward direction, the external panel being successively formed in line with the inside panel; a second shielding means for shielding the high frequency energy in the "Z" direction, leaking to the outside of the heating room; and a chock cover installed in line with a slit of the outside panel and the first shielding means.

Description

Microwave shielding device

1 is a perspective view of a typical microwave oven.

2 is a cross-sectional view of a door choke seal structure for high frequency shielding in a conventional microwave oven.

3 is a perspective view of the second choke shield door choke seal structure,

4 is a diagram showing an impedance relationship in a transmission line for explaining FIG.

5 is a cross-sectional view of a high frequency shielding door choke seal structure of the present invention.

6 is a perspective view of the high frequency shielding door choke structure of FIG.

7 is an enlarged perspective view of the first shielding means of FIG.

8 to 11 are perspective views showing another embodiment of the first shielding means of the present invention.

FIG. 12 is a diagram illustrating transmission line modeling for explaining the first shielding means of FIG. 5;

* Explanation of symbols for main parts of the drawings

300: oven prompt plate 301: inner plate body

302: sort surface 303: heating chamber

304: Outer plate 305: Slit

306: choke cover 307: leak check probe

313: First choke seal 314: Second choke seal

315: first shielding means

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a door choke seal structure for preventing high frequency leakage in a microwave oven. In particular, the present invention effectively prevents high frequency leaks to the outside through a gap between a heating panel front panel and a door of a microwave oven. As well as the shielding box, the thickness and choke length of the door are shortened, and the high frequency shielding device of the microwave oven is used to block the high frequency without using ferrite rubber.

In general, the microwave oven is formed in the main body 100, as shown in the accompanying drawings, the heating chamber 102 for heating food with high-frequency energy generated in the magnetron (not shown), and the heating The door 101 which opens and closes so that food can be taken out to the chamber 102, and the see-through window 103 attached to the said door 101 so that the inside of the heating chamber 102 can be seen.

Thus, the high frequency shielding door choke seal installed in the door 101 of the conventional microwave oven, which is configured, is fixed to the door panel (not shown in the figure), as shown in FIGS. 2 and 3 of the accompanying drawings. Inner portions of the door frame (not shown) are formed on the contact surface 200a to which the oven front play diagram 104 is contacted and the inner plate body 200 which is maintained as the non-contact surface 200b. In the formed outer plate 201, slits 202 having a length of λ / 16 and a pitch of λ / 4 are bent inward, and the inner plate 200 and the outer plate ( A short surface 203 having an impedance of " 0 " is integrally formed between 201, and a predetermined opening portion 202a is directed from the middle of the slits 202 to the bottom of the outer plate body 201. Is formed, the vertical width of the opening 202a and the horizontal length of the slits 202 are It is formed at regular intervals.

Between the slits 202, rectangular cutouts 202b having a period equal to the width of the openings 202a extend to the lower part of the slits 202.

In addition, a rectangular through hole 202c is formed in the slits 202 such that vertical and horizontal widths have a predetermined period, and a ferrite rubber 204 is attached to an upper surface of the silit 202 of the outer plate body 201. A choke seal 205 having a width of λ / 4 and having a predetermined length is formed inside.

In this way, the high frequency shielding device in the conventional microwave oven configured is surrounded by the outer plate body 201 between the dust oven front plate 104 and the inner plate body 200 of the door frame, and the choke seal 205 is formed. When the structure of the part is expressed by the transmission line, the high frequency of the transmission line is expressed by the following equation.

(N = 0, ± 1, ± 2 ……) … … … … … … … … … … … … … … … (Equation 1)

Here, Ko = 2π / λ, and b represents the interval between the oven fronton plate 104 and the inner plate body 200.

At this time, if the interval b between the oven front plate 104 and the inner simplified body 200 is small, the T mode (Transverse Electric Wave) and the T mode (TM: Transverse Magnetic V've) are blocked. Transmission is only possible in TEM mode (TEM. Transverse Electric Magnetic Wave).

That is, in the TEM mode, since the characteristic impedance of the parallel transmission line is proportional to the interval b * μ / ε, heating is performed by making the interval b very small or increasing the ε value (dielectric constant). High frequency leaking from the seal 8 can be reflected

Where μ is the permeability.

In addition, if the short surface 203 of the outer plate body 021 forming the choke seal 205 is tested with an impedance of O (Zero), assuming that the choke seal 205 itself is a transmission line, as shown in FIG. Similarly, the input impedance Zin as a point away from the load ZL by a length L can be expressed as follows.

… … … … … … … … … … … … … … … … (Equation 2)

Here, Zo is a characteristic impedance of a transmission line, and β is a value determined by the structure of the transmission path as a propagation constant.

Assuming Z _L = 0 in Equation 2, input impedance Zin = j Zo tanB _L , where L = λg / 4, Zin becomes infinite (∞), and when L = λg / 2, Zin = It becomes 0 and becomes a short.

Thus, as in the second diagram, the high frequency energy inside the heating chamber 102 starts at point A and is point C through the gap b of the contact surface 20a of the inner plate body 200 which is in contact with the oven front plate 104. In the case of leaking in the air, the leaked high frequency energy is introduced into the choke seal 205 with a path in the B direction at the point D at the center portion of the gap b between the oven front plate 104 and the inner plate body 200. The impedance of the D point can be made infinite (∞) by placing the D point of the directional point at a point λg / 4 away from the short surface 203 having an impedance of "0".

As a result, the choke seal 205 causes resonance, and the resonance source high frequency energy is reflected toward the heating chamber 102 by the slits 202 bent inwardly perpendicular to the outer plate body 201, and thus to the C direction. Leakage of high frequency energy is prevented.

The high frequency energy other than the high frequency energy reflected by the heating chamber 102 is absorbed by the ferrite rubber 204 which is a wave absorber, and the high frequency energy is shielded again.

However, such a high frequency shielding device in a conventional microwave oven uses a microwave oven for a long time, and when the gap between the inner plate body of the choke seal and the oven front plate of the heating chamber is widened, the high frequency energy is not only in the TEM mode. Leakage of TE mode or TE mode rod and high frequency energy to the outside increases locally, and the cost of the product increases due to the use of expensive ferrite rubber at the same time as the choke seal structure, which has a width of λg / 4. In addition, as the length and width of the choke seal became thicker, the thickness of the door itself became thicker, thereby simplifying the product and greatly improving the weight of the choke seal.

Accordingly, the object of the present invention is to make the choke seal with a thickness of the door and a period of λg / 4 thin and short, as well as without using a ferrite rubber mounted between the choke seal and the oven front plate to absorb high frequency energy. It is to provide a high frequency shield of the microwave oven to effectively block the high frequency energy leakage to the outside through the gap between the oven front plate and the door of the heating chamber of the microwave oven,

As a means for achieving the object of the present invention, the outer plate formed at the edge of the door frame is bent inwardly with a predetermined period, and the bent surface formed in the vertical and horizontal direction at one end of the short surface of the inner plate First shielding means for shielding high frequency energy in the X direction leaking out of the heating chamber to the outside, and the first shielding means, the outer shielding body and the inner plate body, respectively divided by the Z-direction component leaking out of the heating chamber. It is achieved by the second shielding means for shielding the high frequency energy in the first and second, and will be described in detail below with reference to the accompanying drawings of the present invention.

FIG. 5 is a cross-sectional view of a door choke seal structure for a shield in a microwave oven according to the present invention, and FIG. 6 is a perspective view of a door choke structure for high frequency shielding of FIG. 5, which is integrated with a door frame (Mitoshi in the drawing). An inner plate body 301 formed in contact with the oven float plate 300, a short surface 302 bent in a horizontal direction at an end of the inner plate body 301, and a short surface of the inner plate body 301. (302) first shielding means (315) for shielding the high-frequency energy in the X-direction leaked to the outside in the heating chamber 303 by forming a pitch in the vertical and horizontal direction having a pitch of λg / 4 at the end; The outer plate body 304 is formed in a line with the inner plate body 301 in a predetermined length and the end is bent vertically downward to have the slits 305, and the outer plate body 304 and the inner plate body 301. By the first shielding means 315 between Second shielding means for shielding the high-frequency energy of the Z-direction component leaked to the outside in the heating chamber 303 to the first and second, and the slits 305 and the first shielding means of the outer plate (304) 315 and the high frequency choke cover 306 mounted in a straight line and the upper end of the five-minute front plate 300 protrudes to leak into the gap when in contact with the slits 305 of the outer plate body 304 It consists of a projection 300a for shielding energy, and a leak check probe 307 for detecting high frequency energy leaking between the slits 305 of the outer plate 304 and the projection 300a of the open front plate 300. do.

As shown in FIG. 7, the first shielding means 315 is vertically bent upwardly at an end portion of the short surface 305 of the inner plate body 304 to be vertically bent to form an oven front plate. A first stepped portion 308 in contact with 300, a first bent portion 309 bent horizontally at an end of the first stepped portion 308 and having a predetermined period, and the first bent portion ( The second stepped portion 3110 that is bent vertically upward with a constant period at the end of 309 and the second bent portion 311 that is bent in the horizontal direction with a constant period at the end of the second stepped portion 3101. And a cutout 312 cut between the second stepped portion and the stepped portion.

The second shielding means is divided by the first shielding means 315 between the outer plate body 304 and the inner plate body 301, respectively, and the high-frequency energy of the Z-direction component leaked to the outside from the heating chamber 303. The first choke seal 313 shielding the primary and the first high frequency of the remaining choke seal 313 is divided by the first shielding means 315 is shielded from the first choke seal 313 The second choke seal 314 shields energy again.

Thus, the operational effects of the present invention configured as described in detail with reference to FIGS. 5 to 7 as follows. First, as shown in FIG. 5, when the flow of the high frequency energy formed from the heating chamber 303 is displayed as a vector, the components may be represented as X components, Y components, and Z components.

At this time, the cause of high frequency leakage is a high frequency leakage to the X component and the Z component.

In order to turn such a high frequency energy component, a choke structure for shielding the leakage of high frequency energy in the X direction, that is, the first shielding means 315 and the second shielding means for preventing the leakage of high frequency energy in the Z direction, The first and second choke seals 313 and 314 constituted by the outer plate 304, the inner plate 301 and the first shielding means 315 are required.

The process of shielding the high frequency energy of the X-direction and Z-direction components by the first shielding means 315 and the second shielding means is as follows.

As shown in FIGS. 6 and 7, the first and the first shielding means 315 of the first shielding means 315 are bent at an end portion of the short surface 302 of the inner plate body 301 integrally formed with the door frame, and each tooth is formed at a period of? G / 4. The second step portion 308, 310, the first and second bent portions 309, 311 and the cut portion 312 acts as a band stop filter for the high frequency energy traveling in the X direction. Therefore, the high frequency energy leakage in the X-axis direction is blocked.

That is, high frequency energy due to the difference in impedance according to the periodic shape of the second stepped portion 310, the first and second bent portions 309 and 311 and the cutout portion 312 of the first shielding means 315. Phase difference occurs, and thus attenuation of high frequency energy occurs.

In addition, the fringing capacitance generated by the first shielding means 315 having the periodic structure complements the role of the filter, and the second stepped portions 310, 1, and 1 of the first shielding means 315 are provided. Each of the first to fourth periods T1 to T4 of the second bent portions 309 and 311 and the cutout portion 312 has a predetermined length.

The acting of the periodic first shielding means 315 as a filter can be described as modeling of a periodic transmission line as shown in FIG.

That is, the modeling of FIG. 12 is equivalently periodically performed at intervals of the distance T of the impedance ZA.

As shown in the characteristics of the phase constant β and the frequency f, that is, β-f, the transmission line has a wave band and a cut band, that is, a propagation band and a blocking band. It has the characteristic of appearing in mutual interaction.

Therefore, in order to block the radio wave leakage in the X direction by using such a relationship, the line condition may be selected so that the frequency of the wave is included in the frequency range of the blocking region.

In this case, the blocking region is determined by the period T of one pitch of the first shielding means 315, the impedance Z _A , and the characteristic impedance Zo of the line.

In addition, the second shielding means for shielding the high-frequency energy leaking in the Z direction is the first and second choke seals (313, 315) having a period of λg / 4 serves as a main role from the heating chamber 303 The high frequency energy flow is equal to the fifth degree.

That is, the first stepped portion 308 of the first shielding means 315 is formed in the inner plate body 301 in which the high frequency energy inside the heating chamber 303 is in contact with the oven front plate 300 starting at the point A. When leaked to point C through the minute gap between the slits 305 bent vertically downward to the end of the outer plate body 304, the leakage high frequency energy of the oven front plate 300 and the inner plate body 301 A short surface 302 having an impedance of "0" is assumed to flow into the first choke seal 313 and the second choke seal 314 of the second shielding means with a path in the B direction at the center point D at a minute interval. By locating the point D of the directional point at a point λg / 4 away from, the impedance of the point D can be made infinite.

Accordingly, the first and second choke seals 313 and 314 cause resonance, and the resonant frequency energy is directed toward the heating chamber 303 by the slits 305 bent inwardly perpendicular to the outer plate 304. By being reflected, leakage of high frequency energy in the C direction is prevented.

In particular, in the above, the first and second choke seals 313 and 314 may include the first and second stepped portions 308 and 310, and the first and second bent portions 309 of the first shielding means 315. As in 311, a two-stage bent shape becomes a main element.

That is, the first shielding means 315 is bent in two stages, while the choke length is shorter than the existing λg / 4 length, while the function plays the role of λg / 4 choke.

In other words, this effect is made possible by the role of the fringing capacitance at the bent (stepped) portion of the first shielding means 315.

In order to manage dimensions of the first and second stepped portions 308 and 310 of the first shielding means 315, the first stepped portion 308 is L1 and the second stepped portion 310 is L2. Assume that the dimension can be determined by the following equation.

β ₁ λ ₁ + β ₂ λ ₂ = π / 2

In the above description, β ₁ = β ₂ = 2π / λ, and π / 2 represents the point where the impedance inversion occurs.

In addition, the slits 305 bent downwardly perpendicular to the ends of the outer plate body 304 and the first step portion 308 of the first shielding means 315 respectively function as secondary and secondary capacitive seals. have.

The protrusion 300a protruding from the upper end of the oven front plate 300 serves to block a path of high frequency energy leaking in the C direction.

In this way, the first and second choke seals 313 and 314, the first shielding means 315, and the primary and secondary capacitive seals having a period of? .

8 to 11 are perspective views showing another embodiment of the first shielding means of the present invention, the operation of which is the same as that of the fifth and sixth.

That is, in the first shielding means 315 of FIG. 8, the first bent portion is sequentially smaller in the first stepped portion 308 vertically bent upwardly at the end of the short surface 302 of the inner plate body 301. 309, the second stepped part 310, and the second bent part 311 are formed by bending in two stages. In the first shielding means 315 of FIG. 9, the first stepped part 308 is provided with the first stepped part 308. The periods of the bent portion 309 and the second bent portion 311 are formed in the same manner, and are formed of the second stepped portion 310 larger than the periods of the first and second bent portions 309 and 311.

In addition, in the first shielding means 315 of FIG. 10, the first bent portion 309 having the same period is bent upwardly to the first stepped portion 308 having a predetermined period, and the first bent portion 309 is formed. The second step portion 310 having a smaller period than this is vertically bent at the center thereof.

In the first shielding means 315 of FIG. 11, the first bent portion 309 and the second stepped portion 310 having a larger period than the first stepped portion 308 having the predetermined period have the same period. do.

By combining these cycles in a certain dimension, it is possible to effectively block the leakage of high frequency energy leaking in the X direction.

As described in detail above, according to the present invention, the high frequency energy leaking in the X direction and the high frequency energy leaking in the Z direction are simultaneously blocked by the λg / 4 choke seal structure and the first shielding means having a constant period. A more reliable choke seal configuration is achieved through double capacitive seals with primary and secondary capacitive seals.

In addition, it is possible to prevent perfect high frequency energy loss without using expensive ferrite love that has been used in the past, so that the cost increase can be greatly suppressed during mass production of the product, and the stepped portion of the two-stage bending can be formed. The λg / 4 choke seal function is the same, but the choke length, width and thickness are greatly reduced, making it possible to design more compactly than the existing door structure, and to realize the overall slimness of the door. In addition, there is an effect that can be expanded.

Claims (9)

An inner plate body contacting the oven front plate, a short surface formed by bending in the horizontal direction at the end of the inner plate body, and one pitch at the end of the short surface of the inner plate body having a period of λg / 4 in multiple stages in the vertical and horizontal directions. A first shielding means that is bent to shield high frequency energy in the X direction, which is leaked out from the heating chamber, and an outer plate body formed in a line with the inner plate body in a predetermined length in a straight line and having an end portion bent vertically downward; And second shielding means which are respectively formed by the first shielding means between the outer plate body and the inner plate body to shield the high-frequency energy of the Z-direction component leaked to the outside from the heating chamber in a first and second order, and the outer plate body. A high frequency shielding device for a microwave oven, comprising: a slit and a choke cover mounted in a line with the first shielding means. The first step of claim 1, wherein the first shielding means has a first step in contact with the oven front plate and is bent upwardly vertically with a predetermined length in the horizontal direction at the end of the short surface of the inner plate body, and at the end of the first step portion. A first bent portion that is bent horizontally and has a predetermined period Tl, a second stepped portion that is bent vertically upward with a predetermined period T2 at an end portion of the first bent portion, and an end portion of the second stepped portion. High frequency shielding of the microwave oven, characterized in that the second folded portion bent in the horizontal direction with a constant period (T3) and the cut portion having a constant period (T4) formed between the first bent portion and the bent portion Device. 2. The first choke according to claim 1, wherein the second shielding means is divided by the first shielding means between the outer plate and the inner plate to shield the high frequency energy of the Z-direction component leaking to the outside from the heating chamber. A high frequency of a microwave oven comprising a seal and a second choke seal, which is formed by a first shielding means above the first choke seal and shields the remaining high frequency energy shielded from the first choke seal again. Shield. The microwave shielding apparatus of claim 1, further comprising a protrusion at an upper end of the oven front plate to prevent leakage of high frequency energy. 3. The period Tl (T3) of the first and second bent portions of the first shielding means is one half of the period of the second stepped portion T2, and the period T4 of the cutout portion is the first. And a period (T4) equal to the period (T1) and the period (T4) of the second bent portion, so that one pitch is configured to have a period (T) of λg / 4. 3. A cycle according to claim 2, wherein the periods of the first, second bent portions, the second stepped portions, and the cutout portions of the first shielding means have T4 <T1 = T3 <T2 and one pitch is a period T of lambda g / 4. High frequency shield of microwave oven, characterized in that the configuration. 3. The cycle according to claim 2, wherein the periods of the first bent portion, the second stepped portion and the second bent portion of the first shielding means have T1> T2> T3, and the period T4 of the cutout portion is equal to the period T3 of the second bent portion. A high frequency shield of a microwave oven, wherein the pitch is equally configured to have a period T of? G / 4. 3. The cycle according to claim 2, wherein the periods of the first bent portion, the second stepped portion, and the second bent portion of the first shielding means have T1 = T2> T3, and the period T4 of the cutout portion is equal to the period T3 of the second bent portion. A high frequency shield of a microwave oven, wherein the pitch is equally configured to have a period T of? G / 4. 3. The period of the first bent portion, the second stepped portion and the second bent portion of the first shielding means is smaller than T1 < T2 = T3, and the period T4 of the cutout portion is equal to the period Tl of the first bent portion. A high frequency shield of a microwave oven, characterized in that the same pitch is configured to have a period T of? G / 4.