KR920010585B1 - Microwave sealing structure for microwave oven - Google Patents

Abstract

The plate comprises a base substance of rubber or organic compound, a conductive substance of rectilinear or flake shape, and ferrite powder. The conductive substance has an aspect ratio of 1.5 to 4 and long axis length of 0.1 to 0.5 mm. The weight ratio of the conductive substance and the ferrite powder are 0.01-10 % and 60-80 % respectively. The conductive substance is carbon fiber or a stainless steel wire.

Description

High Frequency Leakage Plate Of Microwave Oven

1 is a perspective view of a microwave oven.

2 is an exploded perspective view of the door of FIG.

3 is an explanatory view showing the operating principle of the high frequency leakage preventing plate of the present invention.

4 is an exemplary view showing the installation state of the adapter for measuring the dielectric constant, permeability of the high frequency leakage preventing plate.

5 is an exemplary view showing a test position of the apparatus of the present invention and the conventional apparatus.

* Explanation of symbols for the main parts of the drawings

1: body 2: door

3: see-through window 4: cover plate

5: high frequency leakage preventing plate 6: groove

7: see-through mounting bracket 8: mounting bracket

9: high frequency guide plate 10: conductive thin wire or flake

11,11 ′: Waveguide adapter 12,12 ′: Connector for power line connection

The present invention relates to a high frequency leakage preventing device for preventing the high frequency generated in the magnetron of the microwave oven called microwave oven to leak outside of the heating chamber, and in particular, it can prevent the high frequency leakage of the outside of the heating chamber. High frequency leakage preventing plate.

In general, the microwave oven is a convenient kitchen vessel for cooking various foods with the heat generated by irradiating the high frequency generated from the magnetron to the food in the heating chamber.

However, the microwave oven uses high frequency harmful to the human body, so it should be prevented from leaking to the outside of the heating chamber.

In particular, the microwave oven is most likely to leak a high frequency in the distance between the main body and the door due to its structural characteristics, so special consideration is required for this part.

In view of such a situation, various apparatuses for preventing the high frequency leakage from the gap between the main body and the door of the microwave oven have been proposed.

First, US Pat. No. 4,103,681 prevents leakage of high frequency by inserting a conductive rubber between the door of the main body of the microwave oven.

Second, in US Patent No. 3,866,009, a ferrite radio wave absorber is mixed with rubber or plastic to make a radio wave absorption plate, and the radio wave absorption plate is inserted between the body and the door of the microwave oven to prevent high frequency leakage.

Third, in Korean Patent Publication No. 87-837, a conductive wave absorber is made by mixing a ferrite body and a carbon powder in a binder, and the conductive wave absorber is inserted between the main body and the door of the microwave oven to prevent leakage of high frequency. It was.

Fourth, Korean Patent Publication No. 88-122 provided an uneven structure at the edge of the door of the microwave oven, and the high frequency is reflected from the uneven structure to cancel each other to prevent leakage of the high frequency.

Fifthly, Japanese Patent Publication No. 63-34639 mixed ferrite powder and long-axis conductive fiber to make a radio wave absorber, and inserted the wave absorber between the body and the door to prevent high frequency leakage.

However, in the first and third devices, at least 20% by weight of conductive carbon, which is a conductive material, must be added to rubber or plastic in order to engage the conductive radio wave absorber. There was a problem that the productivity is lowered due to poor sex.

In addition, in the second apparatus, a problem of heat resistance is caused in rubber or plastic, and a large amount of expensive radio wave absorber has to be added.

In addition, in the fourth apparatus, there is a concern that the shape of the uneven structure changes due to heating or long-term use, which may lower the leakage preventing performance of high frequency, and lower the reliability of the product.

In addition, in the fifth apparatus, the addition of long-axis metal fiber lowered the workability of the material, the injection property, and the extrudability, and the long-term metal fiber was often captured on the surface. There was a downside to changing.

In addition, there was a disadvantage that it is difficult to evenly distribute the metal fibers of the long axis.

The present invention has been made in view of the above-mentioned conventional drawbacks, and has an object to provide a high frequency leakage preventing plate having excellent high frequency shielding performance, improved thermal conductivity, and excellent workability.

An object of the present invention is to provide a rubber and polymer compound having an aspect ratio of 1.5 or more and 4.0 or less, a major axis of 0.1 mm or more and a 0.5 mm or less conductor such as carbon fiber, aluminum, zinc and It is achieved by adding 0.01% by weight or more to 10.0% by weight of stainless steel thin wire or flake, and adding ferrite powder by 60% to 80% by weight, and then mixing them in a constant ratio.

In the present invention, the conductive thin wire or the flake added to the organic chemical has alignment in the extrusion or injection process, which is a manufacturing process, and this orientation maximizes the high frequency shielding effect.

This is because the conductive thin wires and flakes added to the rubber and the organic polymer compound contribute to the reflection of the high frequency at which they enter, and the high frequency is shielded by contributing to the absorption of the high frequency at which the ferrite powder is incident or reflected.

That is, as the distance between the conductive thin wires and the flakes is smaller than 1/4 of the incident wave wavelength, the advancing high frequency becomes longer in the high frequency absorber under the influence of the conductive thin wires or flakes, and thus the ferrite powder It also increases the absorption effect by the high frequency shielding effect.

Accordingly, the conductive thin wires and the flakes having the orientation are narrower than the spherical conductors and contribute more effectively to the reflection of the incident high frequency wave.

The amount of conductive thin wire or flake added to the rubber or organic compound showed excellent shielding effect between 0.1% and 10.0% by weight. If the amount is less than this, there is almost no high frequency shielding effect. Workability has been lost and productivity is reduced.

The aspect ratio of the conductive thin wire or flake added to the rubber or organic compound showed excellent shielding effect between 1.5 and 4.0, but if smaller than this, the orientation was almost spherical, and if it was larger, the orientation was lowered and the shielding effect was decreased. fell.

In addition, the ferrite powder also showed an excellent shielding effect when added between 60% and 80% by weight, and the addition amount was less than the high frequency shielding effect, the addition of more than 80% by weight worsens the workability, relatively high As the amount of added ferrite increased, it was not economically desirable.

As described above, the high frequency shielding effect was measured after manufacturing the high frequency leakage preventing plate and the excellent high frequency shielding effect was also obtained.

Hereinafter, with reference to the accompanying drawings will be described in detail.

FIG. 1 is a perspective view of the microwave oven, and as shown therein, a high frequency leakage preventing plate 5 is installed at the inner edge of the door 2, that is, the periphery of the viewing window 3, which is coupled to the main body 1 of the microwave oven. .

FIG. 2 is an exploded perspective view of the door of FIG. 1, and as shown therein, a see-through window mount 7 is formed with a groove 6 inside the door 2, and a see-through window 3 is provided on the see-through window mount 7. In addition to the screw is coupled to the mounting hole 8 is installed thereon, by the mounting hole 8 is installed the high frequency leakage preventing plate 5 in the groove portion 6 and the high frequency guide plate 9 is installed The cover plate 4 is installed thereon.

The high frequency leakage preventing device configured as described above is transmitted when the high frequency is applied to the horizontal surface portion of the high frequency guide plate 9 and the high frequency is changed through the front end of the high frequency guide plate 9 to the groove 6 of the door 2. Accordingly, the high frequency transmitted to the groove part 6 and the high frequency reflected from the groove part 6 cancel each other, and at this time, the high frequency that is not canceled and exits into the gap between the door 2 and the main body 1 is a high frequency absorber. It is absorbed by the high frequency leakage preventing plate 5 to prevent leakage of the high main plate.

3 is an explanatory view showing the principle of operation of the high frequency leakage preventing plate of the present invention, as shown in the figure, by forming a conductive wire or a flake 10 at a predetermined interval on the high frequency leakage preventing plate 5, In addition, the flakes 10 increase the high-frequency propagation distance (arrow L) from the high-frequency leakage preventing plate 5, thereby increasing the high-frequency absorption rate.

4 is an exemplary view showing the installation state of the adapter for measuring the dielectric constant and permeability of the high frequency leakage preventing plate using the waveguide, and the high frequency leakage preventing wave 5 between the adapters 11 and 11 'of the two waveguides. The sample is placed to measure permittivity and permeability.

Here, reference numerals 12 and 12 'denote connectors for transmission line connection.

5 is an exemplary view showing the test position of the present invention and the conventional apparatus, and the outside predetermined positions P1, P2, P3, and P4 of the door 2 are used as test positions.

On the other hand, the dielectric constant, permeability and attenuation rate representing the electrical and magnetic properties of the high frequency leakage preventing plate 5 can be expressed by the following equation.

However, since the dielectric oil and permeability are all the same as air, the attenuation rate (α) per unit length can be expressed by the following equation.

Where λ _o = high frequency wavelength in the free space

1INP = -8.67dB

On the other hand, in measuring the permittivity, permeability, and attenuation rate by the method using the transmission line, a high frequency leakage preventing plate 5, which is a sample, is inserted between the adapters 11 and 11 'of the waveguide as shown in FIG. Measurements are made after connecting to the connectors 12 and 12 '.

Here, the input admittance Y _OC at opening and the admittance Y _SC at short circuit are expressed as follows.

In addition, permittivity (ε _r ) and permeability (μ _r ) are expressed by the following equation.

Λ _O : wavelength in free space, λ _C : wavelength in waveguide

As can be seen from the above theoretical explanation, as the attenuation factor α increases, the high frequency shielding effect of the high frequency leakage preventing plate 5 is improved.

Example 1

A high frequency absorber was prepared by kneading 1% by weight of zinc flakes having an aspect ratio of 1.5 and a length of 0.2 mm and 80% by weight of ferrite powder with 19% by weight of a binder. Here, high frequency absorption characteristics, workability during kneading and molding, high frequency leakage thermal conductivity and heat shrinkage are shown in Comparative Tables 1,2,3 and 4 below.

Example 2

A high frequency absorber was prepared by kneading 5% by weight of carbon fiber having an aspect ratio of 3 and 0.4 mm in length and 70% by weight of ferrite powder with 25% by weight of a binder. Here, high frequency absorption characteristics, workability during kneading and molding, high frequency leakage, thermal conductivity, and heat shrinkage are shown in Comparative Tables 1,2,3, and 4 below.

Example 3

A high frequency absorber was prepared by kneading 10 wt% of stainless fine wire and 60 wt% of ferrite powder having an aspect ratio of 4 and a long axis of 0.5 mm with 30 wt% of a binder. Here, high frequency absorption characteristics, workability during kneading and molding, high frequency leakage, thermal conductivity, and heat shrinkage are shown in Comparative Tables 1,2,3, and 4 below.

Comparative Example 1

80% by weight of the ferrite powder was kneaded with 20% by weight of the binder by the method of US Patent No. 3,866,099 to prepare a high frequency absorber. Here, high frequency absorption characteristics, workability during kneading and molding, high frequency leakage, thermal conductivity and thermal shrinkage are shown in Comparative Tables 1,2,3 and 4.

Comparative Example 2

A high frequency absorber was prepared by kneading 55% by weight of ferrite powder, 23% by weight of 50 μmψ × 2 mml brass wire by the method of Japanese Patent Publication No. 63-34639, and a binder. Here, high frequency absorption characteristics, workability during kneading and molding, high frequency leakage, thermal conductivity and thermal shrinkage are shown in Comparative Tables 1,2,3 and 4 below.

[Comparison Table 1]

Where metrics 1-7,

1: μ '(real number of complex permeability)

2: μ ″ (imaginary value of multiple permeability)

3: ε '(real value of complex dielectric constant)

4: ε ″ (imaginary value of plural dielectric constant)

5: decay rate at a frequency of 2.45 GHz [dB]

6: Poor kneading for 1 hour after starting kneading operation at 22 revolutions of kneading machine (kg)

7: Molding injection 1 rotation time [seconds] of molding T2.5mm × W20mm × ℓ50mm in molding of injection machine

From the results of Comparative Table 1, it can be seen that the high frequency absorption characteristics of the high frequency absorber according to the present invention, that is, the attenuation rate is much superior to the existing high frequency absorber, and the workability during kneading and molding is also very good. Comparative Table 2 below shows a result of measuring a high frequency shielding device using a high frequency absorber manufactured by the method of Examples 1, 2, 3 and Comparative Examples 1, 2, and measuring the high frequency leakage preventing effect of the high frequency shield. It is seen. The measuring method replaces the high frequency leakage preventing plate 5, which is the high frequency absorber of FIG. 2, with the high frequency absorber made by the methods of Examples 1, 2 and 3 and Comparative Examples 1, 2, and the main body of the microwave oven 1 of 275 cc of distilled water was added to the heating chamber, and the power was supplied while the door 2 was closed to operate the microwave oven, and the high frequency leakage was measured at the positions P1, P2, P3 and P4 of FIG.

[Comparison Table 2]

From the results of Comparative Table 2, it can be seen that the high frequency leakage preventing device according to the present invention has a much higher frequency shielding effect than the existing high frequency leakage preventing device. Particularly, in Example 3, the thickness of the high frequency absorber is about 50%. In case of reduction, the high frequency shielding effect was shown to be similar to that of the high frequency leakage of the comparative example.

Comparative Table 3 shows the results of measuring the thermal conductivity effect of the high frequency absorber made by the method of Examples 1,2,3 and Comparative Examples 1,2. In the measuring method, after heating one side of a sample with 60 degreeC heat, the other temperature was measured after 30 second.

[Comparison Table 3]

It can be seen from the comparison table that the thermal conductivity of the high frequency absorber according to the method of the present invention is superior to that of the existing high frequency absorber. The high thermal conductivity allows the heat generated in the process of absorbing the high frequency of the high frequency absorber to the outside easily. It means that the effect is high.

Comparative Table 4 shows the thermal contraction rate of the high frequency absorber made by the method of Examples 1,2,3 and Comparative Examples 1,2. The measurement method was placed in a thermo-hygrostat set at 180 ° C., after 500 hours, and left for 24 hours at room temperature to measure the change in dimensions.

[Comparative Table 4]

From the results of Comparative Table 4, it can be seen that the thermal contraction rate of the high frequency absorber according to the present invention is smaller than that of the existing high frequency absorber, which is caused by heat shrinkage when the high frequency absorber of the present invention is used as a high frequency leakage preventing plate of a microwave oven. The small shape deformation means that the high frequency leakage prevention effect can be maintained.

As described in detail above, the high frequency leakage preventing plate of the present invention has a higher high frequency leakage preventing effect, good workability during kneading and molding, high thermal conductivity, and low thermal contraction rate at high temperature, as compared with the existing high frequency absorber. It is possible to reliably prevent the high frequency leakage of the microwave oven and to improve the reliability of the product.

Claims (7)

To the rubber or organic compound, add 0.01-10% by weight of a linear or flake type conductor having an aspect ratio of 1.5-4 and a major axis of 0.1-0.5mm, and add 60-80% by weight of ferrite powder, A high frequency leakage preventing plate of a microwave oven, wherein the microwave oven is mixed and arranged in one direction. The high frequency leakage preventing plate of claim 1, wherein the conductor is a zinc flake having an aspect ratio of 1.5 and a long axis of 0.2 mm. The high frequency leakage preventing plate of claim 1, wherein the conductor is a carbon fiber having an aspect ratio of 3 and a long axis of 0.4 mm. The high frequency leakage preventing plate of claim 1, wherein the conductor is a stainless steel wire having an aspect ratio of 4 and a long axis of 0.5 mm in length. 3. The high frequency leakage preventing plate of the microwave oven according to claim 2, wherein 1 wt% of the zinc flake is added and 60 wt% of the ferrite powder is added. 4. The high frequency leakage preventing plate of the microwave oven according to claim 3, wherein 5% by weight of carbon fiber and 70% by weight of ferrite powder are added. 5. The high frequency leakage preventing plate of the microwave oven according to claim 4, wherein 10 wt% of the stainless fine wire is added and 60 wt% of the ferrite powder is added.

Images