KR100302915B1 - Waveguide of microwave oven - Google Patents

Abstract

PURPOSE: Opening sides of a waveguide is formed as a plurality of slots, and a dielectric material is mounted within the waveguide for passing the slots and moving sidewise in the waveguide. The direction of an electromagnetic wave changes accordingly, thereby improving evenly heating performance. CONSTITUTION: A magnetron generates an electromagnetic wave. The electromagnetic wave is introduced to a cavity through a waveguide(8) in a microwave oven. The waveguide(8) has an opening side of slots(10). A dielectric material(11) is mounted in the waveguide to change phase between the slots(10). The dielectric material(11) is mounted lengthwise in the waveguide, and passes the slots(10), and moves sidewise in the waveguide.

Description

Microwave waveguide

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to microwave ovens, and more particularly, to a waveguide structure for guiding electromagnetic waves generated from a magnetron into a cavity.

Referring to a schematic configuration of a general microwave oven, as shown in FIG. 1, a magnetron 1 for generating electromagnetic waves, a waveguide 2 for guiding electromagnetic waves generated from the magnetron 1 into the cavity 3, and the It is composed of a rotating plate (4) placed on the lower surface of the cavity (3) on which the food (5) is placed.

In addition, the waveguide 2 is formed with a fixed opening 7 for transmitting electromagnetic waves generated from the magnetron 1 to the cavity 3 as shown in FIG. 2.

Looking at the operation for heating the food of the conventional microwave oven having such a structure, first, the electromagnetic waves generated in the magnetron (1) enters the cavity (3) through the waveguide (2) is absorbed by the food (5) to cook the food. do. At this time, the electromagnetic waves inside the cavity are reflected on the walls and foods of the cavity, causing constructive and destructive interference, and forming standing waves in the cavity. Therefore, the electromagnetic fields in the cavity are not uniformly distributed and strong and Weak spots are created. Therefore, a phenomenon in which the food to be heated is not heated evenly occurs. Therefore, in order to prevent this, the food is placed on the rotating plate 4 and the rotating plate is rotated or by using a stirrer 6 shaped like a pinwheel so that the food waves are uniformly heated so that the food is uniformly heated.

When a load (food) is determined in a conventional microwave oven, the distribution of the electromagnetic field in the cavity becomes constant regardless of time and is not uniform. Therefore, a method of obtaining a relatively uniform heating performance using a method of rotating a load to be heated using a rotating plate as described above is mainly used, but the effect is limited. In addition, although the shape of the common cavity is a rectangular parallelepiped, there is a problem that the size of the load that can be heated when using the rotary plate is limited because of this, and thus the entire space of the cavity cannot be utilized.

The present invention has been invented to solve the problems of the prior art as described above to form an opening surface of the waveguide into a plurality of slots, and having a dielectric inside the waveguide that passes through the slot area and moves in the transverse direction of the waveguide. By configuring to change the direction of the electromagnetic wave, an object is to provide a microwave oven with improved uniform heating performance.

1 is a microwave oven structure diagram according to the prior art.

2 shows a conventional waveguide structure,

(A) Front section view.

(B) is side sectional view.

3 is a structural diagram of a waveguide of the present invention.

4A is a diagram showing two isotropic radiators and a radiation pattern.

5 is an arrangement diagram of a plurality of isotropic radiators.

Figure 6 is an embodiment of a radiation pattern.

7 is another embodiment of a radiation pattern.

8 is a cross-sectional view of the waveguide of the present invention.

9 is a longitudinal sectional view of the waveguide of the present invention.

10 is one embodiment of an electromagnetic radiation pattern relative to the location of the dielectric.

11 is another embodiment of an electromagnetic radiation patch for the location of a dielectric.

*** Explanation of symbols for the main parts of the drawing ***

1: magnetron 2: waveguide (conventional)

3: cavity 4: rotating plate (conventional)

6: stirrer 8: waveguide (invention)

9: magnetron antenna 10: slot

11 Dielectric 12 Transfer Screw

13: motor

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

As shown in FIG. 3, the waveguide configuration of the present invention is composed of an opening surface in which a plurality of slots 10 are arranged, and a dielectric 11 or the like installed in the waveguide region so that the position can be changed in the transverse direction. Each slot 10 operates as one antenna, and the waveguide and the plurality of slots 10 constitute a kind of array antenna again. The dielectric 11 in the waveguide determines the electrical length, that is, the phase difference between the slot antennas, and as the position of the dielectric in the waveguide changes, the phases between the slots change, resulting in the radiation pattern of the entire array antenna. Will change.

The principle of the basic array antenna is as follows.

First, a radiation pattern formed by two isotropic radiators spaced apart by the distance L shown in FIG. 4A can be obtained as follows. By reversible theorem the radiation pattern of these two emitters is also the same as the receiving pattern. If the center point of two points is taken as the phase reference, the electric field for each Ø direction

E = E ₁ e ^{-jψ / 2} + E ₂ e ^{jψ / 2}

Is given by If E ₁ = E ₂ = E ₀ ,

to be. When L = λ / 2, E = 2E ₀ cos (π / 2 sinØ), and a radiation pattern is illustrated in FIG. 4B.

In the case of a one-dimensional array of a plurality of isotropic radiators having the same amplitude as shown in FIG.

ψ = βdsin∅ + δ

E = E (e ^jψ + E ₂ e ^j2ψ + ⃛ + e ^jnψ )

Where δ is the phase difference equally given between each emitter. That is, if a phase difference of 90 degrees is provided between each radiator, the phase difference between 1 and 2 is 90 degrees, 180 degrees between 1 and 3 times, and 270 degrees between 1 and 4 times.

Centering the array as the reference plane of the phase

Becomes Therefore, changing the phase difference between each radiator, δ, changes the radiation pattern of the entire array, which means that the main radiation direction of the electromagnetic wave is changed. Fig. 6 shows radiation patterns in the case of n = 10, d = λ / 4, and δ = 45 degrees, but it can be seen that the main radiation direction is inclined at about 30 degrees from the center.

If each radiator is not isotropic and has a constant radiation pattern like a slot antenna, the equation of the radiation pattern may be substituted instead of E ₀ in the above equation.

In the present invention, a plurality of slots 10 are formed in a one-dimensional array on the surface of the waveguide. The spacing between the slots is fixed, and the phase difference between the slots is also fixed if the wavelength in the tube in the waveguide is constant. Therefore, the radiation pattern of the entire slot array antenna in this case is also fixed.

However, the dielectric 11 in the waveguide of the present invention is inserted just to change the phase difference between each slot. The insertion of a dielectric means a change in the wavelength in the tube, which in turn refers to a change in electrical length, or phase, between slots.

The width of the waveguide body 8 of the present invention is designed in TE ₁₀ mode as in conventional waveguides or in most other cases. Thus, in the absence of the dielectric 11, the electric field near the center of the waveguide is the strongest and weakens toward the side wall. At this time, when the dielectric is inserted into the waveguide, the transmission speed of electromagnetic energy in the dielectric is slower than when in air, which means that the wavelength of electromagnetic waves in the dielectric is shorter than when in air. That is, it becomes shorter when filled with air, and the degree is related to the ratio of the electromagnetic waves transmitted along the dielectric to the total energy of the electromagnetic waves transmitted into the waveguide. In other words, it is strongly related to the strength of the electric field where the dielectric is located, and this phenomenon is most pronounced when the dielectric is located near the center of the strongest electric field in the waveguide. It is also related to the width or volume of the dielectric material, and the larger the dielectric constant of the dielectric material, the more remarkable it is.

Of the three variables, namely the position, volume, and permittivity of the dielectric, it is the position that can be changed during the operation of the waveguide. As shown in the waveguide cross-sectional structure of FIG. 8, the feed screw 12 is rotated using the motor 13. When the feed screw rotates, the dielectric moves in the transverse direction of the waveguide. Therefore, the phase between the slots also changes.

10 and 11 show examples of the radiation pattern of the waveguide relative to the position of the dielectric. In this way, the electromagnetic wave distribution inside the microwave oven is changed as the direction of the electromagnetic wave cooker of the waveguide is changed, which is advantageous in view of uniform heating than when the direction of incident electromagnetic waves is fixed as in the conventional case.

As mentioned above, the method of improving the uniform heating performance of a microwave oven using the present invention is not only a method of continuously moving the position of the dielectric in the waveguide to change the distribution of the electromagnetic field in the cavity, but also a method of controlling the dielectric over time for each desired dish. By adjusting the position properly, you can achieve the best cooking. If such a cooking algorithm is made into a menu and input into a microwave oven, an optimum cooking for various dishes can be realized.

As described above, the waveguide device of the present invention changes the distribution of electromagnetic fields in the cavity by changing the direction of the electromagnetic wave incident into the cavity, thereby greatly improving the uniform heating performance compared to the conventional art, and effectively reducing the internal space of the cavity. It can be used as an effect.

Claims (3)

In a microwave oven provided with a magnetron for generating electromagnetic waves, and a waveguide for guiding the electromagnetic waves generated in the magnetron into the cavity, The waveguide 8 comprises an opening surface composed of a plurality of slots 10, A waveguide of a microwave oven, characterized in that a dielectric (11) is provided in the waveguide for varying the phase between the slots (10). The method of claim 1, The dielectric (11) is installed in the longitudinal direction of the waveguide, the waveguide of the microwave oven, characterized in that it passes through the slot (10) region and moves in the transverse direction of the waveguide. The method of claim 2, The dielectric is supported by the feed screw 12 and moved by the rotation of the feed screw 12, The feed screw (12) is a waveguide of the microwave oven, characterized in that rotated by a motor (13).