KR19980054842A - Microwave oven with improved waveguide - Google Patents

Abstract

A microwave oven is disclosed having an improved waveguide that can improve the transmission efficiency of high frequencies. The microwave oven includes a cabinet having a cooking compartment in which food can be placed, and a magnetron for generating a high frequency for cooking the food. A waveguide is formed with a first transmission line for transmitting the high frequency to the upper part of the cooking chamber and a second transmission line which is continuous with the first transmission line and transmits from the upper part of the cooking chamber to the cooking chamber. A bent portion is formed at a connection portion between the first transmission line and the second transmission line, and the bend portion transmits the high frequency wave propagated along the first transmission line along the second transmission line, and the first transmission line and the first transmission line. And a reflecting surface for reducing inductance generated at the connection of the second transmission line. The transmission efficiency of the microwave oven may be improved by minimizing inductance and capacitance formed at the bent portion between the first transmission line and the second transmission line.

Description

Microwave oven with improved waveguide

The present invention relates to a waveguide of a microwave oven. In particular, the present invention relates to a waveguide having an improved structure for improving the transmission efficiency of electromagnetic waves of a microwave oven.

Generally, household microwave ovens are equipped with magnetrons for generating high frequencies. The microwave oven is equipped with a magnetron that generates high frequency. The high frequency wave is mainly generated by stably applying the high voltage generated by the mutual induction action to the magnetron in the first and second induction coils of the high voltage transformer mounted on the bottom plate of the electric field chamber. It is irradiated into the cooking chamber of the stove. When the high frequency is irradiated into the cooking chamber through the waveguide, the food placed inside the cooking chamber by the high frequency is heated and cooked.

The microwave oven is classified into a stirrer type and a radiation type according to a method of irradiating a high frequency generated from the magnetron into the cooking chamber. In a radiated microwave oven, the magnetron is attached to the side wall of the cooking chamber so as to be in direct communication with the cooking chamber. The high frequency generated from the magnetron of the radiated microwave oven is directly irradiated into the cooking chamber of the microwave oven (without reflection and refraction) to cook food. Microwave ovens of this type are disclosed, for example, in US Pat. No. 5,082,999 issued to Yamaguchi et al. On the other hand, in the stirrer type microwave oven, the high frequency generated by the magnetron is radiated from the upper part of the cooking chamber to which the stirrer is attached via a long waveguide.

1 is a schematic diagram showing a conventional stirrer type microwave oven.

As shown in FIG. 1, a conventional microwave oven 400 includes a cabinet 430. The cabinet 430 includes a heating chamber 410 and a control chamber 420 separated from each other by the partition wall 415.

The waveguide 450 guides the high frequency generated from the magnetron 440 to the cooking chamber 410 at the upper portion of the cooking chamber 410. The magnetron 440 is fixed to the upper portion of the control room 420. The high frequency generated from the magnetron 440 passes through the waveguide 450 and is irradiated into the cooking chamber 410 to cook food, and a hool 452 is formed on the cooking chamber 410. One end of the magnetron 440 is integrally formed with an antenna 442 for transmitting the high frequency. The waveguide 450 is continuously formed from the hool 452 formed on the cooking chamber 410 to the magnetron 440. In addition, the upper wall of the waveguide 450 on the horn 452 is provided with a stirrer 454 for dispersing the high frequency generated by the magnetron 440. The stirrer 454 is configured to rotate naturally or by a motor (not shown) to uniformly wave-diffuse high frequency generated and transmitted from the magnetron 440 into the cooking chamber 410. Allow food to cook evenly.

A transformer 460 for generating a high voltage is mounted on the bottom wall of the control room 420. The transformer 460 is connected to the magnetron 440 to apply a high voltage to the magnetron 440.

A cooking table 480 is provided in the cooking room 410 in which food to be cooked is placed. In order to uniformly heat the food, the countertop 480 is connected to the motor 470 through the shaft 472 is rotated by the motor 470 when cooking.

2 is a schematic cross-sectional view showing details of the high frequency transmission line in the waveguide 450. Referring to FIG. 2, the high frequency generated by the magnetron 440 is emitted to the outside by the antenna 442. The waveguide 450 extends from the magnetron 420 to the upper portion of the cooking chamber 410, and has a first transmission line T1 and a first transmission line T1 formed by the upper surface S1 and the lower surface S2. Extends from to the horn 452 at the top of the cooking chamber 410 and has a second transmission line T2 defined by the first side S3 and the second side S4. On the opposite side of the first transmission line T1, the waveguide 450 extends from the magnetron 440 by a predetermined distance d, and the predetermined distance is formed to be about λ / 4 of the wavelength λ of the high frequency wave. The stirrer 454 is attached to the upper surface S1 of the waveguide 450 such that the distance L1 from the upper surface S1 is shorter than the distance between the upper surface S1 and the lower surface S2.

The microwave oven 400 having such a configuration operates as follows.

First, when a user presses an operation switch (not shown) attached to the front of the cabinet 430, a microcomputer (not shown) built in the microwave oven 400 transmits an operation signal to the transformer 460. do. Accordingly, the transformer 460 generates a high voltage, and the high voltage is transmitted to the magnetron 440 to generate a high frequency by the magnetron 440.

The high frequency wave is oscillated through the antenna 442 and is irradiated into the cooking chamber 410 through the through hole 452 through the first transmission line T1 and the second transmission line T2 of the waveguide 450. do. Therefore, the food placed on the countertop 480 is heated. At the same time, the microcomputer applies an operation signal to the motor 480, thereby driving the motor 470 to rotate the countertop 480 while the food is heated.

However, in the conventional microwave oven 400 having such a configuration, when the output of the high frequency output from the magnetron 440 is irradiated into the cooking chamber via the first transmission line T1 and the second transmission line T2, it is about. It will be reduced to 50 to 60%. As described above, the decrease in the transmission efficiency of the high frequency generated by the magnetron 440 may be due to the waveguide itself acting as a resistance of the high frequency. In particular, in the conventional microwave oven 400 as described above, a spark occurs near a corner (A in FIG. 2) where the first transmission line T1 and the second transmission line T2 meet. The spark is a phenomenon caused by the concentration of high frequency energy, which lowers the transmission efficiency of the high frequency. These sparks also occur around the stirrer fan.

As such, when the spark is generated, not only the transmission efficiency of the high frequency is reduced and the output is lowered, but also the substance is generated near the bent portion due to the spark generation, and the cooking state of the food in the cooking chamber 410 becomes poor.

On the other hand, US Patent No. 4,937,418 issued to Boulard discloses a microwave oven which can minimize the stirring of foods and at the same time make the temperature distribution inside the cooking chamber more uniform.

Bollard's microwave oven comprises a waveguide comprising a waveguide having at least one wave-receiving opening formed at the top and at least one wave-diffusing opening formed at the bottom. spreader). Inside the waveguide are provided first and second deflectors for refracting the wave entering the waveguide.

However, since the Bollard wave dispersing apparatus is installed in the cooking chamber as a separate component, it is possible to reduce the utilization area of the cooking chamber as well as reduce the transmission efficiency.

The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a microwave oven having an improved waveguide that can improve the transmission efficiency of high frequency.

1 is a schematic diagram showing a conventional stirrer type microwave oven.

FIG. 2 is a schematic cross-sectional view for showing details of a high frequency transmission line in the waveguide of FIG.

3 is a schematic diagram illustrating a microwave oven according to an embodiment of the present invention.

4 is a schematic cross-sectional view for illustrating in detail the high-frequency transmission line in the waveguide.

FIG. 5 is a schematic diagram for explaining the reflective surface of the microwave oven shown in FIG. 4 in more detail.

6 and 7 are principle diagrams for explaining the transmission efficiency of the high frequency in accordance with the change in the width of the transmission line.

Explanation of symbols for main parts of the drawings

100, 400 ... microwave 130, 430 ... cabinet

115, 415 ... bulkheads 110, 410 ... cooking rooms

120, 420 ... control room 140, 440 ... magnetron

150, 450 ... waveguide 152, 452 ... hool

142, 442 ... antenna 154, 454 ... stirrer

160, 460 ... transformers 180, 480 ... countertops

172, 472 ... shaft 170, 470 ... motor

In order to achieve the above object of the present invention,

A cabinet having a cooking compartment in which food can be placed;

Magnetron for generating a high frequency for cooking the food; And

A first transmission line for transmitting the high frequency to the upper part of the cooking chamber and a first transmission line which is continuous to the upper part of the cooking chamber, and a second transmission line for transmitting into the cooking chamber from the upper part of the cooking chamber, the first transmission line and the first transmission line In a microwave oven having a waveguide in which a bent portion is formed at a connection portion with two transmission lines,

The bent portion transmits the high frequency wave propagated along the first transmission line along the second transmission line, and has a reflective surface for reducing inductance generated at the connection portion between the first transmission line and the second transmission line. It provides a microwave oven, characterized in that.

The high frequency wave is oscillated through the antenna of the magnetron and is transmitted along a first transmission line formed by the upper and lower surfaces of the waveguide. The transmitted high frequency is reflected by the reflective surface and irradiated into the cooking chamber through the through hole through the second transmission line formed by the first side and the second side. Thus, the food placed on the countertop is heated.

The transmission efficiency of the microwave oven may be improved by minimizing inductance and capacitance formed at the bent portion between the first transmission line and the second transmission line.

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

3 is a schematic diagram illustrating a microwave oven according to an embodiment of the present invention.

Referring to FIG. 3, the microwave oven 100 includes a cabinet 130. The cabinet 130 includes a heating chamber 110 and a control chamber 120 separated from each other by the partition wall 115. The food to be cooked is placed in the cooking room 110. In addition, the control chamber 120 is provided with a magnetron 140 for generating a high frequency for cooking the food.

The upper part of the cooking chamber 110 is provided with a waveguide 150 for guiding the high frequency generated from the magnetron 140 to the cooking chamber 110. The magnetron 140 is fixed to the upper portion of the control room 120. A high frequency horn 152 is formed on the upper portion of the cooking chamber 110 through the waveguide 150 generated by the magnetron 140. At one end of the magnetron 140, the antenna 142 for transmitting the high frequency is integrally formed. The waveguide 150 is continuously formed from the hool 152 formed on the cooking chamber 110 to the magnetron 140. In addition, a stirrer 154 is provided on an upper wall of the waveguide 150. The stirrer 154 is disposed such that the start point of the reflective surface R and one end thereof vertically coincide with each other, and are configured to be rotatable by a motor (not shown) or naturally. The stirrer 154 uniformly waves-diffuses the high frequency generated and transmitted from the magnetron 140 into the cooking chamber 110 to uniformly cook food.

A transformer 160 for generating a high voltage is mounted on the bottom wall of the control room 120. The transformer 160 is connected to the magnetron 140 to apply a high voltage to the magnetron 140.

In the cooking chamber 110, a cooking table 180 on which food to be cooked is placed is provided. In order to uniformly heat the food, the countertop 180 is connected to the motor 170 through the shaft 172 and rotated by the motor 170 when cooking.

4 is a schematic cross-sectional view showing details of the high frequency transmission line in the waveguide 150. Referring to FIG. 4, the high frequency generated by the magnetron 140 is emitted to the outside by the antenna 142. The waveguide 150 extends from the magnetron 120 to the upper portion of the cooking chamber 110 and is formed by an upper surface S1 ′ formed by the upper wall and a lower surface S2 ′ (formed by the lower wall) parallel thereto. It extends from the first transmission line T1 'and the first transmission line T1' to the hool 152 of the upper part of the cooking chamber 110, and has a first side surface S3 'and a second side surface S4'. Has a second transmission line T2 '. In the bent portion where the first transmission line T1 'and the second transmission line T2' are in contact, the second side surface S4 'is directly connected to the lower surface S2' while the first side surface S3 'is connected. The reflective surface R is formed between the upper surface S1 'and the upper surface S1'. The distance between the first transmission width W1, which is the distance between the upper surface S1 ', and the lower surface S2', and the second transmission width W2, which is the distance between the first side surface S3 'and the second side surface S4', are the same. Do. As shown in the drawing, a high frequency wave propagated along the first transmission line T1 is applied to the bent portion, which is a connection portion between the first transmission line T1 'and the second transmission line T2', to the second transmission line T2. Reflecting surface R is formed to reflect toward ').

5 is a schematic diagram for explaining the reflective surface R in more detail. As shown, the reflecting surface R and the first transmission line T1 'are formed at a constant angle θ. The angle θ is 40 to 50 degrees, preferably 45 degrees. Therefore, the angle between the reflective surface R, the upper surface S1 'and the first side surface S3' is formed to be 130 to 140 degrees.

The reflection surface R has a shortest distance L from the first side surface S3 ', the upper surface S1', and the tangential portion P, and the first transmission width W1 or the second transmission width W2. 40 to 60%, preferably about half. In addition, one end of the rotary blade of the stirrer 154 positions the stirrer 154 so as to vertically coincide with the point where the reflective surface R and the upper surface S1 ′ meet.

6 and 7 are principle diagrams for explaining the transmission efficiency of the high frequency in accordance with the change in the width of the transmission line. In general, a straight transmission line has the best transmission efficiency. However, as shown in Fig. 6, when there is a portion of the transmission line Ta having a width W1 'larger than the peripheral width W in the middle portion, the transfer state of the bent portion is a capacitor during high frequency transmission. Act as. In addition, as shown in Fig. 7, the transmission line Tb acts as an inductor during high frequency transmission when there is a portion having a width W2 'smaller than the peripheral width W in the middle portion. As described above, when a capacitor or an inductor is present on the high frequency transmission line, it acts as a resistance component during high frequency transmission, thereby decreasing the high frequency transmission efficiency. Therefore, it is desirable to prevent the formation of capacitors and inductors in such high frequency transmission lines.

In the stirrer type microwave oven, since the linear transmission line between the magnetron and the cooking chamber cannot be formed, a bent portion is formed. This bent portion acts as an inductor in the radio wave transmission path, thereby lowering the transmission efficiency of high frequency. In the present invention, the formation of the inductor at the bent portion is prevented to improve the transmission efficiency.

In order to maximize the transmission efficiency at the bent portion, by forming a planar reflective surface as shown in FIG. 5, the capacitance or inductance of the high frequency formed at the bent portion can be minimized. The reflective surface is formed such that the first transmission line T1 'and the reflective surface have an angle of approximately 40 to 50 degrees.

On the opposite side of the first transmission line T1 ′, the waveguide 150 extends from the magnetron 140 by a predetermined distance d. The predetermined distance is formed to a degree of? / 4 of the wavelength? Of the high frequency wave. The stirrer 154 is attached to the upper surface S1 ′ of the waveguide 150 such that the distance L1 ′ from the upper surface S1 is shorter than the distance between the upper surface S1 ′ and the lower surface S2 ′.

The microwave oven 100 having such a configuration operates as follows.

First, when a user presses an operation switch (not shown) attached to the front of the cabinet 130, a microcomputer (not shown) built in the microwave oven 100 transmits an operation signal to the transformer 160. do. Accordingly, the transformer 160 generates a high voltage, and the high voltage is transmitted to the magnetron 140 to generate a high frequency by the magnetron 140.

The high frequency wave is oscillated through the antenna 142 and is transmitted along the first transmission line T1 ′ of the waveguide 150. The transmitted high frequency is passed through the transmission line and the second transmission line T2 'formed by the tangent P between the reflective surface R, the lower surface S2' and the second side surface S4 '. It is irradiated into the cooking chamber 110 through the 152. Therefore, the food placed on the countertop 180 is heated. At the same time, the microcomputer applies an operation signal to the motor 180, thereby driving the motor 170 to rotate the countertop 180 while the food is heated.

According to the present invention, the transmission efficiency of the microwave oven can be improved by minimizing inductance and capacitance formed at the bent portion between the first transmission line and the second transmission line. Since the transmission efficiency of the microwave oven is increased, power consumption can be reduced. In this case, the size of the transformer used in the microwave can be reduced, thereby reducing the cost. In addition, since the transmission efficiency is increased, the spark phenomenon is suppressed in the vicinity of the bent portion and the stirrer, and the formation of this substance due to the spark occurrence is suppressed.

Although the above has been described with reference to a preferred embodiment of the present invention, those skilled in the art will be variously modified and changed within the scope of the present invention without departing from the spirit and scope of the invention described in the claims below. I can understand that you can.

Claims (7)

A cabinet having a cooking compartment in which food can be placed; Magnetron for generating a high frequency for cooking the food; And A first transmission line for transmitting the high frequency to the upper part of the cooking chamber and a first transmission line which is continuous to the upper part of the cooking chamber, and a second transmission line for transmitting into the cooking chamber from the upper part of the cooking chamber, the first transmission line and the first transmission line In a microwave oven having a waveguide in which a bent portion is formed at a connection portion with two transmission lines, The bent portion transmits the high frequency wave propagated along the first transmission line along the second transmission line, and has a reflective surface for reducing inductance generated at the connection portion between the first transmission line and the second transmission line. Microwave oven characterized in that. The microwave oven of claim 1, wherein the first transmission line and the second transmission line have the same radio wave transmission width. The microwave oven according to claim 1, wherein the reflective surface and the first transmission line have a predetermined angle and the reflective surface is inclined. The microwave oven according to claim 3, wherein the predetermined angle is 40 to 50 degrees. The waveguide of claim 1, wherein the waveguide includes a first surface for forming a first transmission line, a second surface facing the third wave, and a third surface for forming the second transmission line, and a fourth surface facing the waveguide. The bent portion is formed at a tangential portion where the first surface and the third surface are connected, and the reflecting surface is formed so as to continue the second surface and the fourth surface. The method of claim 5, wherein the first transmission line and the second transmission line is formed vertically, the reflective surface is formed with an angle of 130 to 140 ° with the second surface and the fourth surface, characterized in that microwave. 6. The method of claim 5, wherein the first transmission line and the second transmission line is formed vertically, the reflective surface is the shortest distance from the tangent portion is 40 to 60% of the width between the first surface and the second surface Microwave oven characterized by the.