KR100208695B1 - Microwave oven with waveguide tube - Google Patents

Abstract

Disclosed is a microwave waveguide for forming microwaves in which a high frequency oscillated in a magnetron is uniformly irradiated into a cooking chamber without dielectric loss so that food can be heated efficiently, and a bent portion that can use a broadband magnetron is provided. The microwave oven includes a cabinet including a cooking chamber, a control chamber and a driving unit. A waveguide is attached to a predetermined position of the partition wall separating the cooking chamber and the control chamber. The magnetron has an antenna for transmitting the high frequency toward the waveguide and is coupled to one end of the waveguide. A transformer is formed on one side of the lower side of the control room, and the magnetron generates a high frequency by applying a high voltage to the magnetron. At least one slit is formed in the partition wall so that a high frequency generated from the magnetron can be incident into the cooking chamber. At least one bent portion for accelerating and concentrating electrons by forming a high frequency magnetic field output from the antenna is formed at an upper end of the slit. Microwave ovens can improve the heating effect on food and the use of broadband magnetrons.

Description

Microwave oven with waveguide with conductive bends

The present invention relates to a microwave oven having a curved waveguide, and more particularly, to a high-frequency microwave emitted from the magnetron evenly irradiated into the cooking chamber without dielectric loss to effectively heat food and to a broadband magnetron The present invention relates to a microwave oven having a waveguide having a bent portion for use.

A microwave oven is a device that heats food by generating a high frequency by applying a high voltage to the high frequency oscillation tube. By bringing the high frequency into the food, the food becomes dielectric heating.

A magnetron is used as the high frequency oscillation tube, and the magnetron is applied with a high voltage by a transformer. The transformer is installed on the inner bottom of the cabinet and generates high voltage by mutual induction action of the primary and secondary induction coils. The high frequency generated by the magnetron proceeds into the cooking chamber of the microwave oven through the waveguide and the slit formed in the partition wall between the waveguide and the cooking chamber. The high frequency wave is diffracted through the slit and spread widely. The diffracted high frequency waves reach the food or directly reach the food while reflecting the surfaces of the cooking chamber to heat the food.

1 is a cross-sectional view showing a conventional microwave oven. Referring to FIG. 1, a conventional microwave oven 100 includes a cabinet 110. The cabinet 110 includes a cooking chamber 120, a control chamber 130, and a driving unit 150. The cooking chamber 120 and the control chamber 130 are separated from each other by the partition wall 140. A transformer 160 is disposed at one lower side of the control room 130. The waveguide 135 is attached to a predetermined position of the partition wall 140 toward the control room 130, and the magnetron 133 is coupled to one end of the waveguide 135. The transformer 160 is electrically connected to the magnetron 133. The transformer 160 applies a high voltage to the magnetron 133 so that the magnetron 133 generates a high frequency. At one end of the magnetron 133, the antenna 131 for transmitting the high frequency is integrally formed. A slit 137 is formed in the partition wall 140 so that the high frequency generated by the magnetron 133 may be incident into the cooking chamber 120. The driving unit 150 is a motor 153 that is driven when the food is heated, the rotary tray 157 to put the food and the rotary tray 157 and the motor 153 is connected to the rotary tray 157 It includes a shaft 155 rotatably supporting the. Since the rotating tray 157 rotates by the rotation of the motor 153 while the high frequency radiation is made to the cooking chamber 120, the food is uniformly heated.

The operation of the microwave oven 100 having such a configuration is as follows.

In general, the front of the cabinet 110 is attached to the operation switch (not shown) of the microwave oven. First, the user presses the operation switch to operate the microwave oven. A microcomputer (not shown) embedded in the microwave oven 100 applies an operation signal to the motor 153 to drive the motor 153, and simultaneously transmits an operation signal to the transformer 160 to transmit the transformer. Let 160 generate a high voltage. The high voltage generated from the transformer 160 is transmitted to the magnetron 133 so that the magnetron 133 generates a high frequency. The high frequency generated by the magnetron 133 is radiated to the cooking chamber 120 through the slit 137 formed on the antenna 135, the waveguide 135, and the partition wall 140. The high frequency wave is diffracted while passing through the slit 137. The diffracted high frequency spreads widely and proceeds into the cooking chamber 120. The high frequency propagated into the cooking chamber 120 directly reaches the food or is reflected by the surfaces inside the cooking chamber 120 to reach the food, thereby heating the food according to the above process.

Meanwhile, when the microcomputer transmits an operation signal to the transformer 160, the motor 153 rotates the shaft 155 connected to the motor 153. The shaft 155 is connected to the rotary tray 157 in the cooking chamber 120 to transmit the rotational force of the motor 153 to the rotary tray 157. Therefore, the rotary tray 157 is interlocked with the motor 153 to uniformly touch high frequency food in the cooking chamber.

However, the conventional microwave oven 100 having the above configuration has a limited portion where diffracted high frequency touches food and the high frequency radiation irradiated into the cooking chamber 120 penetrates the food only by a limited depth. If a large amount of food is placed on 157), there is a problem that the food is unevenly heated.

In order to solve the above problem, a microwave oven having a slit having various shapes has been developed so that high frequency of uniform density in the amount of the electromagnetic field can be irradiated to food. These slits are designed to evenly heat food by diffraction of high frequency incident light into the cooking chamber 120. However, since the slits have a complicated shape, the mold process is difficult during fabrication, thereby increasing manufacturing costs, and food is not evenly heated.

On the other hand, US Patent No. 4,937, 418 discloses a microwave oven that can make the temperature distribution inside the cooking chamber more uniform. According to this patent, a microwave dispersion device comprises a waveguide having at least one wave-receiving opening formed at the top and at least one wave-diffusing opening formed at the bottom. (wave spreader). Inside the waveguide, first and second diffraction members are provided to diffract waves entering the waveguide.

However, the dispersion apparatus of the US patent has a disadvantage of reducing the utilization space of the cooking chamber as a component installed in the cooking chamber, and the production cost increases during manufacturing because the number of parts increases. In addition, the above-mentioned conventional microwave oven and the microwave oven of US Pat. No. 4,937,418 have a structure in which the reflection loss due to the shape of the waveguide is very large, so that dielectric loss occurs and heating efficiency is lowered. The conventional microwave ovens mentioned above and the microwave ovens of U.S. Patent No. 4,937,418 have the possibility of damaging the magnetron when the anode is overheated (over 300 ° C). Magnetron with ± 50) is used. Therefore, magnetrons that do not have a constant oscillation frequency cannot be used.

The present invention has been made to solve the problems of the prior art as mentioned above, the present invention is to improve the shape of the waveguide to reduce the dielectric loss (increase the propagation efficiency), so that the high frequency can be evenly irradiated inside the cooking chamber It is possible to improve the heating effect on food, and to provide a microwave oven that can use a broadband magnetron.

1 is a cross-sectional view showing a conventional microwave oven.

Figure 2 shows a cross-sectional view of a microwave oven according to an embodiment of the present invention.

3 is a cross-sectional view illustrating the waveguide shape of the microwave oven illustrated in FIG. 2.

4 is a schematic diagram for explaining the principle that the magnetron accelerates the electrons.

FIG. 5 is a schematic diagram illustrating a change in a magnetic field by controlling the magnitude of an alternating voltage at an anode when electrons are emitted from a cathode to an anode in the magnetron of FIG. 4.

FIG. 6 illustrates an output range of the magnetron applicable to the microwave oven illustrated in FIG. 2.

<Explanation of symbols for main parts of drawing>

210: cabinet 220: cooking chamber

230: control room 231: antenna

233: magnetron 235: waveguide

237 slits 239 bends

250: driving unit 253: motor

255: shaft 257: rotary tray

In order to achieve the above object, the microwave oven according to the present invention is provided with a cabinet. The cabinet includes a cooking chamber, a control chamber and a driving unit. The cooking chamber and the control chamber are separated from each other by a partition wall. A transformer is installed at one lower side of the control room. A waveguide is attached to a predetermined position of the partition inside the control room, and a magnetron is coupled to one end of the waveguide. The transformer and the magnetron are electrically connected to each other. The transformer applies a high voltage to the magnetron to cause the magnetron to generate a high frequency. At one end of the magnetron, an antenna for transmitting the high frequency is integrally formed. Slit is formed in the partition wall inside the waveguide so that the high frequency generated from the magnetron can be incident into the cooking chamber. One surface of the upper surface or the lower surface forming the slit is formed with a bent portion to increase the magnetic field of the high frequency output from the antenna. The bent portion is formed at an angle of about 90 ° to the waveguide side. The driving unit includes a motor driven when food is heated, a rotary tray capable of placing food in the cooking chamber, and a shaft connecting the rotary tray and the motor to support the rotary tray.

The user presses the operation switch of the microwave oven on the front of the cabinet to operate the microwave oven. The microcomputer embedded in the microwave oven applies an operation signal to the motor to drive the motor, and simultaneously transmits the operation signal to the transformer. The transformer receiving the operation signal generates a high voltage. Since the transformer and the magnetron are electrically connected to each other, the high voltage generated from the transformer is transmitted to the magnetron, and thus high frequency is generated in the magnetron. The high frequency generated in the magnetron is radiated through the antenna and proceeds into the waveguide.

The high frequency is encountered with the bent portion formed in the slit, thereby changing the size of the magnetic field. The bend increases the size of the magnetic field, and the high frequency electrons are further accelerated by the magnetic field, thereby reducing the dielectric loss of the high frequency. The high frequency goes through the slit into the cooking chamber. The high frequency is diffracted while passing through the slit. The diffracted high frequency spreads widely and proceeds into the cooking chamber. In this case, the smaller the size of the slit, the greater the diffraction effect, but the optimum efficiency may vary depending on the thickness, the size of the bent portion and the distance to the antenna. In addition, according to the output of the magnetron, the thickness, the size of the bend and the distance to the antenna may be different. The high frequency propagated into the cooking chamber arrives at the food directly or is reflected by the surfaces in the cooking chamber to reach the food and the food is heated.

Meanwhile, the motor rotates the shaft connected to the motor while the high frequency travels into the cooking chamber, and the shaft rotates the rotary tray inside the cooking chamber. Therefore, the food above the rotary tray is heated by high frequency while rotating.

The microwave oven according to the present invention by the above configuration and operation is more effective food heating due to the reduction of dielectric loss, and can use a wide-band magnetron.

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

As shown in FIG. 2, the microwave oven 200 according to an embodiment of the present invention includes a cabinet 210. The cabinet 210 includes a cooking chamber 220, a control chamber 230, and a driver 250. The cooking chamber 220 and the control chamber 230 are separated from each other by the partition wall 240. A transformer 260 is installed at one lower side of the control room. The waveguide 235 is attached to a predetermined position of the partition wall 240 toward the control room 230. A magnetron 233 is coupled to one end of the waveguide 235 opposite to the partition wall 240. The transformer 260 is electrically connected to the magnetron 233 to apply a high voltage to the magnetron 233. When a high voltage is applied to the magnetron 233, the magnetron 233 radiates high frequency.

The driving unit 250 is connected to the motor 253 which is driven when the food is heated, the rotary tray 257 for placing food in the cooking chamber, and the rotary tray 257 and the motor 253 and the rotation A shaft 255 supporting the tray 257. The rotary tray 257 is rotated by the rotation of the motor 253 to uniformly heat food while the electromagnetic waves proceed to the inside of the cooking chamber 220.

3 is a cross-sectional view showing in detail the internal structure of the waveguide 235 of the microwave oven shown in FIG. Referring to FIG. 3, the magnetron 233 has an antenna 231 for transmitting the high frequency wave to the waveguide 235. A slit 237 is formed in the partition wall 240 in the waveguide 235 so that the high frequency generated by the magnetron 233 can be incident to the cooking chamber 220. The bent portion 239 is integrally formed on the upper surface 237a of the surface of the slit 237. The bent portion 239 may be formed on the lower surface 237b. When only one slit 237 is formed, it is preferable to form two or more slit because high frequency simply has a diffraction effect. In addition, it is preferable to form two or more bends in the same number as the number of the slits 237 in correspondence with the slit 237, even if only one can adjust the high frequency in the waveguide 235 as desired. The bent portion 239 extends toward the inside of the waveguide 235, that is, the magnetron 233, at an angle of about 90 ° to a surface of the slit 237. The bent portion 239 is made of a dielectric having a high dielectric constant such as copper. The high frequency radiation emitted from the magnetron 233 is transmitted to the bent portion 239. When the high frequency reaches the bent portion 239, the frequency changes and at the same time a change in the magnetic field occurs. The magnitude of the magnetic field is increased by the bent portion 239 to be directed to the inside of the cooking chamber. At this time, the magnetic field increases the intensity of the power density toward the interior of the cooking chamber 220. The impedance of the electromagnetic wave to be changed is expressed by the following equation.

The relation is an equation obtained experimentally, Is the characteristic impedance of the electromagnetic wave, Is the relative permittivity of the bend, h is the distance from the antenna to the bend, and w is the width μ of the bend. As can be seen from the above relation, the characteristic impedance of the electromagnetic wave can be adjusted by adjusting the size of the bent portion, thereby reducing the dielectric loss caused by the existing side plate shape. According to the relational expression, regardless of the size of the cooking chamber 220 and the state of the food when heating the food it is possible to improve the propagation efficiency (reduction of dielectric loss) and the intensity of the power density is increased to the cooking chamber 220 The output of the incident electromagnetic wave becomes large. The bent portion 239 may adjust the thickness t and the length w according to the size of the waveguide 235. Therefore, the dielectric efficiency may be maximized by adjusting the size of the waveguide 235, the thickness t and the length w of the curved portion 239. In addition, the thickness t, the size w, and the size of the waveguide 235 may be varied. Since the high frequency oscillated by the magnetron 233 is in contact with the bent portion 239, the impedance is changed, and thus the frequency incident into the cooking chamber is changed. Therefore, the high frequency oscillated by the magnetron 233 may be changed to another frequency by changing the size of the bent portion 239. When the electromagnetic wave reaches the bent portion, the amount of magnetic field in the dielectric is infinitely large, which leads to an unlimited state of cut-off frequency. Thus, a wide range of magnetrons can be used because they can be changed to other frequencies using magnetrons that produce specific frequencies of specific outputs.

4 illustrates a principle of generating electromagnetic waves and schematically illustrates a principle of changing electromagnetic waves by a magnetic field that increases in a bent portion. Referring to FIG. 4, when electrons are emitted from the cathode 273, the electrons are accelerated by an electric field. Since the magnetic field plays a role of concentrating the electrons, when a magnetic field is applied to the electrons emitted from the cathode 273, the path of the electrons is changed to act as a traveling wave. The electrons emitted from the cathode 273 are accelerated to the anode through the grid electrode 275. The accelerated electrons reach the current collector 279 that collects the electrons. The electrons are resonated by the radio frequency (RF). Electrons resonated by the radiator frequency pass through the radio frequency attenuator 280. The radio frequency is attenuated while passing through the radio frequency attenuator 280, and then electromagnetic waves are radiated. At this time, if the magnitude of the magnetic field is small, the traveling wave is changed into a delayed electromagnetic field and dielectric loss occurs.

Figure 5 is a magnetic field as shown a schematic diagram to control the alternating voltage of at the anode (B _0), the magnetic field (B ₀₎ controls the acceleration of the electron by controlling an alternating voltage of at the anode (277) . Is for showing the moving direction of the electron. The magnetron 273 has a permanent magnet therein for accelerating and emitting electrons.

6 illustrates the oscillation frequency of the magnetron usable when the present invention is applied and the output possible range at the oscillation frequency. As shown, when the waveguide according to the present invention is used, the oscillation frequency of the magnetron that can be used is in the range of 1 GHz to 10 GHz, and the output range is 1 Mw to 10 Mw.

The microwave oven according to the present invention as described above reduces the dielectric loss (increasing the propagation efficiency) by improving the shape of the waveguide, and accordingly, it is possible to improve the heating effect on food by allowing the high frequency to be evenly irradiated inside the cooking chamber. The length and thickness of the bent portion 239 and the size of the waveguide are adjusted to enable the use of a magnetron of a wide frequency as well as a magnetron of a specific frequency.

Although the preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, the present invention is not limited thereto and may be improved or modified by those skilled in the art within the scope of the technical idea of the present invention.

Claims (6)

A cabinet including a control chamber for controlling a cooking chamber and components for placing food, and a partition wall separating the cooking chamber and the control chamber is formed; A transformer formed at one side of the lower side of the control room and connected to a power source to generate a high voltage; A magnetron provided in the control room and configured to generate a high frequency to input the high voltage to cook the food; And At least one bent portion attached to the partition wall to enlarge the magnetic field of the high frequency generated from the magnetron and at least one or more slits so that the high frequency generated from the magnetron can be incident into the cooking chamber A microwave oven comprising a waveguide provided. The microwave oven of claim 1, wherein two or more slits are formed. The microwave oven according to claim 2, wherein at least two curved portions are formed corresponding to the slits. The microwave oven of claim 1, wherein the curved portion is made of a dielectric material. The microwave oven of claim 1, wherein the slit is formed in the partition wall, and the bent portion extends toward the magnetron integrally from a lower end of the slit. The microwave waveguide of claim 5, wherein the bent portion is bent at an angle of 90 ° with the slit.