JPS6259436B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to improving radio wave distribution within a heating chamber of a high-frequency heating device. Conventional structure and its problems Conventionally, there is a turntable method in which the food table is rotated as a method to equalize the distribution of radio waves in the heating chamber of high-frequency heating equipment, but in this conventional method, radio waves are transmitted from the top of the heating chamber. Because it has a structure that emits radio waves, the distance from the source of the radio waves to the food is long, so the radio waves are reflected off the heating chamber wall many times before being absorbed by the food, and are attenuated to some extent before being absorbed by the food. Therefore, it has the disadvantage of poor heating efficiency and the disadvantage that the heating in the center of the heating chamber is inevitably weak. In order to overcome this drawback, a method has also been proposed in which a rotating antenna is installed approximately in the center of the bottom of the heating chamber and radio waves are radiated from below the food, but the drawback of this method is that the distance between the antenna and the food is close. Therefore, food directly above the antenna is heated well, but food placed toward the edge of the heating chamber is less likely to be heated.
In addition, in the case of thick foods, the bottom part is well heated, but there is a problem in that the top part, especially the center part, is not easily heated. In particular, in the case of a heating chamber whose planar shape when viewed from above is not a square but a horizontally long rectangle, the phenomenon that heating at both left and right ends is weak becomes noticeable. In order to solve this problem, it has been proposed to provide multiple radio wave supply ports in addition to the rotating antenna at symmetrical positions across the rotating antenna, but the problem in this case is that the radio wave supply ports on the side closer to the high frequency oscillator The radio wave radiation from the supply port on the far side was less than the radio wave radiation from the supply port on the far side, and therefore the left and right or front and rear heating balance was not good. OBJECTS OF THE INVENTION The present invention eliminates the above-mentioned conventional drawbacks, and aims to provide a high-frequency heating device with good heating efficiency and radio wave distribution. Structure of the Invention In order to achieve the above object, the present invention includes a heating chamber for storing food, a high frequency oscillator for supplying high frequency waves into the heating chamber, and a transmission system for transmitting the radio waves oscillated by the high frequency oscillator. a rotating antenna that connects the heating chamber and the transmission means at substantially the center of a bottom wall of the heating chamber; and a food mounting table that separates the heating chamber into a heating space and a radio wave supply space in which the rotating antenna is located. , a configuration in which a plurality of coupling means for coupling the heating chamber and the transmission means are provided at substantially symmetrical positions with respect to the rotating antenna in the radio wave supply space and near a side wall of the heating chamber, the characteristics of the transmission means The impedance Z ₀₁ on the high frequency oscillator side and the impedance Z ₀₂ on the opposite side when viewed from the rotating antenna are configured to have different values, and the characteristic impedances of the two transmission means sandwiching the rotating antenna are different. By doing so, it is possible to adjust the amount of radio wave radiation from each coupling means into the heating chamber, which has the effect of improving the front-to-back or left-right heating balance within the heating chamber. DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below based on the drawings. In FIGS. 1, 2, and 3, 1 is a main body, and a heating chamber 2 is located inside. A front opening of the heating chamber provided for taking food in and out can be opened and closed by a door 3. Reference numeral 4 denotes a high frequency oscillator, and the radio waves oscillated thereby are transmitted through a waveguide 5 and radiated into the heating chamber from the bottom of the heating chamber through coupling holes 6 and 7 between the waveguide and the heating chamber and a rotating antenna 8. The rotating antenna 8 is provided approximately at the center of the bottom wall of the heating chamber, and consists of a vertical component 9 that is substantially perpendicular to the bottom wall of the heating chamber and a horizontal component 10 that is connected at a substantially right angle thereto. The horizontal component 10 forms a strip line together with the heating bottom wall, but since its tip is bent in a direction away from the heating chamber bottom wall, the radio waves transmitted by the strip line are radiated from there. The height dimension b of the waveguide 5 is made different between the high-frequency oscillator side 18 and the opposite side 19 when viewed from the rotating antenna, and as a result, the characteristic impedance Z ₀₁ and Z ₀₂ is a commonly known calculation formula It can be seen that there is a difference depending on a: Waveguide width dimension b: Waveguide height dimension λ _g : Guide wavelength λ: Free space wavelength

[Formula]: 377 Also, when using a strip line instead of a waveguide, its characteristic impedance Z ₀ is

Since it is calculated by [Formula], the characteristic impedance of the two transmission means parts can be changed by changing the a dimension (width dimension of the line). The coupling ports 6 and 7 are provided near the side wall of the heating chamber having a rectangular planar shape, and are arranged at substantially symmetrical positions with respect to the rotation axis of the rotary antenna. The portions of the bottom wall of the heating chamber where the coupling ports 6 and 7 are provided are slightly inclined toward the center of the heating chamber, which affects the direction of radio waves radiated into the heating chamber. The radio wave supply space of the heating chamber where the coupling ports 6 and 7 and the rotating antenna 8 are provided and the heating space where the food to be heated is accommodated are formed by a food mounting table 11 made of a dielectric material.
separated by. A rotary drive shaft 12 made of a dielectric material is connected to the vertical component 9 of the rotary antenna 8, and is rotationally driven by a motor 16 via pulleys 13, 14 and a belt 15. Reference numeral 17 denotes a sealing plate for sealing the opening in the bottom wall of the heating chamber through which the vertical portion 9 of the rotating antenna passes. The operation of the above configuration will be explained below. The radio waves oscillated by the high frequency oscillator 4 are transmitted through the waveguide 5 and are mainly radiated into the heating chamber from the horizontal tip of the rotating antenna 8. Since there is some radio wave radiation from the vertical part 9 of the rotating antenna,
A very good radio wave distribution can be obtained within the range of the rotation diameter of the rotating antenna. Therefore, if the oven has a square planar shape and the width and depth of the heating chamber are equal, a good radio wave distribution can be obtained with just the rotating antenna. If it is considerably larger than that, the end portion of the rotary antenna that deviates from the rotation diameter will be less likely to be heated. Therefore, auxiliary radio waves are radiated from the coupling ports 6 and 7 to heat the portions that are difficult to be heated by the rotating antenna. At that time, if the radio waves are transmitted to the coupling port 7 using a waveguide with uniform characteristic impedance, most of the radio waves will pass through the coupling port 6, so the amount of radio waves emitted from the coupling port 7 will be the amount of radio waves emitted from the coupling port 6. However, by making the height of the waveguide 19 smaller than that of the waveguide 18 as in the embodiment shown in FIG. 2, its characteristic impedance Z ₀₂ can be reduced. Since it is smaller than Z ₀₁ , it is possible to control the amount of radio waves transmitted up to the coupling port 7. Therefore, the amount of radio waves emitted from the coupling port 7 is equal to the amount of radio waves emitted from the coupling port 6. It can be adjusted so that they are approximately equal.
Furthermore, by suppressing the amount of radio waves transmitted through the waveguide 19, the amount of radio waves radiated from the rotating antenna 8 also increases, so that the radio wave uniformity effect of the rotating antenna is improved. The radio waves from coupling ports 6 and 7 are difficult to absorb directly into the food unless the heating chamber is filled with quite large food, so it is reflected by the upper wall of the heating chamber, etc., and is difficult to heat by the rotating antenna. It helps heat the top center, which allows even tall foods to be heated evenly. Furthermore, by changing the inclination angle of the coupling ports 6 and 7, the distribution pattern of the radio waves radiated from them can be changed, so by adjusting this angle and the size of the coupling ports, the radio waves from the rotating antenna can be It can effectively compensate for weak points in the distribution. Effects of the Invention According to the present invention as described above, the following effects can be obtained. 1. Because the distance between the radio wave radiation source and the food is close, a high percentage of the emitted radio waves are directly absorbed by the food, resulting in less loss of radio waves and high heating efficiency. 2 Even if the heating chamber has a rectangular planar shape, the radio waves from the coupling port provided auxiliary near the side wall on the bottom wall of the heating chamber center around the rotation axis of the rotating antenna.
It is possible to uniformly heat the edges of the heating chamber and the upper center of tall large foods. 3. By adjusting the angle of inclination of the coupling ports 6 and 7, it is possible to effectively compensate for the portion where heating by the rotating antenna is weak. 4. If the rotating antenna and coupling port are installed on the top wall of the heating chamber, a cover will be required to cover them, but since they are installed on the bottom wall and covered by the food table, a special cover is required to cover them. There is no need to provide a separate cover, and it can be done at low cost. 5 The characteristic impedance Z ₀₂ of the waveguide 19 is set to 18
By making the characteristic impedance Z ₀₁ smaller, the amount of radio wave radiation from the coupling port 7 is reduced
Since it can be adjusted to be almost equal to the amount of radio wave radiation from the radiator, it is possible to improve the left and right heating balance. 6 Furthermore, by reducing the amount of radio waves transmitted through the waveguide 19, the amount of radio waves radiated from the rotating antenna 8 increases, and the radio wave uniformity effect of the rotating antenna can also be improved. 7. By reducing the height of the waveguide 19, the space between the waveguide and the bottom of the body becomes larger, making it easier to store necessary parts, such as a small motor for rotating the antenna, in this space. As a result, the overall height of the product can be reduced.

[Brief explanation of the drawing]

FIG. 1 is an external view of a high-frequency heating device according to an embodiment of the present invention, FIG. 2 is a cross-sectional view showing the essential parts, and FIG. 3 is an external view of the device viewed from below. 1... Main body, 2... Heating chamber, 4... High frequency oscillator, 6, 7... Coupling port, 8... Rotating antenna, 1
1... Food mounting table, 18, 19... Waveguide.

Claims (1)

[Scope of Claims] 1. A heating chamber for storing food, a high-frequency oscillator for supplying high-frequency waves into the heating chamber, a transmission means for transmitting radio waves oscillated by the high-frequency oscillator, and a heating chamber for storing food. a rotating antenna that connects the heating chamber and the transmission means at approximately the center of the bottom wall of the heating chamber; a food mounting table that separates the heating chamber into a heating space and a radio wave supply space in which the rotating antenna is located; A plurality of coupling means for coupling the transmission means are arranged at substantially symmetrical positions with respect to the rotating antenna in the radio wave supply space and near the side wall of the heating chamber, and the characteristic impedance of the transmission means is set to the rotational antenna. A high-frequency heating device configured such that Z ₀₁ on the high-frequency oscillator side and Z ₀₂ on the opposite side as viewed from the antenna have different values. 2. The high frequency heating device according to claim 1, wherein the value of characteristic impedance Z ₀₂ is smaller than the value of Z ₀₁ . 3. The high-frequency heating device according to claim 1, wherein the transmission means is composed of a waveguide, and the height dimension b of the waveguide is made different in order to make the characteristic impedances Z ₀₁ and Z ₀₂ different values. . 4 In order to configure the transmission means with a strip line and make the characteristic impedances Z ₀₁ and Z ₀₂ different values,
The high frequency heating device according to claim 1, wherein the width dimension a of the strip lines is made different.