JPS648915B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to uniform heating in a high frequency heating device.

Known methods for uniform heating in high-frequency heating devices include a stirrer that diffusely reflects high-frequency waves, a rotating antenna that emits high-frequency waves, a turntable that rotates the object to be heated, and a method of providing a large number of high-frequency supply ports on the peripheral wall of the heating chamber. . In any case, through a large number of cut-and-try experiments, the heating unevenness has been reduced to the extent that it can be put to practical use, but it has the drawback of requiring manpower and a considerable period of study time.

The present invention solves the above-mentioned drawbacks, and aims to provide a high-frequency heating device that achieves uniform heating with simple means.

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 1 is a schematic cross-sectional view of a main part showing an embodiment of the high-frequency heating device of the present invention, and FIG. 2 is a top view as seen from the XY direction of FIG. 1. 1 is a high frequency oscillator that generates high frequency energy; 2 is a waveguide that connects the high frequency oscillator 1 to the heating chamber 3; The heating chamber 3 and the waveguide 2 are formed from metal plates. A heated object 4 such as food is placed at the bottom of the heating chamber 3.
A turntable 5 is provided on which to place and rotate. Two high-frequency radiation ports 6 and 7 are provided in the part where the waveguide 2 is connected to the heating chamber 3. One high-frequency radiation port 6 is used as the tip of the waveguide 2, and the other high-frequency radiation port 7 is heated. A partition part 8 is located at the end of the chamber 3 and separates the dimensions B and D of the two high-frequency radiation ports 6 and 7 in the axial direction of the waveguide 2 from the two high-frequency radiation ports 6 and 7. Dimension B+C+D, which is the sum of dimension C, is 1/2λ~ for the wavelength λ used.
Set it to λ+1/4λ. At the same time, the dimension C of the partition portion 8 is set to be 1/8λ or more. Reference numeral 9 denotes a screw for joining the lower plate of the waveguide 2 and the upper wall end of the heating chamber 3. The dimension E of the mounting part of the screw 9 needs to be 15 mm or more from the viewpoint of ease of manufacture.

The total dimension B + C + D of the dimensions B and D of the high frequency radiation ports 6 and 7 and the dimension C of the partition part is 1/2λ to λ + 1/4λ
Explain why. The internal wavelength λg in the waveguide 2 is larger than the used wavelength (free space wavelength) λ, and increases as the long side dimension a becomes narrower.In a waveguide of practical size, it is 1/2λ~λ+
At least 1/2λg is included within the range of 1/4λ. Specifically, in a household high-frequency heating device called a microwave oven, λ = 122 mm (corresponds to a frequency of 2450 MHz), and 1/2 λ to λ + 1/4 λ is 61
~153mm, and the a dimension is generally 96, 80, and 70mm. For a=96mm, 1/2λg=79mm,
Within the range of 61<B+C+D<153 mm, the maximum magnetic field positions are at the tip and 79 mm in the waveguide axis direction, and the minimum magnetic field positions are at two positions at 39.5 mm and 118.5 mm. At the position of the maximum magnetic field, the wall current in the waveguide axis direction perpendicular to the magnetic field also reaches its maximum. By providing the high-frequency radiation ports 6 and 7 to cut off this wall current, high-frequency energy can be efficiently radiated toward the inside of the heating chamber 3 from the high-frequency radiation ports 6 and 7. Therefore, when a = 96 mm, the high frequency radiation ports 6 and 7 are located at the tip of the waveguide, which is the maximum position of the magnetic field, and at 79 mm.
Place it around mm. The partition part 8 is arranged near the minimum position of 39.5 mm in the magnetic field where high frequency radiation efficiency is poor. Since the wall current is small near the minimum magnetic field position, there is no risk of deformation or melting of the partition section 8 due to abnormal heating. In practice, when a=96mm, the minimum dimension of B+C+D is 1/2
It is 79 mm corresponding to λg.

Similarly, if a=80mm, 61<B+C+D<
There are two maximum magnetic field positions and two minimum magnetic field positions within a range of 153 mm, but the high-frequency radiation ports 6 and 7 are located at the tip of the waveguide, which is the maximum magnetic field position, and at around 95 mm, and the partition part 8 is Place it near the minimum magnetic field position of 47.5mm. In practice, when a=80mm, the minimum dimension of B+C+D is 95mm, which corresponds to 1/2λg.

Also, if a=70mm, 61<B+C+D<
There are two maximum magnetic field positions and one minimum magnetic field position within the range of 153 mm, but the high frequency radiation ports 6 and 7 are placed at the tip of the waveguide, which is the maximum magnetic field position, and near 126 mm, and the partition part 8 is Place it near the minimum magnetic field position of 63mm. In practice, when a=70 mm, the minimum dimension of B+C+D is 126 mm, which corresponds to 1/2λg. In a household microwave oven, the width of the heating chamber is approximately 270 mm to 400 mm. As mentioned above, when a=96mm, B+C
The minimum dimension of +D is 79 mm, and the addition of the minimum dimension of E, 15 mm, is 94 mm. This 94mm is A
(=B+C+D+E), which is the minimum dimension, and can be made shorter than 135 mm, which is 1/2 of the minimum width of 270 mm of the above microwave oven. Similarly, when a=80mm, the minimum A dimension is 110mm, and when a=70mm, the minimum A dimension is 141mm. In this way, a=96, 80,
In any case of 70mm, the distance A between the tip of the waveguide 2 and the side wall of the heating chamber 3 can be shortened to approximately 1/2 of the width of the heating chamber of an actual microwave oven in the waveguide axis direction, which saves space. , which is advantageous in terms of cost.

Note that even if the A dimension is within approximately 1/2 of the heating chamber 3, the object to be heated 4 is rotated and moved by the turntable 5, so that the entire surface of the object to be heated 4 can be uniformly irradiated with high-frequency energy. .

The wavelength λ used for the high-frequency heating device is 122 mm (frequency
2450MHz), 1/8λ is approximately 15mm. This 15 mm is when the partition part 8 is made of painted iron plate or stainless steel in a household high-frequency heating device called a microwave oven.
This is the minimum size necessary to prevent inconveniences such as discoloration and deformation due to abnormal heating in a state where the object to be heated 4 is forgotten to be placed in the heating chamber 3 which supplies high frequency energy of 500W to 700W, that is, in an empty firing state. In practice, dimension C needs to be larger than 15 mm. Dimensions B and D differ in size from each other by moving the position of dimension C.

Next, the functions and effects of the high frequency heating device of the present invention will be explained. The high-frequency energy heading from the high-frequency oscillator 1 toward the heating chamber 3 is first radiated into the heating chamber 3 from the high-frequency radiation port 7 at the end of the heating chamber 3, and then the remaining high-frequency energy is radiated into the high-frequency radiation at the tip of the waveguide 2. It is radiated into the heating chamber 3 from the opening 6. By adjusting the radiation ratio of high frequency energy by making the sizes of the high frequency radiation ports 7 and 6 different from each other, uneven heating of the turntable 5 in the radial direction can be practically reduced even when the heating conditions change. Needless to say, heating unevenness in the circumferential direction can be reduced by rotating the turntable 5.

As described above, according to the present invention, in a high-frequency heating device equipped with a turntable, two high-frequency radiation ports are provided and the sizes of the ports are made different to adjust the radiation ratio of high-frequency energy. , it is easy to practically reduce the heating unevenness of the turntable in the radial direction, it is possible to reduce the manpower and time required to improve the heating unevenness, it is advantageous in manufacturing, and it is possible to reduce the partition part separating the two radiation ports. Since it is located at a position approximately 1/4 of the wavelength in the tube from the tip of the waveguide axis, it provides a safe waveguide coupling structure that will not be deformed or melted due to abnormal heating during dry firing of the partition.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of a main part showing an embodiment of the high-frequency heating device of the present invention, and FIG. 2 is a top view as seen from the XY direction of FIG. 1. 1... High frequency oscillator, 2... Waveguide, 3... Heating chamber, 5... Turntable, 6, 7... High frequency radiation port.

Claims (1)

[Claims] 1 High frequency oscillator 1 that generates high frequency energy
In a high-frequency heating device that includes a waveguide 2 that connects the high-frequency oscillator 1 to a heating chamber 3 and a turntable 5 that rotationally moves the object to be heated 4, the waveguide 2 is installed on the upper surface side of the heating chamber 3. Two high-frequency radiation ports 6 and 7 of different sizes are connected to each other at the joint.
A high-frequency heating device characterized in that a partition part 8 separating the radiation ports 6 and 7 is arranged at a position near the tip of the waveguide 2 at about 1/4 of the wavelength in the pipe.