JPS648916B2 - - 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.
λ+1/4λ and dimension C of partition part 8 to 1/8
λ 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 mounting part dimension E of screw 9 is 15 mm for ease of manufacturing.
The above is necessary.

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 it increases as the long side dimension a becomes narrower, but in a waveguide of practical size, it is 1/2 λ to 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 frequency 2450MHz), 1/2λ to λ+1/4λ
is 61 to 153 mm, and the a dimension is generally 96, 80, and 70 mm. For a=96mm, 1/2λg=79mm
In the range of 61<B+C+D<153mm, the maximum magnetic field position is between the tip and 79mm in the waveguide axis direction.
The minimum magnetic field positions are 39.5mm and 118.5mm. 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 arranged near the tip of the waveguide and 79 mm, respectively, where the magnetic field is maximum. 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. In practice, when a=96 mm, the minimum dimension of B+C+D is 79 mm, which corresponds to 1/2λg.

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 minimum dimension of E, 15 mm, is added to this, resulting in a dimension of 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 reason why the dimension C of the partition portion 8 is set to 1/8λ or more will be explained. The wavelength λ used for the high frequency heating device is 122
mm (corresponding to frequency 2450MHz), 1/8λ
is approximately 15mm. This 15 mm is a household high-frequency heating device called a microwave oven, and when the partition part 8 is made of painted iron plate or stainless steel, the heated object 4 is placed inside the heating chamber 3 which supplies high-frequency energy of 500W to 700W. This is necessary to prevent inconveniences such as discoloration and deformation due to abnormal heating in the state where you forget to add the product, that is, in the dry firing state.
This is the minimum dimension, and for practical purposes, dimension C needs to be larger than 15 mm.

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. Partition part 8
By adjusting the dimension C and position of the high-frequency radiation ports 7 and 6, the radiation ratio of high-frequency energy between the high-frequency radiation ports 7 and 6 can be adjusted, and uneven heating of the turntable 5 in the radial direction can be reduced. 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, the dimensional range of the high-frequency radiation opening and where to adjust it are clear, so it is possible to reduce the manpower and time required to improve uneven heating. There is little heating unevenness in the direction, and the distance between the tip of the waveguide, which has two radiation ports with high radiation efficiency, and the side wall of the heating chamber is short, approximately within half the width of the heating chamber of an actual microwave oven. It is possible to provide a high-frequency heating device that is advantageous in terms of space and cost, and has great effects when implemented.

[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, 4... Heated object, 5... Turntable,
6, 7... High frequency radiation port, 8... Partition part, B,
C, D...Dimensions of each high frequency radiation port and partition.

Claims (1)

[Claims] 1 High frequency oscillator 1 that generates high frequency energy
In a high-frequency heating device including a waveguide 2 that connects the high-frequency oscillator 1 to the heating chamber 3 and a turntable 5 that rotationally moves the object to be heated 4, the waveguide 2 and the heating chamber 3 are connected to each other. Two high-frequency radiation ports 6, 7 are provided in the waveguide, and dimensions B and D of the two high-frequency radiation ports 6, 7 in the waveguide axis direction are separated from the two high-frequency radiation ports 6, 7. A high-frequency heating device characterized in that the total dimension (B+C+D) of the dimension C of the partition portion 8 is set to 1/2 to 5/4 of the wavelength used.