JPH0129314B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to uniform heating in a high frequency heating device.

The uniform heating means of the high-frequency heating device includes a stirrer that diffusely reflects high-frequency energy, a rotating antenna that radiates high-frequency energy while rotating, a turntable that rotates the object to be heated, and a large number of high-frequency supply ports on the peripheral wall of the heating chamber. It is known that it was made into However, all of these products had the drawback that they could not be put into practical use unless they were cut and tried, which required a lot of manpower and a long period of study.

The present invention has been made in order to eliminate the above-mentioned drawbacks, and an object of the present invention is to provide a high-frequency heating device that can achieve uniform heating using 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. In the drawing, 1 is a high frequency oscillator that generates high frequency energy, and 2 is a waveguide that connects the high frequency oscillator 1 to a heating chamber 3. The heating chamber 3 is made of a metal plate in the shape of a rectangular parallelepiped. The waveguide 2 is also made of a metal plate in the shape of a rectangular parallelepiped, and is attached to the outside of the ceiling wall of the heating chamber 3 in parallel to the ceiling wall. A turntable 5 is provided at the lower part of the heating chamber 3 on which a heated object 4 such as food is placed and rotated. There are two high-frequency radiation ports 6 on one side of the waveguide 2 in the part that connects to the heating chamber 3.
7, one high frequency radiation port 6 is opened at the tip of the waveguide 2, and the other high frequency radiation port 7 is opened near the end of the heating chamber 3. The other side of the waveguide extends beyond the outer edge of the heating chamber ceiling;
The above-mentioned high frequency oscillator 1 is attached to the end thereof. In addition, the dimensions B and D of the above-mentioned two high-frequency radiation ports 6 and 7 in the axial direction of the waveguide 2 and the dimension C of the partition part 8 that separates the above-mentioned two high-frequency radiation ports 6 and 7 are summed. Use dimensions B + C + D. Wavelength λ
λ/2 to λ+λ/4, and the dimension C of the partition portion 8 is set to λ/8 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 dimension E 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 λ/2 to λ+λ/
I will explain why I chose 4. 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 between λ/2 and λ.
At least λg/2 is included within the range of +λ/4. Specifically, in a household high-frequency heating device called a microwave oven, λ = 122 mm.
(corresponds to frequency 2450MHz), λ/2 to λ+λ/
4 is 61 to 153 mm, and the a dimension is generally 96, 80, and 70 mm. For a=96mm, λg/2=79
mm, within the range of 61<B+C+D<153mm, the maximum magnetic field positions are at the tip and 79mm in the waveguide axis direction, and the minimum magnetic field positions are 39.5mm and 118.5mm.
There are two locations. 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 into 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 with poor high frequency emissivity.
In practice, when a=96 mm, the minimum dimension of B+C+D is 79 mm, which corresponds to λg/2.

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 near 95 mm, respectively, and the partition part 8 is Place it near the minimum magnetic field position of 47.5mm. In practice, when a=80 mm, the minimum dimension of B+C+D is 95 mm, which corresponds to λg/2.

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 located at the tip of the waveguide, which is the maximum magnetic field position, and near 126 mm, respectively, 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 λg/2.

The reason why the dimension C of the partition portion 8 is set to λ/8 or more will be explained. The wavelength λ used for the high frequency heating device is 122
mm (corresponding to frequency 2.450MHz), λ/
8 is approximately 15mm. This 15mm is the partition part 8 in a household high-frequency heating device called a microwave oven.
When manufactured from painted iron plate or stainless steel, it is induced by a high-frequency magnetic field when 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. This is necessary to prevent problems such as discoloration and deformation of the partition 8 due to abnormal heating caused by loss due to high-frequency current flowing on the surface of the partition 8, and the dimension C of the partition 8 in the waveguide axis direction is It has been experimentally confirmed that there is no problem in practical use if the thickness is 15 mm or more.

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 near the end of the heating chamber 3, and then the remaining high-frequency energy is transmitted to the high-frequency energy at the tip of the waveguide 2. The radiation is emitted from the radiation port 6 into the heating chamber 3 . Therefore, the radiation is uniformly radiated near the center of the heating chamber 3 and near the peripheral wall, that is, in the radial direction of the turntable 5, and uneven heating can be reduced. Needless to say, heating unevenness in the circumferential direction can be reduced by rotating the turntable 5.

Furthermore, in the case of milk stored in a tall cup or milk bottle, or sake stored in a tall sake bottle, uneven heating tends to occur in the vertical direction, but the difference between the tip of the waveguide 2 and the side wall of the heating chamber 3 By selecting the distance A, it is possible to prevent the above-mentioned milk or alcohol from coming directly under the high-frequency radiation port 6, thereby reducing uneven heating in the vertical direction. To do this, it is necessary to make the distance A between the tip of the waveguide 2 and the side wall of the heating chamber 3 directly below the waveguide 2 smaller than 1/2 of the width of the heating chamber 3 in the axial direction of the waveguide, and to emit high-frequency radiation. The opening 7 may be placed as close to the end of the heating chamber 3 as possible.

In a household microwave oven, the width of the heating chamber is 270mm.
~400mm. As mentioned above, when a=96 mm, the minimum dimension of B+C+D is 79 mm, and the dimension obtained by adding the minimum dimension of E, 15 mm, is 94 mm. This 94mm is the minimum dimension of A (=B+C+D+E) and is 1/2 of the minimum width of the microwave oven mentioned above, 270mm.
It can be realized shorter than 135mm. Similarly, a=
At 80 mm, the minimum A dimension is 110 mm, which can be realized to be shorter than 1/2 of the above-mentioned minimum width. However, a
= 70mm, the minimum A dimension is 141mm, so it applies when the width of the heating chamber is 282mm or more.

As described above, according to the present invention, a waveguide is attached to the outside of the ceiling of the heating chamber, two high-frequency radiation ports are provided, and one high-frequency radiation port is used as the tip of the waveguide.
The other high-frequency radiation port is located near the side wall of the heating chamber directly below the waveguide, and the distance between the tip of the waveguide and the side wall of the heating chamber directly below the waveguide is 1/2 the width of the heating chamber in the axial direction of the waveguide. It is easy to reduce heating unevenness in the radial direction, circumferential direction, and vertical direction of tall objects to be heated on the turntable by simply making the heating smaller, reducing the manpower and time required to improve heating unevenness. This is advantageous in manufacturing.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a main part of an embodiment of the high-frequency heating device of the present invention, and FIG. 2 is a top view of FIG. 1 viewed from the XY direction. 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: a high-frequency oscillator, a heating chamber, a waveguide that connects the high-frequency oscillator to the heating chamber and supplies high-frequency energy to the heating chamber, and places an object to be heated in the heating chamber and rotates it. In a high-frequency heating device equipped with a turntable, the waveguide 2 is arranged outside the ceiling of the heating chamber 3 and along the ceiling wall, and one end thereof is connected to two high-frequency radiation ports 6 in the ceiling wall. , 7 to the heating chamber, the other end of which extends beyond the outer edge of the ceiling wall, and the high frequency oscillator 1 is attached to the end of the high frequency oscillator 1, one of the two high frequency radiation ports of the ceiling wall. The position 6 is the tip of the waveguide, and the other high-frequency radiation port 7 is near the side wall of the heating chamber on the side where the high-frequency oscillator is installed, and the tip of the waveguide on the ceiling of the heating chamber and the A high-frequency heating device characterized in that a distance A between the side wall of the heating chamber on which the high-frequency oscillator is attached is smaller than 1/2 of the width of the heating chamber in the tube axis direction of the waveguide.