JPS59194390A - High frequency heater - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

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

Conventionally, as a uniform heating means for high frequency heating equipment.

Stirrers that diffusely reflect high-frequency waves, rotating antennas that radiate high-frequency waves, turntables that rotate and move objects to be heated, and devices that have multiple high-frequency radiation ports in the heating chamber are known, but none of them fully satisfies uniform heating. There are few.

The present invention has been made to eliminate the above-mentioned drawbacks, and its purpose is to obtain a high-frequency heating device that satisfactorily achieves uniform heating. Therefore, by combining two high-frequency radiation ports with different shapes provided on the ceiling of the heating chamber and a turntable, the object to be heated is irradiated with high-frequency energy evenly, and in particular, the central part of the object to be heated is heated. This solves the shortage.

Two embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of a main part showing one embodiment of the present invention, and FIG.
This figure is a plan view of the main parts of the vicinity of the high-frequency radiation opening on the ceiling of the heating chamber in FIG. 1, when viewed from above. FIGS. 5 and 4 show heating temperature characteristics at the center of the object to be heated and heating unevenness characteristics of the object due to differences in the dimensions of the high-frequency radiation openings.

The present invention will be explained in detail with reference to FIGS. 1 and 2.

1 is a high frequency oscillator that generates high frequency energy.

A waveguide 6 connects the high frequency oscillator 1 to the heating chamber 2. The heating chamber 2 and the waveguide 6 are formed from metal plates. At the bottom of the heating chamber 2, there is provided a tar/table 5 on which a nuclear toner 4 such as food is placed and rotated. Two high frequency radiation ports 6 and 7 are provided at the portion where the waveguide filter is connected to the heating chamber 2.

One of the high-frequency radiation ports 6 is used as the tip of the waveguide B.

The position of the other high-frequency radiation lower is λg/2±λg/4 (λg is the wavelength inside the tube) from the high-frequency radiation opening 6 at the tip of the waveguide 6, and λ/2±λ/4 from the heating chamber wall surface 8. (
Installed at a distance of λ (where free space wavelength), dimension A of the radiation lower in the waveguide axis direction is λg/12 or more, dimension B of the same side for high frequency radiation is λg/12 or more, and dimension C of the other side. λg
/3±λg/6. It is said that In addition, the above-mentioned high frequency radiation port 6
, 7 are provided approximately on the center line of the front and rear of the heating chamber.

Next, FIG. 3 shows the operation in the above embodiment.

This will be explained with supplementary reference to FIG.

The reason why the high frequency radiation ports 6 and 7 are positioned λg/2±λg/4 apart from the tip of the waveguide 3 will be explained. It is known that in the waveguide 3, the magnetic field strength is at its maximum at the tip, and also reaches its maximum at a position λg/2 from the tip. Accordingly.

It goes without saying that the magnetic field strength is maximized at the high-frequency radiation port 6 provided at the tip, but the magnetic field of the high-frequency radiation lower can also be at its maximum or close to the maximum, so high-frequency radiation can be efficiently transmitted from the high-frequency radiation ports 6 and 7. Energy can be radiated into the heating chamber 2.

The position of the high frequency radiation lower is λ/2±λ/ from the heating chamber wall surface 8.
The reason why it is set as 4 will be explained. In the heating chamber 2, the magnetic field strength reaches its maximum at λ/2 from the heating chamber wall surface 8, so the degree of coupling is good, and the high frequency energy radiated from the high frequency radiation lower is efficiently radiated into the heating chamber 2. In other words, it is very easy to match the high frequency radiation lower part 1 provided in the waveguide 3 with the heating chamber 2.

The reason why the same dimension A of the high frequency radiation lower is set to λg/12±λg/24 will be explained with reference to FIG. In FIG. 6, the heating temperature increase value at the center of the object to be heated is plotted on the vertical axis, and it shows that the temperature at the center increases relative to the temperature of the entire object to be heated as it goes upward. The horizontal axis indicates a dimension obtained by varying the same dimension A of the high-frequency radiation lower with a center at a position λ/2 from the heating chamber wall surface 8. As shown in FIG. 3, as the 5th dimension A becomes smaller, the temperature at the center becomes higher. A, -0, that is, when the high frequency radiation opening 6 is completely closed, the central portion becomes lower. I did not actually measure it because there is a concern that sparks will occur if it is still below λg/12,
It seems to exhibit characteristics as shown by the dotted line in FIG.

When heating the object 4 with high frequency energy, if insufficient heating occurs in the center due to uneven radiation, the heating time must be increased to compensate for this insufficient heating. This may cause uneven heating such as dehydration around the object to be heated or, in severe cases, carbonization. Therefore, eliminating insufficient heating in the center of the object to be heated is an effective means for eliminating uneven heating. Therefore, as shown in Figure 5,
When considering the occurrence of sparks, etc., it can be seen that when A=λg/12, the heating temperature rises at the center of the object to be heated 4 is large, which is the best dimension.

However, A needs to be 7712 or more due to spark issues.

Next, the same dimension B of the high frequency radiation lower is 7g712 or more.

The reason why the same dimension C is set to λg/3±λg/6 will be explained. As mentioned above, if the dimension B is set to λg/12 or less, sparks will be generated, so it is practically required to be 26712 or more. The dimension C in one direction is varied as shown in Fig. 4,
Examining the state of uneven heating of the heated object 4 at this time, λg
The actual measurement results show that the degree of unevenness is the least near 15, and that the degree of unevenness increases even if the length is shortened or lengthened around this point. Based on these results, the same dimension C is λg/
It was decided to set it to 3±λg/6.

As described above, according to the present invention, two high-frequency radiation ports are provided at the joint between the waveguide and the heating chamber, two trapezoidal high-frequency radiation ports are provided at the tip of the waveguide, and the other rectangular slot-shaped high-frequency radiation port is provided at the tip of the waveguide. The high frequency radiation opening is approximately λg/2 from the former high frequency radiation opening provided at the tip of the waveguide. By installing the heating chamber at a distance of λg/2 from the wall surface, in combination with the turntable, the object to be heated is irradiated with high-frequency energy evenly, which eliminates insufficient heating especially in the center of the object and reduces uneven heating. It is possible to provide a high-frequency heating device with reduced .

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a main part of a high-frequency heating device showing an embodiment of the present invention, and FIG. 2 is a plan view of the main part of a high-frequency heating device when viewed from x-x' in FIG. FIG. 3 and FIG. 4 are a temperature characteristic diagram and a heating unevenness characteristic diagram of the central part of the object to be heated when the dimensions of the high-frequency radiation opening are changed, respectively. 1...High frequency oscillator. 2...Heating chamber. 6... Waveguide. 4...Object to be heated. 5... Turntable. 6.7 ...High frequency radiation port. 8... Heating chamber wall surface. A - Dimension of the radiation lower in the waveguide axis direction. B: One dimension of the radiation port 6 in the waveguide axis direction. C... Dimensions of the same other side. Applicant: Hitachi Thermal Equipment Co., Ltd. Figure 1 Figure 2 431- Figure 3 Figure 4 Dimensions C

Claims (1)

[Claims] A high frequency oscillator (1) that generates high frequency energy. In a high-frequency heating device including a waveguide (6) that connects the high-frequency oscillator (1) to a heating chamber (2) and a turntable (5) that rotationally moves the object to be heated (4), the waveguide (3) and the heating chamber (2) are provided with two high-frequency radiation ports (6), σ), and one high-frequency radiation port (6) is positioned at the tip of the waveguide (5). , the other high-frequency radiation port (the force position is the radiation port (6) at the tip of the waveguide (3)
From λg//2±λg/4 (λg is the tube wavelength), and
It is installed at a distance of λ/2±λ/4 (λ is the free space wavelength) from the heating chamber wall surface (8), and the dimension (2) of the radiation port (7) in the waveguide axis direction is λg/12 or more, and the radiation The dimension of the same side of the mouth (6) is 26712 or more. A high frequency oscillator # characterized in that the other dimension (C1) is λg/3±λg/6.