JPS6037837Y2 - High frequency heating device - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a high-frequency heating device that has an improved excitation section that radiates high-frequency power into an oven.

[Technical background of the invention and its problems]

Conventionally, in a high-frequency heating device such as a microwave oven, as shown in FIG. The microwaves emitted from the excitation port 5 are stirred and radiated into the oven 3 by a stirrer fan 7 provided in a partitioned space partitioned by a partition plate 6 at the oven ceiling.

As a result, the food 9 placed on the shelf board 8 in the oven 3
is heated using microwaves to prepare food.

In such a microwave oven, it is difficult to improve the non-uniformity of the temperature distribution inside the oven 3, and since it is necessary to stir with the stirrer fan 7, the height of the partition space becomes large, and the temperature distribution inside the oven 3 increases. The effective volume inside becomes narrower.

In other words, in order to secure the necessary effective volume inside the oven 3, the outer diameter of the oven must be increased.

[Purpose of invention]

The present invention was developed to solve the above-mentioned problems, and is a high-frequency heating device that can improve the temperature unevenness inside the oven, expand the effective volume inside the oven, and downsize the entire oven. The purpose is to provide

[Summary of the idea]

In order to achieve the above object, the present invention provides an oven having a circular opening formed in the ceiling surface, a hollow box disposed above the oven so as to cover the opening, and the hollow box. a high-frequency oscillator connected to the other end of the waveguide; This device includes a circular substrate made of a dielectric material and a rotating disk formed of a metal plate fixed to the substrate with a cross-shaped slit for microwave excitation.

[Example of idea]

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

2 and 3 show a high-frequency heating device according to an embodiment of the present invention, and the same parts as in FIG. 1 described above are given the same reference numerals and will be explained.

In the figure, 1 is a magnetron that generates microwaves, 2 is a waveguide for guiding this microwave, and 11 is this waveguide 2.
It is a hollow box that guides microwaves from the waveguide 2.

Further, a circular opening (excitation part) 12 is formed in the ceiling surface 4 of the oven 3.

The hollow box 11 is disposed above the oven 3 so as to cover the opening in the ceiling of the oven 3.

Furthermore, a rotating disk 13 is provided within the ceiling opening 2 of the oven 3, which is arranged substantially concentrically with the opening 12 and is rotationally driven by a motor or wind force.

This rotating disk 13 and the ceiling opening 12 of the oven 3
is separated from the space inside the oven 3 by a partition plate 6 attached to the ceiling surface 4 of the oven 3 from below.

Further, inside the oven 3, food 9 to be cooked is placed on a shelf board 8 as described above.

On the other hand, as shown in FIGS. 4 and 5, the rotating disk 13 is made of a circular substrate 14 made of a low dielectric material such as polypropylene or polycarbonate.
It is formed of a relatively lightweight metal plate 15, such as aluminum, which is fixed on this substrate 14 with a cross-shaped slit 16 for microwave excitation left.

In the high frequency heating device having such a configuration, the microwaves generated from the magnetron 1 are transmitted from the waveguide 2 to the hollow box 1.
1 and is radiated to the oven 3 through the slit portion 16 of the rotating disk 13, and the food 9 placed on the shelf board 8 is heated and cooked by this microwave energy.

In this case, since the rotating disk 13 is rotationally driven by a motor or wind power, the rotating disk 13 is
It is possible to make the temperature distribution of the oven 3 uniform by radiating it into the oven 3 through the slit 16 while rotating it.

Here, since the slit 16 of the rotating disk 13 is cross-shaped, it becomes the same shape each time it rotates to l, and the fluctuation in impedance seen from the antenna of the magnetron 1 can be reduced (that is, the reflected power returning to the antenna can be reduced). It becomes less.

) The impedance matching between the waveguide side and the oven side is relatively good.

In addition, due to the operating characteristics of the magnetron 1, this makes it easier to set the operation at the position where the output is output and at a dense frequency band, which improves the heating efficiency and makes it possible to effectively and uniformly heat the food 9. I can do it.

Note that if the gap A (see FIG. 2) between the rotating disk 13 and the opening 12 in the oven ceiling surface 4 is too large, the slit 16
Since microwaves are radiated into the oven 3 from this gap A before they are radiated from the oven 3,
The temperature distribution within the room tends to deteriorate.

Regarding this point, as a result of experiments, if the wavelength of the microwave is input, and the distance of this gap A is approximately λ/8 or less,
It has been found that the microwave radiation is reduced from this gap A.

Therefore, when the frequency of the microwave generated from the magnetron 1 is, for example, 2450 MHz, the gap A is set to be less than I/8, that is, within about 15 rIrIrL.

Further, in the present invention, for example, as shown at 17 in FIG. 4, radio waves excited by the slit 16 of the rotating disk 13 are radiated into the oven 3.

Moreover, by setting the diameter of such a rotating disk 13 to B, and making this diameter B an odd multiple of approximately λ/2,
The maximum electromagnetic wave is always generated at the center of the slit 16, which makes it possible to make the temperature at the center of the oven higher than the surroundings, so that temperature unevenness in the oven 3 can be improved.

In other words, it has been experimentally shown that if the temperature rise in the center of the oven 3 is made higher than the temperature rise in the surrounding area, the temperature unevenness of the food can be improved.
If the above-mentioned predetermined dimensions are set, temperature unevenness can be improved.

Furthermore, since the height of the partition space can be reduced without using the conventional star fan, the oven capacity can be expanded without increasing the outer diameter of the oven.

Next, the results of a temperature distribution test and an actual sponge cake made using the high-frequency heating device using the rotating disk 13 as described above will be shown below.

Here, in the temperature distribution test, as shown in FIG. 6, five water loads were placed at the center of the shelf board 8 and around it as shown in the figure, and the heating time was set at 2 minutes and 3 ce.

However, the temperature distribution rate is expressed by the following formula.

Distribution rate = (Maximum temperature rise value - Minimum temperature rise value) ÷ (Average temperature rise value) x 100% In other words, Table 1 shows that the width C of the slit 16 is 25 mm (constant) and the diameter dimension B of the rotating disk 13 is changed. This shows the case where

Note that the difference in swelling thickness of the sponge cake refers to the difference between the maximum height and the minimum height of the sponge cake after cooking.

From Table 1 above, the diameter 8 dimension is λ/2 (input = approximately 122T
When rrIn, λ/2 = approximately 2 = rrvn ) times 3 (
It can be seen that the temperature distribution is uniform when B = 180rrrrn, which is approximately equal to approximately 183mm).

Also, at this time, the center and surrounding areas inside the oven are heated uniformly.

Therefore, it can be seen that the difference in swelling thickness of the sponge cake is the smallest and the cooking finish is good. Also, Table 2 below shows that the diameter dimension B of the rotating disk 13 is 18ONn.
The test results are shown in the case where the width C of the slit 16 was changed while keeping it constant at (the above-mentioned optimum value).

From Table 2 above, the dimension of the slit width C is approximately λ/4 (approximately 30 m
It can be seen that if the temperature is within m), the temperature distribution will be more uniform and the finished product of the sponge cake will be better.

Therefore, it is preferable that the slit width C provided in the rotating disk 13 of the device of the present invention is approximately equal to or less than 1/4.

[Effect of idea]

As explained above, according to the present invention, a hollow box is disposed above the oven in which a circular opening is formed in the ceiling surface so as to cover the opening, and a waveguide is connected to the hollow box. A high-frequency oscillator is connected to the oven ceiling through a circular substrate made of a low dielectric material in the opening in the oven ceiling, and a metal plate fixed to the substrate with a cross-shaped slit for microwave excitation. Since the formed rotating disk is rotatably arranged approximately concentrically with the opening in the oven ceiling, the microwaves radiated into the oven through the slits are radiated toward the food while rotating. The food placed in the oven can be heated uniformly, and the effective volume inside the oven can be expanded and the oven as a whole can be made smaller.

In addition, since the cross-shaped slit for microwave excitation returns to its original shape after one rotation, it is possible to ensure relatively good impedance matching between the waveguide side and the oven side. As a result, the temperature at the antenna portion of the high-frequency oscillator is reduced, which improves reliability over its lifetime and improves heating efficiency for food.

[Brief explanation of the drawing]

Figure 1 is a schematic cross-sectional view of a conventional high-frequency heating device;
3 and 3 show a high frequency heating device according to an embodiment of the present invention, FIG. 2 is a plan view thereof, FIG. 3 is a sectional view thereof, and FIGS. The rotating disk is shown in detail; FIG. 4 is a plan view thereof, FIG. 5 is a sectional view thereof, and FIG. 6 is a plan view of a shelf board on which a water load is placed in a temperature distribution test of the present device. In the figure, 1 is a magnetron, 2 is a waveguide, 3 is an oven,
4 is a ceiling surface, 6 is a partition plate, 9 is food, 11 is a hollow box, 1
2 is an opening, 13 is a rotating disk, 14 is a substrate, 15 is a metal plate, and 16 is a slit.

Claims (1)

[Scope of claims for utility model registration] 1. An oven with a circular opening formed in the ceiling surface;
a hollow box disposed above the oven so as to cover the opening; a waveguide having one end connected to the hollow box;
A high-frequency oscillator connected to the other end of the waveguide, a circular substrate made of a low dielectric material and rotatably disposed within an opening in the oven ceiling in a substantially concentric state with the opening; 1. A high-frequency heating device comprising: a rotating disk formed of a metal plate fixed to a substrate so as to leave a cross-shaped slit for microwave excitation. 2 The diameter of the substrate of the rotating disk is 17 mm, which is the microwave wavelength λ.
2. The high-frequency heating device according to claim 1, wherein the dimensions are set to be approximately equal to an odd multiple of 2. 3. The utility model according to claim 1 or 2, wherein the rotating disk is such that the width of the slit on the substrate is set to be 11 times smaller than the wavelength λ of the microwave. High frequency heating device.