JPH012292A - High frequency heating device - 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 Field of Industrial Application The present invention relates to a high-frequency heating device that can reduce uneven heating of an object to be heated (hereinafter referred to as food) and achieve uniform heating with a simple configuration.

Conventional technology In high-frequency heating devices, in order to prevent food from being browned and to perform good and efficient cooking, it is necessary to take measures to enable uniform heating.

Generally, in the case of dielectric heating using high frequency, the amount of heat generated Q per unit volume and unit time inside the food is given by the following equation.

Q=to*f m 1E12*gr 5tanδ ・
...... (1) K: proportionality constant f: high frequency frequency E: electric field inside the food εr: real part of the dielectric constant of the food tan δ: dielectric constant of the food Parameter other than IE12 in equation (1) Since is a constant shaped by the food, it is necessary to make the electric field strength IEI inside the food as similar as possible in order to achieve uniform heating.

Conventionally, the basic means of averaging the electric field strength inside food are the turntable method, which rotates the food during heating, and the method using high-frequency waves ( The starrer method for spreading microwaves (hereinafter referred to as microwaves) has been widely put into practical use.

The idea of the turntable method is that by rotating the food during induction heating, even if the electric field strength distribution inside the food is uneven at a certain moment during rotation, the distribution changes from moment to moment due to rotational motion. The electric field strength at each point inside the food product is averaged by one rotation. On the other hand, the idea behind the STUN method is to reflect the microwaves irradiated into the heating chamber from the waveguide in various directions by rotating metallic blades, thereby converting the electromagnetic field inside the heating chamber into a diffused state into a strong standing wave. This method aims to achieve uniform heating of food by suppressing the occurrence of mode.

Problems to be Solved by the Invention However, the standing wave mode of microwaves generated inside the heating chamber, which causes non-uniform heating, strongly depends on the spatial shape of the heating chamber, and it is difficult to change the standing wave mode. is the wavelength of the microwave (spatial wavelength 12.2 in the case of a microwave oven)
This requires modification of the spatial shape with considerably larger dimensions than the conventional method. Therefore, in the stun method described above, in order to suppress the generation of standing waves, the typical dimensions of the blades (for example, diameter) must be several times the microwave wavelength in order to obtain a sufficient diffusion effect, and the heater For ranges equipped with etc., consider the space factor, etc.! Iη, it is difficult to arrange such a large-scale stun. In addition, with the turntable method, heating is made uniform by moving the food during dielectric heating, but because food is moved by rotation, the electric field energy absorbed by the food is averaged in the circumferential direction of the rotating shaft. However, since it is not uniform in the radial direction, it is likely that, for example, the peripheral area will be well heated but the central area will be half baked.

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to provide a high-frequency heating device that can uniformly heat food without significantly impairing the space factor and with a simple configuration.

Means for Solving the Problems In order to solve the above-mentioned problems, the high frequency heating device of the present invention has a structure in which a reflecting plate made of a shape memory alloy is attached to the wall surface constituting the heating chamber.

Function: In addition to the above-described configuration, the present invention has the configuration that, by appropriately setting the critical temperature for shape change of the shape memory alloy that is the material of the reflector, the air in the heating chamber is reduced by the steam etc. released from the food during food heating. As the temperature rises, the temperature of the reflector also increases, and when the critical temperature is reached, the shape of the reflector changes. By setting the area of the reflector to an appropriate size, the standing wave mode of the microwave will change significantly before and after reaching the critical temperature, that is, in the first and second half of cooking, and the electric field strength distribution inside the food will change. The temperature rise distribution will also change significantly. By averaging the distribution by superimposing different distributions in this way, it becomes possible to realize uniformity of the 7JIl heat of the food.

EXAMPLE Hereinafter, a high-frequency heating device according to an example of the present invention will be described with reference to the drawings.

FIG. 1 shows a high frequency heating device in one embodiment of the present invention.

In Fig. 1, 1 is a magnetron, 2 is a radiation antenna of magnetron 1, 3 is a waveguide that serves as a transmission path for microwaves radiated from antenna 2, 6 is a heating chamber, and 4 is a waveguide 3 and a heating chamber. 6 is a coupling hole for high-frequency coupling, 8 is a saucer for placing food, and 9 is a food dielectrically heated by microwaves. Reference numeral 10 denotes a reflector having a joint portion 11 made of a shape memory alloy containing niobium, molybdenum, or the like as an additive component. It is fixed to the side wall of the heating chamber 6 by a part of the lower part of the reflector 1°.

In the high-frequency heating device configured as described above, microwaves radiated from the radiation antenna 2 of the magnetron 1 are transmitted through the waveguide 3 and radiated into the heating chamber 6 through the coupling hole 4. The microwaves radiated into the heating chamber 6 are repeatedly reflected inside the heating chamber 6. Due to the steam and the like emitted from the food 9 heated by the microwave, the temperature inside the zero-mouth heat chamber 5 rises, and the temperature of the reflection plate 10 also rises. When the temperature of the reflector 1o reaches the critical temperature of the shape memory alloy used in the joint 11, the shape of the joint 11 changes. At the same time, the reflection plate 1o is tilted. As the shape inside the heating chamber 6 changes after reaching the critical temperature, the direction of microwave reflection changes.
The standing wave mode changes significantly. As a result, the electric field intensity distribution within the heating chamber 6, that is, within the food 9, changes between the first half and the second half of heating. By superimposing these two different distributions, distribution unevenness is averaged out, making it possible to achieve more uniform heating.

FIG. 2A shows a high frequency heating device according to a second embodiment of the present invention. Further, FIG. 2B shows the movement of the fixing jig 13. In Figure 2, magnetron 1,
The radiation antenna 2, waveguide 3, coupling hole 4, heating chamber 6, saucer 8, and food 9 are the same as those in the embodiment shown in FIG. 12 is a metal reflector, and 13 is a fixture for the reflector using a shape memory alloy, which is attached to the ceiling surface. Reference numeral 14 denotes an aperture on the ceiling surface, and the size is such that the reflector 12 and the fixing jig 13 are accommodated in the aperture 14 when the reflector 12 is parallel to the bottom surface. The shape memory alloy used in the fixture 13 has three critical temperatures. With such a configuration, the shape of the fixing jig 13 changes and the angle of inclination of the reflection plate 12 changes as the temperature inside the heating chamber 6 increases during heating. As a result, the standing wave mode within the heating chamber S, that is, the electric field intensity distribution within the food 9 changes over time. As a result, the inside of the food 9 is averaged by the overlapping of these, and the heating state becomes closer to uniformity.

In addition, although two types of shape memory alloys having different critical temperatures are used in FIG. 1, and three types are used in FIG. 2, more types may be used. Further, in FIG. 1, a part of the reflector 10 is made of a shape memory alloy, but a reflector 10 made only of a shape memory alloy may also be used. In that case, not only the bevel angle but also the shape of the reflector itself may be changed.

Further, in FIGS. 1 and 2, the reflectors 10 and 12 are attached only to the side surfaces and only to the ceiling surface, but they may be attached to both sides. Also, any combination of wall surfaces may be used.

Effects of the Invention The present invention uses a reflector made of a shape memory alloy or a fixing jig on the wall surface constituting the heating chamber, so that the reflector changes depending on the temperature in the heating chamber, that is, the heating time. This makes it possible to realize an excellent high-frequency heating device that can be averaged by changing the electric field strength distribution within the heating area, thereby achieving a more uniform heating state.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a cross-sectional view of a main part showing a high-frequency heating device according to an embodiment of the present invention, FIG. 2A is a cross-sectional view of a main part showing another embodiment of the present invention, FIG. B is an enlarged view of the main parts showing the movement of the fixing jig. 1... Magnetron, 2... Radiation antenna, 3... Waveguide, 4... Coupling hole,
6...Heating chamber, 8...Saucer, 9...
...Food, 10...Reflector, 11...
・Joint part, 12...Reflector, 13...
Fixing jig, 14... Squeezing.

Claims (2)

[Claims] (1) A high-frequency heating device comprising a heating chamber and a high-frequency oscillator, the heating chamber having a reflecting plate made of a shape memory alloy attached to a wall surface constituting the heating chamber. (2) The high-frequency heating device according to claim 1, wherein the shape memory alloy portion constituting the reflection plate is a fastening portion between the heating chamber and the reflection plate.