JPH03219587A - 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 the Invention The present invention relates to a high-frequency heating device for achieving automated defrosting of food products.

2. Description of the Related Art Conventionally, as an example of automating the thawing state of this type of high-frequency heating device (hereinafter referred to as a microwave oven), food 1 placed in a heating chamber 2 is heated as shown in FIG. Food 1 on a turntable 12 which is a uniform means for heating uniformly
The microcomputer 11, which is a control means, controls the drive means 10 to perform a defrosting and heating sequence corresponding to the detected weight, thereby controlling the output of the high-frequency radiation means 3.

That is, when the weight of a food 1 is detected by the weight sensor 21, the food is thawed by repeatedly turning on and off the driving means in accordance with the weight as shown in FIG. Note that 5 is a cooling fan that cools the high frequency radiation means.

Problems to be Solved by the Invention However, in the above configuration, when the starting temperature of the food is a certain predetermined temperature (for example, the freezer temperature -
18°C) and the shape is standard (for example, square).Depending on the thawing start temperature and shape of the food, the food may be boiled or unthawed, resulting in poor thawing results. It was enough. Furthermore, a weight sensor for measuring the weight of food detects changes in strain and changes in capacitance of a sensor material placed under a turntable, and has a very complicated structure.

Therefore, an object of the present invention is to realize thawing of food without failure with a simple configuration.

Means for Solving the Problems In order to achieve the above objects, the present invention uses an antenna installed in a heating chamber to detect the thawing state of food by determining the temperature dependence of the dielectric loss of the food and the oscillation frequency band of the high-frequency radiation means. This is indirectly understood from the relationship with the output of the detection means in . A converter for analog-to-digital conversion of the signal of the detection means and a control means integrate the signal of the detection means for each cycle of the uniform means for uniformly heating the food during oscillation of the high-frequency radiation means, and The configuration is such that the high frequency radiation means and the like are controlled based on the integrated signal change.

According to the present invention, the signal radio waves from the high-frequency radiating means are applied to frozen foods because if the food is below the freezing point due to an increase in dielectric loss due to heating of the frozen foods, the high-frequency radio waves are difficult to be absorbed by the food. The detection output is large, and when the moisture content increases beyond the freezing point, high frequencies begin to be absorbed in that area, so the detection output decreases.Since the signal of the detection means is integrated every cycle of the uniform means, , has the function of detecting the progress of defrosting of the entire food.

EXAMPLE Hereinafter, an example of the present invention will be described based on the accompanying drawings.

FIG. 1 is a block diagram of the main body of a high-frequency heating device according to an embodiment of the present invention.

1 is food, 2 is a heating chamber, 3 is a high frequency radiation means (hereinafter referred to as magnetron), 4 is a high voltage transformer for operating magnetron 3, 5 is a cooling fan for cooling magnetron 3, and 6 is an antenna for magnetron 3. It is shorter than x wavelength of the oscillation frequency (in the present invention, 3 to 5). 7
is an attenuator, 8 is a detection means, 9 is a converter for converting the detected signal from analog to digital, 10 is a drive means for varying the high frequency power of the magnetron 3, and 11 is for integrating the detected signal after conversion, It is a control means (microcomputer in the present invention) that controls the drive means 10 according to signal changes and adjusts the output of high frequency power.

12 is a turntable (one cycle is 10 seconds in the present invention) which is a uniform means for uniformly heating the food 1, and 13 is a motor that drives the turntable 12.

FIG. 2 is a circuit diagram of the detection means 8 for detecting the oscillation signal of the magnetron 3. 14 is a 50 ohm resistor, 15 is a detection diode (for example, Schottky barrier diode), 16.17 is a resistor, and 18 is a capacitor. These detect the high frequency power that is not absorbed by the food l in the oscillation frequency band of the magnetron 3, and the voltage Detected as Vs. Note that 7 is an attenuator, and the high frequency power that the magnetron 3 radiates into the heating chamber 2 is several hundred watts, and is used to prevent excessive input from entering the detection means 8.

FIG. 3 is a diagram in which the detection means 8 is composed of a microstrip line.

A copper foil pattern 20, 21 is etched onto a dielectric substrate 19 having a certain dielectric constant ER. The copper foil section 20 has a characteristic impedance of 50 ohms, and the section 21 is grounded. By configuring the detection means 8 on the microstrip line, it is easy to optimally design the length of the line according to the frequency band to be detected, and since this is done by etching, the detection accuracy is improved. .

Figure 4 shows food 1 (300 pieces of frozen medium minced meat) being heated in heating chamber 2.
FIG. 3 is a characteristic diagram showing changes in the signal voltage detected by the detection means 8 when the sample G) is placed at the center of the turntable 12 and decompressed.

In FIG. 4, the solid line of the detected voltage is the one that connects the detected voltage when the magnetron 3 oscillates during one period of the turntable 12, and the dotted line is the one that connects the detected voltage of one period of the turntable 12 with the analog-to-digital converter. FIG. 3 is a waveform diagram obtained by integrating a converted signal. Note that the integrated values are plotted at the same time. When the food temperature reaches around 12'C, the detection voltage Vs of the detection means 8 suddenly decreases, and the integrated voltage also decreases.

This is because when a part of the food 1 reaches near the freezing point, dielectric loss increases and high frequencies begin to be absorbed in that part, so the high frequencies detected by the detection means 8 relatively decrease. be.

FIG. 5 is a characteristic diagram showing changes in the signal voltage detected by the detection means 8 when the same food 1 (frozen minced meat 300G) is placed on the end of the turntable 12 and thawed.

Compared to FIG. 4, the detected voltage Vs during one period of the turntable 12 fluctuates greatly. This is because the distance between the food 1 and the antenna 6 is relatively large (changes) while the turntable is rotating.However, the integrated detection voltage is approximately the same when placed at the center and when placed at the edge. It turns out that they are the same.

Therefore, even when food 1 of the same weight is placed in the center,
It can be seen that even when placed at the edge of the turntable, stable weight detection is achieved by controlling the signal changes integrated during each cycle of the turntable.

That is, when the integrated signal change gradually decreases and there is no longer any uneven change, the control means 11 controls the magnetron 3, the drive means 10, and the turntable on and off to achieve automation of defrosting. It is something that exists.

Note that an inverter circuit may be used as the drive means 10 to control the output power of the magnetron 3, and the present invention is not limited to one embodiment.

Effects of the Invention As described above, according to the present invention, the following effects can be obtained.

The structure is such that the high frequency in the frequency band of the high frequency radiation means is detected by an antenna placed in the heating chamber, the voltage detected by the detection means is converted from analog to digital, and the control is performed using a signal integrated every period of the uniform means. A stable weight can be detected regardless of how the food is placed, the progress of defrosting the food can be easily detected according to the change in the signal, and automation of food defrosting can be achieved with a simple configuration.

[Brief explanation of drawings]

Fig. 1 is a block diagram of the main body of a high-frequency heating device according to an embodiment of the present invention, and Fig. 2 is a circuit diagram of the detection means of the same device, showing changes in the signal of the detection means 8 when placed at the center of the uniformity means. Characteristic diagram,
Figure 5 is a characteristic diagram similar to Figure 4 when placed at the end of the device.
FIG. 6 is a block diagram of the main body of a conventional high-frequency heating device, and FIG. 7 is a sequence control diagram for defrosting the same. 1... Food, 2... Heating chamber, 3...
... High frequency radiation means, 6 ... Antenna, 8.
...Detection means, 9...Analog-to-digital converter, 10...Driving means, 11...
- Control means, 12... Uniform means.

Claims (1)

[Claims] A heating chamber for putting food in and taking it out, a high-frequency radiation means for supplying high-frequency power into the heating chamber, a driving means for driving the high-frequency radiation means, a uniform means for uniformly heating the food, and an oscillation frequency of the high-frequency radiation means. an antenna shorter than 1/4 wavelength, a detection means for detecting the progress of defrosting of the food through the antenna, a converter for converting the signal of the detection means from analog to digital, and the high frequency radiation means,
control means for controlling the uniformity means; the control means integrates the signal of the detection means during each period of the uniformity means during oscillation of the high-frequency radiation means; A high-frequency heating device that controls a high-frequency radiation means, the driving means, and the uniforming means.