JPS599894A - 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 a high-frequency heating device having a high-frequency heating source and a thawing detection device equipped with a receiving antenna for transmitting and receiving weak high-frequency radio waves of a frequency different from the high-frequency heating source. The present invention relates to a high frequency heating device having a novel processing means.

Conventional methods of defrosting frozen foods using this type of device include 9. For example, at home, there are 9 methods for defrosting frozen foods: natural thawing, running water thawing, and heating thawing.

There are methods such as thawing using high frequency energy using a microwave oven, and for industrial use, thawing is performed using high frequency energy of 2.45 GHz or several tens of MH2, but in either case,
Due to the difference in the amount of frozen food and the temperature of the rice, it is not possible to thaw the food properly, resulting in over- or under-thawing, resulting in the food being boiled, or conversely, under-heating, requiring re-thawing. Therefore, it was extremely troublesome to constantly monitor thawing.

As a recent improvement in usability.

A device has been developed that detects thawing by measuring the temperature of food using infrared rays in a microwave oven. This device is the first
As shown in the principle diagram in the figure, a food placing table 2 is placed inside a heating chamber 1 surrounded by metal, and a frozen food 5 is placed on this food placing table 2 above the heating chamber 1. 2.
45GH2 high frequency heating source 4. High frequency heating means constituted by a waveguide 5 is arranged. 6 is an excitation port for high frequency energy. Here, the door (not shown) is opened and the food 3 is placed in the heating chamber 1, and the high frequency energy oscillated by the high frequency heating source 4 is excited from the excitation port 6 through the waveguide 5 to heat the food 3 to high frequency. Foods that increase with heating 3
The infrared rays 7 emitted from the infrared rays 7 are led out of the heating chamber through the slits 8, the infrared rays 7 are detected by the infrared detector 9, and the detected signals are amplified, converted, and processed by the control device 10 to generate the high-frequency heating source 4. It controls the

This infrared detection method is capable of measuring the absolute temperature of a single food item, so it can measure the thawing temperature, that is, around 0° C. However, even if this method is actually used, there are various problems. The first is that even if it is possible to measure temperature, it is not always possible to properly detect the thawing temperature, and the end point of thawing cannot be determined with certainty due to the melting of the ice.The second is that 2.
Thirdly, because the amount of infrared signal is small, a complex electronic circuit configuration is required for signal processing such as separation and amplification of noise components. This means that there is little possibility that it could be applied to anything other than microwave ovens.

For this reason, as an even better decompression detection method.

We have devised a device that accurately captures changes in physical properties of frozen foods during thawing and achieves appropriate thawing. FIG. 2 is a perspective view of a high-frequency heating device that can detect thawing by applying this method. In the figure, 11 is a cabinet, 12 is a door, 13 is an exhaust port, and 14 is a thawing detection function and a thawing completion indicator light.

A control device includes a defrosting end notification pusher, etc., and 15 is a display section including the control device 14. In this high-frequency heating device, to detect thawing, 9 foods must be heated and 2 foods must be heated.
．． 45 GHz radio frequency energy and 2.45 GHz
radiates high-frequency energy at a different frequency to food,
A rapid change in the amount of radio wave absorption of frozen food as the temperature rises and the food reaches a thawed state, a phenomenon in which the radio wave absorption is at its maximum in the crystalline state at the end of thawing, and further temperature rises from ice crystals to room temperature or high temperature. Defrosting is detected by utilizing the phenomenon in which the radio wave absorption rate decreases when the radio wave absorption rate changes, and it is possible to accurately detect defrosting based on the change in the amount of radio wave absorption.

FIG. 3 is an explanatory diagram showing details of the high-frequency heating device shown in FIG. 2. Heating chamber 1 surrounded by a metal plate or metal mesh
A door (not shown) is attached to the door so that it can be opened and closed freely.
There is a food table 2 inside.

Frozen food 3 is thawed by high frequency heating source 4 .

16 is a generator of a weak high frequency signal different from the high frequency heating source, 17 is a signal transmitting antenna, and 18 is a receiving antenna. Reference numeral 19 denotes a rotary mounting table for rotating and heating the food 3, which is driven by a driving motor 20. It is rotated by a shaft 21 to uniformly heat the nine foods 3. 22 is a rotation detection plate that is fixed to the shaft 21 and rotates, and a rotation detection element 26 that detects the rotation every time the rotation detection plate 30 rotates. A synchronous detector 24 detects the detection signal of this detection element 23. A converter 25 compares the signal from the synchronization detector 24 with the signal from the receiving antenna and receives the signal only while the two-rotation detection signal is present. A control device 26 is provided which receives signals from the converter 25 to control heating, and the output is controlled by these devices. In this case, the received output voltage is measured once during one rotation of the 9-turn mounting table 19, or is outputted by averaging the total output voltage during one rotation, but in either case, the received output voltage is output using the curve shown in Figure 4. 27
Changes as shown in . i.e. -18 to -15°C
As the frozen food is heated, the radio wave absorption increases and the voltage change reaches the lowest point, tmin, which is between -3°C and -1°C, and this temperature is the temperature that is included in the frozen food. The water that is released changes from ice to a mixture of ice and water.

This indicates the temperature at which the temperature has changed to a so-called ice crystal state, and thawing can be detected by detecting the point at which t min has been reached and controlling the heating.

However, when actually decompressing with this method, the following problems arise. That is, in FIG. 5, 1. The 2,45 GH7 high-frequency radio waves excited by the circle, frequency heating source 4 have a powerful output of 500 to 600 W in the case of continuous oscillation in ordinary high-frequency heating equipment, and if heated too strongly like frozen foods, they will boil. Or.

2. If there is a risk of damage to the appearance, such as rupture.
After exciting the oscillation intermittently for 2, eg, 4 seconds.

A common method is to reduce the average excitation power in a unit time by half by changing the duty by pausing for 4 seconds, etc., and heating slowly. When the transmission antenna 17 oscillates a radio wave different from the high-frequency radio wave from the high-frequency heating source at the same timing, the former has a single oscillation output of several hundred W, while the latter has a small output of several tens of mW at most.

2.45 2 included in the oscillation high frequency energy of GH2
, various frequencies other than the 45GH2 fundamental frequency are superimposed on the oscillation frequency from the transmitting antenna 17.

This has the disadvantage that it is difficult for the receiver No. 4 of the receiving antenna 18 to separate it due to radio wave noise, which causes problems in detecting decompression.

The present invention has been made in view of the above-mentioned drawbacks.

The purpose is to obtain a high-frequency heating device having a thawing detection device that is not affected by radio waves from a high-frequency heating source. In order to achieve this purpose, the excitation radio waves from the high-frequency heating source and the radio waves from the transmitting antenna are excited in a temporally divided manner, and the thawing detection signal is transmitted and received and signal measurement is performed only while the excitation of the high-frequency heating source is stopped. It was designed so that it would end.

An embodiment of the present invention will be described below with reference to FIGS. 5 and 6. FIG. 5 is a block diagram of a high-frequency heating device with a thawing detection function with high thawing detection accuracy. In the figure, 28 is a sweep oscillation circuit, which has an output of several tens of meters in a household microwave oven.
Sweep oscillation of radio waves. 29 is an oscillation circuit. The signal of this oscillation circuit 29 has a band rejection filter that prevents the frequency of 2.45 GH2 from flowing into the signal.
er 30 and is transmitted from the transmitting antenna 17 supported by the transmitting antenna support 31 . Similarly, the reception signal 4 is received by the reception antenna 18 supported by the reception antenna support 32, and
r33. Detection circuit 34. The signal is sent to the microcomputer 36 via the amplifier circuit 35. Here, when the microcomputer 36 instructs the high-frequency heating source 4 to intermittently excite, the high-frequency heating source 4 intermittently excites high-frequency output as shown in the waveform 37 in FIG. 6 (to-tt- tz~
t3). During the excitation time indicated by t(, -tl, t2 to t3, the signal from the sweep oscillator 28 is in a rest state.Next, when the high frequency heating source 4 is stopped in intermittent excitation, the microcomputer 360
The sweep oscillator 28 is operated according to the command, and the transmitting antenna 1
7 sends a signal into the refrigerator, and reception number 4 is also received by the receiving antenna 18 and sent to the microcomputer 36.

That is, the signal radio waves are transmitted from time t1 to t2 in FIG. t3~t
Each time is measured over 4 hours. Therefore, by performing signal measurement during the period when the high-frequency heating source 4 is inactive, the influence of various radio noises generated by the high-frequency heating source 40 can be prevented.

Note that this pause time preferably lasts at least while the rotary mounting table 19 makes one rotation, and the food 3 on the rotary mounting table 19 is measured multiple times while the two-rotation detection element 23 detects, for example, one rotation. Then, the average value is calculated, and the average value is further differentiated, and a signal is sent to the high frequency heating source 4 to end the defrosting at the point where the receiving signal 4 no longer changes. .

As described above, according to the present invention, it is possible to prevent adverse radio wave effects on measurement signals from a high-frequency heating source and improve the thawing detection accuracy, so there is an advantage that food can be thawed without failure.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram showing a high-frequency heating device having a conventional thawing device, Fig. 2 is an external view of the same, Fig. 3 is an explanatory diagram for explaining the principle of the thawing state detection device, and Fig. 4 is a receiving device for the same. FIG. 5 is a block diagram and configuration diagram of a high-frequency heating device according to an embodiment of the present invention, and FIG. 6 is an explanatory diagram showing the timing of the oscillation output. 1...Heating chamber, 3...Frozen food. 4... High frequency heating source, 17... Transmission antenna. 1B...Receiving antenna, 19...Rotating mounting table. Figure 1 5 Figure 2 Figure 3 //. Figure 4

Claims (1)

[Claims] A high-frequency heating source that excites high-frequency radio waves in a refrigerator surrounded by metal, a transmitting antenna that excites weak high-frequency radio waves of a different frequency, and a receiving antenna that receives radio waves from the transmitting antenna. The high-frequency heating device is provided in the refrigerator and includes a thawing detection device that thaws the frozen food on the rotating table using the high-frequency heating source and detects the progress of the thawing and controls the heating. (4) The radio waves are intermittently excited, and the rotating mounting table (19) is rotated at least once during the pause time of the intermittent excitation. A high-frequency heating device characterized by measuring thawing detection signals at one or more points on a rotating mounting table (19) and controlling thawing by arithmetic processing of the measured values.