JPH0541279A - High frequency heating device - Google Patents

Abstract

PURPOSE:To accurately control heating regardless of the weight of a food by observing change in high frequency electric power transmitted within a wave guide, and thereby catching the progress of the heating condition of the food. CONSTITUTION:The weight of a food 8 is measured by a weight detecting device 11, and a high frequency heating output optimum to the measured value is selected, so that heating is started. Change in reflection electric power is observed by a control device 7 through a directional coupler 6 wherein reflection electric power out of the incident and reflection directional components of high frequency electric power which are transmitted within a wave guide 5 combining a heating chamber 1 with a magnetron 3, is remarkably changed in particular as heating is progressed, and when specified change is found, heating is controlled to be suspended and so on. By this constitution, heating including the thawing process of a frozen food can easily be controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency heating device for controlling the heating operation by detecting the progress of heating of food, which is particularly effective for thawing frozen food. is there.

[0002]

2. Description of the Related Art A high frequency heating device for controlling the heating of food by measuring the surface temperature of the food by an infrared temperature sensor and by measuring the internal temperature of the food by a temperature probe is disclosed in, for example, Japanese Utility Model Publication No. 60-86807. As known.

[0003]

In the above-mentioned conventional apparatus, first, regarding the infrared temperature sensor,
There is a problem that the accuracy of temperature detection is deteriorated by the dirt of the sensor, and the position of food is greatly affected.

Looking at the thawing and heating of frozen foods, there is a problem that it is extremely difficult to inexpensively and highly accurately detect the temperature because the temperature range in which infrared radiation is originally low is extremely high. There is also a problem that a change in food quality cannot be accurately captured when the food temperature does not rise even after the heating time elapses, as in the case of passing through the eutectic region which is the thawing temperature zone.

Further, the temperature probe has a problem that it is difficult to detect the temperature itself because it cannot be inserted into hard food such as frozen food.

[0006]

The present invention has been made to solve the above-mentioned problems, and a directional coupler is attached to a waveguide for coupling a magnetron and a heating chamber to transmit the signal in the waveguide. By observing the incident reflection component of the high frequency power, the degree of heating of the food is judged based on the change in the detected value that changes with the progress of heating, and the heating operation is controlled when a predetermined change is observed. At that time, the optimum high-frequency heating output is selected according to the weight of the food so that uneven heating does not occur.

[0007]

Since the dielectric properties of food change due to the progress of heating, the detected value of the transmission power detected by the directional coupler also changes accordingly. When a predetermined change occurs in the change in the detected value, the control device controls the heating operation.

In this case, since the high frequency heating output is adjusted to an optimum value according to the weight detected by the weight detecting device, even in a situation where uneven heating is likely to occur, such as when thawing frozen food, Excellent thawing is performed without causing abnormal heating.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG. 1
Is a metal heating chamber for storing food, 2 is this heating chamber 1
It is a high-frequency power supply port that was opened on the ceiling wall of. 3 is a magnetron, 4 is a high frequency power supply device for driving the magnetron 3, and 5 is a waveguide for transmitting the high frequency power generated by the magnetron 3 to the high frequency power supply port 2 of the heating chamber 1. Reference numeral 6 denotes a directional coupler, which is mounted at a predetermined position on one wall of the waveguide so as to obtain a predetermined output signal level, and which collects the incident power component and the reflected power component of the high frequency power transmitted in the waveguide 5. It detects and outputs each detection signal. Reference numeral 7 denotes a control device, which observes the output signal of the directional coupler 6 that changes with the progress of heating, and outputs a signal for performing control such as stopping the heating operation when a predetermined change occurs. To do. This controller 7
May observe changes in both the incident power and the reflected power that are signals output from the directional coupler 6, but in view of the fact that the change with the progress of heating is particularly remarkable with respect to the reflected power, Only the reflected power is focused. Reference numeral 8 is a food to be heated such as frozen food, 9 is a saucer on which the food 8 is placed and which rotates as necessary, and 10 is a rotary drive device for rotationally driving the saucer. 11 A weight detection device which is attached to a part of the rotation drive device 10 and detects the weight of the food on the tray 9. In the one configured in this way,
When the device is activated, first, the control device 7 measures the weight of the food 8 on the tray 9 by the weight detection device 10, and controls the high frequency power supply device 4 so that the high frequency output is optimum for the measured weight. The magnetron 3 is operated, and the rotation driving device 10 is turned on to rotate the tray 9.

The high frequency power generated by the magnetron 3 is supplied into the heating chamber 1 through the waveguide 5 and heats the food 8 contained therein. At that time, a part of the incident power is reflected in the heating chamber and is transmitted as reflected power back through the waveguide 4. Then, the dielectric characteristics of the food 8 start to change with the progress of heating, and the reflected power also changes accordingly.

The controller 7 observes and stores a signal relating to the reflected power detected and output by the directional coupler 6 from the start of heating. In this case, the output signal of the directional coupler 6 fluctuates in response to the temperature rise of the food and changes in its properties, and also fluctuates depending on the position change of the food 8 accompanying the rotation of the tray 9. On the other hand, the control circuit 7 measures the reflected power component through the directional coupler 6 at a plurality of predetermined rotational angle positions in one rotation of the tray 9, calculates an average value, and stores it.

Then, as time passes, such as when it is observed that a predetermined change occurs in the stored value, that is, when it passes through the eutectic region near the thawing temperature of 0 ° C. High-frequency power supply when the temperature and properties of food are accurately detected, including frozen state, eutectic state, and ice-free state, etc. 4 outputs a signal to stop the operation of the magnetron 3 and controls the heating of the food.

As described above, since the food is heated by the high frequency power corresponding to its weight, it is possible to prevent only a part of the food from being excessively heated. In particular, when the frozen food is thawed and heated, the worst situation in which microwaves are concentrated on the water generated in a part of the food and further promotes uneven heating can be avoided.

[0014]

By the way, in the control using the directional coupler, the operating point of the magnetron moves because the impedance of the heating chamber changes as the food moves in the heating chamber due to the rotation of the saucer. However, there is a problem that the detection level of the incident / reflected component of the high frequency power measured by the directional coupler also fluctuates due to the influence. Especially when the weight of the food is less than the predetermined amount, the fluctuation of the detection level is so large that the measured data may not be available for control.

In the case of the above-described embodiment of the present invention, this problem may not be avoided. To solve this point, do not rotate the pan when the weight of the food is less than the specified value, do not change the impedance of the heating chamber due to the rotation of the food, and make the magnetron oscillate at a constant output. It is recommended that the directional coupler capture only changes in physical properties of food due to temperature rise.

In this case, the apparatus is started up, the weight of the food 8 is first detected by the weight detection device 11, and the operation of the rotary drive device 10 for rotationally driving the tray 9 is prohibited when the value does not reach a predetermined value. At the same time, the magnetron 3 is operated with a high-frequency heating output commensurate with the measured food weight, and the value detected by the directional coupler 6 is stored.

As described above, when it is observed that a predetermined change occurs in the stored value, that is, when the eutectic region near the thawing temperature of 0 ° C. is passed. , The food temperature does not rise despite the passage of time, including the frozen state, eutectic state and ice-free state. When observed, a signal is output to the high frequency power source 4 to stop the operation of the magnetron 3 and control the heating of the food.

In this case, since the tray 9 does not rotate, there may be a concern that heating unevenness may occur, but the fact that the food itself is small is actually effective, and conversely the heating unevenness occurs. The situation is unlikely to occur, and there is no problem.

As described above, according to the present invention, the directional coupler detects and controls the change in the transmission power in the waveguide that changes with the progress of heating, that is, the change in the power that changes due to the change in the dielectric property of food. Since the heating operation is controlled when the device observes a predetermined change according to the degree of heating, it is easy to control the heating with high precision including the thawing process of the frozen food.
At that time, the food is heated with a high-frequency output commensurate with its weight, so that optimum heating is realized without causing uneven heating.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part showing an embodiment of the present invention.

[Explanation of symbols]

 1 heating chamber 3 magnetron 4 high frequency power supply device 5 waveguide 6 directional coupler 7 control device 9 saucer 10 rotation drive device 11 weight detection device

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H05B 6/70 E 8815-3K

Claims (3)

[Claims] 1. A heating chamber (1), a tray (9) on which food (7) is placed in the heating chamber, a rotary drive device (10) for rotationally driving the tray, and a tray placed on the tray. A weight detection device (11) for detecting the weight of the food, a magnetron (3) for oscillating high frequency power, a high frequency power supply device (4) for driving the magnetron, and a conductor for coupling the heating chamber and the magnetron. A wave guide (5) and a directional coupler (6) that is attached to a predetermined position on one wall of the wave guide to detect the incident / reflecting direction component of high frequency power transmitted in the wave guide and output a detection signal. ) And a control device (7) for controlling the high frequency power supply device based on the output signal of the weight detection device and the output signal of the directional coupler. 2. The control device controls to turn off the drive of the rotary drive device when the weight of the food detected by the weight detection device is less than a predetermined value. High frequency heating device. 3. The control device controls the high frequency power supply device based on an output signal of a reflection direction component of the incident reflection direction component detected by the directional coupler. The high-frequency heating device described.