JP2852458B2 - High frequency heating equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a high-frequency heating device generally called a microwave oven.

(Prior Art) Conventionally, this kind of high-frequency heating apparatus will be described with reference to FIGS. 6 and 7. FIG. FIG. 6 is a configuration diagram of a conventional high-frequency heating device. The high-frequency heating device includes a heating chamber 2 for thawing or warming the food 1 and a turntable (a motor-driven motor 3 for uniformly heating the food 1). Receiving a lower end of a rotating shaft 3a of the electric motor 3 to which the turntable 4 is fixed, and a magnetron 6 which emits high frequency by operation of a high-voltage transformer 5 disposed above the side wall of the heating chamber 2; A weight sensor 7 for detecting the weight of the food 1 placed thereon, a microcomputer (hereinafter referred to as a microcomputer) 8 for controlling the thawing or warming operation in accordance with the detected weight, and according to the instructions of the microcomputer 8, It comprises a driving device 9 for controlling the output of the magnetron 6 and a cooling fan 10 for cooling.

The operation of the high-frequency heating apparatus thus configured will be described with reference to FIG. 7 (a) when the operation of warming from the solution is performed continuously, and with FIG. 7 (b) when the operation of warming from room temperature is performed.

First, the weight of the frozen food 1 is detected by the weight sensor 7,
As shown in FIG. 7 (a), the thawing and warming control was performed by repeatedly turning on and off the drive device 9 according to the weight.

In the case of the food 1 at room temperature, the heating time was controlled in accordance with the weight detected by the weight sensor 7, and the food 1 was heated once as shown in FIG. 7 (b).

(Problems to be Solved by the Invention) However, in the above configuration, the food 1 at normal temperature and frozen
In the control method that repeats on and off with the same high-frequency output as normal temperature warming, in the case of thawing warming, the finishing temperature is too low or the temperature difference between the center and the surroundings is large, resulting in poor finishing. There was a problem of becoming sufficient. As a countermeasure against this, if a heating sequence for thawing warming is provided as a separate automatic cooking key, there is a problem that it becomes expensive. Further, the weight sensor 7 that measures the weight of the food 1 detects a change in the capacity of the sensor material, and has a problem that it has a complicated structure and is expensive.

The present invention solves the above-described problem, and provides a high-frequency heating apparatus with high reliability in which thawing and normal-temperature heating are performed without failure with a simple configuration.

(Means for Solving the Problems) The present invention provides a heating chamber for taking in and out food, a high frequency radiating means for supplying high frequency to the heating chamber, a driving means for driving the high frequency radiating means, and a uniform heating of the food. A uniforming means, an antenna, a detecting means for detecting the progress of heating of food through the antenna, a converter for converting the signal of the detecting means from analog to digital, a high-frequency radiating means, a driving means and a uniforming means. The control means integrates the high-frequency signal voltage detected by the detection means and analog-to-digital converted by the converter during each period of the uniformity means, and is controlled during a certain period of time. Based on the difference between the maximum value and the minimum value of the integral value of the signal voltage in each cycle, heating control is performed according to the heating start temperature of the food.

(Operation) With the above configuration, if the food 1 is a frozen food and has a temperature below the freezing point, the dielectric loss is small, and therefore it is difficult to absorb high-frequency radio waves, so that the detection output is large. When the part increases, the water with a large dielectric loss begins to absorb high-frequency radio waves, so that the property that the detection output decreases can be used.From the magnitude of the change in the detection output,
It can detect whether it is frozen food or normal-temperature food.

Embodiment An embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a configuration diagram of a high-frequency heating device according to the present invention.

6, the present embodiment differs from the conventional example shown in FIG. 6 in that an antenna shorter than 1/4 wavelength of the high frequency oscillated by the magnetron 6 is provided inside the heating chamber 2 instead of eliminating the weight sensor 7. 11 and a detection device 13 connected to the antenna 11 via an attenuator 12 and further connected to a microcomputer 8 via an A / D converter 14 for converting a detected analog signal into a digital signal. Is a point. The other components are the same as those of the conventional example, and the same components are denoted by the same reference numerals and description thereof will be omitted.

The attenuator 12 includes a magnetron 6 and a heating chamber 2.
The high-frequency power radiated into the inside is designed to prevent an excessive input from being input to the detector 13 at several hundred watts.

FIG. 2 is a circuit diagram of a detector 13 for detecting the oscillation signal of the magnetron 6.

In the figure, a detection device 13 includes a detection diode 15 such as a Schottky barrier diode and a resistor between an input terminal 13a connected to the attenuator 12 and an output terminal 13b connected to the A / D converter 14. 16 in series, and input terminal 13a
And between the detection diode 15 and the ground through a 50 ohm resistor 17, and between the detection diode 15 and the output terminal 13b through a parallel resistor 18 and capacitor 19. In the oscillation frequency band of the magnetron 6, high-frequency power not absorbed by the food 1 is detected, and the voltage is detected.
Output as V _S.

Figure 3 is a plan view of a detection device 13 which is a micro-strip line, the detection device 13, after securing the foil to one surface of a dielectric substrate 20 having a dielectric constant E _R, the ground electrode on both sides by etching 21a and 21b, input terminal in the center
A wiring pattern to be 21c, an output terminal 21d and a connection line 21e is formed, and according to the wiring diagram of FIG.
A resistor 17, a resistor 18 and a capacitor 19 of 50 ohms are formed between the resistor 17, the resistor 16 and the ground electrodes 21a and 21b.

Thus, the detection device on the microstrip line
By configuring 13, it is easy to optimally design the length of the line in accordance with the frequency band to be detected, and since it is formed by etching, the detection accuracy is good.

The operation of the high-frequency heating device configured as described above will be described.

First, the food 1 is placed in the center of the turntable 4 in the heating chamber 2.
Then, a frozen meat dumpling weighing 300 grams is placed, and an input button (not shown) is operated to start heating. The microcomputer 8 instructs the driving device 9 to emit high-frequency radio waves from the magnetron 6, and also instructs the electric motor 3 to turn the turntable 4.
Is rotated at a rotation speed of 6 times per minute.

The above high-frequency radio wave is absorbed by the frozen meat dumpling and proceeds to thaw, and the radio wave that is not absorbed is captured by the antenna 11, attenuated by the attenuator 12, passed through the detection device 13 and the A / D converter 14, and detected by the detection output V. _It is input to the microcomputer 8 as _S.
The microcomputer 8 performs integration for each cycle of the turntable 4.

FIG. 4 is a characteristic diagram showing the change of the signal voltage detected by the detector 13 and the integrated value of the microcomputer 8 at this time. The solid line indicates the detected voltage value when the magnetron 6 oscillates, and the broken line indicates the detected voltage. The integral value for each cycle of the turntable 4 is shown. When the temperature of the food 1 is in the vicinity of -2 ° C., rapidly decreased detection voltage V _S is, integrating the voltage also decreases. This is because, when a part of the food 1 is near the freezing point, the dielectric loss increases, and the high frequency begins to be absorbed in that part, and the high frequency captured by the antenna 11 relatively decreases.

 FIG. 5 is a characteristic diagram when the food 1 at normal temperature is warmed.

Compared to FIG. 4, the change in the integrated value of the detection voltage is small and the change in the dielectric loss is small, indicating that the heating is performed in the normal temperature range.

As described above, whether the food 1 is a frozen food or a normal-temperature food can be determined based on the difference between the maximum value and the minimum value of the integrated value as described above. Of the driving device 9 is controlled.

It goes without saying that an inverter circuit may be used for the driving device 9 for controlling the output power of the magnetron 6.

(Effects of the Invention) As described above, according to the present invention, a high frequency in a frequency band radiated by a magnetron is captured by an antenna, a detection voltage is converted into a digital value, and an integral value for each cycle of a turntable is obtained. Therefore, whether the food is thawed or warmed at normal temperature is detected from the progress of heating of the food, and heating is performed in accordance with each of them, and a simple high-frequency heating device having a structure that can always obtain a good finish can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram of a high-frequency heating device according to the present invention, FIGS. 2 and 3 are circuit diagrams of a detection device and a plan view of the circuit on a microstrip line, and FIGS. FIG. 6 is a characteristic diagram showing the progress of the detection voltage and the integrated value for each cycle of the turntable when the food and the room temperature food are warmed, FIG.
FIGS. 7 (a) and 7 (b) are sequence control diagrams for thawing warming and normal temperature warming. 1 ... food, 2 ... heating room, 3 ... electric motor, 3a ... rotating shaft, 4 ... turntable, 5 ... high voltage transformer, 6 ...
... magnetron, 7 ... weight sensor, 8 ... microcomputer (microcomputer), 9 ... driving device, 10 ... cooling fan, 11 ... antenna, 12 ... attenuator, 13 ... detecting device, 13a, 21c …… Input terminals, 13b, 21d …… Output terminals, 14…
… A / D converter, 15… Detector diode, 16,18 …… Resistance,
17 ... 50 ohm resistor, 19 ... capacitor, 20 ... dielectric substrate, 21a, 21b ... ground electrode, 21e ... connection line.

──────────────────────────────────────────────────の Continued on the front page (72) Inventor Masato Kajita 1006 Kazuma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (72) Koji Yoshino 1006 Kazama Kadoma Kadoma, Osaka Pref. Matsushita Electric Industrial In-company (72) Inventor: Shinichi Sakai 1006 Kazuma Kadoma, Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (56) References JP-A-59-207595 (JP, A) JP-A-3-219586 (JP, A JP-A-3-219587 (JP, A) JP-A-4-17293 (JP, A) JP-A-4-56092 (JP, A) JP-A-56-44494 (JP, U) JP-A-59-44 170393 (JP, U) (58) Field surveyed (Int. Cl. ⁶ , DB name) F24C 7/02 310 F24C 7/02 340 H05B 6/68 320

Claims (1)

(57) [Claims] 1. A heating chamber for taking food in and out, a high frequency radiating means for supplying high frequency to the heating chamber, a driving means for driving the high frequency radiating means, a uniform means for uniformly heating the food, and an antenna. Detecting means for detecting the progress of heating of the food via the antenna; a converter for converting the signal of the detecting means from analog to digital; and control for controlling the high-frequency radiating means, the driving means, and the uniforming means. The control means integrates the high-frequency signal voltage detected by the detection means and analog-to-digital converted by the converter during each period of the uniforming means, and is controlled during a certain period of time. A heating control in accordance with a difference between a maximum value and a minimum value of the integrated value of the signal voltage in each cycle of the heating according to a heating start temperature of the food.