JP2003045639A - High frequency thawing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve a desirable finished condition by detecting the end of thawing of the subject to be thawed. SOLUTION: This high frequency thawing apparatus has a matching circuit 100 having variable reactance elements 98 and 107 connected between an electrode plate 91 and a high frequency power supply 105. The high frequency power supply 105 is adapted to end its operation in response to a change in the constant of the variable reactance elements 98 and 107, thus making it possible to detect the end of thawing by use of a relatively simple arrangement.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency defrosting device used for household or business use and defrosting an object to be defrosted by using a high-frequency electric field.

[0002]

2. Description of the Related Art Heretofore, as a high-frequency decompressing device of this type, there has been one described in Japanese Patent Application Laid-Open No. 8-255682. FIG. 12 shows the conventional high-frequency decompression device described in the above publication.

In FIG. 12, a high voltage power supply 5 and a high frequency power supply 6 supply a high frequency high voltage between the upper electrode plate 2 and the lower electrode plate 3 in the heating chamber 1 to generate a high frequency electric field between both electrode plates. By doing so, the object to be thawed was dielectrically heated.

Further, as an impedance matching circuit,
The configuration of a series resonance circuit, which is shown in FIG. 12 as a conventional technique, in which a resonance capacitor 51 and a resonance variable coil 52 are connected in series, and a high frequency transformer 53 is provided on the resonance capacitor 51, is also used in the embodiment. However, the effect of reducing the loss of the resonance variable coil 52 has been described as the effect.

[0005]

However, although the high-frequency defrosting apparatus having the above-mentioned conventional structure is provided with the sensors for detecting the shape of the object to be defrosted, it does not indicate that the defrosting of the object to be defrosted is completed. A configuration that can detect properly is not stated, so it is difficult to obtain an appropriate finished state, and if it is thawed too much, boiling will occur and at the same time waste of power will occur, and conversely if thaw is insufficient There was a problem that a problem may occur in post-cooking.

As a method of detecting the temperature of the object to be defrosted,
For example, there is an infrared sensor, but it is expensive, and it is quite difficult to detect the temperature of the whole defrosted object.

[0007]

In order to solve the above-mentioned conventional problems, a high-frequency defrosting apparatus of the present invention comprises an electrode plate, a high-frequency power source for supplying high-frequency power to the electrode plate, the electrode plate and the high-frequency wave. A matching circuit having a variable reactance element connected between power supplies is provided, and the high-frequency power supply is configured to end its operation when the constant of the variable reactance element is changed.

With this, by properly detecting the defrosting completion state by an electrical method and automatically stopping the defrosting operation, the finished state is good and wasteful consumption of power can be prevented.

[0009]

The invention according to claim 1 has a high-frequency power supply for supplying high-frequency power to the electrode plate, and a matching circuit having a variable reactance element connected between the electrode plate and the high-frequency power supply. The high-frequency power supply is configured to end the operation in response to a change in the constant of the variable reactance element, so that the defrosting end state is appropriately detected, and the defrosting operation is automatically stopped, thereby improving the finished state. Therefore, it is possible to prevent wasteful consumption of electric power.

According to a second aspect of the present invention, in particular, the high-frequency defroster according to the first aspect is provided, wherein the matching circuit has a variable reactance element realized by a variable coil connected in series to the electrode plate, and the high-frequency power source is the above-mentioned. With the configuration that the operation is terminated after receiving a signal that the inductance value of the variable coil increases with time, the change in state at the point where the inductance value starts to decrease and then increases immediately before the end of thawing becomes the source of detection. Therefore, the decompression end can be detected with a relatively simple configuration.

According to a third aspect of the present invention, in particular, the high-frequency decompressor according to the first aspect is such that the matching circuit has a variable reactance element constituted by a variable capacitor connected in parallel to the output of the high-frequency power source. A high-frequency decompression device capable of detecting decompression completion with a very simple structure can be realized by adopting a configuration in which the operation is terminated when the capacitance value of the variable capacitor increases with time and reaches a predetermined value. It is a thing.

[0012] According to a fourth aspect of the present invention, in particular, the high frequency defrosting apparatus according to the third aspect is relatively simple in that the predetermined value is set to a value according to the variable capacitor value at the start of operation. However, even if the objects to be defrosted have different types and sizes, the defrosting completion can be detected more reliably.

According to a fifth aspect of the present invention, in particular, the high frequency defrosting device according to the third aspect is configured such that the predetermined value is set to a value corresponding to the minimum value of the variable capacitor from the start of operation. Even if conditions such as the type and size of the thawed product and the temperature of the thawed product at the start of the thawing are different, the thawing end can be detected with high accuracy.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 shows a block diagram of a high-frequency decompression device according to a first embodiment of the present invention.

In FIG. 1, two horizontally provided electrode plates 91 and 92 face each other to form an electrode 93, and an object to be thawed 94 such as frozen food is placed on the electrode plate 92. It is in the state of being

The high frequency power supply 105 outputs a high frequency power of 250 watts at 13.56 MHz, and the electrode plate 9
The high frequency power is supplied to the first and the second power supply units 92.

The matching circuit 100 has a variable reactance element 98 composed of a variable coil 97 connected in series to the upper electrode plate 91.

Further, in this embodiment, the variable reactance element 107 composed of the variable capacitor 106.
The variable capacitor 106 has a high frequency power source 10
5 outputs are connected in parallel.

Variable coil 97 and variable capacitor 106
Automatically performs impedance matching operation so that when the impedance of the electrode 93 changes due to various conditions, the impedance viewed from the high frequency power source 105 has a substantially constant absolute value and the reactance component becomes substantially zero. It is a thing.

The driving means 108 composed of a motor is configured to move the upper end of the variable coil 97 up and down, thereby changing the interval between the electrode plates 91 and 92,
Further, the inductance is changed by changing the winding pitch of the variable coil 97.

The variable coil 97 may have a variable inductance value in addition to the pinion rack mechanism, and may have a structure similar to that of a pantograph of a train. Other than the configuration in which the winding pitch is variable, for example, a magnetic core or a conductive core may be taken in and out, and a coil may be provided with a slider to change the length of the actual portion of the coil.

The variable capacitor 106 has a structure in which the facing area of the two electrode plates changes due to the rotational movement and the capacitance changes, and a variable capacitor generally used is used.

In the present embodiment, the variable capacitor 10
6 is rotationally driven by means (not shown) different from the drive means 108.

Braking means 10 constituted by using a solenoid
9 is provided to switch between braking and non-braking in response to a change in the distance between the electrode plates 91 and 92, and when the braking means 109 is in the non-braking state by the operation of the driving means 108, the electrode plates 91, The inductance of the variable coil 97 is changed when the interval of 92 is changed and the braking means 109 is in a braking state.

FIG. 2 shows a high frequency power source 1 of the same high frequency decompressor.
The circuit diagram of 05 is shown.

As shown in FIG. 2, the high frequency power source 105
Is an oscillation circuit 1 having a 13.56 MHz crystal oscillator
11, an inverter 112, and a filter circuit 113.

In this embodiment, the oscillator circuit 111 is
Further, it incorporates a microcomputer, detects the inductance value of the variable coil 97 that realizes the variable reactance element 98, processes the signal, and starts / stops the oscillation by an algorithm as shown in the flowchart described later. It is supposed to control.

The inverter 112 is a semiconductor element 114 composed of MOSFETs for performing a switching operation,
115, a DC power supply 116, a capacitor 117 that stabilizes the output of the DC power supply 116 against high frequencies, and a drive circuit 118 that controls ON / OFF by applying a voltage between the gates and sources of the semiconductor elements 114 and 115. .

The filter circuit 113 has an input connected to the connection point of the source terminal and the drain terminal which are the output terminals of the semiconductor elements 114 and 115. The coil 119 and the capacitor 120 are connected in series between the input terminal and the output terminal. A circuit is provided, and a capacitor 121 is connected between the output terminal and the common terminal (GND terminal) to reduce the harmonic distortion of the voltage applied to the input for output.

FIG. 3 shows the inverter 1 of the high frequency power supply 105.
12 is a circuit diagram of the drive circuit 118 used in FIG.

MOS driven by the output of the input terminal e
FET 202, choke coil 203 for resonance, capacitor 204, drive transformer 205, and capacitor 20 for impedance matching of drive transformer 205
6 and a trimmer capacitor 207 are provided.

The driving transformer 205 is carbonyl iron powder F.
The e (CO) 5 is wrapped with an insulating material, and is sintered at high pressure and high temperature to form a toroidal core.
It is constructed by winding 9, 210 and magnetically coupling them.

Further, particularly in this embodiment, the semiconductor element 1 having a large current capacity in terms of power as a high frequency decompressor.
In order to drive 14 and 115 with high efficiency, a structure called a trifilar winding, in which three enamel wires are wound around a core while closely contacting each other, is used, and one having a high coupling coefficient is used.

The DC power supply 211 has an output voltage of 24 V and a current capacity of 0.6 amperes.

The trimmer capacitor 207 absorbs the variations of the drive transformer 205 and other constituent elements, sets the gate-source voltage of the semiconductor elements 114 and 115 to a predetermined value, and can be driven with high efficiency in the manufacturing line. It is adjusted.

FIG. 4 shows the output voltage waveform of the drive circuit 118 in the state where the semiconductor elements 114 and 115 are connected and the defrosting operation is performed. FIG. 4A shows the position on the high potential side. 4A shows the waveform of the gate-source voltage Vg2 of the semiconductor element 115 located on the low potential side.

Since the windings 209 and 210 on the secondary side are connected with opposite polarities, (a) and (a) have voltage waveforms of opposite phases to each other, and the semiconductor elements 114 and 115.
Will be turned on alternately.

In addition, since the gate-source voltage is applied up to 12 V at maximum in any of the semiconductor devices, the drain-source voltage is almost 0 V, that is, the switch is almost conductive. Conduction is performed, and as a result, a high efficiency of 80 to 90%, which cannot be obtained with a class A amplifier using a vacuum tube, can be achieved, and a highly efficient high-frequency decompressor can be realized.

FIG. 5 is a waveform diagram for explaining the operation of the filter circuit 113.

FIG. 5A shows the input voltage waveform of the filter circuit 113, which is the drain voltage of the semiconductor element 115.
The inter-source voltage becomes Vds2. FIG. 5A shows the voltage waveform Vout of the output of the filter circuit 113.

In this embodiment, the semiconductor elements 114 and 115 are used.
, The Vds2 waveform is close to a square wave, and some ringing waveform is also superimposed, resulting in large harmonic distortion. However, due to the operation of the filter circuit 113, The harmonic component is removed, and a smooth voltage waveform that is almost a sine wave is output as Vout.

With the above-described structure, the high frequency thawing apparatus of this embodiment is applied with a high frequency voltage of several thousand volts between the electrode plates 91 and 92, and the inside of the object to be defrosted 94 is chilled and thawed by dielectric heating. Has been done.

In the high-frequency defroster, the impedance of the electrode 93 is capacitive, that is, it includes a considerably large negative reactance component, and therefore the high-frequency power source 105 is used.
In order to satisfactorily supply power from the coil, a coil having a positive reactance component is always required, but in the present embodiment, since the variable coil 97 is connected in series with the electrode 93, the variable coil 97 is positive. By having the reactance component of, the negative reactance component of the electrode 93 is almost canceled out.

Therefore, the variable coil 97 requires a smaller reactance value than the structure having the resonance capacitor 51 as in the prior art, and the number of turns, the diameter, etc. can be minimized, and the device size can be reduced. Will be effective in reducing costs and prices.

In order to make the high frequency power source 105 work efficiently, in the present embodiment, the variable coil 9 is always operated during the defrosting operation.
The inductance of the variable capacitor 106 is changed, and the electrostatic capacitance of the variable capacitor 106 is automatically changed.

Such impedance matching is necessary even when the function of detecting the end of defrosting is not provided, and detects the magnitude and phase difference of the voltage and current at the input of the matching circuit 100, and Accordingly, each variable reactance element is increased / decreased. For example, a configuration that has been used for a long time for a radio antenna can also be configured.

Therefore, for example, an infrared sensor capable of detecting the temperature of the object to be thawed 94 is not separately provided to detect the end of the thaw, but an infrared sensor is separately provided.
Since the end of the decompression can be known only by adding the program of the microcomputer described later, it is very advantageous in terms of cost.

FIG. 6 is a flow chart showing the algorithm of the microcomputer provided inside the oscillation circuit 111 of this embodiment.

When the power of the apparatus is turned on by the user after the object to be defrosted 94 is turned on, the processing from the start 700 is started, and first, the oscillation start 701 is performed to 13.5.
Output of 6 MHz is performed.

In M0 ← 9999 702, the maximum value 9999 that can be represented by this microcomputer is substituted into the memory M0 as an initial value.

Then, the inductance value of the variable coil 97 is read at the L1 value input 703.

More specifically, by reading the rotation angle of the driving means 108 with a potentiometer or encoder, or by counting the pulse number of the stepping motor in the microcomputer, the value corresponding to the value can be known. Is something that can be done.

In M1 ← L1 704, a value is assigned to the memory M1 and M1-M0> 0 705 is determined.

If the determination is No, M0 ← M1
After shifting to 706 and performing the processing, the L1 value input 7
It will return to 03.

FIG. 7A shows the inductance of the variable coil of the high-frequency defrosting apparatus of this embodiment, FIG. 7A shows the capacitance of the variable capacitor, and FIG. 7C shows the temperature change graph of the object to be defrosted. However, from the start of thawing to the point A, the L1 value decreases with time, so M1-M0> 070
The judgment of No. 5 is No, and it means that it turns around the loop.

When point A is exceeded, the inductance value of the variable coil receives a signal that increases with time, and the determination of M1-M0> 0705 becomes Yes.

Then, by the 60 second timer 707,
After waiting for 60 seconds, move to stop 708, where 1
The output of 3.56 MHz is stopped, and the operation of the high frequency power supply 105 is terminated.

In the present embodiment, the variable reactance element 98 is realized by the variable coil 97, and the product of the inductance value and ω is the reactance. Therefore, the high frequency power supply 105 has a constant of the variable reactance element 98. The operation is ended in response to the change of.

According to the experiments conducted by the inventors, the thawing is almost completed 60 seconds after the point A, and the temperature of the object to be thawed 94 begins to rise as shown in FIG. 7C. .

Therefore, by the operation as in this embodiment, the decompression operation can be ended at an appropriate time.

In this embodiment, the variable capacitor 106 is provided so as to be connected in parallel to the output of the high frequency power source 105, and the variable reactance element 107 is used. However, the variable reactance element 107 is not necessarily the variable capacitor 1.
It does not have to be 06, but may be composed of a variable coil.

In this case, the inductance value of the variable coil 97 is a value obtained by subtracting a constant value from the case of this embodiment, but the variation curve is almost the same as that in FIG. Therefore, the detection of the end of defrosting can be similarly performed.

(Embodiment 2) FIG. 8 is a flow chart showing an algorithm of a microcomputer provided inside the oscillator circuit 111 in the second embodiment.

Also in this embodiment, the parts other than the microcomputer have the same structure as that of the first embodiment.

The operation will be described below.

When the power of the apparatus is turned on by the user after the object to be defrosted 94 is turned on, the processing from the start 800 is started, and first the oscillation is started 801 to 13.5.
Output of 6 MHz is performed.

Variable capacitor 1 at C1 value input 802
A capacitance value of 06 is read.

As with the variable coil 97 of the first embodiment, this is also achieved by reading the rotation angle of the variable capacitor shaft with a potentiometer or encoder and counting the number of pulses of the stepping motor to be driven in the microcomputer. , It is possible to know the value according to the value.

A value is set in the memory M0 by M0 ← C1 + P803, which becomes the capacitance value at the end of the decompression.

At the C1 value input 804, the capacitance value of the variable capacitor 106 is read again, and C1-M0
> 0 If the determination at 805 is No, the process returns to the C1 value input 804.

FIG. 9A shows the inductance of the variable coil of the high-frequency decompression device of this embodiment, FIG. 9A shows the capacitance of the variable capacitor, and FIG. 9C shows the temperature change graph of the object to be defrosted. Is.

Therefore, until the value of the capacitance of the variable capacitor 106 increases and reaches the predetermined value, it turns around this loop.

When the value of the capacitance of the variable capacitor 106 increases and exceeds the value of the memory M0, the oscillation stop 806 stops the operation of the high frequency power supply 105, and the end 8
Move to 08.

The equivalent series resistance (real number of impedance) of the electrode 93 varies depending on the size and material of the object to be defrosted 94, but in the present embodiment, the capacitance value of the variable capacitor 106 at the start of defrosting. By reading B and setting a value obtained by adding P to it, that is, a value corresponding to B is set as a predetermined value, it is possible to considerably suppress the change in the finished state due to each of the above-mentioned fluctuation factors. The decompression operation can be appropriately terminated with a simple configuration.

In FIG. 9, since the capacitance value B of the variable capacitor 106 at the start of defrosting is lower than the value at the end of defrosting, the operation shown in the flowchart of FIG. Depending on the shapes and types of 91, 92, the ratio of the equivalent series resistance of the electrode 93 to the input impedance of the matching circuit 100, the temperature of the object to be defrosted 94 at the start of thawing, the value at point B is the value at the end of thawing. It may be larger than the capacitance value, that is, P <0.

However, even in that case, a normal operation can be performed by adding a routine for determining whether or not the read capacitance value is increasing with time.

(Third Embodiment) FIG. 10 is a flow chart showing an algorithm of a microcomputer provided inside the oscillation circuit 111 in the third embodiment.

Also in this embodiment, the parts other than the microcomputer have the same structure as in the first embodiment.

The operation will be described below.

When the user turns on the power of the device after the object to be defrosted 94 is put in, the processing from the start 900 is started, and the oscillation starts 901 to 13.5.
Output of 6 MHz is performed.

In M0 ← 9999 902, the maximum value 9999 that can be expressed by this microcomputer is substituted into the memory M0 as an initial value.

Then, the capacitance value of the variable capacitor 106 is read at the C1 value input 903.

This is also exactly the same as the second embodiment, by reading the rotation angle of the variable condenser shaft and the like with a potentiometer or an encoder, and counting the number of pulses of the stepping motor to be driven in the microcomputer,
It is possible to know the value according to the value.

In M1 ← C1 904, a value is assigned to the memory M1, and it is determined that M1-M0> 0 905.

If the determination is No, M0 ← M1
After shifting to 906 and performing the processing, C1 value input 9
It will return to 03.

FIG. 11A shows the inductance of the variable coil of the high-frequency defrosting apparatus of this embodiment, FIG. 7A shows the capacitance of the variable capacitor, and FIG. 7C shows the time change graph of the temperature of the defrosted object. However, from the start of thawing to point C, the C1 value decreases with time, so M1-M0> 09
The determination of 05 is No, which means that it will turn around the loop.

When the point C is exceeded, the variable capacitor 10
The capacitance value of 6 receives a signal that increases with time, and the determination of M1-M0> 0 905 is Yes.
s.

At this time, M0 becomes the capacitance value at the point C, so the value is set in the memory M0 by M0 ← M0 + Q907, which is the capacitance value at the end of decompression.

At the C1 value input 908, the capacitance value of the variable capacitor 106 is read again, and C1-M0
If the result of determination> 0 909 is No, the process returns to the C1 value input 908.

Therefore, until the value of the capacitance of the variable capacitor 106 increases and reaches the predetermined value, it turns around this loop.

When the value of the capacitance of the variable capacitor 106 increases and exceeds the value of the memory M0, the oscillation stop 910 stops the operation of the high frequency power supply 105, and then the end 9
Go to 11.

Although the equivalent series resistance (corresponding to the real number of impedance) of the electrode 93 varies depending on the size and material of the object to be defrosted 94 and the temperature, in the present embodiment, the capacitance of the variable capacitor 106 starts defrosting. The capacitance value C of the variable capacitor 106 at the minimum point is read from the above, and a value obtained by adding the value Q to it, that is, a value corresponding to C is set as a predetermined value, so that The change can be considerably suppressed, and the present embodiment can more appropriately terminate the thawing operation even if the temperature at the start of thawing is different.

In the second and third embodiments, P
Although the values Q and Q are added to obtain a predetermined value, it is possible to use multiplication or division instead of addition.

[0095]

As described above, according to the present invention, it is possible to detect the end of the defrosting of the object to be defrosted and to finish the defrosting operation with a relatively simple structure, and to realize a device with excellent defrosting performance. can do.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a high-frequency decompression device according to a first embodiment.

FIG. 2 is a circuit diagram of a high frequency power supply 105 of the high frequency decompressor.

FIG. 3 is a circuit diagram of a drive circuit 118 of the high frequency decompressor.

FIG. 4 is an operation waveform diagram of the drive circuit 118 of the high-frequency decompression device.

FIG. 5 is an operation waveform diagram of the filter circuit 113 of the high frequency decompressor of the same.

FIG. 6 is a flowchart of an oscillator circuit in the high frequency power supply 105 of the high frequency decompressor.

FIG. 7 is a diagram showing the time change of the inductance of the variable coil of the high-frequency defroster, the capacitance of the variable capacitor, and the temperature of the object to be defrosted.

FIG. 8 is a flowchart of an oscillator circuit in a high frequency power supply 105 of a high frequency decompressor according to a second embodiment.

FIG. 9 is a diagram showing a time change of the inductance of the variable coil of the high-frequency defroster, the capacitance of the variable capacitor, and the temperature of the object to be defrosted.

FIG. 10 is a flowchart of an oscillator circuit in a high frequency power supply 105 of a high frequency decompressor according to a third embodiment.

FIG. 11 is a diagram showing a time change of the inductance of the variable coil of the high-frequency defroster, the capacitance of the variable capacitor, and the temperature of the object to be defrosted.

FIG. 12 is a block diagram of a high-frequency decompression device according to a conventional technique.

FIG. 13 is the same impedance matching circuit diagram of the high-frequency defroster.

[Explanation of symbols]

91, 92 Electrode plate 105 high frequency power supply 106, 107 variable reactance element 100 matching circuit 106 variable coil 107 Variable capacitor

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Katsunori Zaizen             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Yoji Uitani             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. F term (reference) 3K086 AA01 AA10 BA09 DA02 DA07                       FA05 FA10                 3K090 AA01 AB03 BA05 BB01 EB12                 4B022 LQ07 LT07

Claims (5)

[Claims] 1. An electrode plate, a high frequency power source for supplying high frequency power to the electrode plate, and a matching circuit having a variable reactance element connected between the electrode plate and the high frequency power source, wherein the high frequency power source is the A high-frequency decompression device that terminates its operation when the constant of the variable reactance element changes. 2. The matching circuit has a variable reactance element realized by a variable coil connected in series to an electrode plate,
The high frequency power supply device according to claim 1, wherein the high frequency power supply terminates its operation after receiving a signal in which the inductance value of the variable coil increases with time. 3. The matching circuit has a variable reactance element composed of a variable capacitor connected in parallel to the output of the high frequency power source, and in the high frequency power source, the capacitance value of the variable capacitor increases with time to a predetermined value. The high frequency defrosting apparatus according to claim 1, wherein the operation is terminated at times. 4. The high frequency decompressor according to claim 3, wherein the predetermined value is set according to the variable capacitor value at the start of operation. 5. The high frequency decompressor according to claim 3, wherein the predetermined value is set to a value corresponding to a minimum value of the variable capacitor from the start of operation.