JP2003045640A - High frequency thawing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the size and cost of apparatus by varying the interval between electrode plates, and simplifying the arrangement of a drive means for a first variable coil. SOLUTION: The drive means 108 is integrated by varying the interval between the electrode plates 101 and 102, and varying the inductance of the first variable coil 106 as well.

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 Conventionally, as this kind of high-frequency defroster,
There is one as described in JP-A-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. 13 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, in the above-mentioned conventional high-frequency defroster, the upper electrode plate 2 is moved up and down according to the height of the object to be defrosted, and the variable operation of the resonance variable coil 52 is changed. Further, it is necessary to perform tap switching of the high frequency transformer 53, and a driving means using, for example, a motor, a gear, a cam or the like is required to drive each variable element, and the device becomes large in size and the cost becomes high. Had challenges.

[0006]

In order to solve the above-mentioned conventional problems, a high-frequency defrosting apparatus of the present invention comprises: an electrode plate facing each other;
The first variable coil is connected to one of the electrode plates, and a driving unit that changes at least the distance between the electrode plates or the inductance of the first variable coil is provided.

This makes it possible to reduce the required number of driving means, downsize the apparatus, and reduce the cost.

[0008]

The invention according to claim 1 is characterized in that the driving means changes at least one of the interval between the electrode plates or the inductance of the first variable coil, whereby the object to be defrosted is changed. The same drive means drives the adjustment of the spacing between the electrode plates according to the height and the adjustment of the variable coil for efficiently operating the high-frequency power supply in response to various load conditions, thus reducing the device size The cost can be reduced.

According to a second aspect of the present invention, in particular, the high-frequency defrosting device according to the first aspect is provided with a braking means for switching between braking and non-braking in response to a movement of changing the distance between the electrode plates, and the driving means comprises: By adopting a configuration in which the braking means changes the distance between the electrode plates in the non-braking state and the braking means changes the inductance of the first variable coil in the braking state,
Since the spacing of the electrode plates and the inductance of the variable coil can be adjusted independently, it is possible to reduce the number of driving means and also when the height of the non-heated object and the combination of electrical characteristics are different. , The decompression operation can be performed efficiently.

According to a third aspect of the present invention, particularly in the high-frequency decompressor according to any one of the first and second aspects, the driving means changes the winding pitch of the first variable coil, By adopting a configuration in which the inductance of the first variable coil is changed, the variable coil can be realized with a simple configuration, which is effective for downsizing the device.

According to a fourth aspect of the present invention, in particular, in the high frequency defrosting apparatus according to the third aspect, the first and second electrode plates are provided substantially horizontally and the longitudinal direction is substantially perpendicular to the electrode plates.
The variable coil has a variable coil and the driving means is configured to change the interval and the winding pitch of the electrode plates by the vertical movement, so that the variable coil can be realized with a simple structure, which is particularly effective for downsizing the device. Is.

According to a fifth aspect of the present invention, particularly in the high frequency defrosting apparatus according to the first aspect, the second variable coil has a second variable coil connected in parallel to the output of the high frequency power source, and the driving means has the second variable coil. Since the second variable coil is made of an inexpensive material, the impedance connected to the output of the high-frequency power source can be changed with respect to changes in the type, shape, temperature, etc. of the defrosted object. Is properly maintained, the high frequency power source is operated efficiently, and defrosting performance is obtained.

According to a sixth aspect of the present invention, particularly in the high-frequency decompression device according to the fifth aspect, the second variable coil is configured to have magnetic coupling with the first variable coil, whereby the first variable coil is formed. Since the coil and the second variable coil can operate as a step-up transformer, a high voltage can be applied to the electrode plate with a relatively simple structure, and high defrosting performance can be obtained. .

According to a seventh aspect of the present invention, in particular, in the high-frequency defrosting apparatus according to any one of the first to sixth aspects, the distance between the electrode plates when the object to be defrosted is placed between the electrode plates is Since the winding pitch of the first variable coil is smaller than that during the thawing operation, the volume occupied by the first variable coil becomes small when the object to be defrosted is placed. As a result, the volume of the device can be reduced, and the size can be reduced.

The invention described in claim 8 is, in particular, in the high frequency thawing apparatus according to claim 5 or 6, when the object to be defrosted is placed between the electrode plates, the distance between the electrode plates is set during the defrosting operation. The winding pitch of the first variable coil and the winding pitch of the second variable coil are small in comparison with each other, so that both the first variable coil and the second variable coil are arranged. The occupying volume becomes small when the object to be defrosted is placed, and as a result, the volume of the device becomes small, and the size can be reduced.

[0016]

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

(Embodiment 1) FIG. 1 is a sectional view of a high-frequency defroster according to a first embodiment of the present invention during a defrosting operation.

In FIG. 1, two horizontally provided electrode plates 101 and 102 face each other to form an electrode 103, and an object to be thawed 10 such as frozen food is placed on the electrode plate 102.
4 is in the state of being placed.

The high frequency power source 105 outputs a high frequency power of 250 watts at 13.56 MHz, and the electrode plate 10
The high frequency power is supplied to the first and second power supplies 102.

The first variable coil 106 connected to the upper electrode plate 101 is provided so that its longitudinal direction is perpendicular to the electrode plate 101.

The series circuit of the electrode 103 and the first variable coil 106 is connected to the output of the high frequency power source 105, and in this embodiment, the variable capacitor 107 is connected in parallel to the output of the high frequency power source 105. The variable coil 106 and the variable capacitor 107 of No. 1 are such that when the impedance of the electrode 103 changes under various conditions, the impedance seen from the high frequency power source 105 has a substantially constant absolute value and the reactance component becomes substantially zero. ,
The impedance matching operation is performed.

The drive means 108 composed of a motor is the first
The configuration is such that the upper end of the variable coil 106 is moved up and down, whereby the spacing between the electrode plates 101 and 102 is changed, and the winding pitch of the first variable coil 106 is changed, thereby changing the inductance. It is supposed to be.

The variable capacitor 107 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
7 is rotationally driven by means (not shown) different from the driving means 108.

Braking means 10 constituted by using a solenoid
9 is for the movement of changing the distance between the electrode plates 101 and 102,
It is provided to switch between braking and non-braking. When the braking means 109 is in the non-braking state, the distance between the electrode plates 101 and 102 is changed by the operation of the driving means 108, and when the braking means 109 is in the braking state. , The inductance of the first variable coil 106 is changed.

Furthermore, in this embodiment, when the object to be defrosted 104 is placed between the electrode plates 101 and 102, the electrode plate 10
The interval between 1 and 102 is larger than that when operating as a high-frequency decompressor, and at the same time the first variable coil 106 is
The winding pitch of is small.

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 supply 105
Is an oscillator circuit 111 having a crystal oscillator, and an inverter 1.
12 and the filter circuit 113.

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, in the high-frequency defrosting apparatus of this embodiment, a high-frequency voltage of several thousand volts is applied between the electrode plates 101 and 102, and the inside of the object to be defrosted 104 is chilled and thawed by dielectric heating. Has been done.

Hereinafter, the electrode plate 10 by the driving means 108
Variable operation of the interval of 1 and 102, and the first variable coil 10
The inductance variable operation of 6 will be described.

FIG. 6 shows a sectional view of the object to be defrosted 104 placed in the high-frequency defrosting apparatus of this embodiment.

The object to be thawed 104 such as frozen food is placed on the lower electrode plate 1 with the user opening the front door of the apparatus.
Judgment on 02.

At this time, in this embodiment, the driving means 108 rotates counterclockwise.

At this time, the braking means 109 is in a non-braking state, and the electrode plate 101 is in a state in which it can freely move up and down.

By the operation of the driving means 108, the pinion rack mechanism operates, the upper end of the first variable coil 106 is lifted up, and the electrode plate 101 is pulled up from the upper side through the first variable coil 106. To be

In this embodiment, the first variable coil 106
Is designed so that its length is contracted by elasticity when no force is applied.
As shown in, the distance between the upper and lower electrode plates 101, 102 is widened, and the object to be thawed is easily placed.

Further, in this embodiment, when the user takes out the object to be defrosted 104 after the thawing operation is completed, the upper electrode plate 101 is also raised to the same position as in FIG. It is possible to realize a device with excellent usability.

In addition, in the state shown in FIG. 6, since the length of the first variable coil 106 is short, the height of the device does not unnecessarily increase, and therefore the size of the device is reduced. It is very effective.

FIG. 7 shows a cross-sectional view when the electrode plate 101 of the high-frequency defroster is lowered.

At this time, the braking means 109 is also in the non-braking state, but the driving means 108 is rotationally driven in the clockwise direction and the upper end of the first variable coil 106 is lowered by the pinion rack mechanism. , The upper electrode plate 10
1 is lowered, and the distance between the electrode plates 101 and 102 is narrowed.

The driving means 108 is stopped when the upper electrode plate 101 is lowered until the distance between the electrode plates 101 and 102 becomes a value slightly larger than the height of the object to be defrosted 104.

FIG. 8 shows a sectional view of the high-frequency defroster in a state in which the electrode plate 101 has been completely lowered.

In FIG. 8, the solenoid of the braking means 109 operates to shift to the braking state.

In this braking state, the vertical movement of the upper electrode plate 101 is prohibited, and the distance between the electrode plates 101 and 102 is fixed.

FIG. 9 shows a cross-sectional view when increasing the winding pitch of the first variable coil 106 of the high-frequency defroster.

In FIG. 9, the driving means 108 is driven to rotate again in the counterclockwise direction, and the upper end of the first variable coil 106 is pulled up again by the pinion rack mechanism.

However, since the braking means 109 is in the braking state this time and the upper electrode plate 101 is in the fixed state, the length of the first variable coil 106 is increased by driving the driving means 108. Will be extended, and the winding pitch will increase.

The first variable coil 106 of this embodiment is an air core, and is made of an enameled wire having a diameter of 2 mm.
It is constructed by winding turns, and the outer diameter of the coil is 100 mm.

Due to the change in the winding pitch due to the change in the entire length of the mechanical coil as described above, the inductance value can be used within the range of the change rate of about 1: 2.

In the state shown in FIG. 6, the winding pitch is 2 mm, which is the highest in terms of inductance. However, the defrosting operation cannot be performed in terms of the withstand voltage, but the object 104 to be defrosted is taken in and out. Therefore, the structure is effective in that energization is not required and rather the distance between the electrode plates 101 and 102 can be increased by shortening the height direction.

In the high frequency defroster, the impedance of the electrode 103 is capacitive, that is, it includes a considerably large negative reactance component, and therefore the high frequency power source 10
In order to satisfactorily supply the electric power from the coil 5, a coil having a positive reactance component is required, but in the present embodiment, the first variable coil 106 is connected in series with the electrode 103. Since the variable coil 106 of No. 1 has a positive reactance component, an operation of substantially canceling out the negative reactance component of the electrode 103 is performed.

Therefore, the first variable coil 106 is provided with the first variable coil 106 more than the configuration having the resonance capacitor 51 as in the conventional technique.
The required reactance value will be small, the number of turns and diameter will be the minimum necessary, and it will be effective for downsizing and cost reduction of equipment.

In order to make the high frequency power source 105 work efficiently, in this embodiment, the inductance of the first variable coil 106 is changed and the electrostatic capacitance of the variable capacitor 107 is also changed.

The equivalent series resistance (real number of impedance) of the electrode 103 varies depending on the size, material, temperature, etc. of the object to be thawed 104. For example, for the purpose of thawing frozen food used for home use, The results measured by the inventors as the electrode 103 having a practical size are as follows.
The range was about 7 to 30 ohms.

For example, in the case where the high frequency power supply 105 is a general one that is compatible with a load of 50 ohms,
The first variable coil 106 is set to have that value as much as possible.
Then, the adjustment of the variable capacitor 107 is performed.

As described above, in the present embodiment, the operation of changing the distance between the electrode plates 101 and 102 by one driving means 106 and the variable inductance of the first variable coil 106 are
Both are done and integrated, resulting in a smaller device and lower cost.

Particularly in this embodiment, the electrode plates 101 and 102 are
Since the electrode plate 101 that is moved to change the distance between the two is on the upper side, the weight of the non-decompressed product 104 is not applied when the electrode plate 101 moves up and down, and the driving means 108 is relatively small and has low power consumption. Although the effect of being able to use is that, by inevitably moving the upper electrode plate 101 up and down,
This does not mean that the distance between the electrode plates 101 and 102 has to be changed, and the device can be realized by constructing a driving means having sufficient power to move up and down even when the weight of the object to be defrosted 104 is used as a load. Therefore, the effect of reducing the number of driving means can be similarly obtained.

(Embodiment 2) FIG. 10 is a sectional view of a high frequency defrosting device according to a second embodiment of the present invention during a defrosting operation.

In the present embodiment, the variable capacitor 107 used in the first embodiment is eliminated and the second variable coil 250 and the braking means 251 are provided instead, but other parts are It has the same configuration as the previous embodiment.

The second variable coil 250 is provided in series above the first variable coil 106 and has a short distance between the first variable coil 106 and the first variable coil 106. The coil 106 and the second variable coil 250 have a configuration having a considerable mutual inductance.

However, at the time of manufacture, the first variable coil 106 and the first variable coil 106 are manufactured by winding an enamel wire having a diameter of 2 mm for 15 turns, and then 10 from the bottom.
Tapping is performed at the turn, and the lower 10 turns serve as the first variable coil 106 and the upper 5 turns serve as the second variable coil 250.

The upper end of the second variable coil 250 is
The ground terminal is connected to the housing of the apparatus and the ground together with the ground terminal of the high frequency power supply 105 and the lower electrode plate 102.

Therefore, both ends of the second variable coil 250 are connected in parallel to the output of the high frequency power supply 105.

In this embodiment, the braking means 109,
In a state in which both 251 are in the braking state, the drive means 108 changes the total length and winding pitch of the second variable coil 250, and changes the inductance.

Further, the object to be defrosted 104 is connected to the electrode plates 101, 1
The electrode plate 1 is placed between the two parts and placed between the two parts.
The interval between 01 and 102 is larger than that during operation, and at the same time, the winding pitch of the first variable coil 106 and the winding pitch of the second variable coil 250 are both smaller than during operation. Has become.

The operation of the above configuration will be described.

In the initial state, the braking means 109, 2
All of 51 are in a non-braking state, and the electrode plate 101 is pulled up by rotating the driving means in the counterclockwise direction, as in FIG.

After the unheated material 104 is placed, the driving means 108 is rotated in the clockwise direction to lower the electrode plate 101, and the driving means 108 is temporarily stopped at the height corresponding to the object to be defrosted 104, and the braking means is provided. When 109 is brought into the braking state and the driving means 108 is further rotated counterclockwise, the series body of the first variable coil 106 and the second variable coil 250 is extended as a whole.

After that, in this embodiment, the braking means 251 is also in the braking state, and the winding pitch of the first variable coil is fixed at that time, and the driving of the driving means 251 thereafter causes the second variable coil to operate. The winding pitch of 250 can be adjusted.

By the above-described operation, the high frequency defrosting apparatus of this embodiment can drive the electrode plate 10 by one driving means 108.
Since the interval of 1 and 102 is variable, the inductance of the first variable coil 106 is variable, and the inductance of the second variable coil 250 is variable,
Generally, the number of driving means composed of expensive parts such as a stepping motor is minimized to reduce the cost.

Impedance matching to the value of the impedance of the electrode 103, that is, the value of the equivalent series resistance (ESR), as seen from the output of the high-frequency power source 105 (however, the reactance component is substantially zero) is matched. In order to obtain the above, a method of connecting a variable capacitor in parallel with the output of the high frequency power supply 105 as in the first embodiment and a second method in parallel with the output of the high frequency power supply 105 as in the second embodiment. Although there is a configuration for connecting the variable coil of No. 2, the latter configuration, in particular, can be manufactured at once because the enameled wire required as a material for the second variable coil 250 is equivalent to that of the first variable coil 106. In this respect, the first variable coil 106 is advantageous in cost, and the value of the inductance required for the first variable coil 106 is smaller than that of the former method. Effect also occurs that requires less number of turns of the Le 106.

As described above, the impedance matching can be performed by the two variable coils, in particular, that the electrode 103 which is a load in the high-frequency decompressor always has a capacitive impedance, that is, a negative reactance component. It consists of.

Further, since the first variable coil 106 and the second variable coil 250 are provided in a state where there is magnetic coupling between them, an action as a single-winding type step-up transformer (auto transformer) is added, and several kilovolts are added. Such a high voltage is generated between the electrode plates 101 and 102, which is extremely advantageous.

In addition, when the object to be defrosted 104 is placed and taken out, the first variable coil 106 and the second variable coil 250 are both in a state in which the winding pitch is small and the total length is extremely short. Therefore, the shape of the device can be minimized.

[0089]

As described above, according to the present invention, it is possible to reduce the distance between the electrode plates and to simplify the structure of the driving means for the first variable coil, thereby reducing the size and cost of the device. it can.

[Brief description of drawings]

FIG. 1 is a sectional view of a high-frequency defrosting device according to a first embodiment during a defrosting operation.

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 sectional view of the object to be defrosted 104 placed in the high-frequency defroster.

FIG. 7 is a cross-sectional view of the electrode plate 101 of the high-frequency defroster as it descends.

FIG. 8 is a sectional view of the high-frequency defroster in a state in which the lowering of the electrode plate 101 is completed.

FIG. 9 is the same as the first variable coil 106 of the high frequency decompressor.
Cross-sectional view when increasing the winding pitch

FIG. 10 is a sectional view of the high-frequency defrosting device according to the second embodiment during a defrosting operation.

FIG. 11 is a sectional view of the object to be defrosted 104 placed in the high-frequency defroster.

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]

101, 102 electrode plate 105 high frequency power supply 106 first variable coil 108 driving means 109,251 Braking means 250 Second variable coil

   ─────────────────────────────────────────────────── ─── 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 AA02 AA08 AA10 BA09                       CC20 CD30 DB03 FA04 FA09                 3K090 AA20 AB03 BA05                 3L086 AA20 DA19 DA30                 4B022 LB01 LQ07 LT07

Claims (8)

[Claims] 1. An opposing electrode plate, a high frequency power supply for supplying high frequency power to the electrode plate, a first variable coil connected to the electrode plate, at least a gap between the electrode plates or the first variable coil. A high-frequency defrosting device having a driving means for changing one of the inductance of a coil. 2. A braking means for switching between braking and non-braking in response to a movement of changing the distance between the electrode plates, wherein the driving means changes the distance between the electrode plates in a non-braking state of the braking means, and the braking means. The high frequency defrosting device according to claim 1, wherein the inductance changes the inductance of the first variable coil in a braking state. 3. The high frequency decompressor according to claim 1, wherein the driving unit changes the winding pitch of the first variable coil to change the inductance of the first variable coil. 4. An electrode plate having two electrode plates provided substantially horizontally and a first variable coil whose longitudinal direction is substantially perpendicular to the electrode plates, wherein the driving means moves the electrode plates at intervals and windings by vertical movement. The high frequency defrosting device according to claim 3, wherein the pitch is changed. 5. A second device connected in parallel to the output of the high frequency power supply.
2. The high frequency decompressing device according to claim 1, further comprising a variable coil according to claim 1, wherein the driving means changes the inductance of the second variable coil. 6. The high frequency decompressor according to claim 5, wherein the second variable coil has a magnetic coupling with the first variable coil. 7. The distance between the electrode plates when the object to be defrosted is placed between the electrode plates is larger than that during the defrosting operation, and the winding pitch of the first variable coil is small. Any one of 6
The high frequency defrosting device according to the item. 8. The distance between the electrode plates when the object to be defrosted is placed between the electrode plates is larger than that during the defrosting operation, and the winding pitch of the first variable coil and the winding of the second variable coil are set. The high frequency defrosting device according to claim 5, wherein the pitch is small.