JPH0878151A - High frequency defroster - Google Patents

Abstract

(57) [Summary] [Object] To provide a high-frequency defrosting device capable of uniformly defrosting an object to be defrosted without prolonging the thawing time and requiring no special skill. [Structure] An upper electrode 2 and a lower electrode 3 composed of divided electrode plates 2a and 3a are provided in a heating chamber 1. Adjacent divided electrode plates 2a and 3a are connected by an elastic member 8. The upper electrode 2 can be moved up and down by the electrode driving unit 7, and the divided electrode plates 2a and 3a are brought into close contact with the surface of the object to be defrosted 4 by the expansion and contraction of the elastic member 8. A high-frequency electric field is applied between the electrodes 2 and 3 from the high-voltage power supply 5 and the high-frequency oscillator 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high frequency thawing device for thawing frozen food such as meat and fish by dielectric heating.

[0002]

2. Description of the Related Art Conventionally, thawing by dielectric heating at a high frequency of several MHz or more is generally known. The device has a structure as shown in FIG. The heating chamber 1 is provided with an upper electrode 32, a lower electrode 33, and a posting plate 34 on which the object to be defrosted 4 is placed, and a high-frequency electric field is applied between the electrodes 32 and 33 from the high-voltage power supply 5 and the high-frequency oscillator 6 so that the object to be defrosted 4 is dielectric Due to the loss, heat thawing is performed. Both electrodes 32, 3
Reference numeral 3 is a single metal plate, which is installed in parallel with each other. The upper electrode 32 can be moved up and down by the electrode driving unit 7, and depending on the size of the object to be thawed 4, the upper and lower electrodes 3 can be moved.
The interval of 2, 33 is adjusted so that high-frequency energy can be efficiently supplied to the object to be defrosted 4.

The contact surface of the object to be thawed 4 with the electrodes 32 and 33 is not generally a flat surface but has an uneven shape. For example, in the case of the object to be thawed 4 having the shape as shown in FIG. Although the object to be defrosted 4 and the upper electrode 32 are in contact with each other, an air gap is generated in the portion B. Generally, the smaller the air gap, the larger the electric field applied to the object to be thawed and the more easily it is heated. This will be described with reference to the schematic diagram of FIG. 8. When the object to be defrosted 4 is sandwiched between the two electrodes 32 and 33 and a voltage V is applied between the electrodes 32 and 33, the dielectric constant of the object to be defrosted 4 is ε _1. Assuming that the permittivity of the air in the air gap is ε ₀ , the electric field E ₁ applied to the part without the air gap and the electric field E ₂ applied to the part with the air gap are expressed as follows.

[Equation 1] From the above two formulas,

[Equation 2] Here, the permittivity ε _{0 of} air is very small (ε ₀ = 1),
Since the permittivity ε ₁ of the defrosted object is several times that of ε ₀ , ε ₁ / ε ₀ >>
1, and d ₂ / d ₁ <1, so that E ₂ <E ₁ . The energy given to the object to be thawed by the dielectric heating is the electric field 2
Since it is proportional to the power, the portion without the air gap is likely to be heated, and the portion with the air gap is less likely to be heated.

Thus, since the surface of the object to be thawed is uneven, it is difficult to thaw where there is an air gap, which causes uneven thawing, and conversely, where there is no air gap, overheating causes burning or boiling. There was a problem that Therefore, as shown in Japanese Patent Application Laid-Open No. 58-223288, the upper electrode is placed 10 to 20 mm from the object to be thawed.
The influence of the air gap due to the unevenness of the object to be thawed can be reduced by separating them from each other, or as shown in JP-A-59-105296, the electrodes can be protected by a thin film of liquid conductor such as saline. By doing so, a method has been proposed in which the electrode and the object to be thawed are brought into close contact with each other and a uniform input voltage is applied.

[0005]

However, even if the upper electrode is separated by about 10 to 20 mm from the object to be thawed to reduce the influence of the air gap due to the unevenness of the object to be thawed, the object to be covered is provided in order to provide the air gap as a whole. A long thawing time is inevitable because the absolute amount of energy given to the thawed product is small. A high-power oscillator is required to prevent the thawing time from increasing. Further, since the thawing time varies depending on the position of the upper electrode, there is a drawback that it takes skill to find an appropriate thawing time.

When the electrode is formed by protecting the electrode with a liquid conductor such as saline solution protected by a thin film, the thin film portion hangs down by its own weight when it comes into close contact with the irregularities on the surface of the object to be thawed. There is also a problem in terms of use and safety, because it is difficult for an object to enter between the electrodes and the thin film is highly likely to be broken depending on the shape of the object to be thawed.

The present invention solves the above-mentioned drawbacks of the prior art, and provides a high-frequency defrosting device capable of uniformly defrosting an object to be defrosted without prolonging the thawing time and requiring no special skill. To do.

[0008]

In order to achieve the above object, the present invention provides a high frequency oscillator for generating a high frequency high voltage,
In a high-frequency defrosting device including a pair of upper and lower electrodes installed in a heating chamber connected to the high-frequency oscillator, one or both of the electrodes is composed of a plurality of divided electrode plates, and each divided electrode plate is individually It is a high-frequency defrosting device characterized in that it is provided with a contact means for moving and contacting the object to be defrosted. The contact means has a structure in which adjacent divided electrode plates are joined and held by an elastic member, or an elastic member is brought into contact with one surface of the divided electrode plate, and the other surface is defrosted by the elastic force of the elastic member. There are some configurations that closely adhere to things.

Further, in addition to the contact means for individually moving each divided electrode plate up and down to bring it into close contact with the object to be thawed, a fixing means for arbitrarily fixing each divided electrode plate and all the divided electrode plates are fixed by the fixing means. It may be a high-frequency defrosting device provided with an elevating means that moves up and down evenly. In this device, after the divided electrode plates are brought into contact with the object to be thawed by the contact means, all supporting rods are fixed by the holding means, and all the divided electrode plates are moved up and down uniformly by the elevating means, whereby the thawed object is thawed. A constant space is provided between the object and the divided electrode plate.

Further, both electrodes are composed of a plurality of divided electrode plates, the insulating means for electrically separating the divided electrode plates from each other, and the detecting means for detecting the progress of the thawing for each divided electrode plate. And a control means for controlling the output from the high frequency oscillator according to the progress of the defrosting by the signal obtained from the detection means. . The control means has a switching unit for selectively applying the output from the high frequency oscillator to each divided electrode plate, and a high frequency oscillator connected to each divided electrode plate,
Some have an input variable unit that can change the output of the high-frequency oscillator according to the progress of defrosting.

[0011]

[Function] Since one or both of the upper and lower electrodes are composed of a plurality of divided electrode plates and the divided electrodes can be individually moved, the divided electrode plates adhere to each other according to the unevenness of the surface of the thawed material. . Since the electrode is not a single plate as in the prior art but a divided electrode having a small shape, the number of contact points increases and the air gap also decreases. Therefore, a substantially uniform electric field is applied to the portion where the object to be thawed and the electrode are in contact with each other. That is, by moving the split electrode plate according to the unevenness of the surface of the object to be thawed, the unevenness of thawing due to the unevenness of the surface of the object to be thawed is reduced, and the energy generated between the electrodes is efficiently given to the object to be thawed. The thawing time can be shortened. Further, by providing a gap with a certain distance from the object to be thawed, a more uniform electric field can be applied, and the thaw unevenness can be further reduced.

By detecting the progress of the defrosted object and controlling the output of the high-frequency oscillator to each divided electrode plate accordingly, heating can be performed according to the shape. Therefore, uniform thawing can be performed regardless of the unevenness of the surface of the thawing object.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing a first embodiment of a high-frequency decompression device according to the present invention. The heating chamber 1 is provided with an upper electrode 2, a lower electrode 3, and a support shaft 9 for holding the upper electrode 2 and a support plate 10 for holding the lower electrode. Give an electric field.
The upper electrode 2 can be moved up and down by the electrode driving unit 7, and the space between the upper and lower electrode plates 2 and 3 is adjusted according to the size of the object to be defrosted 4 to efficiently apply high-frequency energy to the object to be defrosted 4.
To be able to supply.

Now, as shown in FIG. 2, the upper and lower electrodes 2, 3 are composed of a plurality of divided electrode plates 2a, 3a. In order that the divided electrode plates 2a and 3a individually change their direction to some extent and adhere to the object to be thawed 4, adjacent divided electrode plates are coupled and held by an elastic member 8 such as a spring, and the upper and lower electrodes 2 are , 3 are configured. The divided electrode plates at the four corners of the upper electrode 2 are joined and held to the support shaft 9 by the elastic member 8. Support shaft 9 for holding the split electrode plate 2a constituting the upper electrode 2
Is joined to the drive shaft 12 connected to the electrode drive unit 7 and is movable in the vertical direction. The divided electrode plates 2a and 3a are connected to the high frequency oscillator 6 by wiring. When the elastic member 8 is conductive, if it is connected to any one of the divided electrode plates, the other divided electrode plates also have the same potential.
If the elastic member 8 does not have conductivity, each divided electrode plate may be connected by wiring.

Next, the operation of the high frequency decompressor will be described. The shape of the object to be defrosted 4 is, for example, as shown in FIG. Place the object to be thawed 4 between the electrodes 2 and 3,
The upper electrode 2 is lowered by the electrode driving unit 7 and pressed against the object to be defrosted 4. By expanding and contracting the elastic member 8 connecting the plurality of divided electrode plates 2a and 3a, the individual divided electrode plates 2a and 3a are
It is possible for a to adhere to the surface of the object 4 to be thawed.
Thus, the electrode-to-electrode potential applied to the object to be thawed between the electrode plates in contact with the upper surface and the lower surface of the object to be thawed becomes the same, and the thawing time can be shortened.

In the first embodiment, if there is unevenness in the center of the object to be thawed, the divided electrodes may not be able to adhere sufficiently. In the second embodiment shown below, it is possible to adhere even to the unevenness of the central portion. FIG. 3 is a schematic configuration diagram showing the second embodiment. Similar to the first embodiment, the divided electrode plates 2a and 3a forming the upper and lower electrodes 2 and 3 are joined to one end of the supporting rod 15, and the supporting rod 15 penetrates the supporting plates 10 and 11, and A stopper 16 is attached to the end. As a means for bringing the divided electrode plates 2a, 3a into close contact with the object to be defrosted 4, a spring 17 is wound around the support bar 15 between the divided electrode plates 2a, 3a and the support plates 10, 11. Upper electrode 2
A support plate 11 for holding is connected to a support shaft 9, and the support shaft 9 is connected to a drive shaft 12 connected to the electrode drive unit 7.

When the electrodes are pressed against the object to be thawed placed in the heating chamber during thawing, the divided electrode plates 2a and 3a are pressed against the surface of the object to be thawed 4 by the elastic force of the spring 17. Even if there is unevenness at the center of the object to be thawed 4, the expansion and contraction of the spring allows the individual electrode plates to be brought into close contact with each other according to the surface of the object to be thawed. Therefore, the upper surface and the lower surface of the object to be thawed can be more reliably brought into contact with each other, and the inter-electrode potential applied to the object to be thawed between the heating electrodes can be made uniform, so that the thaw time can be shortened.

FIG. 4 is a schematic configuration diagram showing a third embodiment. One end of the support rod 15 is attached to the plurality of divided electrode plates 2a forming the upper electrode 2. The support rod 15 is the support plate 11
A holding device that can be arbitrarily selected to be fixed or opened is attached to the support rod 15 on the support plate 11. The lower divided electrode plate 3a is placed on the lower support plate 10. In this holding device, a gear 20 that is rotationally driven by a motor is attached to a support rod 15 with a thread groove 19 cut.
It is a structure that bites. The gear 20 is movable in the lateral direction and can be arbitrarily engaged with or disengaged from the thread groove 19 of the support rod 15. Therefore, in this holding device, which will be described in detail below, the divided electrode plates 2a and 3a are connected to the object to be defrosted 4.
It also has a close contact function of contacting with, a fixing function of fixing the supporting rods 15, and an elevating function of fixing all the supporting rods and moving them up and down.

Next, the operation of this high frequency decompressor will be described. The object to be thawed 4 is placed between the electrodes 2 and 3, and the divided electrode plate 2a forming the upper electrode 2 is lowered by the holding device 18 until it comes into contact with the object to be thawed 4. This is, for example, gear 2
By separating 0 from the thread groove 19 of the support rod 15, the divided electrode plate 2a is allowed to fall freely and brought into contact with the object to be thawed 4. If the contact sensor is attached, the motor is rotated to lower the support bar 15 until the divided electrode plate comes into contact with the object to be defrosted 4 and the contact sensor reacts. Thaw target 4
After the divided electrode plates 2a and 3a come into contact with each other, all the gears 20 are engaged with the thread grooves 19 of the support rod, and all the motors are simultaneously driven in the ascending direction so that the divided electrode plates and the object to be defrosted are uniformly distributed. Make a gap.

On the surface of the object to be defrosted 4, the divided electrode plates 2a,
Since the distance between the split electrode plates 2a and 3a is different only when the split electrode plates 2a and 3a are in contact with each other, even if the voltage applied between the split electrode plates 2a and 3a is equal, Differences occur. In order to reduce the influence of this difference, a uniform and small gap is provided between the electrode and the object to be thawed.
In this way, the influence of the difference in electric field strength is reduced, and uniform thawing performance without uneven thawing or local overheating to cause burning or boiling is obtained.

FIG. 5 shows a block diagram of a fourth embodiment according to the present invention. Since the basic configuration of this embodiment is almost the same as that of the third embodiment shown in FIG. 4, the corresponding parts are designated by the same reference numerals and the description thereof will be omitted. Adjacent split electrode plates 2a, 3
The support plates 10 and 11 are made of an insulating material so that a can maintain the insulating property, and are arranged at intervals so that the divided electrode plates 2a and 3a never contact each other. Alternatively, the side surfaces of the divided electrode plates 2a and 3a are coated with an insulating material so that the adjacent divided electrode plates 2a and 3a may come into contact with each other. In order to measure the surface temperature of the object to be thawed between the divided electrode plates 2a and 3a, a non-contact temperature sensor such as infrared rays is arranged as a detection means (not shown). When the surface temperature exceeds a certain reference value by receiving a signal from it,
A switching circuit 22 that disconnects the output from the high-frequency oscillator is provided between the electrodes.

When the surface temperature of the object to be defrosted 4 exceeds the reference value set in advance, the switching circuit 22 is turned off so that the divided electrode plates 2a, 3 at that portion are turned off.
The output of the high frequency oscillator 6 for a is stopped. Thaw target 4
For the divided electrode plate whose surface temperature does not exceed the reference value, the switching circuit 22 is turned on and the output of the high frequency oscillator 6 is continuously added. In this way, while sensing the surface temperature of the object to be thawed sandwiched between the electrodes, the switching circuit is turned on and off accordingly to control the output of the high frequency oscillator.
Energy can be efficiently given to the object to be thawed.
Therefore, the thawing time can be shortened and uniform thawing performance can be obtained without causing thawing unevenness or locally overheating to cause burning or boiling.

FIG. 6 is a block diagram showing the fifth embodiment. The difference from the fourth embodiment is that a high frequency oscillator 23 is connected to the divided electrode plates 2a and 3a facing each other vertically, and a variable control circuit 24 that can vary the output of the high frequency oscillator 23 and each divided electrode plate. That is, the detection circuit 25 for detecting the dielectric loss per unit volume between 2a and 3a is provided. This high-frequency decompressor varies the output of the high-frequency oscillator 23 based on the dielectric loss per unit volume detected by the detection circuit so that the variable control circuit 24 keeps the electric field of the divided electrode plate constant.

It is generally known that the electric field strength between the divided electrode plates and the dielectric loss per unit volume of the object to be defrosted (there is no air gap) between the divided electrode plates have the following relationship. There is. P = (5/9) × 10 ⁻¹⁰ fE ² ε _r tanδ (1) where P is the dielectric loss per unit volume, f is the power supply frequency, ε _r is the dielectric constant of the defrosted object, and tan δ is the dielectric loss tangent, E represents the electric field between the electrodes. Therefore, if the dielectric loss per unit volume can be made equal, it can be said that the electric fields between the divided electrode plates are also made equal.

The object to be defrosted can be regarded as a parallel circuit of capacitance and resistance, and the dielectric loss can be obtained from the capacitance and resistance between the divided electrode plates. Therefore, the dielectric loss per unit volume is the dielectric loss divided by the volume between the divided electrode plates. First, the volume of the thawed material can be obtained from the distance between the divided electrode plates and the area of the divided electrode plates. In order to measure this distance, a potentiometer is attached to the electrode plate drive unit for measurement. The capacitance is obtained from the distance between the divided electrode plates, and the impedance is obtained from the voltage and current between the divided electrode plates. Therefore, the resistance component of the impedance can be calculated. In this way, the dielectric loss per unit volume is obtained from the dielectric loss and volume of the thawed material between the divided electrode plates.

The object to be defrosted 4 is placed between the divided electrode plates 2a and 3a, and the divided electrode plates 2a and 3a are brought into contact with the object to be defrosted 4. The output from the high frequency oscillator 6 is the divided electrode plates 2a and 3a.
Is applied to the detection circuit 25, as described above,
The dielectric loss per unit volume between the divided electrode plates 2a and 3a is detected between the divided electrode plates. The signal is sent to the variable control circuit 24, and the variable control circuit 23 increases or decreases the output from the high frequency oscillator 23 according to the degree so that the dielectric loss per unit volume becomes a preset value. Since the electric field strength of the object to be thawed sandwiched between the electrodes is equalized in this way, the object to be thawed can be uniformly thawed. As a result, the energy is efficiently applied to the object to be thawed, so that the thaw time can be shortened, and uniform thaw performance can be obtained without causing uneven thaw or local overheating to cause burning or boiling.

[0027]

According to the present invention, since each divided electrode plate is in close contact with the surface of the object to be thawed placed in the heating chamber, the potential difference between the upper and lower contact surfaces of the object to be thawed is the same. Therefore, the energy generated between the electrodes can be efficiently given to the object to be thawed, and the thaw time can be shortened. When a plurality of adjacent divided electrode plates are joined by an elastic member, expansion and contraction of the elastic member allows the individual divided electrode plates to be brought into close contact with each other according to the inclination of the surface of the object to be thawed. When the split electrode plate moves vertically due to the elastic force of the elastic member and adheres to the surface of the object to be thawed, the individual electrode plates will not be thawed even if the center of the object to be thawed is uneven. It can be closely attached to the surface of an object.

After the divided electrode plates come into contact with the object to be thawed by the support rod holding means and the elevating means, all the electrode plates are held and moved simultaneously, so that a uniform gap is provided between the object to be thawed and the divided electrode plates. Since it is formed, a more uniform electric field is applied to the object to be thawed, and uniform thawing performance without uneven thawing or local overheating to cause burning or boiling can be obtained.

When the control means controls the output of the high-frequency oscillator applied between the divided electrode plates in accordance with the degree of thawing of the thawed object detected by the detection means, the thawed object between the electrode plates is controlled. By adjusting the thawing progress, it is possible to efficiently use the energy generated between the electrodes and obtain uniform thawing performance without uneven thawing or local overheating to cause burning or boiling.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a first embodiment of a high-frequency decompression device according to the present invention.

FIG. 2 is a plan view showing electrodes of the high-frequency defroster.

FIG. 3 is a schematic configuration diagram showing a second embodiment of the high-frequency decompression device according to the present invention.

FIG. 4 is a schematic configuration diagram showing a third embodiment of the high-frequency decompression device according to the present invention.

FIG. 5 is a schematic configuration diagram showing a fourth embodiment of the high-frequency decompression device according to the present invention.

FIG. 6 is a schematic configuration diagram showing a fifth embodiment of the high-frequency decompression device according to the present invention.

FIG. 7 is a schematic configuration diagram showing a conventional technique.

FIG. 8 is a schematic diagram showing the relationship between a dielectric and an electric field during thawing.

[Explanation of symbols]

 2 upper electrode 2a divided electrode 3 lower electrode 3a divided electrode 4 decompressed object 6 high frequency oscillator 8 elastic member

Claims (7)

[Claims] 1. A high-frequency defrosting device comprising a high-frequency oscillator for generating a high-frequency high voltage and a pair of upper and lower electrodes connected to the high-frequency oscillator and installed in a heating chamber, wherein one or both of the electrodes are plural. 2. A high-frequency defrosting device, comprising: the divided electrode plates according to claim 1, each of the divided electrode plates individually moving so as to come into close contact with an object to be defrosted. 2. The high frequency defrosting device according to claim 1, further comprising a contact means configured to hold adjacent divided electrode plates together by an elastic member. 3. The high-frequency defrosting apparatus according to claim 1, further comprising a contact means for abutting an elastic member on one surface of the split electrode plate, and the other surface of the divided electrode plate being in close contact with the object to be defrosted by the elastic force of the elastic member. 4. A high-frequency defroster comprising a high-frequency oscillator for generating a high-frequency high voltage, and a pair of upper and lower electrodes connected to the high-frequency oscillator and installed in a heating chamber, wherein one or both of the electrodes are plural. Of the divided electrode plates, each of the divided electrode plates individually moving up and down to make close contact with the object to be defrosted, fixing means for arbitrarily fixing the individual divided electrode plates, and the fixing means. A high-frequency defrosting device, comprising: an elevating means for fixing a divided electrode plate and moving the same evenly up and down to provide a uniform space between the object to be defrosted and the divided electrode plate. 5. A high-frequency defroster comprising a high-frequency oscillator for generating a high-frequency high voltage, and a pair of upper and lower electrodes connected to the high-frequency oscillator and installed in a heating chamber, wherein both electrodes are composed of a plurality of divided electrode plates. Insulation means for making the divided electrode plates electrically independent of each other, detection means for detecting the defrosting progress of each divided electrode plate, and defrosting progress by a signal obtained from the sensing means. And a control means for controlling the output from the high-frequency oscillator according to the above. 6. The high-frequency defrosting device according to claim 5, further comprising a control unit having a switching unit for selectively applying the output from the high-frequency oscillator to each divided electrode plate. 7. The high frequency decompressor according to claim 5, further comprising a high frequency oscillator connected to each of the divided electrode plates, and a control means having an input variable section capable of varying the output of the high frequency oscillator according to the progress of the decompression. .