JP6838291B2 - Semiconductor type high frequency dielectric heating device - Google Patents

Description

The present invention relates to a semiconductor-type high-frequency dielectric heating device that heats an object to be heated arranged between opposing electrodes by high-frequency dielectric heating, and more particularly to a semiconductor-type high-frequency dielectric heating device that thawes frozen foodstuffs by high-frequency dielectric heating.

Conventionally, as a high-frequency dielectric heating device that heats an object to be heated by high-frequency dielectric heating, a high-frequency dielectric heating device that heats an object to be heated arranged between opposing electrodes by high-frequency dielectric heating is known. High-frequency dielectric heating is caused by applying a high-frequency voltage to the object to be heated (dielectric), changing the polarity of each molecule constituting the object to be heated at high frequency, and accompanying rotation, collision, vibration, friction, etc. of the molecule. It is a heating method that heats an object to be heated by internal heat generation.

The electrode impedance on which the object to be heated is arranged varies greatly depending on the shape, type, heating or thawing temperature of the object to be heated. At this time, when there is a difference between the output impedance of the high-frequency power supply and the electrode impedance on which the object to be heated is arranged, that is, when the impedance is not matched, reflected power is generated, the heating or thawing efficiency is lowered, and the circuit element is destroyed or deteriorated. May lead to.
In order to prevent this, a matching box is inserted between the high frequency power supply and the electrode, and impedance matching is maintained by providing a component, for example, a capacitor or a coil.

Conventionally, a high-frequency dielectric heating device for an object to be heated whose electrode impedance greatly changes depending on the shape, type, heating or thawing temperature of foodstuffs, etc. has a simple structure, a high heat-resistant temperature of a circuit element, and excellent resistance to reflected power. A vacuum tube type high frequency power supply is used. However, the vacuum tube type high frequency power supply has a high anode voltage due to the power amplification method, the device is large, the power supply efficiency is low, and the device cost is high because it is supplemented by the increase in output, and residual heat of the filament is required. There is a problem that it takes time to start up the device.

On the other hand, a semiconductor high-frequency power supply that amplifies power by controlling semiconductors at high speed is characterized by its small size and high efficiency as a system by combining it with a high-resolution automatic matching device, and has been conventionally used for applications such as plasma discharge. Has been done. As the circuit configuration of the automatic matching device used in the plasma discharge, the inverted L type shown in FIG. 1 (a) and the π type shown in FIG. 1 (b) can be considered.
FIG. 1A includes a first capacitor C1 connected in parallel with the high-frequency power supply 20, a second capacitor C2 connected in series with the electrode 30, and a coil L, and the first capacitor C1 and the second capacitor. Impedance matching is performed by making C2 variable in capacitance and sequentially changing its value in real time.
Here, assuming that the output impedance of the high-frequency power supply 20 and the combined impedance of the matching unit 40 are Z,
Z = R / (1 + ω 2 R 2 C 1 2) a + j {(ωL-1 / ωC 2) -ωR 2 C 1 / (1 + ω 2 R 2 C 1 2)},
The complex conjugate Z'is shown as the impedance matching range of the variable capacitance capacitors C1 and C2. At this time, the resistance R / (1 + ω ² R ² C ₁ ² ) of Z'does not become larger than the output impedance R of the power supply. Therefore, for example, the impedance for a load having a large resistance or impedance such as foodstuffs. Matching cannot be done properly.
Here, each symbol in the above equation is ω: angular frequency, R: output impedance of the power supply, L: reactance of the coil, C ₁ : capacitance of the first capacitor with variable capacitance, C ₂ : capacitance of the second capacitor with variable capacitance. Is.

FIG. 1B shows a first capacitor C1 connected in parallel with the high-frequency power supply 20, a third capacitor C3 connected in parallel with the electrode 30, and a series between the first capacitor C1 and the third capacitor C3. It is configured to include a connected coil L, to make the capacitance of the first capacitor C1 and the third capacitor C3 variable, and to perform impedance matching by changing the values in real time.
However, in the configuration in which the third capacitor C3 has a variable capacitance and its value is sequentially changed, the electrode impedance also changes sequentially accordingly. Therefore, in particular, the load between the electrodes 30 has a large capacity like foodstuffs, and moreover, When the electrode impedance changes significantly depending on the shape, type, heating or thawing temperature, the change is promoted, and it is difficult to continue stable impedance matching. Then, in order to maintain impedance matching in a state where the electrode impedance is not stable, it is necessary for the first capacitor C1 to have a large impedance adjustment width, which causes a problem that the matching device 40 is large and the cost is high.

As a high-frequency dielectric heating device that avoids the problem of increasing the size of the matching device, the matching circuit has a variable capacitor in parallel with the high-frequency power supply and a variable coil in series with the electrode, and the capacity of the capacitor can be increased by switching means. High frequency dielectric heating devices are known (see, for example, Patent Document 1).
In the high-frequency dielectric heating device described in Patent Document 1, the power reflected by the high-frequency power source is detected by the reflected power detecting means, and the values of the variable capacitor and the variable coil are appropriately combined based on the detection signal of the reflected power detecting means. Match the impedance and keep the reflected power to a minimum.

Japanese Unexamined Patent Publication No. 2005-56781

The high-frequency dielectric heating device described in Patent Document 1 is configured to adjust the impedance by changing the capacitance of a capacitor or a coil. , It is necessary to increase the impedance adjustment range by the coil and the capacitor, and it is not possible to reduce the size of the matching unit.

Therefore, the present invention solves these problems, and targets the heating or thawing of foodstuffs by a small and highly efficient semiconductor high-frequency power source, and the electrode impedance is changed depending on the shape, type, heating or thawing temperature of the foodstuffs. Even in a situation that is easily changed, it is possible to suppress the change and perform good impedance matching while simplifying and downsizing the matching device, and it is possible to heat or thaw with high quality at a small size and at low cost. An object of the present invention is to provide a semiconductor type high frequency dielectric heating device.

The present invention includes a semiconductor type high-frequency power source, a pair of electrodes disposed to face, Ri Do from the impedance matching device, a semiconductor type high frequency the placed frozen material between opposing said electrode thawing by high frequency dielectric heating In the dielectric heating device, the matching capacitor is between the first capacitor connected in parallel with the high frequency power supply, the third capacitor connected in parallel with the electrode, and the first capacitor and the third capacitor. A coil and a second capacitor connected in series with the capacitor, and a control unit are provided , and at least one of the first capacitor or the second capacitor is provided with a capacitance variable means, and the control unit is in the process of thawing the frozen foodstuff. In addition, the capacitance of the third capacitor is not variably adjusted, but is set to perform impedance matching by changing the capacitance of at least one of the first capacitor and the second capacitor, and the output of the high frequency power supply is set. With respect to the impedance and the impedance matching range formed by the matching capacitor, the resistance of the matching range includes a portion larger than the output impedance, and the reactor range is set so that the negative is larger than the positive. , The problem is solved.

In the invention according to claim 1, a small and highly efficient semiconductor high-frequency power supply and a third capacitor connected in parallel with the electrodes suppress changes in electrode impedance while stably heating or thawing foodstuffs. be able to.

In the invention according to claim 1 , the capacitance of the capacitor can be adjusted by the capacitance variable means provided in at least one of the first capacitor and the second capacitor, and for various foodstuffs having different shapes, types, and electrical characteristics. Impedance matching can be performed well.

In the invention according to claim 1 , at least the resistance of the impedance matching range formed by the matching device and the output impedance of the high-frequency power supply includes a portion larger than the output impedance, and the reactance range is larger than positive and negative. This is characteristic and can be easily realized by setting the third capacitor to a predetermined value.
In this way, by specializing the impedance matching range for thawing of foodstuffs, the matching box can be simplified and downsized. Further, by shortening the impedance matching time, it is possible to prevent damage or deterioration of the device from the reflected power and improve the reliability.
According to the second aspect of the present invention, accurate information on the impedance of foodstuffs can be easily obtained from the impedance information output unit of the matching device, and the parameters of the matching device narrowed down to the target object to be heated can be set. The matching device can be simplified based on the result.

A circuit diagram showing a reference example of a circuit configuration of an automatic matching device for plasma discharge. A circuit diagram showing a semiconductor type high frequency dielectric heating device according to an embodiment of the present invention. The table which shows the change of the capacity of the 2nd capacitor when the 3rd capacitor is not provided and when it is provided. The table which shows the change of the capacity of the 1st capacitor when the 3rd capacitor is not provided and when it is provided. An explanatory diagram showing an impedance matching range in the circuit configuration shown in FIG. An explanatory diagram showing an impedance matching range in the circuit configuration shown in FIG. The table which shows the result of having measured the change of the capacitance of the 1st capacitor and the 2nd capacitor. The table which shows the result of having measured the change of the capacitance of the 1st capacitor and the 2nd capacitor under the condition different from FIG.

Hereinafter, the semiconductor type high frequency dielectric heating device 10 according to the embodiment of the present invention will be described with reference to the drawings.

As shown in FIG. 2, the semiconductor high-frequency dielectric heating device 10 includes a semiconductor high-frequency power supply 20, a pair of electrodes 30, a matching device 40 connected between the electrodes 30 and the high-frequency power supply 20, and impedance matching. A coaxial cable (not shown) that connects the high-frequency power supply 20 and the matching box 40, a reflected power detection unit (not shown) that detects the power reflected by the high-frequency power supply 20, and a control unit (not shown) that controls each unit. The frozen foodstuffs arranged between the pair of electrodes 30 arranged to face each other are thawed by high-frequency dielectric heating. The high-frequency power supply 20 is configured to suppress or stop the high-frequency output by a protection function when the reflectance detected by the reflected power detection unit exceeds a predetermined threshold value.

As shown in FIG. 2, the matching unit 40 includes a first capacitor C1 connected in parallel with the high frequency power supply 20, a third capacitor C3 connected in parallel with the electrode 30, a first capacitor C1 and a third capacitor C3. A coil L and a second capacitor C2 connected in series between the two capacitors are provided, and a third capacitor C3 is connected in parallel with the electrode 30 inside the matching unit 40 to suppress a change in the electrode impedance. It has become.

At least one of the first capacitor C1 and the second capacitor C2 is provided with a capacitance variable means (not shown), and the capacitance can be adjusted so as to suppress the reflected power detected by the reflected power detection unit during thawing. The capacitance adjustment of the capacitor may be a continuous adjustment type by driving a variable capacitor in FIG. 2A or a multi-stage switching type by a relay in FIG. 2B. Further, although the third capacitor C3 does not variably adjust the capacitance during thawing, it may be provided with a simple capacitance variable mechanism in order to set the optimum value according to the load in advance.

In the circuit configuration of FIG. 2, assuming that the combined impedance including the output impedance of the high-frequency power supply 20 and the matching unit 40 is Z, the combined impedance Z is expressed by the following equation.
Z = 1 / [{(1 / R + jωC ₁ ) ^-1 + j (ωL-1 / ωC ₂ )} ^-1 + jωC ₃ ]
Each symbol in the above formula is ω: angular frequency, R: power supply output impedance (coaxial cable resistance), L: coil reactance, C ₁ : capacitance of the first capacitor with variable capacitance, C ₂ : variable capacitance. Capacity of the second capacitor, C ₃ : Capacity of the third capacitor.
Here, assuming that the complex conjugate of the combined impedance Z is Z', the range of Z'obtained by the capacitance variable width of the first capacitor C1 or the second capacitor C2 is the impedance matching range, which is ω, R, L, C. _It can be freely set according to the values of 1, C ₂ , and C _3.
Then, by setting the third capacitor C3 to a predetermined value, at least the resistance of the output impedance of the high frequency power supply 20 and the impedance matching range formed by the matching box 40 is larger than the output impedance (a portion larger than the output impedance). (Including), the range of reactance is larger than positive.

Based on the reflectance detected by the reflected power detection unit, the control unit switches the capacitance of at least one of the first capacitor C1 and the second capacitor C2 in the decreasing direction according to the thawed state of the object to be heated. It is designed for impedance matching. The control unit does not variably adjust the capacitance of the third capacitor C3 during thawing.

An experimental example of the present invention will be described below.

FIG. 3A shows the frequency of the high frequency power supply 20 = 13.56 MHz, the output impedance of the high frequency power supply 20 = 50 Ω, the capacitance C _{1 of the first capacitor C1 = 1500 pF, and the capacitance C 2} = 25 of the second capacitor C2 with variable capacitance. The value when the capacitance of the second capacitor C2 is adjusted so that the reflected power by the reflected power detector is always minimized by defrosting various foodstuffs with ~ 250 pF and the inductance L of the coil L = 1.8 μH ( Capacity%) is shown.
When the third capacitor C3 is not connected, the C2 volume% at the start of thawing differs depending on the type and number of foodstuffs, and the C2 volume% at the end of thawing changes significantly in the decreasing direction. That is, unless the capacitance variable width of the second capacitor C2 is increased, it is difficult to perform impedance matching, and the matching device 40 cannot be simplified or downsized.
In FIG. 3B, in addition to the above circuit configuration, a third capacitor C3 having a capacity of 400 pF is connected in parallel with the electrode 30 to thaw various foodstuffs so that the reflected power by the reflected power detector is always minimized. , The value (capacity%) when the capacitance of the second capacitor C2 is adjusted is shown. Various foodstuffs can be thawed without significantly changing the capacitance% of the second capacitor C2, and the matching device 40 having a reduced capacitance variable width of the second capacitor C2 can be simplified and downsized.

FIG. 4 shows the frequency of the high frequency power supply 20 = 13.56 MHz, the output impedance of the high frequency power supply 20 = 50 Ω, the capacitance C ₂ = 95 pF of the second capacitor C2, the inductance L of the coil L = 1.8 μH, and the first capacitor with variable capacitance. The capacity of C1 is C ₁ = 150 to 1500 pF, the capacity of the third capacitor C3 is C ₃ = 400 pF, various ingredients are thawed, and the capacity of the first capacitor C1 is always minimized by the reflected power detector. The value (capacity%) of C1 at the time of adjustment is shown. By connecting the third capacitor C3, the variable capacitance width of the first capacitor C1 can be set small, and the matching unit 40 can be simplified and downsized.

5, in the circuit configuration of FIG. 1 (a), the combined impedance of the high frequency power source 20 and the matching device 40 and Z, Z = R / (1 + ω 2 R 2 C 1 2) + j {(ωL-1 / ωC 2 The impedance matching range obtained by the complex conjugate Z'of) −ωR ² C ₁ / (1 + ω ² R ² C ₁ ^{2)} is shown.}
However, the angular frequency ω = 13.56 MHz, the output impedance R of the high frequency power supply 20, R = 50 Ω, the reactance L of the coil L = 1.8 μH, the capacitance of the first capacitor C1 with variable capacitance C ₁ = 150 to 1500 pF, and the variable capacitance first. 2 Capacitor C2 capacitance C ₂ = 25 to 250 pF.
The impedance matching range obtained by Z'is limited to a range smaller than the output impedance R = 50Ω (standardized impedance 1) of the high frequency power supply 20, and impedance matching is not possible for a resistance load larger than that.

_{FIG. 6 shows Z = 1 / [{(1 / R + jωC 1} ) ^-1 + j (ωL-1 /), where Z is the output impedance of the high-frequency power supply 20 and the combined impedance of the matching box 40 in the circuit configuration of FIG. The impedance matching range obtained by the complex conjugate _{Z'of ωC 2} )} ^-1 + jωC _{3}] is shown.}
However, the angular frequency ω = 13.56 MHz, the output impedance of the power supply R = 50 Ω, the reactance L of the coil L = 1.8 μH, the capacitance of the first capacitor C1 with variable capacitance C ₁ = 150 to 1500 pF, and the second capacitor with variable capacitance. The capacitance of C2 is C ₂ = 25 to 250 pF, and the capacitance of the third capacitor C3 is C ₃ = 50 pF, 200 pF, 400 pF, 600 pF.
By connecting the third capacitor C3 in parallel with the electrode 30 and increasing its value, the impedance matching range obtained by Z'in the example shown in FIG. 5 described above rotates counterclockwise, and the resistance of Z'is rotated. Expanded to a range larger than the output impedance R = 50Ω (normalized impedance 1) of the power supply. Range of reactance, capacitance _C 3 = 200 pF of the third capacitor C3, the negative is larger than the positive At _400pF, C 3 = negative In a positive 600pF is reduced. By connecting the third capacitor C3 in parallel with the electrode 30 in this way, a matching range specialized for thawing frozen foodstuffs can be obtained.

FIG. 7 shows the frequency of the high frequency power supply 20 = 13.56 MHz, the output impedance of the high frequency power supply 20 = 50 Ω, the inductance L of the coil L = 1.8 μH, the capacitance C ₁ = 150 to 1500 pF of the first capacitor C1 of the variable capacitor, and the second variable capacitor. Capacitor C2 capacity C ₂ = 25 to 250 pF, third capacitor C3 capacity C ₃ = 200 pF, 400 pF, 15 frozen Shine Muscats (thickness 28 mm) at -40 ° C are thawed at an output of 50 W and a thawing time of 15 minutes. done, as reflected power due to the reflected power detection unit is always minimized shows C _1, C ₂ values (% by volume) when sequentially automatically adjust the capacitance of the variable capacitor C1, C2 by the servo motor.
In the state where the third capacitor C3 is not connected, the values of the variable capacitors C1 and C2 greatly decrease and change with defrosting, but by connecting the third capacitor C3, the changes of the variable capacitors C1 and C2 are suppressed, and C The effect of suppressing changes in the variable capacitors C1 and C2 was greater when C _{3 = 400 pF than when 3 = 200 pF.}

FIG. 8 shows the frequency of the high frequency power supply 20 = 13.56 MHz, the output impedance of the high frequency power supply 20 = 50 Ω, the inductance L of the coil L = 1.8 μH, the capacitance C ₁ = 150 to 1500 pF of the first capacitor C1 of the variable capacitor, and the second variable capacitor. Capacitor C2 capacity C ₂ = 25 to 250 pF, third capacitor C3 capacity C ₃ = 200 pF, 400 pF, frozen mango (thickness 85 mm) at -40 ° C is thawed at an output of 200 W, thawing time is 15 minutes, and reflected. The values (capacity%) _{of C 1} and C ₂ when the capacitor capacities of the variable capacitors C1 and C2 are sequentially and automatically adjusted by the servo motor so that the reflected power by the power detection unit is always minimized are shown.
In a state where the third capacitor C3 is not connected, the value of the variable capacitor C1, C2 with the thawing is reduced greatly changed, the state of connecting the C 3 ₌ 200 pF, change of variable capacitors C1, C2 is inhibited There is. With C ₃ = 400 pF connected, automatic impedance matching could not be performed.

From the above, the semiconductor type high-frequency dielectric heating device 10 suppresses the change in the electrode impedance due to the thawing of foodstuffs by connecting the third capacitor C3 in parallel with the electrode 30 to the matching device 40, and simplifies the matching device 40. It was confirmed that impedance matching is possible while reducing the size.
At this time, the larger the value of the capacitor capacity of the third capacitor C3 is, the more effective it is in suppressing the change in the electrode impedance. Therefore, it is preferable to set the optimum value of C3.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various design changes can be made without departing from the present invention described in the claims. It is possible.

For example, in the above-described embodiment, the semiconductor-type high-frequency dielectric heating device has been described as thawing frozen foodstuffs by high-frequency dielectric heating, but the same effect can be obtained by thawing living organisms such as blood and animals and plants in addition to the foodstuffs. It is possible, and the use of the semiconductor type high-frequency dielectric heating device is not limited to thawing frozen foodstuffs as long as it heats the object to be heated.

Further, in addition to the above-described embodiment, an impedance information output unit that outputs impedance information of the matching unit (for example, the state of the first capacitor) to a monitoring monitor or the like may be provided. In this case, it becomes possible to easily obtain accurate information on the impedance of the foodstuff from the impedance information output unit of the matching device, and the parameters of the matching device narrowed down to the target object to be heated can be set, and matching is performed based on the result. The vessel can be simplified.

The semiconductor-type high-frequency dielectric heating device of the present invention is not only suitable for rapid thawing of frozen foods and the like, but also can be widely applied as an industrial dielectric heating device, and is a tabletop thawing device for home or business use (a tabletop thawing device for home or business use). It has high industrial potential, as it can be used by incorporating it into a microwave oven) or a refrigerator.

10 ・ ・ ・ Semiconductor type high frequency dielectric heating device 20 ・ ・ ・ High frequency power supply 30 ・ ・ ・ Electrode 40 ・ ・ ・ Matcher C1 ・ ・ ・ 1st capacitor C2 ・ ・ ・ 2nd capacitor C3 ・ ・ ・ 3rd capacitor L ・ ・・ ・ Coil

Claims (2)

A semiconductor type high-frequency power source, a pair of electrodes disposed to face, Ri Do from the impedance matching device, the placed frozen material between opposing the electrode in semiconductor type high-frequency dielectric heating apparatus for thawing by high frequency dielectric heating There,
The matching unit includes a first capacitor connected in parallel with the high-frequency power supply, a third capacitor connected in parallel with the electrode, and a coil connected in series between the first capacitor and the third capacitor. includes and a second capacitor, and a control unit,
At least one of the first capacitor and the second capacitor includes a capacitance variable means.
The control unit does not variably adjust the capacitance of the third capacitor during thawing of the frozen foodstuff, but changes the capacitance of at least one of the first capacitor and the second capacitor to perform impedance matching. Set to do,
Regarding the output impedance of the high-frequency power supply and the impedance matching range formed by the matching box, the resistance of the matching range includes a portion larger than the output impedance, and the reactance range is set to be larger than positive and negative. A semiconductor type high frequency dielectric heating device characterized in that it is used. The semiconductor-type high-frequency dielectric heating device according to claim 1 , further comprising an impedance information output unit that outputs impedance information of the matching device to the semiconductor-type high-frequency dielectric heating device.

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