JP2017017004A - Semiconductor type high frequency induction heating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor type high frequency induction heating device which is small-sized, inexpensive and capable of performing high-quality heating or thawing by satisfactorily performing impedance matching while suppressing a change of electrode impedance.SOLUTION: A semiconductor type high frequency induction heating device 10 comprises a semiconductor type high frequency power source 20, a pair of electrodes 30 which are disposed oppositely, and an impedance matching box 40. In the semiconductor type high frequency induction heating device 10, the matching box 40 includes: a first capacitor C1 connected in parallel with the high frequency power source 20; a third capacitor C3 connected in parallel with the electrodes 30; and a coil L and a second capacitor C2 connected in series between the first capacitor C1 and the third capacitor C3.SELECTED DRAWING: Figure 1

Description

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

  Conventionally, as a high-frequency dielectric heating apparatus that heats an object to be heated by high-frequency dielectric heating, a high-frequency dielectric heating apparatus that heats an object to be heated disposed between opposing electrodes by high-frequency dielectric heating is known. High-frequency dielectric heating is caused by applying high-frequency voltage to the object to be heated (dielectric material), 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 for heating an object to be heated by internal heat generation.

The electrode impedance of the object to be heated 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 of the object to be heated, that is, 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 device is inserted between the high-frequency power source and the electrode, and impedance matching is maintained by providing, for example, a capacitor or a coil as its constituent elements.

  Conventional high-frequency dielectric heating devices for heated objects whose electrode impedance changes greatly depending on the shape, type, heating or thawing temperature of foods, etc., have a simple structure, high heat resistance temperature of circuit elements, 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 it is compensated for by increasing the output, so the device cost is high and the residual heat of the filament is necessary. There is a problem that it takes time to start up the device.

On the other hand, a semiconductor high-frequency power source that performs power amplification by controlling high-speed switching of a semiconductor is characterized by its small size and high efficiency as a system when combined with a high-resolution automatic matching unit, and has been used for applications such as plasma discharge. Has been. As the circuit configuration of the automatic matching device used in the plasma discharge, an inverted L type shown in FIG. 1A and a π type shown in FIG.
FIG. 1A includes a first capacitor C1 connected in parallel to the high-frequency power source 20, a second capacitor C2 connected in series to the electrode 30, and a coil L. The first capacitor C1 and the second capacitor This is a configuration that performs impedance matching by making C2 variable in capacity and sequentially changing the value in real time.
Here, when 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 an impedance matching range by the variable capacitance capacitors C1 and C2. At this time, since 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, for example, it is an impedance for a load having a large resistance or impedance such as food. Alignment cannot be done properly.
Here, each symbol in the above expression is ω: angular frequency, R: output impedance of the power supply, L: reactance of the coil, C ₁ : capacitance of the variable capacitance first capacitor, C ₂ : capacitance of the variable capacitance second capacitor. It 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. The coil L is connected, the first capacitor C1 and the third capacitor C3 are variable in capacitance, and impedance matching is performed by changing the value in real time.
However, in the configuration in which the capacitance of the third capacitor C3 is variable and the value is sequentially changed, the electrode impedance is also sequentially changed accordingly, and in particular, the load between the electrodes 30 is a large capacity like food, When the electrode impedance changes greatly depending on the shape, type, heating or thawing temperature, the change is promoted, and it is difficult to keep impedance matching stably. In order to maintain the impedance matching in a state where the electrode impedance is not stable, it is necessary to provide the first capacitor C1 with a large impedance adjustment width, which causes a problem that the matching unit 40 is large in size and high in cost.

As a high-frequency dielectric heating device that avoids the problem of upsizing of the matching unit, the matching circuit has a variable capacitor in parallel with the high-frequency power source and a variable coil in series with the electrode, and the capacity of the capacitor can be increased by switching means A high-frequency dielectric heating apparatus is 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 supply is detected by the reflected power detection means, and based on the detection signal of the reflected power detection means, the values of the variable capacitor and the variable coil are appropriately combined, Impedance matching is used to keep reflected power to a minimum.

JP 2005-56781 A

  The high-frequency dielectric heating device described in Patent Document 1 is configured to adjust the impedance by changing the capacitance of the capacitor or the coil. In particular, when the impedance change is large, such as when the food is thawed, Therefore, it is necessary to increase the impedance adjustment width by the coil or the capacitor, and the matching unit cannot be reduced in size.

  Therefore, the present invention is intended to solve these problems, and is intended for heating or thawing of food with a small, high-efficiency semiconductor high-frequency power source. The electrode impedance depends on the shape, type, heating or thawing temperature of the food. It is possible to perform impedance matching satisfactorily while suppressing the change and simplifying the miniaturization and miniaturization even in a situation that is likely to change, and it can be heated or thawed in a compact, inexpensive and high quality manner. An object of the present invention is to provide a semiconductor type high frequency dielectric heating device.

  The present invention is a semiconductor type high frequency dielectric heating device comprising a semiconductor type high frequency power supply, a pair of electrodes arranged opposite to each other, and an impedance matching unit, wherein the matching unit is connected in parallel with the high frequency power source. One capacitor, a third capacitor connected in parallel with the electrode, a coil and a second capacitor connected in series between the first capacitor and the third capacitor, to solve the above problem It is.

  In the invention according to the first aspect of the present invention, the heating or thawing of the food is stably performed while suppressing the change in the electrode impedance by the small capacitor having high efficiency and the third capacitor connected in parallel with the electrode. be able to.

  In the invention according to claim 2, the capacitance of the capacitor can be adjusted by the capacitance varying means provided in at least one of the first capacitor and the second capacitor. For various foods having different shapes, types, and electrical characteristics. Impedance matching can be performed satisfactorily.

In the invention according to claim 3, at least the resistance of the impedance matching range formed by the output impedance of the high-frequency power supply and the matching unit includes a portion larger than the output impedance, and the reactance range is larger than positive and negative. This can be easily realized by setting the third capacitor to a predetermined value.
As described above, the impedance matching range is specialized for the thawing of the food material, so that the matching unit can be simplified and downsized. Further, by shortening the impedance matching time, damage and deterioration of the device can be prevented from the reflected power, and reliability can be improved.
According to the fourth aspect of the present invention, it is possible to easily obtain accurate information on the food impedance from the impedance information output unit of the matching unit, and set parameters of the matching unit narrowed down to the object to be heated. Or the matching unit can be simplified based on the result.

The circuit diagram which shows the reference example of the circuit structure of the automatic matching device for a plasma discharge use. The circuit diagram which shows the semiconductor type high frequency dielectric heating apparatus which concerns on one Embodiment of this invention The table | surface which shows the change of the capacity | capacitance of the 2nd capacitor when not providing the 3rd capacitor and when providing. The table | surface which shows the change of the capacity | capacitance of a 1st capacitor when not providing a 3rd capacitor and when providing. Explanatory drawing which shows the impedance matching range in the circuit structure shown in FIG. FIG. 3 is an explanatory diagram showing an impedance matching range in the circuit configuration shown in FIG. 2. The table | surface which shows the result of having measured the change of the capacity | capacitance of a 1st capacitor | condenser and a 2nd capacitor | condenser. The table | surface which shows the result of having measured the change of the capacity | capacitance of a 1st capacitor | condenser and a 2nd capacitor | condenser on conditions different from FIG.

  Below, semiconductor type high frequency dielectric heating device 10 concerning one embodiment of the present invention is explained based on a drawing.

  As shown in FIG. 2, the semiconductor high-frequency dielectric heating apparatus 10 includes a semiconductor high-frequency power source 20, a pair of electrodes 30, a matching unit 40 connected between the electrode 30 and the high-frequency power source 20, and impedance matching, A coaxial cable (not shown) for connecting the high-frequency power supply 20 and the matching unit 40, a reflected power detection unit (not shown) for detecting the power reflected to the high-frequency power supply 20, and a control unit (not shown) for controlling each part. The frozen food disposed between the pair of electrodes 30 provided opposite to each other is thawed by high frequency dielectric heating. The high frequency power supply 20 is configured to suppress or stop the high frequency output by the protection function when the reflectance detected by the reflected power detection unit exceeds a predetermined threshold.

  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, and a first capacitor C1 and a third capacitor C3. A circuit configuration that includes a coil L and a second capacitor C2 connected in series between the two and a third capacitor C3 connected in parallel to the electrode 30 inside the matching unit 40, thereby suppressing a change in electrode impedance. It has become.

  At least one of the first capacitor C1 or the second capacitor C2 is provided with a capacity varying means (not shown), and the capacity 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 variable capacitor driving in FIG. 2A or a multistage switching type by a relay in FIG. Further, the third capacitor C3 does not variably adjust the capacity during the thawing, but may be provided with a simple capacity variable mechanism in order to set the optimum value according to the load in advance.

In the circuit configuration of FIG. 2, if the combined impedance composed of 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: output impedance of the power source (coaxial cable resistance), L: reactance of the coil, C ₁ : capacitance of the first capacitor with variable capacitance, C ₂ : variable capacitance. The capacity of the second capacitor, C ₃ : the capacity of the third capacitor.
Here, when the complex conjugate of the combined impedance Z is Z ′, the range of Z ′ obtained by the variable capacitance width of the first capacitor C1 or the second capacitor C2 is the impedance matching range, and ω, R, L, C _It can be set freely 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 impedance matching range formed by the output impedance of the high frequency power supply 20 and the matching unit 40 is larger than the output impedance (a portion larger than the output impedance). The reactance range is more negative 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 or the second capacitor C2 in a decreasing direction according to the thawing state of the object to be heated. Designed for impedance matching. The control unit does not variably adjust the capacity of the third capacitor C3 during thawing.

  Hereinafter, experimental examples of the present invention will be described.

FIG. 3A shows the frequency of the high-frequency power source 20 = 13.56 MHz, the output impedance of the high-frequency power source 20 = 50Ω, the capacitance C ₁ of the first capacitor C ₁ = 1500 pF, and the capacitance C ₂ of the variable second capacitor C ₂ = 25. ˜250 pF, coil L inductance L = 1.8 μH, various food materials are thawed, and the value when the capacitance of the second capacitor C2 is adjusted so that the reflected power by the reflected power detection unit is always minimized ( Capacity%).
When the third capacitor C3 is not connected, the C2 capacity% at the start of thawing varies depending on the type and number of ingredients, and the C2 capacity% at the end of thawing varies greatly 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 unit 40 cannot be simplified and 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, and various foods are thawed so that the reflected power by the reflected power detection unit is always minimized. The values (capacity%) when the capacity of the second capacitor C2 is adjusted are shown. Various ingredients can be thawed without greatly changing the capacitance% of the second capacitor C2, and the matching unit 40 having a small 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 = 50Ω, the capacitance C ₂ of the second capacitor C2 = 95 pF, the inductance L of the coil L = 1.8 μH, and the variable capacitance first capacitor. capacity C1 _C 1 = 150~1500pF, third and capacitor _C 3 = 400pF capacitor C3, and extract the various ingredients, as reflected power due to the reflected power detection unit is always minimum, capacitance of the first capacitor C1 The value (capacity%) of C1 when adjustment is performed is shown. By connecting the third capacitor C3, the capacitance variable 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. 1A, the combined impedance of the high-frequency power supply 20 and the matching unit 40 is Z, and Z = R / (1 + ω ² R ² C ₁ ² ) + j {(ωL−1 / ωC ₂ ) −ωR ² C ₁ / (1 + ω ² R ² C ₁ ² )}, the impedance matching range obtained with the complex conjugate Z ′.
However, the angular frequency ω = 13.56 MHz, the output impedance R = 50Ω of the high frequency power supply 20, the reactance L of the coil L = 1.8 μH, the capacitance C ₁ of the variable capacitance first capacitor C ₁ = 150 to 1500 pF, the variable capacitance of the first capacitance of second capacitor C2 _C 2 = a 25～250PF.
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 source 20, and impedance matching is impossible for a resistance load larger than that.

6, in the circuit configuration of FIG. 2, assuming that the combined impedance composed of the output impedance of the high frequency power supply 20 and the matching unit 40 is Z, Z = 1 / [{(1 / R + jωC ₁ ) ⁻¹ + j (ωL−1 / 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 R of the power supply R = 50Ω, the reactance L of the coil L = 1.8 μH, the capacitance C ₁ of the variable capacitance first capacitor C ₁ = 150 to 1500 pF, the variable capacitance second capacitor C2 of the capacitor _C 2 = _25~250pF, third capacitance _C 3 = 50 pF capacitor C3, 200pF, 400pF, and 600 pF.
By connecting the third capacitor C3 in parallel with the electrode 30 and increasing its value, the impedance matching range obtained with Z ′ in the example shown in FIG. 5 described above rotates counterclockwise and the resistance of Z ′ Is expanded to a range larger than the output impedance R of the power source = 50Ω (standardized impedance 1). The reactance range was greater than positive when the capacitance of the third capacitor C3 was C ₃ = 200 pF and 400 pF, and was less than negative when C ₃ = 600 pF. Thus, by connecting the third capacitor C3 in parallel with the electrode 30, a matching range specialized for thawing frozen foods can be obtained.

FIG. 7 shows the frequency of the high-frequency power source 20 = 13.56 MHz, the output impedance of the high-frequency power source 20 = 50Ω, the inductance L of the coil L = 1.8 μH, the capacitance C ₁ of the variable capacitor first capacitor C1 = 150 to 1500 pF, capacitance of the capacitor C2 _C 2 = 25~250pF, capacitance _C 3 = 200 pF of the third capacitor C3, and 400pF, -40 ° C. refrigeration Shine Muscat 15 grains (thickness 28mm) output 50 W, thawed on thawing time 15 minutes This shows the values (capacity%) of C ₁ and C ₂ when the capacitor capacities of the variable capacitors C ₁ and C ₂ are automatically and sequentially adjusted by the servo motor so that the reflected power from the reflected power detector is always minimized.
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 the thawing, but the change of the variable capacitors C1 and C2 is suppressed by connecting the third capacitor C3, 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 = 50Ω, the inductance L of the coil L = 1.8 μH, the capacitance C ₁ of the variable capacitor first capacitor C ₁ = 150 to 1500 pF, capacitance of the capacitor C2 _C 2 = 25~250pF, capacitance _C 3 = 200 pF of the third capacitor C3, and 400pF, outputs -40 ℃ refrigeration mango (thickness 85 mm) 200 W, and extract with thawing time 15 minutes, reflecting The values (capacity%) of C ₁ and C ₂ are shown when the capacitor capacities of the variable capacitors C ₁ and C ₂ are sequentially and automatically adjusted by the servo motor so that the reflected power by the power detector is always minimized.
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 the thawing, but in the state where C ₃ = 200 pF is connected, the change of the variable capacitors C1 and C2 is suppressed. Yes. When C ₃ = 400 pF was connected, automatic impedance matching could not be performed.

From the above, the semiconductor high-frequency dielectric heating device 10 suppresses a change in electrode impedance due to the thawing of food by connecting the third capacitor C3 in parallel with the electrode 30 to the matching device 40, thereby simplifying the matching device 40. It was confirmed that impedance matching was possible while miniaturizing.
At this time, the larger capacitor value of the third capacitor C3 is more effective in suppressing the change in electrode impedance. However, when the frozen food is thick, matching may be difficult. Therefore, it is preferable to set an optimal value of C3.

  As mentioned above, although embodiment of this invention was explained in full detail, this invention is not limited to the said embodiment, A various design change can be performed without deviating from this invention described in the claim. Is possible.

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

  In addition to the above-described embodiment, an impedance information output unit that outputs impedance information (for example, the state of the first capacitor) of the matching unit to a monitoring monitor or the like may be provided. In this case, it is possible to easily obtain accurate information on food impedance from the impedance information output unit of the matcher, and set the matcher parameters narrowed down to the object to be heated and match based on the result. The device 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 etc., but can also be widely applied as an industrial dielectric heating device. Industrial applicability is high, for example, it can be incorporated into a microwave oven or refrigerator.

DESCRIPTION OF SYMBOLS 10 ... Semiconductor type high frequency dielectric heating apparatus 20 ... High frequency power supply 30 ... Electrode 40 ... Matching device C1 ... 1st capacitor C2 ... 2nd capacitor C3 ... 3rd capacitor L .. Coils

Claims (4)

A semiconductor type high frequency dielectric heating device comprising a semiconductor type high frequency power source, a pair of electrodes arranged opposite to each other, and an impedance matching device,
The matching unit includes a first capacitor connected in parallel with the high-frequency power source, a third capacitor connected in parallel with the electrode, and a coil connected in series between the first capacitor and the third capacitor. And a semiconductor-type high-frequency dielectric heating device comprising a second capacitor.   2. The semiconductor type high frequency dielectric heating device according to claim 1, wherein at least one of the first capacitor and the second capacitor is provided with a capacity varying means.   Regarding the impedance matching range formed by the output impedance of the high-frequency power supply and the matching unit, 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. The semiconductor type high frequency dielectric heating device according to claim 1 or 2, wherein the device is a semiconductor high frequency dielectric heating device.   The semiconductor high frequency dielectric heating apparatus according to claim 1, further comprising an impedance information output unit that outputs impedance information of a matching unit to the semiconductor high frequency dielectric heating apparatus.

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