High-frequency thawing device

Abstract

To provide a high-frequency thawing device which attains circuit downsizing and reduction of cost and is capable of performing uniform thawing.SOLUTION: A high-frequency thawing device 100 comprises an upper flat electrode 4 and a lower flat electrode 5 which are connected to a high frequency power source 1. An upper spiral electrode is connected to the upper flat electrode 4. The upper spiral electrode has a length, which is an integer multiple of a 1 / 4 wavelength λ of a power transmission frequency from the high frequency power source 1, and consists of a first upper spiral electrode 6 and a second upper spiral electrode 7 of which the outer peripheral end is connected with the upper flat electrode 4 and the inner peripheral end is opened. The first upper spiral electrode 6 and the second upper spiral electrode 7 are disposed in point symmetry and at an equal interval in such a manner that mutual spirals are not overlapped, and induction heating is performed on a frozen food material which is disposed between the first and second upper spiral electrodes 6 and 7 and the lower flat electrode 5.SELECTED DRAWING: Figure 1A

Description

Technical Field

[0001] The present invention relates to a high-frequency dielectric heating device, and particularly to a high-frequency thawing device that applies a high-frequency electric field in the MHz band to frozen food and thaws the frozen food by dielectric heating.

Background Art

[0002] In food processing factories and the like, there are cases where frozen food ingredients are thawed for food processing. As a type of thawing machine used in food processing factories and the like, a high-frequency thawing device is known that applies a high-frequency electric field in the MHz band to frozen food placed between opposing electrodes and thaws the frozen food by dielectric heating.

[0003] High-frequency dielectric heating is a technique in which a high-frequency voltage is applied to a dielectric that is the object to be heated, and the object to be heated is heated from the inside by self-heating (dielectric loss) caused by the vibration of polar molecules that make up the object to be heated. In dielectric heating by microwaves (GHz band) using a microwave oven, since the heat generation difference between ice and water is large, uneven heating occurs because the melted part on the surface layer of the food generates significant heat. However, it is generally known that high-frequency dielectric heating using a frequency band lower than microwaves has the advantage that the penetration depth of energy is deeper than that of microwaves, and the difference in heat generation between ice and water is also small, so uneven heating is less likely to occur.

[0004] As a conventional technique for dielectric heating using a high-frequency electric field in the MHz band, for example, there is the technique described in Patent Document 1. Patent Document 1 describes a high-frequency heating device configured to detect an impedance change accompanying a temperature rise of an object to be heated by a reflected power detection means when heating the object to be heated placed between electrodes with high-frequency power in the MHz band from a high-frequency power source, and to switch the constants of a matching circuit composed of a variable inductor and a capacitor to maintain a matching state.

[0005] In addition, Patent Document 2 describes a high-frequency power supply application device in the MHz band used in plasma processing such as semiconductor dry etching and thin film formation. The configuration thereof is shown in FIG. 13. FIG. 13 is a schematic diagram of a high-frequency power supply application device related to the prior art.

[0006] As shown in FIG. 13, the high-frequency power supply application device is composed of a first high-frequency power supply 1301, a matching circuit 1302, a chamber 1303, and a second high-frequency power supply 1308. A coil 1304, a workpiece 1305, a lower electrode 1306, and an insulator 1307 are arranged in the chamber 1303.

[0007] The MHz-band high-frequency signal (RF signal) from the high-frequency power supply 1301 is impedance-matched to the workpiece 1305 placed between the coil 1304 and the lower electrode 1306, which has a length approximately an integer multiple of 1 / 4 of the wavelength of the high-frequency power, by the matching circuit 1302. As a result, a standing wave with an integer multiple of 1 / 4 wavelength is generated in the coil 1304 with a large voltage amplitude. A high electric field is applied to the workpiece 1305 by this voltage amplitude, and plasma processing is performed by efficiently transmitting high-frequency power. Further, a high-frequency voltage is applied to the workpiece 1305 through the lower electrode 1306 arranged on the insulator 1307 by the second high-frequency power supply 1308, so that power is efficiently transmitted to the workpiece 1305.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0009] When applying the high-frequency power supply device (Fig. 13) of Patent Document 2 to the high-frequency heating device of Patent Document 1 to thaw food by dielectric heating, power on the order of several hundred watts is required. In this case, as with the high-frequency heating device of Patent Document 1, a voltage of more than several thousand volts is generated in the matching circuit. When heating an object to be heated placed between the parallel plate electrodes shown in Patent Document 1, an electric field is generated almost uniformly on the electrode surface of the parallel plate electrodes. However, in the case of the coil of Patent Document 2, an even higher electric field is generated in the vicinity of the winding than in the parallel plate electrodes. For this reason, in thawing by dielectric heating using a coil, since the electric field in the portion along the winding of the coil becomes higher, a difference occurs in the electric field applied to the food between the portion directly under the coil and the portion between the windings of the coil on the food surface. In addition, since a standing wave is generated in the coil, there is a problem that uneven heating easily occurs along the winding of the coil centered on directly under the portion where the voltage amplitude is the highest, and uniform heating cannot be achieved.

[0010] Furthermore, when trying to enlarge the coil (spiral electrode) in order to thaw a large food, the coil length cannot be easily increased in order to utilize the resonance of the standing wave generated on the coil. For this reason, the pitch of the coil widens and the potential difference between the coil windings increases, so uneven heating becomes even greater, making it difficult to increase the size of the electrode.

[0011] Another problem is that, in order to generate a high electric field using the resonance of the coil, a voltage of more than several thousand volts is generated at both ends of the coil. Therefore, the matching circuit for matching with the coil requires high voltage resistance, resulting in a high cost problem.

[0012] Furthermore, as the thawing of the food progresses, the dielectric constant of the food changes in the direction of increasing, and accordingly, the capacitance between the wirings of the coil increases, so the resonance frequency of the coil changes. For this reason, the matching circuit for impedance matching with this resonance frequency shift requires a wide adjustment range, so the number of switching elements of inductors and capacitors for matching increases, the shape becomes large, and parasitic inductors and capacitance components increase, making it difficult to achieve matching.

[0013] An object of the present invention is to solve the above problems, reduce the size and cost of a circuit, and provide a high-frequency thawing device capable of homogeneous thawing.

Means for Solving the Problems

[0014] To achieve the above object, the present invention, as an example, includes an upper flat electrode and a lower flat electrode disposed opposite to each other vertically in a housing, an upper spiral electrode disposed below the upper flat electrode and connected to the upper flat electrode, a high-frequency power supply having one connected to the upper flat electrode and the other connected to the lower flat electrode for supplying high-frequency power. The upper spiral electrode is composed of a first upper spiral electrode and a second upper spiral electrode, the length of the upper spiral electrode being an integer multiple of 1 / 4 of the wavelength λ of the power transmission frequency from the high-frequency power supply, the outer peripheral end being connected to the upper flat electrode, and the inner peripheral end being open. The first upper spiral electrode and the second upper spiral electrode are arranged point-symmetrically and at equal intervals so that their spirals do not overlap, and a heated object disposed between the first upper spiral electrode, the second upper spiral electrode, and the lower flat electrode is dielectrically heated.

Effects of the Invention

[0015] According to the present invention, it is possible to provide a high-frequency thawing device capable of reducing the size and cost of a circuit and achieving homogeneous thawing.

Brief Description of the Drawings

[0016]

Figure 1A

Figure 1B

Figure 1C

Figure 2A

Figure 2B

Figure 2C

Figure 3A

Figure 3B

Figure 4A

Figure 4B

Figure 5

Figure 6

Figure 7

Figure 8A

Figure 8B

Figure 8C

Figure 9

Figure 10

Figure 11

Figure 12A

Figure 12B

Figure 12C

Figure 13

Mode for Carrying Out the Invention

[0017] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The high-frequency thawing device according to the embodiments of the present invention is based on the principle of high-frequency dielectric heating and can be widely applied in the heating scene of the object to be heated. However, in the following embodiments, the case of specialized use for thawing will be described. In the figure, when viewed from the rear used by the user, it is defined as up and down, front and rear, and left and right as indicated by the arrows.

[0018] Also, in the embodiments of the present invention, a high-frequency thawing device is installed in the backyard of a convenience store, supermarket or other retail store, or a restaurant, etc., and frozen foods and food materials such as boxed lunches, prepared foods, and meats stored in a frozen state are thawed according to the number of customers entering the store, and then arranged as chilled products on the display shelves in the store, or the thawed food materials are cooked and provided to customers.

[0019] However, the following description shows specific examples of the content of the present invention, and the present invention is not limited to these descriptions. Various changes and modifications can be made by those skilled in the art within the scope of the technical idea disclosed in this specification.

Examples

[0020] Figure 1A is a configuration diagram showing an overview of a high-frequency thawing device according to Embodiment 1 of the present invention. The high-frequency thawing device 100 includes a high-frequency power supply 1 that outputs an MHz band such as 13.56 MHz, 27.12 MHz, or 40.68 MHz, which is an ISM band (Industrial, Scientific and Medical), an antenna tuner 2 (adjustment circuit), a housing 3, an upper flat electrode 4, a lower flat electrode 5, and upper spiral electrodes (a first upper spiral electrode 6 and a second upper spiral electrode 7). The housing 3 forms the outer shell of the high-frequency thawing device 100. The upper flat electrode 4 and the lower flat electrode 5 are arranged to face each other in the vertical direction within the housing 3. The frozen food 8 (object to be heated) is arranged between the first upper spiral electrode 6 and the second upper spiral electrode 7 and the lower flat electrode 5. Then, the frozen food 8 (object to be heated) is thawed by dielectric heating caused by the electric field generated by these electrodes (the upper flat electrode 4, the lower flat electrode 5, the first upper spiral electrode 6, and the second upper spiral electrode 7).

[0021] One side of the high-frequency power supply 1 is connected to the upper flat electrode 4 via the antenna tuner 2, and the other side of the high-frequency power supply 1 is connected to the lower flat electrode 5. Also, the lower flat electrode 5 is connected to the housing 3. The housing 3 serves as a frame ground (FG). The antenna tuner 2 adjusts the impedance matching with the upper flat electrode 4 by adjusting the constants.

[0022] Also, Figure 1B is a diagram showing an overview of the cross-sectional configuration of the high-frequency thawing device according to Embodiment 1 of the present invention, and Figure 1C is a diagram showing an example of the arrangement of the spiral electrodes according to Embodiment 1 of the present invention. The same parts as those in Figure 1A are given the same numbers, and the operation will be described using these figures.

[0023] The upper flat electrode 4 and the lower flat electrode 5 are formed of, for example, aluminum plates. The first upper spiral electrode 6 and the second upper spiral electrode 7 are arranged below the upper flat electrode 4 (on the side facing the lower flat electrode 5) and have a length that is an integral multiple of 1 / 4 of the wavelength λ of the transmission frequency of the high-frequency power supply 1. The outer peripheral ends of these spiral electrodes are connected to the upper flat electrode 4, and the inner peripheral ends are in an open state. The first upper spiral electrode 6 and the second upper spiral electrode 7 are arranged symmetrically with respect to each other at equal intervals so that their spirals do not overlap. Further, the first upper spiral electrode 6 and the second upper spiral electrode 7 are formed by laminating copper plates and are arranged about 15 mm below the upper flat electrode 4.

[0024] When high-frequency power in the MHz band from the high-frequency power supply 1 is applied between the upper flat electrode 4 and the lower flat electrode 5 that is GND (ground) connected to the housing 3, an electric field is generated in the flat electrode. Due to this electric field, the first upper spiral electrode 6 and the second upper spiral electrode 7 are excited by the potential difference with the lower flat electrode 5, and a standing wave is generated. At this time, since the length of the spiral electrode is an integral multiple of 1 / 4 of the wavelength λ of the transmission frequency of the high-frequency power supply 1, the outer peripheral end of the spiral electrode has the minimum amplitude and the inner peripheral end has the maximum amplitude, and the electric field is concentrated at the center of the electrode.

[0025] Furthermore, as shown in FIG. 1C, since the second upper spiral electrode 7 is arranged between the winding pitches of the first upper spiral electrode 6, a symmetric configuration is formed. Equivalently, the pitch interval of the spiral electrode becomes 1 / 2, and the electric field concentration is alleviated. In particular, it is possible to reduce the uneven heating that easily occurs on the surface of the foodstuff directly below the spiral electrode at the center where the electric field is high.

[0026] Also, the power supply point 10 shown in FIG. 1C indicates the connection point between the antenna tuner 2 and the upper flat electrode 4. By connecting at an equal distance from the short points of the first upper spiral electrode 6 and the second upper spiral electrode 7 to the upper flat electrode 4, the symmetry between the first upper spiral electrode 6 and the second upper spiral electrode 7 can be better maintained.

[0027] Incidentally, since the current Ia flowing through the first upper spiral electrode 6 shown in FIG. 1C and the current Ib flowing through the second upper spiral electrode 7 are in the same direction and have substantially equal magnitudes, the interference between the spiral electrodes is small, and the configuration is such that these effects do not need to be considered. An example of the design constants of the spiral electrodes shown in FIG. 1C is as follows: the pattern width is 1 cm, the pitch interval between the first upper spiral electrode 6 and the second upper spiral electrode 7 is 1 cm, and the size is 27 cm in length and 29 cm in width.

[0028] Here, the dielectric heating principle of this embodiment will be described with reference to FIG. 2A. Note that the parts overlapping with FIG. 1A are given the same reference numerals and the description thereof is omitted. FIG. 2A is a diagram showing the electric field due to the standing wave generated on the λ / 4 spiral electrode and the current distribution flowing through the spiral electrode in the high-frequency thawing device of FIG. 1A. In the figure, the length of the lower spiral electrode 201 is made one-fourth of the wavelength, the outer peripheral end is connected (shorted) to the lower flat electrode 5, and the inner peripheral end is in an open state. Thus, due to the potential difference with the upper flat electrode 4, a standing wave of λ / 4 open short is excited in the lower spiral electrode 201. In this standing wave, the potential of the inner peripheral end is higher than that of the outer peripheral end, which is at the same potential as the flat electrode, by the amplitude of the standing wave, so the electric field at the central part becomes higher. On the other hand, since the inner peripheral end of the spiral electrode 201 is in an open state, no current flows, and the operation is such that the current flows most at the outer peripheral end.

[0029] In FIG. 2A, the lower spiral electrode 201 is connected to the lower flat electrode 5. Similarly, on the upper flat electrode 4 side, the electric field concentration effect can be further obtained by connecting spiral electrodes to both the upper and lower flat electrodes. At this time, for the current flowing through the spiral electrodes, the magnetic fluxes generated in the winding directions of the upper and lower spiral electrodes may be in the same direction or in the opposite direction. When the magnetic fluxes are in the same direction and in the opposite direction, the equivalent λ / 4 lengths are different. For example, when the winding directions of the upper and lower spiral electrodes are opposite when viewed from above, the generated magnetic fluxes are in the same direction and strengthen each other, increasing the equivalent inductance of the spiral electrodes. Therefore, the upper and lower spiral electrodes are slightly shortened by the amount of mutual coupling. On the other hand, when the winding directions of the upper and lower spiral electrodes are the same when viewed from above, the magnetic fluxes are in the opposite direction and the equivalent inductance decreases. Therefore, it is necessary to lengthen the length of the spiral electrodes by the amount of mutual coupling.

[0030] FIGS. 2B and 2C are diagrams for explaining the operation of an electric field diffusion plate, which is a metal plate arranged between a spiral electrode and a frozen food to uniformize the electric field from the spiral electrode, as another means for performing homogeneous thawing by arranging two spiral electrodes in point symmetry. FIG. 2B is an electrode configuration diagram for explaining the operation of the electric field diffusion plate. FIG. 2C is a cross-sectional configuration diagram for explaining the operation of the electric field diffusion plate.

[0031] In these figures, the electric field diffusion plate 9 is composed of a central electrode plate 202, notches 203, 204, and a coupling capacitance 205 of the electric field diffusion plate 9. For other parts that overlap with FIG. 1, the same numbers are assigned and the description is omitted.

[0032] The electric field diffusion plate 9 includes a frame portion 206, 207 that forms the periphery, notches 203, 204 where a part of the frame portion 206, 207 is cut out, a connection portion 208 that connects the notched frame portions 206, 207, and a central electrode plate 202 that is located at the central portion of the connection portion 208 and is formed wider than the width of the connection portion 208.

[0033] In other words, the electric field diffusion plate 9 has two U-shaped frame portions 206 and 207 formed such that the open sides thereof face each other with a gap therebetween, the central portions of the frame portion 206 and the frame portion 207 are connected by a connecting portion 208, and a central electrode plate 202 is provided at the central position of the connecting portion.

[0034] In FIG. 2B, since the central portion of the lower spiral electrode 201 and the central electrode plate 202 of the electric field diffusion plate 9 are coupled (capacitively coupled) by a coupling capacitance 205, an electric field generated by electric field coupling is generated at the central portion of the electric field diffusion plate 9. Further, since it is connected to the metal plate on the outer peripheral portion of the frozen food 8, an electric field (electric field E' shown in FIG. 2C) substantially at the same level as the electric field (electric field E shown in FIG. 2C) generated by the electric field coupling at the central portion is generated throughout the electric field diffusion plate 9. At this time, as shown in FIG. 2C, the electric field diffusion plate 9 is disposed between the lower spiral electrode 201 and the frozen food 8, so that substantially the entire frozen food 8 is heated at the same electric field level, enabling uniform thawing. Further, increasing the central electrode plate 202 of the electric field diffusion plate 9 can increase the capacitive coupling with the lower spiral electrode 201. However, when the coupling amount is insufficient, it is also possible to adjust the capacitive coupling amount by increasing the width of the inner peripheral end of the lower spiral electrode 201.

[0035] FIG. 3A is a diagram showing an example of the analysis results of the impedance characteristics and return loss characteristics of the electrodes of the high-frequency thawing device according to Embodiment 1 of the present invention. In FIG. 3A, in the high-frequency thawing device shown in FIG. 2A, when the lower spiral electrode 201 of the lower flat electrode 5 is also arranged on the upper flat electrode 4, the electromagnetic field analysis results of the impedance characteristics and return loss (reflection attenuation amount) characteristics between the upper flat electrode 4 and the lower flat electrode 5 are shown. FIG. 3B is a diagram showing an example of the analysis results between the electrodes of the high-frequency heating device shown in Patent Document 2 as the prior art. Note that for the return loss characteristics, the horizontal axis is the frequency [MHz], the vertical axis is the return loss [dB], and the lower the value, the better the matching, and at 0 dB, total reflection occurs. The analysis was performed with the upper and lower flat electrodes being 30 cm × 30 cm and the spiral electrode length being approximately 200 cm so as to resonate at a frequency of 40.68 MHz. As the food material, a simulated food material with a size of 20 cm × 20 cm × 5 cm frozen to -20°C was used. In the prior art of FIG. 3B, calculations were performed using electrodes with a size of 30 cm × 30 cm as parallel flat electrodes. The results of varying the frequency from 10 MHz to 100 MHz are shown.

[0036] In FIG. 3B, it can be seen that in the conventional thawing using parallel flat plates, the inter-electrode impedance shows capacitive characteristics, and in terms of the return loss characteristics, it is almost a total reflection characteristic. Therefore, when matching is achieved using a matching circuit, even if the transmitted power is about several hundred watts, a high voltage of more than several thousand volts is generated between the electrodes due to the matching inductor and the series resonance of the electrodes. For this reason, the conventional high-frequency thawing machine requires a high withstand voltage matching circuit, which leads to a problem that the circuit becomes large and the cost increases.

[0037] On the other hand, in the electrode of this embodiment shown in Fig. 3A, due to the inductor component of the spiral electrode, a matching point due to series resonance occurs between the parallel plates at a transmission frequency of around 40.68 MHz with the capacitance component of the parallel plates and the food material. Therefore, the voltage generated between the parallel plates becomes relatively low, about 200V. For this reason, since the shift of the matching point due to the change in the dielectric constant accompanying the thawing state of the food material can be adjusted by an antenna tuner with low withstand voltage and low cost used in general amateur radio etc., miniaturization and cost reduction of the circuit can be achieved.

[0038] Fig. 4A is a diagram showing an example of the configuration of the antenna tuner 2 of the high-frequency thawing device shown in Fig. 1A. In Fig. 4A, inductors 421, 422, and 423 are connected in series to the tuner input terminal 401 and the tuner output terminal 402, and relays 411, 412, and 413 are connected in parallel to both ends of each inductor, respectively. By switching the relay with a control signal from the control terminal 403, it is possible to change the series inductance value. Also, capacitors 424, 425, 426, and 427 are connected in parallel via relays 415, 416, 417, and 418, respectively, between the tuner input terminal 401 or the tuner output terminal 402 and GND, and the configuration is such that the grounding capacitance value to GND can be switched. Furthermore, the configuration is such that it is possible to switch whether the capacitance value switching of the ground is connected to the tuner input terminal 401 side or the tuner output terminal 402 side by the relay 414. Generally, when the impedance of the tuner output side is higher than that of the tuner input side, the tuning operation is performed by switching to the tuner output side, and when it is lower, it is switched to the tuner input side.

[0039] In the circuit of the antenna tuner 2, due to the parasitic inductor 431 (parasitic inductor component) generated by the routing of the inductor serially connected between the tuner input and output terminals and the parasitic capacitance 433 generated by the routing of the capacitance parallely connected between the tuner input and output terminals, jumps occur where the change range is larger than the design constants when switching the inductance value and capacitance value by the relay, resulting in lack of matching or insufficient matching and increased reflected power and decreased heating efficiency. Therefore, a canceling capacitance 432 (first canceling element) that resonates at the power transmission frequency of the high-frequency power supply is serially connected to the parasitic inductor 431 (parasitic inductor component) generated by the routing of the inductor serially connected between the input and output terminals of the antenna tuner, and an inductor 434 (second canceling element) that resonates at the power transmission frequency of the high-frequency power supply is parallely connected to the parasitic capacitance 433 (parasitic capacitance component) generated by the routing of the inductor parallely connected between the input and output terminals of the antenna tuner.

[0040] With such a configuration, it becomes possible to reduce the parasitic components due to the pattern routing of the antenna tuner in the power transmission frequency band, so a defroster with less reflected power and excellent convergence can be obtained.

[0041] Figure 4B is a diagram showing another example of the antenna tuner. In Figure 4B, an inductor 442 is connected between the tuner input terminal 401 and the tuner output terminal 402, and variable capacitance capacitors (varicaps) 441 and 443 are connected between the input and output terminals of the tuner and GND, respectively. In this figure, the variable capacitance capacitors (varicaps) 441 and 443 require a mechanism for mechanical adjustment. However, by using variable capacitance capacitors, it becomes possible to continuously adjust the deviation of the matching point. In addition, since there is no switching circuit by a relay, the routing of the wiring is shortened, so an antenna tuner circuit with excellent convergence can be obtained without adding inductors and capacitors for canceling parasitic components.

[0042] According to this embodiment, it is possible to provide a high-frequency thawing device capable of miniaturizing and reducing the cost of a circuit, and capable of homogeneous thawing with excellent convergence of a matching circuit.

Embodiment

[0043] FIG. 5 is a configuration diagram showing an outline of a high-frequency thawing device according to Embodiment 2 of the present invention. The high-frequency thawing device 200 includes at least an RF signal source 501 (RF: Radio Frequency) that outputs an MHz band such as 13.56 MHz, 27.12 MHz, and 40.68 MHz, an attenuator 502, a high-frequency power amplifier 503, a power supply circuit 504, a directional coupler 505, a control circuit 506, a temperature sensor 507, a first lower spiral electrode 521, and a second lower spiral electrode 522. Further, the high-frequency power amplifier 503 includes a distribution circuit 511, a high-frequency amplifier 512, and a combining circuit 513. In addition, the same reference numerals are given to the parts overlapping with those of the high-frequency thawing device of Embodiment 1 shown in FIG. 1A, and the description thereof is omitted.

[0044] The high-frequency thawing device 200 shown in FIG. 5 is different from FIG. 1 in that an RF signal source 501, an attenuator 502, a high-frequency power amplifier 503, a power supply circuit 504, and a directional coupler 505 are applied instead of the high-frequency power supply 1 (FIG. 1), and a power supply circuit 504, a control circuit 506, a temperature sensor 507, and lower spiral electrodes (a first lower spiral electrode 521 and a second lower spiral electrode 522) are added.

[0045] The high-frequency thawing device 200 in FIG. 5 is configured such that a first lower spiral electrode 521 and a second lower spiral electrode 522 are disposed above a lower flat electrode 5 so as to face a first upper spiral electrode 6 and a second upper spiral electrode 7 disposed on an upper flat electrode 4.

[0046] The first lower spiral electrode 521 and the second lower spiral electrode 522 are arranged above the lower flat electrode 5 (on the side facing the upper flat electrode 4), and have a length that is an integer multiple of 1 / 4 of the wavelength λ of the transmission frequency of the high-frequency power supply 1. The outer peripheral ends of these spiral electrodes are connected to the lower flat electrode 5, and the inner peripheral ends are in an open state. The first lower spiral electrode 521 and the second lower spiral electrode 522 are arranged point-symmetrically with equal intervals so that their spirals do not overlap each other. Also, the first lower spiral electrode 521 and the second lower spiral electrode 522 are formed by laminating copper plates and are arranged about 15 mm above the lower flat electrode 5.

[0047] Also, the upper spiral electrode and the lower spiral electrode are arranged with opposite winding directions so that the directions of the magnetic fluxes of the upper spiral electrode and the lower spiral electrode are the same. The high-frequency power supply 1 applies an RF signal source 501, an attenuator 502, a high-frequency power amplifier 503, a power supply circuit 504, and a directional coupler 505, and a power supply circuit 504, a control circuit 506, and a temperature sensor 507 are added.

[0048] The high-frequency power amplifier 503 in FIG. 5 attenuates the high-frequency in the MHz band from the RF signal source 501 to a desired high-frequency power by the attenuator 502, then distributes it to each high-frequency amplifier 512 by a distribution circuit 511 to perform power amplification, and synthesizes the high-frequency power of about 100 W to 1000 W synthesized by a synthesis circuit 513 through the directional coupler 505 and the antenna tuner 2 and supplies it to the electrodes.

[0049] The directional coupler 505 measures the incident power and the reflected power at the input of the antenna tuner 2 and outputs the results to the control circuit 506. The control circuit 506 is configured to optimize the constants of the antenna tuner 2 so that the reflected power of the directional coupler 505 becomes small. Also, the control circuit 506 measures the temperature of the frozen food 8 from the temperature sensor 507 and stops power transmission when the target thawing temperature is reached. Alternatively, the control circuit 506 is configured to adjust the output power by the attenuator 502 according to the temperature state.

[0050] In the above configuration, the frozen food 8 placed between the upper and lower spiral electrodes is thawed by dielectric heating using the RF signal amplified by the high-frequency power amplifier 503. However, the directional coupler 505 detects the impedance variation between the electrodes due to the variation in the dielectric constant of the food, which changes depending on the size and thawing state of the frozen food, and the control circuit 506 adjusts the constants of the antenna tuner 2 to match the impedance of the electrodes, thereby performing efficient thawing. Also, the completion of thawing is determined by measuring the temperature of the frozen food 8 using the temperature sensor 507.

[0051] Furthermore, in this embodiment, for example, the lengths of the first upper spiral electrode 6 and the first lower spiral electrode 521 are set to lengths that resonate with the transmission frequency (40.68 MHz in this embodiment) at the dielectric constant at the start of thawing of the frozen food 8, and the lengths of the second upper spiral electrode 7 and the second lower spiral electrode 522 are set to lengths that resonate at the dielectric constant at the end of thawing of the frozen food 8. By configuring in this way, the resonance frequency band between the spiral electrode and the food is widened, and the adjustment range of the matching of the antenna tuner 2 is narrowed, so the convergence of the antenna tuner is improved, and it is possible to avoid thawing in a state where matching cannot be achieved due to a jump in constants caused by parasitic components of the antenna tuner or where the matching is insufficient and the reflected wave is large and the heating efficiency is poor. For example, at a transmission frequency of 40.68 MHz, the spiral electrode length that resonates at λ / 4 is about 2 m, but even if the lengths of the first and second spiral electrodes differ by about 6 cm, it is possible to widen the resonance frequency band.

[0052] Next, the process from the start to the end of thawing of the frozen food 8 will be described with reference to FIG. 11. FIG. 11 is a flowchart showing the process from the start to the end of dielectric heating of the high-frequency thawing device according to Embodiment 2 of the present invention.

[0053] In FIG. 11, as the thawing of the frozen food 8 progresses, the dielectric constant changes, causing the impedance matching point between the electrodes to shift. Therefore, it mainly describes the operation of adjusting the matching point from the antenna tuner 2 and performing thawing while maintaining a state of good heating efficiency.

[0054] Set the frozen food 8 between the upper spiral electrodes (the first upper spiral electrode 6 and the second upper spiral electrode 7) and the lower spiral electrodes (the first lower spiral electrode 521 and the second lower spiral electrode 522), and start thawing the frozen food 8 (step S100).

[0055] The control circuit 506 performs a reset of the antenna tuner 2 (step S101), adjusts the attenuator 502, and starts transmitting power at a power lower than the power required for normal thawing from the high-frequency power amplifier 503 (step S102).

[0056] Next, the control circuit 506 measures the incident power amount and the reflected power amount from the directional coupler 505, and adjusts the antenna tuner 2 so that the reflected power becomes minimum (step S103).

[0057] The control circuit 506 calculates the VSWR (Voltage Standing Wave Ratio) indicating the matching state calculated from the incident power amount and the reflected power amount, and determines whether the VSWR is less than or equal to the threshold value for the matching state (step S104). In step S104, when the VSWR is less than or equal to the threshold value and the matching is achieved (Yes in step S104), the control circuit 506 starts transmitting power at a high power required for thawing from the high-frequency power amplifier 503 (step S106).

[0058] On the other hand, in processing step S104, when the VSWR is greater than or equal to the threshold value (No in step S104), the control circuit 506 notifies to change the position and height of the frozen food 8. As the means of notification, for example, the generation of sound by a sound generating device, the display of characters by a display device, etc. are used. The user confirms the notification content and changes the position and height of the frozen food 8 (step S105). In processing step S105, after changing and adjusting the position and height of the frozen food 8, the process returns to processing step S101 again, and the control circuit 506 resets the antenna tuner 2 and performs tuning again.

[0059] After power transmission is started in step S106, the control circuit 506 measures the temperature of the frozen food 8 using the temperature sensor 507, and determines whether the target temperature at which thawing ends has been reached (step S107). If the temperature of the frozen food 8 has reached the target temperature (Yes in step S107), the control circuit 506 notifies that the thawing of the frozen food 8 is completed, and ends the process (step S111).

[0060] If the temperature of the frozen food 8 has not reached the target temperature (No in step S107), the control circuit 506 measures the incident power and the reflected power from the directional coupler 505 (step S108).

[0061] The control circuit 506 calculates the VSWR (Voltage Standing Wave Ratio) indicating the matching state calculated from the incident power and the reflected power, and determines whether the VSWR is less than or equal to the threshold value for the matching state (step S109).

[0062] In step S109, when the VSWR is less than or equal to the threshold value and the matching is achieved (Yes in step S109), the control circuit 506 returns to step S106, and starts power transmission with high power required for thawing from the high-frequency power amplifier 503 (step S106).

[0063] On the other hand, in processing step S109, when the VSWR is greater than or equal to the threshold value (No in step S109), the control circuit 506 reduces the high-frequency power output from the high-frequency power amplifier 503 and adjusts the matching point with the antenna tuner 2 (step S110). Then, it returns to the process of step S104, and if the VSWR is less than or equal to the threshold value, it transmits the power required for thawing, and thaws the frozen food 8 again.

[0064] By measuring the voltage amplitude of the variable matching circuit input in this way, it is possible to detect the matching state, and thus it is possible to thaw the frozen food with relatively simple control.

[0065] With the above configuration, according to this embodiment, even if the dielectric constant of the frozen food 8 changes due to thawing, by adjusting the antenna tuner so that the reflected power is minimized, a high-frequency thawing machine with excellent heating efficiency can be obtained.

[0066] Furthermore, according to this embodiment, by adding a capacitor and an inductor that cancel out the parasitic components of the antenna tuner, the matching of the antenna tuner is improved. Therefore, it returns from the processing step S104 shown in FIG. 11 via the processing step S105 to the processing step S101, and the number of times power transmission stops once can be reduced. Thus, the frequency at which the matching is lost and the thawing time becomes long can be reduced.

[0067] Also, according to this embodiment, in addition to the configuration in which the first upper spiral electrode 6 and the second upper spiral electrode 7 are arranged point-symmetrically, similar spiral electrodes in a point-symmetric relationship with each other, namely the first lower spiral electrode 521 and the second lower spiral electrode 522, are also arranged at the lower part. Since the frozen food 8 is thawed by the electric fields generated above and below, uniform thawing is possible on both sides of the food, and even for thick foods, the electric field penetrates to the inside, enabling uniform thawing.

[0068] Furthermore, according to this embodiment, since the first and second spiral electrodes are set to slightly different lengths that resonate at the transmission frequency with the dielectric constants at the start and end of thawing of the food, respectively, the resonance frequency bandwidth is broadened, the convergence of the antenna tuner is improved, and the number of switching elements of the antenna tuner is reduced, enabling miniaturization and cost reduction of the circuit. Also, in this embodiment, since a high-frequency power amplifier 503 uses a plurality of relatively low-cost high-frequency amplifiers to obtain the large power required for thawing, cost reduction can be achieved.

Embodiment

[0069] FIG. 6 is a configuration diagram showing an outline of a high-frequency thawing device according to Embodiment 3 of the present invention. The high-frequency thawing device 300 is configured such that a transformer 601a (balun transformer) is connected between an antenna tuner 2, an upper flat electrode 4, and a lower flat electrode 5 connected to GND at a position other than the housing GND. In addition, the same reference numerals are assigned to the parts overlapping with the high-frequency thawing device of Embodiment 2 shown in FIG. 5, and the description thereof is omitted.

[0070] In Embodiment 3 shown in FIG. 6, compared with the high-frequency thawing device of Embodiment 2 shown in FIG. 5, the high-frequency power output from the antenna tuner 2 is converted into a balanced signal by the transformer 601a, and the points connected to the upper flat electrode 4 and the lower flat electrode 5 are different.

[0071] In the configuration of the high-frequency thawing device according to Embodiment 2 of FIG. 5, the electric field generated by the upper spiral electrode causes an ineffective high-frequency current that does not contribute to thawing to flow due to capacitive coupling with the housing 3, which results in a loss and a decrease in heating efficiency. In addition, in the case of thick food materials, there is a problem that the electric field cannot reach the center of the food material because it combines with the side surface of the housing 3, and thawing of the center part cannot be promoted. In the high-frequency thawing device 300 according to Embodiment 3, a balanced electric field is applied by the first upper spiral electrode 6, the second upper spiral electrode 7, the first lower spiral electrode 521, and the second lower spiral electrode 522. Therefore, the loss due to capacitive coupling with the side surface of the housing 3 is reduced, and the electric field coupling in the vertical direction is strengthened. For this reason, according to the configuration of the present embodiment, since the electric field passes through the center part, even thick food materials can be homogeneously thawed not only on the upper and lower surfaces but also in the cross-sectional direction.

[0072] Incidentally, the inter-electrode impedance between the upper flat electrode 4 and the lower flat electrode 5 is a relatively small value of about 30 Ω or less with respect to the source impedance of 50 Ω of the high-frequency power amplifier 503. In other words, the transformer 601a converts to an impedance lower than the source impedance of the RF signal source 501. Therefore, in addition to the transformer 601a which is a transmission line transformer with an impedance conversion ratio of 1:1, by using the transmission line transformer 602b with an impedance conversion ratio of 4:1, the transmission line transformer 602c of a trifilar winding with an impedance conversion ratio of 9:4, and the transformer 602d whose turns ratio can be arbitrarily changed, the matching of the antenna tuner 2 is further improved.

[0073] The flow from the start to the end of thawing of the frozen food 8 is the same as that in FIG. 11 described in Example 2.

Example

[0074] FIG. 7 is a configuration diagram showing an outline of a high-frequency thawing device according to Example 4 of the present invention. In the high-frequency thawing device 400, an electric field diffusion plate 701 (upper electric field diffusion plate) for equalizing the electric field generated from the spiral electrodes shown in FIGS. 2B and 2C is disposed between the upper spiral electrodes (the first upper spiral electrode 6, the second upper spiral electrode 7) and the frozen food 8. Similarly, an electric field diffusion plate 702 (lower electric field diffusion plate) is disposed between the lower spiral electrodes (the first lower spiral electrode 521, the second lower spiral electrode 522) and the frozen food 8. In addition, parts overlapping with the high-frequency thawing device of Example 3 shown in FIG. 6 are denoted by the same reference numerals and the description thereof is omitted. The electric field diffusion plate 701 and the upper spiral electrodes (the first upper spiral electrode 6, the second upper spiral electrode 7) are located below the upper flat electrode 4, and the electric field diffusion plate 702 and the lower spiral electrodes (the first lower spiral electrode 521, the second lower spiral electrode 522) are located above the lower flat electrode 5. The configurations of the electric field diffusion plates 701 and 702 are the same as those of the electric field diffusion plate 9.

[0075] In Example 4 shown in FIG. 7, compared with the high-frequency thawing device of Example 3 shown in FIG. 6, the electric field diffusion plates 701 and 702 are respectively arranged between the upper spiral electrode and the food material and between the food material and the lower spiral electrode. This is different. As a result, the central electrode plate 202 of the electric field diffusion plate shown in FIG. 2B is combined with the central part of the high electric field spiral electrode, and the high electric field in the central part is made uniform on the outer peripheral part of the food material by the metal plates on the outer peripheral part connected to the central electrode plate 202 (the frame parts 206 and 207 in FIG. 2B). Therefore, the electric field generated from the spiral electrode can be made uniform.

[0076] As described above, according to this example, in addition to arranging the first spiral electrode and the second spiral electrode point-symmetrically and in pairs, an electric field diffusion plate is used, so that the homogenization of the electric field can be further achieved.

[0077] 〔An example of analysis results〕 Here, the analysis results of the heat generation distribution on the surface of the food material by dielectric heating according to each of the above-described examples will be described with reference to FIGS. 8A, 8B, and 8C. As an example, the analysis results regarding each example of the present invention show those of Example 2.

[0078] FIG. 8A is a diagram showing the analysis results when dielectric heating is performed by the high-frequency heating device shown in Patent Document 1 (prior art). In FIG. 8A, a configuration is adopted in which spiral electrodes having a length of λ / 4 are arranged above and below the flat electrode. FIG. 8B is a diagram showing the analysis results when dielectric heating is performed by the high-frequency thawing device of Example 2 shown in FIG. 5. FIG. 8C is a diagram showing the analysis results when an electric field diffusion plate is added to the configuration of Example 2. That is, FIG. 8C shows a configuration in which the electric field diffusion plate 9 is arranged on the lower spiral electrode having a length of λ / 4 shown in FIG. 2B, and is also arranged opposite to the upper flat electrode 4 side, and dielectric heating is performed by a high-frequency thawing device having a configuration in which electric field diffusion plates are arranged on the upper and lower spiral electrodes.

[0079] The size of the spiral electrode was set to approximately 25 cm × 27 cm, and the analysis was carried out on a simulated food material of 20 cm × 20 cm × 5 cm in a frozen state at -20°C. The frequency was 40.68 MHz, and the distance between the spiral electrodes was 8 cm. Also, as the electric field diffusion plate of the high-frequency thawing device analyzed in Fig. 8C, one with an outer shape of 25 cm × 22 cm, a thickness of 1 cm, and a central electrode plate with a size of 6 cm × 6 cm was used.

[0080] In the dielectric heating according to the prior art of Fig. 8A, it can be seen that the heat generation on the surface of the food material progresses along the shape of the spiral electrode, and in particular, it is likely to have uneven heating along the spiral electrode in the central part where the electric field is high. On the other hand, in Example 2 of the high-frequency thawing device of Fig. 8B, since the first and second spiral electrodes are arranged point-symmetrically and the electric field generated from the spiral electrodes is homogenized, it can be seen that the heat generation on the surface of the food material is also homogenized. In addition, in the spiral electrode, since the electric field is high in the central part and becomes lower towards the outer periphery, it can be seen that the heat generation of the food material also decreases towards the end. This is an effective configuration for suppressing the uneven heating generated at the end of the food material due to the concentration of the electric field by the end effect. Therefore, by adopting the configuration of the first and second spiral electrodes, it can be seen that the uneven heating in the central part can be reduced and the uneven heating generated at the end of the food material can also be reduced, enabling uniform thawing. Also, in the configuration using the electric field diffusion plate of Fig. 8C, since the heat generation due to the high electric field in the central part is reduced, the uneven heating is suppressed compared to the prior art. Furthermore, by using the electric field diffusion plate in the configuration of the first and second spiral electrodes, the heat generation in the central part is suppressed, making more uniform thawing possible.

[0081] FIG. 9 is a diagram showing the relationship between the frequency and the return loss in the high-frequency thawing device of Example 2. In FIG. 9, in the high-frequency thawing device of Example 2 shown in FIG. 5, the first upper spiral electrode 6 and the first lower spiral electrode 521 are set to lengths that resonate with the transmission frequency (40.68 MHz in this example) at the dielectric constant at the start of thawing of the frozen food 8, and the lengths of the second upper spiral electrode 7 and the second lower spiral electrode 522 are set to lengths that resonate at the dielectric constant at the end of thawing of the frozen food 8, thereby showing the result of analyzing the effect of broadening the resonance frequency band between the spiral electrode and the food. For comparison, the thawing device of the prior art shown in FIG. 8A was also analyzed. The constants of the spiral electrodes and the like used in the analysis were the same as those in the analysis of the heat generation amount on the food surface shown in FIGS. 8A and 8B. In the analysis of the high-frequency thawing device of Example 2 shown in FIG. 5, the lengths of the first and second spiral electrodes in the upper and lower parts were analyzed with a difference of about 6 cm.

[0082] The horizontal axis in FIG. 9 is the frequency when it changes from 30 MHz to 50 MHz, and the vertical axis is the return loss (reflection attenuation amount). The smaller the value, the better the matching. If it is 0 dB, it is total reflection with no matching at all. As shown in FIG. 9, in Example 2, since the 3 dB bandwidth is widened by about 1.45 times, the convergence of the antenna tuner can be improved and the number of variable elements can be reduced, so that a small and low-cost high-frequency thawing machine can be obtained.

[0083] FIG. 10 is a circuit diagram showing another example of the configuration of the antenna tuner. FIG. 10 shows the circuit configuration including the component arrangement of the antenna tuner used in Example 2 shown in FIG. 5, Example 3 shown in FIG. 6, and Example 4 shown in FIG. 7. In the configuration shown in FIG. 10, compared with the antenna tuner circuit shown in FIG. 4A, the constants of the parasitic inductor 1001, the parasitic capacitance 1002, the canceling capacitance 1003, and the canceling inductor 1004 are different from those in FIG. 6, and the directional coupler 505 and the control circuit 506 are built in the antenna tuner 2. Other parts overlapping with the circuit of the antenna tuner 2 shown in FIG. 4A are given the same numbers and the description is omitted.

[0084] FIG. 10 shows a loop arrangement with respect to FIG. 4A such that the leads of inductors 411, 422, 423 and relays 411, 412, 413 connected in series between the antenna input / output terminals are shortened. For this reason, the value of parasitic inductor 1001 becomes smaller than that in FIG. 4A, so the cancellation capacitance 1003 may be increased or becomes unnecessary, and the convergence of the antenna tuner due to the parasitic inductor component can be improved.

[0085] Also, by arranging capacitors 424, 426 connected in parallel between the antenna input / output terminals and branching capacitors 425, 427 into two in parallel, capacitor 427, which is the farthest from switching relay 414, has a shorter distance from the relay due to the branching arrangement. Therefore, the value of equivalent parasitic capacitance 1002 becomes smaller, so the cancellation inductor 1004 may be increased or becomes unnecessary, and the convergence of the antenna tuner due to the parasitic capacitance component can be improved. Furthermore, since the connection distance between switching relay 414 and the antenna input / output can also be shortened, the parasitic inductor component due to this lead can also be reduced.

[0086] With the above configuration, by incorporating the directional coupler 505 and the control circuit 506 into the antenna tuner 2, the circuit can be miniaturized. At the same time, by reducing the parasitic inductors and parasitic capacitances, the convergence is improved, and by reducing the number of switching elements, cost reduction can be achieved.

Embodiment

[0087] FIG. 12A is a configuration diagram showing an example of the outline of a high-frequency thawing device according to Embodiment 5 of the present invention. The high-frequency thawing device in FIG. 12A is composed of a frozen food 8, a high-frequency power supply 1201, a flat electrode 1202, and a spiral antenna 1203. The high-frequency power supply 1201 in the figure is a power supply that supplies relatively high-frequency power from several 100 MHz to about 2.4 GHz, and supplies high-frequency power to the spiral antenna 1203 via the flat electrode 1202. The spiral antenna 1203 has a length that is an integer multiple of 1 / 4 of the wavelength λ of the power transmission frequency from the high-frequency power supply, is provided on the flat electrode 1202, has its outer peripheral end connected to the flat electrode 1202, and its inner peripheral end is in an open state. Since the spiral antenna 1203 efficiently radiates electromagnetic waves due to resonance at λ / 4 wavelength, it is possible to thaw the frozen food 8 placed on the spiral antenna.

[0088] With the above configuration, in addition to the electric field generated from the spiral antenna 1203, a high-frequency thawing device that can also be thawed by electromagnetic waves can be obtained.

[0089] FIG. 12B is a schematic configuration diagram showing another example of the high-frequency thawing device according to Embodiment 5 of the present invention. The high-frequency thawing device in FIG. 12B is different in that a plurality of antenna pairs in which a first spiral antenna 1204 and a second spiral antenna 1205 are arranged point-symmetrically are arranged on the flat electrode 1202 as compared with FIG. 12A. For other parts overlapping with FIG. 12A, the same reference numerals are given and the description is omitted.

[0090] The first spiral antenna 1204 and the second spiral antenna 1205 are arranged point-symmetrically and at equal intervals so that their spirals do not overlap each other.

[0091] In FIG. 12B, in addition to obtaining the same effect as the high-frequency thawing device shown in FIG. 12A, the first spiral antenna 1204 and the second spiral antenna 1205 form a self-complementary antenna having a constant antenna impedance with respect to the feeding frequency, and since they are excellent in broadband and matching, a matching circuit such as an antenna tuner is not required, and it is also possible to thaw a relatively large foodstuff by arranging a plurality of spiral pairs on the flat electrode 1202.

[0092] FIG. 12C is a schematic configuration diagram showing still another example of the high-frequency thawing device according to Embodiment 5 of the present invention. The high-frequency thawing device of FIG. 12C includes a semiconductor wafer 1206, a flat electrode 1207, and an inverted L-shaped antenna 1208. The inverted L-shaped antenna 1208 includes a portion horizontally arranged along the semiconductor wafer 1206 and a portion bent downward from this horizontal portion.

[0093] Further, the high-frequency power supply 1201 is a power supply that supplies high-frequency power of several GHz. A flat electrode 1207 is arranged on the semiconductor wafer 1206, and high-frequency power is supplied to the inverted L-shaped antenna 1208 via the flat electrode 1207. Note that the inverted L-shaped antenna 1208 has a length that is an integer multiple of 1 / 4 of the wavelength λ of the power transmission frequency from the high-frequency power supply, and a plurality of them are arranged on the flat electrode 1207. Further, a plurality of flat electrodes 1207 are arranged on the semiconductor wafer 1206 at the same wiring distance as the high-frequency power supply 1201. Note that when the power transmission frequency becomes a high frequency of GHz band or higher, the wavelength becomes short and it becomes difficult to maintain a spiral shape. For this reason, it is necessary to arrange it as an inverted L-shaped antenna and also shorten the wiring length between the flat electrodes 1207, and thus the configuration is formed on the semiconductor wafer 1206.

[0094] With the above configuration, according to this embodiment, it is possible to obtain a high-frequency thawing device capable of efficiently thawing by radiated electromagnetic waves even at a high frequency of GHz band or higher.

[0095] Note that the present invention is not limited to the above-described embodiments, and various modifications are included. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Also, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. Further, it is possible to add, delete, or replace other configurations for a part of the configuration of each embodiment.

Description of Reference Numerals

[0096] 1… High-frequency power supply, 2… Antenna tuner, 3… Housing, 4… Upper flat electrode, 5… Lower flat electrode, 6… First upper spiral electrode, 7… Second upper spiral electrode, 8… Frozen food, 9… Electric field diffusion plate, 10… Power supply point, 100… High-frequency thawing device, 200… High-frequency thawing device, 201… Lower spiral electrode, 202… Central electrode plate, 203… Notch, 204… Notch, 205… Coupling capacitance, 206… Frame part, 207… Frame part, 208… Connection part, 300… High-frequency thawing device, 400… High-frequency thawing device, 401… Tuner input terminal, 402… Tuner output terminal, 403… Control terminal, 411… Relay, 412… Relay, 413… Relay, 414… Relay, 415… Relay, 416… Relay, 417… Relay, 418… Relay, 421… Inductor, 422… Inductor, 423… Inductor, 424… Capacitor, 425… Capacitor, 426… Capacitor, 427… Capacitor, 431… Parasitic inductor, 432… Canceling capacitance, 433… Parasitic capacitance, 434… Inductor, 441… Variable capacitance capacitor (varicon), 442… Inductor, 443… Variable capacitance capacitor (varicon), 501… Signal source, 502… Attenuator, 503… High-frequency power amplifier, 504… Power supply circuit, 505… Directional coupler, 506… Control circuit, 511… Distribution circuit, 512… High-frequency amplifier, 513… Combining circuit, 521… First lower spiral electrode, 522… Second lower spiral electrode, 601a… Transformer, 602b… Transmission line transformer, 602c… Transmission line transformer, 602d… Transformer, 701… Electric field diffusion plate, 702… Electric field diffusion plate, 1001… Parasitic inductor, 1002… Parasitic capacitance, 1003… Canceling capacitance, 1004… Inductor, 1201… High-frequency power supply, 1202… Flat electrode, 1203… Spiral antenna, 1204… First spiral antenna, 1205… Second spiral antenna, 1206… Semiconductor wafer, 1207… Flat electrode, 1208… Inverted L-shaped antenna, 1301… High-frequency power supply, 1302… Matching circuit, 1303… Chamber, 1304… Coil, 1305… Object to be processed, 1306… Lower electrode, 1307… Insulator, 1308… Second high-frequency power supply

Claims

1. An upper flat electrode and a lower flat electrode disposed opposite to each other vertically within a housing, an upper spiral electrode disposed below the upper flat electrode and connected to the upper flat electrode, and a high-frequency power supply having one end connected to the upper flat electrode and the other end connected to the lower flat electrode for supplying high-frequency power. The upper spiral electrode consists of a first upper spiral electrode and a second upper spiral electrode, wherein the length of the upper spiral electrode is an integer multiple of 1 / 4 of the wavelength λ of the power transmission frequency from the high-frequency power supply, the outer peripheral end is connected to the upper flat electrode, and the inner peripheral end is open. The first upper spiral electrode and the second upper spiral electrode are arranged in a point-symmetrical and equally spaced manner so that their spirals do not overlap. A high-frequency thawing device characterized by dielectrically heating an object to be heated disposed between the first upper spiral electrode, the second upper spiral electrode, and the lower flat electrode.

2. In the high-frequency thawing device according to Claim 1, it is provided with a lower spiral electrode disposed above the lower flat electrode and connected to the lower flat electrode. The lower spiral electrode is characterized in that the length of the lower spiral electrode is an integer multiple of 1 / 4 of the wavelength λ of the power transmission frequency from the high-frequency power supply, the outer peripheral end is connected to the lower flat electrode, and the inner peripheral end is open.

3. In the high-frequency thawing device according to Claim 1, it is provided with a lower spiral electrode disposed above the lower flat electrode and connected to the lower flat electrode. The lower spiral electrode consists of a first lower spiral electrode and a second lower spiral electrode, wherein the length of the lower spiral electrode is an integer multiple of 1 / 4 of the wavelength λ of the power transmission frequency from the high-frequency power supply, the outer peripheral end is connected to the lower flat electrode, and the inner peripheral end is open. The first lower spiral electrode and the second lower spiral electrode are arranged in a point-symmetrical and equally spaced manner so that their spirals do not overlap.

4. In the high-frequency thawing device according to Claim 3, An upper electric field diffusion plate that capacitively couples with the central portion of the upper spiral electrode is disposed between the object to be heated and the upper spiral electrode.

5. In the high-frequency thawing device according to Claim 4, A high-frequency thawing device, characterized in that a lower electric field diffusion plate that capacitively couples with the central part of the lower spiral electrode is arranged between the object to be heated and the lower spiral electrode.

6. In the high-frequency thawing device according to claim 5, the upper electric field diffusion plate and the lower electric field diffusion plate are composed of two frame parts formed in a U shape with a gap provided on the open side facing each other, a connecting part connecting the central parts of the two frame parts, and a central electrode plate formed at the central position of the connecting part. A high-frequency thawing device characterized by this.

7. In the high-frequency thawing device according to any one of claims 1 to 6, a high-frequency thawing device, characterized in that an adjustment circuit for adjusting impedance matching with the high-frequency power supply is provided between the high-frequency power supply and the upper flat electrode.

8. In the high-frequency thawing device according to claim 7, a high-frequency thawing device, characterized by comprising a directional coupler that is arranged between the high-frequency power supply and the adjustment circuit and measures the incident power and reflected power input to the adjustment circuit, and a control circuit that inputs the result measured by the directional coupler and controls the adjustment circuit so that the reflected power becomes small.

9. In the high-frequency thawing device according to claim 7, a high-frequency thawing device, characterized in that the adjustment circuit is an antenna tuner configured to switch the capacitance value and inductance value of a capacitor by a relay.

10. In the high-frequency thawing device according to claim 9, the antenna tuner is provided with a first cancellation element that is connected in series to a parasitic inductance component generated by the wiring routing of an inductor connected in series between the input and output terminals of the antenna tuner and resonates at the transmission frequency of the high-frequency power supply, and a second cancellation element that is connected in parallel to a parasitic capacitance component generated by the wiring routing of an inductor connected in parallel between the input and output terminals of the antenna tuner and resonates at the transmission frequency of the high-frequency power supply. A high-frequency thawing device characterized by this.

11. In the high-frequency thawing device according to claim 3, the lower flat electrode is connected to the ground, an adjustment circuit for adjusting impedance matching with the high-frequency power supply is provided between the high-frequency power supply and the upper flat electrode, a high-frequency thawing device, characterized in that baluns for converting the power output from the adjustment circuit into a balanced signal are provided between the upper flat electrode and the adjustment circuit and between the lower flat electrode and the ground.

12. In the high-frequency thawing device according to claim 11, the balun converts to an impedance lower than the signal source impedance of the high-frequency power supply, and the high-frequency thawing device is characterized by this.

13. A high-frequency thawing device comprising a spiral antenna provided on a flat electrode and a high-frequency power supply that supplies high-frequency power to the spiral antenna via the flat electrode, wherein the spiral antenna has a length that is an integer multiple of 1 / 4 of the wavelength λ of the transmission frequency from the high-frequency power supply, the outer peripheral end is connected to the flat electrode, the inner peripheral end is in an open state, and the object to be heated on the flat electrode is heated.

14. A high-frequency thawing device comprising a spiral antenna provided on a flat electrode and a high-frequency power supply that supplies high-frequency power to the spiral antenna via the flat electrode, wherein the spiral antenna is composed of a first spiral antenna and a second spiral antenna having a length that is an integer multiple of 1 / 4 of the wavelength λ of the transmission frequency from the high-frequency power supply, the outer peripheral end is connected to the flat electrode, and the inner peripheral end is open, the first spiral antenna and the second spiral antenna are arranged point-symmetrically and at equal intervals so that their spirals do not overlap, and the object to be heated arranged on the spiral antenna is heated.

15. In the high-frequency thawing device according to claim 14, the high-frequency thawing device is characterized by including a plurality of the spiral antennas.

16. A high-frequency thawing device comprising an inverted L-shaped antenna provided on a flat electrode arranged on a semiconductor wafer and a high-frequency power supply that supplies high-frequency power to the inverted L-shaped antenna via the flat electrode, wherein the inverted L-shaped antenna has a length that is an integer multiple of 1 / 4 of the wavelength λ of the transmission frequency from the high-frequency power supply, and the object to be heated on the flat electrode is heated.

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