High-frequency thawing device

Abstract

The invention provides a high-frequency thawing device which realizes miniaturization and low cost of a circuit and can perform homogeneous thawing. The high-frequency thawing device (100) is provided with an upper plate electrode (4) and a lower plate electrode (5) which are connected with a high-frequency power supply (1). And the upper plate electrode (4) is connected with the upper spiral electrode. The length of the upper spiral electrode is an integral multiple of 1 / 4 of the wavelength (lambda) of the power transmission frequency from the high-frequency power source (1), and the upper spiral electrode is composed of a first upper spiral electrode (6) and a second upper spiral electrode (7), the outer peripheral ends of which are connected to the upper plate electrode (4) and the inner peripheral ends of which are open. The first upper spiral electrode (6) and the second upper spiral electrode (7) are arranged at equal intervals in a point symmetry manner so as not to overlap each other in a spiral manner, and a frozen food material arranged between the first upper spiral electrode (6) and the lower plate electrode (5) and between the second upper spiral electrode (7) and the lower plate electrode (5) is dielectrically heated.

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, it is sometimes necessary to thaw frozen food materials to process food. As one type of thawing machine used in food processing factories and the like, there is known a high-frequency thawing device that applies a high-frequency electric field in the MHz band to frozen food disposed between opposing electrodes and thaws the frozen food by dielectric heating.

[0003] High-frequency dielectric heating is a technique of applying a high-frequency voltage to an object to be heated, i.e., a dielectric, and heating the object to be heated from the inside by self-heating (dielectric loss) caused by vibrations of polar molecules constituting the object to be heated. In dielectric heating using microwaves (GHz band) generated by a microwave oven using an induction cooker, the difference in heat generation between ice and water is large, so the melted part of the food surface layer significantly generates heat, resulting in uneven heating. However, in high-frequency dielectric heating using a frequency band lower than microwaves, the penetration depth of energy is deeper than that of microwaves, and in addition, the difference in heat generation between ice and water is small. Therefore, it is generally known to have the advantage of being less likely to cause uneven heating.

[0004] As an existing technique of 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 having the following structure: when heating an object to be heated placed between electrodes with high-frequency power in the MHz band from a high-frequency power supply, an impedance change accompanying the temperature rise of the object to be heated is detected by a reflected power detection unit, and the constants of a matching circuit composed of a variable inductor and a capacitor are switched to maintain the 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 dry etching and thin film formation of semiconductors. Its structure is as Figure 13 shown. Figure 13 is a schematic diagram of the high-frequency power supply application device related to the existing technique.

[0006] As Figure 13 shown, 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, an object to be processed 1305, a lower electrode 1306, and an insulator 1307 are disposed in the chamber 1303.

[0007] The high-frequency signal (RF signal) in the MHz band from the high-frequency power supply 1301 passes through the matching circuit 1302 to achieve impedance matching for the object 1305 between the coil 1304 and the lower electrode 1306, which is approximately an integer multiple of 1 / 4 of the wavelength of the high-frequency power. As a result, standing waves that are integer multiples of 1 / 4 wavelength are generated in the coil 1304 with a large voltage amplitude. A high electric field is applied to the object 1305 through this voltage amplitude, and plasma processing is performed by efficiently transmitting high-frequency power. Also, through the second high-frequency power supply 1308, a high-frequency voltage is applied to the object 1305 via the lower electrode 1306 disposed on the insulator 1307, and thus power can also be efficiently transmitted to the object 1305.

[0008] Prior Art Documents

[0009] Patent Document 1: Japanese Patent Laid-Open No. 2005-56781

[0010] Patent Document 2: Japanese Patent Laid-Open No. 9-293600

[0011] When applying the high-frequency power application device of Patent Document 2 ( Figure 13 ) to the high-frequency heating device of Patent Document 1 for thawing food materials by dielectric heating, power of about several hundred watts is required. However, in this case, a voltage of more than several thousand volts is generated in the matching circuit in the same way as the high-frequency heating device of Patent Document 1. When heating the object to be heated disposed between the parallel plate electrodes shown in Patent Document 1, an electric field is generated substantially uniformly on the electrode surfaces of the parallel plate electrodes. However, in the case of the coil of Patent Document 2, a higher electric field is generated near the winding. Therefore, in thawing by dielectric heating using a coil, the electric field in the part along the winding of the coil becomes higher. Therefore, on the food material surface, a difference in the electric field applied to the food material occurs between the part directly below the coil and the part between the windings of the coil. In addition, since standing waves are generated in the coil, there is a problem that uneven heating is likely to occur along the winding of the coil with the center directly below the part with the highest voltage amplitude, and homogeneous heating cannot be performed.

[0012] Furthermore, when trying to thaw a larger food material and increase the coil (helical electrode), due to the resonance of the standing waves generated on the coil, it is not easy to increase the coil length. Therefore, the coil pitch is enlarged, the potential difference between the coil windings and the wire becomes larger, and thus the uneven heating becomes further larger. Therefore, it is difficult to make the electrode larger.

[0013] In addition, as another issue, since resonance of a coil is used to generate a high electric field, a voltage of over 1000 V is generated at both ends of the coil. Therefore, there is an issue that the matching circuit for matching with the coil needs to have a high withstand voltage, resulting in a high cost.

[0014] Furthermore, when thawing food ingredients, the dielectric constant of the food ingredients changes in the direction of increasing, and accordingly, the capacitance between the wirings of the coil increases, and thus the resonance frequency of the coil changes. Therefore, the matching circuit for achieving impedance matching for this resonance frequency deviation requires a wide adjustment range. As a result, the number of switching elements of inductors and capacitors for matching increases, the shape becomes larger, and parasitic inductor and capacitance components increase. Therefore, there is an issue that it is difficult to achieve matching. Summary of the Invention

[0015] An object of the present invention is to solve the above issues and provide a high-frequency thawing device that achieves miniaturization and low cost of the circuit and can perform uniform thawing.

[0016] To achieve the above object, as an example, according to the present invention, it is characterized by comprising: an upper flat electrode and a lower flat electrode that are disposed opposite to each other vertically within a housing; an upper spiral electrode that is disposed below the upper flat electrode and is connected to the upper flat electrode; and a high-frequency power supply that is connected to the upper flat electrode on one side and to the lower flat electrode on the other side to supply high-frequency power. 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 upper spiral electrode is composed of a first upper spiral electrode and a second upper spiral electrode whose outer peripheral ends are connected to the upper flat electrode and whose inner peripheral ends are open. The first upper spiral electrode and the second upper spiral electrode are arranged point-symmetrically and at equal intervals such that their spirals do not overlap, and dielectric heating is performed on an object to be heated disposed between the first upper spiral electrode, the second upper spiral electrode, and the lower flat electrode.

[0017] The effects of the present invention are as follows.

[0018] According to the present invention, it is possible to provide a high-frequency thawing device that achieves miniaturization and low cost of the circuit and can perform uniform thawing. Brief Description of the Drawings

[0019] Figure 1A is a schematic structural diagram showing a high-frequency thawing device according to Embodiment 1 of the present invention.

[0020] Figure 1B is a schematic diagram showing a cross-sectional structure of the high-frequency thawing device according to Embodiment 1 of the present invention.

[0021] Figure 1CThis is a diagram showing an example of the configuration of the spiral electrode in Embodiment 1 of the present invention.

[0022] Figure 2A This is a diagram showing Figure 1A the distribution of the electric field caused by the standing wave generated on the λ / 4 spiral electrode and the current flowing in the spiral electrode in the high-frequency thawing device.

[0023] Figure 2B This is an electrode structure diagram for explaining the operation of the electric field diffusion plate.

[0024] Figure 2C This is a cross-sectional structure diagram for explaining the operation of the electric field diffusion plate.

[0025] Figure 3A This 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 in Embodiment 1 of the present invention.

[0026] Figure 3B This 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.

[0027] Figure 4A This is a diagram showing Figure 1A an example of the structure of the antenna tuner 2 of the high-frequency thawing device shown.

[0028] Figure 4B This is a diagram showing another example of the antenna tuner.

[0029] Figure 5 This is a schematic structure diagram of the high-frequency thawing device in Embodiment 2 of the present invention.

[0030] Figure 6 This is a schematic structure diagram of the high-frequency thawing device in Embodiment 3 of the present invention.

[0031] Figure 7 This is a schematic structure diagram of the high-frequency thawing device in Embodiment 4 of the present invention.

[0032] Figure 8A This 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).

[0033] Figure 8B This is a diagram showing the analysis results when dielectric heating is performed by the high-frequency thawing device in Embodiment 2 of the present invention.

[0034] Figure 8C This is a diagram showing the analysis results when an electric field diffusion plate is added to the structure of Embodiment 2.

[0035] Figure 9It is a diagram showing the relationship between frequency and return loss in the high-frequency thawing device of Example 2.

[0036] Figure 10 It is a circuit diagram showing another example of the structure of the antenna tuner.

[0037] Figure 11 It is a flowchart showing the process from the start to the end of dielectric heating in the high-frequency thawing device of Example 2 of the present invention.

[0038] Figure 12A It is a structural diagram showing a schematic example of the high-frequency thawing device of Example 5 of the present invention.

[0039] Figure 12B It is a schematic structural diagram showing another example of the high-frequency thawing device of Example 5 of the present invention.

[0040] Figure 12C It is a schematic structural diagram showing yet another example of the high-frequency thawing device of Example 5 of the present invention.

[0041] Figure 13 It is a schematic diagram of a high-frequency power supply application device related to the prior art.

[0042] In the figure: 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 - cut portion, 204 - cut portion, 205 - coupling capacitor, 206 - frame portion, 207 - frame portion, 208 - connecting portion, 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 capacitor, 433 - parasitic capacitor, 434 - inductor, 441 - variable capacitance capacitor (variable capacitor), 442 - inductor, 443 - variable capacitance capacitor (variable capacitor), 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 - synthesis 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 capacitor, 1003 - canceled capacitor, 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. Detailed implementation manners

[0043] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The principle of the high-frequency thawing device according to the embodiments of the present invention is high-frequency dielectric heating, which can be widely applied to the heating scenarios of objects to be heated. The following embodiments will describe the case specifically for thawing. In the figure, when observed from the rear where the user uses, as indicated by the arrow, it is defined as up and down, front and back, left and right.

[0044] In addition, in the embodiments of the present invention, it is contemplated to install high-frequency thawing devices in the backyards of convenience stores, supermarkets and other retail stores, restaurants, etc., to thaw frozen foods and ingredients such as boxed lunches, side dishes, and meats stored according to the number of customers entering the store, and in the case of arranging the thawed ingredients as fresh chilled products on the display shelves in the store, cooking the thawed ingredients and providing them to customers, etc.

[0045] However, the following description shows specific examples of the content of the present invention. The present invention is not limited to these descriptions, and those skilled in the art can make various changes and modifications within the scope of the technical idea disclosed in this specification.

[0046] [Embodiment 1]

[0047] Figure 1A It is a schematic structural diagram showing a high-frequency thawing device according to Embodiment 1 of the present invention. The high-frequency thawing device 100 is composed of a high-frequency power supply 1 that outputs MHz frequency bands such as the ISM band (Industrial, Scientific and Medical band, ISM: 13.56 MHz, 27.12 MHz, 40.68 MHz, etc.), 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 contour of the high-frequency thawing device 100. The upper flat electrode 4 and the lower flat electrode 5 are disposed opposite to each other in the vertical direction within the housing 3. The frozen food 8 (object to be heated) is disposed 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 through 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).

[0048] One of the high-frequency power supplies 1 is connected to the upper flat electrode 4 via the antenna tuner 2, and the other of the high-frequency power supplies 1 is connected to the lower flat electrode 5. In addition, the lower flat electrode 5 is connected to the housing 3. The housing 3 becomes frame grounding (FG). The antenna tuner 2 adjusts the constants to adjust the impedance matching with the upper flat electrode 4.

[0049] In addition, Figure 1B is a schematic diagram showing the cross-sectional structure of the high-frequency thawing device according to Embodiment 1 of the present invention, 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 reference numerals are assigned to the same parts as Figure 1A the same, and these figures are used to explain the operation.

[0050] 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 disposed below the upper flat electrode 4 (on the side facing the lower flat electrode 5), and have a length that is an integer multiple of 1 / 4 of the wavelength λ of the power 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 at equal intervals and point-symmetrically with respect to each other in such a way that their spirals do not overlap. In addition, the first upper spiral electrode 6 and the second upper spiral electrode 7 are formed by laminating copper plates and are disposed about 15 mm away from the upper flat electrode 4 downward.

[0051] By applying high-frequency power in the MHz band from the high-frequency power supply 1 between the upper flat electrode 4 and the lower flat electrode 5 connected to the housing 3 GND (ground), an electric field is generated within the flat electrodes. 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 standing waves are generated. At this time, since the length of the spiral electrode is an integer multiple of 1 / 4 of the wavelength λ of the power transmission frequency of the high-frequency power supply 1, the outer peripheral end of the spiral electrode becomes the minimum amplitude, and the inner peripheral end becomes the maximum amplitude, and the electric field is concentrated at the central part of the electrode.

[0052] Furthermore, as Figure 1C shown, since it has a point-symmetric structure in which the second upper spiral electrode 7 is disposed between the winding pitches of the first upper spiral electrode 6, the pitch of the spiral electrodes is equivalently 1 / 2, and the concentration of the electric field 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.

[0053] In addition, Figure 1C the power supply point 10 shown represents the connection point between the antenna tuner 2 and the upper flat electrode 4. By connecting at a distance equal to the short-circuit points of the first upper spiral electrode 6 and the second upper spiral electrode 7 with the upper flat electrode 4 respectively, the symmetry between the first upper spiral electrode 6 and the second upper spiral electrode 7 can be further maintained.

[0054] In addition, Figure 1C the current Ia flowing in the first upper spiral electrode 6 and the current Ib flowing in the second upper spiral electrode 7 shown are in the same direction and have substantially equal magnitudes, so the interference between the spiral electrodes is small, and it becomes a structure in which their effects can be ignored. If an example of the design constants of the spiral electrodes shown in Figure 1C is given, the pattern width is 1 cm, the pitch 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.

[0055] Here, Figure 2A the dielectric heating principle of this embodiment is described. In addition, for parts Figure 1A repeated with Figure 2A the same reference numerals are assigned and the description is omitted. Figure 1A FIG. is a diagram showing the distribution of the electric field caused by the standing wave generated on the λ / 4 helical electrode and the current flowing in the helical electrode in the high-frequency thawing device of

[0056] In addition, in Figure 2A , the structure is such that the lower helical electrode 201 is connected to the lower flat electrode 5. However, the same applies to the upper flat electrode 4 side. Furthermore, by connecting helical electrodes to both the upper and lower flat electrodes, the electric field concentration effect can be further obtained. At this time, with respect to the current flowing in the helical electrode, the magnetic fluxes generated in the winding directions of the upper and lower helical electrodes may be in the same direction and in opposite directions. The equivalent λ / 4 lengths are different when the magnetic fluxes are in the same direction and in opposite directions. For example, when the winding directions of the upper and lower helical electrodes are opposite when viewed from above, the generated magnetic fluxes are in the same direction and are strengthened, and the equivalent inductance of the helical electrode increases. Therefore, the mutual coupling amount is slightly reduced by shortening the upper and lower helical electrodes. On the other hand, when the winding directions of the upper and lower helical electrodes are the same when viewed from above, the magnetic fluxes are in opposite directions and the equivalent inductance decreases. Therefore, the length of the helical electrode needs to be increased to increase the mutual coupling amount.

[0057] Figure 2B , Figure 2C FIG. is a diagram showing the operation of a metal plate, i.e., an electric field diffusion plate, arranged to homogenize the electric field from the helical electrode between the helical electrode and the frozen food material, which is another unit that symmetrically arranges two helical electrodes as points for homogeneous thawing. Figure 2B FIG. is an electrode structure diagram for explaining the operation of the electric field diffusion plate. Figure 2C FIG. is a cross-sectional structure diagram for explaining the operation of the electric field diffusion plate.

[0058] In these figures, the electric field diffusion plate 9 is composed of the central electrode plate 202, cutout portions 203, 204, and coupling capacitor 205 of the electric field diffusion plate 9. For other parts repeated with FIG. 1, the same reference numerals are assigned and the description is omitted.

[0059] The electric field diffusion plate 9 includes: frame portions 206 and 207 that form the periphery; cutout portions 203 and 204 formed by cutting a part of the frame portions 206 and 207; a connection portion 208 that connects the cut-off frame portions 206 and 207; and a center 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.

[0060] In other words, the electric field diffusion plate 9 opposes the open sides of two U-shaped frame portions 206 and 207 with a gap therebetween, connects the central portions of the frame portion 206 and the frame portion 207 to each other through the connection portion 208, and has a center electrode plate 202 at the central position of the connection portion.

[0061] In Figure 2B the central portion of the lower spiral electrode 201 and the center electrode plate 202 of the electric field diffusion plate 9 are coupled (capacitively coupled) through a coupling capacitor 205. Therefore, an electric field generated by electric field coupling is generated at the central portion of the electric field diffusion plate 9, and it is connected to the metal plate at the outer peripheral portion of the frozen food 8. Therefore, an electric field ( Figure 2C the electric field E shown) of substantially the same level as the electric field generated by electric field coupling passing through the central portion is generated in the entire electric field diffusion plate 9 ( Figure 2C the electric field E’ shown). At this time, as Figure 2C shown, the electric field diffusion plate 9 is disposed between the lower spiral electrode 201 and the frozen food 8. Thus, substantially the entire frozen food 8 is heated at the same electric field level, and thus homogeneous thawing can be performed. In addition, when the center electrode plate 202 of the electric field diffusion plate 9 is increased, the capacitive coupling with the lower spiral electrode 201 can also be increased. However, when the coupling amount is insufficient, the capacitive coupling amount can also be adjusted by thickening the width of the inner peripheral end of the lower spiral electrode 201.

[0062] Figure 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 Figure 3A it shows 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 when the lower spiral electrode 201 of the lower flat electrode 5 is also disposed on the upper flat electrode 4 in the high-frequency thawing device shown in Figure 2A . Figure 3BThis is a diagram showing an example of the analysis result between the electrodes of the high-frequency heating device shown in Patent Document 2 as the prior art. Additionally, regarding the return loss characteristics, the horizontal axis represents frequency [MHz], and the vertical axis represents return loss [dB]. The lower the value, the better the matching, and it becomes total reflection at 0 dB. During the analysis, to resonate at a frequency of 40.68 MHz, the upper and lower flat plate electrodes are 30 cm × 30 cm, the length of the helical electrode is approximately 200 cm, and the food material is a simulated food material with a size of 20 cm × 20 cm × 5 cm frozen to -20 °C. In Figure 3B of the prior art, electrodes with a size of 30 cm × 30 cm are used as parallel plate electrodes for calculation. The results of oscillation from 10 MHz to 100 MHz are shown.

[0063] In Figure 3B , it can be seen that in the conventional thawing based on parallel plates, the impedance between the electrodes shows capacitive characteristics, and in the return loss characteristics, it is generally a total reflection characteristic. Therefore, when using a matching circuit to achieve matching, even if the power supply power is about several hundred watts, a high voltage of more than several thousand volts will be generated between the electrodes due to the series resonance of the inductor for matching and the electrodes. Therefore, a high-voltage withstand matching circuit is required in the conventional high-frequency thawing machine, and there is a problem that the circuit becomes large-sized and the cost becomes high.

[0064] In contrast, in the electrodes of the present embodiment shown in Figure 3A , due to the inductance component of the helical electrode, a matching point based on series resonance is generated between the flat plate electrodes near the capacitive component of the parallel plate and the food material and the power supply frequency of 40.68 MHz. Therefore, the voltage generated between the flat plate electrodes is relatively low, about 200 V. Therefore, it is possible to adjust the shift of the matching point caused by the change in the dielectric constant accompanying the thawing state of the food material by using a low-voltage withstand and low-cost antenna tuner used in general amateur radio, etc., and thus it is possible to achieve miniaturization and low-cost of the circuit.

[0065] Figure 4A This is a diagram showing an example of the structure of the antenna tuner 2 of the high-frequency thawing device shown in Figure 1A . In Figure 4AIn [the circuit], 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. By switching the relays according to the control signal from the control terminal 403, the inductance value in series can be changed. Additionally, capacitors 424, 425, 426, and 427 are connected in parallel between the tuner input terminal 401 or the tuner output terminal 402 and GND via relays 415, 416, 417, and 418 respectively through relay 414, forming a structure for switching the grounding capacitance value to GND. Moreover, through relay 414, the grounding capacitance value switching component can be switched to be connected to the tuner input terminal 401 side or the tuner output terminal 402 side. Usually, when the impedance on the tuner output side is higher than that on the tuner input side, it is switched to the tuner output side, and when it is lower, it is switched to the tuner input side to perform the tuning operation.

[0066] In addition, in the circuit of the antenna tuner 2, due to the parasitic inductor 431 (parasitic inductor component) generated by the wiring winding of the inductor connected in series between the tuner input and output terminals and the parasitic capacitor 433 generated by the wiring winding of the capacitor connected in parallel between the tuner input and output terminals, when switching the inductance value and capacitance value by the relay, there is a jump in the change range larger than the design constant, resulting in problems such as inability to match, or insufficient matching, increased reflected power, and reduced heating efficiency. Therefore, it is equipped with: a cancellation capacitor 432 (first cancellation element) that is connected in series with the parasitic inductor 431 (parasitic inductance component) generated in the wiring winding of the inductor connected in series between the input and output terminals of the antenna tuner and resonates at the power supply frequency of the high-frequency power supply; and an inductor 434 (second cancellation element) that is connected in parallel with the parasitic capacitor 433 (parasitic capacitance component) generated in the wiring winding of the capacitor connected in parallel between the input and output terminals of the antenna tuner and resonates at the power supply frequency of the high-frequency power supply.

[0067] By adopting such a structure, it is possible to reduce the parasitic components caused by the mode adjustment of the antenna tuner in the power supply band, so a defrosting machine with less reflected power and excellent convergence can be obtained.

[0068] Figure 4B It is a diagram showing another example of the antenna tuner. In Figure 4BIn [the figure], an inductor 442 is connected between a tuner input terminal 401 and a tuner output terminal 402, and variable capacitance capacitors (variable capacitors) 441 and 443 are respectively connected between the input / output terminals of the tuner and GND. In this figure, the variable capacitance capacitors (variable capacitors) 441 and 443 require a mechanism for mechanical adjustment. However, by using variable capacitance capacitors, the offset of the matching point can be continuously adjusted. In addition, since there is no relay-based switching circuit, the routing winding is shortened. Therefore, even without adding inductors and capacitors for eliminating parasitic components, an antenna tuner circuit with excellent convergence can be obtained.

[0069] According to this embodiment, a high-frequency thawing device can be provided, which can achieve miniaturization and cost reduction of the circuit, has excellent convergence of the matching circuit, and can perform uniform thawing.

[0070] [Embodiment 2]

[0071] Figure 5 is a schematic structural diagram showing a high-frequency thawing device according to Embodiment 2 of the present invention. The high-frequency thawing device 200 is at least composed of an RF signal source 501 (RF: Radio Frequency) that outputs RF signals in MHz bands 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. Furthermore, the high-frequency power amplifier 503 is composed of a distribution circuit 511, a high-frequency amplifier 512, and a combining circuit 513. In addition, for Figure 1A Parts that are the same as those in Embodiment 1 of the high-frequency thawing device shown are labeled with the same numbers and the description is omitted.

[0072] Figure 5 The difference between the high-frequency thawing device 200 shown and that in Fig. 1 is that, instead of the high-frequency power supply 1 (Fig. 1), 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, 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.

[0073] Figure 5 The high-frequency thawing device 200 is configured such that the first lower spiral electrode 521 and the second lower spiral electrode 522 are arranged above the lower flat electrode 5 so as to face the first upper spiral electrode 6 and the second upper spiral electrode 7 arranged on the upper flat electrode 4.

[0074] 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 power 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 at equal intervals and point-symmetrically with respect to each other in such a way that their spirals do not overlap. In addition, 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 away from the lower flat electrode 5 upward.

[0075] In addition, the upper spiral electrode and the lower spiral electrode are arranged in such a way that their winding directions are opposite, 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 uses an RF signal source 501, an attenuator 502, a high-frequency power amplifier 503, a power supply circuit 504, a directional coupler 505, and is additionally provided with a power supply circuit 504, a control circuit 506, and a temperature sensor 507.

[0076] Figure 5 The high-frequency power amplifier 503 is configured to attenuate the high-frequency in the MHz band from the RF signal source 501 to the desired high-frequency power through the attenuator 502, then distribute it to each high-frequency amplifier 512 through a distribution circuit 511 for power amplification, and supply the high-frequency power of about several 100 W to 1000 W that has been power-combined through a synthesis circuit 513 to the electrode via the directional coupler 505 and the antenna tuner 2.

[0077] The directional coupler 505 measures the incident power and the reflected power of 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 to reduce the reflected power of the directional coupler 505. In addition, 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. Or, the control circuit 506 is configured to adjust the output power through the attenuator 502 according to the temperature state.

[0078] In the above structure, the frozen food 8 placed between the upper and lower spiral electrodes is thawed by dielectric heating according to the RF signal amplified by the high-frequency power amplifier 503. However, the directional coupler 505 detects the impedance change between the electrodes due to the change in the dielectric constant of the food, which varies according to the size and thawing state of the frozen food. The control circuit 506 adjusts the constants of the antenna tuner 2 to perform impedance matching of the electrode, thereby efficiently thawing. In addition, the completion of thawing is determined by measuring the temperature of the frozen food 8 with the temperature sensor 507.

[0079] 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 dielectric constant at the start of thawing of the frozen food 8 and the power transmission frequency (40.68 MHz in this embodiment), and the lengths of the second upper spiral electrode 7 and the second lower spiral electrode 522 are set to lengths that resonate with the dielectric constant at the end of thawing of the frozen food 8. By configuring in this way, the resonance frequency band of the spiral electrode and the foodstuff becomes wider, and the adjustment range of the matching of the antenna tuner 2 becomes narrower. Therefore, the convergence of the antenna tuner is improved, and it is possible to avoid thawing in a state where constant jumps caused by parasitic components of the antenna tuner result in non-matching, insufficient matching, large reflected waves, and poor heating efficiency. For example, at a power transmission frequency of 40.68 MHz, the length of a spiral electrode resonating at λ / 4 is approximately 2 m, but even if the lengths of the first and second spiral electrodes differ by only approximately 6 cm, broadbanding of the resonance frequency can be achieved.

[0080] Next, use Figure 11 to describe the process of the frozen food 8 from the start to the end of thawing. Figure 11 It 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.

[0081] In Figure 11 it is described centering on the action of adjusting the matching point by the antenna tuner 2 to maintain a state of good heating efficiency and perform thawing because the impedance matching point shifts as the dielectric constant changes during the thawing of the frozen food 8.

[0082] Place 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).

[0083] The control circuit 506 performs reset of the antenna tuner 2 (step S101), and adjusts the attenuator 502 to start transmitting the high-frequency power output from the high-frequency power amplifier 503 with a power lower than that required for normal thawing (step S102).

[0084] 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 to minimize the reflected power (step S103).

[0085] The control circuit 506 calculates the VSWR (Voltage Standing Wave Ratio) representing the matching state calculated from the incident power and the reflected power, and determines whether the VSWR is below the threshold value of the matching state (step S104). In step S104, when the VSWR is below the threshold value and a matching state has been achieved (Yes in step S104), the control circuit 506 starts delivering the high-frequency power output from the high-frequency power amplifier 503 with the high power required for thawing (step S106).

[0086] On the other hand, in processing step S104, when the VSWR is above the threshold value (No in step S104), the control circuit 506 notifies to change the position and height of the frozen food 8. As a notification unit, for example, the generation of sound based on a sound generating device, the display in text based on 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 the position and height of the frozen food 8 for adjustment, it returns to processing step S101 again, and the control circuit 506 resets the antenna tuner 2 and performs tuning again.

[0087] After starting power transmission in step S106, the control circuit 506 measures the temperature of the frozen food 8 through the temperature sensor 507, and determines whether the target temperature for the end of thawing has been reached (step S107). When the temperature of the frozen food 8 reaches the target temperature (Yes in step S107), the control circuit 506 notifies the completion of the thawing of the frozen food 8 and ends the processing (step S111).

[0088] When 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).

[0089] The control circuit 506 calculates the VSWR (Voltage Standing Wave Ratio) representing the matching state calculated from the incident power and the reflected power, and determines whether the VSWR is below the threshold value of the matching state (step S109).

[0090] In step S109, when the VSWR is below the threshold value and a matching state has been achieved (Yes in step S109), the control circuit 506 returns to step S106 and starts delivering the high-frequency power output from the high-frequency power amplifier 503 with the high power required for thawing (step S106).

[0091] On the other hand, in processing step S109, when the VSWR is above the threshold (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 through the antenna tuner 2 (step S110). After that, the process returns to step S104. If the VSWR is below the threshold, the power required for thawing is delivered, and the frozen food 8 is thawed again.

[0092] By measuring the voltage amplitude input to the variable matching circuit in this way, the matching state can be detected, and thus the thawing of the frozen food can be performed with relatively simple control.

[0093] With the above structure, according to this embodiment, even if the dielectric constant of the frozen food 8 changes due to thawing, by adjusting the antenna tuner to minimize the reflected power, a high-frequency thawing machine with excellent heating efficiency can be obtained.

[0094] Moreover, according to this embodiment, by adding capacitors and inductors to eliminate the parasitic components of the antenna tuner, the matching performance of the antenna tuner is improved. Therefore, from Figure 11 the processing step S104 shown, after passing through the processing step S105, it returns to the processing step S101, and the number of times of temporarily stopping power supply can be reduced. Therefore, the frequency of the thawing time becoming longer due to non-matching can be reduced.

[0095] In addition, according to this embodiment, in addition to the structure in which the first upper spiral electrode 6 and the second upper spiral electrode 7 are symmetrically arranged, the same spiral electrodes in which the first lower spiral electrode 521 and the second lower spiral electrode 522 are symmetrically related to each other are also arranged in the lower part. The frozen food 8 is thawed by the electric fields generated above and below. Therefore, homogeneous thawing can be performed on both sides of the food, and even for thick foods, the electric field penetrates into the interior, so homogeneous thawing can be performed.

[0096] In addition, according to this embodiment, since the first and second spiral electrodes are respectively set to slightly different lengths that resonate at the dielectric constant at the start and end of the thawing of the food at the power supply frequency, the broadband of the resonance frequency can be achieved, the convergence of the antenna tuner can be improved, and by reducing the number of switching elements of the antenna tuner, miniaturization and low cost of the circuit can be achieved. In addition, in this embodiment, the high-frequency power amplifier 503 uses a plurality of low-cost high-frequency amplifiers to obtain the large power required for thawing, so low cost can be achieved.

[0097] [Embodiment 3]

[0098] Figure 6FIG. 0 is a schematic structural diagram of the 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) is connected between the antenna tuner 2 and the upper flat electrode 4 and the lower flat electrode 5 connected to the position GND other than the case GND. In addition, for the parts repeated in the high-frequency thawing device of Embodiment 2 shown in Figure 5 the same reference numerals are given and the description thereof is omitted.

[0099] In Figure 6 Embodiment 3 shown in Figure 5 compared with the high-frequency thawing device of Embodiment 2 shown in

[0100] In Figure 5 the structure of the high-frequency thawing device of Embodiment 2, the electric field generated by the upper spiral electrode flows through an ineffective high-frequency current that does not contribute to thawing due to capacitive coupling with the case 3, which becomes a loss and causes a decrease in heating efficiency. In addition, the food material having a thickness is combined with the side surface of the case 3, and the electric field cannot reach the central portion of the food material, and there is a problem that the thawing of the central portion cannot be promoted. In the high-frequency thawing device 300 of 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 caused by capacitive coupling with the side surface of the case 3 is reduced, and the longitudinal electric field coupling becomes stronger. Therefore, according to the structure of the present embodiment, since the electric field passes through the central portion, even for thick food materials, homogeneous thawing can be achieved in the cross-sectional direction in addition to the upper and lower surfaces.

[0101] In addition, 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 signal source impedance of the high-frequency power amplifier 503, which is 50 Ω. In other words, the transformer 601a transforms to an impedance lower than the signal source impedance of the RF signal source 501. Therefore, in addition to the transmission line transformer with an impedance transformation ratio of 1:1, that is, the transformer 601a, by using a transmission line transformer 602b with an impedance transformation ratio of 4:1, a transmission line transformer 602c with a two-wire winding impedance transformation ratio of 9:4, and a transformer 602d with an arbitrarily changed turn ratio, the matching of the antenna tuner 2 is further improved.

[0102] The process from the start to the end of thawing the frozen food material 8 is the same as that described in Embodiment 2 Figure 11 described above.

[0103] [Embodiment 4]

[0104] Figure 7This is a schematic structural diagram of the high-frequency thawing device according to Embodiment 4 of the present invention. In the high-frequency thawing device 400, an electric field diffusion plate 701 (upper electric field diffusion plate) that realizes the homogenization of the electric field generated by the spiral electrodes shown in Figure 2B and Figure 2C is disposed between the upper spiral electrodes (first upper spiral electrode 6, 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 (first lower spiral electrode 521, second lower spiral electrode 522) and the frozen food 8. In addition, parts that are the same as those in Embodiment 3 of the high-frequency thawing device shown in Figure 6 are marked with the same numbers and the description is omitted. The electric field diffusion plate 701 and the upper spiral electrodes (first upper spiral electrode 6, 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 (first lower spiral electrode 521, second lower spiral electrode 522) are located above the lower flat electrode 5. The structures of the electric field diffusion plates 701 and 702 are the same as those of the electric field diffusion plate 9.

[0105] In Figure 7 the shown Embodiment 4, compared with the high-frequency thawing device of Embodiment 3 shown in Figure 6 , the difference is that the electric field diffusion plates 701 and 702 are respectively disposed between the upper spiral electrode and the food material and between the food material and the lower spiral electrode. Thus, Figure 2B the central electrode plate 202 of the electric field diffusion plate shown in is combined with the central part of the spiral electrode with a high electric field, and the high electric field in the central part is homogenized at the outer periphery of the food material through the metal plates ( Figure 2B the frame parts 206 and 207) at the outer peripheral part connected to the central electrode plate 202. Therefore, the homogenization of the electric field generated by the spiral electrode can be performed.

[0106] As described above, according to the present embodiment, in addition to symmetrically and pairwise disposing the first spiral electrode and the second spiral electrode, an electric field diffusion plate is also used, so that further homogenization of the electric field can be achieved.

[0107] 〔An example of the analysis result〕

[0108] Here, Figure 8A and Figure 8B and Figure 8C are used to illustrate the analysis result of the heat generation distribution on the surface of the food material by dielectric heating according to the above embodiment. Regarding the analysis result of each embodiment of the present invention, Embodiment 2 is shown as an example.

[0109] Figure 8A is a diagram showing the analysis result when dielectric heating is performed by the high-frequency heating device shown in Patent Document 1 (prior art). In Figure 8AIn this case, a spiral electrode with a length of λ / 4 is arranged above and below a flat electrode. Figure 8B It shows the analysis result when dielectric heating is performed by the high-frequency thawing device of Example 2 shown by Figure 5 the figure. Figure 8C It is a figure showing the analysis result when an electric field diffusion plate is added to the structure of Example 2. That is, Figure 8C It is a structure in which an electric field diffusion plate 9 is arranged on the lower spiral electrode with a length of λ / 4 shown by Figure 2B also arranged opposite to the upper flat electrode 4 side, and the analysis result when dielectric heating is performed by a high-frequency thawing device with a structure in which electric field diffusion plates are arranged on the upper and lower spiral electrodes.

[0110] The size of the spiral electrode is set to about 25 cm × 27 cm, and the analysis is performed in a state where a simulated food material of 20 cm × 20 cm × 5 cm is frozen to -20°C. The frequency is 40.68 MHz, and the distance between the spiral electrodes is 8 cm. In addition, as the Figure 8C electric field diffusion plate of the high-frequency thawing device analyzed in this case, a plate with an outer shape of 25 cm × 22 cm, a thickness of 1 cm, and a central electrode plate of 6 cm × 6 cm is used.

[0111] In Figure 8A the dielectric heating of the prior art, it is known that the heat generation on the surface of the food material proceeds along the shape of the spiral electrode. In particular, the spiral electrode in the central part with a high electric field is likely to cause uneven heating. In contrast, in Figure 8B Example 2 of the high-frequency thawing device, by symmetrically arranging the first and second spiral electrodes, the electric field generated from the spiral electrodes is homogenized. Therefore, it is known that the heat generation on the surface of the food material is also homogenized. In addition, in the spiral electrode, the higher the electric field in the central part and the closer to the outer peripheral part, the lower the electric field. Therefore, it is known that the heat generation of the food material is also closer to the end part, and the heat generation decreases. This is an effective structure for suppressing uneven heating generated at the end part of the food material due to the concentration of the electric field caused by the end effect. Therefore, it can be known that by adopting the structure of the first and second spiral electrodes, uneven heating in the central part can be reduced, and uneven heating generated at the end part of the food material can also be reduced. Therefore, uniform thawing can be performed. In addition, the structure using the Figure 8C electric field diffusion plate also reduces the heat generation caused by the high electric field in the central part. Therefore, uneven heating is suppressed compared with the prior art. Furthermore, by using the electric field diffusion plate in the first and second spiral electrode structures, the heat generation in the central part is suppressed. Therefore, more uniform thawing can be performed.

[0112] Figure 9 It is a figure showing the relationship between the frequency and the return loss in the high-frequency thawing device of Example 2. In Figure 9 this case, it shows in Figure 5In the high-frequency thawing device of Embodiment 2 shown, the first upper spiral electrode 6 and the first lower spiral electrode 521 are set to lengths that resonate with the dielectric constant at the start of thawing of the frozen food 8 and the power transmission frequency (40.68 MHz in this embodiment), and the lengths of the second upper spiral electrode 7 and the second lower spiral electrode 522 are set to lengths that resonate with the dielectric constant at the end of thawing of the frozen food 8, and as a result, an analysis of the effect of broadening the frequency band of the resonance frequency of the spiral electrode and the food is carried out. For comparison, an analysis was also carried out on the thawing device of the prior art shown in Figure 8A The constants of the spiral electrode and the like used for the analysis are the same as those for the analysis of the heat generation amount on the surface of the food shown in Figure 8A , Figure 8B In the analysis of the high-frequency thawing device of Embodiment 2 shown in Figure 5 , an analysis was carried out by giving a difference of about 6 cm to the lengths of the first and second spiral electrodes in the upper and lower parts.

[0113] Figure 9 The horizontal axis is the frequency when changing 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 becomes a total reflection with complete non-matching. As shown in Figure 9 , in Embodiment 2, the frequency band is broadened by about 1.45 times under the 3 dB bandwidth. Therefore, it is possible to improve the convergence of the antenna tuner, and it is possible to reduce the number of variable elements. Therefore, a small-sized and low-cost high-frequency thawing machine can be obtained.

[0114] Figure 10 is a circuit diagram showing another example of the structure of the antenna tuner. In Figure 10 , a circuit structure showing the component arrangement of the antenna tuner used in Embodiment 2 shown in Figure 5 , Embodiment 3 shown in Figure 6 , and Embodiment 4 shown in Figure 7 is shown. In the structure shown in Figure 10 , compared with the antenna tuner circuit shown in Figure 4A , the differences are that the constants of the parasitic inductor 1001, the parasitic capacitor 1002, the canceling capacitor 1003, and the canceling inductor 1004 are different from those in Figure 6 , and the directional coupler 505 and the control circuit 506 are built into the antenna tuner 2. In addition, parts of the circuit of the antenna tuner 2 that are repeated with Figure 4A are marked with the same reference numerals and the description is omitted.

[0115] Figure 10 Relative to Figure 4A, configured in a loop in such a way that the leads of the inductors 411, 422, 423 connected in series between the antenna input and output terminals and the relays 411, 412, 413 are shortened. Therefore, the value of the parasitic inductor 1001 is smaller than Figure 4A , so by increasing or not requiring the cancellation of the capacitance 1003, the convergence of the antenna tuner based on the parasitic inductor component can be improved.

[0116] In addition, by adopting a configuration in which the capacitors 424, 426 connected in parallel between the antenna input and output terminals and the capacitors 425, 427 are branched into two in parallel, the capacitor 427 farthest from the switching relay 414 has a shorter distance from the relay in the branched configuration. Therefore, the value of the equivalent parasitic capacitance 1002 becomes smaller, and by increasing or not requiring the cancellation of the inductor 1004, the convergence of the antenna tuner based on the parasitic capacitance component can be improved. Furthermore, the connection distance between the switching relay 414 and the antenna input and output can also be shortened. Therefore, the parasitic inductance component caused by this lead can also be reduced.

[0117] In the above structure, by incorporating the directional coupler 505 and the control circuit 506 into the antenna tuner 2, miniaturization of the circuit can be achieved, and by reducing parasitic inductors and parasitic capacitances, the convergence can be improved, and the number of switching elements can be reduced, thereby enabling cost reduction.

[0118] [Embodiment 5]

[0119] Figure 12A is a structural diagram showing an example of the outline of the high-frequency thawing device according to Embodiment 5 of the present invention. Figure 12A The high-frequency thawing device consists of a frozen food 8, a high-frequency power supply 1201, a flat electrode 1202, and a helical antenna 1203. The high-frequency power supply 1201 in the figure is a power supply that supplies high-frequency power with a relatively high frequency of about several 100 MHz to 2.4 GHz, and supplies the high-frequency power to the helical antenna 1203 via the flat electrode 1202. In addition, the helical 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, connects the outer peripheral end to the flat electrode 1202, and the inner peripheral end is in an open state. Since the helical antenna 1203 efficiently radiates electromagnetic waves due to resonance based on the λ / 4 wavelength, the frozen food 8 placed on the helical antenna can be thawed.

[0120] By adopting the above structure, a high-frequency thawing device is obtained that can thaw not only by the electric field generated from the helical antenna 1203 but also by electromagnetic waves.

[0121] Figure 12B is a schematic structural diagram showing another example of the high-frequency thawing device according to Embodiment 5 of the present invention.Figure 12B The high-frequency thawing device and Figure 12A In comparison, the difference is that a plurality of first spiral antennas 1204 and an antenna pair symmetrically arranged with respect to the second spiral antenna 1205 are arranged on the flat electrode 1202. For other parts that are Figure 12A repeated, the same reference numerals are marked and the description is omitted.

[0122] The first spiral antenna 1204 and the second spiral antenna 1205 are arranged point-symmetrically and at equal intervals in such a way that their spirals do not overlap with each other.

[0123] In Figure 12B , in addition to being able to obtain the same effects as the high-frequency thawing device shown in Figure 12A , the first spiral antenna 1204 and the second spiral antenna 1205 form a self-assisted antenna with a constant antenna impedance with respect to the supply frequency. Since the matching is excellent in a wide frequency band, a matching circuit such as an antenna tuner is not required. And by arranging a plurality of spiral pairs on the flat electrode 1202, it is also possible to thaw relatively large food materials.

[0124] Figure 12C is a schematic structural diagram showing another example of the high-frequency thawing device according to Embodiment 5 of the present invention. Figure 12C The high-frequency thawing device is composed of a semiconductor wafer 1206, a flat electrode 1207, and an inverted L-shaped antenna 1208. The inverted L-shaped antenna 1208 has a portion horizontally arranged along the semiconductor wafer 1206 and a portion bent downward from this horizontal portion.

[0125] In addition, the high-frequency power supply 1201 is a power supply that supplies high-frequency power of several GHz or higher. The 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. In addition, the inverted L-shaped antenna 1208 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 a plurality of them are arranged on the flat electrode 1207. And 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. In addition, if the transmission frequency becomes a high frequency above the GHz band, the wavelength also becomes shorter and it is difficult to maintain the spiral shape. Therefore, it is necessary to be arranged as an inverted L-shaped antenna, and it is also necessary to shorten the wiring length between the flat electrodes 1207, so it becomes a structure formed on the semiconductor wafer 1206.

[0126] By adopting the above structure, according to this embodiment, a high-frequency thawing device can be obtained that can efficiently thaw by radiating electromagnetic waves even at high frequencies above the GHz band.

[0127] In addition, the present invention is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments are examples that have been described in detail for easy understanding of the present invention and are not necessarily limited to having all the structures described. Further, a part of the structure of a certain embodiment can be replaced with the structure of another embodiment, and also, the structure of another embodiment can be added to the structure of a certain embodiment. In addition, with respect to a part of the structure of each embodiment, addition, deletion, or replacement with other structures can be performed.

Claims

1. A high-frequency thawing device, characterized in that it includes: an upper flat electrode and a lower flat electrode, which are arranged oppositely up and down in a housing; an upper spiral electrode, which is arranged below the upper flat electrode and connected to the upper flat electrode; and a high-frequency power supply, one of which is connected to the upper flat electrode, the other is connected to the lower flat electrode, and supplies high-frequency power, 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, and the upper spiral electrode is composed of a first upper spiral electrode and a second upper spiral electrode whose outer peripheral ends are connected to the upper flat electrode and whose inner peripheral ends are open, the first upper spiral electrode and the second upper spiral electrode are arranged point-symmetrically and at equal intervals in such a way that their spirals do not overlap each other, dielectric heating is performed on the object to be heated arranged between the first upper spiral electrode, the second upper spiral electrode and the lower flat electrode.

2. The high-frequency thawing device according to claim 1, characterized in that it includes a lower spiral electrode, which is arranged above the lower flat electrode and connected to the lower flat electrode, 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 of the lower spiral electrode is connected to the lower flat electrode, and the inner peripheral end is open.

3. The high-frequency thawing device according to claim 1, characterized in that it includes a lower spiral electrode, which is arranged above the lower flat electrode and connected to the lower flat electrode, 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, and the lower spiral electrode is composed of a first lower spiral electrode and a second lower spiral electrode whose outer peripheral ends are connected to the lower flat electrode and whose inner peripheral ends are open, the first lower spiral electrode and the second lower spiral electrode are arranged point-symmetrically and at equal intervals in such a way that their spirals do not overlap each other.

4. The high-frequency thawing device according to claim 3, characterized in that an upper electric field diffusion plate capacitively coupled to the central part of the upper spiral electrode is arranged between the object to be heated and the upper spiral electrode.

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

6. The high-frequency thawing device according to claim 5, characterized in that the upper electric field diffusion plate and the lower electric field diffusion plate are composed of two frame parts formed in a U shape and facing each other with a gap between the open sides, 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.

7. The high-frequency thawing device according to any one of claims 1 to 6, characterized in that It is provided with an adjustment circuit which is arranged between the high-frequency power supply and the upper flat electrode and adjusts the impedance matching with the high-frequency power supply.

8. The high-frequency thawing device according to claim 7, characterized in that it is provided with: a directional coupler which is arranged between the high-frequency power supply and the adjustment circuit and measures the incident power and the reflected power input to the adjustment circuit; and a control circuit which inputs the result measured by the directional coupler and controls the adjustment circuit to reduce the reflected power.

9. The high-frequency thawing device according to claim 7, characterized in that the adjustment circuit is an antenna tuner having a structure in which the capacitance value and the inductance value of a capacitor are switched by a relay.

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

11. The high-frequency thawing device according to claim 3, characterized in that the lower flat electrode is connected to the ground, it is provided with an adjustment circuit which is arranged between the high-frequency power supply and the upper flat electrode and adjusts the impedance matching with the high-frequency power supply, a balun is provided between the upper flat electrode and the adjustment circuit and between the lower flat electrode and the ground, and the balun converts the power output from the adjustment circuit into a balanced signal.

12. The high-frequency thawing device according to claim 11, characterized in that the balun transforms into an impedance lower than the signal source impedance of the high-frequency power supply.

13. A high-frequency thawing device, characterized in that it is provided with: a helical antenna which is arranged on a flat electrode; and a high-frequency power supply which supplies high-frequency power to the helical antenna via the flat electrode, the length of the helical antenna 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 of the helical antenna is connected to the flat electrode and 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, characterized in that it is provided with: a helical antenna which is arranged on a flat electrode; and a high-frequency power supply which supplies high-frequency power to the helical antenna via the flat electrode, the length of the helical antenna is an integer multiple of 1 / 4 of the wavelength λ of the power transmission frequency from the high-frequency power supply, and the helical antenna is composed of a first helical antenna and a second helical antenna whose outer peripheral ends are connected to the flat electrode and inner peripheral ends are open, the first helical antenna and the second helical antenna are arranged point-symmetrically and at equal intervals in such a way that their spirals do not overlap, and the object to be heated arranged on the helical antenna is heated.

15. The high-frequency thawing device according to claim 14, wherein: a plurality of the spiral antennas are provided.

16. A high-frequency thawing device, wherein: an inverted L-shaped antenna disposed on a flat electrode arranged on a semiconductor wafer; and a high-frequency power supply for supplying high-frequency power to the inverted L-shaped antenna via the flat electrode, the length of the inverted L-shaped antenna is an integer multiple of 1 / 4 of the wavelength λ of the power transmission frequency from the high-frequency power supply, and the inverted L-shaped antenna heats an object to be heated on the flat electrode.

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