High-frequency defrosting device and high-frequency defrosting method

Abstract

To reduce uneven heating and defrost frozen objects in a short time.SOLUTION: A high-frequency defrosting device includes a flat upper electrode and a flat lower electrode arranged in parallel. Multiple meanderline electrodes, formed in a meanderline pattern with the center of the upper electrode or the center of the lower electrode as the symmetry point, are arranged in point symmetry on each of the upper electrode and lower electrode. One end of each meanderline electrode is electrically connected to the upper electrode or the lower electrode, respectively. The other end of the meanderline electrode, positioned centrally on the upper electrode or the lower electrode, is not electrically connected to the upper electrode or the lower electrode. The electrical length of the meanderline electrodes is formed such that it is an integer multiple of one-quarter of the wavelength λ of the RF signal output by the high-frequency power source.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a high-frequency thawing device and a high-frequency thawing method. [Background technology]

[0002] Regarding thawing frozen foods and the like, for example, Patent Document 1 describes "a radio frequency power application device comprising: a radio frequency power generation source that generates radio frequency power; a coil having a length that is approximately an integral multiple of 1 / 4 of the wavelength of the radio frequency power generated by the radio frequency power generation source, and that generates a magnetic field when radio frequency power is supplied from the radio frequency power generation source and a radio frequency current flows; and an impedance matching device that matches the impedance between the radio frequency power generation source and the coil." [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 09-293600 Summary of the Invention [Problem to be solved by the invention]

[0004] FIG. 9 shows an example of heating unevenness caused by using a coil (spiral electrode). When using a coil with a configuration that supplies power from the center, such as the high-frequency power applicator described in Patent Document 1, as shown on the left side of the figure, the center of the coil is heated strongly at the start of thawing. This causes heat conduction from the center to the edge of the food, making heating unevenness less likely to occur. However, as shown on the right side of the figure, as the thawing of the center of the food progresses to approximately 0°C, the food's dielectric constant changes, and the magnetic field generated in the axial direction of the coil interacts with the food, resulting in a circular (donut-shaped) heating unevenness where the temperature around the food is higher than the temperature at the center. Furthermore, in the case of the high-frequency power applicator described in Patent Document 1, power is supplied from the power source to the center of the coil via an impedance matcher. This configuration makes it difficult to thaw food in a short time because the signal source impedance is included in the coil's resonance system, resulting in losses.

[0005] The present invention has been made in view of the above points, and has an object to reduce uneven heating and to enable frozen objects to be thawed in a short time. [Means for solving the problem]

[0006] The present application includes a number of means for solving at least part of the above problems, examples of which are as follows.

[0007] In order to solve the above-mentioned problems, one embodiment of the present invention provides a high-frequency thawing device that thaws an object to be thawed by dielectric heating, and includes: a flat upper electrode and a flat lower electrode arranged in parallel at positions above and below a position where the object to be thawed is placed; and a high-frequency power supply that outputs high-frequency RF signals to the upper electrode and the lower electrode. On each of the upper electrode and the lower electrode, a plurality of meander-line electrodes are arranged in point symmetry with respect to the center of the upper electrode or the lower electrode. One end of each meander-line electrode is electrically connected to the end of the upper electrode or the lower electrode, and the other end of the meander-line electrode arranged toward the center of the upper electrode or the lower electrode is electrically disconnected from the upper electrode or the lower electrode. The electrical length of each meander-line electrode is formed to be an integer multiple of 1 / 4 of the wavelength λ of the RF signal output by the high-frequency power supply. [Effects of the Invention]

[0008] According to the present invention, it is possible to reduce uneven heating and thaw a frozen object in a short time.

[0009] Problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram showing an example of the configuration of a high-frequency thawing device according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a diagram illustrating an example of a balun transformer. [Figure 3] FIG. 3 is a flowchart illustrating an example of a thawing method using a high-frequency thawing device. [Figure 4] FIG. 4 is a diagram showing an example of a decompression result according to the first embodiment. [Figure 5] FIG. 5 is a diagram showing an example of the configuration of a high-frequency thawing device according to the second embodiment of the present invention. [Figure 6]FIG. 6 is a diagram showing an example of the configuration of a high-frequency thawing device according to the third embodiment of the present invention. [Figure 7] FIG. 7 is a diagram showing an example of the shape of the metal plate. [Figure 8] FIG. 8 is a diagram showing an example of the relationship between uneven heating occurring in an object to be thawed and the size and arrangement of the metal plate. [Figure 9] FIG. 9 shows an example of uneven heating caused by the prior art. DETAILED DESCRIPTION OF THE INVENTION

[0011] Several embodiments of the present invention will be described below with reference to the drawings. Each embodiment is an example for explaining the present invention, and appropriate omissions and simplifications have been made for clarity of explanation. The present invention can be implemented in various other forms. Unless otherwise specified, each component may be singular or plural. The position, size, shape, and scope of each component shown in the drawings may not represent the actual position, size, shape, and scope to facilitate understanding of the invention. In all drawings used to explain the embodiments, identical components are generally designated by the same reference numerals, and repeated description of such components will be omitted. Furthermore, in the following embodiments, a component (including an element step, etc.) is not necessarily essential unless otherwise specified or considered to be clearly essential in principle. Furthermore, when a term "consists of A," "composed of A," "having A," or "including A" is used, it does not exclude other elements unless otherwise specified, such as when referring to only that element. Similarly, in the following embodiments, when referring to the shape, positional relationship, etc. of a component, etc., it includes those that are substantially similar or approximate to that shape, etc., unless otherwise specified or considered to be clearly essential in principle. Furthermore, "obtaining" includes, as specific examples, at least the subject generating, calculating, or receiving from outside.

[0012] <Configuration example of the high-frequency thawing device 100 according to the first embodiment of the present invention> The high-frequency thawing device 100 according to the first embodiment of the present invention is intended to be placed, for example, in the back yard of a retail store such as a convenience store or supermarket, and to thaw frozen food and ingredients such as boxed lunches and prepared dishes stored according to the number of customers entering the store, and to display the thawed food on store shelves as chilled items, or to provide the thawed food to customers, etc. Hereinafter, the frozen food and ingredients to be thawed by the high-frequency thawing device 100 will be referred to as the object to be thawed T.

[0013] 1 shows an example of the configuration of a high-frequency thawing device 100. The high-frequency thawing device 100 thaws an object T to be thawed placed between electrodes by dielectric heating. The high-frequency thawing device 100 includes a high-frequency power supply 10, a directional coupler 17, an antenna tuner 18, a balun transformer 19, a power supply circuit 20, a control circuit 21, and a thawing chamber 101.

[0014] The high-frequency power supply 10 has an RF signal source 11, an attenuator 12, and a power transmitting amplifier 13. The RF signal source 11 generates an RF signal in a MHz band such as 13.56 MHz, 27.12 MHz, or 40.68 MHz that belongs to the ISM (Industrial Scientific and Medical Band), and outputs the signal to the attenuator 12. The attenuator 12 attenuates the RF signal under control of a control circuit 21 and outputs the attenuated RF signal to the power transmitting amplifier 13. The power transmitting amplifier 13 has a distribution circuit 14, multiple amplification elements 15, and a combining circuit 16, and amplifies a predetermined component of the RF signal from the attenuator 12 under control of the control circuit 21.

[0015] The RF signal output from the power transmission amplifier 13 is input to the upper electrode 110 and the lower electrode 120 of the thawing chamber 101 via the directional coupler 17, the antenna tuner 18, and the balun transformer 19.

[0016] The directional coupler 17 detects the amount of incident RF signal input from the power transmission amplifier 13 and the amount of reflection input from the antenna tuner 18, and outputs the results to the control circuit 21.

[0017] Under the control of the control circuit 21, the antenna tuner 18, together with the balun transformer 19, adjusts and matches the impedance between the upper electrode 110 and the lower electrode 120.

[0018] FIG. 2 shows five examples 19a to 19e of the balun transformer 19, including a voltage balun, a 4:1 balun transformer, a transformer, a voltage balun+4:1 transformer, and a 4:1 transformer+voltage balun.

[0019] Returning to Fig. 1, the power supply circuit 20 supplies power to the power transmitting amplifier 13 under control of the control circuit 21. The control circuit 21 calculates a VSWR (Voltage Standing Wave Ratio) (incident amount / reflected amount), which is the ratio between the incident amount of the RF signal input from the directional coupler 17 and the reflected amount from the antenna tuner 18, and controls the attenuator 12, the antenna tuner 18, and the power supply circuit 20 based on the VSWR. The UI (User Interface) unit 22 is, for example, a touch panel or the like, and displays various information and accepts user operations.

[0020] The thawing chamber 101 includes a flat upper electrode 110 and a lower electrode 120 arranged parallel to each other above and below a position where an object T to be thawed is placed inside the chamber.

[0021] On the upper electrode 110, a plurality of meander-line electrodes (two electrodes 111 and 112 in the figure) are arranged symmetrically with respect to the center of the upper electrode 110. One end of each of the electrodes 111 and 112 is electrically connected to the edge of the upper electrode 110, and the other end, which is arranged toward the center of the upper electrode 110, is electrically disconnected from the upper electrode 110 (open state).

[0022] Similarly, on the lower electrode 120, a plurality of meander-line electrodes (two electrodes 121 and 122 bent alternately in the front-to-rear direction in the illustrated example) are arranged symmetrically with respect to the center of the lower electrode 120. One end of each of the electrodes 121 and 122 is electrically connected to the edge of the lower electrode 120, and the other end, which is located toward the center of the lower electrode 120, is electrically disconnected from the lower electrode 120 (open state).

[0023] The electrical length of each of the plurality of meander-line electrodes arranged on the upper electrode 110 and the lower electrode 120 is an integral multiple of ¼ of the wavelength λ of the RF signal output by the high frequency power supply 10.

[0024] In particular, some of the multiple meander-line electrodes provided on upper electrode 110 (e.g., electrode 111) have electrical lengths that are an integral multiple of 1 / 4 of the wavelength λ of an RF signal that resonates with the (known) dielectric constant of the object to be thawed T at the start of thawing, and some other electrodes (e.g., electrode 112) have electrical lengths that are an integral multiple of 1 / 4 of the wavelength λ of an RF signal that resonates with the (known) dielectric constant of the object to be thawed T at the end of thawing. Note that although the dielectric constant differs depending on the type of object to be thawed T, the difference in the dielectric constant of the object to be thawed between the start and end of thawing is greater than the difference in dielectric constant due to differences in the type of object to be thawed T, and therefore, the difference in dielectric constant due to differences in the type of object to be thawed T will be ignored here.

[0025] Furthermore, when meander-line electrodes are provided on the upper electrode 110 in addition to the electrodes 111 and 112, the electrical length of the electrodes is set to a length between an integral multiple of 1 / 4 of the wavelength λ of the RF signal that resonates with the dielectric constant of the object to be thawed T at the start of thawing and an integral multiple of 1 / 4 of the wavelength λ of the RF signal that resonates with the dielectric constant of the object to be thawed T at the end of thawing. The same applies to the electrical lengths of the multiple meander-line electrodes provided on the lower electrode 120.

[0026] In this embodiment, the electrodes 111, 112, 121, and 122 are bent alternately in the front-to-back direction, thereby canceling out the magnetic field generated by energization. Furthermore, the absence of a coil (spiral electrode) suppresses the generation of a magnetic field in the up-and-down direction, thereby reducing the occurrence of annular heating unevenness due to the generation of the magnetic field. Furthermore, the open ends of the upper electrode 110 and the lower electrode 120, where the electric field is stronger than at the connection ends of the electrodes 111, 112, 121, and 122, are provided toward the center of the upper electrode 110 and the lower electrode 120. Therefore, heat conduction occurs from the center of the object T to be thawed to the ends, preventing uneven heating, such as the ends of the object T being heated first.

[0027] <About the decompression process> FIG. 3 is a flowchart illustrating an example of the defrosting process performed by the high-frequency defrosting device 100.

[0028] The defrosting process is started when the user places the object T to be defrosted at a predetermined position in the defrosting box 101 and performs a predetermined start operation using the UI unit 22.

[0029] First, the control circuit 21 controls the antenna tuner 18 to reset the impedance between the upper electrode 110 and the lower electrode 120 to a predetermined value together with the balun transformer 19 (step S1). Next, the control circuit 21 controls the power supply circuit 20 to start transmitting power to the power transmitting amplifier 13 at a predetermined low power (step S2). This generates an electric field in the thawing chamber 101, and thawing of the object T to be thawed begins.

[0030] Next, the control circuit 21 calculates the VSWR using the incident amount and reflection amount of the RF signal input from the directional coupler 17, and controls the antenna tuner 18 based on the VSWR to adjust and match the impedance between the upper electrode 110 and the lower electrode 120 (step S3).

[0031] Next, the control circuit 21 determines whether the VSWR calculated in step S3 is equal to or less than a predetermined threshold (step S4). If it is determined that the VSWR is not equal to or less than the predetermined threshold (NO in step S4), there is a possibility that the object to be thawed T may be overheated, so the control circuit 21 controls the UI unit 22 to notify the user to change the position or height of the object to be thawed T (step S5). Thereafter, the control circuit 21 returns the process to step S1 and repeats step S1 and subsequent steps.

[0032] On the other hand, if it is determined that the VSWR calculated in step S3 is equal to or less than the predetermined threshold value (YES in step S4), then the control circuit 21 controls the power supply circuit 20 to change the power transmission to the power transmission amplifier 13 to a predetermined high power (step S6).

[0033] Next, the control circuit 21 determines whether or not the temperature of the object to be thawed T has reached a preset target temperature based on the output of a sensor (not shown) provided in the thawing chamber 101 (step S7).

[0034] If it is determined that the temperature of the object T to be thawed has not reached the target temperature (NO in step S7), the control circuit 21 then calculates the VSWR again (step S8) and determines whether the VSWR calculated in step S8 is equal to or less than a predetermined threshold (step S9). If the control circuit 21 determines that the VSWR calculated in step S8 is equal to or less than the predetermined threshold (YES in step S9), the process returns to step S7, and steps S7 and onward are repeated.

[0035] On the other hand, if the control circuit 21 determines that the VSWR calculated in step S8 is not equal to or less than the predetermined threshold value (NO in step S9), the control circuit 21 controls the power supply circuit 20 to change the power transmission to the power transmitting amplifier 13 from high power to low power, and also controls the antenna tuner 18 to adjust and match the impedance between the electrodes (step S10). Thereafter, the control circuit 21 returns the process to step S4 and repeats step S4 and subsequent steps.

[0036] Then, in step S7, if it is determined that the temperature of the object to be thawed T has reached the target temperature (YES in step S7), the control circuit 21 controls the UI unit 22 to notify the user that the thawing has ended (step S11). This ends the thawing process.

[0037] 4 shows an example of the thawing results obtained by the high-frequency thawing device 100. In the case of the high-frequency thawing device 100, the open ends of the electrodes 111, 112, 121, and 122, where the electric field is stronger, are located near the center of the upper electrode 110 and the lower electrode 120. Therefore, as shown on the left side of the figure, at the start of thawing, heat conduction occurs from the center to the edges of the object to be thawed T, and thawing is performed, making it difficult for uneven heating to occur. Furthermore, as shown on the right side of the figure, even when the thawing of the center of the object to be thawed T has progressed to approximately 0°C, no circular (doughnut-shaped) uneven heating is observed, as shown on the right side of FIG. 9, indicating that uneven heating has been reduced.

[0038] <Configuration example of high-frequency thawing device 200 according to the second embodiment of the present invention> 5 shows an example of the configuration of a high-frequency thawing device 200 according to a second embodiment of the present invention. In the high-frequency thawing device 200, the thawing chamber 101 of the high-frequency thawing device 100 (FIG. 1) is replaced with a thawing chamber 201. Components common to the high-frequency thawing device 200 and the high-frequency thawing device 100 are given the same reference numerals, and descriptions thereof will be omitted as appropriate.

[0039] The thawing chamber 201 of the high-frequency thawing device 200 includes an upper electrode 110 and a lower electrode 120, similar to the thawing chamber 101 (FIG. 1).

[0040] The upper electrode 110 has a plurality of electrodes (two electrodes 211, 212 in the figure) arranged symmetrically with respect to the center of the upper electrode 110, each of which has a meander-line shape at its end and spirals from the middle toward the center around the symmetry point. One end of the electrodes 211, 212, which is meander-line shaped at the end of the upper electrode 110, is electrically connected to the upper electrode 110, and the other end, which is spiral shaped, is electrically disconnected from the upper electrode 110 (open state).

[0041] Similarly, on the lower electrode 120, a plurality of electrodes (two electrodes 221 and 222 in the figure) are arranged point-symmetrically, with the end sides being meander-line shaped and spiraling from the middle toward the center around the symmetric point, with the center of the lower electrode 120 as the point of symmetry. One end of the electrodes 221 and 222, which is formed in a meander-line shape on the end side of the lower electrode 120, is electrically connected to the lower electrode 120, and the other end, which is formed in a spiral shape, is electrically disconnected from the lower electrode 120 (open state).

[0042] The electrical length of each of the electrodes 211 , 212 , 221 , and 222 is set to an integral multiple of ¼ of the wavelength λ of the RF signal output from the high frequency power supply 10 .

[0043] In particular, the electrical length of electrode 211 provided on upper electrode 110 is an integer multiple of 1 / 4 of the wavelength λ of an RF signal that resonates with the dielectric constant of object T to be thawed at the start of thawing, and the electrical length of electrode 212 is an integer multiple of 1 / 4 of the wavelength λ of an RF signal that resonates with the dielectric constant of object T to be thawed at the end of thawing. As described above, the electrical lengths of electrodes 211 and 212 are different, but this is adjusted by changing the line length of the spirally formed portion. The same applies to the electrical lengths of electrodes 221 and 222 provided on lower electrode 120.

[0044] Generally, when a spiral electrode and a meander-line electrode have the same electrical length, the spiral electrode has a shorter line length than the meander-line electrode. Therefore, since the electrodes 211, 212, 221, and 222 of this embodiment are formed into a spiral shape from the middle, the line length can be shorter than that of the electrodes 111, 112, 121, and 122 of the first embodiment.

[0045] Therefore, in this embodiment, the area of ​​the electrodes 211 and 212 that occupy the upper electrode 110 and the area of ​​the electrodes 221 and 222 that occupy the lower electrode 120 can be reduced compared to the first embodiment. Furthermore, since the spiral electrodes are arranged on the central side of the upper electrode 110 and the lower electrode 120, the electric field at the center of the upper electrode 110 and the lower electrode 120 can be increased. This allows the object T to be thawed to be thawed from the center.

[0046] <Configuration example of high-frequency thawing device 300 according to the third embodiment of the present invention> 6 shows an example of the configuration of a high-frequency thawing device 300 according to a third embodiment of the present invention. The high-frequency thawing device 300 is configured by adding metal plates 311 and 321 to the thawing chamber 201 of the high-frequency thawing device 200 (FIG. 5). Components common to the high-frequency thawing device 300 and the high-frequency thawing devices 100 and 200 are designated by the same reference numerals, and descriptions thereof will be omitted where appropriate.

[0047] Metal plate 311 is disposed between electrodes 211, 212 provided on upper electrode 110 and a position inside the refrigerator where an object to be thawed T is placed. Similarly, metal plate 321 is disposed between electrodes 221, 222 provided on lower electrode 120 and a position inside the refrigerator where an object to be thawed T is placed.

[0048] 7 shows three examples of the shape of the metal plate 311 (321). The metal plate 311a has a rectangular ring-shaped outer peripheral portion 3111 that covers the vicinity of the spiral outer periphery of the electrodes 211, 212, a ring-shaped central portion 3112 that covers the central portion of the spiral of the electrodes 211, 212, and a connecting portion 3113 that connects the outer peripheral portion 3111 and the central portion 3112, thereby capacitively coupling the vicinity of the spiral outer periphery and the central portion of the electrodes 211, 212. Notches 3114 are formed in the outer peripheral portion 3111 and the central portion 3112 to prevent them from forming a closed loop.

[0049] The metal plate 311b has a rectangular ring-shaped outer peripheral portion 3111 that covers the spiral outer periphery of the electrodes 211, 212, a disk-shaped central portion 3115 that covers the spiral central portion of the electrodes 211, 212, and a connecting portion 3113 that connects the outer peripheral portion 3111 and the central portion 3115, thereby capacitively coupling the spiral outer periphery of the electrodes 211, 212 with the central portion.

[0050] The metal plate 311c has a disk-shaped central portion 3116 that covers the spiral central portion of the electrodes 211 and 212.

[0051] FIG. 8 shows an example of the relationship between the annular heating unevenness occurring in the object to be thawed T and the shape and arrangement of the metal plate 311.

[0052] When metal plates 311a and 311b are used, in addition to the same effects as in the second embodiment, the high electric field generated in the central part of the spiral can be homogenized by bringing it closer to the same potential all the way to the periphery of the spiral by the outer peripheral portion 3111, thereby enabling more uniform thawing.

[0053] When metal plates 311b and 311c are used, in addition to the same effects as in the second embodiment, the central portion 3113 can shield the magnetic field, which is the cause of the annular heating unevenness that occurs in the object to be thawed T, thereby reducing the annular heating unevenness.

[0054] It should be noted that a metal plate 311 and a metal plate 321 may be added to the thawing chamber 101 of the high-frequency thawing device 100 (FIG. 1).

[0055] The present invention is not limited to the above-described embodiments, and various modifications are possible. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with or add to the configuration of another embodiment. [Explanation of symbols]

[0056] 10...High frequency power supply, 11...RF signal source, 12...Attenuator, 13...Power transmission amplifier, 14...Distribution circuit, 15...Amplifying element, 16...Combining circuit, 17...Directional coupler, 18...Antenna tuner, 19...Balun transformer, 20...Power supply circuit, 21...Control circuit, 22...UI unit, 100...High frequency thawing device, 101...Thawing cabinet, 110...Upper electrode, 111...Electrode, 112...Electrode 120 lower electrode, 121 electrode, 122 electrode, 200 high frequency thawing device, 201 thawing chamber, 211 electrode, 212 electrode, 221 electrode, 222 electrode, 300 high frequency thawing device, 311 metal plate, 321 metal plate, 3111 peripheral portion, 3112 central portion, 3113 connecting portion, 3114 notch, 3115 central portion, 3116 central portion

Claims

1. A high-frequency thawing device that thaws an object to be thawed by dielectric heating, a flat upper electrode and a flat lower electrode arranged in parallel at positions sandwiching from above and below a position where the object to be thawed is placed; a high frequency power supply that outputs a high frequency RF signal to the upper electrode and the lower electrode, a plurality of meander line electrodes formed in a meander line shape are arranged point-symmetrically on each of the upper electrode and the lower electrode, with the center of the upper electrode or the lower electrode being a point of symmetry; one end of the meander-line electrode is electrically connected to an end side of the upper electrode or the lower electrode, and the other end of the meander-line electrode disposed on the center side of the upper electrode or the lower electrode is electrically disconnected from the upper electrode or the lower electrode; The electrical length of the meander line electrode is formed to be an integral multiple of 1 / 4 of the wavelength λ of the RF signal output from the high frequency power supply. High frequency defrosting device.

2. 2. The high-frequency thawing device according to claim 1, Two meander line electrodes are arranged on each of the upper electrode and the lower electrode in point symmetry with respect to the center of the upper electrode or the lower electrode. High frequency defrosting device.

3. 3. The high-frequency thawing device according to claim 1 or 2, Among the plurality of meander-line electrodes arranged on the upper electrode and the lower electrode, an electrical length of a portion of the meander line electrodes is set to a length that is an integral multiple of ¼ of a wavelength λ of the RF signal that resonates with the dielectric constant of the object to be thawed at the start of thawing; The electrical length of the remaining meander line electrodes is set to an integral multiple of 1 / 4 of the wavelength λ of the RF signal that resonates with the dielectric constant of the object to be thawed at the end of thawing. High frequency defrosting device.

4. 4. The high-frequency thawing device according to claim 3, Among the plurality of meander-line electrodes arranged on the upper electrode and the lower electrode, The electrical length of the meander line electrode other than the part and the other part is set to a length between a length that is an integral multiple of 1 / 4 of the wavelength λ of the RF signal that resonates with the dielectric constant of the object to be thawed at the start of thawing and a length that is an integral multiple of 1 / 4 of the wavelength λ of the RF signal that resonates with the dielectric constant of the object to be thawed at the end of thawing. High frequency defrosting device.

5. 4. The high-frequency thawing device according to claim 3, The other end of the meander-line electrode is formed in a spiral shape with the symmetrical point as the center. High frequency defrosting device.

6. 6. The high-frequency thawing device according to claim 5, The electrical length of the meander line electrode is adjusted by changing the line length of the spiral portion formed on the other end. High frequency defrosting device.

7. 6. The high-frequency thawing device according to claim 5, a metal plate disposed between the meander-line electrode disposed on the upper electrode and a position where the object to be thawed is placed, and between the meander-line electrode disposed on the lower electrode and a position where the object to be thawed is placed, The metal plate has at least one of an outer peripheral portion that covers the vicinity of the outer periphery of the spiral portion formed on the other end side of the meander-line electrode and a central portion that covers the central portion of the spiral portion. High frequency defrosting device.

8. 8. The high-frequency thawing device according to claim 7, A notch is formed in the outer periphery of the metal plate. High frequency defrosting device.

9. A high-frequency thawing method using a high-frequency thawing device that thaws an object to be thawed by dielectric heating, comprising: a step of outputting a high-frequency RF signal to a flat upper electrode and a lower electrode that are arranged in parallel at positions that sandwich from above and below a position where the object to be thawed is placed; a plurality of meander line electrodes formed in a meander line shape are arranged point-symmetrically on each of the upper electrode and the lower electrode, with the center of the upper electrode or the lower electrode being a point of symmetry; one end of the meander-line electrode is electrically connected to an end side of the upper electrode or the lower electrode, and the other end of the meander-line electrode disposed on the center side of the upper electrode or the lower electrode is electrically disconnected from the upper electrode or the lower electrode; The electrical length of the meander line electrode is formed to be an integral multiple of 1 / 4 of the wavelength λ of the RF signal output from the high frequency power supply. High frequency thawing method.

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