JP2019032963A - High frequency decompression device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high frequency defrosting apparatus capable of appropriately determining the timing of ending defrosting. A high-frequency defrosting device 100 is arranged between an electrode plate (upper electrode 1 and lower electrode 2), a high-frequency power supply 5 that supplies high-frequency power to the electrode plate, and the electrode plate and the high-frequency power supply 5. It includes a matching circuit 6 and a control unit (control circuit 10) that controls the operation of the high-frequency power supply 6. The matching circuit 6 includes a first capacitance variable capacitor (first capacitor 6a) connected in series with the electrode plate and a second capacitance variable capacitor (second capacitor 6b) connected in parallel with the electrode plate. ) And. The control unit stops the operation of the high frequency power supply 5 based on the capacitance change of at least one of the first capacitance variable capacitor and the second capacitance variable capacitor. [Selection diagram] Fig. 2

Description

  The present invention relates to a high-frequency thawing apparatus that performs a thawing process by applying a high-frequency electric field to food or the like.

  In the high-frequency thawing apparatus, a high-frequency high voltage is applied between two electrodes, and dielectric heating is performed with a material to be thawed (a material to be heated) interposed therebetween. Such a high-frequency thawing apparatus includes a detector that can detect the temperature of the object to be heated in order to end the dielectric heating when the object to be heated reaches a desired state. is there.

  For example, Patent Literature 1 discloses a high-frequency thawing device including a radiant heat sensor 6 for detecting a side surface temperature of an object 3 to be thawed. The radiant heat sensor 6 is installed on the side surface of the heating chamber 1.

  Moreover, in FIG. 10, the structure of an example of the high frequency thawing apparatus provided with the radiant heat sensor is shown. The high-frequency thawing device 200 includes a metal heating chamber 209. Inside the heating chamber 209, an upper electrode 201, a lower electrode 202, a top plate 207, a bottom plate 208, a radiant heat sensor 211, and the like are provided. The upper electrode 201 and the lower electrode 202 are disposed so as to be parallel to each other. The bottom plate 208 is disposed on the lower electrode 202 and is in close contact with the lower electrode 202. The top plate 207 is disposed below the upper electrode 201 and is in close contact with the upper electrode 201. An object to be thawed 203 is placed on the bottom plate 208. The radiant heat sensor 211 is disposed on the side surface of the heating chamber 209.

  A high-frequency power source 205, a matching circuit 206, a control circuit 210, and the like are provided outside the heating chamber 209. The high frequency power source 205 and the matching circuit 206 are connected to the upper electrode 201 and the lower electrode 202 by wiring. A high frequency voltage is supplied from the high frequency power source 205 to the upper electrode 201 and the lower electrode 202. As a result, a high-frequency electric field is generated between the upper electrode 201 and the lower electrode 202, the material 203 to be thawed is dielectrically heated, and the material to be thawed 203 is thawed. The control circuit 210 is connected to the high frequency power source 205 and controls on / off of the high frequency power source 205 and the like. The control circuit 210 is also connected to the radiant heat sensor 211. The detection result of the radiant heat sensor 211 is transmitted to the control circuit 210.

  With the above configuration, the radiant heat sensor 211 detects the surface temperature of the object to be thawed 203. When the control circuit 210 determines that the surface temperature has reached a predetermined temperature based on the detection result of the surface temperature transmitted from the radiant heat sensor 211, the control circuit 210 stops the high-frequency power source 205 and ends the heating and thawing process.

JP-A-8-78150

  However, it is necessary to attach a detector to the apparatus in order to determine that thawing of the object to be thawed is completed by detecting the temperature of the object to be thawed with a detector such as a radiant heat sensor. Thereby, there exists a problem that an apparatus enlarges. The detector is placed in an electromagnetic wave environment in the heating chamber. Therefore, it is desired to install a special detector that can withstand the electromagnetic wave environment, and there is a problem that the cost of the apparatus increases. Furthermore, it is difficult to detect the temperature of the entire object to be thawed with a detector, and there is a problem that thawing cannot be completed at an appropriate timing.

  Therefore, an object of the present invention is to provide a high-frequency thawing device that can appropriately determine the timing of ending thawing while suppressing an increase in size of the device.

  A high-frequency thawing device according to one aspect of the present invention includes an electrode plate, a high-frequency power source that supplies high-frequency power to the electrode plate, a matching circuit that is disposed between the electrode plate and the high-frequency power source, and the high-frequency power source. A control unit for controlling the operation of the power supply. The matching circuit includes a first capacitance variable capacitor connected in series to the electrode plate, and a second capacitance variable capacitor connected in parallel to the electrode plate. The control unit stops the operation of the high frequency power supply based on a change in capacitance of at least one of the first capacitance variable capacitor and the second capacitance variable capacitor.

  In the high-frequency decompression device according to one aspect of the present invention described above, the control unit stops the operation of the high-frequency power supply when a capacitance change per hour of the first variable capacitance capacitor becomes a predetermined value or less. May be.

  In the high-frequency thawing device according to one aspect of the present invention, the control unit may detect the minimum of the first variable capacitance capacitor and stop the operation of the high-frequency power source.

  In the high frequency thawing device according to one aspect of the present invention described above, the control unit may stop the operation of the high frequency power supply by detecting a maximum value of the second variable capacitance capacitor.

  In the high-frequency thawing device according to one aspect of the present invention described above, the control unit detects the maximum of the second capacitance variable capacitor, and then the capacitance change per hour of the second capacitance variable capacitor is just before the capacitance. The operation of the high-frequency power supply may be stopped when the change in capacity per unit time is smaller than the change and the capacity change per time becomes a predetermined value or less.

  In the high-frequency thawing device according to one aspect of the present invention, the control unit may include a state setting unit that sets a thawing state of an object to be thawed. And the said control part may determine the timing of the operation | movement completion | finish of the said high frequency power supply according to the thawing | decompression state set in the said state setting part.

  In the high-frequency thawing device according to one aspect of the present invention, the control unit operates the high-frequency power source based on a change in the capacitance of the first capacitance variable capacitor according to the thawing state set by the state setting unit. It may be determined whether to stop the operation of the high-frequency power source based on a change in capacitance of the second capacitance variable capacitor.

  As described above, according to the high-frequency thawing device according to one aspect of the present invention, it is possible to appropriately determine the timing for ending the thawing of the object to be thawed.

It is a schematic diagram which shows the internal structure of the high frequency thawing apparatus concerning 1st Embodiment. It is a figure which shows the circuit structure in the high frequency decompression apparatus shown in FIG. It is a graph which shows the temperature change of the to-be-heated material at the time of performing a thawing | decompression process using the high frequency thawing apparatus concerning 1st Embodiment, and the capacity | capacitance change of a 1st capacitor | condenser. It is a flowchart which shows an example of the flow of the thawing | decompression process performed in the high frequency thawing apparatus concerning 1st Embodiment. It is a graph which shows the temperature change of the to-be-heated material at the time of performing a thawing | decompression process using the high frequency thawing apparatus concerning the modification of 1st Embodiment, and the capacity | capacitance change of a 1st capacitor | condenser. It is a flowchart which shows an example of the flow of the thawing | decompression process performed in the high frequency thawing apparatus concerning the modification of 1st Embodiment. It is a graph which shows the temperature change of the to-be-heated material at the time of performing a thawing | decompression process using the high frequency thawing apparatus concerning 2nd Embodiment, and the capacitance change of a 2nd capacitor | condenser. It is a graph which shows the temperature change of the to-be-heated material at the time of performing a thawing | decompression process using the high frequency thawing apparatus concerning 2nd Embodiment, and the capacitance change of a 2nd capacitor | condenser. It is a flowchart which shows an example of the flow of the thawing | decompression process performed in the high frequency thawing apparatus concerning 2nd Embodiment. It is a schematic diagram which shows an example of a structure of the conventional high frequency thawing apparatus.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

[First Embodiment]
(Schematic configuration of the high-frequency thawing device)
First, a schematic configuration of the high-frequency thawing device 100 according to the present embodiment will be described with reference to FIG. The high-frequency thawing apparatus 100 according to this embodiment applies a high-frequency electric field to an object to be heated (food to be thawed) 3 such as food to perform thawing processing, heat treatment, and the like of the object to be heated. In particular, the high-frequency thawing device 100 of the present embodiment is used to heat the object to be heated 3 in a frozen state and to defrost or heat the object to be heated 3. The high-frequency thawing apparatus 100 includes a heating chamber (thawing chamber) 9. The heating chamber 9 is formed of a metal casing.

  As shown in FIG. 1, the heating chamber 9 includes an upper electrode (electrode plate) 1, a lower electrode (electrode plate) 2, a metal plate (conductive plate-like member) 4, a top plate 7, and a bottom plate. 8 etc. are provided. The upper electrode 1 and the lower electrode 2 constitute an electrode plate of the high-frequency thawing device 100. The upper electrode 1 and the lower electrode 2 are arranged in parallel to each other. In the present embodiment, two electrode plates (that is, the upper electrode 1 and the lower electrode 2) are provided. However, in another aspect of the present invention, at least one electrode plate may be provided. The upper electrode 1, the lower electrode 2, the top plate 7, and the bottom plate 8 are all flat. The bottom plate 8 is disposed on the lower electrode 2 and is in close contact with the lower electrode 2. The top plate 7 is disposed below the upper electrode 1 and is in close contact with the upper electrode 1.

  The upper electrode 1 is connected to the metal plate 4. The upper electrode 1 is supported above the heating chamber 9 by the metal plate 4. Further, the metal plate 4 is connected to the voltage application unit 20 (more specifically, the matching circuit 6).

  The bottom plate 8 is fixed to the side wall of the heating chamber 9. The lower electrode 2 is bonded and fixed to the lower surface of the bottom plate 8. Thus, in this embodiment, the positions of the bottom plate 8 and the lower electrode 2 are fixed in the heating chamber 9. The lower electrode 2 is connected to the voltage application unit 20 (more specifically, the matching circuit 6) via a wiring.

  When the object 3 to be heated is thawed or heated using the high frequency thawing apparatus 100, the object to be heated 3 is placed on the bottom plate 8. Then, a high-frequency electric field is applied between the upper electrode 1 and the lower electrode 2 to perform dielectric heating thawing due to dielectric loss of the object 3 to be heated.

  In the present embodiment, the height of the upper electrode 1 can be changed by expanding and contracting the metal plate 4 connected to the upper electrode 1 in the vertical direction. Therefore, the distance between the upper electrode 1 and the lower electrode 2 can be changed according to the size of the object to be heated 3 placed on the bottom plate 8.

(Configuration of voltage application unit)
Next, the configuration of the voltage application unit 20 that applies a voltage to each electrode in the heating chamber 9 will be described with reference to FIG. FIG. 2 is a circuit diagram showing a circuit configuration between the electrode pair (upper electrode 1 and lower electrode 2) and the voltage application unit 20. As shown in FIG.

  The voltage application unit 20 applies a high frequency voltage between the upper electrode 1 and the lower electrode 2. As shown in FIG. 1, the voltage application unit 20 is disposed outside the heating chamber 9. The voltage application unit 20 includes a high-frequency power source 5, a matching circuit 6, a control circuit (control unit) 10, and the like as main components.

  The high frequency power supply 5 generates high frequency power to be supplied to the upper electrode 1 and the lower electrode 2. That is, in the high frequency power supply 5, a voltage signal having a frequency in a band from HF to VHF is transmitted, and the transmitted voltage signal is amplified to a desired power by an amplifier (not shown). The amplified voltage is transmitted to the matching circuit 6.

  As shown in FIG. 2, the matching circuit 6 includes a first capacitor (first capacitance variable capacitor) 6a, a second capacitor (second capacitance variable capacitor) 6b, a coil 6c, and the like. The first capacitor 6a and the second capacitor 6b can adjust the capacitance.

  As shown in FIG. 2, the first capacitor 6 a and the coil 6 c are connected in series with the upper electrode 1 and the lower electrode 2 (that is, a capacitor composed of the electrodes 1 and 2). Further, the metal plate 4 is connected in series between the first capacitor 6 a and the upper electrode 1 and the lower electrode 2.

  On the other hand, the second capacitor 6 b is connected in parallel with the output of the high frequency power supply 5.

  With the above configuration, the matching circuit 6 cancels the reactance of the capacitor formed by the upper electrode 1 and the lower electrode 2. The matching circuit 6 can match the input impedance to the matching circuit 6 and the output impedance to the amplifier by adjusting the values of the first capacitor 6a and the second capacitor 6b. Thereby, a high frequency electric field can be efficiently applied to the article 3 to be heated.

  In addition, the metal plate 4 functions as an inductor for matching impedance in the circuit of the high-frequency decompression device 100 together with the matching circuit 6. Since the metal plate 4 is provided, the number of inductor components in the matching circuit 6 can be reduced.

  The voltage subjected to impedance matching in the matching circuit 6 is supplied to a capacitor formed by the upper electrode 1 and the lower electrode 2. As a result, a high-frequency electric field is generated between the upper electrode 1 and the lower electrode 2. The heated object 3 placed between the upper electrode 1 and the lower electrode 2 is dielectrically heated.

  The control circuit 10 controls the operation of the high frequency power supply 5. That is, the high frequency power supply 5 starts or stops the supply of high frequency power in accordance with a command from the control circuit 10. For example, the control circuit 10 detects the capacitance change of at least one of the first capacitor 6a and the second capacitor 6b, and stops the operation of the high-frequency power source 5 based on the detection result. The control circuit 10 can also change the frequency of the voltage signal transmitted from the high frequency power supply 5.

  As shown in FIG. 2, the control circuit 10 has a state setting unit 11. For example, the state setting unit 11 sets the thawing state of the object to be heated 3 in accordance with an instruction from the user. The thawing state set here is used to determine the timing at which the supply of high-frequency power from the high-frequency power supply 5 is stopped.

  For example, when the user desires to defrost substantially all of the article 3 to be heated, the user selects the “thaw mode” using an operation panel (not shown) or the like. When the user desires to heat the article to be heated 3 to a state immediately before thawing starts, the “pre-thawing mode” is selected.

  These selection commands are transmitted to the state setting unit 11. The state setting unit 11 sets the thawing state corresponding to the mode selected on the operation panel as the thawing state of the article 3 to be heated. For example, when the user selects the “thawing mode”, a state where substantially all the heated object 3 has been thawed is set as the thawed state.

  When the control circuit 10 determines that the object to be heated 3 has reached the thawing state set by the state setting unit 11, the control circuit 10 stops the operation of the high frequency power supply 5. In the present embodiment, the determination of the thaw state is performed based on the change in capacitance of the first capacitor 6a.

(Control of high frequency power supply by control circuit)
Next, a method for controlling the stop of the operation of the high frequency power supply 5 using the control circuit 10 will be described with reference to FIGS. 3 and 4. Here, the flow of processing when the user selects the “decompression mode” will be described. FIG. 3 is a graph showing a change in the temperature (° C.) of the heated object 3 after the start of applying a high frequency voltage to the heated object 3 and a change over time in the variable capacitance of the first capacitor 6a. FIG. 4 is a flowchart showing the flow of processing performed in the control circuit 10 during the thawing processing of the article 3 to be heated.

  As shown in FIG. 3, when the thawing process of the object to be heated 3 is started, the temperature of the object to be heated 3 in the frozen state gradually increases. Then, when the temperature of the object to be heated 3 reaches about 0 ° C., thawing of the object to be heated 3 is started. In a state where the object to be heated 3 is being thawed, the temperature of the object to be heated 3 is maintained at about 0 ° C.

  On the other hand, the variable capacity of the first capacitor 6a decreases rapidly when the thawing process of the object to be heated 3 is started. Thereafter, when the temperature of the object to be heated 3 reaches about 0 ° C., the rate of capacity reduction of the first capacitor 6a decreases.

  And while defrosting of the to-be-heated material 3 is progressing (while the temperature of the to-be-heated material 3 is maintained at about 0 degreeC), the capacity | capacitance change of the 1st capacitor | condenser 6a turns from increase to decrease. That is, while the thawing of the object to be heated 3 is proceeding, the minimum of the capacitance change of the first capacitor 6a is detected. As shown in FIG. 3, the minimum of the capacitance change of the first capacitor 6a is detected when the defrosting of the article 3 to be heated proceeds more than half (time A in FIG. 3). This means that the first capacitor 6a exhibits a minimum value when substantially all of the object to be heated 3 has been thawed.

  Therefore, when detecting the time point A, the control circuit 10 stops the operation of the high frequency power supply 5 and ends the decompression process. Hereinafter, a specific processing flow will be described with reference to FIG.

  For example, when the object to be heated 3 is placed on the bottom plate 8 and the user presses the thawing start button on the operation panel, the thawing process is started. First, the control circuit 10 turns on the high frequency power supply 5 and starts supplying high frequency power (step S11).

  When the supply of the high frequency power is started, the control circuit 10 acquires the capacitance X1 of the first capacitor 6a (step S12), and then waits for a predetermined time (for example, a time of 1 second to 5 seconds). (Step S13).

  Thereafter, the control circuit 10 acquires the capacitance X2 of the first capacitor 6a after a predetermined time has elapsed (step S14). Then, the control circuit 10 compares the magnitude relationship between the capacitance X1 and the capacitance X2 (step S15). If the electrostatic capacity X2 is equal to or lower than the electrostatic capacity X1 (NO in step S15), the process returns to step S12, and the electrostatic capacity X1 is compared with the electrostatic capacity X2 (ie, from step S12 to step S15). The process up to is repeated.

  After the comparison between the capacitance X1 and the capacitance X2 is repeated, if it is determined that the capacitance X2 exceeds the capacitance X1 (YES in step S15), the minimum value of the first capacitor 6a is determined. Means it existed. Therefore, the control circuit 10 determines that the time point A shown in FIG. 3 has been reached (or has passed the time point A), turns off the high-frequency power supply 5 and stops the supply of high-frequency power (step S16). . Thereby, the thawing | decompression process of the to-be-heated material 3 is complete | finished.

  By performing the process as described above, the thawing process is appropriately terminated at the timing when the article to be heated 3 is in a desired thawing state (for example, a state where substantially all the article to be heated 3 has been thawed). Can do.

  When a mode other than the “thawing mode” is selected, the control circuit 10 can determine the timing for turning off the high-frequency power supply 5 with reference to the graph shown in FIG. For example, when the “pre-thawing mode” is selected, the high frequency power supply 5 can be turned off when the rate of capacity reduction of the first capacitor 6a decreases to a predetermined value or less.

(Modification)
In the following, another processing flow when the user selects the “decompression mode” will be described with reference to FIGS. 5 and 6. The processing described here can be suitably used when it is difficult to detect the minimum of the first capacitor 6a due to the physical properties of the article 3 to be heated.

  FIG. 5 is a graph showing a change in the temperature (° C.) of the article 3 to be heated since the application of the high-frequency voltage to the article 3 to be heated and a change with time in the variable capacitance of the first capacitor 6a. FIG. 6 is a flowchart showing the flow of processing performed in the control circuit 10 during the thawing processing of the article 3 to be heated.

  Unlike the case shown in FIG. 3, depending on the physical properties of the object 3 to be heated, as shown in FIG. 5, the first capacitor 6a does not show a minimum, and the capacitance is slightly increased even after being completely thawed. May continue to decrease. In such a case, the control circuit 10 stops the operation of the high-frequency power source 5 when the amount of decrease in the capacitance of the first capacitor 6a per unit time becomes equal to or less than a predetermined value.

  A specific processing flow will be described below with reference to FIG. First, the control circuit 10 turns on the high frequency power supply 5 and starts supplying high frequency power (step S21).

  When the supply of the high frequency power is started, the control circuit 10 acquires the capacitance X1 of the first capacitor 6a (step S22), and then waits for a predetermined time (for example, a time of 1 second to 5 seconds). (Step S23).

  Thereafter, the control circuit 10 acquires the capacitance X2 of the first capacitor 6a after a predetermined time has elapsed (step S24). Then, the control circuit 10 calculates the difference between the electrostatic capacitance X1 and the electrostatic capacitance X2 (step S25). If the difference between the capacitance X1 and the capacitance X2 is larger than the predetermined value Z (NO in step S25), the process returns to step S22, and the difference between the capacitance X1 and the capacitance X2 is calculated. The calculation process (that is, the process from step S22 to step S25) is repeated.

  After the process from step S22 to step S25 is repeated, if the difference between the capacitance X1 and the capacitance X2 is equal to or smaller than the predetermined value Z (YES in step S25), the static of the first capacitor 6a is It means that the amount of decrease in the electric capacity per unit time has become a predetermined value or less. Therefore, the control circuit 10 determines that the time point B shown in FIG. 5 has been reached, turns off the high-frequency power supply 5 and stops the supply of high-frequency power (step S26). Thereby, the thawing | decompression process of the to-be-heated material 3 is complete | finished.

  By performing the above processing, even when it is difficult to detect the minimum of the first capacitor 6a, the object 3 to be heated is in a desired defrost state (for example, substantially all the object 3 to be heated is defrosted). The thawing process can be properly terminated at the timing when the state is reached.

(Summary)
As described above, the high-frequency thawing device 100 according to this embodiment includes the voltage application unit 20. The voltage application unit 20 includes a high frequency power supply 5, a matching circuit 6, and a control circuit 10. The matching circuit 6 includes a first capacitor 6a connected in series to the upper electrode 1 and the lower electrode 2, and a second capacitor 6b connected in parallel with the output of the high-frequency power source 5. . Further, the control circuit 10 includes a state setting unit 11.

  Then, the control circuit 10 determines the end timing of the operation of the high frequency power supply 5 according to the decompression state set by the state setting unit 11. Thereby, the thawing | decompression process can be ended at the timing when the to-be-heated material 3 was defrosted to the desired state. That is, the thawing process can be terminated at an appropriate timing without detecting the temperature of the article to be heated 3 with a thermal sensor or the like.

  Further, in the high frequency thawing device 100 according to the present embodiment, the control circuit 10 stops the operation of the high frequency power source 5 by detecting the minimum of the first capacitor 6a, for example. According to this configuration, without using a detector such as a heat sensor, the state where thawing should be terminated can be detected electrically and the thawing process can be automatically stopped. Thereby, it can suppress that a to-be-heated material will be in the state of an overheating, and can obtain the to-be-heated material with a good finishing state. In addition, according to the high-frequency thawing device 100 according to the present embodiment, wasteful consumption of power can be suppressed. Thus, according to this embodiment, a high-frequency high-frequency heating device is provided.

[Second Embodiment]
Subsequently, a second embodiment of the present invention will be described. In the first embodiment described above, the thawing state of the article to be heated 3 is determined based on the capacitance change of the first capacitor 6a arranged in series with the upper electrode 1 and the lower electrode 2. On the other hand, in the second embodiment, the defrosted state of the article to be heated 3 is determined based on the capacitance change of the second capacitor 6b disposed in parallel with the upper electrode 1 and the lower electrode 2. The basic configuration of the high-frequency thawing device 101 according to the second embodiment is the same as that of the first embodiment. Therefore, the following description will focus on how to determine the thawing state of the article to be heated 3 based on the change in the capacity of the second capacitor 6b.

  Hereinafter, a method in which the high-frequency decompression apparatus 101 according to the second embodiment controls the stop of the operation of the high-frequency power supply 5 using the control circuit 10 will be described with reference to FIGS. 7 to 9. 7 and 8 are graphs showing changes in the temperature (° C.) of the object to be heated 3 since the start of applying a high-frequency voltage to the object to be heated 3, and changes over time in the variable capacitance of the second capacitor 6b. is there. FIG. 9 is a flowchart showing the flow of processing performed in the control circuit 10 during the thawing processing of the article 3 to be heated. The process shown in FIG. 9 is a process when the user selects the “pre-decompression mode”.

  First, the flow of processing when the user selects the “pre-thawing mode” will be described with reference to FIG.

  As shown in FIG. 7, when the thawing process of the object to be heated 3 is started, the temperature of the object to be heated 3 in the frozen state gradually increases. Then, when the temperature of the object to be heated 3 reaches about 0 ° C., thawing of the object to be heated 3 is started. In a state where the object to be heated 3 is being thawed, the temperature of the object to be heated 3 is maintained at about 0 ° C.

  On the other hand, the variable capacitance of the second capacitor 6b gradually increases when the thawing process of the article to be heated 3 is started. Thereafter, immediately before the temperature of the article 3 to be heated reaches about 0 ° C. (time C in FIG. 7), the capacitance change of the second capacitor 6b turns from increasing to decreasing. That is, the maximum change in the capacitance of the second capacitor 6b is detected at a timing before the object to be heated 3 begins to thaw. And while defrosting of the to-be-heated material 3 is progressing (while the temperature of the to-be-heated material 3 is maintained at about 0 degreeC), the capacity | capacitance of the 2nd capacitor | condenser 6b falls gradually.

  From the above, it can be seen that the second capacitor 6b exhibits a maximum immediately before the thawing of the article 3 to be heated starts. Therefore, the control circuit 10 stops the operation of the high-frequency power source 5 at the time when it is detected that the second capacitor 6b shows the maximum (time C in FIG. 7), and ends the thawing process. Hereinafter, a specific processing flow will be described with reference to FIG.

  For example, when the object to be heated 3 is placed on the bottom plate 8 and the user presses the thawing start button on the operation panel, the thawing process is started. First, the control circuit 10 turns on the high frequency power supply 5 and starts supplying high frequency power (step S31).

  When the supply of the high frequency power is started, the control circuit 10 acquires the electrostatic capacitance Y1 of the second capacitor 6b (step S32), and then waits for a predetermined time (for example, a time of 1 second to 5 seconds). (Step S33).

  Thereafter, the control circuit 10 acquires the capacitance Y2 of the second capacitor 6b after a predetermined time has elapsed (step S34). Then, the control circuit 10 compares the magnitude relationship between the capacitance Y1 and the capacitance Y2 (step S35). If the electrostatic capacity Y2 is greater than or equal to the electrostatic capacity Y1 (NO in step S35), the process returns to step S32, and the electrostatic capacity Y1 and the electrostatic capacity Y2 are compared (that is, from step S32 to step S35). The process up to is repeated.

  If it is determined that the electrostatic capacity Y2 is lower than the electrostatic capacity Y1 after repeating the comparison between the electrostatic capacity Y1 and the electrostatic capacity Y2 (YES in step S35), the minimum of the second capacitor 6b is determined. Means it existed. Therefore, the control circuit 10 determines that the time point C shown in FIG. 7 has been reached (or has passed the time point C), turns off the high-frequency power supply 5 and stops the supply of high-frequency power (step S36). . Thereby, the thawing | decompression process of the to-be-heated material 3 is complete | finished.

  By performing the above-described process, the heat treatment can be appropriately terminated at a timing when the object to be heated 3 is in a desired state (for example, the state in which the object to be heated 3 is heated to just before thawing). it can.

  Next, the flow of processing when the user selects the “decompression mode” will be described with reference to FIG.

  As shown in FIG. 8, when the thawing process of the object to be heated 3 is started, the temperature of the object to be heated 3 in the frozen state gradually increases. Then, when the temperature of the object to be heated 3 reaches about 0 ° C., thawing of the object to be heated 3 is started. In a state where the object to be heated 3 is being thawed, the temperature of the object to be heated 3 is maintained at about 0 ° C. Thereafter, when the object to be heated 3 is almost completely thawed, the temperature of the object to be heated 3 starts to gradually increase from 0 ° C.

  On the other hand, the variable capacitance of the second capacitor 6b gradually increases when the thawing process of the article to be heated 3 is started. Thereafter, immediately before the temperature of the article to be heated 3 reaches about 0 ° C., the capacitance change of the second capacitor 6b turns from increasing to decreasing. And while defrosting of the to-be-heated material 3 is progressing (while the temperature of the to-be-heated material 3 is maintained at about 0 degreeC), the capacity | capacitance of the 2nd capacitor | condenser 6b falls gradually.

  Thereafter, the amount of decrease in the capacity of the second capacitor 6b per unit time gradually decreases, and the capacity of the second capacitor 6b becomes substantially constant. The time when the capacity of the second capacitor 6b becomes substantially constant (time D in FIG. 8) corresponds to the time when the article to be heated 3 is almost completely thawed.

  Therefore, when the time point D is detected, the control circuit 10 stops the operation of the high frequency power supply 5 and ends the decompression process. Thereby, a heat processing can be appropriately complete | finished at the timing when the to-be-heated material 3 was thawed | decompressed almost completely.

  Depending on the physical properties of the object 3 to be heated, the capacitance of the second capacitor 6b may not be constant, and the capacitance may continue to decrease slightly even after being completely thawed. In such a case, it is preferable that the control circuit 10 stops the operation of the high-frequency power supply 5 when the amount of decrease in the capacitance of the second capacitor 6b per unit time becomes a predetermined value or less. Such control can be performed by applying the process shown in the flowchart of FIG.

  As described above, in the high frequency thawing device 101 according to the present embodiment, the control circuit 10 stops the operation of the high frequency power supply 5 based on the change in the capacitance of the second capacitor 6b. For example, when the “pre-thawing mode” is selected in the state setting unit 11 (that is, when the user desires to heat the article to be heated 3 to a state just before the start of thawing), the control circuit 10 Then, the maximum of the second capacitor 6b is detected and the operation of the high frequency power supply 5 is stopped. On the other hand, when “thawing mode” is selected in the state setting unit 11 (that is, when the user desires to defrost substantially all of the article to be heated 3), the control circuit 10 performs the second operation. After detecting the maximum of the capacitor 6b, the capacitance change (absolute value) per second of the second capacitor 6b is smaller than the previous capacitance change (absolute value thereof), and the second capacitor 6b per hour When the capacitance change (the absolute value thereof) becomes a predetermined value or less, the operation of the high-frequency power supply 5 is stopped.

  According to this configuration, without using a detector such as a heat sensor, the state where thawing should be terminated can be detected electrically and the thawing process can be automatically stopped. The method of the thawing process described in the second embodiment is preferably selected when “pre-thawing mode” or “thawing mode” is selected.

[Third Embodiment]
Subsequently, a third embodiment of the present invention will be described. In the first and second embodiments described above, the thawing state of the article to be heated 3 is determined based on the capacitance change of one of the first capacitor 6a and the second capacitor 6b. However, in one embodiment of the present invention, the defrosted state of the object to be heated 3 can also be determined based on the capacitance changes of both the first capacitor 6a and the second capacitor 6b. Therefore, in the following, a method for determining the defrosted state of the article to be heated 3 based on the capacitance changes of the first capacitor 6a and the second capacitor 6b will be described.

  As the basic configuration of the high-frequency thawing device according to the present embodiment, the configuration of the high-frequency thawing device 100 or 101 described above can be applied. Therefore, a specific description is omitted.

  Similar to the first embodiment, the voltage application unit 20 provided in the high-frequency decompression apparatus 101 includes a high-frequency power source 5, a matching circuit 6, a control circuit (control unit) 10, and the like (FIGS. 1 and 1). 2). The control circuit 10 has a state setting unit 11.

  For example, the state setting unit 11 sets the thawing state of the object to be heated 3 in accordance with an instruction from the user. As described in the first embodiment, the thawing state of the article 3 to be heated includes, for example, two thawing states of “defrosting mode” and “pre-thawing mode”. However, the mode representing the decompressed state is not necessarily limited to this.

  In addition, when “decompression mode” is selected from the above three decompression states, the timing of stopping the operation of the high-frequency power supply 5 based on the capacitance change of the first capacitor 6a or the second capacitor 6b. It is determined. More specifically, the control circuit 10 determines the time point B shown in FIG. 5 or the time point D shown in FIG. 8, and stops the operation of the high-frequency power source 5 at these time points.

  Further, when the “pre-thawing mode” is selected from the above three thawing states, the timing for stopping the operation of the high-frequency power source 5 is determined based on the change in the capacitance of the second capacitor 6b. More specifically, the control circuit 10 determines the time point C shown in FIG. 7 and stops the operation of the high-frequency power source 5 at the time point C.

  As described above, in the high-frequency decompression device according to the third embodiment, the control circuit 10 detects the capacitance change of the first capacitor 6a according to the decompression state set in the state setting unit 11, or the first It is possible to determine whether to detect the capacitance change of 6b of the second capacitor.

  When it is desired to end the thawing process in a state where the heated object 3 is almost completely thawed, the thawing process is performed based on the detection result of the capacitance change of the first capacitor 6a or the second capacitor 6b. Can be terminated. In addition, when it is desired to end the heating process immediately before the object to be heated 3 starts thawing, the thawing process can be ended based on the detection result of the capacitance change of the second capacitor 6b. .

  Therefore, according to the high frequency thawing apparatus according to the third embodiment, the thawing process can be terminated at a more appropriate timing according to each selected thawing state. Therefore, if the to-be-heated material is thawed using the high-frequency thawing device according to the third embodiment, it can be brought closer to the thawing state desired by the user.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims. Further, configurations obtained by combining the configurations of the different embodiments described in this specification with each other are also included in the scope of the present invention.

1: Upper electrode 2: Lower electrode 3: Heated object 4: Metal plate 5: High frequency power supply 6: Matching circuit 6a: First capacitor (first capacitance variable capacitor)
6b: second capacitor (second variable capacitance capacitor)
9: Heating room (thawing room)
10: Control circuit (control unit)
11: State setting unit 20: Voltage application unit 100: High-frequency thawing device 101: High-frequency thawing device

Claims (7)

An electrode plate;
A high frequency power source for supplying high frequency power to the electrode plate;
A matching circuit disposed between the electrode plate and the high-frequency power source;
A control unit for controlling the operation of the high-frequency power source,
The matching circuit includes a first capacitance variable capacitor connected in series to the electrode plate, and a second capacitance variable capacitor connected in parallel with the high-frequency power source,
The controller stops the operation of the high-frequency power source based on a change in capacitance of at least one of the first capacitance variable capacitor and the second capacitance variable capacitor;
High-frequency thawing device.   The high frequency thawing device according to claim 1, wherein the control unit stops the operation of the high frequency power supply when a capacitance change per hour of the first variable capacitance capacitor becomes a predetermined value or less.   The high frequency thawing device according to claim 1, wherein the control unit detects the minimum of the first capacitance variable capacitor and stops the operation of the high frequency power supply.   4. The high frequency thawing device according to claim 1, wherein the control unit detects the maximum of the second variable capacitance capacitor and stops the operation of the high frequency power supply. 5.   The control unit detects a maximum of the second variable capacitance capacitor, and then the capacitance change per hour of the second variable capacitance capacitor is smaller than the previous capacitance change, and the capacitance change per time 5. The high frequency thawing device according to claim 1, wherein when the frequency becomes equal to or less than a predetermined value, the operation of the high frequency power supply is stopped. The controller is
It has a state setting part that sets the thawing state of the object to be thawed,
6. The high frequency thawing device according to claim 1, wherein an operation end timing of the high frequency power supply is determined according to a thawing state set by the state setting unit. The controller is
According to the decompression state set in the state setting unit,
And determining whether to stop the operation of the high-frequency power source based on a change in capacitance of the first variable capacitance capacitor or to stop the operation of the high-frequency power source based on a change in capacitance of the second variable capacitance capacitor. Item 7. The high-frequency thawing device according to item 6.

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